Effects of time on decremental responses of single auditory-nerve fibers

Abstract

Stimuli consisted of CF tone bursts with superimposed increments or decrements in sound intensity. The intensity changes were applied at various time delays from tone onset and the resulting changes in response firing rate were computed from PST histograms. Consistent with previous results [R. L. Smith, J. Acoust. Soc. Am. 65, 166–178 (1979)], the change in response was independent of the time delay to the change in intensity, as long as firing rates were averaged over time windows exceeding 10 ms. When the same data was analyzed using windows of less than 2 ms, the initial increment in response caused by an increment in intensity remained independent of time delay. In contrast, the initial decrement in response caused by a decrement in intensity decreased with increasing time delay and appeared to be closely related to the amount of adaptation preceding the decrement. Similar decreases were observed in the response modulation produced by amplitude-modulated stimuli. Thus, while incremental and decremental responses are basically additive, the initial portion of the decremental response appears to reflect a qualitatively different process.