Islands of residual vision in hemianopic patients

Following damage to primary visual cortex, some patients demonstrate a limited ability to respond to stimuli they do not acknowledge seeing. This residual vision, which has been referred to as ''blindsight,'' has been attributed to secondary visual pathways. We previously reported an isolated island of blindsight in one patient and argued it was a likely consequence of cortical sparing in V1. We now report an extension of our initial findings. The data reveal a patchy distribution of residual visual abilities in the absence of acknowledged awareness. Variable patterns of cortical sparing appear to be the most parsimonious way to account for this outcome, suggesting that blindsight is generally mediated by the primary visual pathway.