Body recognition in a patient with bilateral primary visual cortex lesions

When the primary visual cortex of a cerebral hemisphere is lesioned, the patient loses sight in the contralateral visual field. However, it has been shown that some patients are still capable of “recognizing” certain visual attributes of stimuli that are presented in their blind visual field and for which they have no conscious awareness of their presence. For example, a patient with a lesion in the right primary visual cortex and ensuing clinical blindness of the left visual field was able to discriminate above chance level the orientation of lines that were presented in his blind visual field and without acknowledged awareness of the stimuli (1). Recent neuroimaging findings in such patients reported extensive activations of extrastriate visual areas in the intact hemisphere in response to stimuli presented in the blind field (2,3), as well as the formation of new fiber connections linking intact subcortical areas in the damaged hemisphere with extrastriate areas in the intact hemisphere (4). This suggests that spared object categorization for unseen stimuli is, at least in part, mediated by striate and extrastriate visual areas along the ventral stream of the intact hemisphere. We investigated object recognition in a patient with cortical blindness over the entire visual field.