Auditory N1 Component to Gaps in Continuous Narrowband Noises

In Brief Objectives: To determine whether (1) the auditory N1 component can be elicited to gaps in continuous narrowband noises, (2) psychophysical and electrophysiological gap thresholds (PGTs and EGTs) are similar to one another, and (3) EGTs are the same for all narrowband noise center frequencies. Design: PGTs and EGTs were obtained from 18 normal-hearing young-adult listeners to gaps in continuous narrowband noises with center frequencies of 0.5, 1, or 4 kHz. PGTs were obtained with a modified Békésy-type tracking paradigm, whereas EGTs were obtained to 2-, 5-, 10-, 20-, or 50-msec gaps presented every 2.2 sec. Results: (1) The auditory N1 component was recorded to gaps in narrowband noises, although they appeared morphologically different from cortical potentials obtained using the continuous broadband noise. (2) At center frequencies of 1 and 4 kHz, psychometric functions revealed close similarity between PGTs and EGTs. However, different results were present for the 0.5-kHz narrowband noise, attributed to stimulus artifact. (3) EGTs were approximately 10 msec for most participants at 1 and 4 kHz, but 20 msec at 0.5 kHz, corroborating other studies showing increases in gap threshold with lower center frequencies. Conclusions: The auditory N1 component can be recorded to gaps in continuous narrowband noises whose gap thresholds are grossly similar to those obtained psychophysically. The differences found between PGTs and EGTs with different narrowband noise center frequencies call for further investigation of narrowband noise stimuli for the study of temporal resolution. The evoked auditory N1 component to gaps in three different continuous narrowband noises was described for a group of young-adult listeners and compared with the results of a modified Békésy gap detection task using identical stimuli. N1 component grand averages suggest that gap thresholds can be obtained at 10 msec with center frequencies of 1 and 4 kHz, but a gap of 20 msec was necessary at 0.5 kHz. At 1 and 4 kHz, results between the two measures were similar but not at 0.5 kHz. Noise bandwidth and behavioral detection of spectral splatter likely explain differences at 0.5 kHz.