It is proposed that there are at least two categories of blindsight. One is present in visually guided behaviour in normals as well as in brain-damaged patients, while the other is present only following cortical lesions. It is also proposed that blindsight is blind because residual visual functions are banned from consciousness either when they are subserved by subcortical centres alone or when they are mediated by cortical areas that have never been exclusively associated with such functions before brain injury.

We studied patients with left visual extinction following right hemisphere damage in a simple manual reaction time task using brief visual stimuli. With unilateral lateralized stimuli the patients showed a high proportion of unwanted, reflex-like saccades to either side of stimulation. In contrast, with bilateral stimuli there was an overall decrease in the proportion of unwanted saccades, and the vast majority of them were directed toward the ipsilesional side. The implications of these results for the Findlay & Walker model are (...) discussed. (shrink)