Verbal Learning Impairment in Parkinson's Disease: Role of the Frontostriatal System in Working and Strategic Memory

Introduction: Learning is a long-term memory process, influenced by working memory control processes, including recognition of semantic properties of items by which subjects generate a semantic structure of engrams. The aim of the study was to investigate the verbal learning strategies of individuals with Parkinson's disease (PD). Methods: Thirty individuals with idiopathic PD and healthy control (HC) subjects were tested with a multi-trial word list learning, under two conditions: without cue and then with an explicit cue suggesting the categories in the list, respectively. Results: In comparison to HC subjects, individuals with PD recalled fewer words and achieved a reduced number of categorical clusters; the strategical cue did not improve their performance. Conclusion: This suggests, besides a difficulty in identifying the correct learning strategy, a deficit in working memory, which undermines the strategy implementation.