Brainstem auditory evoked responses to tone bursts in the echolocating bat,Rousettus

Abstract

1. Brainstem auditory evoked potentials (BAEPs) from subcutaneous electrodes were obtained from the megachiropteran echolocating bat,Rousettus aegyptiacus. 2. BAEP amplitude was measured as a function of a stimulus frequency. The lowest thresholds (defined as a 1 μV averaged response) lay between 10 and 20 kHz, and responses could be obtained from 5 to 45 kHz in most individuals (Fig. 3). Threshold increased at a rate of 30 dB/octave below 10 kHz and 40 dB/octave above 17 kHz. 3. Electrode configuration affected some components of the BAEP waveform (Fig. 1), but not the frequency response of the BAEP (Fig. 3). Pentobarbital anesthesia raised BAEP thresholds at all frequencies tested (Fig. 4), when compared with the unanesthetized state. BAEP thresholds were not affected by changes in deep rectal temperature in the range of 29–30 °C (Fig. 4). 4. Comparison of the BAEP frequency response curve with the behavioral audiogram (Fig. 6) suggests that it is an accurate predictor of the region of greatest auditory sensitivity.