Figure 1.

A, Illustration of the workspace and task. Participants were instructed to perform forward reaching movements toward a visual target. An open goal target was presented for a random delay uniformly distributed between 2 and 4 s before it was filled in. The cue to reach the target was given by filling in the goal in red. The goal was turned red if the time between the go signal and the stabilization in the target was comprised between 0.6 and 0.8 s. B, Hand paths from the first force field trials (top) and trial #25 selected for illustration (bottom) from each participant (n = 18). Counterclockwise and clockwise perturbations are depicted in blue and red, respectively. The black traces illustrate for each panel baseline trials selected randomly (one baseline trial per participant). Osh.: target overshoot; Max.: maximum displacement in the direction of the force field; Thresh.: the positional threshold used to align EMG data. C, Maximum displacement in the direction of the force field. The dashed trace illustrates that the exponential fit did not reveal any significant curvature across force field trials (p > 0.05). D, Maximum target overshoot in the direction opposite to the force field. Solid traces revealed strongly significant exponential decay across trials (p < 0.001).