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Lucia M. Vaina, Sergei Soloviev, Ferdinando Buonanno; Reorganization of human retinotopic cortical map after an occipital lobe infarct: A longitudinal study. Journal of Vision 2004;4(8):191. doi: https://doi.org/10.1167/4.8.191.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: We present a longitudinal psychophysical and fMRI study of a patient with an infarct in the right occipital lobe resulting in a superior paracentral left quadrantopsia. In association with weekly psychophysical training of visual motion dicrimination in the affected quadrant, the patient underwent three fMRI sessions, at 3,6,and 9 months after the infarct. For comparison an identical fMRI study was also carried out once on a normal control. Methods: In each fMRI study we acquired a high resolution structural MRI of the brain, performed functional retinotopic mapping, mapped fMRI responses to full screen flickering checkerboard and perforemd hMT+ localization using radial motion discrimination. Using an automatic procedure for retinotopic localization developed by Dumoulin et al. 2002, we plotted the phase map of FFT at task frequency in polar coordinates and compared the plots for the patient's scans and that of the control. Further, to compare quantitatively the results from different scans obtained over time we introduced an asymmetry index for each pair of retinotopic areas (in the left and right hemisphere), over time (in the patient), and for the percent BOLD signal increase. Results: First, the patient's FFT map over time became more symmetrical and similar to that of the normal subject which correlated with his self-report of some perception in the scotoma. Second, a significant portion of V3 (about 1cm in diamter) became V2d. Third, activity patterns over the three scans in the hMT+ localization test demonstrated that, as activation around the damaged V1 increased, the area of activation in the ispilesional hMT+ decreased (p<<0.01). Conclusion: Over the three fMRI scans there was an orderly reorganization of the retinotopic areas, which we suggest is due to the devlopment of horizontal connections and recruitment of neurons around the lesion. The hMT+ bilateral activations may be due to callosal connections.
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