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Lucia M. Vaina, Sergei Soloviev; Functional stealing: Reorganization of the retinotopic map after occipital lobe infarct. Journal of Vision 2006;6(6):401. doi: 10.1167/6.6.401.
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© ARVO (1962-2015); The Authors (2016-present)
fMRI in a neurological patient with a right hemisphere infarct showed that the lesion partially involved the areas V1, V2d, V2v and VP. Method: To localize and quantify training related changes in activity over time we performed retinotopic mapping and hMT+ localization at: 3, 6 and 9 months after the infarct. Using surface-based measurements we quantified the reorganization and areas-shifts by measuring distances between the center of mass of functionally defined areas. Shifts between areas were computed in spherical surface-based coordinates. Results: Areas V1, V2v, V2d and VP were initially smaller in the affected side compared to the normal side, but increased significantly over time, at the expense of functional areas not involved in the lesion (V3, V4, hMT+) which became comparatively smaller. At 9 months there was an impressive reorganization of the early retinotopic areas in the lesioned (right) hemisphere but not in the normal hemisphere or in normal subjects. The most dramatic changes were seen in areas presumably involved in mediating the visual motion tasks that the patient was trained on over 9 month in weekly 3 hours sessions. Conclusion: The extent of shift and change in areas' surface demonstrate training-dependent large-scale reorganization in the retinotopic map around the lesion. Topography was maintained, but there was a dramatic functional stealing from nearby intact areas by areas involved in the lesion. Areas involved in the lesion and solicited by the motion tasks during training expanded, while areas not involved in lesion, but underlying the trained motion stimuli, became smaller.
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