Fig. 1.

Sequence of events in an execution and an imagination trial. A trial started when participants pressed the two start buttons (start position). After an interval of 500 ms, the stimulus was presented. Upon identification of the target button, participants released the corresponding start button and the stimulus disappeared. Participants then executed or imagined moving to the target button, pressing and releasing it, and moving back to the start button. When participants arrived at the start button at the end of the (actual or imagined) movement they pressed it again. Imagination and execution were indicated by the color of the filled circle in the stimulus display