Effects of age upon auditory evoked potentials from the inferior colliculus and cortex in the guinea pig.

Auditory evoked potentials from the inferior colliculus and cortex were examined for evidence of the effect of aging in central regions of the auditory system of the guinea pig. The threshold was 25 dB higher in the responses from the inferior colliculus and 44 dB higher in the cortical potentials in old animals than in young animals. The latency of the collicular responses in the old group was greater by 1.5 ms and, in the high-frequency range, the amplitudes were smaller at all intensities tested. The latency of responses recorded from the auditory cortex in the old guinea pigs was 3.6 ms greater at threshold and the amplitudes were smaller. With stimuli well above threshold, the latency differences were no longer significant, whereas the amplitudes in old animals became significantly greater than those in the young.