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The role of spared calcarine cortex and lateral occipital cortex in the responses of human hemianopes to visual motion

Morland, A.B., Lê, S., Carroll, E., Hoffmann, M.B. and Pambakian, A. (2004) The role of spared calcarine cortex and lateral occipital cortex in the responses of human hemianopes to visual motion. Journal of Cognitive Neuroscience, 16 (2). pp. 204-218. ISSN 0898-929X

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Some patients, who are rendered perimetrically blind in one hemifield by cortical lesions, nevertheless exhibit residual visual capacities within their field defects. The neural mechanism that mediates the residual visual responses has remained the topic of considerable debate. One explanation posits the subcortical visual pathways that bypass the primary visual cortex and innervate the extrastriate visual areas as the substrate that underlies the residual vision. The other explanation is that small islands of the primary visual cortex remain intact and provide the signals for residual vision. We have performed behavioral and functional magnetic resonance imaging experiments to investigate the validity of the two explanations of residual vision. Our behavioral experiments indicated that of the seven hemianopes tested, two had the ability to discriminate the direction of a drifting grating. This residual visual response was shown with fMRI to be the result of spared islands of calcarine cortical activity in one of the hemianopes, whereas only lateral occipital activity was documented in the other patient. These results indicate that the underlying neural correlates of residual vision can vary between patients. Moreover, our study emphasizes the necessity of ruling out the presence of islands of preserved function and primary visual cortex before assigning residual visual capacities to the properties of visual pathways that bypass the primary visual cortex.

Item Type: Article
Institution: The University of York
Academic Units: The University of York > Psychology (York)
Depositing User: York RAE Import
Date Deposited: 23 Apr 2009 13:44
Last Modified: 23 Apr 2009 13:44
Published Version: http://dx.doi.org/10.1162/089892904322984517
Status: Published
Publisher: Massachusetts Institute of Technology Press
Identification Number: 10.1162/089892904322984517
URI: http://eprints.whiterose.ac.uk/id/eprint/6569

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