Differential effects of L-dopa and subthalamic stimulation on depressive symptoms and hedonic tone in Parkinson's disease.

Patients with Parkinson's disease frequently have mild to moderate depression and exhibit low hedonic tone. The authors investigate the impact of a single L-dopa challenge and the acute effects of electric stimulation of the subthalamic nucleus (STN) on symptoms of depression and hedonic tone. Depressive symptoms improved with L-dopa and STN stimulation to the same extent. However, hedonic tone improved only with L-dopa. Most of the emotional changes did not correlate with changes in motor performance, indicating they were not just reactive but specific to the treatment. These results demonstrate a single dissociation of depressive symptoms and anhedonia in response to an acute L-dopa and STN-stimulation challenge.