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Title: The electrophysiological response to visual symmetry : hemisphere lateralisation and visual clutter
Author: Wright, D.
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2016
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The experiments reported in this thesis explore the electrophysiological response to visual symmetry. Symmetry is an important visual feature in object recognition and image segmentation that is efficiently processed by the visual system. Neuroimaging and electrophysiological research has provided a greater understanding of how the human brain processes symmetry. ERP research has identified a neural signature for symmetry processing termed the Sustained Posterior Negativity (SPN): Lower amplitude is observed in posterior electrodes for symmetrical than random patterns from around 200ms after stimulus onset. This thesis will address four important and novel questions: (1) Can the SPN be produced independently within each hemisphere? (2) Is right lateralised alpha desynchronisation during regularity discrimination the result of hemisphere specialisation or directed spatial attention? (3) Does visual crowding influence the SPN? and (4) How does figure-ground assignment influence the neural response to symmetry? The current studies show for the first time that the SPN can be produced to stimuli in the periphery with symmetry processed by independent symmetry sensitive networks within each hemisphere. It also offers evidence that the right hemisphere may be specialised for symmetry perception. Moreover, figure-ground assignment and visual crowding are shown to modulate the SPN. Together these experiments highlight that this automatic response to symmetry is processed independently in each hemisphere and is subject to bottom-up stimulus characteristics.
Supervisor: Bertamini, M. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral