40-Hz auditory event-related potential in normal adults.

40-Hz event-related potentials (AERP) in response to 0.5-, 1-, 2- and 4-kHz tone pips were studied in 45 subjects (18 males and 27 females) in order to assess their reliability and threshold in normal adults and to study the effects of stimulus frequency and intensity on their latency and amplitude. In all subjects well-formed and reproducible 40-Hz AERP were detected, thus showing a good reliability of 40-Hz AERP to tone pips. The response was always detectable within 15 dB nHL intensity level and showed a sequence of positive (P1, P2 and P3) and negative (N1, N2 and N3) waves. It has also been observed that the latency of the first component following the acoustic stimulus decreased at increasing stimulus frequency and intensity, while the amplitude of the whole response increased upon increasing stimulus intensity. It can be suggested that the 40-Hz AERP to tone pips may represent a useful tool in assessing auditory threshold in the low-frequency range.