Fig.1.

Dopamine (DA) projections play a critical role in modulating both motor and cognitive circuits. Dopamine (DA) from neurons within the substantia nigra pars compacta and ventral tegmental area of the midbrain project to the dorsal lateral striatum of the basal ganglia and the prefrontal cortex, respectively. The earlier and more profound depletion of DA in the dorsal lateral striatum results in impairment in corticostriatal thalamic circuitry, which is important for automatic movements, and consequently greater reliance on frontal striatal circuitry, important for goal-directed motor control in Parkinson’s disease (PD). Although affected to a lesser degree, DA loss in the frontal-striatal circuit contributes to cognitive impairments in PD. Animal studies are beginning to reveal evidence for exercise-induced neuroplasticity in motor and cognitive related circuitry in PD and how the two circuits are inter-related.