The independency of the Bereitschaftspotential from previous stimulus-locked P3 in visuomotor response tasks.

The Bereitschaftspotential (BP) and the P3 are well-known ERPs usually observed during self-paced and externally triggered tasks. Recently, the BP was also detected in externally triggered tasks before stimulus onset. However, doubts have been raised about the authenticity of the BP in these tasks due to possible overlaps with the previous trial P3 (hereinafter s-1 P3). Here, we aim to test the authenticity of the BP in externally triggered tasks by comparing ERPs obtained during two visuomotor response tasks with different interstimulus intervals (ISIs) allowing (short-ISI; 1,000-2,000 ms) or not (long-ISI; 2,000-4,000 ms) P3-BP overlaps. In line with previous research, we hypothesize that BP and the s-1 P3 contribute independently to the scalp-detected activities during these tasks. ERPs were recorded from 14 healthy participants during the short-ISI and long-ISI visuomotor response tasks. Amplitudes and latencies of pre- (BP and pN) and poststimulus ERP components (P1, pN1, pP1, N1, pP2, dpP2, N2, P3) were compared between conditions. No effect of ISI was found on the amplitude of any pre- and poststimulus components. In contrast, longer ISI is associated with earlier onsets of the BP and pN components. In visuomotor response tasks, the BP is independent from the P3 elicited by the previous trial (s-1 P3), even using relatively short ISI. Since the different ISIs did not affect the amplitude of the BP and the P3 components, we conclude that also a short ISI can be adopted safely and conveniently to keep a reasonable duration of the overall experiment.