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Title: Individual differences in cortical constraints of visual abilities
Author: Cook, Emily
ISNI:       0000 0004 8498 8430
Awarding Body: Royal Holloway, University of London
Current Institution: Royal Holloway, University of London
Date of Award: 2016
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This thesis investigates how various cortical parameters constrain individual differences in low and intermediate level visual abilities by combining psychological and neuroscientific methodologies. The first 3 experiments consider individual difference in cortical magnification. Firstly, inter- and intra-individual differences of retinotopic maps were investigated. It was documented that there is both high inter- and intra- individual variability in multiple cortical parameters. Whilst some clustering between early visual areas was identified, generally visual areas are uncorrelated with one another. Secondly, visual abilities measured psychophysically were compared to cortical magnification in maps thought to underlie these abilities. In contrast with previous literature (Duncan & Boynton, 2003), cortical magnification was a weak predictor of performance in both low level and intermediate level abilities. Experiments 4, 5 and 6 demonstrate that pRF surround size in V1 correlates with individual differences in first and second order surround suppression. This suggests that the 2 processes may not be as different as suggested in the psychophysical literature (Morgan, Mason, & Baldassi, 2000). The more complex phenomenon of crowding also showed an association with pRF parameters, questioning the proposal (Whitney & Levi, 2011) that it is a separate and distinct phenomena to surround suppression. The final experimental section of this thesis expands the link between visual abilities and cortical parameters to a more complex cognitive task. This section offers insight into the cortical processes underpinning the previously documented link between low level visual abilities and measures of IQ (Melnick, Harrison, Park, Bennetto, & Tadin, 2013). These experiments demonstrate that the links between surround suppression and visual reasoning abilities are mediated by levels of gamma-aminobutyric acid (GABA) in the early visual cortex.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available