Human Auditory Brainstem Response to Temporal Gaps in Noise

Abstract

Gap detection is a commonly used measure of temporal resolution, although the mechanisms underlying gap detection are not well understood. To the extent that gap detection depends on processes within, or peripheral to, the auditory brainstem, one would predict that a measure of gap threshold based on the auditory brainstem response (ABR) would be similar to the psychophysical gap detection threshold. Three experiments were performed to examine the relationship between ABR gap threshold and gap detection. Thresholds for gaps in a broadband noise were measured in young adults with normal hearing, using both psychophysical techniques and electrophysiological techniques that use the ABR. The mean gap thresholds obtained with the two methods were very similar, although ABR gap thresholds tended to be lower than psychophysical gap thresholds. There was a modest correlation between psychophysical and ABR gap thresholds across participants. ABR and psychophysical thresholds for noise masked by temporally continuous, high-pass, or spectrally notched noise were measured in adults with normal hearing. Restricting the frequency range with masking led to poorer gap thresholds on both measures. High-pass maskers affected the ABR and psychophysical gap thresholds similarly. Notched-noise-masked ABR and psychophysical gap thresholds were very similar except that low-frequency, notched-noise-masked ABR gap threshold was much poorer at low levels. The ABR gap threshold was more sensitive to changes in signal-to-masker ratio than was the psychophysical gap detection threshold. ABR and psychophysical thresholds for gaps in broadband noise were measured in listeners with sensorineural hearing loss and in infants. On average, both ABR gap thresholds and psychophysical gap detection thresholds of listeners with hearing loss were worse than those of listeners with normal hearing, although individual differences were observed. Psychophysical gap detection thresholds of 3- and 6-month-old infants were an order of magnitude worse than those of adults with normal hearing, as previously reported; however, ABR gap thresholds of 3-month-old infants were no different from those of adults with normal hearing. These results suggest that ABR gap thresholds and psychophysical gap detection depend on at least some of the same mechanisms within the auditory system.