The status of blindsight: Near-threshold vision, islands of cortex and the riddoch phenomenon

In this introductory paper, we assess the current status of blindsight — the phenomenon in which patients with damage to their primary visual cortex retain the ability to detect, discriminate and localize visual stimuli presented in areas of their visual field in which they report that they are subjectively blind. Blindsight has gar- nered a great deal of interest and critical research, in part because of its important implications for the philosophy of mind. We briefly consider why this is so, and then go on to examine three empirical questions which have fuelled challenges to the validity of blindsight as a distinct neuropsychological phenomenon. First, is blind- sight simply degraded normal vision? Second, does blindsight depend on undamaged areas of primary visual cortex? Third, does evidence that blindsight patients are aware of moving stimuli undermine the apparent dissociation between access to vis- ual information and visual experience in blindsight? In the course of the review we introduce the four other papers on blindsight in this issue. We conclude that, although patients with primary visual cortex damage may indeed perceive moving stimuli, there is still good evidence for a dissociation between access to information and phe- nomenal experience which cannot be accounted for in terms of degraded normal vision or undamaged primary visual cortex.