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Visual perception in autism spectrum disorders.

Koh, Hwan Cui (2009) Visual perception in autism spectrum disorders. PhD thesis, University of Sheffield.

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This thesis presents research conducted at the cognitive level, the neurophysiological level and the psycho-physical level, for examining vision in ASD. The psycho-physical findings suggest that atypical visual perception in ASD is unlikely to have a sub-cortical origin as sub-cortical magnocellular and parvocellular pathway functioning, and low/high spatial frequency detection in adolescents with ASD were found to be no different from typically-developing controls. There was, however, evidence indicating local motion direction perception deficits in the same adolescents with ASD suggesting that atypical motion perception in ASD may have a cortical origin. Electrophysiological investigation of low level visual perception in ASD revealed findings concurring with this latter interpretation. More specifically, whereas visual evoked potentials demonstrated visuo-integrative processes associated with perception of second order and hyperbolic gratings were not atypical in children with ASD, there was increased activity of the visual cortical region. A further gamma power analysis then demonstrated that there may be increased neuro-connectivity within primary visual area V1 in the children with ASD. Atypical low level visual cortical processes may result in locally-biased perceptual style previously observed in individuals with ASD. However, a cross-cultural comparison of perceptual style in children with ASD and TD children from Singapore and England, found evidence suggesting that locally-biased perceptual style in ASD may not be culturally universal. In sum, lower level visual cortical processes may be atypical in ASD, and whether these atypicalities manifest at the higher perceptual level can be determined by cultural variability in attention and response processes.

Item Type: Thesis (PhD)
Academic Units: The University of Sheffield > Faculty of Science (Sheffield) > Psychology (Sheffield)
Identification Number/EthosID: uk.bl.ethos.521865
Depositing User: EThOS Import Sheffield
Date Deposited: 20 Apr 2016 10:45
Last Modified: 20 Apr 2016 10:45
URI: http://etheses.whiterose.ac.uk/id/eprint/10348

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