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Action potentials were recorded from single neurons in auditory cortex on the supratemporal plane in 10 hemispheres in nine monkeys (macaca mulatta). Each monkey was trained to sit quietly in a chair with its head restrained. Pure tones were delivered monaurally or binaurally through rubber ear molds that fitted tightly into each external auditory canal. When one ear is stimulated, the number of spikes and the firing pattern depend upon the position of the stimulus within the response area of the cell. For most neurons, spike count is a nonmonotonic function of SPL. Commonly, neurons discharge a train of spikes throughout a tone of several hundred milliseconds duration at suprathreshold levels at best frequency. A few cells adapt quickly and discharge only a few spikes at onset of the tone. Others are inhibited by the tone or are excited only at the termination of the sound. When tones are delivered binaurally, the number of spikes and their temporal order are very sensitive to small interaural differences in SPL. At low frequencies, spike count is a periodic function of differences in time of arrival of the stimulus at the two ears. Neurons can have a characteristic delay. Within a given penetration, phase-sensitive neurons with very similar best frequencies and spike-count functions can have very different firing patterns.

©1973 Acoustical Society of America