Auditory brainstem responses in ground squirrels arousing from hibernation

Auditory brainstem responses (ABRs) were recorded in ground squirrels (Citellus lateralis) arousing from hibernation. Squirrels implanted with recording screws to record ABRs, and a thermistor to record brain temperature, were placed in a cold room at 9 degrees C on a 2L:22D light-dark cycle. Hibernating animals were moved from the cold room and ABRs recorded during arousal. The responses showed a gradual development of all brainstem peaks. At low temperatures there were very long latencies to the peaks. The amplitudes of the peaks increased (with fluctuations) as brain temperature increased. The data indicate that neural generators on the brainstem auditory pathway were all activated early in arousal. These results do not support the hypothesis that successive peaks appear and grow in amplitude only after previous peaks are fully developed.