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Sara Rafique, John Richards, Jennifer Steeves; Visual hallucinations following occipital stroke associated with altered structural connectivity. Journal of Vision 2017;17(10):180. doi: https://doi.org/10.1167/17.10.180.
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Irreversible damage to the visual pathway that results in vision loss can produce visual hallucinations in cognitively healthy individuals. These visual hallucinations stem from disruption to neuronal function that leads to aberrant functional activity across visual cortices and associated cortical networks. We sought to investigate structural changes in white matter connectivity and its contribution to chronic visual hallucinations following damage to the visual cortex. We performed diffusion tensor imaging to assess white matter in a patient suffering from continuous and disruptive unformed visual hallucinations for more than 2 years following right occipital stroke, and in healthy age-matched controls. White matter structure was reconstructed using probabilistic fibre tractography, and diffusion was quantified by measuring diffusion tensor indices. Using probabilistic tractography, we reconstructed reciprocal white matter tracts between the lateral geniculate nucleus and visual cortex, and between visual cortices. Tracts were further reconstructed from visual cortex to frontal, temporal, and parietal regions of interest based on fMRI findings showing functional differences in the patient compared with healthy age-matched controls. White matter tracts showed regeneration of terminal fibres of ipsilesional optic radiations in the patient that were displaced anterior to the lesion site; however, reciprocal intrahemispheric tracts from ipsilesional visual cortex to lateral geniculate body were disrupted. There was an absence of interhemispheric white matter tracts from ipsilesional to contralesional primary visual cortex, while contralesional to ipsilesional tracts were spared in the patient. Further, we observed compromised structural characteristics and changes in diffusion of white matter tracts in the patient connecting the visual cortex with frontal and temporal regions. This cortical remapping and disruption of communication between visual cortices and from visual cortex to remote regions is consistent with our previous findings showing imbalanced functional activity of the same regions associated with chronic visual hallucinations in the patient.
Meeting abstract presented at VSS 2017
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