A direct demonstration of functional specialization within motion-related visual and auditory cortex of the human brain

Background: Physiological studies of the macaque brain have shown that there is a large expanse of visual cortex, the V5 complex, which is specialized for visual motion, and that several areas within V5 are specialized for different kinds of visual motion, In continuing work on motion-related visual cortex, we wished to chart the specialized visual motion areas in the human brain and to determine their anatomical relationship. Human subjects viewed different motion displays, and the cortical location of the increased activity produced by each stimulus was recorded. The technique of functional magnetic resonance imaging (fMRI) was used, in order to image the same subjects repeatedly. Results: We found that each of the three motion stimuli activated specific parts of the V5 complex, These sites of activation overlap with V5 and, to a smaller extent, with each other, Unexpectedly, the three motion stimuli also activated neighbouring, but nonoverlapping, regions of auditory cortex that are normally activated by the perception of speech. Conclusions: The three sites of activation produced by the visual motion stimuli occupy adjacent territories within the V5 complex. Components of the V5 complex are specifically connected to regions within auditory cortex.