The development of stimulus following in the cochlear nerve and inferior colliculus of the mouse

The decrement of evoked response amplitudes during the presentation of repetitive clicks was examined quantitatively at the level of the eighth nerve and inferior colliculus in mice aged 13-60 days postnatal. The amplitudes of both these potentials were found to decline during the course of stimulation, this being much more severe at the onset of hearing than in adults. Furthermore the following response at the level of the cochlear nerve was adult-like by day 18, while the response at the level of the inferior colliculus continued to improve through day 24. Recordings in the inferior colliculus were consistently obtained in two different regions along the frequency axis. The regions that responded best to a lower range of frequencies (e.g. 3-9 kHz) showed a more rapid and severe decrement in the evoked response to repetitive stimulation than those regions responding best to a higher range of frequencies (e.g. 8-17 kHz). This was found to be the case for repetitive click stimuli and repetitive tone bursts. Single unit responses in the inferior colliculus were consistent with this differential decline as a function of stimulus rate seen along the frequency axis.