Unilateral damage to the adult primary visual cortex causes a loss of conscious vision over contra-lateral parts of the visual field in both eyes. Such partial cortical blindness hinders every aspect of daily life, including reading, navigation, and driving. While visual rehabilitation for this condition has been controversial, the existence of residual visual processing abilities in cortically blind fields (commonly known as a??blindsighta??) suggests that it might be possible to recover vision though perceptual training. Our laboratory has focused on retraining motion perception, studying the properties of recovered vision psychophysically and using fMRI. To date, we have shown that discrimination of both simple and complex, moving visual stimuli can be retrained back to normal levels of threshold performance in cortically blind fields. Testing with controlled fixation shows that the recovered abilities are localized to retrained visual field locations, but generalize to discrimination of untrained (including non-motion) stimuli and tasks. Supporting this broad generalizability of re-learning, fMRI data suggest that visual training in cortically blind fields may not just recruit brain circuits mediating blindsight. Instead, altered activity in spared early and higher-level visual areas points to largely canonical routes of visual processing as the substrates of recovered vision.
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