Role of the supplementary motor area in the automatic activation of motor plans in de novo Parkinson's disease patients.

The role of the basal ganglia-cortical motor loop in automatic and unconscious motor processes is poorly understood. Here, we used event-related functional magnetic resonance imaging in 11 de novo Parkinson's disease patients as they performed a visuomotor masked priming task. The stronger subliminal priming effect for the non-dominant side of motor symptoms than for the dominant side was paralleled by stronger supplementary motor area proper activity in response to lateralized visual stimuli presented below the threshold of awareness. This novel result supports the prediction that this area is involved in the automatic activation of motor plans as a function of striatal dopamine levels.