Short-term adaptation in single auditory nerve fibers: some poststimulatory effects

Abstract

Responses were obtained from single units of the auditory nerve of anesthetized Mongolian gerbils. Stimuli were at the characteristic frequency of the unit under study and consisted of adapting tones up to 400 ms in duration followed after a silent interval by 40 ms long test tones. The adapting exposure always reduced the response to the test tone, and the decrement in firing rate decreased exponentially as the silent interval increased, with an average time constant of 115 ms. The decrement was independent of the intensity of the test tone so that adapted and unadapted firing rates differed only by an additive constant. When adapting intensity was increased, the decrement increased in proportion to the driven response produced by the adapting tone. When adapting duration was increased, the decrement increased and depended mainly on the decay in firing rate that occurred during the adapting tone. In agreement with previous perstimulatory studies, these poststimulatory effects suggested that a static saturating nonlinearity precedes an additive adaptation process in peripheral auditory signal processing.