[Detemination of the hearing characteristics of the dolphin by the evoked potential method]

The evoked potentials were recorded in the dolphin Tursiops truncatus auditory cortex with implanted electrodes. Thresholds of the responses to sounds (clicks, noises and tones) ranged from 10(-2) to 10(-3) Pa. Noises evoked potentials with the lowest threshold of about 1-10(-3) Pa. The evoked responses were elicited both by on and off sound effects as well as by change of the sound intensity or frequency. The thresholds of responses to changes of intensity were about 0.6-0.8 db (7-10%); those of responses to changes of frequency were about 0.25%. The temporal summation could be observed up to 20 msec.