Intensity and rate functions of cochlear and brainstem evoked responses to click stimuli in man

Abstract

The complex of five waves, which are the responses to click stimuli of the auditory nerve and the brainstem auditory nuclei, were recorded in ten human subjects by means of earlobe and scalp electrodes. The rate of the stimuli was varied from 5/s to 80/s and their intensity was varied over a 70 dB intensity range in order to study the rate and intensity functions of each of the response components. With increasing click intensity, the amplitude of the first wave (generated by the auditory nerve) increased proportionally while the amplitudes of the later waves (generated by the brainstem auditory nuclei) reached their maximum amplitudes at intermediate click levels (saturation), and at high intensities occasionally even decreased in amplitude. The latency of each of the waves decreased by similar amounts as the intensity was increased. With increasing click rates, the amplitude of the first wave decreased the most, while there were smaller effects on the amplitude of the later waves. There was no effect of click rate on the latency of the first wave, but the latency of the later waves increased with click rate, the effect being greater on the later waves. In the rate functions, the latency change of a wave was greater than that of the waves preceding it (accumulative effect). These results are explained by overlapping convergence and divergence in the ascending auditory pathway. These results support the notion that the principal component of each wave is activated by the principal component of the previous wave. These results may explain the relative ease with which several workers record the fourth wave of the complex, and their preference for this response.

Brainstem Auditory-Evoked Potentials Studied with Paired Stimuli in Multiple Sclerosis Patients

“…Waves I and II did not show a significant latency differ ence between single-and paired-click stimulation (PCI 4.0 and 1.5 ms). These findings in MS patients are simi lar to those in normal subjects [4,13]. Comparing the responses to paired stimulation with a PCI of 1.5 and 4 ms, wave III was only significantly delayed with a PCI of 1.5 ms [4] in normal subjects.…”

Effects of Click Intensity and Frequency on the Brain-Stem Auditory Evoked Potentials in the Common Marmoset (Callithrix jacchus).

“…The amplitudes of waves I (32 and 99 kHz) and II (32 kHz) became larger as the stimulus intensity was increased from 50 to 70 dB pe SPL, and then decreased as the stimulus intensity was further raised from 70 to 100 dB pe SPL. It has also been reported that wave amplitudes are rarely influenced by intensity changes or decreased as the stimulus intensity was increased because of the saturation of the response [7,36].…”

“…The prolongation of BAEP latencies with progressive decreases in stimulus intensity have previously been observed in response to click stimuli in various laboratory animals and in humans [18,39]. The range of latency increase per decibel (dB) was approximately 6-14 µsec/dB in common marmosets, whereas it was the 8-18 µsec/dB in rats [5,10], 8-28 µsec/dB in dogs [37], 12-53 µsec/dB in monkeys [35], and 35-56 µsec/dB in humans [16,18,36]. The reason why common marmosets have a shorter range of latency increase per dB may be the result of stimulation at higher click frequencies.…”

Mathematical Expression of Relationship Between Auditory Brainstem Transmission Time and Age

“…However, the absolute latency of an ABR wave may vary as a function of stimulus intensity (Pratt and Sohmer 1976), stimulus repetition rate (Hyde et al 1976, Pratt and and stimulus frequency (Brama and Sohmer 1977). In addition, a conductive hearing-loss also gives rise to increased absolute response latencies (Sohmer and Cohen 1976).…”