Procedure
Motor cortex activity was manipulated by a simple motor task
performed with the right (dominant) hand during a letter visual discrimination
task. Motor cortex activity related to hand extension was quanti-
fied by the ~20 Hz oscillations around the motor cortex exhibits two
particular periods: an activation and a “idling” state of the motor cortex
(respectively associated with the Suppression and the Rebound of the
~20 Hz oscillations; for more details see (Pfurtscheller and Lopes da
Silva, 1999; Salmelin and Hari, 1994). Because these periods were relatively
variable between participants, we determined their latency for
each participant during a preliminary independent session (simple
motor task). The dual-task session was systematically performed after
this session (a range of 1–6 days in average 2 days).
Single motor task to determine the individual suppression/rebound ~20 Hz
oscillations periods
Participants had to perform 2 blocks of 50 self-paced extensions of
the right hand at intervals of ~5 s. In order to help participants to respect
the 5 s interval between each movement, this task was preceded by a familiarization
session in which participants had to synchronize the