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George E. Carvell, PhD, PT   University of Pittsburgh
 
PARKINSONíS DISEASE EFFECT ON BASAL GANGLIA CIRCUITRY
LGP = Globus Pallidus (lateral/external)
MGP = Globus Pallidus
(medial/internal)
SNc = Substantia Nigra (pars compacta)
SNr = Substantia Nigra (pars reticulata
STN = Subthalamic Nucleus
Loss of dopaminergic input to the striatum due to PD results in reduced inhibition of the Globus Pallidus (internal/medial division) and the Substantia Nigra (pars reticulata). The disinhibited GPM and SNr are driven by the subthalamic nucleus and the result is an increased inhibition of the thalamic nuclei. Inhibited thalamic neurons reduces thalamocortical drive to closed loop cortical targets of basal ganglia circuitry. 
Fig 8 In: F. Blandini, G. Nappi, C. Tassorelli, and E. Martignoni, Functional Changes of Basal Ganglia Circuitry in Parkinsonís Disease. Prog Neurobio 62: 63-88, 2000.
Fig 8 p 77