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Nikita Wong, Sara Rafique, Krista Kelly, Stefania Moro, Brenda Gallie, Jennifer Steeves; White matter changes following early loss of one eye extend beyond the primary visual pathway. Journal of Vision 2017;17(10):631. doi: 10.1167/17.10.631.
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Long-term morphological changes following early (< 2 years of age) monocular enucleation (surgical removal of an eye) are present in adult subcortical and cortical visual, auditory, and multisensory regions. Previously we reported increased radial diffusivity (RD) in the right optic radiation of people with one eye, and an absence of the hemispheric asymmetries that exist in controls. In an attempt to determine whether these structural connectivity changes extend to other related white matter tracts, we investigated how the early loss of one eye affects the development of connectivity in: 1) tracts connecting primary visual cortex (V1) to lateral geniculate nucleus (LGN), 2) occipito-callosal connections between left and right V1, 3) auditory radiations, and 4) cortico-cortical projections from primary auditory cortex (A1) to V1. Diffusion-weighted images were acquired for all participants and probabilistic tractography was used to reconstruct the tracts of interest. Average values for fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and RD were extracted bilaterally. In contrast to the optic radiations, the V1-LGN projection in people with one eye was unchanged, compared to controls. However, a significant reduction in FA was observed in the right-to-left V1-V1 projection of the patient group. In both the auditory radiations and A1-V1 tracts, people with one eye did not demonstrate the significant leftward asymmetries that were found in controls. These findings indicate microstructural changes to white matter in people with one eye that extend beyond the primary visual pathway to include interhemispheric, auditory, and multisensory tracts. The lack of asymmetries in the auditory and audiovisual connections may reflect adaptive compensation for the loss of one eye in these sensory modalities, consistent with previous behavioural findings. Overall, these results suggest that early monocular enucleation has distal effects on white matter structure both within the visual system and in other sensory systems.
Meeting abstract presented at VSS 2017
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