Phase-locked response to low-frequency tones in single auditory nerve fibers of the squirrel monkey.

Abstract

Responses of auditory nerve fibers to pure tones were studied in 25 squirrel monkeys. In a response to a tone of low frequency the discharges were spaced at intervals grouped around the integral multiples of the period of the stimulating tone regardless of the frequency or intensity of an effective stimulus. The cadence of the stimulus cycles possibly determines the phase-locked response. Locking of the discharges to the stimulus cycle was demonstrable up to 4500 to 5000 cps. Probability of stimulus cycle being effective in producing a discharge can be satisfactorily estimated by dividing the number of discharged spikes by the number of cycles delivered. For a given stimulus duration and the same discharge rate the probability of a cycle being effective was nearly a linear function of the period. If frequency and stimulus duration were constant probability of discharge was. within dynamic range of the unit, a monotonic function of stimulus strength which approximated a power function.