1. Study Rationale: Epidemiological studies report that 85% of stroke survivors show hemiparesis and a percentage ranging from 55% to 75% report upper limb functional impairment. Early rehabilitation in stroke patients with motor disorders can be effective to restore the affected function and to improve the performance of daily activities. Up to now, different methods and techniques have been used to recover motor functions in stroke patients, including motor training (active or passive mobilization) for the paretic limb, functional electrical stimulation, Constraint Induced Movement Therapy (CIMT) and robot-assisted rehabilitation. However, none of these has been conclusively proven to be more effective than the others. The clinical benefits induced by motor rehabilitation are closely related to "neuroplasticity", i.e. the ability of the central nervous system (CNS) to undergo structural and functional changes in response to physiological events, environmental stimuli and pathological events. After brain injuries, neurorehabilitation should aim at recovering functions and not vicariate them. In this context, observation and imitation of actions can recruit the mirror neuron system. Mirror neurons found both in the premotor cortex and parietal lobe, discharge both during the execution of a goal-directed action and the observation of the same or a similar action when performed by another individual. Electroencephalography (EEG) and Magnetoencephalography (MEG) studies showed that when an individual observes hand actions there is a desynchronization of the motor cortex similar, although weaker, to that occurring during actual execution of the observed movements. By means of Transcranial Magnetic Stimulation (TMS) it has been shown that motor-evoked potentials recorded from hand muscles increase during the observation of hand movements. Brain imaging studies showed that during the observation of actions performed with different biological effectors ( hand/mouth/foot), there is an activation of the ventral premotor cortex including Broca's region somatotopically organized. Thus, the motor system may be activated during action observation in the absence of overt movements. Based on this experimental evidence it has been suggested that action observation may be exploited as a rehabilitative approach even when patients can't perform motor output. Action observation treatment has been proven to be effective also in the rehabilitation on Parkinson's disease patients, in children with cerebral palsy, and orthopedic patients with hip/knee replacement.