Auditory nerve and brain stem volume-conducted potentials evoked by pure-tone pips in the CBA/J laboratory mouse

The short latency (less then 10 ms) auditory nerve and brain stem evoked potentials of Jewett were examined in the inbred CBA/J laboratory mouse. Tone pips, at nine frequencies from 4 to 64 kHz, were used to determine auditory nerve evoked potential (P1) thresholds. Maximum sensitivity occurred at 32 kHz, and a second sensitive area was seen at 56 kHz. With the exception of 32 kHz, as stimulus frequencies were increased in octave intervals, the 90 dB P1 amplitude also increased. P1 latency decreased as the stimulus frequency was increased up to 32 kHz, but this trend reversed with further increases of frequency. However, the P1 amplitude-latency function produced a better agreement of latency and frequency with the travelling wave theory for amplitudes less than 1 micro V, while amplitudes from 2 to 8 micro V were independent of frequency. Latency and amplitude input-output functions for responses from the four auditory brain stem loci suggest that auditory information is differentially processed as a function of frequency at each level, This is especially true for the inferior colliculus, which is most sensitive to 8-KHz stimuli.