Recent work has shown that the cerebellum is hyperactive in PD patients, though it is not known whether this activity is compensatory (i.e. reduces motor impairments) or pathological (i.e. causes motor impairments). One idea is that increased cerebellar activity, affecting cerebral motor areas, compensates for the reduced drive from the basal ganglia (Wu et al. 2013). Alternatively, it is possible that cerebellar hyperactivity is pathological, as recent work suggests that cerebellar activity may be partially responsible for the generation of Parkinsonian tremor (Helmich et al. 2012). One approach to answer this question is to use non-invasive brain stimulation techniques to decrease the activity of the cerebellum in PD patients and determine if they improve or worsen their gait pattern.