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Ariella V. Popple, Stanley A. Klein, Dennis M. Levi; fMRI retinotopy in strabismic amblyopia without rotating wedges. Journal of Vision 2004;4(8):763. doi: 10.1167/4.8.763.
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© ARVO (1962-2015); The Authors (2016-present)
Retinotopy is the mapping of location in the visual field onto the cortical surface of the brain. The borders between early visual areas can be identified by retinotopy, since they occur at the foci of symmetry reversals in the polar angle plot. Amblyopia is a condition of monocular visual impairment, caused by an early mismatch between the two eyes' images, as with strabismus. It is thought to involve the active suppression of one eye's cortical representation during development. Although physiological abnormalities in primary visual cortex (V1) have been studied extensively in animal models of amblyopia, as well as post-mortem studies, less is known about the role of extra-striate visual areas. Of particular interest is the development of areas believed to sustain normal binocular vision, such as V3 and V3a. However, these areas can be hard to identify using conventional rotating-wedge stimuli for retinotopy, as strabismic amblyopes often have difficulty maintaining central fixation. We have developed stimuli that flash on and off at different times, in different parts of the visual field, following independent timeseries. Our data show that, using the anatomical segmentation of the two hemispheres as an objective reference, rotating wedges gave particularly poor retinotopy in amblyopic eyes. In contrast, few (<5%) of the visuotopic voxels were mis-assigned with our stimuli, regardless of the eye-of-origin. Using these stimuli, we hope to identify extra-striate monocular abnormalities in amblyopia.
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