VISUAL-CORTEX ACTIVATION IN BLIND HUMANS DURING SOUND DISCRIMINATION

We used a whole-scalp magnetometer with 122 planar gradiometers to stu dy the activity of the visual cortex of five blind humans deprived of visual input since early infancy. Magnetic responses were recorded to pitch changes in a sound sequence when the subjects were either counti ng these changes or ignoring the stimuli. In two of the blind subjects , magnetic resonance images were also obtained, showing normal visual cortex macroanatomy. In these subjects, the magnetic responses to coun ted pitch changes were located at visual and temporal cortices whereas ignored pitch changes activated the temporal cortices almost exclusiv ely. Also in two of the other three blind, the visual-cortex activatio n was detectable in the auditory counting task. Our results suggest th at the visual cortex of blind humans can participate in auditory discr imination.