Which structure regulates initiation and control of movement, with dopamine modulating direct and indirect pathways?

• A. Cerebellum
• B. Basal ganglia
• C. Thalamus
• D. Hippocampus

Answer: (B)

Movement regulation hinges on the basal ganglia, a group of deep brain nuclei that decide which motor programs to start or inhibit. Within this system, the direct pathway promotes movement by disinhibiting the thalamus, while the indirect pathway suppresses movement by increasing thalamic inhibition. Dopamine from the substantia nigra pars compacta acts on the direct pathway through D1 receptors to boost its activity and on the indirect pathway through D2 receptors to lessen its suppressive effect. This dual modulation tilts the balance toward initiating and smoothing purposeful movements. The cerebellum, thalamus, and hippocampus contribute to related aspects of movement or memory, but the dopaminergic control of these competing pathways is a defining feature of the basal ganglia.