Examining enhancement conditions with an auditory nerve model

Abstract

Psychophysical studies have shown that the ability to detect a signal in a masker may be improved by presenting a preceding sound (precursor) identical to the masker, an effect called overshoot. When the masker has no spectral notch around the signal frequency, overshoot has been predicted using a physiologically-realistic auditory nerve (AN) model in which gain is reduced by the precursor. This may simulate the medial olivocochlear reflex (MOCR). When there is a spectral notch in the masker at the signal frequency, the resulting improvement in signal detection is sometimes called enhancement. It has been suggested that enhancement may be due to adaptation of suppression, which could be related to gain reduction in the cochlea, or to adaptation of inhibition, which could occur more centrally. Physiological studies of the AN have shown either no adaptation of suppression [Palmer et al., J. Acoust. Soc. Am. 97, 1786-1799] or a reduction in suppression when the MOCR was elicited [Kawase et al., J. Neurophys. 70, 2533-2549]. The purpose of the present experiment is to use the AN model to investigate the relationship between gain reduction and suppression with stimuli used in previous studies of enhancement. [Research supported by NIH(NIDCD) R01 DC008327]