Auditory Brainstem Responses to Successive Sounds: Effects of Gap Duration and Depth

Abstract

Temporal acuity is the ability to differentiate between sounds based on fluctuations in the waveform envelope. The proximity of successive sounds and background noise diminishes the ability to track rapid changes between consecutive sounds. We determined whether a physiological correlate of temporal acuity is also affected by these factors. We recorded the auditory brainstem response (ABR) from human listeners using a harmonic complex (S1) followed by a brief tone burst (S2) with the latter serving as the evoking signal. The duration and depth of the silent gap between S1 and S2 were manipulated, and the peak latency and amplitude of wave V were measured. The latency of the responses decreased significantly as the duration or depth of the gap increased. The amplitude of the responses was not affected by the duration or depth of the gap. These findings suggest that changing the physical parameters of the gap affects the auditory system’s ability to encode successive sounds.

Gap in Noise Auditory Brainstem Responses: A Systematic Review

“…Duda-Miloy et al reported that the duration of the gap has a suppressive impact on the wave V amplitude in response to post-gap noise burst [5]. On the other hand, Fan et al found that neither the duration nor depth of the gap influenced response amplitude; however, they observed a significant decrease in response latency with increasing gap duration or depth [17]. Similarly, Grose et al reported that in conditions where gaps were within-channel, shorter gap durations resulted in increased wave V latency and deteriorated waveform [16].…”

“…It is worth noting that human data was only reported up to 4000 Hz. Fan et al used a harmonic complex [17].…”

“…Signals with a length of 12 ms (n=1), 15 ms (n=2), 25 ms (n=1), 50 ms (n=4), 100 ms (n=1), and 150 ms (n=1) were used in the studies. In Allhussaini et al and experiment 2 of Fan et al, gaps of constant length were inserted between two signals, with the gap duration set at 12 ms and 5 ms, respectively [15,17]. Similarly, in Mori et al's study, the gap length was determined individually for each listener based on their gap thresholds.…”

“…The first signal consisted of ten 200 to 2 kHz harmonics at frequency intervals of 200 Hz. The second signal, referred to as the target signal, was a tone with a frequency of 1000 Hz combined with the fifth harmonic of the first signal [17]. (referred to as pre-gap) and another succeeding it (known as post-gap).…”

“…Normal hearing was defined as pure tone thresholds equal to or below 25 dBHL according to Poth et al and Aluussaini et al [4,15], equal to or less than 20 dBHL in Grose et al's study [16] and equal to or lower than 15 dBHL in Duda-Milloy et al's study at each clinical octave in the range of 250 to 8000 Hz [5]. Also in Fan et al's study, the thresholds equal to or lower than 25 dBHL in 250-8000 Hz were considered normal hearing [17]. In Werner et al's study, normal hearing status was verified through screening audiometry at octave frequencies from 500 to 8000 Hz, with thresholds set at 15 dBHL.…”