Frequency specificity of the cochlear action potential varies with stimulus presentation rate

Abstract

It is well documented that the amplitude of an averaged cochlear action potential decreases as the rate of stimulus presentation is increased. In the present study, frequency regions contributing to the AP elicited by tone burst stimuli at rates from 4 to 80/s have been investigated in guinea pigs using a tone masking procedure. Derived responses corresponding to specific regions were obtained by subtracting AP responses in the presence of a low-level continuous masking tone from those in the absence of masker. This is a modification of the technique described by Hood et al. [J. Acoust. Soc. Am. Suppl. 1 81, S8 (1987)]. When stimulation rate is increased, the derived response amplitudes decreased near the probe frequency region, while amplitudes at outlying frequencies were less markedly changed. These data suggest the contribution to the AP from the region corresponding to the probe frequency becomes less at high stimulation rates. With an 80/s stimulation rate the contribution from this region is negligible. The degradation of frequency specificity of responses is presumed to arise from each stimulus acting as a “forward masker” for the following stimulus. To optimize the frequency specificity of AP responses to tone burst stimuli, the rate of presentation must therefore be considered. [Work supported by NIH.]