Functional imaging studies on dopamine and motor control.

In this review, the insights that PET and MR activation studies have given us concerning the role of dopamine in motor control are reviewed. Regional cerebral blood flow (rCBF) changes when normal subjects and Parkinson's disease patients perform simple finger movements, motor sequence learning, problem solving, and tasks financially rewarded according to success are compared. Additionally, dopamine release during rewarded and unrewarded actions, as reflected by relative levels of striatal binding of the reversible dopamine antagonist 11C-raclopride, are contrasted. It is argued that during unrewarded familiar actions tonic dopamine release in the basal ganglia acts to focus and filter cortical output so optimising the running of motor programmes. During motor learning, novel, and financially rewarded tasks additional dopamine is phasically released, acting to both alert the subject and to reinforce motor learning.