Visuospatial Influences on Emotional Perception: Effects of Spatial Location on Ratings of Emotional Valence

VISUOSPATIAL INFLUENCES ON EMOTIONAL PERCEPTION: EFFECTS OF SPATIAL LOCATION ON RATINGS OF EMOTIONAL VALENCE

DANA MARIE SZELES

A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA

2015

To my parents, Rose and Rick Szeles

ACKNOWLEDGMENTS

First, I want to thank my dissertation chair and mentor, Dr. Tim Conway for his wise leadership, dedicated support, and constant direction throughout my graduate career – both in research and in my development as a professional, clinical neuropsychologist. Likewise, I want to thank my research advisor, Dr. Kenneth Heilman for his guidance during the development of this project, compassionate life advice, and unfailing faith in my scientific endeavors and career pursuits.

I am thankful to Dr. Michael Robinson, whose statistical knowledge helped strengthen and validate the methodological approaches applied herein. I want to thank

Liliana Salazar, Scott Norberg, and Damon Lamb – members of Dr. Heilman’s Center for Neuropsychological Studies – for directly assisting in recruitment and administration of the Vertical Neglect project that supported data collection for this study as well as the

Department of Veteran’s Affairs for funding this important investigation. I am grateful to the entire lab for their insight throughout the evolution of my dissertation and their suggestions regarding both my study design and analyses. Most notably within the lab, I would like to recognize Dr. Kenneth Heilman, Dr. John Williamson, Dr. Adam Falchook,

Dr. Keith White, Dr. Ira Fischler, Dr. Leah Acosta, Dr. Joanne Byars, Dr. Eduardo Zilli,

Dr. Brandon Burtis, Liliana Salazar, Scott Norberg, and Dr. Damon Lamb. Last but certainly not least, I am grateful to Dr. Nicholas Milano and Dr. Susan Leon in the

Center for Neuropsychological Studies for their role model mentorship, irreplaceable friendship, and constant faith in my capacity for success.

I thank my countless family and friends for always anticipating that my hard work and desire would yield accomplishment, and for helping me celebrate each graduate school milestone with more anticipation and enthusiasm than surprise. 4

Finally, I would like to thank the distinguished members of my dissertation committee, Dr. Tim Conway, Dr. Russell Bauer, Dr. Kenneth Heilman, Dr. Patricia

Durning, and Dr. Lisa Edmonds, who have committed their valuable time and efforts to reviewing and determining the scientific rigor of this project. Their insight has undeniably enhanced both this project, and my growth as a scientific researcher during my time at the University of Florida. I am grateful to have benefited from each of their unique perspectives during my graduate studies, and delight in knowing I will not be the last student who will.

TABLE OF CONTENTS

page

ACKNOWLEDGMENTS ...... 4

LIST OF TABLES ...... 9

LIST OF FIGURES ...... 10

LIST OF ABBREVIATIONS ...... 12

ABSTRACT ...... 13

CHAPTER

1 INTRODUCTION ...... 15

Vertical (Upper and Lower) Emotion ...... 15 Horizontal (Left and Right) Emotion ...... 17

2 REVIEW OF THE LITERATURE ...... 21

Neurological Underpinnings ...... 21 Influence of Spatial Attention on Emotion ...... 24 Influence of Emotion on Spatial Attention ...... 26 Influence of Emotion on Action-Intention ...... 29 Emotion and Physiology ...... 32

3 STUDY AIMS AND HYPOTHESES-PREDICTIONS ...... 37

Purpose of the Study ...... 37 Specific Aim #1: Influence of Spatial Attention on the Perception of Emotions ...... 43 Upper and Lower Space ...... 43 Hypothesis-1 ...... 43 Prediction-1 ...... 43 Alternative prediction-1 ...... 45 Right and Left Space ...... 46 Hypothesis-2 ...... 46 Prediction-2 ...... 47 Alternative prediction-2 ...... 48 Specific Aim #2: Influence of Emotion Processing on Attention or Intentional Spatial Biases ...... 48 Ventral versus Dorsal Stream Engagement ...... 48 Hypothesis-3 ...... 50 Prediction-3 ...... 50 Alternative prediction-3 ...... 52

Right versus Left Hemisphere Engagement ...... 53 Hypothesis-4 ...... 53 Prediction-4 ...... 54 Alternative prediction-4 ...... 55 Specific Aim #3: Influence of Emotion Processing on Physiological Responding ... 57 Upper versus Lower Space ...... 57 Hypothesis-5 ...... 57 Prediction-5 ...... 57 Alternative prediction-5 ...... 57 Right versus Left Space ...... 58 Hypothesis-6 ...... 58 Prediction-6 ...... 58 Alternative prediction-6 ...... 58

4 METHODS ...... 60

Research Design ...... 60 Apparatus ...... 60 Emotional Picture Stimuli...... 62 Equating for valence and arousal across Upper-Lower and Right-Left conditions...... 65 Equating for valence and arousal across spatial assignment, within conditions...... 66 Valence Lines ...... 68 Participants ...... 70 Inclusion and Exclusion Criteria ...... 70 Screening Measures ...... 71 Benton Handedness Questionnaire ...... 71 Beck Depression Inventory, second edition (BDI-II) ...... 72 Demographics across Counterbalanced, Between-Subjects Factors ...... 72 Experimental Paradigm ...... 73 Instructions ...... 73 Computer Presentation ...... 75 Pilot Electrophysiology ...... 78 Preparation and Electrode Placement ...... 79 Startle Eye-Blink Measurement ...... 80 Statistical Analyses/Evaluation ...... 81 Repeated Measures Analysis of Variance (ANOVA) ...... 81 Paired Samples t-tests ...... 83 Post-test Debriefing ...... 83

5 RESULTS ...... 85

Post-test Debriefing Form ...... 85 Dataset Corrections: Effect of Probe Administration ...... 85 Differences Between Upper-Lower and Right-Left Conditions ...... 88

Analyses for Specific Aim 1: Influence of Spatial Attention on the Perception of Emotions ...... 90 Upper-Lower Condition ...... 90 Effect of valence category ...... 90 Effect of spatial location ...... 91 Interaction effect (valence x space) ...... 94 Summary...... 95 Right-Left Condition ...... 95 Effect of valence category ...... 95 Effect of spatial location ...... 96 Interaction effect (valence x space) ...... 99 Summary...... 99 Analyses for Specific Aim 2: Influence of Emotion on Attention or Intention ...... 100 Upper-Lower Condition ...... 100 Right-Left Condition ...... 102 Summary ...... 105 Analyses for Specific Aim 3: Influence of Emotion on Physiological Responding . 106

6 DISCUSSION ...... 107

Specific Aim 1: Influence of Spatial Attention on the Perception of Emotions ...... 107 Specific Aim 2: Influence of Spatial Attention on Action-Intention ...... 112

7 CONCLUSIONS ...... 118

Summary ...... 118 Study Limitations ...... 118 Implications for Future Research ...... 120 Conclusions ...... 121

APPENDIX

A TELEPHONE SCREENING ...... 122

B OVERVIEW OF COUNTERBALANCED FACTORS ACROSS STIMULI ...... 128

C POST-TEST DEBRIEFING FORM ...... 131

D ERRORS DURING PROBE ADMINISTRATION ...... 132

LIST OF REFERENCES ...... 134

BIOGRAPHICAL SKETCH ...... 143

LIST OF TABLES

Table page

3-1 Overview of specific aims, hypotheses, and predictions for Upper-Lower and Right-Left conditions...... 41

3-2 Overview of alternative hypotheses, predictions, outcomes, and conclusions for Upper-Lower and Right-Left conditions ...... 43

5-1 Means and standard deviations of average emotional ratings for negative, neutral, and positive pictures presented in lower, middle, and upper space in the Upper—Lower condition...... 89

5-2 Means and standard deviations of average emotional ratings for negative, neutral, and positive pictures presented in left, middle, and right space in the Right—Left condition...... 89

5-3 Means and standard deviations of average emotional ratings for negative, neutral, and positive pictures presented in lower, middle, and upper space in the Upper—Lower condition...... 90

5-4 Means and standard deviations of average emotional ratings for negative, neutral, and positive pictures presented in left, middle, and right space in the Right—Left condition...... 90

D-1 Number and type of errors committed during probe administration for critical trials during each experimental condition ...... 134

LIST OF FIGURES

Figure page

3-1 Depiction of predicted outcome for Specific Aim #1 in the Upper-Lower condition ...... 44

3-2 Depiction of the alternative predicted outcome for Specific Aim #1 in the Upper-Lower condition ...... 46

3-3 Depiction of predicted outcome for Specific Aim #1 in the Right-Left condition .. 47

3-4 Depiction of the alternative predicted outcome for Specific Aim #1 in the Right-Left condition ...... 48

3-5 Figure illustration of horizontal valence lines shown following critical pictures in the Upper-Lower condition ...... 49

3-6 Illustration of vertical valence lines shown following critical pictures in the Right-Left condition ...... 50

3-7 Depiction of predicted outcome for Specific Aim #2 in the Upper-Lower condition ...... 51

3-8 Depiction of the alternative predicted outcome for Specific Aim #2 in the Upper-Lower condition ...... 53

3-9 Depiction of predicted outcome for Specific Aim #2 in the Right-Left condition .. 55

3-10 Depiction of the alternative predicted outcome for Specific Aim #2 in the Right-Left condition ...... 56

4-1 Illustration of computer setup...... 61

4-2 Illustration of five possible positions for presentation of emotional pictures and relative spacing across display positions ...... 63

4-3 Illustration of presentation order and timing of stimuli and response periods during computer paradigm ...... 77

4-4 Illustration of electrode placement during startle eye-blink acquisition ...... 80

5-1 Emotional ratings for positive, neutral, and negative pictures evaluated when presented in Lower, Middle, and Upper Space in the Upper-Lower condition .... 92

5-2 Emotional ratings for positive, neutral, and negative pictures evaluated when presented in Left, Middle, and Right Space in the Right-Left condition ...... 97

5-3 Emotional ratings for positive, neutral, and negative pictures evaluated with the “positive” label positioned on the right side of the horizontal valence line, and with the “positive” label on the left side of the line in the Upper-Lower condition ...... 102

5-4 Emotional ratings for positive, neutral, and negative pictures evaluated with the “positive” label positioned at the top of the vertical valence line, and with the “positive” label at the bottom of the line in the Right-Left condition ...... 104

B-1 Number of stimuli in each counterbalanced category ...... 129

B-2 Example division of critical images across the three primary positions of interest in each condition...... 130

D-1 Stimulus characteristics of items probed incorrectly during each experimental condition and withdrawn from analysis ...... 133

LIST OF ABBREVIATIONS

ANOVA Analysis of Variance

ANS Autonomic Nervous System

BDI Beck Depression Inventory

BDI-II Beck Depression Inventory, Second Edition

DSM-IV Diagnostic and Statistical Manual of Mental Disorders, 4th Edition

IAPS International Affective Pictures System ms Milisecond

Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy

VISUOSPATIAL INFLUENCES ON EMOTIONAL PERCEPTION: EFFECTS OF SPATIAL LOCATION ON RATINGS OF EMOTIONAL VALENCE

Dana Marie Szeles

December 2015

Chair: Tim W. Conway Cochair: Russell M. Bauer Major: Psychology

Emotional concepts are often conceptualized along a vertical plane, such that positive things are conceptualized as being “up” in space whereas negative things are conceptualized as being “down.” While this has been supported by sociological and anthropological research, a neurobiological basis for this dichotomy has not yet been proposed. It is possible for instance, that the ventral stream, which attends to upper space, may assign greater positive value to emotional stimuli whereas the dorsal stream, which attends to lower space may assign greater negative value. The purpose of this study was to examine how directing attention toward specific parts of space might influence the perception of emotion. A secondary aim was to explore how both spatial orienting and emotional processing might contribute to spatial action-intention biases. These aims were explored in both the vertical dimension (upper, middle, and lower space) as well as the horizontal dimension (left, middle, and right space).

This study revealed that pictures in lower space were rated as more positive than pictures presented in middle space, while negative pictures alone were rated more positively in both lower and upper space. Along the horizontal dimension, pictures were

rated more negatively when presented in right relative to middle space for all pictures and when negative pictures alone were examined. A consistent upward spatial bias was seen along a vertical line for rating emotional valence, suggesting either spatial biases or dominance of the ventral stream for emotional processing. An interaction was initially observed (though lost with statistical correction) along the horizontal dimension, such that positive and negative pictures were rated more intensely when the positive label appeared at the left end of the line, consistent with valence theory.

While several factors limit conclusive findings, it appears that spatial orienting may influence the perceived valence of emotional stimuli; likewise, this may occur in different ways along the vertical versus horizontal planes. Additionally, it appears that action-intention biases along the horizontal plane may interact with valence due to hemispheric asymmetries for emotional processing whereas the ventral stream might facilitate upward biases, independent of emotion.

CHAPTER 1 INTRODUCTION

Vertical (Upper and Lower) Emotion

People often represent positive and negative concepts through spatial metaphor along a vertical dimension, such that things that are “up” in position are generally considered “good” while things that are “down” in position are generally considered

“bad.” That is, individuals tend to categorize positive stimuli more quickly when they are presented higher in vertical space and categorize negative stimuli more quickly when they are presented lower in vertical space. Similarly, individuals tend to more frequently recall positive stimuli as being presented higher in vertical space and more frequently recall negative stimuli as being presented lower in vertical space. This has been explored by comparing visual depictions of God versus the Devil (Meier, Hauser,

Robinson, Friesen, & Schjeldahl, 2007), words conveying moral versus immoral concepts and behaviors (e.g., “trustworthy” versus “adultery”; Meier, Sellborn, and

Wygant, 2007), words conveying “good” versus “bad” personality/behavioral traits (e.g.

“hero” versus “liar”; Meier & Robinson, 2004), and pleasant versus unpleasant emotional pictures (Crawford, Ochsner, Drake, & Murphy, 2005). Likewise, in a series of experiments by Meier and Robinson (2004), responses to non-emotional stimuli in upper and lower positions (determining whether a presented letter was a ‘p’ or a ‘q’) were also facilitated after participants first evaluated either positive or negative words, respectively, in center space.

Even in the absence of explicit task demands (e.g., when asked to simply place emotional labeled pegs – e.g.s, happy, sad, angry – in whatever location desired on an axially aligned board), individuals place positive feeling words (happy, joyful, surprised)

in distal positions (toward the top of the workspace) while individuals place negative feeling words (afraid, sad, disgusted) closer to proximal space (toward the bottom of the workspace; Foster, Drago, Webster, Harrison, Crucian, & Heilman 2008). In addition, different emotional experiences can influence the spatial allocation of attention such that positive emotional experiences induce a distal (in the axial plane) or upward (in the vertical plane) bias and sad experiences induce a proximal or downward bias (Wapner,

Werner, & Krus, 1957). Based on these results, revealing that positive versus negative emotion words, concepts, and pictures induce vertical shifts of attention and/or action- intention, it should be no wonder that we also describe the emotional experience along a vertical dimension. Hence, we say we feel “down” when we are sad, and when things are improving we state things are “looking up” and feel elated. It is unclear if this up- down positive-negative dichotomy is due to nurture (learned experiences) or nature

(neurobiology). That is, might this common finding be due to one’s culture and environment or an underlying organizational system within the brain?

In his seminal sociological review of good versus bad representations in vertical space, Schwartz (1981) emphasized the role of early parent-child relationships in perpetuating higher equals “good” and lower equals “bad” social and moral disparities in later adulthood. Tolaas (1991) similarly highlighted that resources gleaned during infancy are often obtained at points which are “up” in space (e.g., food and nourishment from parents) and this association between “up” and “good” might persist through later stages in life. As proposed by Piaget and Inhelder (1969), it is likely that such early sensory-motor experiences provide the early basis for an understanding of the world and ability to approach what is good and supportive while avoiding what is bad and

harmful. Throughout development, these early sensory representations (up-down spatial representations) may evolve into a more complex understanding of abstract emotional concepts, such as love and hate. While some cross-cultural evidence has been demonstrated through anthropological and developmental studies (e.g.s,

Schwartz, 1981; Tolaas, 1991; Piaget & Inhelder, 1969), a neurological account for this relationship has not yet been proposed. The present study aims to link what is known about how the brain attends to space with what has been observed regarding the vertical representation of emotion. By manipulating the spatial location of emotional stimuli and determining its effect on emotional perception, this study may begin to support a neurological basis for these behavioral observations.

Horizontal (Left and Right) Emotion

To date, much of the neuropsychological literature has examined emotional processing with respect to hemispheric asymmetry between the right and left hemispheres. Within this left- versus right-brain approach, two major theories exist to explain preferential emotional processing in the brain. The dominance theory posits that the right hemisphere is specialized for processing emotional relative to non-emotional stimuli in the environment (Heilman, Watson, & Valenstein, 2003). The valence theory, in contrast, posits that the right hemisphere is specialized for processing negative stimuli while the left hemisphere is specialized for processing positive stimuli (Borod,

Cicero, Obler, Welkowitz, Erhan, Santschi, Grunwald, Agosti, & Whalen, 1998;

Silberman & Weingartner, 1986).

A great deal of support for each of these theories is drawn from patients with left versus right hemisphere damage as well as functional neuroimaging in neurologically healthy controls. The dominance hypothesis, for instance, has been largely supported 17

by observations of patients with right hemisphere damage, who demonstrate greater difficulty discriminating emotions of facial expressions than patients with left hemisphere damage and normal controls (DeKosky, Heilman, Bowers, & Valenstein, 1980; Bowers,

Bauer, Coslett, & Heilman, 1985). Likewise, neuroimaging has revealed heightened right hemisphere activation relative to left in response to both positive and negative stimuli (Ishai, Schmidt, & Boesiger 2005). In contrast, the valence theory has gained support from patients with right hemisphere damage, who often demonstrate jocularity and sometimes inappropriate laughter and positive mood states while patients with left hemisphere damage more frequently experience depression (e.g., Starkstein,

Robinson, & Price, 1987). These data provide support for the possible role of the left hemisphere in mediating positive mood states versus the right hemisphere, which may be more involved in negative emotion processing. Discrepant findings appear to suggest a potential difference in specialization for emotional perception versus experience with dominance for the right hemisphere in perceiving/discriminating emotions versus hemispheric specialization for processing the experience of negative

(right) versus positive (left) mood states.

Tachistoscopic research has provided an additional means of non-invasively probing the roles of the right versus left hemisphere in emotional processing.

Tachistoscopic studies involve presentation of stimuli to one hemifield at a time, and determining whether an advantage in either speed or accuracy of responding exists in one hemifield versus the other. Each hemisphere processes information in the contralateral hemifield (Kinsbourne, 1970). Thus, delayed or less accurate responding when stimuli are presented in a certain space (e.g., in right space) would implicate

reduced specialization of the contralateral (e.g., left) hemisphere or increased time to communicate with the specialized ipsilateral (right) hemisphere in selecting a response.

Likewise, an advantage in speed or accuracy when stimuli are presented in one hemifield over the other (e.g., in left space) would implicate the dominance of the contralateral (right) hemisphere for processing that type of information.

Tachistoscopic research has likewise provided evidence for both the dominance theory and valence theory in emotional processing. For instance, when participants were shown line drawings of emotional faces and asked to determine if two faces were expressing the same or different emotions, a benefit in left visual field was found (Ley &

Bryden, 1979). This study revealed that regardless of the specific emotion presented, the right hemisphere was dominant for processing facial expressions. Conversely, tachistoscopic studies have similarly shown support for the valence theory. In a series of investigations examining speed of recognition for positive (happy) and negative (sad) faces presented in the right versus left visual hemifield, (Reuter-Lorenz, Givis, &

Moscovitch, 1983; Reuter-Lorenz and Davidson, 1981), faces were more quickly recognized as positive when they appeared in the right hemifield (which is processed by the left hemisphere) and as negative when they appeared in the left hemifield (which is processed by the right hemisphere). Similarly, it has been shown that emotional pictures are rated as more negative when presented to the left hemifield (and processed by the contralateral right hemisphere) and as more positive when presented to the right hemifield (and processed by the left hemisphere; Drake, 1987; Merckelbach & Van

Oppen, 1989). These studies therefore showed an interaction, with preferential processing of negative stimuli by the right hemisphere and preferential processing of

positive stimuli by the left hemisphere. Together, the possibility exists that the right hemisphere may be largely dominant for emotional processing, while this effect might be strongest for negative stimuli in particular. Alternatively, as posited by Ley and

Strauss (1986), the right hemisphere may be best suited for making perceptual decisions regarding valence, as judged in reaction time experiments (e.g., Ley &

Bryden, 1979) whereas, specialization across the hemispheres may reflect differential processing when an emotional experience is invoked or stimuli are judged against each other for relative emotional value (e.g., Reuter-Lorenz, et al., 1983; Reuter-Lorenz &

Davidson, 1981).

Motivated by both the dominance and valence theories of the right versus left hemispheres, this study aimed to elucidate whether the dorsal and ventral visual processing streams would demonstrate a similar dichotomous relationship. This study therefore sought to explore two parallel postulates regarding the influence of spatial attention toward upper and lower space on emotional processing: 1) that the ventral visual stream preferentially processes positive stimuli/upper space while the dorsal stream preferentially processes negative stimuli/lower space; and 2) that the ventral visual stream may be dominant for emotional processing (due to extensive connections with the amygdala and projections along the emotion circuit, as discussed further herein). Methods for assessing preferential processing within the dorsal versus ventral visual streams are detailed herein.

CHAPTER 2 REVIEW OF THE LITERATURE

Neurological Underpinnings

The parietal lobe exhibits greater representation of the lower compared to the upper visual field, which appears supported by stronger connections between the primary visual cortex and parietal-occipital regions; in contrast, the ventral visual processing stream contains a larger representation of the upper visual field, supported by connections between the primary visual cortex and temporal lobes (Previc, 1990).

Therefore, at the most basic level, the dorsal and ventral visual processing streams have been shown to allocate visual spatial attention for stimuli presented in lower and upper space, respectively.

These assertions are supported further by evidence from patients with brain injury, who have experienced bilateral damage to the dorsal and ventral processing streams. Altitudinal neglect for example, defined by neglect of lower portions of space, has been reported following a patient with biparietal-occipital (dorsal) lesions (Verfaellie,

Rapcsak, & Heilman, 1990; Rapcsak, Cimino, & Heilman, 1988) whereas neglect of upper portions of space has been observed in a patient with bilateral temporo-occipital

(ventral) lesions (Shelton, Bowers, & Heilman, 1990). These data provide further support for the roles these processing streams might play in attending to parts of lower versus upper space in healthy adults, and the impairments that might result with destruction.

Aside from attending predominantly to lower space and upper space, the dorsal and ventral stream also contribute to different aspects of spatial processing. For instance, the dorsal stream is specialized for identifying “where” spatial information is (in

relation to the self) and appears to be important in programming the complex motor programs for fine motor interaction with environmental stimuli, such as that needed for complex tool use (Balint, 1909). Likewise, the dorsal stream is also responsible for calculating approximate distances of objects for target approximation during reaching and grasping movements (Goodale, Westwood, & Milner, 2004; Milner & Goodale,

1995). Conversely, the ventral stream is considered the “what” processing stream and is specialized for processing object-specific spatial information, including features needed for color, face, and object recognition (Lissauer, 1890; Mishkin & Ungerleider, 1982). In effect, the dorsal stream guides “egocentric” – or person-centered – processing whereas the ventral stream guides “allocentric” – or other-centered – aspects of attention (Hillis, Newhart, Heidler, Barker, & Herskovits, 2005). In review, the dorsal stream processes information in lower space and mediates attention to body-centered spatial information while the ventral stream processes information in upper space and mediates attention to environment-centered spatial information. In terms of emotion, when we feel “down” we may tend to focus on the personal relevance of external stimuli. In contrast, when we feel happy we may tend to concentrate more on things beyond ourselves – focusing more on interactions with others and societal integration

(Drago, Heilman, & Foster, 2010). This does not imply that mood states cannot exist in the absence of visuospatial information or that they depend on visuospatial means to experience and communicate these states. However, it may suggest an alternate role for the ventral and dorsal processing streams beyond what is necessary for processing visual stimuli. Specifically, these streams may also influence how emotional experiences (whether internally or externally driven) are interpreted, even in the

absence of primary visual information, and how they may direct subsequent attention either toward or away from further engagement.

Anecdotal evidence regarding the emotional and behavioral consequences of biparietal and bitemporal lesions provides some insight into the roles the dorsal and ventral stream might play in emotional processing. In patients with Balint’s syndrome, for instance – a disorder caused by bilateral parieto-occipital damage – alterations of mood have been described:

At first he was inclined to brood over his afflictions but later he became placid, good-humoured and most ready to co-operate, this mood persisting for many months without appreciable fluctuation. Failures in performance never gave rise to catastrophic reactions and he had good insight into his state (Allison, Hurwitz, White, & Wilmot, 1969).

Of course, such placidity would never be highlighted in research and may not mark a stark change from previous functioning. In contrast, data regarding emotional functioning in individuals with bilateral temporal lobe lesions have been far more striking, leaning toward more negative mood states. These include reports of heightened aggressive states in felines (Bard & Mountcastle, 1948), apathetic withdrawal in monkeys (Kluver and Bucy, 1939), and agitation and delirium accompanying visual disturbances in humans (Medina, Chokroverty, & Rubino, 1977).

These reports suggest that disruption within the ventrolateral (frontotemporal) limbic system – with projections along the ventral visual processing stream – might disrupt integral connections that are normally responsible for mediating emotions and behavior

(MacLean, 1952). Thus, beyond the potential role of the ventral stream in mediating more positive, stable mood states, these findings reveal the potential dominance of ventral networks in mediating emotions in general.

Anecdotal evidence from bilateral lesions in humans is certainly rare, limiting implications of the role of dorsal and ventral processing streams in healthy emotional processing. However, it is also likely that the emotional consequences of biparietal and bitemporal lobe injuries have largely been overshadowed in the past by their more debilitating effects – prominent disturbances in visual perception, language, and attention.

Since it appears that the dorsal stream may be more involved in mediating negative experiences and the ventral stream may be more important for positive mood states, by priming-activating one or the other of these systems it may be possible to influence individuals’ emotional responses. This priming could be performed by manipulating the spatial location of emotional stimuli. Thus, more positive assessment of stimuli should occur when stimuli are presented in upper space (when processed by the ventral stream) and more negative assessment should occur when stimuli are presented in lower space (when processed by the dorsal stream).

Influence of Spatial Attention on Emotion

As with research on hemispheric asymmetries in emotional processing, it is possible that the vertical location of stimuli might also facilitate the speed and accuracy of emotional judgments, such that positive stimuli in upper space would be more quickly judged as being positive and negative stimuli in lower space would be more quickly recognized as being negative. Support for this postulate comes from the research of

Meier, Sellborn, and Wygant (2007), who demonstrated that neurologically healthy participants categorized (via response box selection) moral words (e.g.s, “honest,”

“upstanding”) more quickly when they were presented in upper portions of the screen whereas immoral words (e.g., “underhanded,” “guilty”) were categorized more quickly 24

when they were presented in lower portions of the screen. This work was preceded by

Meier and Robinson (2004), who examined reaction times for category judgments of words that have either a positive or negative valence (e.g., ‘hero’ versus ‘liar’) when presented in upper or lower space. Again, they found that positive words were more readily categorized as ‘positive’ when they appeared in upper space while negative words were more readily categorized as ‘negative’ when they appeared in lower space.

Interestingly, in a follow-up experiment the authors argued that spatial location does not influence emotional evaluations directly, since judgments of positive and negative words in center space were not facilitated after attention was first directed toward upper or lower portions of space. Importantly, redirection of attention to center space may have overshadowed the potential role of spatial attention on concurrent (versus delayed) emotional evaluations.

A related study by Crawford, Ochsner, Drake, and Murphy (2005) investigated these vertical dichotomies by exploring the interaction between emotion and spatial memory. Specifically, they examined participants’ spatial recall for vertically presented emotional pictures from the International Affective Picture System (IAPS; Lang, Bradley,

& Cuthbert, 1999). Participants viewed pictures of both positive and negative events

(e.g., positive = a couple laughing, puppies; negative = a starving child, a gun directed at the viewer) which were randomly presented in one of 60 different locations, distributed evenly across upper or lower portions of vertical space. Sixty different pictures were presented during an initial exposure period in one of the 60 evenly space locations. Following presentation of all 60 pictures, participants were asked to recall the original space of each picture, presented randomly one by one, by dragging the picture

to the recalled location of its first appearance. On average, participants recalled positive pictures as appearing more often in upper portions of space while they recalled negative pictures as appearing more often in lower portions of space. Results from this study suggest that positive and negative emotional pictures may generate corresponding vertical representations independent of those in the environment and these may influence vertical localization of the emotional picture during later recall.

Since the dorsal and ventral streams are specialized for processing information in lower versus upper space, individuals should theoretically engage these respective streams to a greater extent depending on the spatial location of target information. In effect, selective engagement of dorsal versus ventral streams – by manipulating the spatial location of target stimuli – may prime the perception of greater negative versus positive emotional content.

While previous work has explored how the vertical location of stimuli can facilitate positive-negative semantic judgments and reaction times (Meier, et al., 2007; Meier, et al., 2004; Meier & Robinson, 2004), studies exploring the influence of spatial orienting on emotional perception have largely been restricted to categorical judgments (deciding whether an picture is ‘positive’ or ‘negative’) in the horizontal plane (e.g.s, Van Strien &

Van Beek, 2000; Atchley, Ilardi, & Enloe, 2003; Adolphs, Jansari, & Tranel, 2001). The current study aimed to address this limitation by examining more subtle effects of spatial attention on emotion (graded ratings of how positive or negative a stimulus is) in the vertical plane.

Influence of Emotion on Spatial Attention

There is far more information present in the environment than we can simultaneously process. Attention is the means of selecting information from the 26

environment for further processing amongst many competing options. As proposed by

Heilman and Valenstein (1979), attentional networks may limit processing to a certain sensory modality – for instance, attending to only visual inputs in the presence of ambient background noise – or limiting sensory processing to stimuli within a region of the environment – e.g., objects only in upper versus lower space. These attentional allocations may be influenced by concurrent, higher-level cognitive processes, which allow selection of information based on the organism’s goals and needs for survival.

Emotional state may be one such cognitive process that prepares the brain to respond preferentially to information in certain regions of space. Indeed, emotion elicitation studies have shown that negatively versus positively induced emotions predictably alter the direction of spatial attention in the vertical plane. For instance,

Wapner and colleagues (1957) created a paradigm in which neurologically healthy study participants (undergraduates anticipating feedback on midterm grades) were presented with their actual midterm grades between two attempts at a visuospatial attention task. The participants were selected for inclusion in the study based on whether they had actually received an ‘A’ or an ‘F’ in the experimenter’s psychology class – conditions expected to produce the greatest differences in experience of either objective success or failure. During the visuospatial task, participants were placed in a dark room and asked to designate the point along a 20x20cm luminous square corresponding to their eye level by bisecting the square with a horizontal rod. After the experimenter casually communicated the outcome of the participant’s midterm grade during a break, the participants were asked to bisect the luminous square once more.

The researchers found that individuals who received feedback that they achieved an ‘A’

on their midterm bisected the luminous square higher following feedback on their grade

(compared to their initial attempt) whereas those who received an ‘F’ bisected the square lower compared to their initial attempt. Although mood was not objectively quantified, the researchers noted that the grades elicited mood-congruent behaviors in line with the predicted outcomes of the grade manipulation – that is, individuals receiving an ‘A’ smiled while their less successful counterparts (those who received the

‘F’) appeared tearful and cried. These results support the possibility that negative and positive mood states – as suggested by the objective experience of either success or failure and physiological signs of either distress or joy – can impact the subsequent direction of one’s vertical spatial attention.

A similar study by Meier and Robinson (2006) investigated the impact of more enduring, endogenous mood states by evaluating self-reported depressive symptoms through the Beck Depression Inventory (BDI; Beck, Rush, Shaw, & Emery, 1979). The research study required categorical judgments of positive and negative words in center space (i.e., stating ‘positive’ or ‘negative’). The investigators found a positive relationship between BDI scores and speed of responding to subsequently presented, unrelated targets in lower versus upper space (letter q versus letter p discriminations).

That is, the higher an individual’s BDI score, the faster they were to respond to targets in lower space compared to upper space. This relationship was predominantly seen at higher score ranges (i.e. those with lower BDI scores did not demonstrate as predictable patterns of reacting to stimuli in upper versus lower space). Results from this study suggest that the more negative the individual’s endogenous emotional state, the stronger the spatial attention bias toward targets in lower vertical space. Importantly,

the researchers did not reveal whether specific criteria were applied to exclude individuals for clinically significant depression, though BDI scores ranged from 0 (no depressive symptoms) to 20 out of 63 possible points. Further, since the researchers were interested in the influence of depressive symptoms on vertical selective attention, they did not examine differences in responding to upper versus lower visual targets based on the valence of priming stimuli in center space. It therefore remains possible that any changes related to the priming stimuli may have been masked by an overall enhanced bias toward responding to stimuli in lower space for those with higher BDI scores.

These data collectively suggest that emotional state might influence how attention is directed in the environment, and the direction of attention toward a specific portion of space may be predictably altered by the valence assigned to incoming information. Likewise, it is possible that more positive or negative judgments of emotional information might direct attention further up or down in space along the vertical plane, just as activation of the right versus left hemisphere might direct attention toward the right or left.

Influence of Emotion on Action-Intention

For purely spatial tasks (e.g., line bisection), the direction of the individual’s attention may be inferred by the degree of deviation toward a specific portion of space

(Chatterjee, Mennemeier, & Heilman, 1992). While emotion may indeed influence the direction of attention in the environment, this is most often assessed using a motor- intentional task, for instance, recording the positive or negative value of a stimulus along a line as in the current study. Thus, also important in understanding the interaction

between emotion processing and space is the influence of different emotions on approach-avoidance behaviors.

Denny-Brown and Chambers (1958) posited and provided evidence that whereas the frontal lobes mediate avoidance behaviors the posterior temporal and parietal lobes mediate approach behaviors. Positive emotions are considered to be on the approach continuum whereas negative emotions motivate avoidance (Kinsbourne, 1978;

Davidson, 1995). As mentioned previously, the left hemisphere has been considered dominant for processing positive emotions whereas the right has been considered dominant for processing negative emotions (Canli, Desmond, Zhao, Glover, & Gabrieli,

1998; Davidson, Ekman, Saron, Senulis, & Friesen, 1990; Tomarken, Davidson,

Wheeler, & Doss, 1992). Thus, while the posterior and left hemisphere cortices motivate one to approach, the anterior and right hemisphere cortices motivate one to avoid.

Approach-avoidance behaviors might also be elicited by simple categorization of positive and negative concepts, which might motivate certain spatial predispositions. In a study by Foster and colleagues (Foster et al., 2008), which examined the placement of emotionally labeled pegs within an axially aligned board, a bias was observed in placement such that positively labeled pegs (happy, joyous) were placed in more distal portions of space (towards the top of the workspace) whereas negatively labeled pegs were placed in more proximal portions of space (towards the bottom of the workspace).

Thus, the tendency to represent positive emotions “higher” in space and negative emotions “lower” in space was maintained, even in the absence of explicit task demands or mood induction. Notably, only positive emotionally labeled pegs were placed significantly higher in space (i.e. further away from the central horizontal axis)

compared to negative emotionally labeled pegs. Negative emotionally labeled pegs did not deviate significantly from center, but were significantly different in their placement compared to positive emotionally labeled pegs. A significant deviation upward for positive pegs versus the non-significant deviation of negative pegs provides support for the possibility that the ventral stream may contribute a stronger role to emotional processing, just as seen for the right relative to left hemisphere (e.g., Tucker and

Frederick, 1989).

Spatial action-intention biases toward left and right portions of space, induced by viewing emotional pictures have been virtually unexplored. Positive or negative emotions – and consequently, asymmetrical left versus right hemisphere activation – might prompt spatial biases toward right or left hemispace. Therefore, in addition to assessing the influence of the vertical (upper versus lower space) presentation of emotional pictures on eliciting emotional experience, this study aimed to consider the additional influence of the induced emotion on the allocation of right-left spatial attention or action-intention. By using horizontal lines to rate valence (i.e., marking points on a line that correspond to positive-negative valence judgments) this study sought to determine how the presentation of positive, neutral, and negative emotional pictures in upper versus lower space might induce a right or left spatial bias. Thus, a secondary research aim was to examine whether judgments of negative emotional pictures might facilitate an overall shift toward right hemispace and positive emotional pictures might facilitate an overall shift toward left hemispace (or vice-versa) and whether these directional biases might be influenced by the vertical position of presentation (upper or lower space).

Whereas the presence of hemispatial biases may be related to either sensory- attentional or motor-intentional mechanisms, the dissociation of these processes would entail an additional study incorporating the influence of picture reversal on spatial biases

(e.g., Na, Adair, Williamson, Schwartz, Haws, & Heilman, 1998). While this could certainly be the goal of future studies, investigating the mechanism of this possible spatial bias was beyond the scope of the current study.

Emotion and Physiology

In addition to the subjective qualities of an emotion, emotional experiences are also associated with changes in the autonomic nervous system (ANS). The ANS is responsible for engaging the “fight or flight” response when an organism encounters potentially dangerous stimuli in the environment and this then motivates the organism to escape or protect oneself against threat. Because of the amygdala’s close connections with the ANS (Chapman, Schroeder, Geyer, Brazier, Fager, Poppen, Solomon, &

Yakovlev, 1954; LeDoux, Iwata, Cicchetti, & Reis, 1988; Lee, Arena, Meador, Smith,

Loring, & Flanigin, 1988; Amaral, Price, Pitkanen, & Carmichael, 1992) and observed role in fear conditioning (Adolphs, Tranel, Damasio, & Damasio, 1995), the amygdala has been considered principal in mediating the ANS response to negative stimuli.

The amygdala is able to mediate the response to negative stimuli and the conditioned fear response via extensive and reciprocal subcortical and cortical connections. Quick, subcortical inputs from the thalamus to the lateral nucleus of the amygdala for instance, allow a rapid, automatic response to conditioned stimuli

(LeDoux, 1992), including acoustic stimuli during experimental fear conditioning

(LeDeux, Cicchetti, Xagoraris, & Romanski, 1990). Additional input from both the hippocampus (Ottersen, 1982, Amaral, et al.,1992) and cortex (Romanski & LeDoux, 32

1993) permit evaluation of threat based on previous experience, allowing the organism to further assess true danger and respond accordingly. The amygdala, via reciprocal connections with sensory association areas, can then alter the resulting flow of information and modulate how sensory information is subsequently perceived (LeDoux,

1995).

The startle reflex is a brainstem reflex that occurs in response to unexpected stimuli and is considered an observable component of the ANS response. In the experimental environment, this is most often elicited via a brief, loud, sudden burst of noise while the participant completes an experimental task. Changes in the startle reflex are most reliably measured via a fast flexion of the muscles surrounding the eye, referred to as the startle eyeblink (Anthony, 1985). Changes in the amplitude of the eyeblink response can then be measured against the specific conditions of a task, permitting inferences about how external stimuli may influence this behavioral response.

Through its connections with the ANS, the amygdala is able to effectively modulate the startle eyeblink reflex. Amygdala modulation occurs via projections from the central nucleus to the nucleus reticularis of the pons (Rosen, Hitchcock, Sananes,

Miserendino, & Davis, 1991). As mentioned, reciprocal connections with the cortex may alter the response of the amygdala to various stimuli based on an organism’s perceived level of threat. Likewise, the magnitude of the startle eye blink reflex is amplified when participants view negative emotional pictures or stimuli (Bradley, Cuthbert, & Lang,

1990, 1991; Cook, Hawk, Davis, & Stevenson, 1991; Vrana, Spence, & Lang, 1988;

Vrana & Lang, 1990), whereas this response is attenuated when participants view positive emotional pictures and stimuli (Grillon & Davis, 1995; Vrana, 1995; Bradley, et

al., 1990). These opposing responses suggest that negative emotions or emotional stimuli may somehow tap into the amygdala and its readiness to perceive threat for immediate action. In contrast, the amygdala may identify less need for the “fight or flight” when the organism is processing pleasant, non-threatening stimuli. Thus, observable measures of ANS change like startle eyeblink can lend additional insight into the perceived valence of emotional stimuli as being more positive or negative.

Moreover, measurement of startle eyeblink provides an objective means of assessing how valence may be assigned (and altered) under various conditions (e.g., with change in spatial location) in addition to subjective report.

In terms of the respective roles of dorsal and ventral stream involvement in physiological arousal during emotion, it has been shown that the amygdala demonstrates strong, reciprocal connections with visual areas of the ventral processing stream via the basal nucleus (Amaral, Behniea, & Kelly, 2003). Thus, both cortical areas within the ventral stream and the amygdala may play a role in determining how visual information is processed and perceived. As reviewed, the amygdala has been linked to heightened startle reflex during emotional processing (Davis, 1992) and this reflex is lost with amygdala damage (Hitchcock & Davis, 1986). However, it remains unclear if the ventral versus the dorsal stream is more likely to inhibit or active the portions of the amygdala that modulate the startle reflex. Thus, it is possible that pictures presented in upper space (opposing the ventral visual stream) might be associated with either enhanced or diminished startle amplitude presumably via activation or inhibition of the amygdala whereas the opposite might occur when pictures are presented in lower space (opposing the dorsal visual stream).

In terms of the relative contributions of the amygdala in the left versus right hemisphere, mixed findings have been reported. For instance, greater left relative to right amygdala activation has been shown in functional imaging studies in response to negative stimuli (Isenberg, Silbersweig, Engelien, et al., 1999; Strange, Henson, Friston,

& Dolan, 2000). In other imaging studies, greater left amygdala activation has been shown in response to both negative and positive stimuli (Canli, Zhao, Brewer, Gabrieli,

& Cahill, 2000; Hamann & Mao, 2002; Hamann, 2001). While these data appear to conflict with dominance theory of the right hemisphere’s role in emotional processing, it is possible that activation of the left amygdala reflects less specialized (more effortful) processing. Conversely, evidence from brain injury has demonstrated a stronger role for the right relative to the left amygdala in the startle reflex, particularly in response to negative stimuli. In one patient with a lesion restricted to the right amygdala, diminished startle and lack of potentiation to negative stimuli was observed (Angrilli, Mauri,

Palomba, Flor, Birbaumer, Sartori, & di Paola, 1996). These observations suggest that isolated lesions of the right amygdala are sufficient to interfere with the startle reflex, and provide data supporting the role of the right hemisphere in processing negative emotional stimuli. Due to these conflicting findings, it remains unknown whether the left or right amygdala may be more involved in processing positive and negative emotional stimuli and responsible for mediating the startle response during picture evaluation.

Likewise, it also remains unknown whether emotional stimuli presented to the left or right hemifield might elicit a more amplified, or well-modulated (diminished) startle reflex.

Together, the present study aimed to obtain objective data on how the emotional quality of positive, neutral, and negative pictures may be altered based on spatial location of picture presentation. Further, this study aimed to elucidate the respective roles of the ventral versus dorsal streams and right versus left hemisphere in modulating the startle eyeblink reflex. It was proposed that the startle eyeblink reflex would be measured in response to sudden bursts of noise stimulation as participants viewed emotional pictures. Startle amplitude would then be examined for the influence of positive and negative stimuli compared to neutral stimuli when presented in upper, lower, right, left, and middle space. It was expected that differences in startle amplitude would be observed for negative relative to positive stimuli when compared to neutral pictures. It was further expected that spatial location would modify the amplitude of the startle response. The direction of this change in amplitude (potentiation or attenuation) was therefore proposed an exploratory aim of the current study.

CHAPTER 3 STUDY AIMS AND HYPOTHESES-PREDICTIONS

Purpose of the Study

Studies of the relationships between spatial attention and emotion are critical to understanding the nature of emotion processing in neurologically healthy adults. Those people who feel “down” might direct attention downward and engage the egocentric dorsal stream to a greater extent than their ventral stream. Heightened activation of the dorsal stream might then lead to enhanced readiness for processing negative information. In contrast, those who feel “up” might instead attend upward and – upon engaging the allocentric ventral stream to a greater extent – remain better prepared to process information as being more positive. If spatial attention impacts how emotions are qualitatively perceived, this might also provide insight into the cyclical nature of negative mood states. That is, it might explain why certain individuals become more withdrawn and pull away from potential sources of support when they feel depressed while individuals who feel happy seek opportunities to interact with others and perceive greater social connection. Ultimately, this insight may allow for modifications for existing psychological treatments in clinical populations by incorporating efforts to direct one’s attention either upward or downward during therapeutic engagement.

As mentioned previously, strong evidence suggests that emotional judgments can influence the direction of spatial attention, particularly when stimuli have clear categorical boundaries (e.g., determining a positive or negative association for the label

“happy” versus “sad,” or identifying whether the picture of a starving child is “good” or

“bad”). However, it is less established whether the direction of spatial attention

(attending more toward lower versus upper space) can also influence subtle

components of emotional perception and whether these exist along a graded continuum. That is, can spatial attention influence how positive or negative we perceive a stimulus to be?

Much of the work exploring the relationship between visuospatial and emotional processing has focused on abstract concepts (e.g., words describing the divine, judgment of various adjectives) and categorical judgments of emotional pictures (i.e., the IAPS; Lang, Bradley, & Cuthbert, 2005). The ability to accurately judge the emotional quality of a visual picture may carry important predictive value in reflecting the quality of one’s personal interactions, their perception of social support in the environment, and ability to respond to perceived threats appropriately (Salovey &

Mayer, 1989). Thus, an individual’s ability to interpret the quality of an emotional picture seems critical for further investigation. Though the dorsal and ventral visual processing streams may moderate the relationship between visuospatial attention and emotional perception, it has received little investigative attention. Therefore, the present study aimed to examine the possible role of differential ventral and dorsal stream engagement on emotional perception, by manipulating the spatial location of emotional pictures.

Specific aims, hypotheses, and predications are presented in Tables 3-1 and 3-2 for reference throughout.

Table 3-1. Overview of specific aims, hypotheses, and predictions for Upper-Lower and Right-Left conditions Condition Specific Hypothesis Prediction Aim Upper- #1: Since the ventral and dorsal When emotional pictures are presented in Lower Influence streams mediate attention toward upper space (to the ventral stream), of Spatial upper and lower space (and participants will rate pictures as more Attention upper and lower space have been positive than those presented in middle on the associated with up=good and space. Likewise, when emotional pictures Perceptio down=bad evaluations), the are presented in lower space (to the dorsal n of ventral stream may also mediate stream), participants will rate them as more Emotions processing of positive emotions negative compared to pictures in middle while the dorsal stream may space. mediate negative emotions. In effect, attention toward upper and lower space might enhance the perception of positive and negative emotional valence, respectively.

Right- #1: Valence theory states that the When pictures are presented in left space Left Influence right hemisphere is dominant (to the right hemisphere), participants will of Spatial for processing negative rate emotional pictures as more negative Attention emotions whereas the left compared to pictures presented in middle on the hemisphere is dominant for space. When pictures are presented in Perceptio processing positive emotions. right space (to the left hemisphere), n of participants will rate emotional pictures as Emotions more positive compared to pictures presented in middle space.

Upper- #2: Since each hemisphere attends Upon viewing negative pictures, Lower Influence to contralateral space, negative participants will mark the horizontal of pictures should stimulate greater valence line closer to the left end of the Emotion right hemisphere engagement line (opposing the right hemisphere). Processi and heightened attention (and Likewise, upon viewing positive pictures, ng on intention) toward left hemispace participants will mark the horizontal Attention whereas positive pictures would valence line closer to the right end of the or stimulate greater left hemisphere line (opposing the left hemisphere). In Intention engagement and heightened effect, a significant interaction between al Spatial attention (and intention) toward valence and label position will appear Biases right hemispace. such that positive pictures are rated as more positive and negative pictures are rated as more negative when the positive label is positioned on the right (and negative label is on the left).

Table 3-1. Continued Condition Specific Aim Hypothesis Prediction Right-Left #2: Influence It is posited that while the It is expected that upon viewing of Emotion ventral and dorsal streams negative pictures (with engagement of Processing mediate attention toward upper the dorsal stream) participants' attention on Attention and lower space, they may also will be directed downward and they will or Intentional be responsible for processing mark the vertical valence line closer to Spatial positive and negative emotions. the bottom of the line. It is expected that Biases It is expected then, that upon upon viewing positive pictures (with viewing negative pictures the engagement of the ventral stream), dorsal stream may be participants’ attention will be directed engaged to a greater extent upward and they will mark the vertical and this may direct attention valence line closer to the top. Thus, a and spatial biases downward. significant interaction between Conversely, upon viewing valence and label position would be positive pictures, the ventral expected such that positive pictures are stream may be engaged to a more positive and negative pictures are greater extent and this may more negative when the positive label direct attention and spatial appears at the top. biases upward.

Upper- #3: Influence The startle eye blink is a Since the ventral stream primarily Lower of Emotion protective reflex and the ventral processes stimuli in upper space, Processing stream appears to have more emotional pictures presented in upper on direct access to the amygdala, (versus middle or lower) space will elicit Physiological a critical portion of this stronger startle responses regardless Responding response system. Stronger of the valence of emotional pictures connections of the amygdala presented. along the ventral stream may in turn lead to stronger levels of arousal when this emotional network is engaged.

Right-Left #3: Influence Information processed by the Pictures presented in left hemispace (to of Emotion right relative to left amygdala the right hemisphere) may elicit Processing will more strongly activate the stronger startle responses compared on startle reflex to negative stimuli. to pictures presented in middle space. It Physiological is expected that this effect will be most Responding pronounced for negative pictures.

Table 3-2. Overview of alternative hypotheses, predictions, outcomes, and conclusions for Upper-Lower and Right-Left conditions Condition Specific Alternative Alternative Prediction Outcome Conclusion Aim Hypothesis Upper- #1: Since the ventral Participants will rate Participants Neither Lower Influence visual stream has a emotional pictures in rated pictures prediction of Spatial more direct access upper space (to the presented in fully Attention to the amygdala - - ventral stream) as more lower space supported on the the ventral stream negative than those as Perceptio may instead presented in middle significantly n of mediate space. Likewise, more Emotions processing of participants will rate positive than negative emotions. emotional pictures pictures Since the dorsal presented in lower presented in stream has less space (to the dorsal middle direct access to the stream) as more space. amygdala, the positivecompared to dorsal stream may pictures presented in instead mediate middle space. processing of positive emotions.

Right- #1: Dominance theory When pictures are Participants Neither Left Influence states that the right presented in left space rated pictures predictio of Spatial hemisphere is (to the right presented in n fully Attention dominant for hemisphere), right space as supporte on the processing participants will rate significantly d Perceptio emotional relative emotional pictures more more negative n of to non-emotional intensely compared to than pictures Emotions stimuli. pictures presented in presented in middle space. Thus, middle space. negative pictures will be rated as more negative and positive pictures will be rated as more positive.

Upper- #2: Pseudoneglect, or A significant main A trend Neither Lower Influence specialized effect of label position emerged, such predictio of processing of would be expected such that positive n fully Emotion emotional that positive and pictures were supporte Processi information by the negative pictures are rated as more d ng on right hemisphere rated as more positive positive and Attention may drive a (and less negative) negative or consistent leftward when the positive label pictures were Intention attentional bias, appears at the left end of rated as more al Spatial unrelated to the horizontal valence negative when Biases valence. line. A main effect of the positive label position for label appeared emotional but not non- at the left end emotional stimuli would of the suggest the role of the horizontal right hemisphere in valence line. responding to emotional stimuli in particular.

Table 3-2. Continued Condition Specific Aim Alternative Hypothesis Alternative Prediction Outcome Conclusion Right- #2: Influence Altitudinal A significant main A Alternative Left of Emotion pseudoneglect, or effect of label consistent prediction Processing specialized processing position would be upward supported on Attention of emotional expected such that bias was or Intentional information by the positive and negative seen, Spatial ventral stream may pictures are rated as leading to a Biases drive a consistent more positive (and main upward attentional less negative) when effect of bias, unrelated to the positive label label valence. appears at the top of position the vertical valence line. A main effect of label position for emotional but not non-emotional stimuli would suggest the role of the ventral stream in responding to emotional stimuli in particular.

Upper- #3: Influence It is also possible that Since the ventral Could not be explored Lower of Emotion the ventral stream has stream primarily Processing an inhibitory influence processes stimuli in on on the amygdala, with upper space, Physiologica stronger connections emotional pictures l allowing better presented in upper Responding modulatory control space will elicit over the amygdala’s attenuated startle responses to negative responses compared stimuli. Pictures to pictures presented presented in upper in middle and lower space may instead space. be associated with less preparedness for “fight or flight."

Right- #3: Influence Information processed Pictures presented in Could not be explored Left of Emotion by the left relative to right hemispace (to Processing right amygdala will the left hemisphere) on more strongly activate may elicit stronger Physiologica the startle reflex to startle responses l negative stimuli. compared to pictures Responding presented in middle space. It is expected that this effect will be most pronounced for negative pictures.

Specific Aim #1: Influence of Spatial Attention on the Perception of Emotions

Upper and Lower Space

To investigate whether vertical (upper and lower) spatial attention influences emotion perception, pictures that have been judged as inducing a variety of emotional experiences (positive, neutral, and negative) were presented in the current experiment in upper, middle, and lower visual space. Neurologically healthy participants subsequently rated these pictures based on how positively or negatively they were perceived. This experimental condition was deemed the Upper-Lower condition.

Hypothesis-1

Since the dorsal and ventral streams have different vertical attentional biases, and these two streams may also be connected to networks that mediate emotions of different valence, the vertical spatial location of emotional pictures in upper versus lower space may influence the strength of the emotion elicited. That is, pictures presented in upper space might be associated with stronger ventral stream activation and this should support stronger perceptions of positive emotion. In contrast, pictures presented in lower space might lead to stronger dorsal stream activation and this should support stronger perceptions of negative emotion.

Prediction-1

Based on the hypothesis that dorsal stream activation facilitates negative emotional processing and ventral stream activation facilitates positive emotional processing, pictures presented in upper space should stimulate stronger ventral stream activation, facilitating greater positive emotional evaluations, while pictures presented in lower space should stimulate stronger dorsal stream activation, and greater negative emotional evaluations. In the context of the present experimental design, it was

therefore predicted that participants would rate pictures presented in upper space as more positive than those presented in middle space whereas the reverse would be true for pictures presented in lower space (i.e., participants would rate pictures presented in lower space as more negative compared to pictures presented in middle space). It was predicted that this relationship would persist across all three valence categories – thus, negative and positive images should be less negative and more positive, respectively in upper space while negative and positive images should be more negative and less positive in lower space compared to middle space. Predictions were made relative to middle space predominantly as directional effects might implicate the importance of one stream over the other when compared to the neutral center. A depiction for this prediction is shown in Figure 3-1.

Figure 3-1. Depiction of predicted outcome for Specific Aim #1 in the Upper-Lower condition. It was predicted that pictures presented in upper space would be rated more positively whereas pictures presented in lower space would be rated more negatively.

Alternative prediction-1

The alternative hypothesis related to the greater neuroanatomical connections between the ventral stream and amygdala. The amygdala is critical for mediating negative emotions such as fear and anger (Aggleton & Young, 2000; LeDoux, 1996).

Since the ventral visual stream has a more direct access to the amygdala (Amaral, et al., 2003), it was alternatively predicted that participants might instead rate pictures presented in upper space as more negative compared to pictures presented in middle space. In contrast, since the dorsal stream has less direct access to the amygdala, it was alternatively predicted that pictures presented in lower space (to the dorsal stream) would be rated as more positive relative to pictures presented in middle space. Based on this supposition relative to the amygdala, it also remained possible that this effect would be seen specifically for negative stimuli, such that negative pictures presented in lower space would be rated as more positive than negative pictures in middle space whereas negative pictures in upper space would be rated as more negative than pictures presented in middle space. A depiction for this alternative prediction is shown in

Figure 3-2.

Figure 3-2. Depiction of the alternative predicted outcome for Specific Aim #1 in the Upper-Lower condition. It was alternatively predicted that pictures presented in upper space would be rated more negatively whereas pictures presented in lower space would be rated more positively.

Right and Left Space

To build upon existing literature and investigate whether horizontal (right and left) spatial attention influences subtle differences in emotion perception, positive, neutral, and negative pictures were also presented in right, middle, and left space. These were also rated by the participants based on how positively or negatively the pictures were perceived. This experimental condition was deemed the Right-Left condition.

Hypothesis-2

Hypothesis 2 posited that the horizontal spatial location of emotional pictures would influence the positive or negative quality of emotion perceived. Since pictures presented in one hemifield are processed by the contralateral hemisphere, pictures presented in left space should be associated with stronger right hemisphere engagement while pictures presented in right space should be associated with stronger

left hemisphere engagement. In accordance with valence theory, pictures presented in left space (to the right hemisphere) should be associated with more negative evaluations while pictures presented in right space (to the left hemisphere) should be associated with more positive evaluations.

Prediction-2

In accordance with valence theory, it was predicted that when pictures were presented in right hemispace, participants would rate the pictures as more positive compared to pictures presented in middle space. In contrast, it was expected that participants would rate pictures as more negative when they were presented in left space compared to middle space. A depiction for this prediction is shown in Figure 3-3.

Figure 3-3. Depiction of predicted outcome for Specific Aim #1 in the Right-Left condition. It was predicted that pictures presented in right space would be rated more positively whereas pictures presented in left space would be rated more negatively.

Alternative prediction-2

In accordance with dominance theory, which states that the right hemisphere is dominant for processing emotional relative to non-emotional stimuli, it was predicted that both positive and negative pictures would be rated more intensely (as more positive and more negative, respectively) when presented in left hemispace (to the right hemisphere). A depiction for this alternative prediction is shown in Figure 3-4.

Figure 3-4. Depiction of the alternative predicted outcome for Specific Aim #1 in the Right-Left condition. It was alternatively predicted that pictures presented in left space would be rated more intensely than pictures in middle space; thus, negative pictures would be rated more negatively while positive pictures would be rated more positively.

Specific Aim #2: Influence of Emotion Processing on Attention or Intentional

Spatial Biases

Ventral versus Dorsal Stream Engagement

To determine if spatial biases might be induced by emotion processing and experience as assessed by self-report, horizontal or vertical valence lines were shown

following the presentation of emotional pictures in the Upper-Lower and Right-Left conditions. Horizontal lines were presented in the Upper-Lower condition whereas vertical lines were shown in the Right-Left condition. Labels for “positive” and “negative” were presented at opposite ends, with the position of these labels counterbalanced across participants. Examples of positioning for valence lines in the Upper-Lower condition are presented in Figure 3-5. Examples of positioning for valence lines in the

Right-Left condition are presented in Figure 3-6. After presentation of each picture on the touch-screen monitor, valence lines appeared in the same space as the preceding image. Upon presentation of the valence line, participants were instructed to indicate how positive or negative the preceding picture appeared to be by marking a point along the line corresponding to how positive or negative the picture was judged. A more detailed description of this setup and the valence lines used is provided in the Methods.

A B

Figure 3-5. Figure illustration of horizontal valence lines shown following critical pictures in the Upper-Lower condition (those presented in upper, middle, and lower space). Valence lines were presented immediately after the emotional picture to be rated, and the valence lines were aligned with the horizontal midpoint of the previously presented picture. The horizontal line was presented following pictures in all five positions, however these were aligned with the left-most and right-most portions of the screen for distractor pictures in left and right space. Participants rated the emotional pictures by placing a mark along the line between the “positive” and “negative” labels. The “positive” label position was counterbalanced such that half of the participants viewed the positive label on the right side of the line (A) and half viewed it on the left (B).

A B

Figure 3-6. Illustration of vertical valence lines shown following critical pictures in the Right-Left condition (those presented in left, middle, and right space). The vertical valence line was presented following pictures in all five positions, however these were aligned with the top-most and bottom-most portions of the screen for distractor pictures in upper and lower space. The “positive” label position was counterbalanced such that half of the participants viewed this label on the top of the line (A) and half viewed it on the bottom (B).

Hypothesis-3

It has been posited that negative emotions and emotional experiences are associated with a stronger engagement of the right hemisphere while positive emotions activate the left hemisphere (Canli, et al., 1998; Davidson, et al., 1990; Tomarken, et al.,

1992). Since each hemisphere attends to contralateral space (Kinsbourne, 1970), it would be expected that negative pictures would stimulate greater right hemisphere engagement and heightened attention (and intention) toward left hemispace whereas positive pictures would stimulate greater left hemisphere engagement and heightened attention (and intention) toward right hemispace.

Prediction-3

It was predicted that upon processing content in negative pictures during the

Upper-Lower condition, participants would mark the horizontal valence line closer to the left end of the line (opposing the right hemisphere). Likewise, it was expected that upon processing content in positive pictures presented during the Upper-Lower condition,

participants would mark the horizontal valence line closer to the right end of the line

(opposing the left hemisphere). In effect, a significant interaction was predicted between valence and label position for the Upper-Lower condition such that positive pictures would be rated as more positive and negative pictures would be rated as more negative when the positive label was positioned on the right (and negative label was on the left).

This predicted relationship is depicted in Figure 3-7.

Figure 3-7. Depiction of predicted outcome for Specific Aim #2 in the Upper-Lower condition. Image represents the expected tendency upon rating emotional pictures along the horizontal valence line. Based on valence theory, which states that the right hemisphere processes negative emotions and the left hemisphere processes positive emotions, a valence by label position interaction was predicted, such that negative pictures would be rated as more strongly negative and positive pictures would be rated as more strongly positive when the positive label position appeared on the right side of the line.

Alternative prediction-3

Alternatively, it is possible that uniform spatial action-intention biases exist independent of valence, in accordance with the presence of pseudoneglect (Bowers &

Heilman, 1980; Jewell & McCourt, 2000), a leftward bias observed in neurologically healthy adults during horizontal, solid line bisection. In effect, it was alternatively predicted that regardless of the picture valence and label position along the horizontal valence line, participants would demonstrate a consistent leftward bias consistent with the presence of pseudoneglect in the Upper-Lower condition. This would be evidenced by a significant main effect of label position, such that both positive and negative pictures would be rated as more positive (and less negative) when the positive label was positioned on the left end of the line.

A consistent leftward bias might also be seen due to heightened right hemisphere engagement during processing of emotional stimuli. Since the right hemisphere has been posited to be dominant for processing emotional stimuli (both positive and negative), in accordance with this dominance theory, the right hemisphere might be engaged to a greater extent during emotional picture rating in general.

Activation of the the right hemisphere and attention toward contralateral space would then result in stronger attention (and intention) toward left space. This alternative, predicted relationship is depicted in Figure 3-8. To dissociate these effects (spatial versus emotional), the main effect of label position in the Upper-Lower condition was further compared between neutral (non-emotional) pictures relative to positive and negative emotional pictures.

Figure 3-8. Depiction of the alternative predicted outcome for Specific Aim #2 in the Upper-Lower condition. Image represents the expected tendency upon rating emotional pictures along the horizontal valence line. Based on the observation of pseudoneglect (a tendency to attend to greater portions of left versus right space) and dominance theory, which states that the right hemisphere is specialized for processing both positive and negative emotional states, a main effect of label position was predicted, such that a consistent leftward bias would be observed along the valence line, sugh that negative pictures would be rated as more strongly negative and positive pictures would be rated less positive when the positive label position appeared on the right side of the line. Likewise (as reviewed in Table 3-2), positive pictures would be rated as more positive (and negative pictures less negative) when the positive label appeared at the left end of the line.

Right versus Left Hemisphere Engagement

Hypothesis-4

The ventral stream predominantly attends to stimuli in upper space whereas the dorsal stream attends to stimuli presented in lower space. It was therefore posited that the ventral stream might also be responsible for processing more positive emotions whereas the dorsal stream might be responsible for processing more negative

emotions. It was therefore hypothesized that upon viewing negative pictures in the

Right-Left condition, the dorsal stream might be engaged to a greater extent and this might direct attention and spatial biases downward along the vertical valence line.

Conversely, it was hypothesized that upon viewing positive pictures, the ventral stream might be engaged to a greater extent and this might in turn direct attention and spatial biases upward along the vertical valence line.

Prediction-4

Since negative emotions should engage spatial biases downward, it was predicted that upon viewing negative pictures, participants would mark the vertical valence line closer to the bottom of the line in the Right-Left condition. Likewise, it was predicted that upon viewing positive pictures, participants’ attention would be directed upward and they would mark the vertical valence line closer to the top. Thus, it was predicted that positive pictures would be rated as more positive and negative pictures would be rated as more negative when the positive label appeared at the top of the vertical valence line. In turn, a significant interaction between valence and label position was expected. This predicted relationship is depicted in Figure 3-9.

Figure 3-9. Depiction of predicted outcome for Specific Aim #2 in the Right-Left condition. Image represents the expected tendency upon rating emotional pictures along the vertical valence line. Based on valence theory, which states that the right hemisphere processes negative emotions and the left hemisphere processes positive emotions, a valence by label position interaction was predicted, such that negative pictures would be rated as more strongly negative and positive pictures would be rated as more strongly positive when the positive label position appeared on the right side of the line.

Alternative prediction-4

Alternatively, it is possible that uniform spatial action-intention biases exist independent of valence. In accordance with the presence of altitudinal pseudoneglect

(Suavansri, Falchook, Williamson, & Heilman, 2012), a normal upward bias observed in neurologically healthy adults during solid line bisection, it was posited that a consistent upward bias might be observed regardless of the picture’s valence and label position along the vertical valence line in the Right-Left condition. Therefore it was predicted that participants might demonstrate a consistent upward bias and mark the line closer to the top throughout. Thus, a significant main effect of label position would be expected such that positive and negative pictures would be rated as more positive (and less negative) 55

when the positive label appears at the top of the vertical valence line in the Right-Left condition. This predicted relationship is depicted in Figure 3-10.

Figure 3-10. Depiction of the alternative predicted outcome for Specific Aim #2 in the Right-Left condition. Image represents the expected tendency upon rating emotional pictures along the vertical valence line. Based on the observation of altitudinal neglect (an observed tendency to attend to greater portions of upper space) and a supposed valence theory, in which the ventral stream might be specialized for processing both negative and positive emotions, a main effect of label position interaction was predicted, such that negative pictures would be rated as more strongly negative and positive pictures would be rated as more positive (and negative pictures less negative) when the positive label appeared at the top of the valence line.

A consistent upward bias might also be seen due to heightened ventral stream engagement related to emotional processing. That is, since the ventral stream may be dominant for processing emotional stimuli in general, the ventral stream may be engaged to a greater extent during emotional picture rating. Likewise, a systematic action-intention bias toward upper space due to heightened ventral stream engagement

might result during emotional processing. To dissociate these effects, the main effect of label position was further compared for neutral (non-emotional) pictures relative to positive and negative emotional pictures.

Specific Aim #3: Influence of Emotion Processing on Physiological Responding

To determine if the vertical location of stimuli alters physiological responding to stimuli presented in upper versus lower space and right versus left space, the startle eye blink reflex was recorded and it was planned that this would be correlated with valence ratings for emotional pictures across each space.

Upper versus Lower Space

Hypothesis-5

The startle eye blink is a protective reflex and the ventral stream appears to have more direct access to the amygdala, a critical portion of the emotion network that mediates negative emotions like fear and anger. Stronger connections of the amygdala along the ventral stream should in turn lead to stronger levels of arousal when this emotional network is engaged.

Prediction-5

Since the ventral stream primarily processes stimuli in upper space, this network should be engaged to a greater extent when emotional pictures are presented in upper

(versus lower) space. Thus, it was predicted that emotional pictures presented in upper

(versus lower) visual space would elicit stronger startle responses regardless of the valence of emotional pictures presented.

Alternative prediction-5

It is also possible that the ventral stream has an inhibitory influence on the amygdala, with stronger connections allowing better modulatory control over the

amygdala’s responses to negative stimuli. Since the ventral stream has been posited to be important for processing positive emotions, pictures presented in upper space may instead be associated with less negative evaluations and less preparedness for “fight or flight.” It was therefore alternatively predicted that pictures presented in upper space

(and processed by the ventral stream) would be associated with attenuation of the startle blink reflex and that this attenuation would not be seen for pictures presented in lower space.

Right versus Left Space

Hypothesis-6

The right amygdala appears to play an irreplaceable role in modulation of the startle reflex, particularly in potentiation of the startle response to negative stimuli. It was therefore supposed that information processed by the right amygdala would more directly activate the startle reflex to negative stimuli.

Prediction-6

It was predicted that pictures presented in left hemispace (and processed by the right hemisphere) might elicit stronger startle responses compared to pictures presented in middle space. Further, it was expected that this effect would be most pronounced for negative pictures.

Alternative prediction-6

Although supported moreso through functional imaging than lesion studies, it has also been shown that the left amygdala plays a strong role in processing emotional stimuli relative to the right amygdala, and this may include processing of both positive and negative stimuli. Therefore, it is possible that negative pictures presented in right

hemispace (and attended by the left hemisphere) instead might elicit stronger startle responses and positive pictures presented in right hemispace would be associated with greater attenuation of the startle reflex.

CHAPTER 4 METHODS

Research Design

The primary research question for the current investigation was: how might the direction of spatial orienting influence the viewer’s interpretation of emotion pictures? To investigate this research question, pictures representing a range of emotional valences and intensities were presented to participants followed by opportunities for participants to rate the positive/negative quality of each picture. The spatial position of emotional pictures thus served as the primary experimental manipulation. Its influence on emotional processing was then measured in terms of participants’ ratings of how positive or negative the picture appeared. Participants’ ratings of picture quality thus served as the primary dependent variable.

Apparatus

Experimental stimuli were presented within the bounds of an ELO TouchSystems

42-inch, high-definition touch-screen monitor, with a display screen measuring

36.5x20.5inches (WxH; touch-screen depicted in Figure 4-1, A. Participants were positioned directly in front of the monitor in a sturdy, non-rolling chair (Figure 4-1, B).

The participants were asked to place their head and chin upon a secure head/chin rest

(Figure 4-1, C). placed directly in front of the chair to ensure maintenance of eye level, posture, and viewing angles throughout the experiment. The height of the head/chin rest was adjusted to align the participants’ eyes with the veridical center of the screen

(Figure 4-1, D). such that the center of pictures presented in middle space within the screen would be aligned precisely at eye level. Chair height was adjusted to ensure maximum comfort and participants were encouraged to voice if they became too

uncomfortable with this position and desired a break. Participants were positioned 13 inches from the screen, creating an approximate 38 degree viewing angle (from center to center) between pictures presented in upper and lower space (depicted in Figure 4-1,

E)., and a 62 degree viewing angle between pictures presented in right and left space

(Figure 4-1, F).

Figure 4-1. Illustration of computer setup. Participants were seated directly in front of the 42” touch-screen monitor (A) computer in a sturdy, non-rolling chair (B). Participants were asked to place their head and chin upon a secure chin rest (C) positioned directly in front of their seat, to ensure consistent viewing position throughout the experiment. In this position, participants’ eyes were aligned with the veridical center of the screen (D). This further allowed for a consistent 38 degree viewing angle between upper/lower and middle portions of the screen (E), and a 62 degree viewing angle between left/right and middle portions of the screen (F).

All experimental stimuli and instructions were presented against a grey background on the touch-screen monitor. This was intended to control for the influence of color on affective judgments, as previous work has demonstrated differences in positive-negative judgments based on context brightness (Meier, Robinson, & Clore,

2004).

Emotional Picture Stimuli

The current project utilized pictures from the IAPS (Lang, Bradley, & Cuthbert,

2005). The pictures in this large database have been evaluated by neurologically healthy women and men on several emotional dimensions including: 1) emotional valence (how positive or negative the image appears, on a Likert scale ranging from 1-

9, where smaller values represent more negative images); and 2) arousal level (how physiologically stimulating the image appears, again, as rated based on a Likert scale from 1-9, where smaller values represent less arousing images). The ratings for pictures in this database range in valence from 1.31 to 8.34 and range in arousal from to 1.72 to 7.35. A total of 120 different pictures were selected for distribution across the two primary conditions (Upper-Lower and Right-Left). Thus, there were 60 different images in each condition. A breakdown of this distribution is provided in Appendix B,

Figure B-1 and described in further detail below.

Pictures were presented in one of five possible locations (depicted in Figure 4-2) although only three primary spaces were analyzed in each of two primary conditions.

Pictures to be analyzed will hereafter be referred to as “critical” pictures. In the first experimental condition, the Upper-Lower condition, critical pictures were those presented in upper, middle, and lower space. In the second experimental condition, the

Right-Left condition, critical pictures were those presented in left, middle, and right space. Thus, the critical pictures occupied three of five possible spatial positions while remaining pictures (hereafter referred to as “distractor” pictures) occupied the remaining two spaces in each condition. In each condition, 12 different pictures were viewed in each of the five positions. Since there were three primary positions being testing in each condition, this resulted in a total of 36 “critical” pictures being rated and analyzed in each condition and 24 “distractor” pictures that were rated, but not analyzed.

Figure 4-2. Illustration of five possible positions for presentation of emotional pictures and relative spacing across display positions. Critical pictures in the Upper- Lower condition included those in the midsagittal plane, located at the top, center, and bottom of the screen. Critical images in the Right-Left condition included those located to the left, middle, and right side of the screen.

It was anticipated that some individuals might interpret space as a factor of interest in the study and this might systematically influence their subjective judgments.

Pictures were therefore presented in all five spaces in both conditions rather than just in the three spaces of interest to prevent explicit decision-making patterns (e.g., conscious intention to rate a picture as more positive or negative when it is presented in one space over the other). All critical pictures were landscape-oriented and fitted to a 4.5”x6” frame upon presentation. Therefore, only landscape-oriented emotional pictures were selected as critical pictures, to avoid the effects of black surrounding borders on emotional interpretation.

Three broad valence categories were selected for the experimental trials in the current study: 1) positive images (valence range 6-8.99); 2) neutral images (valence range 4-5.99); and 3) negative images, (valence range 1-3.99). Of each of the 12 pictures presented per space and described above, four of these were positive, four were negative, and four were neutral.

Within each valence category (positive, neutral, and negative) for each condition and in each space, half of the images represented high arousal stimuli (arousal range 5-

6.99 on a 1-9 scale); the remaining represented low arousal stimuli (arousal range 2-

4.99). This ensured a sufficient number of more “ambiguous” low arousal stimuli which might depend more on subjective judgment and be expected to elicit greater variability across participants during valence ratings. It also allowed for a sufficient number of high arousal stimuli which should more effectively elicit the startle reflex and allow comparison of startle amplitude across positions. Thus, half of the high arousal and half of the low arousal stimuli were probed for startle response.

Images were roughly equated across space for luminosity and complexity based on visual inspection by the examiner. More rigorous equating was conducted based on normative valence and arousal ratings from the IAPS database as described further below.

Equating for valence and arousal across Upper-Lower and Right-Left conditions

A One-Way ANOVA was performed to establish potential differences between stimuli assigned to the Upper-Lower versus Right-Left condition. Results of this analysis revealed that there was no difference between the conditions for either average valence, F (1, 70) = .092, p = 762, or arousal, F (7, 70) = .859, p = .357 across all stimuli overall. When divided across valence category, no differences were found for average valence or arousal for negative stimuli (valence, F (1, 22) = .080, p = .780; arousal, F (1, 22) = .170, p = .684) or neutral stimuli (valence, F (1, 22) = .1.449, p =

.242; arousal, F (1, 22) = .140, p = .712). There was no difference in mean arousal for positive stimuli, F (1, 22) = .711, p = .408, though a significant different was found for average valence across positive stimuli, F (1, 22) = 5.91, p = .024. Overall, IAPS normative ratings were more positive for positive stimuli assigned to the Upper-Lower condition (M = 7.40, SE = .12) compared to positive stimuli in the Right-Left condition (M

= 6.88, SE = .18).

No significant differences were revealed between pictures presented in middle space between the Upper-Lower or Right-Left condition in either average valence, F (1,

22) = .052, p = .82, or arousal, F (1, 22) = .52, p = .48. Similarly, no significant differences were revealed between pictures presented in eccentric space between the

Upper-Lower condition (upper and lower positions) and Right-Left condition (left and

right positions) in either valence, F (1, 22) = .04, p = .84, or arousal, F (1, 22) = .37, p =

.55.

Equating for valence and arousal across spatial assignment, within conditions

A One-Way ANOVA was performed to ensure there were no significant differences in image quality or content within each of the two conditions, across the three critical trial positions (i.e., across upper, middle, and lower space for the Upper-

Lower condition and across left, middle, and right space for the Right-Left condition).

Thus, a total of 36 critical items were submitted to a One-Way ANOVA for each experimental condition. For the Upper-Lower space condition, no difference was noted across upper, middle, and lower spatial positions in either mean valence (F (2, 33) =

.002, p = .998) or arousal, F (2, 33) = .034, p= .966, ratings norms, as reported for the

IAPS. A similar finding of no significant difference was revealed for the Right-Left space condition across right, middle, and left spatial positions (valence: F (2, 33) = .005, p =

.995; arousal: F (2, 33) = .400, p = .673).

Analyzing these factors separately across valence groups (negative, neutral, and positive images), no differences were revealed in the average valence for negative (F

(2, 9) = .167, p = .849), neutral (F (2, 9) = .267, p = .772), or positive (F (2, 9) = .119, p

= .890) images selected and distributed across space for the Upper-Lower space condition. Similarly, no differences were noted in average arousal of negative (F (2, 9)

= .021, p = .979), neutral (F (2, 9) = .013, p = .987), or positive (F (2, 9) = .032, p = .969) across space in the Upper-Lower space condition. Similarly, no differences in valence arose for the Right-Left condition across spatial positions for negative (F (2, 9) = .046, p

= .955), neutral (F (2, 9) = .044, p = .957), or positive images (F (2, 9) = .018, p = .982),

nor in arousal (negative: F (2, 9) = .523, p = .610; neutral: F (2, 9) = .070, p = .933; positive: F (2, 9) = .019, p = .981) were found.

Of the 60 stimuli selected for presentation in each condition, 30 items received startle stimulation. Data were therefore further analyzed across the subset of items selected for startle. This comparison ensured that no systematic differences in valence or arousal contributed to differences in startle amplitude elicited across critical spaces.

Results from a One-Way ANOVA revealed no significant differences in mean valence (F

(2, 15) = .001, p = .999) or arousal level (F (2, 15) = .030, p = .970) for items probed while in upper, middle, and lower spaces (for the Upper-Lower space condition).

Similarly, no group differences were noted across items probed in right, middle, and left space (in the Right-Left space condition) for either valence (F (2, 15) = .002, p = .998) or arousal (F (2, 15) = .030, p = .970).

To ensure that no additional aspects of the images might have gone overlooked in the experimental design, stimulus assignment across the two primary critical positions

(i.e., upper and lower positions in the “Upper-Lower” condition and right and left positions in the “Right-Left” condition) were further counterbalanced across participants.

That is, pictures assigned to the two primary critical spaces for one half of participants were assigned to the opposite space for the other half of participants. This division is depicted in Appendix B, Figure B-2. Thus, for the Upper-Lower condition half of the participants (Group 1, N=16) viewed 12 of the 36 critical images in upper space (e.g., images 1-12) and 12 of the 36 critical images in lower space (e.g., 13-24). The other half of participants (Group 2, N=16) viewed the opposite set of 12 images in upper space (e.g., 13-24) and 12 in lower space (e.g., 1-12). Image presentation was divided

in this manner rather than presenting all stimuli in both spaces to control for effects of repeated presentation (i.e., viewing the same stimuli in both locations of interest) on the quality of emotional judgments. Repeated exposure has been shown to impact levels of physiological arousal more so than basic detection or categorization of emotional stimuli

(Codispoti, Ferrari, & Bradley, 2006). However, degree of pleasantness has also been shown to increase for repeated stimuli in some studies (e.g., Zajonc, 1968) and diminish with declines in novelty in others (Martin, 1906). Thus, repeated presentation could produce subtle effects on the degree of positive or negative quality assigned. Both groups viewed the last set of the same 12 critical images in middle space (e.g., 25-36).

To control for the effects of sequencing on ratings, half of the participants in each of the participant groups (N=8) viewed images in one predetermined, pseudorandom order in which no two stimuli were presented in the same spatial location one right after the other. The other half of each group (N=8) received the same stimulus-location pairings in the opposite viewing order. Stimuli were presented in this manner to control for the possible effect of preceding images on subsequent ratings; for instance, the effect of rating a given positive image before versus after viewing several negative images.

Valence Lines

Following presentation of each of the emotional pictures in one of the five spatial positions, the images were replaced by a single valence line with the words positive and negative shown at opposite ends. Images representing the three primary positions of interest and two opposing positive-negative label orientations are presented in Chapter

3, Figures 3-5 and 3-6. Participants were instructed to mark a point along this line that corresponded to the perceived emotional quality of the picture that they just viewed. 68

The participants’ marks along these valence lines (distance from the center of the line, in millimeters, indicating how positive or negative the image appeared) served as the primary dependent variable. Positive values indicated that the mark was made closer to the positive end of the line whereas negative values indicated that the mark was made closer to the negative end of the line.

The precise center of the valence line was aligned with the center of the previously presented image. For images in the Upper-Lower condition presented toward the far left and right edges of the screen, the horizontal line was shifted such that the most lateral aspects of the line (positive/negative labels to the left or right of the line) were aligned against the left or right edges of the viewing window. This was intended to maintain the presentation style for the horizontal valence line, though these trials were not submitted for subsequent analysis. Likewise, for images in the Right-Left condition presented toward the top and bottom of the screen, the vertical line was shifted such that the most superior and inferior aspects of the line were presented at the top and bottom edges of the viewing window, respectively.

The solid valence line was used as opposed to symbolic faces (i.e. a happy or sad face depicted with the Self-Assessment Manikin used in the IAPS) to prevent selections that too closely map onto faces in the images just seen (e.g., matching the curvature of the mouth or eyebrows when images of people are involved). This also supported examination of the effect of emotional processing (more positive or negative experiences) on spatial bias toward one part of space. The end at which the word

“positive” or “negative” appeared was therefore counterbalanced across participants to examine this more effectively. The position of the positive and negative labels remained

consistent throughout each individual participant’s test session. Consistent presentation of the positive label at one end of the line was chosen to avoid the introduction of additional set-shifting demands (e.g., decisions about which end is “negative” on each trial). Thus, 16 individuals viewed the positive label in the Upper-Lower condition on the right, and 16 viewed it on the left. In the Right-Left condition, 16 individuals viewed the positive label on the top of the vertical valence line, and 16 individuals viewed it on the bottom.

Participants

Thirty-two young adults between the ages of 21 and 40 with at least 12 years of education participated in the current study. Participants were recruited from the

University of Florida, Gainesville community, and proximal geographic regions by approved advertisements and word-of-mouth. The study procedures outlined herein were appended to an ongoing investigation of vertical spatial neglect in neurologically healthy younger and older adults, as well as individuals with a history of a single, unilateral stroke. Prior to taking part in any of the experimental procedures, all participants were consented according to the policies and procedures outlined by the

University of Florida Institutional Review Board, as well as the Malcom Randall VA

Medical Center, which provided funding for this study. Following successful eligibility screening and completion of study procedures, participants were compensated with a total of $150 for their time and effort.

Inclusion and Exclusion Criteria

To qualify for the study, individuals expressed that they were willing to complete a brief eligibility screening process, had been considered neurologically healthy, and were willing to consent to the proposed study procedures. Exclusion criteria included:

1.) endorsed history of drug/alcohol abuse sufficient to interfere with activities of daily functioning; 2) endorsed history of brain trauma or neurological disease (e.g.,

Alzheimer’s disease, stroke, epilepsy, head injury with loss of consciousness lasting more than one minute); 3) endorsed history of learning disability as evidenced by trouble with reading, math, or spelling during schooling; 4.) endorsed history of psychological diagnosis or treatment for any Axis I mood disorder without remission; 4) endorsed history of acute or chronic medical illness with organ failure (e.g., congestive heart failure, kidney failure, hepatic encephalopathy); 5) current psychotropic medication regimen that might influence alertness, arousal, and/or attention (i.e., benzodiazepines, barbiturates, anticonvulsants, neuroleptics, amphetamines, and dopaminergic agents, including antidepressants and medication for attention); 6) endorsed history of developmental disorders or complications at birth. These criteria were assessed prior to study enrollment with the Phone Screening Form (Appendix A).

Screening Measures

Benton Handedness Questionnaire

The Benton Handedness Questionnaire (Varney & Benton, 1975) was used to document hand dominance for a number of daily activities, including writing, drawing, throwing, using scissors, using a toothbrush, etc. Handedness has not been shown to play a strong role in positive-negative judgments in the horizontal plane (Van Strien &

Van Beek, 2000; Rodway, Wright, & Hardie, 2003) but our sample was restricted to right-handed individuals nonetheless to control for effects of reversed hemispheric asymmetries to the extent possible. The Benton Handedness Questionnaire assessed preference on ten basic manual activities (e.g.s, using a toothbrush, writing, throwing a ball), and individuals were asked to provide which hand they preferred to use – their

right hand, left hand, or either. Individuals who endorsed right-handedness during the initial phone screen were asked to indicate their hand preference for the ten activities listed. Those who endorsed a right hand preference for eight or more activities (Meador,

Loring, Lee, Hughes, Lee, Nichols, & Heilman, 1999) or denied left hand preference for at least eight activities (may endorse “either”) were considered sufficiently right-handed and were enrolled in the study.

Beck Depression Inventory, second edition (BDI-II)

All participants additionally completed the Beck Depression Inventory, second edition (BDI-II; Beck, Steer, & Brown, 1996) prior to study enrollment. This brief self- report measure was originally designed to document the presence and severity of depressive symptomatology (Beck, Rush, Shaw, & Emery, 1979). The second edition of the BDI was developed to address concerns regarding its content validity and compatibility with DSM-IV criteria (American Psychiatric Association, 1994). In sum, the

BDI-II is a face valid assessment of self-reported symptoms of both somatic and cognitive symptoms of depression. Participants were excluded for scores at or above

14, the accepted cut-off for at least mild depression (Beck, et al., 1996) and these individuals were not enrolled.

Demographics across Counterbalanced, Between-Subjects Factors

A One-Way ANOVA was performed to determine significant differences in demographics (education level, gender, age, and depressive symptoms) across the between-subjects factors of interest (label position) in both Upper-Lower and Right-Left conditions.

For the between-subjects factor of label position, a significant difference in education level was found for the Upper-Lower condition, such that individuals who

viewed the positive label on the right side of the valence line had fewer years of formal education (M = 15.19, SE = .60) compared to individuals who viewed the positive label on the left side of the line (M = 17.56, SE = .61), F(1, 30) = 7.68, p = .010. For the Right-

Left condition, a significant difference in BDI-II score was found for positive label position such that individuals who viewed the positive label on the top of the valence line had slightly lower scores on the BDI-II (M = 1.56, SE = 2.12) compared to individuals who viewed the positive label on the bottom of the valence line (M = 3.38,

SE = 2.60). Importantly, both of these average BDI-II scores fell well below clinical levels (i.e., 14) and both spanned a similar, non-clinical range (0-7 and 0-8, respectively).

Experimental Paradigm

Instructions

Prior to initiating the experiment, participants were read the following instructions, modified from the original IAPS directions: “In this study, we are interested in how people rate pictures that represent a lot of different events that occur in life. For about the next 40 minutes, you will be looking at different pictures projected on the screen in front of you, and you will be rating each picture in terms of how it positive or negative it is. There are no right or wrong answers, so simply respond as honestly as you can.”

Participants were then provided with a visual example of the first valence line they would use to rate images, which corresponded to the orientation and positive label positioning for the first experimental condition (e.g., at the top, bottom, left, or right of the line). They were then read the following, complete overview:

Experimenter: “On the screen in front of you, you will see a line, arranged as a continuum. We call this the ‘valence line,’ and you will be using this line to rate how positive or negative you felt the picture was. On this line,

you will be expected to perform only one rating for each picture that you observe.

“You can see that the valence line varies along a scale. At one extreme along this scale – positive – you felt the picture reflected positive experiences that might be happy, pleasing, satisfying, content, or hopeful. If you felt the picture was completely positive, you can indicate this by marking the line toward the word “positive,” like this (motion toward positive label along valence line). The other end of the scale is when you felt the picture reflected negative experiences that were unhappy, annoying, unsatisfying, melancholic, despairing, or boring. If you felt the picture was completely negative, you can indicate this by marking the line toward the word “negative,” like this (motion toward negative label along valence line). The valence line also allows you to describe intermediate ratings that are somewhere in between, by marking the line at any other points along the scale. If you felt the picture reflected completely neutral experiences that were neither happy nor sad, mark the line in the middle, like this (motion toward the center of the valence line). If, in your judgment, your rating fell between two of these three anchors, then mark the line somewhere in between, like this (demonstrate with valence line) or this (demonstrate again on opposite end). This permits you to make more finely graded ratings of how positive or negative the pictures were.

“The procedure will be as follows: Before each of the pictures which you will rate, there will be a crosshair on the screen that you should attend to. Keep your head and chin in place, with your eyes fixed on this crosshair the entire time it is on the screen. It is important that your eyes remain directed towards the screen when the pictures to be rated are subsequently shown. You'll have only a second or two to view each picture. Please view the picture for the entire time it is on the screen and make your ratings immediately after the picture is removed. If, for some reason, you should miss viewing any picture, please tell the examiner so this can be noted. You should still attempt to rate the picture based on how positive or negative you felt the picture may have been afterward, even if you are unsure of what you saw.

“It is very important not to dwell on your ratings of the pictures, since there will not be much time. We are interested in your own personal ratings. Therefore, please don't make any ratings based on what you believe others might think of the pictures. You can understand how this might bias our results.

“Throughout the experiment, you will be wearing these headphones (motion to headphones) and will hear occasional bursts of white noise. Please disregard these sounds as you complete the tasks and focus only on how positive or negative you felt each image was.

“Before we begin, I’m going to show you some examples of the kinds of pictures you will be viewing and rating. This is just to help you get a feel for how the ratings are done. Do you have any questions before we begin?

Participants then began the practice set, in which representative pictures (a positive, negative, and three neutral pictures) were presented on the screen in each of the five spatial positions, with opportunities to practice marking desired points along the subsequently presented valence line. Following the presentation of sample stimuli, participants were instructed, “Now you know how to do it. Are there any questions before we begin with the experiment? (pause) Great. Let’s get started."

Prior to beginning the subsequent condition (e.g., “Right-Left” if they completed the “Upper-Lower” condition first), participants were shown the second valence line they would be using to rate stimuli, which corresponded to the orientation and positive label positioning for the second experimental condition (e.g., at the top, bottom, left, or right of the line). They were then provided with the following directions: “Just as in the last experiment you will see a line, arranged as a continuum on the screen in front of you.

Only this time, the line will be arranged in the following manner...” Participants were then encouraged to preview the example line before proceeding with the second experimental condition.

Computer Presentation

Emotional images were displayed in one of four pseudorandomized orders (i.e., no two stimuli are presented in the same space one right after the other) for each condition: 1) pseudorandomized order #1; 2) pseudorandomized order #2 (order #1 with images in opposing critical spaces – e.g., upper space images instead presented in lower space and vice versa); 3) pseudorandomized order #3 (order #1 presented in the

reversed order); and 4) pseudorandomized order #4 (order #2 presented in the reversed order). Presentation orders were counterbalanced across participants such that a total of eight individuals (one quarter of the total sample of 32 participants) viewed a given pseudorandomized order. Presentation orders were pre-determined in this way (versus randomization with each participant) to control for effects of emotional carry-over due to rating both negative and positively valenced images in the same run. That is, the effect of seeing three negative images then a positive image, for instance would affect one quarter of the participants similarly and this could be controlled across orders. Further, this was intended to allow more efficient analysis of electrophysiological data, as it would allow for more repeatable and reliable identification of probed items within the acquired presentation set.

The computer paradigm, and timing of repeated stimuli are presented in Figure

4-3. At the start of the first condition, directions were presented in the center of the screen reading, “Indicate how positive or negative the image is” to reiterate the examiner’s instructions to rate the perceived emotional quality of each picture shown.

Directions remained on the screen for approximately two seconds prior to initiation of the experiment, followed by a black and white, pixilated pattern. This pixelated black and white pattern was displayed for 750ms, followed by a fixation cross measuring

1x1inches in the center of the 42” monitor (aligned with the participant’s eye level). The fixation cross remained on the screen for two seconds. Following the two-second period, the fixation cross disappeared and the pixilated screen appeared again for

750ms, followed by an emotional image in one of the five possible locations.

Figure 4-3. Illustration of presentation order and timing of stimuli and response periods during computer paradigm. The horizontal and vertical valence lines remained on the screen indefinitely, until a response was made by marking a point along the line on the screen.

Research on the time course associated with affective labeling of emotional expressions has revealed an early “pre-attentive” period for emotional recognition at approximately 120ms (Eimer & Holmes, 2002; Pizzagalli, Regard, & Lehmann, 1999).

Importantly however, individuals might consciously rely on the spatial position of stimuli to aid decisions if the viewing period is too short for a confident rating. To therefore avoid reliance on this early “unconscious” level of processing, the emotional image was instead presented for a total of 2000ms (two seconds). This period has shown to be sufficient for accurate emotional ratings of the primary emotions in center space and is

associated with sustained ERP activity beyond the early, pre-attentive period (Eimer &

Holmes, 2002). Previous research has shown that individuals are able to accurately detect and categorize emotional stimuli as being fundamentally “positive” or “negative” within a short, subliminal period, as brief as 13.3ms (Dijksterhuis & Aarts, 2003).

However, this timeframe does not allow for sufficient processing of meaning beyond what is necessary for basic detection and survival. Sufficient exposure time was therefore necessary in the current experiment to allow conscious cognitive processing, such that participants could reliably process subtle differences in the positive or negative quality of presented images based on expectedly longer, more involved evaluation.

At the end of the 2000ms presentation period for each image, the pixelated black and white screen reappeared for 750ms, followed by a single horizontal (Upper-Lower condition) or vertical (Right-Left) valence line in place of the previously presented emotional image.

Participants were instructed to mark a point on the valence line that corresponded to the perceived valence of the situation depicted (ranging from extremely positive to extremely negative). The line remained visible on the screen until the participant marked the touch-screen monitor at the desired point along the line. No feedback was provided regarding the quality of participants’ performance, but clarification was provided when necessary regarding directions received prior to the start of the experiment.

Pilot Electrophysiology

To determine the degree to which spatial location impacts participants’ physiological reactivity to positive, negative, and neutral images, pilot startle blink 78

electromyographic (EMG) data was also obtained during both conditions. Previous research has demonstrated that the degree of the startle blink reaction to a brief burst of white noise may be influenced by the participant’s emotional state. That is, it is amplified when individuals are viewing negative scenes, which would predispose one to an avoidance response. Likewise, startle amplitude is attenuated when individuals are viewing images that they find pleasant, as this is more in line with an appetitive response (Lang, Bradley, & Cuthbert, 1990).

Preparation and Electrode Placement

Prior to the start of the Emotional Pictures paradigm, participants were asked to remove any dirt, oil, or makeup on the face and around the eyes to allow for improved contact between the electrode and action potentials elicited by the obicularis oculi muscle. The obicularis oculi muscle is responsible for the slow- and fast-twitch muscle movements that initiate the eyeblink reflex in response to a startle stimulus. This muscle extends below the eye, from the nasal bridge, across the cheekbones, temple, and up across the lower forehead. Previous research suggests that monaural presentation of the startle probe to the left elicits significant modulation of the startle reflex (Bradley,

Cuthbert, & Lang, 1996). Thus, the right hemisphere’s dominance for emotional processing may also provide more reliable startle responses when physiology is measured on the left side of the body, since the left side of the face is controlled by the right hemisphere and has been deemed more emotive (Sackeim, Gur, & Saucy, 1978).

Thus, following skin preparation, two electrodes, prepared with a conductance gel on the underside of the electrode, were placed on this muscle of the left eye. One electrode was positioned just above the eye on the obicularis and the second electrode was positioned just below the left eye on the oculi muscle; the center of these electrodes 79

was aligned with the center of the pupil. A single ground electrode for baseline comparison was placed on the bone of the skull, directly behind the left ear. An illustration of this setup is shown in Figure 4-4.

Figure 4-4. Illustration of electrode placement during startle eye-blink acquisition. An electrode was placed upon the left oculi muscle (A), as close to the lower eye lid as comfortable for the participant, as well as the left obicularis (B), just slightly upon the eyebrow, above the eye. Both were placed upon the participants’ left eye, where the center of the electrode was roughly aligned with the pupil. A final ground electrode was placed upon the bone of the skull, just behind the left ear (C) as a reference point for startle comparison.

Startle Eye-Blink Measurement

During the course of both the Upper-Lower and Right-Left conditions, physiological responding was measured via startle amplitude, or the magnitude of the startle eyeblink reflex following presentation of brief bursts of background white noise.

During both of the experiments, the startle eyeblink response was elicited with single,

95 decibel, bursts of white noise lasting a total of 50 miliseconds (ms) each. These brief bursts of noise were presented binaurally through Sennheiser stereo headphones following a manual trigger (i.e., the experimenter pressed a designated button on a nearby computer keyboard). Following trigger of the startle stimulus, the burst of white noise occurred at randomly assigned 500, 750, or 1000ms delays. These random delays were programmed through EPrime (Schneider, Eschman, & Zuccolotto, 2002) to preclude anticipation of the startle stimulus onset following a set interval. Despite the likelihood of random delays due to experimenter response time variability, these additional delays were built into the EPrime program presuming only negligible deviations in response times across trials. It was planned that half of the stimuli in each condition (30 items in total, comprised of 18 critical images and 12 distractor images) would be probed for a startle response. Startle amplitudes were acquired via a continuous recording of inputs from facial electrodes on a separate laptop using the

AcqKnowledge 2.0 software program (BioPac Systems, Goleta, CA). Please refer to

Lang, et al. (1990) for a more complete review of startle eyeblink rationale and methodology.

Statistical Analyses/Evaluation

Repeated Measures Analysis of Variance (ANOVA)

To review, images in the two opposing spaces in each condition were counterbalanced such that half of the participants (N=16) viewed one set of 12 images in one position (e.g., upper space) and the other set of 12 images in the opposing position (e.g., lower space) while the other half of the group (N=16) viewed each of the

12 images in the opposite positions (e.g., lower and upper space, respectively). The entire set of 32 participants viewed the same 12 critical images in middle space. Once

again, an illustration depicting this division across space is shown in Figure B-2. Since participants never saw the same image twice, it was important to counterbalance stimuli in this manner to ensure that any differences that appeared due to spatial position were not due to inherent differences in the stimuli themselves – i.e., that one set of 12 critical images was not by nature, considered more positive or negative than the opposing set of 12 critical images. During study design, images were equated across space for valence and arousal such that each stimulus set of 12 critical images assigned to upper

(or left) and lower (or right) space did not have significantly different normative IAPS ratings from each other, or from images in middle space (return to Methods for a full review).

In effect, the same 32 participants rated negative, neutral, and positive images in each of the three spaces of interest for both the Upper-Lower and Right-Left conditions.

Therefore, a Repeated measures ANOVA was conducted to examine rating differences based on each of the within-subjects variables of interest. The two within-subjects variables included 1) space (upper, middle and lower when analyzed within the Upper-

Lower condition and right, middle, and left when analyzed within the Right-Left condition); and 2) valence (negative, neutral, and positive). The between-subjects factor of interest was label position (whether the “positive” label appeared at the right or left of the horizontal valence line in the Upper-Lower condition or at the top or bottom of the vertical valence line in the Right-Left condition).

Correction for violations of sphericity: Since the same participants participated in all of the experimental manipulations, the Repeated measures ANOVA presumes that each of the experimental manipulations affected the participants sample

in the same graded manner. Sphericity – a measure of the relationship across manipulations – assumes that across multiple, experimental manipulations (e.g., presentation of positive, neutral, and negative images), differences between each experimental pairing (e.g., ratings for positive versus negative images compared to positive versus neutral images) – when calculated across all participants have the same variance, or quantitative spread about the mean. Larger variances for one pairing versus another would suggest that a given manipulation (e.g. negative images) impacted participants’ ratings less predictably than other manipulations. This would then present a problem as the effect could not be fully accounted for by participant-level factors alone (e.g., the tendency for a person to rate all images as more negative than others). To correct for violations of sphericity, degrees of freedom may be adjusted using the Greenhouse-Geisser or Hundt-Feldt corrections to ensure significant differences exist with more stringent criteria – that is, if they would still appear given a smaller sample.

Paired Samples t-tests

Since it was important to examine the relationship between and within specific space and valence categories, planned paired samples t-tests were performed following the observation of significant main effect and interactions.

Post-test Debriefing

To assess for face validity of the primary research question (the influence of lower versus upper space and left versus right space on negative versus positive ratings of emotional images) all participants completed a Post-test Debriefing Form (Appendix

C) following completion of the experiment. This form assessed participants’ self-ratings of accuracy on the valence line task as a method for reporting emotional judgments,

elicited hypotheses or expectations that may have influenced participants’ pattern of responding, and asked about potential strategies used while rating the emotional images (physical imitation, empathetic imagery, etc.). These responses were considered to ensure unbiased sampling in recruitment (ensure participants do not demonstrate extensive knowledge about emotional processing and/or visual processing stream dichotomies) and to consider the impact of other potential a priori hypotheses on participants’ response styles.

CHAPTER 5 RESULTS

Post-test Debriefing Form

All 32 participants denied having a priori hypotheses about the nature of the task, the specific factors being explored in the study, or anticipated outcomes. The most frequently endorsed strategies for determining how positive or negative each picture was rated included 1) considering what the individuals involved (people or animals) may have experienced (25 individuals); 2) judging the facial expressions of people depicted

(24); 3) imagining what one’s own emotional state might be in a similar situation (20); 4) putting oneself in the shoes of individuals (people or animals) involved (18); 5) considering one’s own facial expression (e.g., strength of smile, eyebrow furrowing) while viewing the images (14); and 6) considering how one’s own body felt (e.g., discomfort, degree of increased heart rate) while viewing the images (13). Overall, no individuals demonstrated biased knowledge about the procedures that might have systematically influenced their performance. Thus, data from all individuals were retained in the analyses.

Dataset Corrections: Effect of Probe Administration

Due to experimental error during the administration of startle stimuli (i.e., manual triggering of white noise via a keyboard button press), several items originally assigned to receive startle stimulation during experimental design instead received 1) early administration (trigger accidentally pressed prior to display of the picture on the screen);

2) late administration (trigger pressed after two-second presentation window); 3) missed administration (trigger deliberately not pressed during interstimulus interval due to missed presentation window); or 4) accidental administration (trigger accidentally

pressed for an item not assigned to receive startle stimulation). Data on the specific items missed across participants and features of items incorrectly probed/missed is documented in Appendix D. Due to sufficient lack of control over extraneous auditory stimuli, the data analyses detailed herein included results from the full, uncorrected dataset (Tables 5-1 and 5-2) as well as a corrected dataset with these items removed

(Tables 5-3 and 5-4).

Table 5-1. Means and standard deviations of average emotional ratings for negative, neutral, and positive pictures presented in lower, middle, and upper space in the Upper—Lower condition. Data below reflect averages for the full dataset, including items incorrectly probed during startle eyeblink administration.

Upper-Lower Condition

N Mean Std. Deviation Skewness Kurtosis Space Valence Statistic Statistic Statistic Statistic Std. Error Statistic Std. Error Lower Negative 32 -71.84 35.96 -0.34 0.41 -0.66 0.81 Middle Negative 32 -94.47 33.98 0.46 0.41 -0.73 0.81 Upper Negative 32 -82.46 32.11 0.17 0.41 -0.95 0.81 Lower Neutral 32 5.08 39.16 0.23 0.41 0.18 0.81 Middle Neutral 32 -9.78 32.46 -0.36 0.41 0.33 0.81 Upper Neutral 32 -6.47 36.33 0.61 0.41 0.88 0.81 Lower Positive 32 90.81 42.77 -0.78 0.41 0.32 0.81 Middle Positive 32 95.05 43.45 -0.91 0.41 0.68 0.81 Upper Positive 32 92.55 40.17 -0.44 0.41 -0.66 0.81

Table 5-2. Means and standard deviations of average emotional ratings for negative, neutral, and positive pictures presented in left, middle, and right space in the Right—Left condition. Data below reflect averages for the full dataset, including items incorrectly probed during startle eyeblink administration.

Right-Left Condition

N Mean Std. Deviation Skewness Kurtosis Space Valence Statistic Statistic Statistic Statistic Std. Error Statistic Std. Error Left Negative 32 -67.86 36.08 0.25 0.41 -0.73 0.81 Middle Negative 32 -66.82 30.54 0.35 0.41 0.21 0.81 Right Negative 32 -80.70 35.37 0.17 0.41 -0.58 0.81 Left Neutral 32 -6.25 34.60 -0.07 0.41 1.60 0.81 Middle Neutral 32 10.05 33.55 0.26 0.41 -0.40 0.81 Right Neutral 32 3.72 30.61 -0.27 0.41 -0.12 0.81 Left Positive 32 79.55 35.44 0.27 0.41 -0.87 0.81 Middle Positive 32 80.63 40.07 -0.26 0.41 -0.41 0.81 Right Positive 32 77.55 39.44 -0.27 0.41 -0.28 0.81

Table 5-3. Means and standard deviations of average emotional ratings for negative, neutral, and positive pictures presented in lower, middle, and upper space in the Upper—Lower condition. Data below reflect averages for the abbreviated Table 5-3. Means and standard deviations of average emotional ratings for negative, neutral, and positive pictures presented in lower, middle, and upper space in the Upper—Lower condition. Data below reflect averages for the abbreviated dataset, upon removal of items incorrectly probed during startle eyeblink administration.

Upper-Lower Condition Std. N Mean Deviation Skewness Kurtosis Std. Std. Space Valence Statistic Statistic Statistic Statistic Error Statistic Error Lower Negative 32 -71.82 35.99 -0.34 0.41 -0.67 0.81 Middle Negative 32 -94.09 34.54 0.48 0.41 -0.76 0.81 Upper Negative 32 -82.33 32.12 0.16 0.41 -0.96 0.81 Lower Neutral 32 5.35 39.36 0.22 0.41 0.12 0.81 Middle Neutral 32 -9.78 32.46 -0.36 0.41 0.33 0.81 Upper Neutral 32 -7.66 34.63 0.49 0.41 0.76 0.81 Lower Positive 32 91.44 41.60 -0.70 0.41 0.15 0.81 Middle Positive 32 95.05 43.45 -0.91 0.41 0.68 0.81 Upper Positive 32 92.55 40.17 -0.44 0.41 -0.66 0.81

Table 5-4. Means and standard deviations of average emotional ratings for negative, neutral, and positive pictures presented in left, middle, and right space in the Right—Left condition. Data below reflect averages for the abbreviated dataset, upon removal of items incorrectly probed during startle eyeblink administration.

Right-Left Condition Std. N Mean Deviation Skewness Kurtosis Std. Std. Space Valence Statistic Statistic Statistic Statistic Error Statistic Error Left Negative 32 -67.86 36.08 0.25 0.41 -0.73 0.81 Middle Negative 32 -66.82 30.54 0.35 0.41 0.21 0.81 Right Negative 32 -80.70 35.37 0.17 0.41 -0.58 0.81 Left Neutral 32 -6.25 34.60 -0.07 0.41 1.60 0.81 Middle Neutral 32 10.05 33.55 0.26 0.41 -0.40 0.81 Right Neutral 32 3.72 30.61 -0.27 0.41 -0.12 0.81 Left Positive 32 79.55 35.44 0.27 0.41 -0.87 0.81 Middle Positive 32 80.63 40.07 -0.26 0.41 -0.41 0.81 Right Positive 32 77.55 39.44 -0.27 0.41 -0.28 0.81

Differences Between Upper-Lower and Right-Left Conditions

A paired samples t-test was performed on both the full and abbreviated datasets to examine whether experimental condition (Upper-Lower versus Right-Left) contributed to differences in valence ratings across pictures and valence categories. Averages of all picture ratings, and for all negative, neutral, and positive pictures were calculated for each participant and compared across conditions.

Results from the paired samples t-test in the full dataset revealed a non- significant effect of condition across all stimuli, t (31) = -.47, p = .64, r = .08. This effect remained in the abbreviated dataset, t (31) = -.44, p = .66, r = .08. That is, pictures were not rated as overall more positive or negative in one condition versus the other. These findings correspond to non-significant differences in mean valence and arousal for stimuli assigned to each condition, as established prior to the start of data collection

(see Methods for detailed overview of this comparison).

Separate paired samples t-test were thereafter performed for each of the valence categories. Results from these comparisons in the full dataset revealed that positive pictures in the Upper-Lower condition were rated as significantly more positive than positive images in the Right-Left condition t (31) = 3.32, p = .002, r = .51; this relationship remained in the abbreviated dataset, t (31) = 3.47, p = .002, r = .53.

However, exploration of differences between items in each condition based on normative IAPS data established that positive images in the Upper-Lower condition were considered more positive overall than those presented in the Right-Left condition prior to the start of data collection, F (1, 22) = 5.91, p < .05, obviating direct conclusions from this finding.

A separate paired samples t-test revealed a significant difference between negative images rated across conditions in both the full dataset, t (31) = -3.07, p = .004, r = .48, and the abbreviated dataset, t (31) = -3.06, p = .004, r = .48, such that negative images in the Upper-Lower condition were rated as significantly more negative (M = -

82.92, SE = 3.25) than negative images in the Right-Left condition (M = -69.72, SE =

3.38). Similarly, when averages were compared in the abbreviated dataset, negative pictures in the Upper-Lower condition were rated as more negative (M = -82.75, SE =

4.76) compared to negative pictures in the Right-Left condition (M = -71.82, SE = 4.88).

This could not be accounted for by a significant difference in mean IAPS valence ratings, as it was established these were not significantly different during initial condition assignment, F (1, 22) = .080, p > .05. There was not a significant difference between neutral pictures rated between conditions in either the full dataset, t (31) = -1.51, p =

.14, r = .26 or abbreviated dataset, t (31) = -1.69, p = .10, r = .29.

There was a significant difference in ratings for pictures presented in eccentric space in the Upper-Lower condition versus in the Right-Left condition as examined in the full dataset, t (31) = 2.87, p = .007, r = .46 such that pictures presented in eccentric space in the Upper-Lower condition (M = 8.98, SE = 2.92) were rated more positively compared to pictures presented in eccentric space in the Right-Left condition (M = 1.09,

SE = 3.18). However, this difference was lost in the abbreviated dataset, t (31) = 1.39, p

= .17, r = .24. A significant difference was found between the pictures evaluated in middle space in the Upper-Lower condition versus the Right-Left condition as assessed in both the full dataset, t (31) = -2.88, p = .007, r = .46, and abbreviated dataset, t (31) =

-3.00, p = .005, r = .47. These data revealed that pictures in middle space in the Upper-

Lower condition (M = -3.07, SE = 3.17) were rated as more negative compared to pictures that were presented in middle space in the Right-Left condition (M = 7.33, SE =

3.17). The same relationship appeared in the abbreviated dataset (Upper-Lower middle space trials: M = -2.83, SE = 2.67; Right-Left middle space trials: M = 7.56, SE = 3.06).

Analyses for Specific Aim 1: Influence of Spatial Attention on the Perception of Emotions

Upper-Lower Condition

Effect of valence category

To ensure validity of the valence categories designed to elicit positive, neutral, and negative emotional ratings, the main effect of valence was first examined within the

Repeated measures ANOVA. Mauchley’s test revealed that the assumption of sphericity had been violated for the main effect of valence in both the full, uncorrected dataset, 휒2

(2) = 12.48, p = .002 as well as the abbreviated dataset, 휒2 (2) = 12.82, p = .002, marking unequal variances across participants in the differences between positive, neutral, and negative picture ratings. Degrees of freedom were therefore adjusted using the Greenhouse-Geisser estimates of sphericity (ɛ = .741 and .737) for subsequent interpretation.

Application of the Greenhouse-Geisser correction in the full dataset revealed a significant main effect of valence category on participant ratings, F (1.48, 44.45) =

258.84, p = .000, r = .90. This remained significant after correction in the dataset with incorrectly probed items removed, F (1.47, 44.21) = 260.69, p = .000, r = .90.

Follow-up contrasts revealed for both datasets that, as expected, pictures categorized as positive during the experimental design (M = 92.80, SE = 6.21) were rated more positively than those categorized as neutral (M = -3.73, SE = 4.59), F (1, 30)

= 156.96, p = .000, r = .84. Also as predicted, pictures categorized as negative (M = -

82.92, SE = 4.63) were rated more negatively than those categorized as neutral, F (1,

30) = 213.09, p = .000, r = .88. This pattern was similarly seen in the abbreviated dataset for positive versus neutral pictures, F (1, 30) = 160.60, p = .000, r = .84, and for negative versus neutral pictures, F (1, 30) = 212.92, p = .000, r = .88.

These results validated the original categories used to designate pictures as fundamentally positive, neutral, or negative in the Upper-Lower condition. Likewise, these valence categories were maintained for purposes of subsequent analyses (e.g., examining the influence of space within each valence category).

Effect of spatial location

Eccentric (upper and lower) versus middle space: In order to first determine if the manipulation of space had an overall effect on emotional ratings, a paired samples t-test was performed comparing the average ratings for pictures presented in eccentric space (upper and lower space, combined) to pictures presented in middle space.

Results of the paired samples t-test revealed a significant difference between ratings for pictures in eccentric and middle space in the full, uncorrected dataset, t (31) = 4.37, p <

.001, r = .62. Overall, independent of the valence of these pictures, pictures in eccentric space (M = 8.98, SE = 2.92) were rated as more positive than pictures presented in middle space (M = -3.07, SE = 3.17). The same significant difference and direction of observed means across valence was detected in the abbreviated dataset, t (31) = 2.48, p = .02, r = .41. These data are presented for reference in Figure 5-1.

Figure 5-1. Emotional ratings for positive, neutral, and negative pictures evaluated when presented in Lower, Middle, and Upper Space in the Upper-Lower condition. Standard error bars are superimposed.

Comparisons across upper, middle, and lower space: Upon examining the main effect of spatial location across all three spaces, Mauchley’s test revealed that the assumption of sphericity had been violated for the main effect of space for both the full dataset, 휒2 (2) = 8.15, p = .017 and the abbreviated dataset, 휒2 (2) = 8.81, p = .012, marking unequal variances across ratings for pictures presented in upper, middle, and lower space. Degrees of freedom were again adjusted using the Greenhouse-Geisser estimate of sphericity (ɛ = .792 and .803). Application of the Greenhouse-Geisser correction in the Repeated measures ANOVA revealed a significant effect of space for both the uncorrected dataset, F (1.61, 48.19) = 4.65, p = .013, r = .13, and abbreviated dataset, F (1.59, 47.55) = 5.04, p = .010, r = .14. To determine which of the three spaces might be contributing to the significant main effect observed, three a priori,

paired samples t-test comparisons were performed between means for lower and middle, upper and middle, and lower and upper space for both the uncorrected and abbreviated datasets.

In the full dataset, only a significant difference between lower space and middle space was detected, t (31) = 2.72, p = .01, r = .44. In accordance with the alternative prediction, pictures in lower space (M = 8.01, SE = 4.01), independent of their valence, were rated as being significantly more positive than pictures presented in middle space

(M = -3.07, SE = 3.17). This difference remained statistically significant and in the same direction when incorrectly probed data were removed from the dataset, t (31) = 2.61, p =

.014, r = .42. A significant difference was not found between pictures rated in middle versus upper space in either the full dataset, t (31) = -1.63, p = .11, r = .28 or abbreviated dataset, t (31) = 1.29, p = .21, r = .22. Similarly, a significant difference was not found between pictures rated in lower versus upper space in either the full dataset, t

(31) = 1.69, p = .10, r = .29 or abbreviated dataset, t (31) = 1.84, p = .08, r = .31. Thus, only one component of the alternative prediction (more positive ratings in lower relative to middle space) was supported by these results.

The alternative prediction also stated that more positive ratings in lower space might be observed predominantly for negative stimuli due to stronger connections of the ventral relative to dorsal stream with the amygdala. To explore whether both components of the alternative prediction might be supported (i.e., that negative pictures in lower space would be rated as more positive and negative pictures in upper space would be rated as more negative), two additional, a priori, paired samples t-test comparisons were conducted comparing negative pictures alone. These comparisons

evaluated the mean differences for negative pictures rated in lower versus middle, as well as upper versus middle space. Results of these comparisons in the full, uncorrected dataset revealed that negative pictures in lower space (M = -71.84, SE =

6.36) and negative pictures in upper space (M = -82.46, SE = 5.68) were both rated as less negative than negative pictures in middle space (M = -94.47, SE = 6.00), (lower vs. middle space: t (31) = 3.60, p = .001, r = .54; upper vs. middle space: t (31) = 2.74, p =

.01, r = .44). There was not a significant difference between pictures in lower versus upper space, t (31) = 1.28, p = .21, r = .22. Parallel findings were obtained in the corrected dataset with incorrectly probed items removed (lower vs. middle space: t (31)

= 3.54, p = .001, r = .54; upper vs. middle space: t (31) = 2.69, p = .011, r = .44; lower space vs. upper space: t (31) = 1.27, p = .22, r = .22). Thus, while the difference for pictures in lower space agreed with the alternative prediction, more positive ratings for negative pictures in upper space opposed the alternative prediction, though this was observed for only the negative stimuli.

Interaction effect (valence x space)

Mauchley’s test revealed that the assumption of sphericity had been violated for the main interaction between space and valence for both the full, uncorrected dataset,

휒2 (9) = 23.96, p = .004 and the abbreviated dataset with incorrectly probed items removed, 휒2 (9) = 24.45, p = .004. Following Greenhouse-Geisser correction, a significant interaction effect was not found between valence and space either for the full dataset, F (2.79, 83.78) = 2.04, p = .12, r = .06, or the abbreviated dataset, F (2.79,

83.66) = 1.97, p = .103, r = .06. The relationship between valence and space is depicted visually in Figure 5-1 based on means and standard error bars for the abbreviated dataset. These data suggest that while negative, neutral, and positive pictures were 94

rated differently, and lower space contributed to more positive ratings overall, the influence of space did not differ significantly across the three valence categories.

Summary

These data reveal that participants rated negative and positive pictures in the

Upper-Lower condition as more negative and positive than neutral pictures, respectively. Overall, pictures presented in eccentric, or non-central (upper and lower) space were rated as more positive than items presented in middle space. When the effect of space was considered separately for lower and upper space, pictures presented in lower space were rated as significantly more positive than pictures presented in middle space. Though a significant interaction between valence and space was not found, there was an effect of space when it was considered specifically for negative stimuli. That is, negative pictures presented in lower and upper space were both rated as more positive than negative pictures presented in middle space, consistent with the original finding of more positive ratings in eccentric space.

Right-Left Condition

Effect of valence category

Once again, to ensure validity of the valence categories used to elicit positive, neutral, and negative emotional ratings in the Right-Left condition, the main effect of valence was first examined within the Repeated measures ANOVA. Mauchley’s test revealed that the assumption of sphericity had been violated for the main effect of valence in the Right-Left condition for both the full dataset, 휒2 (2) = 14.36, p = .001, and abbreviated dataset, 휒2 (2) = 12.08, p = .002. Degrees of freedom were adjusted using the Greenhouse-Geisser estimate of sphericity for both sets of data (ɛ = .746 and .719).

Application of the Greenhouse-Geisser correction revealed a significant main effect of

valence category on participant ratings for the full dataset, F (1.44, 43.15) = 194.54, p <

.001, r =.87. As predicted once again, follow-up contrasts revealed that pictures categorized as positive (M = 79.54, SE = 6.23) during the experimental design were rated more positively than those categorized as neutral (M = 2.03, SE = 4.20), F (1, 30)

= 106.06, p < .001, r = .78. Pictures categorized as negative (M = -72.07, SE = 4.94) were rated more negatively than those categorized as neutral, F (1, 30) = 193.36, p =

.000, r = .87. This significant main effect was maintained for the abbreviated dataset, F

(1.49, 44.75) = 191.75, p = .000, r =.87, in the same predicted directions across all three valence categories.

Effect of spatial location

Eccentric (right and left) versus middle space: A paired samples t-test was performed to determine if the manipulation of space along the horizontal plane had an effect on emotional ratings for the Right-Left condition. Results of the paired samples t- test revealed a significant difference between pictures in eccentric (right and left space, combined) and middle space for the full dataset, t (31) = 2.52, p = .02, r = .41. Overall, pictures in eccentric space (M = 1.09, SE = 3.18) were rated as being significantly less positive than pictures presented in middle space (M = 7.33, SE = 2.87). This significant difference was maintained for the abbreviated dataset, t (31) = -2.94, p = .006, r = .47.

These data are represented in Figure 5-2.

Figure 5-2. Emotional ratings for positive, neutral, and negative pictures evaluated when presented in Left, Middle, and Right Space in the Right-Left condition. Standard error bars are superimposed.

Right versus middle space and left versus middle space: Mauchley’s test revealed that the assumption of sphericity was upheld for the main effect of space

(across left, middle, and right space) in the Right-Left condition for the full dataset, 휒2

(2) = 1.22, p > .05. The uncorrected, Repeated measures test of within-subjects effects however, did not reveal a significant main effect of space on participant ratings, F (2,

60) = 2.82, p = .067, r = .09. When the abbreviated dataset was considered upon the removal of items that were incorrectly probed, the assumption of sphericity was again upheld for the main effect of space, 휒2 (2) = 1.36, p > .05. In the abbreviated dataset, the uncorrected, Repeated measures test of within-subjects effects did reveal a significant main effect of space on participant ratings, F (2, 60) = 3.56, p = .035, r = .11.

Three a priori, paired samples t-test comparisons were conducted between means for left and middle, right and middle, and left and right space in both the full dataset and the

abbreviated dataset to explore this discrepancy in findings based on withdrawn items.

Following these comparisons in the full dataset, and independent of the valence of pictures presented, it was found that pictures in right space (M = .54, SE = 3.56) were rated as being significantly less positive than pictures presented in middle space (M =

7.33, SE = 2.87), t (31) = -2.03, p = .037, r = .34. A significant difference in ratings was not found between pictures presented in left space (M = 1.64, SE = 2.87) and middle space, t (31) = -2.18, p = .051, r = .36 or left and right space, t (31) = .34, p = .74, r =

.06. Parallel findings were found for the abbreviated dataset – that is, only a significant difference between pictures in right and middle space was detected with paired samples t-test comparisons.

It is possible that an effect was not seen for pictures presented in the left hemifield in the expected direction in either dataset because differences across valence categories may have overshadowed valence-specific effects. In other words, it is possible that negative pictures (due to right hemisphere specialization for processing negative information) may have been rated as more negative in left space (which is processed by the right hemisphere) and more positive in right space (which is processed by the left hemisphere) whereas this effect may not have been observed for neutral or positive pictures. When the effect of space was considered specifically for negative stimuli in the full dataset, it was found that negative pictures presented in right space (M = -80.94, SE = 6.33) were rated as significantly more negative than negative pictures presented in middle space (M = -67.10, SE = 5.35), t (31) = -2.33, p = .026, r =

.39. Once again, as found when data were collapsed across valence categories, a significant difference was not seen for negative pictures presented in left space (M = -

68.15, SE = 6.44) relative to middle space, t (31) = -.204, p = .84, r = .04, or right relative to left space, t (31) = -1.76, p = .09, r = .30. This same pattern was observed for the abbreviated dataset, with negative pictures in right space being rated as more negative than negative pictures in middle space. Thus, only negative pictures presented in right space were rated as being significantly more negative than negative pictures presented in middle space. This finding conflicted with both original predictions.

Interaction effect (valence x space)

Mauchley’s test revealed that the assumption of sphericity was violated for the interaction effect between valence and space in the Right-Left condition for both the full dataset, 휒2 (9) = 20.34, p = .016, and abbreviated dataset, 휒2 (9) = 17.44, p = .043.

Following Greenhouse-Geisser correction, the Repeated measures ANOVA revealed that there was a non-significant interaction between space and valence for the full dataset, F (3.06, 91.77) = 2.30, p = .08, r = .071, and the abbreviated dataset, F (3.17,

95.07) = 2.11, p = .101, r = .066. Even in the absence of Greenhouse-Geisser correction, the interaction was not significant for either dataset. This relationship is shown for means obtained from the abbreviated dataset in Figure 5-2.

Summary

In sum, participants rated negative and positive pictures as more negative and positive than neutral pictures, respectively, in the Right-Left condition. Pictures presented in eccentric (right or left space) were both rated as significantly more negative compared to pictures presented in middle space. When examined across all three spaces (right, middle, and left), only the difference between right and middle space remained significant, with pictures presented in right space rated as more negative than middle space. Similarly, when examined for negative stimuli alone, only

the difference between ratings of negative pictures in right versus middle space was significant.

Analyses for Specific Aim 2: Influence of Emotion on Attention or Intention

Upper-Lower Condition

Effect of label position: To determine the effect of emotional perception on spatial attention or intention (as reflected in ratings of emotional valence), label space

(positive label at the right or left side of the line in the Upper-Lower condition) was examined as a between-subjects factor within the Repeated measures ANOVA. This between-subjects factor was added to determine whether negative and positive pictures might lead to a rightward or leftward direction bias (i.e., in responding closer to the right versus the left end of the line). It was initially predicted that emotional processing of positive and negative stimuli might lead to greater left versus right hemisphere engagement, and this might lead to a bias toward one or the other end of the horizontal valence line. If an action-intention bias were elicited by specific emotional ratings, we might expect both positive and negative ratings to be artificially “stronger” when the positive label was on one side of the line versus the other.

Valence by label position interaction: For the valence by label position interaction, a significant interaction was initially seen between valence by label position in the full dataset, F (2, 60) = 3.46, p = .038, r = .10. However, this result disappeared following Greenhouse-Geisser correction for violation of sphericity, F (1.48, 44.45) =

3.46, p = .053, r = .10. A similar, significant interaction was initially seen in the abbreviated dataset which disappeared with correction for sphericity. When this interaction was considered within the alternate Multivariate Analysis of Variance approach, which does not assume sphericity as a necessary condition, this interaction 100

was still not significant in either the full dataset, F (2, 29) = 2.43, p = .11, or the abbreviated dataset, F (2, 29) = 2.46, p = .10.

Despite loss of statistical significance with correction, a trend appeared in the originally predicted direction in both datasets – that is, negative pictures were rated as more negative and positive pictures were rated as more positive when the positive label appeared on the left side of the horizontal valence line, a pattern which was not predicted by either the original or alternative hypotheses. This relationship is depicted for the dataset with incorrectly probed items withdrawn in Figure 5-3.

For the space by label position interaction, Greenhouse-Geisser correction was applied for a violations of sphericity for the effect of space in the full dataset, 휒2 (2) =

8.15, p = .017 and the abbreviated dataset, 휒2 (2) = 8.81, p = .012. Following

Greenhouse-Geisser correction, no significant differences were revealed for this interaction in either the full dataset, F (1.61, 48.19) = .50, p = .57, r = .09 or abbreviated dataset, F (1.59, 47.55) = .507, p = .61, r = .02. This finding suggested that positioning in upper versus lower space did not systematically engage spatial biases toward the left or right side of the horizontal valence line.

Main effect of label position: When examined as a between-subjects factor in the Repeated measures ANOVA, the main effect of label space was not significant for the Upper-Lower condition for either the full dataset, F (1, 30) = 1.75, p = .20, r = .06, or the abbreviated dataset, F (1, 30) = 1.68, p = .21, r = .05. In effect, pictures overall were not rated as significantly more positive or negative based on the orientation of the positive label (whether it appeared on the left or right side) along the horizontal valence line. Thus, neither a systematic leftward or rightward bias was observed across different

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valence category pictures. This result suggested that pseudoneglect did not significantly contribute to a spatial bias observed in a specific direction across all pictures rated.

Likewise, when this was decomposed for neutral versus emotional (positive and negative) pictures, a main effect of label position was not found for either emotional F

(1, 30) = 1.81, p = .19, r = .06 or non-emotional pictures F (1, 30) = .51, p = .48, r = .02.

This result was not altered in the abbreviated dataset. These data are presented for reference in Figure 5-3.

Figure 5-3. Emotional ratings for positive, neutral, and negative pictures evaluated with the “positive” label positioned on the right side of the horizontal valence line, and with the “positive” label on the left side of the line in the Upper-Lower condition. Standard error bars are superimposed.

Right-Left Condition

Effect of label position: Label space (positive label at the top or bottom of the vertical valence line) was once again considered as a between-subjects factor in the

Repeated measures ANOVA for the Right-Left condition. This was examined based on

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the proposal that positive evaluations might facilitate heightened engagement of the ventral processing stream, thereby directing attention further upward, and negative evaluations would facilitate heightened engagement of the dorsal processing stream, directing attention downward. Thus, positive pictures should be rated as more positive when the positive label appears at the top of the vertical valence line whereas negative pictures should be rated as more negative when the negative label appears at the bottom.

Valence by label position interaction: Following Greenhouse-Geisser correction for a violation of sphericity for the main effect of valence, a significant interaction was not found between valence and label position for the full dataset, F

(1.44, 43.15) = .24, p = .79, r = .008, or space and label position, F (1.92, 57.62) = .88, p = .42, r = .03. This effect was not altered with the abbreviated dataset. Thus, differences in emotional processing related to valence and spatial location of the pictures did not alter the direction of spatial action-intention biases in the directions originally predicted.

Main effect of label position: There was a significant effect of label position in the Right-Left condition, F (1, 30) = 4.66, p = .039, r = .13 such that individuals who viewed the positive label at the top of the vertical valence line rated all pictures, regardless of valence as more positive compared to individuals who viewed the positive label at the bottom of the vertical valence line. That is, both positive and negative (as well as neutral pictures) were rated as more positive when the positive label appeared at the top (versus the bottom) of the vertical valence line. This finding was in line with the alternative prediction, which predicted a systematic upward bias when the positive

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label was positioned at the top of the line, irrespective of the valence of stimuli being rated. This relationship remained when considered within the abbreviated dataset. The relationship between label position and the valence of pictures presented is shown in

Figure 5-4.

Figure 5-4. Emotional ratings for positive, neutral, and negative pictures evaluated with the “positive” label positioned at the top of the vertical valence line, and with the “positive” label at the bottom of the line in the Right-Left condition. Standard error bars are superimposed.

To explore whether the systematic bias might be related to the task of emotional processing versus a systematic upward spatial bias, the main effect of label position was decomposed for emotional relative to non-emotional stimuli. Results of this comparison in the full dataset revealed a main effect of label position for neutral stimuli

F (1, 30) = 4.22, p = .049, r = .12 but not for positive and negative stimuli, F (1, 30) =

2.27, p = .14, r = .07. Although the main effect of label position remained non-significant for emotional stimuli in the abbreviated dataset, the significant effect for neutral stimuli

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was no longer significant once incorrectly probed items were withdrawn, F (1, 30) =

3.68, p = .07, r = .11. These data indicate that the effect was apparent across all stimuli in both the full and abbreviated datasets, but strongest for non-emotional relative to emotional pictures when considered for the full dataset alone.

Summary

In the Upper-Lower condition, it was predicted that negative pictures would stimulate greater right hemisphere engagement and heightened attention (and intention) toward left hemispace whereas positive pictures would stimulate greater left hemisphere engagement and heightened attention (and intention) toward right hemispace. Thus, negative pictures would be rated as more negative and positive pictures would be rated as more positive when the positive label is on the right end of the line. While an interaction between valence and label position was not significant, a trend instead in the opposite direction was observed – that is, positive pictures were rated as more positive and negative pictures were rated as more negative when the positive label appeared at the left end of the horizontal valence line. There was a significant main effect of label position (in the absence of an interaction related to space or valence) in the Right-Left condition. This suggested a systematic upward bias during picture ratings along the vertical valence line that was unrelated to valence or space. It was further observed that while this effect was apparent across all pictures, regardless of valence, it was strongest for neutral (non-emotional) stimuli.

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Analyses for Specific Aim 3: Influence of Emotion on Physiological Responding

As mentioned previously, errors in administration of the startle eyeblink paradigm precluded valid analysis of this portion of the experiment. Therefore, a full analysis of the effect of probe stimulation on the amplitude of startle was not conducted.

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CHAPTER 6 DISCUSSION

Specific Aim 1: Influence of Spatial Attention on the Perception of Emotions

Specific Aim 1 predicted that pictures presented in upper space would be rated as more positive than pictures presented in middle space and pictures presented in lower space would be rated as more negative than pictures in middle space.

Alternatively, it was proposed that due to more extensive connections with the amygdala (which specializes in processing negative stimuli), the ventral stream may assign greater negative value to pictures presented in upper space whereas more positive value would be assigned to pictures presented in lower space (to the dorsal stream). It was further predicted that this alternative relationship might be specific for negative stimuli in particular. In contrast to both of these predictions, pictures in lower space were rated as more positive than those in middle space, and negative pictures in upper and lower parts of space were both rated as more positive than pictures presented in middle space.

It is possible that neither the original nor alternative prediction was fully supported due to loss of strength for comparisons across space based on the study design. Importantly, pictures assigned to upper/lower (and left/right) space were counterbalanced during study design to measure the effects of these opposing positions against middle space as a neutral comparison. Pictures in these opposing spaces were not additionally counterbalanced however, with pictures assigned to middle space.

Thus, it cannot be definitively stated that pictures presented in upper and lower space were perceived as more positive than pictures in middle space solely due to spatial location. Rather, differences observed for eccentric relative to middle space could be

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accounted for by differences inherent in the pictures themselves. To address this possibility in future studies, it would be necessary to recruit a larger sample of participants such that additional counterbalancing could ensure that all three sets of

“critical” pictures could be viewed by a separate group of individuals in upper/right, middle, and lower/left space. Differences relative to middle space would then support the influence of spatial attention toward upper and right versus lower and left parts of space.

It is also possible that a dichotomous model of ventral relative to dorsal stream engagement was not supported due to heightened engagement of one stream over the other based on the nature of the emotional rating task. Since ratings of negative pictures in particular were both biased toward more positive evaluations in both upper and lower space, it is possible that the novelty of responding to stimuli in a different portion of space in the vertical plane contributed to less negative ratings overall. As highlighted earlier, the dorsal stream is responsible for calculating approximate distances of objects for target approximation during reaching and grasping movements

(Goodale, et al., 2004; Milner & Goodale, 1995). Since the primary mode of responding during the emotional pictures task involved reaching toward a visual stimulus in space

(the valence line), it might be expected that the very act of providing an emotional rating would engage the dorsal stream to a greater extent. In the current study, attention was consistently directed towards a single crosshair in middle space between trials, which required little shifting of attention toward different parts of space. This was done to ensure that any differences observed for upper, lower, or right and left parts of space would not be influenced by the preceding trial – for instance, if attention had just been

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directed upward. However as shown with the current findings, it is possible that this also contributed to lesser engagement for middle space trials, and subsequently, more negative ratings when pictures were presented in middle compared to upper and lower space. Thus, more positive ratings may have been made for pictures when attention was shifted toward both upper and lower space (which may be processed by the dorsal stream due to more marked shifts in visual engagement and reaching requirements).

Since the dorsal stream is likely specialized for processing information in lower space

(Verfaellie, et al., 1990), pictures in lower space may have been processed to an even greater extent by the dorsal stream, strengthening this effect in lower space when stimuli were collapsed across valence categories. This possibility reveals the importance of considering how subjective emotional ratings are measured experimentally, as specialization for spatial processing might interact with methods of emotional reporting.

Unfortunately, while preferential processing may be inferred by reaction time and categorization tasks, preferential processing of emotional pictures does not necessarily translate to more positive subjective ratings. Along these lines, if reaching in different, or novel parts of space were the sole explanation for more positive judgments, we would expect the same outcome in the Right-Left condition – which was clearly not supported.

That is, pictures in both left and right parts of space were rated as more negative compared to pictures in middle space – although this difference was only significant in right space. This pattern was observed for negative stimuli in particular and when collapsed across valence categories.

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For the Right-Left condition in particular, it is possible that presentation of stimuli in left hemispace did not elicit significant differences in rating emotional stimuli because of the role of the parietal lobes in regulating emotional arousal. It has been shown that each hemisphere attends to contralateral hemispace (Kinsbourne, 1970). Thus, presentation of pictures in left space would yield heightened right parietal lobe activation. Additionally, it has been shown that right parietal activation might be more involved in regulating emotional arousal. Thus, it has been found that upon engagement of attention toward left hemispace, participants demonstrate less marked negative mood states after viewing a sad mood induction film compared to counterparts whose attention was initially focused toward right parts of space (Compton, 1999). Conversely, left hemisphere parietal areas may not be able to demonstrate the same control over emotional arousal, thereby eliciting stronger, and more negative responses to emotional pictures, and negative pictures in particular, when presented in right hemispace. Thus, more negative ratings for pictures presented in right space are supported by this possibility.

It is also possible that emotional processing is comprised of more than just response to visual information. Thus, manipulation of relative dorsal versus ventral processing stream engagement (presumably via manipulation of spatial attention toward upper and lower parts of space), may not have been sufficient to override an emotional processing system independent of these streams. A recent neuroimaging study found that during processing of both negative and positive IAPS pictures, blood oxygen level dependent (BOLD) signal activation was increased relative to a neutral condition

(viewing a central crosshair) in bilateral prefrontal cortex (PFC), anterior cingulate, and

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temporal lobes (Aldhafeeri, Mackenzie, Kay, Alghamdi, & Sluming, 2012), areas that traverse both dorsal and ventral processing streams. In support of this interpretation,

Meier and Robinson (2004) also found that initial engagement of attention toward upper and lower parts of space did not facilitate evaluations of positive and negative words subsequently presented in middle space. It is certainly possible that subsequent shifting of attention toward middle space in this previous study was sufficient to obviate the role of dorsal versus ventral stream engagement in emotional judgments. However, it may also be that while emotional evaluations can shift attention toward upper or lower portions of space, spatial attention toward upper versus lower space is not sufficient (or necessary) to alter emotional judgment.

Finally, in terms of a more nurture-related account that integrates results from both conditions (versus the neurobiological account of dorsal versus ventral stream engagement), it is possible that the simple behavior of directing attention repeatedly up and down in space may have been more strongly associated with positive, enjoyable experiences whereas the behavior of directing attention to the left and right repeatedly may have been associated with a greater sensation of disagreement. Zajonc and

Markus (1982) posited that preferences are developed not solely through neurobiological predispositions, but rather through tradition, pleasant repeated exposures, and even sensorimotor associations. They argued the approach-avoidance perspective that preferences may even be marked by subtle motor movements, for instance, the way we tend to lean in toward someone we favor while directing our body away from unpleasant individuals. This simple theory was supported in a study by Wells and Petty (1980), who investigated the effects of head shaking and head nodding

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motions on participant preferences for an auditory sample. Seventy-two participants were led to believe they were testing the effectiveness of headphones during various head movements and listened to a radio broadcast while engaged in either head nodding (up and down movements) or head shaking (left-right movements). Wells and

Petty found that individuals engaged in the head nodding condition agreed more with the content of the radio sample than individuals in the head shaking conditions. The authors suggested that these motions activated motor representations associated with either a state of agreement or disagreement and activation of these representations motivated individuals either toward or away from the information being presented. Along these lines, the gesture for ‘yes’ is up and down movements while the gesture for ‘no’ is side-to-side movements. In turn, it is possible that the mere act of looking up and down activated pleasant associations for the participants in the current study, whereas left- right movements activated a state of discord or disagreement, motivating more negative ratings of the emotional pictures shown.

Specific Aim 2: Influence of Spatial Attention on Action-Intention

It was initially predicted that since each hemisphere attends to contralateral space, increased activation in the right or left hemisphere (coincident with evaluations of either negative or positive emotional pictures) should increase attention or action- intention toward the opposing hemisphere. Thus, negative pictures should stimulate right hemisphere engagement and attention, as well as action-intention toward left hemispace whereas positive pictures should stimulate left hemisphere engagement and attention, as well as action-intention toward right hemispace.

Though no longer significant following corrections for violations of sphericity, a trend toward a significant valence by label position interaction was found, however in 112

the opposite direction than expected. These results suggest that the emotional valence of presented pictures may induce differential activation of the right versus left frontal lobes and the contralateral parietal lobe, thereby directing attention toward right versus left hemispace, respectively.

One possible explanation for this finding is based on recent work by Foster, et al.

(2008). According to the action-intention hypothesis posited by Foster and colleagues, in addition to driving opposing approach and avoidance behaviors the anterior and posterior association cortices are also mutually inhibitory. These researchers examined this theory in a study of 138 undergraduate students, who were asked to simply place a collection of emotionally labeled pegs on an axially aligned board, “…in a manner that represents the relationships between the emotions” (p. 129). They found that negative emotionally labeled pegs (e.g., sad, afraid, disgusted) were placed closer toward portions of right, proximal space whereas positive emotion labels (e.g., happy, joyful, surprised) were placed closer to left, distal space. Based on these findings, it was postulated that activation first occurs in the anterior portions of the dominant (left or right) hemisphere, in accordance with valence theory (right = negative; left = positive).

Activation within the anterior portions of the dominant hemisphere would then lead to inhibition of the ipsilateral posterior cortex. Reduced activation of the ipsilateral posterior region would in turn lead to disinhibition (and thus, activation) of the contralateral posterior cortex. Heightened activation of the posterior segment of the non-dominant hemisphere would then result in an overall spatial bias toward the opposing hemispace , ipsilateral to the dominant hemisphere (Foster, et al., 2008). Therefore, viewing stimuli with a positive valence should increase anterior left and posterior right hemisphere

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activation, leading to increased spatial biases toward left hemispace; stimuli with negative valence should induce a spatial bias in the opposite direction (toward right hemispace).

While alternative explanations exist, since this effect was no longer significant following corrections for sphericity violations, sufficient differences in the variances obtained for each of the valence categories may reflect an artifact of study design and power to detect a true, significant effect in the originally expected direction. Violations of sphericity are important to consider in Repeated measures designs because they indicate differences in the population variance across experimental conditions and inflation of the F-ratios obtained. Inflated F-ratios also reveal a greater likelihood of Type

II error, or the possibility of interpreting a result as true when it is in fact false. Therefore, it is possible that the interaction between valence and label position in the Upper-Lower condition was sufficiently weak that it did not survive correction. Conversely, violations of sphericity may be detected more easily in large samples, when N is greater than the number of comparisons, plus 10. Since 16 participants contributed to ratings for each of the label positions, it is possible that sphericity was more easily violated in the current study, reducing power of a significant interaction after correction. Likewise, with an even larger sample size this violation may not have contributed to a substantially different alpha level and the interaction would have remained significant, as expected.

Since a non-significant interaction was found between space and label position for the Upper-Lower condition, it suggests that the position of stimuli in upper, middle, and lower space did not contribute (beyond what might be explained by picture valence alone) to differential engagement of the left and right hemispheres and subsequent

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action-intention biases toward left versus right hemispace. Likewise, it suggests that positioning in upper versus lower space (and presumably, differential engagement of the ventral versus dorsal processing streams, respectively) was not responsible for greater action-intention toward one side of the horizontal valence line versus the other.

Since a main effect for label position was also not found, it suggests that any normal hemispatial biases (e.g., pseudoneglect; Bowers & Heilman, 1980; Jewell &

McCourt, 2000) may have been overshadowed by differential engagement of the right and left hemispheres. Likewise, it is possible that differential engagement of the right and left hemispheres may have resulted from the process of viewing and evaluating both positive and negative emotional stimuli in the Upper-Lower condition. Importantly, the effect of label position was still not significant when pictures were decomposed across emotional and non-emotional stimuli. That is, the process of simply engaging in an emotional decision task did not influence the direction of subsequent spatial biases in a specific direction (toward the left or right).

In the Right-Left condition, the initial postulate stated that negative emotions might be preferentially processed by the dorsal stream and positive emotions might be preferentially processed by the ventral stream. Since the dorsal stream attends to lower space and the ventral stream attends to upper space, it would then be presumed that negative stimuli would stimulate the dorsal stream to a greater extent, thereby directing attention toward lower portions of space. Positive stimuli in contrast would be expected to stimulate the ventral stream to a greater extent, thereby directing attention toward upper portions of space. In terms of action-intention biases, it would therefore be expected that positive stimuli would be rated most positive and negative stimuli would

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be rated most negative when the positive label is located at the top of the vertical valence line. This first prediction would result in a significant interaction between valence and label position. Surprisingly, this expected interaction was not found.

In accordance with the alternative prediction, there was a significant main effect of label position in the Right-Left condition such that responses were consistently biased toward upper portions of the line. In effect, both negative and positive stimuli were rated as more positive (and less negative) when the positive label appeared at the top versus the bottom of the vertical valence line.

As stated in the alternative prediction, it is possible that – like the right hemisphere’s dominance for emotional processing in general – the ventral stream might also be dominant for emotional processing, regardless of the valence of stimuli being perceived. Due to strong, reciprocal connections of the amygdala within the ventral stream, it is possible that the act of perceiving and rating emotional pictures engaged the ventral stream to a greater extent, even across right, middle, and left positions. This in turn, would have directed subsequent attention upward, resulting in an action- intention bias toward the top of the line, an outcome which was indeed observed.

Although this postulate is certainly possible, the consistent, upward bias observed might also be accounted for by altitudinal pseudoneglect as previously described (Suavansri, et al., 2012). Likewise, when the data were decomposed across non-emotional and emotional stimuli, the effect only remained significant for non- emotional stimuli. This finding suggests that rather than a product of emotional processing by the ventral stream, differential engagement of the ventral versus dorsal

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streams due to emotional processing may have been overshadowed by the strength of normal upward spatial biases.

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CHAPTER 7 CONCLUSIONS

Summary

Data from this study revealed that the dorsal stream may be more important for assigning positive value to stimuli presented in lower space whereas the left hemisphere may permit more negative evaluations of emotional stimuli presented in right space. Further it appears that while the ventral stream may have supported vertical action-intention biases toward upper space, independent of the valence of pictures viewed, horizontal action-intention biases might be driven more by the emotional quality of the pictures assessed. While several alternative explanations for these findings have been discussed, the study limitations that may have confounded these results are further discussed below.

Study Limitations

Among the clearest study limitations is the lack of control over startle probe administration. Since this was not uniformly delivered as originally planned across counterbalanced factors (i.e., space, and valence/arousal of pictures) it could not be systematically explored in the Repeated measures ANOVA. Moreover, it is possible that this contributed to differences across participants – i.e. additional exposure to probe stimulation may have influenced ratings as more positive or negative in certain participants. While attempts were made to correct for the latter confound by performing analyses with both the full dataset and abbreviated dataset with incorrectly probed items removed, it cannot be concluded that this did not somehow influence the results.

As mentioned earlier, pictures assigned to upper/lower (and left/right) space were counterbalanced during study design though these were not additionally

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counterbalanced with pictures assigned to middle space. Non-significant differences between upper and lower, as well as left and right parts of space suggest that these opposing locations did not contribute in substantially different ways to emotional ratings.

However, lack of counterbalancing against pictures in middle space limits conclusions regarding the effect of eccentric relative to middle space on emotional processing.

Future work may recruit additional participants and ensure that the same sets of pictures are represented at least once in each of the three spaces of interest.

It is also possible that the pictures chosen for emotional ratings were also too dependent on personal preferences and less capable of eliciting consistent valence ratings. Anecdotally, certain images (children, roller coasters) elicited extreme differences in responding across participants – eliciting more positive or more negative ratings for participants based on past experience and preferences. The Post-test debriefing form revealed the individual factors which likely contributed to variance across the three valence categories. For instance, one participant stated, “I enjoyed water, fire, and action; apathetic to children,” while another noted, “I had to view it as if I wasn't a firefighter because ‘your worst day is our best day’ [referring to the excitement involved while on the job while viewing scenes others might consider disastrous].”

Future investigations may take this possibility into account during stimulus selection, and it may be important to choose stimuli that elicit smaller standard deviations across the normative sample, with minimal differences between both men and women. While differences across selected valence categories were validated in both conditions via a significant main effect of valence category, ratings in each of the valence categories still ranged across both extreme ends of the valence lines in both conditions. Thus, it

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remains possible that these differences across the sample contributed to a loss of detectable difference across space.

It is possible as well that the subtle differences related to space across positive, neutral, and negative pictures were obscured by consistent markings of these stimuli at extreme points along the line. Anecdotally once again, it was noted that despite directions to make graded ratings of how positive and negative each of the stimuli were, participants often marked all positive stimuli toward the far end of the line nearest the positive label whereas all negative stimuli were often marked closest to the far end nearest the negative label. This may have systematically eliminated the subtle differences expected across positive, neutral, and negative stimuli, which may have been elucidated with the addition of startle stimulation. Thus, more explicit directions may be useful in future studies which more strongly encourage use of the entire line to compare pictures against specific anchors (e.g. death of a parent versus successful graduation from a doctoral program) and against each other.

Implications for Future Research

Future work might examine startle eyeblink, as initially proposed in this study, as an objective, non-invasive measure of emotional response. This measure may serve to dissociate different components of amygdala involvement in processing negative emotional pictures in particular. Additionally, it may be useful to incorporate systematic measures of both vertical and horizontal line bisection in addition to vertical and horizontal lines for emotional rating. These may be useful in evaluating the spatial biases induced by emotional stimuli and the enhancing effect of initial spatial orienting on biases toward different parts of space (e.g., greater bias toward right space following an initial orienting upward). 120

Conclusions

While several factors limit conclusive findings and directional interpretations of the data, results from Specific Aim #1 reveal that spatial orienting may influence the perceived valence of emotional stimuli. Further, it appears that this may occur in different ways along the vertical versus horizontal planes. Since many studies utilize spatial means of assessing emotional perception (e.g., the Self-Assessment Manikin rating system for evaluating valence and arousal; Lang, et al., 1999), this study suggests that both spatial orienting and emotional processing may influence the action- intention biases involved in reporting these emotional judgments. Thus, future studies may consider the means by which emotional perception is both elicited and assessed.

Data from Specific Aim #2 suggests that action-intention biases along the horizontal plane may interact with valence due to prominent hemispheric asymmetries for emotional processing. Action-intention biases in the vertical plane in contrast, may be more strongly mediated by the ventral visual processing stream in general, which may influence responding upward independent of concurrent emotional processes.

Together, data from the current investigation contribute to a growing body of literature regarding the overlapping influences of emotion and spatial processing.

Ongoing work may continue to explore the extent of this overlap, as well as how manipulating one system might predictably alter responses in the other.

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APPENDIX A TELEPHONE SCREENING

Screening Date: ______Time Started: ______Time Ended: ______

Screener’s Name: ______(Print) First Last

Participant’s Name: ______(Print) First Last

Contact # (record this last, only if eligible): ______

PART 1 – Welcome and Study Overview

Thank you so much for your interest in our research study! First, may I ask how you learned about this project?

Participant response: ______

Excellent. Before I provide an overview of the study, I would like to ask you for some background information to help us determine if you qualify.

Participant Gender: ______

Participant’s Age: Younger Group (21-40): ______Older Group (60-80): ______

Handedness: ______(Must be right-handed to qualify)

Education: ______(Must have at least 12 years of education to qualify)

Study Group (Check one): Young Control Older Control Young, Left Stroke Old, Left Stroke Young, Right Stroke Old, Right Stroke

If participant does not fall into one of the target groups: Thank you for your inquiry about our study. Unfortunately you do not qualify for the current study based on one or more of these factors. However, may we share your contact information with other researchers in our group who are running studies that you may be eligible for?

No Ok, not a problem. Thank you again for your inquiry, and please keep us in mind if you hear about future studies you might be interested in.

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Yes Wonderful. Thank you for your time, and I hope we can find another study that you might be interested in in the future.

Contact phone number: ______

If participant continues to qualify:

Great. Last two questions before we continue:

Are you a veteran? ____

How would you describe your race or ethnicity? (check one):

____ American Indian/Alaska Native ____ Black/African American ___ Asian ____ Unknown, not reported ____ Native Hawaiian/Pacific Islander ___ Hispanic or Latino ____ White

Great. As you likely already know, this study is conducted at the VA’s Malcolm Randall Medical Center and the McKnight Brain Institute at the University of Florida. The study consists of either one or two visits, depending on your schedule, for approximately 4-5 hours for initial testing and approximately 90 minutes for an MRI. The MRI may be scheduled on the same day or a different day, depending on your availability. Upon completion of the entire study, you will be compensated with $150 via direct deposit for your time and effort.

The name of this study is the Vertical Neglect study and the aim of this study is to learn more about how aging and strokes change people’s ability to be aware of objects around them. More specifically, in this study we will examine people’s attention and their ability to see things down toward the ground and up toward the ceiling as well as on their right and left side. We are also interested in learning if the ability to perceive emotion changes with aging and with stroke. Therefore, we also plan to examine how people perceive different emotional pictures.

You are being asked to volunteer for this research study because either you have had a stroke in the left or right side of your brain or you are a healthy individual who has not had a stroke.

If you qualify and are interested in participating, we will arrange an appointment for you to come in to the Malcom Randall VAMC. At that visit, we will review a special document with you called the Informed Consent Form, which provides details about study involvement. If you agree to participate, we will both sign that form as an agreement, but you can end your participation in the study at any time, and this is not a binding contract.

As part of the study, we would ask you to do a few thinking and memory assessment tasks that are commonly used in thinking and memory research. We will perform

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several tests that examine your ability to perceive things around you and understand the environment, as well as your ability to speak and understand speech, drive, walk, and remember things. Study involvement may also include the additional study of other brain and body changes, including changes in heart rate, perspiration, your startle reaction, and wakefulness. Lastly, if you are eligible, someone who is involved with the research study may take you to the McKnight Brain Institute near Shands Hospital for an MRI scan of the brain. This helps us understand more about how you responded to the tests and how we can help people who have had brain injuries, like stroke. You will have a study coordinator available at all times, to assist with the instructions, and to help you every step of the way.

Does this sound like something you would be interested in?

No Ok, well thank you for your inquiry about our study. May we share your contact information with other researchers in our group who are running studies that you may be eligible for?

No Ok, not a problem. Thank you again for your inquiry, and please keep us in mind if you hear about future studies you might be interested in.

Yes Wonderful. Thank you for your time, and I hope we can find another study that you might be interested in in the future.

Contact phone number: ______

(Answer any other questions and end call)

Yes That’s great! (Move to next prompt)

PART 2 – Screening Introduction Before we can schedule you to participate in this study, we will need to ask for some background information to ensure that you are eligible. If you continue to qualify following this brief phone screening, we can arrange an appointment for additional thinking, memory, and emotional testing that will help us determine if you continue to qualify. If you do not qualify following the entire screening process, you may not be asked to continue with full participation in the study tasks described, or be eligible for compensation. However, you may be able to participate in other ongoing projects.

Does this procedure sound acceptable?

No Ok, well thank you for your inquiry about our study. May we share your contact information with other researchers in our group who are running studies that you may be eligible for? No Ok, not a problem. Thank you again for your inquiry, and please keep us in mind if you hear about future studies you might be interested in.

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Yes Wonderful. Thank you for your time, and I hope we can find another study that you might be interested in in the future.

Contact phone number: ______

(Answer any other questions and end call)

Yes That’s great! (Move to next prompt)

Part 3 – Inclusion and Exclusion Screening

At this point I would like to ask some questions so we can determine if you would be a good candidate for our study. You can comment at any point if you are unsure, or need additional information to answer accurately.

Complete the entire screening questionnaire before ending the call, even if the participant does not qualify based on their early responses.

Have you ever been diagnosed or treated for any of the following?

1. Any type of mood, emotional, or behavioral difficulties, such as sadness, anxiety, obsessive compulsions, anger, delusions or hallucinations? 2. Drug or Alcohol Abuse (i.e., have you ever had problems with these substances or has it ever interfered with daily activities or functioning?) 3. Learning Disability, or trouble in school with subjects like reading, math, or spelling? 4. Neurological dysfunction or injuries like epilepsy, TBIs, concussion, or stroke? (If yes to stroke): Do you have neuroimaging or medical records available to confirm the presence of your stroke? 5. Acute or chronic organ failure such as heart, liver, or kidney? 6. Developmental/birth disorders or complications at birth?

We also want to learn more about any medications you may take. If you have questions about what any of these medications are, I can give you an example and definition to help you understand and answer accurately.

 Benzodiazepines – Used for anxiety, insomnia, & seizures. Ex: Xanax, Valium, & Klonopin  Barbiturates – Used for anxiety, insomnia, & seizures. Ex: Luminal & Phenobarbital  Anticonvulsants – Used for bipolar disorder, mood stabilization, & seizures. Ex: Same as above

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 Antipsychotics – Used for bipolar disorder, schizophrenia, & dementia. Ex: Zyprexa & Seroquel  Amphetamines – Used recreationally & for ADHD & narcolepsy. Ex: Adderall, Dexedrine, & Vyvanse  Dopaminergic Agents – Used recreationally, for LBP, heart & kidney failure. Ex: MDMA & Metedrone  Other Psychotropic Medications – Anxiolytics, Euphoriants, Stimulants, Depressants, & Hallucinogens

Part 4 – Phone Screening Outcome: Ineligible (or) Unsure (or) Eligible-Schedule (Select one option below)

DO NOT INCLUDE IN THE STUDY – If the respondent does not meet the inclusion criteria or definitely meets one of the exclusionary criteria:

Thank you for answering my questions. Your answers are very important to us; however you will not be able to join the study at this time {If the participant inquires about why, explain that you cannot share the exact inclusion/exclusion criteria}.

May we share your contact information with other researchers whose studies you may be eligible for?

No Ok, not a problem. Thank you again for your inquiry, and please keep us in mind if you hear about future studies you might be interested in.

Yes Wonderful. Thank you for your time, and I hope we can find another study that you might be interested in in the future.

Contact phone number: ______

Comments regarding reason(s) for exclusion______

UNSURE about meeting study criteria? – If further clarification is needed from the study team, whether or not the respondent meets one or more of the exclusionary criteria:

Thank you for answering my questions. Your answers are very important to us. According to some of your answers, I need to forward your information to our Primary Investigator or his Study Coordinator for further clarification. Someone from our office will then get back with you as soon as possible.

Comments regarding reason(s) for deferral______

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______After information was reviewed, Respondent was contacted by ______on the _____ day of ______and was informed they were: Excluded Included ______

SCHEDULE - If the respondent meets all of the inclusion criteria and does not meet any of the exclusionary criteria:

Thank you for answering these questions. Your answers are very important to us. According to your answers, you appear to meet our initial criteria for enrolling in the study. Next, we need to schedule an appointment at the VA’s Malcolm Randal Medical Center, in order to complete your eligibility screening and begin your research participation. It will be important on the day of testing to bring your bank information (routing and account number) for purposes of direct deposit payment. (Only if enrolled as participant with stroke): Also, please remember to bring a copy of your neuroimaging results and/or medical records on the day of testing for qualification and enrollment purposes.

APPOINTMENT(S) SCHEDULED ON: ______

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APPENDIX B OVERVIEW OF COUNTERBALANCED FACTORS ACROSS STIMULI

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Figure B-1. Number of stimuli in each counterbalanced category: specifically, trial type (critical or distractor), space (upper, lower, middle, right, and left), valence (negative, neutral, or positive), arousal (high or low normative level), and startle category (probed or not probed). These stimuli comprised the total stimulus set of 120 different IAPS images and were divided, then equated for valence and arousal across space within each condition (Upper-Lower and Right-Left) separately.

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Figure B-2. Example division of critical images across the three primary positions of interest in each condition. Group 1 and 2 represent two different groups of 16 individuals each who viewed a certain stimulus set assignment. Stimulus sets 1 and 2 represent the specific images which were counterbalanced across participant Groups.

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APPENDIX C POST-TEST DEBRIEFING FORM

Post-Test Debriefing Form Subject #: ______Date: ______

Emotional Rating 1. How well do you think you performed on the emotional rating tasks (mark with an X)?

______1 2 3 4 5 6 7 8 9 10 not very accurate very accurate

1. What strategies did you use while rating the emotional images? Did you:

a. Consider your own facial expression (e.g., strength of smile, eyebrow furrowing) while viewing the images?

b. Consider how your body felt (e.g., discomfort, degree of increased heart rate) while viewing the images?

c. Judge the facial expressions of people depicted?

d. Consider what the individuals involved (people or animals) may have experienced?

e. Put yourself in the shoes of individuals (people or animals) involved?

f. Imagine what your emotional state might be in a similar situation?

g. Others?

2. Did you have any hypotheses or expectations as you performed these tasks?

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APPENDIX D ERRORS DURING PROBE ADMINISTRATION

Table D-1. Number and type of errors committed during probe administration for critical trials during each experimental condition Upper-Lower Right-Left Subject ID early late missed accidental # errors early late missed accidental #errors HYC001 0 0 HYC002 0 X 1 HYC003 0 0 HYC004 0 X X 2 HYC005 0 0 HYC006 0 0 HYC007 0 X 1 HYC008 X 1 X 1 HYC009 X X 2 X 1 HYC010 X X 2 0 HYC011 0 0 HYC012 0 X 1 HYC013 0 2X X 3 HYC014 0 0 HYC015 0 0 HYC016 X 1 X 1 HYC017 0 0 HYC018 0 X 1 HYC019 0 X 1 HYC020 0 0 HYC021 X 1 0 HYC022 0 0 HYC023 X 1 2X 2 HYC024 0 X X 2 HYC025 0 0 HYC026 0 X 1 HYC027 X 1 0 HYC028 0 X 1 HYC029 X 1 0 HYC030 X 1 0 HYC031 0 0 HYC032 0 0 Average #errors 0.34 Average #errors 0.59 Total errors 11 Total errors 19

Notes: Early = trigger accidentally pressed prior to image display; Late = trigger pressed after two-second presentation window; Missed = trigger deliberately not pressed during interstimulus interval due to missed presentation window; Accidental = trigger accidentally pressed for an item not assigned to receive startle stimulation.

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Figure D-1. Stimulus characteristics of items probed incorrectly during each experimental condition and withdrawn from analysis

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BIOGRAPHICAL SKETCH

Dana Marie Szeles initiated her doctoral training at the University of Florida in the summer of 2009. She began her research in the Department of Clinical and Health

Psychology, with a particular interest and focus on speech and language disorders. In her early work, she became interested in interdisciplinary work, exploring a unique speech pattern experienced by individuals with post-stroke apraxia of speech.

Alongside colleagues in speech and language pathology, neurology, and neuropsychology, she sought to characterize changes in the quality of speech production before and after language intervention. She received her M.S. from the

University of Florida in the spring of 2011. She continued in the area of stroke research in pursuit of her dissertation, which herein examines the potential mechanisms responsible for both visuospatial and emotional perception in neurologically healthy adults. It is hoped that findings from this investigation might inform future work with individuals who have experienced cognitive changes in these areas. In pursuit of advanced clinical work in the area of acute brain injury, she completed her clinical internship in the Department of Rehabilitation Medicine at The Mount Sinai Hospital, where she performed both neuropsychological assessments and intervention for patients following traumatic brain injury and stroke. Dana received her Ph.D. from the

University of Florida in the fall of 2015. Following conferral of her degree, she went on to complete her post-doctoral fellowship in neuropsychology through the Departments of

Neurology and Radiology at the Medical University of South Carolina. There, she sought to further her training and expertise in the area of neuropsychological assessment and research for a career working with both acute and chronic neurologic injury and disease. 143