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Andrew Bock, Melissa Saenz, Geoffrey Boynton, Holly Bridge, Ione Fine; Lack of visual experience does not affect the retinotopic organization of visual cortico-callosal connections.. Journal of Vision 2012;12(9):1358. doi: 10.1167/12.9.1358.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The visual cortex in each hemisphere is linked to the opposite hemisphere by axonal projections that pass through the splenium of the corpus callosum. Recent human studies (Levin et al., 2010; Lepore et al. 2010) find that early postnatal blindness leads to reductions in splenium white matter volume; however it is not apparent whether these results reflect reductions in myelination and/or disorganization of splenial fibers. Here, using diffusion tractography, we examined the retinotopic organization of splenium connections within 6 anophthalmic and 6 control subjects. In anophthalmia, development of the eye is either absent or arrested at an early prenatal stage, and no functioning eye can be detected in the socket. Methods: Probabilistic diffusion tractography was performed on diffusion-weighted MR data (60 directions). Specifically, we tracked probabilistic fibers from seed points within the splenium to anatomically defined subregions that correspond in visually normal individuals to three eccentricity bands and the upper vs. lower visual field representations of early visual cortex (V1/V2). Each tractography seed point within the splenium was then labeled according to its connection probability to the V1/V2 retinotopic subregions in each hemisphere. This method has previously been shown to reliably identify retinotopic organization of fibers within the corpus callosum (Saenz and Fine, 2010). Results: We found that retinotopic mapping within the splenium was not measurably disrupted in anophthalmic subjects compared to visually normal controls. These results suggest that prenatal retinal activity and/or postnatal visual experience play little to no role in the organization of callosal connections within the splenium.
Meeting abstract presented at VSS 2012
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