Objective: To determine if Parkinson’s disease causes an impairment in the ability to consolidate learning into long-term memory and to determine if this deficit is dopamine-dependent.

Background: Loss of dopamine in Parkinson’s disease has been associated with reduced plasticity but little is known about the behavioral and cognitive consequences of this reduced plasticity. One important role of plasticity is the consolidation of learning into long-term memory. In this study, we aimed to identify whether Parkinson’s disease, and specifically dopamine loss, lead to reduced consolidation of learning. Indeed, it is widely accepted that dopamine plays an important role in multiple aspects of learning and that Parkinson’s patients have a learning deficit, but dopamine’s role in the consolidation of learning is not well understood.

Methods: We used a task that measures two types of learning: probabilistic incremental learning and episodic memory. To test the effect of Parkinson’s disease and dopamine on the consolidation of incremental learning and episodic memory, we tested healthy controls and participants with Parkinson’s disease, either ON or OFF their dopaminergic medications. Consolidation was measured by testing the persistence of learning at two time points across a two-day delay.

Results: Initial learning was similar among Parkinson’s patients and controls, but Parkinson’s patients showed weaker consolidation than controls for both incremental learning and episodic memory. Early results also suggest that dopamine replacement at the time of initial learning improved consolidation of incremental learning. This effect was not seen for episodic memory.

Conclusions: These findings suggest that Parkinson’s patients have weaker consolidation of both incremental and episodic memory, but that dopamine might play a selective role in the consolidation of certain types of learning. Future work is needed to determine whether weaker consolidation in Parkinson’s patients can be linked more generally to reduced plasticity and whether therapies thought to influence plasticity, such as deep brain stimulation, can also have beneficial effects on consolidation processes.

Parts of the data described here were presented at the Society for Neuroscience meeting in October 2015.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/consolidation-of-learning-and-memory-in-parkinsons-disease/