Fig. 1.

Apparatus and experimental design. A: subjects were seated in front of an InMotion2 robotic arm and performed the reaching task in a horizontal plane with the right arm. B: on day 1, all subjects performed reaches in a null field (no force applied by the robot). Subjects then underwent a preobservation MRI scan session. The scan session consisted of 2 resting-state runs separated by an anatomical scan, followed by 2 functional localizer tasks. On day 2, subjects in the learning group (n = 15) observed a learning video showing a tutor adapting her reaches to a left force field (FF). A control group (n = 15) observed a control video showing a tutor performing curved reaches in an unlearnable (randomly varying) FF. Finally, all subjects performed reaches in a right FF as a behavioral test of motor learning by observing.