No visual responses in denervated V1: high-resolution functional magnetic resonance imaging of a blindsight patient.

ABSTRACT

Following severe cranio-cerebral trauma that affected the optic radiation, patient FS suffers from an incomplete macula-splitting hemianopia. Within the hemianopic field, FS exhibits blindsight, i.e. he detects and discriminates visual stimuli he cannot (consciously) see. We performed functional magnetic resonance imaging (fMRI) at high spatial resolution using a large flickering stimulus field to assess visual responsiveness of deafferented V1. Contrasting strong activation of the normal contralesional visual cortex, ipsilesional V1 displayed no stimulus-related MRI signal changes. However, activation was observed in ipsilesional extrastriate cortex. We conclude that blindsight does not depend on functional islands of tissue preserved within the deafferented striate cortex.