Tim Martin, Assistant Professor
Department of Psychology
Kennesaw State University
Lecture Title: Mechanisms of visual restoration in hemianopia/quadrantanopia
Abstract: Post-chiasmal brain lesions often cause loss of vision in one quarter to one half of the visual field. By the third month post-lesion, further recovery is generally considered impossible because the pathway from retina to primary visual cortex is irreparable, and according to the classical model of visual neuroanatomy, this pathway is the sole carrier of most visual information to the cortex. Rehabilitation therefore focuses on the development of compensatory strategies to cope with disability, rather than restoration of function. Recent discoveries in neuroanatomy, adult plasticity, and perceptual learning, along with limited success in several paradigms of aggressive visual retraining, provide ample reasons to challenge this view of post-chiasmal vision loss. This study seeks to inform the possible mechanisms of recovery in one retraining paradigm, motion direction discrimination training. Using fMRI, brain responses to motion stimuli were assessed pre- and post-training in a small sample of hemianopes and quadrantanopes. Post-training, activity increased in perilesional cortex relative to pre-training levels, and this effect paralleled behavioral improvements. The effect was limited to retrained regions of the blind visual field, ruling out spontaneous recovery.