Non-invasive Assessment of Synaptic Plasticity

The pathophysiological mechanisms underlying Movement Disorders, including Parkinson's disease, have been related to altered synaptic plasticity affecting several structures of the central nervous system. Although several previous neurophysiologic investigations have shown abnormal long-term potentiation and depression-like plasticity in M1, other regions crucially involved in motor planning and execution, including the spinal cord, have been studied less. Parkinson's disease arises from the progressive loss of dendritic spines followed by atrophy of specific cortical (i.e. M1) and subcortical structures (i.e. putamen). These structural changes are responsible for the main clinical features of PD such as bradykinesia and rigidity. The present research project aims to probe non-invasively the main pathophysiologic mechanisms underlying altered synaptic plasticity in M1 and spinal cord and their relationship in a cohort of patients with movement disorders, including Parkinson's disease. More in detail, the investigators will use specific methodologies able to induce plasticity, including the repetitive transcranial magnetic stimulation (TMS), concerning the M1 and the focal muscle vibration, regarding the spinal cord. The neuromodulation protocol will imply 2 separate sessions, randomly scheduled to take into account the effect of the symptomatic pharmacologic treatment. Furthermore, patients will be randomly assigned to sham or real non-invasive stimulation groups. Before and after the stimulation protocol, the investigators will collect specific clinical as well as neurophysiologic measures (i.e., thresholds) according to standardized procedures. In conclusion, the goal of the study is to investigate the abnormal plasticity in the M1 and spinal cord in patients affected by specific movement disorders, through non-invasive techniques.