The effect of varying stimulus rate and tone burst frequency on the auditory brainstem response

The auditory brainstem response (ABR) was investigated for latency change of absolute waves I, III, and V and amplitude change of wave V associated with alteration of stimulus rate and frequency. ABR's were evoked using five stimulus frequencies, 0.5, 1, 2, 4, and 8 kHz, at 6 stimulus presentation rates, 11.1, 21.1, 31.1, 41.1, 61.1, and 81.1/sec.; Comparisons of the ABR's evoked across 4 of the 5 different frequencies and 6 rates revealed significant latency shifts. The expected tonotopic relationship occurred in which the earliest responses were obtained using 8 kHz stimuli with latencies progressively increasing as stimulus frequency decreased. Latency of individual ABR components also increased as stimulus rate increased with the most significant rate effect occurring between 41.1 and 61.1/sec. With increasing rate, waves I and III became more difficult to identify. Wave V was observed at even the fastest rate across the 4 higher frequencies. Interaction between stimulus rate and frequency on wave V latency was not significant.; The amplitude of wave V was affected by stimulus frequency with the largest wave V obtained with a 2 kHz tone burst and the smallest amplitude wave V obtained with a 4 kHz tone burst. Stimulus rate did not affect the amplitude of wave V, and interaction between stimulus rate and frequency was not significant for amplitude of wave V. In the present study, the Frequency Following Response (FFR) was obtained at all rates across the nine subjects utilizing the lowest frequency, 500 Hz.