DOCSLIB.ORG

Unmasking Saccadic Uncrowding ⇑ Mehmet N

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Unmasking Saccadic Uncrowding ⇑ Mehmet N Vision Research 127 (2016) 152–164 Contents lists available at ScienceDirect Vision Research journal homepage: www.elsevier.com/locate/visres Unmasking saccadic uncrowding ⇑ Mehmet N. Ag˘aog˘lu a, , Haluk Ög˘men b, Susana T.L. Chung a a School of Optometry, University of California, Berkeley, Berkeley, CA 94720-2020, United States b Department of Electrical & Computer Engineering, University of Denver, Denver, CO 80208, United States article info abstract Article history: Stimuli that are briefly presented around the time of saccades are often perceived with spatiotemporal Received 5 July 2016 distortions. These distortions do not always have deleterious effects on the visibility and identification Received in revised form 6 August 2016 of a stimulus. Recent studies reported that when a stimulus is the target of an intended saccade, it is Accepted 7 August 2016 released from both masking and crowding. Here, we investigated pre-saccadic changes in single and crowded letter recognition performance in the absence (Experiment 1) and the presence (Experiment 2) of backward masks to determine the extent to which saccadic ‘‘uncrowding” and ‘‘unmasking” mech- Keywords: anisms are similar. Our results show that pre-saccadic improvements in letter recognition performance Crowding are mostly due to the presence of masks and/or stimulus transients which occur after the target is pre- Masking Remapping sented. More importantly, we did not find any decrease in crowding strength before impending saccades. Perisaccadic perception A simplified version of a dual-channel neural model, originally proposed to explain masking phenomena, Neural modeling with several saccadic add-on mechanisms, could account for our results in Experiment 1. However, this model falls short in explaining how saccades drastically reduced the effect of backward masking (Experiment 2). The addition of a remapping mechanism that alters the relative spatial positions of stim- uli was needed to fully account for the improvements observed when backward masks followed the letter stimuli. Taken together, our results (i) are inconsistent with saccadic uncrowding, (ii) strongly support saccadic unmasking, and (iii) suggest that pre-saccadic letter recognition is modulated by multiple perisaccadic mechanisms with different time courses. Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction factors, such as attention (Freeman & Pelli, 2007; Grubb et al., 2013; Yeshurun & Rashal, 2010) and perceptual grouping Objects that fall on the fovea can be easily recognized whereas (Manassi, Sayim, & Herzog, 2012, 2013) also affect crowding. they may be difficult to recognize in the periphery due to factors Crowding is a major bottleneck for object recognition and a funda- such as the reduced photoreceptor density of the peripheral retina. mental component of conscious spatial vision (Levi, 2008; Pelli & Recognition is even more difficult when objects are closely sur- Tillman, 2008; Whitney & Levi, 2011). rounded by other objects, a phenomenon called crowding While crowding impairs the recognition of an object, it leaves (Bouma, 1970; Chung, Levi, & Legge, 2001). The crowding strength the detectability of its features unaffected (e.g., Levi, Hariharan, & is generally defined as a reduction in recognition performance due Klein, 2002). Masking refers to the reduction in visibility of a (tar- to the presence of flanking objects (Levi, 2008; Whitney & Levi, get) stimulus when it is presented in close spatiotemporal proxim- 2011). There are many accounts of crowding, but one account sug- ity to another (mask) stimulus (Breitmeyer & Ogmen, 2006). gests that crowding results from the obligatory integration of fea- Masking and crowding are affected similarly by certain spatiotem- tures within a spatial window. The extent of this window, the poral properties of the stimuli such as stimulus onset asynchrony critical distance, scales with eccentricity (Bouma, 1970; Chung and duration (Chung et al., 2001; Lev & Polat, 2015); however, they et al., 2001). The crowding strength and the critical distance also have distinct characteristics (Chung et al., 2001; Pelli, depend on temporal properties of the stimuli (Chung, 2016; Palomares, & Majaj, 2004). Chung & Patel, 2011; Lev, Yehezkel, & Polat, 2014). Many other In this paper, we define flankers (i.e., stimuli crowding a target stimulus) as stimuli of the same object category (e.g., letters) as the target, although we note that flankers that belong to different ⇑ Corresponding author at: 360 Minor Hall, University of California, Berkeley, object categories can also induce crowding (Chanceaux, Mathot, Berkeley, CA 94720-2020, United States. & Grainger, 2014; He & Tjan, 2004). Masks are defined as stimuli E-mail address: [email protected] (M.N. Ag˘aog˘lu). http://dx.doi.org/10.1016/j.visres.2016.08.003 0042-6989/Ó 2016 Elsevier Ltd. All rights reserved. M.N. Ag˘aog˘lu et al. / Vision Research 127 (2016) 152–164 153 that do not have structures or features as those of the target (e.g., either during fixation (with the letters presented in the peripheral noise masks). Crowding can occur in the absence of masking, and retina), or after a saccadic eye movement following the offset of a vice versa. When flankers and masks are presented in combination, cue located at the location of the target letter. To quantify the the net effect may not be equal to the sum of the individual effects. changes in crowding strength due to impending saccades, the tar- Certain types of masks reduce flankers’ visibility, which in turn get letter was presented either alone or with two horizontally reduces crowding (Chakravarthi & Cavanagh, 2009). When a target flanking letters. In Experiment 1, we specifically tested the is crowded and weakly masked, the combined deleterious effect is hypotheses that (i) saccade targets are released from crowding, larger than the sum of their individual effects, known as ‘‘super- and (ii) perisaccadic mechanisms interact with the temporal order crowding” (Vickery, Shim, Chakravarthi, Jiang, & Luedeman, of the stimuli. In Experiment 2, we specifically tested the hypoth- 2009). Crowding the ‘‘crowders” (i.e., flankers) or masking the esis that impending saccades reduce masking. By comparing the masks can restore the recognizability or the visibility of a target results from both experiments, we also tested the hypothesis that (Manassi et al., 2013; Ogmen, Breitmeyer, Todd, & Mardon, remapping (in the form of perceptual displacements) affects pre- 2006). The evidence reviewed here suggests that, although they saccadic masking but not crowding. can be dissociated in some settings, masking and crowding might Saccades have been shown to result in increased detection share common neural mechanisms under certain conditions. More- thresholds (known as saccadic suppression) and enhanced discrim- over, most stimuli used to study crowding and masking activate ination performance (e.g., Bridgeman, Hendry, & Stark, 1975; both mechanisms, therefore, it is difficult to disentangle their indi- Deubel & Schneider, 1996). In order to understand how mecha- vidual contributions to the final percept. nisms with such opposite effects might play a role in pre- A powerful paradigm to study these processes is the pre- saccadic object recognition, we used a simplified version of a saccadic ‘‘uncrowding” and ‘‘unmasking”, in which the presenta- dual-channel neural model of visual masking to account for the tion of the stimuli (i.e., target-mask or target-flanker displays) data in both experiments. This model could account for letter prior to an impending saccade reduces the impairments due to recognition performance during fixation, suggesting that masking crowding and masking (De Pisapia, Kaunitz, & Melcher, 2010; and crowding might share common low-level mechanisms. Finally, Harrison, Mattingley, & Remington, 2013). Saccades constitute a by adding several independent saccadic mechanisms to this model, fundamental aspect of normal vision; hence, it is essential to we sought to tease apart different components of pre-saccadic understand how visual processes operate under pre-saccadic con- modulations in letter recognition. ditions. As a consequence of saccades, retinal images are frequently displaced, yet we perceive a stable and coherent world. How does 2. Methods the visual system achieve perceptual stability? Among many pro- posals, much attention is received by those based on updating a 2.1. Overview highly detailed retinotopic map via shifts of neuronal receptive fields (RF) or attentional resources (Burr, Ross, Binda, & Morrone, In Experiment 1, we aimed to determine whether or not, and 2010; Cavanagh, Hunt, Afraz, & Rolfs, 2010; Melcher & Colby, how pre-saccadic letter recognition is affected by the temporal 2008; Wurtz, 2008). Neurons which shift their RFs in parallel to order of presentation of a target and its flankers. The target letter the direction of an impending saccade toward the retinal locations was presented either alone (unflanked) or accompanied by two that they will occupy (‘‘future field”) after a saccade, commonly horizontally flanking letters with a varying flanker-target onset referred to as ‘‘remapping”, have been found in several cortical asynchrony (FTOA). A negative FTOA means that the flanker letters and subcortical structures (Duhamel, Colby, & Goldberg, 1992; were presented before the target letter, a positive FTOA means that Nakamura & Colby, 2002; Sommer & Wurtz, 2006; Umeno & the target letter was presented first, and zero FTOA corresponds to Goldberg, 1997; Walker,
Load more

Recommended publications
  • Explanation of the Perceptual Oblique Effect Based on the Fidelity of Oculomotor Control During Saccades
    Explanation of the Perceptual Oblique Effect Based on the Fidelity of Oculomotor Control During Saccades Khuong N. Nguyen∗, Xi Liuy, Oleg Komogortsevz, Ricardo Gutierrez-Osuna∗, and Yoonsuck Choe∗ ∗Department of Computer Science and Engineering, Texas A&M University - College Station, TX 77843 yDepartment of Electrical and Computer Engineering, Texas A&M University - College Station, TX 77843 zDepartment of Computer Science, Texas State University - San Marcos, TX 78666 Abstract—The oblique effect, observed in both humans and perception in the brain [8]. We propose that a possible ex- animals, refers to the phenomenon of differential perceptual planation can be found in the oculomotor system. Research performance in visual recognition tasks that involve horizontal in active vision and perceptual performance discovered that and vertical, vs. diagonal patterns. Furthermore, differences have been found in the visual cortical organization for the horizontal saccadic eye movements (SEMs) follow different systematic and vertical vs. diagonal representations. However, why such curvatures for different angles [9]. While horizontally and structural differences leading to functional divergence emerge vertically SEMs are smooth and aligned along the major axis, in the first place is yet to be explained. In this paper, we oblique SEMs experiences shakiness and deviation from the propose a potential explanation for the oblique effect based on the center lines. Given the above, we propose that the oblique differences in the sampling of oriented edge inputs along different angles due to mechanics of eye movement. Our hypothesis is effect is due to less precise ocular motions along the oblique that the oblique effect is mainly due to eye movement along the directions, which makes the image samples taken along the diagonal directions being less precise than the horizontal and the trajectory more variable than the samples taken along the vertical, which causes the sampling of the angles more variable vertical or horizontal directions.
    [Show full text]
  • Flicker Can Be Perceived During Saccades at Frequencies in Excess
    Lighting Res. Technol. 2013; 45: 124-132 Flicker can be perceived during saccades at frequencies in excess of 1 kHz JE Roberts MSc and AJ Wilkins DPhil Department of Psychology, University of Essex, Colchester, UK Received 30 November2011; Revised 31 December 2011; Accepted 1 January 2012 When driving at night, flickering automobile LED tail lights can appear as multiple images. The perception of a flickering source of light was therefore studied during rapid eye movements Isaccades) of 20-400 amplitude in an otherwise dark room !<1Iuxl. The temporal modulation appeared as a spatial pattern known as a 'phantom array' during the saccade. The appearance of the pattern enabled the discrimination of flicker from steady light at frequencies that in 11 observers averaged 1.98 kHz. At a frequency of 120 Hz, the intrasaccadic pattern was perceptible when the contrast of the flicker exceeded 10%. It is possible that intrasaccadic stimulation interferes with ocular motor control. 1, Introduction fusion frequency is, however, usually measured with a spatially unstructured field. When driving at night behind a car with LED It is rarely measured during eye movements, tail lights, it is possible to experience a trail of and when it is, estimates of the critical lights with each rapid movement of the eyes freq uency increase.4 When each flash of a (saccade). The trail occurs because the LED spatially structured light source is imaged on lamps are lit intermittently to control heat a different part of the retina during a rapid build-up. The frequency ofoperation is above eye movement, the light source forms a flicker fusion, varies from one manufacturer 'phantom array', and the above example of to another and may not be the same for both tail light flicker shows that the array is tail lamps, to judge from videos posted on the sometimes perceptible under everyday view­ web.
    [Show full text]
  • The Role of the Brain in Perception
    BEHAVIORAL AND BRAIN SCIENCES (2001) 24, 939–1031 Printed in the United States of America A sensorimotor account of vision and visual consciousness J. Kevin O’Regan Laboratoire de Psychologie Expérimentale, Centre National de Recherche Scientifique, Université René Descartes, 92774 Boulogne Billancourt, France [email protected] http://nivea.psycho.univ-paris5.fr Alva Noë Department of Philosophy, University of California at Santa Cruz, Santa Cruz, CA 95064 [email protected] http://www2.ucsc.edu/people/anoe/ Abstract: Many current neurophysiological, psychophysical, and psychological approaches to vision rest on the idea that when we see, the brain produces an internal representation of the world. The activation of this internal representation is assumed to give rise to the experience of seeing. The problem with this kind of approach is that it leaves unexplained how the existence of such a detailed internal representation might produce visual consciousness. An alternative proposal is made here. We propose that seeing is a way of acting. It is a particular way of exploring the environment. Activity in internal representations does not generate the experience of seeing. The out- side world serves as its own, external, representation. The experience of seeing occurs when the organism masters what we call the gov- erning laws of sensorimotor contingency. The advantage of this approach is that it provides a natural and principled way of accounting for visual consciousness, and for the differences in the perceived quality of sensory experience in the different sensory modalities. Sev- eral lines of empirical evidence are brought forward in support of the theory, in particular: evidence from experiments in sensorimotor adaptation, visual “filling in,” visual stability despite eye movements, change blindness, sensory substitution, and color perception.
    [Show full text]
  • Backward and Forward Masking Associated with Saccadic Eye Movement
    Perception & Psychophysics 1981, 30 (1), 62- 70 Backward and forward masking associated with saccadic eye movement BARBARA A. BROOKS, DIANNE M. K. IMPELMAN, and JANET T. LUM Department ofPhysiology, University ofTexas Health Science Center, San Antonio, Texas 78284 Visual masking effects on test flash thresholds were measured under real and simulated eye movement conditions to determine whether visual masking is primarily responsible for elevations in threshold that are sometimes associated with saccadic eye movements. Brief luminous flashes presented to the central retina before,during, and after saccades were masked by stimuli presented either pre- or postsaccadically. The amount and time course of masking were quantitatively dependent on stimulus parameters of intensity and temporal separation and were unaffected by eye movement parameters (amplitude, velocity, direction) as long as retinal stimulus conditions were constant. The duration of forward masking was longer than that of backward masking. When retinal conditions during saccades were mimicked while the eyes were held steady, masking interactions were identical to those obtained during real saccades.These results indicate that masking effects during saccades in ordinary environments are determined solely by the stimulus situation at the retina. Putative nonvisual, centrally originating saccadic suppression suggested by other authors is evidently not additive with visually determined masking during saccades. The term "masking" refers to the competitive only during saccadic movement, the blurred world interaction between two or more visual stimuli pre­ can readily be seen (Campbell & Wurtz, 1978; related sented close together in time and space. A stimulus is observations in the fixating eye by Corfield, Frosdick, said to be masked when its visibility is diminished or & Campbell, 1978).
    [Show full text]
  • Unmasking Saccadic Uncrowding
    UC Berkeley UC Berkeley Previously Published Works Title Unmasking saccadic uncrowding. Permalink https://escholarship.org/uc/item/52t3z95b Authors Ağaoğlu, Mehmet N Öğmen, Haluk Chung, Susana TL Publication Date 2016-10-01 DOI 10.1016/j.visres.2016.08.003 Peer reviewed eScholarship.org Powered by the California Digital Library University of California Vision Research 127 (2016) 152–164 Contents lists available at ScienceDirect Vision Research journal homepage: www.elsevier.com/locate/visres Unmasking saccadic uncrowding ⇑ Mehmet N. Ag˘aog˘lu a, , Haluk Ög˘men b, Susana T.L. Chung a a School of Optometry, University of California, Berkeley, Berkeley, CA 94720-2020, United States b Department of Electrical & Computer Engineering, University of Denver, Denver, CO 80208, United States article info abstract Article history: Stimuli that are briefly presented around the time of saccades are often perceived with spatiotemporal Received 5 July 2016 distortions. These distortions do not always have deleterious effects on the visibility and identification Received in revised form 6 August 2016 of a stimulus. Recent studies reported that when a stimulus is the target of an intended saccade, it is Accepted 7 August 2016 released from both masking and crowding. Here, we investigated pre-saccadic changes in single and crowded letter recognition performance in the absence (Experiment 1) and the presence (Experiment 2) of backward masks to determine the extent to which saccadic ‘‘uncrowding” and ‘‘unmasking” mech- Keywords: anisms are similar. Our results show that pre-saccadic improvements in letter recognition performance Crowding are mostly due to the presence of masks and/or stimulus transients which occur after the target is pre- Masking Remapping sented.
    [Show full text]
  • Previous Studies (Li, Barbot, & Carrasco, (Morey, 2008)
    Journal of Vision (2020) 20(4):17, 1–24 1 Intra-saccadic motion streaks as cues to linking object locations across saccades Department of Psychology, Humboldt-Universität zu Berlin, Berlin, Germany Bernstein Center for Computational Neuroscience Berlin, Berlin, Germany Berlin School of Mind and Brain, Humboldt-Universität Richard Schweitzer zu Berlin, Berlin, Germany Department of Psychology, Humboldt-Universität zu Berlin, Berlin, Germany Bernstein Center for Computational Neuroscience Berlin, Berlin, Germany Berlin School of Mind and Brain, Humboldt-Universität Martin Rolfs zu Berlin, Berlin, Germany When visual objects shift rapidly across the retina, they produce motion blur. Intra-saccadic visual signals, Introduction caused incessantly by our own saccades, are thought to be eliminated at early stages of visual processing. Here The dystopian science-fiction television series “Black we investigate whether they are still available to the Mirror” featured an episode in which people could visual system and could—in principle—be used as cues record memories through their pupils (Armstrong & for localizing objects as they change locations on the Welsh, 2011). Replays of these memories revealed a retina. Using a high-speed projection system, we common but wrong intuition of how our eyes capture developed a trans-saccadic identification task in which the world around us. They showed skillfully crafted brief but continuous intra-saccadic object motion was videos, with smooth camera movements from one key to successful performance. Observers made a location to the next. In reality, we make several saccadic saccade to a target stimulus that moved rapidly either up eye movements every second that rapidly shift the or down, strictly during the eye movement.
    [Show full text]
  • Intra-Saccadic Motion Streaks As Cues to Linking
    Journal of Vision (2020) 20(4):17, 1–24 1 Intra-saccadic motion streaks as cues to linking object locations across saccades Department of Psychology, Humboldt-Universität zu Berlin, Berlin, Germany Bernstein Center for Computational Neuroscience Berlin, Berlin, Germany Berlin School of Mind and Brain, Humboldt-Universität Richard Schweitzer zu Berlin, Berlin, Germany Department of Psychology, Humboldt-Universität zu Berlin, Berlin, Germany Bernstein Center for Computational Neuroscience Berlin, Berlin, Germany Berlin School of Mind and Brain, Humboldt-Universität Martin Rolfs zu Berlin, Berlin, Germany When visual objects shift rapidly across the retina, they produce motion blur. Intra-saccadic visual signals, Introduction caused incessantly by our own saccades, are thought to be eliminated at early stages of visual processing. Here The dystopian science-fiction television series “Black we investigate whether they are still available to the Mirror” featured an episode in which people could visual system and could—in principle—be used as cues record memories through their pupils (Armstrong & for localizing objects as they change locations on the Welsh, 2011). Replays of these memories revealed a retina. Using a high-speed projection system, we common but wrong intuition of how our eyes capture developed a trans-saccadic identification task in which the world around us. They showed skillfully crafted brief but continuous intra-saccadic object motion was videos, with smooth camera movements from one key to successful performance. Observers made a location to the next. In reality, we make several saccadic saccade to a target stimulus that moved rapidly either up eye movements every second that rapidly shift the or down, strictly during the eye movement.
    [Show full text]
  • The Causal Role of Neural Oscillations in Attentional and Perceptual Sampling Mechanisms Samson Chota
    The causal role of neural oscillations in attentional and perceptual sampling mechanisms Samson Chota To cite this version: Samson Chota. The causal role of neural oscillations in attentional and perceptual sampling mecha- nisms. Human health and pathology. Université Paul Sabatier - Toulouse III, 2020. English. NNT : 2020TOU30110. tel-03117853 HAL Id: tel-03117853 https://tel.archives-ouvertes.fr/tel-03117853 Submitted on 21 Jan 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. THÈSE En vue de l’obtention du DOCTORAT DE L’UNIVERSITÉ DE TOULOUSE Délivré par l'Université Toulouse 3 - Paul Sabatier Présentée et soutenue par Samson CHOTA Le 20 octobre 2020 Étude de la relation causale entre les oscillations cérébrales et la perception en utilisant des techniques non invasives de stimulation cérébrale Ecole doctorale : CLESCO - Comportement, Langage, Education, Socialisation, Cognition Spécialité : Neurosciences Unité de recherche : CERCO - Centre de Recherche Cerveau et Cognition Thèse dirigée par Rufin VANRULLEN Jury Mme Laura DUGUé, Rapporteure
    [Show full text]
  • Masking the Saccadic Smear
    1 Masking the saccadic smear 2 3 Marianne Duyck1, Thérèse Collins & Mark Wexler 4 5 Laboratoire Psychologie de la Perception 6 Université Paris Descartes & CNRS UMR 8242 7 45 rue des Saints-Pères 8 75006 Paris, France 9 10 Abstract 11 Static visual stimuli are smeared across the retina during saccades, but in normal 12 conditions this smear is not perceived. Instead, we perceive the visual scene as static 13 and sharp. However, retinal smear is perceived if stimuli are shown only intra- 14 saccadically, but not if the stimulus is additionally shown before a saccade begins, or 15 after the saccade ends (Campbell & Wurtz, 1978). This inhibition has been compared to 16 forward and backward metacontrast masking, but with spatial relations between 17 stimulus and mask that are different from ordinary metacontrast during fixation. 18 Previous studies of smear masking have used subjective measures of smear perception. 19 Here we develop a new, objective technique for measuring smear masking, based on the 20 spatial localization of a hole in the smear created by very quickly blanking the stimulus 21 at various points during the saccade. We apply this technique to show that smear 22 masking survives dichoptic presentation (and is therefore cortical in origin), as well as 23 separations of as much as 6 deg between smear and mask. 24 25 26 1 Corresponding author: [email protected] 27 Introduction 28 Any model of vision which takes the retinal image as a starting point immediately runs 29 into the problem of eye movements, and in particular saccades. Although saccades lead 30 to frequent, rapid displacements of the retinal image, the retinal consequences of these 31 displacements are largely not perceived.
    [Show full text]
  • Fixations Curvature Microsaccades.Pdf
    Fixa%ons Microsaccades saccadic curvature Review: The visual coordinate system • Spaotopic coordinates • This is the world we think we see • Stable, unless objects are moving in the world • But, As we move our eyes, the image on the re$na changes • And neurons in the visual cortex are a 2D map of the re$na • Re$notopic coordinates • This is the world as it falls on the re$na of the eye • If objects in the world fall on different neurons, how does the visual system know they are the same object? Review: Re%notopic coordinates The nave frame of reference for human vision is re$notopic (Golomb, 2008) Review: Spaotopic coordinates ? This is the problem of Visual stability Maintained fixaon • We always say this is a period of ‘relave’ ocular stability Scleral coil. Ouch. • Earliest studies on small movements within fixaon used Scleral Eye Coil (or variant) • .01 dva • 1000+hz • Steinman, et al. (1973). Miniature eye Dual purkinje (corneal reflec$ons) movement. Science Front(1) and rear(2) reflec$ons of cornea • A lot is based on this early work Front (3) and rear(4) reflec$ons lens Fixa%onal Moon • Slow fixaonal oscilaons • dri], slow control • Occasional, small interrup$ons • Microsaccades • 2-3 per second • 12’ – 15’ • Usually binocular Slow control: Moon • If the visual cortex is a re$nal map of visual input • Then eye mo$on will create input ‘blur’ • Too much mo$on impairs vision (Burr&Ross, 1982) • High velocity mo$on from saccades (up to 900 Corollary Discharge. A corollary deg/sec) is blocked perceptually discharge (CD) is a copy of a motor • Saccadic suppression, aka saccadic masking command that is sent to the muscles to • Look in the mirror, you cannot see your own produce a movement.
    [Show full text]
  • The Four Chances for Error
    The Looked but Failed to See Motorcyclist/car Collision Four Chances for Error* Introduction Understanding the four chances for error and the associated visual phenomena is helpful in furthering our understanding of the Looked But Failed to See (LBFTS) Right-of-way Violation (ROWV) motorcyclist/car collision scenario. Knowing these four chances for error, and the associated phenomena, is also helpful in formulating recommended actions for both riders and drivers that will lessen the chance of these types of collision occurring. A key point to understand is the human eyes and brain is not the equivalent of the lens of a camera. The commonsense argument that “if it is visible, we will see it if we look hard enough” simply isn’t true. 1. Didn’t look. Did the driver fail to look? If the driver is distracted or misunderstands the road layout (for example having no experience regarding traffic flow at a roundabout), he or she might not look or might not look in the necessary direction. Riders need to be aware of situations that might be complicated for drivers, reduce speed, and be prepared to take evasive action. Drivers need to eliminate distractions while driving and take extra time to focus at unfamiliar road layouts. 2. Looked but couldn’t see. The driver looks but the motorcyclist is not visible. If the motorcyclist is in the “wrong place” (for example behind a larger vehicle) or the motorcyclist is appropriately placed but the driver’s view of the motorcyclist is blocked (for example, by the car pillar or a roadway obstacle like a light pole) the driver could look but fail to see the motorcyclist.
    [Show full text]
  • I0035-8711-380-1-06978.Pdf —
    Journal of Vision (2020) 20(4):17, 1–24 1 Intra-saccadic motion streaks as cues to linking object locations across saccades Department of Psychology, Humboldt-Universität zu Berlin, Berlin, Germany Bernstein Center for Computational Neuroscience Berlin, Berlin, Germany Berlin School of Mind and Brain, Humboldt-Universität Richard Schweitzer zu Berlin, Berlin, Germany Department of Psychology, Humboldt-Universität zu Berlin, Berlin, Germany Bernstein Center for Computational Neuroscience Berlin, Berlin, Germany Berlin School of Mind and Brain, Humboldt-Universität Martin Rolfs zu Berlin, Berlin, Germany When visual objects shift rapidly across the retina, they produce motion blur. Intra-saccadic visual signals, Introduction caused incessantly by our own saccades, are thought to be eliminated at early stages of visual processing. Here The dystopian science-fiction television series “Black we investigate whether they are still available to the Mirror” featured an episode in which people could visual system and could—in principle—be used as cues record memories through their pupils (Armstrong & for localizing objects as they change locations on the Welsh, 2011). Replays of these memories revealed a retina. Using a high-speed projection system, we common but wrong intuition of how our eyes capture developed a trans-saccadic identification task in which the world around us. They showed skillfully crafted brief but continuous intra-saccadic object motion was videos, with smooth camera movements from one key to successful performance. Observers made a location to the next. In reality, we make several saccadic saccade to a target stimulus that moved rapidly either up eye movements every second that rapidly shift the or down, strictly during the eye movement.
    [Show full text]