Detection of temporal gaps in noise in dolphins: evoked-potential study

Temporal resolution of hearing was studied in bottlenosed dolphins by recording the auditory brain-stem response (ABR) evoked by gap in noise. Gaps shorter than 0.5 ms evoked a response combining both off- and on-components; longer gaps evoked separate off- and on-responses. Both the response to a short gap and on-response to the end of a long gap increased with increasing gap duration. On-response recovered completely at gap duration of 5-10 ms. Small but detectable response arose at gap duration as short as 0.1 ms. Contrary to the on-response after a long silence, the response to a short gap was less dependent on noise intensity. From these data, the temporal transfer function of the supposed integrator was derived assuming nonlinear transform of the integrator output to ABR amplitude. Equivalent rectangular duration of the found temporal transfer function was 0.27 ms.