Abstract
Research in the last few decades has brought us closer to an understanding of the brain circuit abnormalities that underlie parkinsonian motor signs. This article summarizes the current knowledge in this rapidly emerging field. Traditional observations of activity changes of basal ganglia neurons that accompany akinesia and bradykinesia have been supplemented with new knowledge regarding specific pathophysiologic changes that are associated with other parkinsonian signs, such as tremor and gait impairments. New research also emphasizes the role of non-basal ganglia structures in parkinsonism, including the pedunculopontine nucleus, the cerebellum, and the cerebral cortex, and the role of structural and functional neuroplasticity. A more detailed understanding of the brain network abnormalities that result from Parkinson's disease is necessary to arrive at more effective and specific treatments for these symptoms in parkinsonian patients through circuit interventions reaching from deep brain stimulation to genetic and chemogenetic treatments.