Levodopa inhibits habit-learning in Parkinson’s disease.

Mixed dopaminergic medication, comprising dopamine agonists and levodopa, may affect habit-learning in patients with Parkinson’s disease (PD). However, the specific impact of levodopa on this effect is unknown. We assessed habit-learning in 20 non-demented PD-patients both with and without levodopa. We observed intact habit-learning in PD-patients OFF-medication. In contrast, the administration of 200 mg of levodopa impaired habit-learning. We conclude that potential deficits in habit-learning in PD may be attributed to the intake of levodopa.