Some Effects of Short-Term Adaptation on Incremental Responses of Auditory Neurons

Abstract

Single units in the cochlear nuclei of anesthetized Mongolian gerbils were studied using best frequency tones. The units showed an onset peak and a decay to a steady firing rate in response to 150-msec tone bursts. As in our previous study [SMITH, R. L., and ZWISLOCKI, J. J. (1971). J. Acoust. Soc. Amer. 50, 1520–1525], 300-msec tone bursts served as pedestals upon which intensity increments were placed. The time delay from pedestal onset to increment onset was fixed at 150 msec. Total onset firing rates have been determined in response to positive and negative increments. The “adapted” response curves so obtained are approximately parallel to the “unadapted” ones measured at the pedestal onset. They are shifted along the stimulus intensity scale relative to the unadapted curves, and the shift increases with the pedestal intensity. This pattern holds for intensity levels of the pedestal up to 15 dB re the threshold of the units. At higher levels, where the pedestal responses show saturation effects, the slope and the maximum firing rate of the incremental response curves decrease.