The cortical basis of global motion detection in blindsight.
The importance of stimulus qualities such as orientation, motion and luminance in blindsight are well known but their cortical basis has been much less explored. We therefore studied the performance of two blindsighted hemianopic subjects (GY and MS), in a task in which the subject had to decide in which of two adjunctive intervals a pattern of global spots moved coherently, at a variety of speeds, in the hemianopic field. Their ability was compared with that of two control subjects with normal vision. Both hemianopes performed this simple discrimination well in their blind fields but their performance was impaired by repetitive transcranial magnetic stimulation (rTMS) applied over cortical area hV5/MT(+) although not, or only slightly, by stimulation over the region of V3 or the vertex. The result is a direct demonstration that area hV5/MT(+) is necessary for global motion detection in blindsight.
Alexander
Iona
I
Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford, OX1 3UD, UK.
Cowey
Alan
A
D000222:Adaptation, Physiological / Q000502:physiology*; D000368:Aged; D019575:Blindness, Cortical / Q000473:pathology / Q000503:physiopathology*; D006423:Hemianopsia / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009039:Motion Perception / Q000502:physiology* / Q000528:radiation effects; D009473:Neuronal Plasticity / Q000502:physiology; D009483:Neuropsychological Tests; D010775:Photic Stimulation; D020127:Recovery of Function / Q000502:physiology; D013702:Temporal Lobe / Q000033:anatomy & histology / Q000502:physiology / Q000528:radiation effects; D050781:Transcranial Magnetic Stimulation / Q000009:adverse effects; D014793:Visual Cortex / Q000293:injuries / Q000473:pathology / Q000503:physiopathology*; D014794:Visual Fields / Q000502:physiology; D014795:Visual Pathways / Q000033:anatomy & histology / Q000502:physiology* / Q000528:radiation effects