Context Expectations play a central role in the mechanism of the placebo effect. In Parkinson
disease (PD), the placebo effect is associated with release of endogenous dopamine in both
nigrostriatal and mesoaccumbens projections, yet the factors that control this dopamine
release are undetermined. Objective To determine how the strength of expectation of clinical
improvement influences the degree of striatal dopamine release in response to placebo in
patients with moderate PD. Design Randomized, repeated-measures study with perceived …