Brainstem auditory evoked response in the ferret (Mustela putorius).

The effect of click intensity, repetition rate and binaural interaction on the brainstem auditory evoked response (BAER) was examined in sixteen pigmented adult male ferrets. Potentials were recorded from platinum needle electrodes inserted over the vertex and left and right mastoids. Square waves, 100 microseconds in duration, were transduced by earphones enclosed in an assembly designed to fit securely over the ferret's external ear. The BAER in the ferret consists of four prominent vertex-positive peaks (P1-P4) and a fifth peak of smaller amplitude and more variable latency. The mean latencies of P1-P4 at 104 dB peak SPL were 0.96, 1.83, 2.75 and 3.62 ms. Reducing intensity over a 70 dB range resulted in a reduction in amplitude and a corresponding increase in latency ranging between 0.57 and 0.67 ms. Also, increasing click repetition rate resulted in a reduction in amplitude and an increase in latency. With intensity fixed at 104 dB peak SPL comparison of latencies at 10 and 50/s showed a mean increase of 20, 50, 60 and 80 microseconds for P1-P4, respectively. The effect of binaural interaction on the BAER was examined using the procedure of Dobie and Berlin (1979); the response evoked by binaural stimulation was subtracted from the summed left and right monaural responses to obtain a binaural interaction component. Binaural interaction in the ferret gave rise to a distinct vertex-negative wave with a latency similar to P4. An increase in click intensity over a 70 dB range resulted in a monotonic increase in amplitude and a decrease in latency of the binaural interaction component.