Dr. High Yield Psychiatry Practice Test 2026 - Free Psychiatry Practice Questions and Study Guide

Parkinsonian motor symptoms come from degeneration of the dopaminergic neurons that project from the substantia nigra to the striatum, the nigrostriatal pathway. Dopamine in this pathway normally tunes the balance between the direct and indirect circuits of the basal ganglia to facilitate smooth, initiated movement. When nigrostriatal dopamine is depleted, the direct pathway’s activity decreases and the indirect pathway becomes relatively overactive, producing bradykinesia, rigidity, rest tremor, and difficulty with posture and movement initiation.

Other major dopamine pathways have different roles: the mesolimbic pathway is mainly about reward and motivation, the tuberoinfundibular pathway regulates prolactin, and the corticospinal tract is the primary motor pathway from cortex to spinal cord. Dysfunction in these others does not produce the classic parkinsonian motor syndrome. Treatments like L-DOPA help by replenishing dopamine in the nigrostriatal pathway, improving the motor symptoms.