S. H. Ridgway
D. A. Carder
Biosci. Div., Naval Command, Control and Ocean Surveillance Ctr., RDTE Div., Code 5107B, 49620 Beluga Rd., Rm. 200, San Diego, CA 92152
Brain-wave activity (EEG) even at minute levels recorded from the dolphin head surface may be processed in synchrony with sound to reveal an auditory-evoked potential (AEP). AEPs can provide objective information about the auditory system and many features are consistent across species so that experience with common laboratory animals and humans may be of help in evaluating responses. Although AEPs do not require a behavioral response, they may be compared with behavioral responses as sound is attenuated toward threshold. Some components of the AEP are unaffected by level of consciousness, allowing their use to evaluate hearing in sleeping infants and to determine brain damage or brain death. Auditory thresholds, and related information such as temporary threshold shifts, are critical for evaluating the potential impacts of ocean noise pollution on marine animals. Most species that are of concern, such as the great whales will not likely be brought into the laboratory so that their auditory system can be studied; however, many opportunities exist for brief studies when such animals become stranded or entrapped. Physiological studies, including AEPs, could go a long way toward providing critical information needed to define some limits for safe noise exposure for marine animals.