Brainstem auditory-evoked response in the rat. Normative studies, with observations concerning the effects of ossicular disruption.

Six young adult Sprague-Dawley rats were unilaterally cochleotomized, Brain-stem auditory-evoked responses (BAERs) to clicks and to 1-, 2-, 4-, 8- and 16-kHz tone bursts were obtained. In addition, response thresholds were estimated before and after ossicular disruption in the noncochleotomized ear of 4 animals. With increasing tone burst frequency, there was a decrease in BAER peak latencies as well as a decrease in threshold. With increasing click and tone burst intensity, there was a decrease in peak latencies and an increase in peak amplitudes. BAER peak latency/intensity functions to click stimuli ranged from -.013 to -.018 ms/dB. With increasing tone burst frequency there was a decrease in the slope of the latency/intensity function. Following ossicular disruption, BAER thresholds to clicks were elevated by an average of 49 dB. Threshold shifts to tone burst stimuli were smallest for 1- and 2-kHz tone bursts (35-36 dB) and increased with increasing frequency up to a maximum of 65 dB for 16-kHz tone bursts.