[Effects of task load on early and late components of auditory event-related brain potentials].

Objective: To study the effects of task load on early and late components of auditory event-related potentials.
Method: The subjects were 12 healthy right-handed volunteers aged 20-23 years. The stimuli were auditory signals of two kinds of tones and appeared randomly from four speakers located on the left-front, left-rear, right-front and right-rear over the head of the subject. Tasks included: a) pressing the button in response to all signals (AR); b) making location discrimination to tones from left or right (DR); c) making location discrimination to target signals (T, high-tone or low-tone) from the four sides, and make no response to non-target signals (NT). The event-related potentials (ERPs) of three tasks were compared with each other.
Result: 1) The early components include P1, N1 and P2, and the late components include N2 (N2a/N2b), P3 and SW (slow wave). 2) P1 wave amplitude increased with the increase of the task load. N1 wave amplitude of SR(T)-ERPs decreased markedly compared with that of AR-ERPs and DR-ERPs, and P2 wave amplitude of AR-ERPs increased significantly compared with that of DR-ERPs and SR(T)-ERPs. P2 wave latency shortened with increase of the task load. 3) N2 (N2a/N2b), P3 and SW wave amplitudes increased with the increase of the task load.
Conclusion: These data indicate that not only the late components but also the early components of auditory event-related potentials were affected by task load. The effects on the late components may be related to the change of the early component (P1) which may reflect the early activity process of the brain.