Two-tone interactions in inner hair cell receptor potentials: AC versus DC effects

Two-tone suppression was studied in both ac and dc receptor potentials recorded from inner hair cells in the third turn of the guinea pig cochlea. Frequency response functions for the ac component obtained at moderate intensities indicate that frequency selectivity is enhanced when a high-side suppressor is added to the stimulus. This occurs because the largest reductions in magnitude take place well above and below the characteristic frequency (CF) of the cell. Changes near CF are relatively small. In contrast, frequency response functions for the dc receptor potential become broader in the presence of an excitatory suppressor. The significance of these findings for the processing of complex stimuli is considered.