Aging and the auditory brainstem response in mice with severe or minimal presbycusis.

Threshold, latency, and amplitude of the auditory brainstem response (ABR) were obtained with filtered noise pips in young and aging C57BL/6J mice (to 16-months), which undergo severe progressive age-related sensorineural hearing loss (presbycusis) and CBA/J mice (to 19-months), which show only mild loss late in life. Aging per se (CBA mice) is not associated with significant changes in ABR parameters. Presbycusis, in aging C57 mice, is associated with increased thresholds; there is a trend toward increased latencies, but only when threshold elevations are substantial. Amplitudes of early waves, but not late waves, decrease greatly in aging C57 mice. In young C57 mice, amplitudes of early ABR waves vary monotonically with intensity, while amplitudes of later waves (IV and V) have a relatively flat, or even nonmonotonic, relationship to intensity; in older C57 mice, all waves have monotonic intensity functions. ABR parameters are not affected by gender in either strain. The mouse models can help to clarify some inconsistencies in the human literature on aging and the ABR.