The goal of this prospective open label study is to elucidate the pathophysiology of dystonia and to understand how deep brain stimulation (DBS) influences brain networks. The investigators will enroll patients with dystonia implanted with DBS of the Globus Pallidus internus (GPi) with sensing implantable neurostimulators, capable of measuring GPi local field potentials (LFPs). The main questions it aims to answer are: * does DBS influence pallidal LFPs in the long term? * how the basal-ganglia-thalamo-cortical circuit is modified after DBS? * do LFPs changes correlate with clinical improvement? Participants will undergo to serial clinical evaluations, magnetoencephalography (MEG) and functional Magnetic Resonance Imaging (fMRI) studies. Primarily, the data obtained from our study might help in clarifying basic pathological electrophysiological features of dystonia. These features might be secondarily used in future to provide a framework for an effective application of closed-loop DBS in Dystonia.