Seeing without seeing? Degraded conscious vision in a blindsight patient

Abstract

Blindsight patients, whose primary visual cortex is lesioned, preserved ability to discriminate visual stimuli presented in their "blind" field, yet report no visual awareness hereof. Blindsight is generally studied in experimental investigations of single patients, as very few patients have been given this "diagnosis". In our single case study of patient GR, we ask whether blindsight is best described as unconscious vision, or rather as conscious, yet severely degraded vision. In experiment 1 and 2, we succesfully replicate the typical findings of pervious studies on blindsight. The third experiment, however, suggests that GR's ability to discriminate amongst visual stimuli does not reflect unconcious vision, but rather degarded, yet concious vision. As our finding results from using a method for obtaining subjective reports tha has not previously used in blindsight studies (but validated in studies of healthy subjects and other patients with brain injury), our results call for a reconsideration of blindsight, and, arguably also of many previous studies of unconscious perception in healthy subjects. © 2008 Overgaard et al.