Effect of dopaminergic stimulation in Parkinson's disease on declarative and non-declarative memory

Ten patients with Parkinson's disease were examined using a procedural learning task and Sternberg's declarative short term memory test, under two condition's: on dopaminergic medication producing an optimal motor state, and without medication. The performance in the non-declarative task was improved, while reaction times in the declarative memory test were delayed in medicated subjects. The findings lead to the conclusion that dopaminergic medication can impair declarative short term memory even in doses producing motor improvement.