Verbal learning in frontal patients: area 9 is critical for employing semantic strategies

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 Parkinson’s disease patients. Thirty patients with idiopathic Parkinson’s disease and thirty normal control 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. In comparison to healthy control subjects, parkinsonian patients recalled fewer words and achieved a reduced number of categorical clusters; strategical cue did not improve their performance. This suggests, besides a difficulty in identifying the correct learning strategy, a deficit in working memory, which undermines the strategy implementation. We hypothesize that this function pertains to the dorsolateral cognitive circuit of the extrapyramidal system.