Figure 1.

Experimental setup. A, Experiment 1, during which participants voluntarily performed either a flexion–extension or an extension–flexion movement of the elbow: while moving up toward (up) or down far from (down) the face, they received an electrical stimulation in three preset positions: far (α1), intermediate (α2), and near (α3). B, Experiment 2 shows the pulley system used by the experimenter to induce the passive flexion–extension (up) and extension–flexion (down) movements to participants' right forearm. The electrical stimulation was delivered in the same conditions as in Experiment 1. C, Experiments 3A and 3B. In Experiment 3A, the subject kept a static position corresponding to α2 and imagined either an elbow flexion movement toward the face (up, from α2 to α3) or an elbow extension movement (down, from α2 to α1). In Experiment 3B, the subject imagined either a flexion or an extension movement starting from a static hand position corresponding to α1 (up, from α1 to α3) and α3 (down, from α3 to α1), respectively.