Single unit responses in the auditory cortex of Rhesus monkeys during a sound localization task

Abstract

Behavioral studies have suggested that the auditory cortex plays an essential role in the localization of sound in space. The present study investigated how single units in the auditory cortex (koniocortex and adjacent belt areas) respond to sound sources that an animal is required to localize. Sound stimuli 100 ms in duration were presented randomly from one of five speaker locations within arm's reach of the monkey. In the localization condition animals were trained to press a key on the speaker which had presented the sound. Unit activity in the localization condition was compared to that recorded in another condition, the detection condition, in which the animals pressed a single key whenever a stimulus was presented regardless of its location. Approximately 5% of the units had significantly greater evoked activity in the localization condition than in the detection condition. The type of response pattern and spontaneous activity remained the same. Most of the recorded units were differently responsive to sound location. Generally there was a gradual increase in evoked activity as the sound source was changed from ipsilateral to contralateral speaker locations.