EVIDENCE FOR A SOUND MOVEMENT AREA IN THE HUMAN CEREBRAL-CORTEX

HUMAN listeners can localize sounds by the difference in both arrival time (phase) and loudness between the two ears(1). Movement of the sou nd source modulates these cues, and responses to moving sounds have be en detected in animals in primary auditory cortex(2,3) and in humans i n other cortical areas(4). Here we show that detection of changes in t he interaural phase or amplitude difference occurs through a mechanism distinct from that used to detect changes in one ear alone, Moreover, a patient with a right hemisphere stroke is unable to detect sound mo vement, regardless of whether it is defined by phase or by loudness cu es. We propose that this deficit reflects damage to a distinct cortica l area, outside the classical auditory areas, that is specialized for the detection of sound motion, The deficit is analagous to cerebral ak inotopsia (motion blindness) in the visual system, and so the auditory system may, like the visual system(5), show localization of specializ ed functions to different cortical regions.