Cortical-basal ganglia gamma oscillations are pathologically reduced in Parkinson's disease (PD) and the plasticity of the primary motor cortex (M1) is impaired. Enhancing gamma oscillations through transcranial alternating current stimulation (tACS), a non-invasive neurophysiological tool that modulates cortical rhythms, can restore this alteration. However, whether tACS-related normalization of M1 plasticity results in positive clinical effects is unknown. Motor learning is also impaired in PD and gamma oscillations play a relevant role in different forms of learning in humans. Nevertheless, whether motor learning abnormalities relate to reduced gamma oscillations in PD is another unclear issue. It can be hypothesized that gamma oscillations impairment in M1 contributes to altered motor control, plasticity and learning in PD. Accordingly, in this project, the authors intend to test whether gamma-tACS on M1 in PD patients ameliorates motor performance and learning, as objectively assessed with kinematic techniques.