Seeing without Seeing? Degraded Conscious Vision in a Blindsight Patient.
Blindsight patients, whose primary visual cortex is lesioned, exhibit 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 successfully replicate the typical findings of previous studies on blindsight. The third experiment, however, suggests that GR's ability to discriminate amongst visual stimuli does not reflect unconscious vision, but rather degraded, yet conscious vision. As our finding results from using a method for obtaining subjective reports that 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.
Overgaard
Morten
M
CNRU, Hammel Neurorehabilitation and Research Center, Aarhus University Hospital, Hammel, Denmark. neumov@sc.aaa.dk
Fehl
Katrin
K
Mouridsen
Kim
K
Bergholt
Bo
B
Cleeremans
Axel
A
D001364:Awareness; D001766:Blindness / Q000503:physiopathology* / Q000523:psychology; D055253:Color Vision; D003243:Consciousness; D006801:Humans; D010775:Photic Stimulation; D011336:Probability; D014785:Vision, Ocular / Q000502:physiology*; D014794:Visual Fields / Q000502:physiology; D014795:Visual Pathways / Q000503:physiopathology; D014796:Visual Perception / Q000502:physiology*