A major difficulty hindering progress in our understanding of dystonia is the fact that accurate descriptions of the motor signs associated with different forms of the disease are presently lacking. Indeed, different forms of the disease yield symptoms that cannot be distinguished on the basis of current clinical evaluations. We hypothesize that the multiple pathophysiological mechanisms that appear to underlie the motor symptoms of dystonia should induce somewhat different behavioural expressions of the disease, and should also respond differently to deep brain stimulation. As proximal muscles are involved in postural limb stabilisation, we propose to not only study distal, but also proximal and contra-lateral diffusion of the motor command. Our hypothesis is that movement and EMG patterns should diverge depending on the aetiology of the disease and task conditions. In other words, we expect to identify kinematics and EMG signatures specific to different forms of dystonia.