Unit Responses in the Cochlear Nucleus of the Rat to Sweep Tones

Abstract

Abstract Unit discharges in the cochlear nucleus of the rat have been studied in response to stimulation with continuous tones whose frequency was changed linearly at different rates (sweep tones). At low sweep rates the distribution of discharges as a function of tone frequency was an expression of the unit's response area. When the rate of frequency change was increased the response areas of the unit became narrower. At a certain sweep rate the probability of firing, within a narrow frequency range around the units' CF, reached a maximum value which was several times greater than that found for low sweep speed. The direction of the change in tone frequency had no significant influence on the results and the average firing rate appeared to be independent of the sweep rate. These results indicate that spectral resolution of cochlear nucleus units was enhanced at a certain rate of frequency change. Additional experiments showed that the enhancement of spectral resolution at a certain rate of frequency change remains upon introduction of masking wide band noise.