PubMed1989
The latencies of the peaks in brainstem responses and the threshold response were determined in 18 healthy beagles. In the first series of measurements the dogs were sedated and the stimulus was delivered via an in-the-ear transducer. The latencies, the threshold levels, and the influence of the stimulus repetition rate on the latencies were measured. Using a miniature electric microphone in the outer ear canal near the tympanic membrane, it was found that at a level setting corresponding to 0 dB human level (HL) the major peak in damped oscillation during condensation reached a sound pressure level (SPL) of about 27 dB and the secondary rarefaction peak reached 24 dB SPL. In the second series of measurements the dogs were not sedated and the stimulus was delivered via a headphone. The wave forms, the mean latencies for peaks I to V as a function of the stimulus level, and the threshold of each wave are presented from both series. In the first series the latency values at 80 dB HL (107 dB SPL) were 1.21, 1.97, 2.67, 3.12 and 3.61 ms for peaks I, II, III, IV and V, respectively. The thresholds for peaks I to V were 47.5 +/- 9.5, 47.5 +/- 11.5, 41.3 +/- 13.0, 63.3 +/- 17.4 and 28.0 +/- 9.7 dB HL, respectively. The difference in peak latency between the first and the second series was 0.065 ms. This difference corresponded to the difference in length of the acoustic pathways.(ABSTRACT TRUNCATED AT 250 WORDS)