Sound localization: the role of the commissural pathways of the auditory system of the cat

Three main commissural pathways transmit auditory information from one side of the brain to the other. They are the trapezoid body, the commissure of the inferior colliculus and the corpus callosum. The present experiment was an attempt to determine whether one or more of these commissures are part of a neural mechanism that encodes the binaural auditory cues which enable an animal to localize sound in space. The accuracy with which cats can localize sound was determined by behavioral methods. Then in separate operations the trapezoid body, the commissure of the inferior colliculus and the corpus callosum were transected; the order of these operations varied from animal to animal. After each operation, the animal's accuracy at localizing sound was again determined. The only operations that had any effect on localization ability were those in which transection of the trapezoid body was attempted. Transection of the commissure of the inferior colliculus or of the corpus callosum, or of both, had no observable effect on localization ability. We concluded that: (1) the auditory pathways in the medulla appear to transmit information important for localization of sound, and (2) neither the corpus callosum nor the commissure of the inferior colliculus appears to carry this information.