Event-related brain potentials isolate the motor component in a tapping task

Repetitive tapping is used to investigate temporal perception, memory, and reproduction. Intertap intervals and their variability, arise from cognitiv e and motor processes during the task. We used a measure of readiness poten tial onset to determine motor component latency during the timed interval. Subjects performed a paced, two-handed tapping task at four target interval s (1.5-2.75 s). Overall latency of production increased with increasing ISI , as did variability across target interval, conforming to a generalized We ber's law. In contrast, average motor latency was roughly 0.5 s across ISI. This constant motor latency may also indicate constant variability attribu table to motor processing. NeuroReport 12:3015-3018 (C) 2001 Lippincott Wil liams & Wilkins.