Unit responses in the cochlear nucleus of the rat to pure tones.

Abstract

AbstractThe response patterns are described of cochlear nucleus units (termed rat transient units) which only responded to a tone burst with a single discharge evoked immediately after the onset. When these cells were stimulated with bursts of repetitive clicks such units showed a marked selectivity to the click repetition rate. At a low click repetition rate one discharge was evoked for each click but this one to one relationship failed rapidly when the click rate was increased slightly above a given click repetition rate. Any additional increase in click rate resulted in only a single discharge fired immediately after the onset of a click burst and thus resembling these units' response to tone bursts. By replacing the click sounds by short bursts of pure tones presented repetitively it was shown that rat transient units were not selective to repetition rate per se, but rather, to the duration of silent interval between successive sounds. The activity of these units to click stimulation could be inhibited by broad band noise or by pure tones within certain frequency limits. Furthermore, these units showed a spectral selectivity which appeared when the stimulation was pure tones or band‐pass filtered clicks. The spectral region of highest sensitivity varied among the individual units in the range from 5 to 20 kHz and was thus widely different from the critical repetition rate for click stimulation. The latter rate was found to vary from 200 to 800 clicks per second in different units.These findings may thus explain why, in psychoacoustic experiments, repetitive presentation of short sounds results in a pitch perception which is dependent on the length of the silent period between successive sounds.