Subjects will come for one screening visit and two outpatient study visits. During the first study visit patients will be scored clinically for dystonia and cerebellar signs. They will also undergo a structural magnetic resonance imaging (MRI) to locate the parietal target during the stimulation session. They will perform two motor learning tasks: a reaching task with visuomotor conflict and a predictive motor timing task. At least 24 hours later, during study visit two, subjects will receive TMS. TMS-induced electromyographic (EMG) activity of hand muscles will be recorded as motor evoked potentials (MEPs). Using single TMS shocks, we will measure at baseline, the input-output (I-O) curve for the right first dorsal interosseous (FDI) muscle MEPs. Then, the subjects will receive a plasticity induction protocol aiming to induce plasticity in the pathway linking the posterior parietal (PP) cortex and the primary motor cortex (M1). To that end, transcranial stimulation will be applied repeatedly (100 pairs) to the left angular gyrus in the PP cortex and to the left M1. At the end of the intervention, the I-O curve will be measured again over the next 50 minutes. The exploratory CER study will have the same experimental design. It differs from the PAR study only by the type of plasticity induction protocol used. Specifically, the cerebellum will be stimulated rather than the PP cortex.