The function of the basal ganglia is often described in terms of which hypothesis?

• A. Brake hypothesis
• B. Acceleration hypothesis
• C. Gatekeeper hypothesis
• D. Inhibition hypothesis

Answer: (A)

The main idea being tested is that the basal ganglia function as a brake on movement. Think of them as a system that keeps motor actions in check, suppressing competing or unwanted motor programs so that the selected action can be carried out smoothly. This braking is implemented through the balance of two pathways: the direct pathway, which reduces the thalamic inhibition and helps facilitate movement, and the indirect pathway, which increases inhibition to prevent competing actions. Dopamine tunes this balance by promoting the direct pathway, effectively lowering the brake when movement is desired. Clinically, this helps explain why dopamine loss in Parkinson’s disease makes the brake too strong (leading to slowed, rigid movements) and why Huntington’s disease, with reduced braking, results in excessive, involuntary movements. While some models describe action selection in terms of gating, the brake metaphor most directly captures the idea that the basal ganglia suppress competing motor activity until the appropriate action is released.