Visual responses from cells in striate cortex of monkeys rendered chronically 'blind' by lesions of nonvisual cortex.

Chronic 'blindness' can be produced in monkeys by a large cortical removal that spares modality specific visual cortex (striate, prestriate, and inferior temporal cortex). To understand the reasons for the blindness we compared single unit activity recorded from striate cortex of these monkeys with the activity of units recorded from seeing animals. The results indicate that visual processing in the striate cortex of the blind monkeys, with the exception of changes attributable to a partial disruption of the geniculostriate pathway, is similar to that of the normal monkeys. The chronic blindness is therefore probably due not to dysfunction within striate cortex but rather to a disconnection from critical processing stages within the ablated territory. Feedback from this territory is apparently not necessary for information processing to occur in striate cortex.