Are Visual Stimuli Neighboring Attended Stimuli Suppressed In
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Linköping University | The Department of Computer Science Bachelor Thesis, 18 ECTS | Cognitive Science Spring 2016 | LIU-IDA/KOGVET-G--16/017—SE Is Visual Stimuli Neighboring Attended Stimuli Suppressed in High Perceptual Load? A Steady State Evoked Potential Study Kan visuellt distraktor-stimuli påverkas av perceptuell belastning? Author: Linn Maria Elisabeth Bergström Supervisor at Linköping University: Carine Signoret Supervisor at Stockholm University: Stefan Wiens Examinator, Linköping University: Rachel Ellis Linköpings universitet SE-581 83 Linköping 013-28 10 00, www.liu.se Is Visual Stimuli Neighboring Attended Stimuli Suppressed in High Perceptual Load? Upphovsrätt Detta dokument hålls tillgängligt på Internet – eller dess framtida ersättare – under 25 år från publiceringsdatum under förutsättning att inga extraordinära omständigheter uppstår. 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For additional information about the Linköping University Electronic Press and its procedures for publication and for assurance of document integrity, please refer to its www home page: http://www.ep.liu.se/. © Linn Maria Elisabeth Bergström 2 Is Visual Stimuli Neighboring Attended Stimuli Suppressed in High Perceptual Load? Abstract Perceptual load theory, together with the surround-suppression model suggest that stimulus surrounding attended stimuli is suppressed, especially if perceptual load is high. This study attempts to map surround-suppression using electroencephalography to measure neural activity related to suppression at four surrounding locations (2°, 3°, 4° and 6° from fixation). Color and orientation was used to manipulate load, and the effect of load was controlled through behavioral and neural measures using event related potentials. Our results demonstrate no statistically supported effect of load in behavioral data or SSVEP data, but unexplained increased neural amplitude of an early visual component (i.e. N1) in the (hypothesized) low load condition. 3 Is Visual Stimuli Neighboring Attended Stimuli Suppressed in High Perceptual Load? 4 Is Visual Stimuli Neighboring Attended Stimuli Suppressed in High Perceptual Load? Table of Contents ABSTRACT ........................................................................................................................................... 3 INTRODUCTION ................................................................................................................................. 6 BACKGROUND .................................................................................................................................... 6 THE CURRENT STUDY ................................................................................................................................... 10 ALTERNATIVE THEORIES ............................................................................................................................. 11 LIMITATIONS OF THE STUDY ....................................................................................................................... 12 METHOD.............................................................................................................................................12 SUBJECTS ........................................................................................................................................................ 12 STIMULI ........................................................................................................................................................... 12 PROCEDURE .................................................................................................................................................... 13 DESIGN ............................................................................................................................................................ 14 EEG RECORDINGS AND ANALYSIS ............................................................................................................... 14 STEADY STATE VISUAL EVOKED POTENTIALS (SSVEPS) ..................................................................... 15 EVENT RELATED POTENTIALS (ERPS) ..................................................................................................... 16 RESULTS .............................................................................................................................................16 BEHAVIOURAL PERFORMANCE ................................................................................................................... 16 SSVEPS ........................................................................................................................................................... 17 ERPS ............................................................................................................................................................... 18 DISCUSSION.......................................................................................................................................19 RESULT DISCUSSION ..................................................................................................................................... 20 Assuming there is no Effect of Load in the Data ............................................................................ 21 Assuming there is an Effect of Load in the Data ............................................................................ 21 METHOD DISCUSSION ................................................................................................................................... 22 CONCLUSION .................................................................................................................................................. 23 REFERENCES .....................................................................................................................................24 5 Is Visual Stimuli Neighboring Attended Stimuli Suppressed in High Perceptual Load? Introduction This study aims to add evidence and understanding in the neuropsychological attempt to figure out how human perception works. More specifically, how we perceive our environment and how we focus our attention to be able to make sense of the world and not be overwhelmed by the multitude of stimuli surrounding us. In the past and still today, the neural and cognitive mechanisms that allow our perception are debated and many theories have been suggested, some of which will be discussed below. Perception and attention are cognitive functions that are important in our everyday life to be able to function in the world around us, act and interact appropriately with other people and things in our environment. A better understanding of our attentional and perceptual system could help improve design in situations where human attention and perception plays a vital roll, for example in driving situation. Understanding the relationship between attention and perception could also be an important contributor to reversing attentional deficit disorders. Background The environment is filled with stimuli. Our sensory systems are dedicated to register and process information from the world and make us conscious of our environment. Our awareness of our environment is in cognitive terms called perception and defined by Purves et al. (2008, pp. 40-41) as: “… the conscious awareness of external and internal environment generated by neural processing carried out by the human sensory systems … In vision, the fundamental qualities of perceptual awareness are brightness, color, form, depth and motion … [The] complex aspects of conscious awareness quickly transcend the notion of perception as simply the end result of sensory processing and clearly depend on a host of other cognitive functions including learning,