Figure 1. Experimental conditions.

In both INTRA- and INTER-manual condition subjects felt the orientation of a kinesthetic target and reproduced it by prono-supinating the hand (blue arrows). Subjects never saw their hand, thanks to a virtual reality system. Whilst in the INTRA condition the subject sensed the target and reproduced the orientation with the same (right) hand, in the INTER condition targets were sensed with the left and reproduced with the right. To detect the use of visual representation of the task, in some of the trials the virtual scene imperceptibly rotated with respect to gravity (red arrows).