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Title: How vision influences perceived duration : an empirical and computational investigation
Author: Rowland, Edward
ISNI:       0000 0004 8498 1298
Awarding Body: Royal Holloway, University of London
Current Institution: Royal Holloway, University of London
Date of Award: 2015
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Time perception is often thought of as arising from a centralised mechanism. Recently, there has been a shift away from this perspective, with evidence showing that adaptation to particular visual properties at specific locations and stimulus predictability affects perceived event duration, implying that sensory systems carry out duration processing. This thesis investigates the following three questions: (1) Does adaptation induced duration compression affect other visual processes? (2) Can sensory systems encode duration using their basic response properties? (3) What is the relationship between predictability, perceived duration and neural response to a visual stimulus? The first question was investigated using a visual illusion called Flash-Lag, commonly thought to possess a fixed time component. After pilot investigations comparing psychophysical techniques, results from a behavioural experiment show that adapting to a high temporal frequency stimulus reduces the time component of the Flash-Lag illusion, implying a role for duration in positional and/or motion computations. We demonstrate a model using labelled lines and varying temporal response of neurons can encode the duration of a temporally normalised input. This model exhibits effects similar to those observed in literature including adaptation induced duration compression, central tendency and perceived duration scaling with the magnitude of various stimulus properties. Finally, a new paradigm is developed to test if stimulus duration decreases with stimulus predictability. Although behavioural results show no effect of predictability, event related fMRI shows significant differences in BOLD signal. Area MST demonstrates reduced response to expected events in a duration judgement task, but not an orientation judgement task, suggesting response is reduced by predictability, dependent on the task. These results show that duration may be encoded in sensory systems and is used in perceptual tasks. Furthermore, it is proposed that duration is estimated using ramping or climbing activity within neural populations in the dorsal visual pathway.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Vision ; Perception ; Time ; Psychophysics ; Modelling ; fMRI ; Illusions ; flash-lag effect ; Neuroscience(all) ; Sensory Systems