Some temporal effects on the sensitivity of the CAP to changes in sound intensity and frequency

Abstract

The sensitivity of the compound action potential (CAP) of the auditory nerve to changes in sound intensity and frequency was obtained in anesthetized Mongolian gerbils. Detection of the change in N1 peak magnitude caused by a probe stimulus was determined using a two‐interval tracking procedure [E. M. Relkin and R. L. Smith, J. Acoust. Soc. Am. Suppl. 1 83, S98 (1988)], a technique that depends on both the N1 magnitude and its variability. The probe was added to a background sound consisting of a train of short tone bursts, and the time delay from background onset to probe onset was varied. Adaptation, i.e., the number of prior tone bursts, reduced the magnitude and variability of the CAP in response to successive background tone bursts, but did not appear to directly affect detection of the probe tone. However, detection was found to be a sensitive function of the latency between the onset of the probe and the corresponding background tone burst, particularly for probes that differed in frequency from the background. This dependency apparently resulted from variations in neural synchrony caused by cochlear travel time. [Research sponsored by NSF and NIH.]