Modeling the antimasking effects of the olivocochlear reflex in auditory-nerve responses to tones in noise.

Abstract

The medial olivocochlear reflex (MOCR) has been hypothesized to provide benefit for listening in noise. The present study modeled antimasking effects in single auditory-nerve (AN) fibers [Kawase et al., J. Neurophysiol. 70, 2533–2549 (1993)]. A well-established computational model for normal-hearing and hearing-impaired AN responses [Zilany and Bruce, J. Acoust. Soc. Am. 120, 1446–1466 (2006)] was extended by using reductions in outer-hair-cell (OHC) gain to mimic the MOCR. Tone responses in noise were examined as a function of tone and noise level and OHC gain reduction. Signal detection theory was used to predict detection and discrimination for different spontaneous-rate fibers. Model results were consistent with physiological data. Decreasing OHC gain decreased the noise response and increased maximum firing rate to the tone, thus modeling the MOCR ability to decompress AN-fiber dynamic range (particularly high-spontaneous-rate fibers). For each masker level, an optimal OHC gain reduction (i.e., maximum discrimination without increased detection threshold) was found to be physiologically realistic. Thus, OHC gain reduction improved tone-in-noise discrimination even though it produced a “hearing loss” in quiet. Combining MOCR effects with the sensorineural-hearing-loss effects already captured by this AN model will be beneficial for exploring implications of their interaction for listening in noisy situations. [Work supported by NIH Grant No. R01-DC008327.]