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 is 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.