The influence of noise exposure on the parameters of a convolution model of the compound action potential

摘要

The influence of noise exposure on the parameters of a convolution model of the compound actionpotential (CAP) was examined. CAPs were recorded in normal-hearing gerbils and in gerbilsexposed to a 117 dB SPL 8 kHz band of noise for various durations. The CAPs were fitted with ananalytic CAP to obtain the parameters representing the number of nerve fibers (N), the probabilitydensity function [P(t)] from a population of nerve fibers, and the single-unit waveform [U(t)]. Theresults showed that the analytic CAP fitted the physiologic CAPs well with correlations ofapproximately 0.90. A subsequent analysis using hierarchical linear modeling quantified the changein the parameters as a function of both signal level and hearing threshold. The results showed thatnoise exposure caused some of the parameter-level functions to simply shift along the signal levelaxis in proportion to the amount of hearing loss, whereas others shifted along the signal level axisand steepened. Significant changes occurred in the U(t) parameters, but they were not related tohearing threshold. These results suggest that noise exposure alters the physiology underlying theCAP, some of which can be explained by a simple lack of gain, whereas others may not.