Inner hair cell responses to tonal stimulation in the presence of broadband noise.

The effects of broadband noise (BBN) on the tone-evoked de receptor potential from inner hair cells of guinea pigs were measured. The effects of the noise were: suppression of the receptor potential, no net change, or greater depolarization relative to the tone alone, evoked receptor potential. The effects appear to be consistent with a two-tone suppression hypothesis. The time course of the suppression effect is immediate and constant in time. This observation suggests no obvious involvement of a local feedback loop in outer hair cells or one depending on the efferent nerves. Inner hair cell "sensitivity" is a variable in the magnitude of the suppression. Comparison of masked, tone-evoked de receptor potential intensity functions to responses from auditory-nerve fibers (taken from the literature for experiments using a similar paradigm) differentiates the phenomena of suppression and adaptation in the auditory periphery.