Recovery from sound exposure in auditory-nerve fibers

The discharge rate of single auditory-nerve fibers to tone bursts was measured after exposure to continuous tones. Both the exposure tone and the test tone bursts were at the fiber’s characteristic frequency. Following exposure, the discharge rate to the test bursts is transiently depressed. For moderate exposures (180 sec or less in duration and less than 80 dB SPL), the recovery of discharge rate to the preexposure level is well described by a single rising exponential. The time constant of the recovery increases as the level or duration of the exposure increases; time constant decreases as the level of the test bursts is increased. For all exposure and test conditions employed, time constants were in the range 1–30 sec. The relevance of these data to hypotheses about the mechanisms of adaptation in the auditory periphery is discussed.