Overshoot measured physiologically and psychophysically in the same human ears

Abstract

A nonlinear version of the stimulus-frequency otoacoustic emission (SFOAE) was measured using stimulus waveforms similar to those used for behavioral overshoot. Behaviorally, the seven listeners were as much as 11 dB worse at detecting a brief tonal signal (4.0 kHz, 10 ms in duration) when it occurred soon after the onset of a wideband masking noise (0.1–6.0 kHz; 400 ms in duration) than when it was delayed by about 200 ms, and the nonlinear SFOAE measure exhibited a similar effect. When either lowpass (0.1–3.8 kHz) or bandpass noise (3.8–4.2 kHz) was used instead of the wideband noise, the physiological and behavioral measures again were similar. When a highpass noise (4.2–6.0 kHz) was used, the physiological and behavioral measures both showed no overshoot-like effect for five of the subjects. The physiological response to the tone decayed slowly after the termination of the noise, much like the time course of resetting for behavioral overshoot. One subject exhibited no overshoot behaviorally even though his cochlear responses were like those of the other subjects. Overall, the evidence suggests that some basic characteristics of overshoot are obligatory consequences of cochlear function, as modulated by the olivocochlear efferent system.