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Tony GARCIA, Anne-Claire VIRET, Céline PEREZ, Céline CAVEZIAN, Paméla LALIETTE, Françoise HERAN, Olivier GOUT, Sylvie CHOKRON; Cortical Reorganization After Optic Neuritis: A Functional Neuroimaging Approach. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2191.
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© ARVO (1962-2015); The Authors (2016-present)
Previous studies have suggested an early cortical reorganization after optic neuritis involving extra-striate areas, particularly the lateral occipital complex located in the parvocellular pathway. Parvo and magnocellular pathways are known to convey respectively high and low spatial frequencies present in a visual scene. The objective of the present study is to characterize cortical reorganization at the acute phase of a first episode of optic neuritis using a visual categorization task of natural scenes that controls the spatial frequency content of the stimulus. Using this experimental design, we aim to assess the pattern of cortical reorganization when targeting the parvo- or magnocellular pathways in optic neuritis patients.
A categorization task of natural scenes filtered in low spatial frequencies, high spatial frequencies or unfiltered was used. This experiment was coupled to a recording of brain activation by functional MRI in order to study the pattern of cortical activation during the visual categorization task. Three groups were individually analyzed: right optic neuritis patients, left optic neuritis ones and healthy volunteers as controls.
Fifteen patients were prospectively recruited: seven experiencing their first episode of right acute unilateral optic neuritis and eight a left. Twenty five healthy volunteers were also included.In the control group the right eye as the left eye activated temporo-parieto-occipital areas bilaterally with a greater volume in the hemisphere contralateral to the visual stimulation.In the left optic neuritis group, both for the affected eye and the fellow eye, low spatial frequencies activated more areas than high spatial frequencies. This effect was bilateral but more sustained activity was observed in the contralateral side of the stimulated eye.In the right optic neuritis group, for the affected as well as for the fellow eye, high spatial frequencies recruited more areas than low spatial frequencies, bilaterally but mainly contralateral.
The present findings show for the first time a different pattern of cortical activation depending on the laterality of the optic neuritis and on the spatial frequency of the visual scene. Given the fact that there is a hemispheric specialization for spatial frequency processing with a left hemisphere specialization for high spatial frequencies and a right hemisphere specialization for low spatial frequencies, the present results raise the question of an interaction between the lesion side in optic neuritis patients and the hemispheric specialization for visual processing in cortical reorganization.
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