The loss of visual function following brain injury can be highly debilitating for an individual. Typically, damage to the occipital cortex or optic radiations following a brain lesion or trauma leads to a loss of visual function in visuotopically corresponding parts of the visual field while sparing the remaining areas (e.g. half the visual field as in the case with hemianopia). This partial blindness and loss in visual function has generally been considered untreatable due to the fact that the highly specific neuronal organization underlying normal visual function is determined early in development and not regenerative particularly after the "critical period" of development has been reached. More recent evidence (including that from our laboratory) has demonstrated that a considerable degree of plasticity and reorganization of the visual system occurs not only after cerebral damage but also in adulthood, that is, well after the critical period of development has occurred. For example, evidence of spontaneous post-lesion neuroplasticity has been demonstrated in the adult visual system as documented by extensive receptive field reorganization following lesions in the retina or visual cortex (e.g. Kass 1990).