Verbal learning strategies in Parkinson's disease.

Word-list learning was studied in patients with Parkinson's disease (PD) and normal control (NC) participants by means of the selective-reminding procedure of H. Buschke and P. A. Fuld (1974) in 3 learning conditions using semantically unrelated items; semantically related items, whose implicit categorical structure had to be spontaneously guessed; and semantically related items, whose explicit categorical structure was known in advance. The PD patients displayed poor learning in all 3 conditions. To identify the functional locus of the PD patients' deficits, the authors performed a stochastic Markov chain analysis, which allowed individual measurements of encoding, retrieval, and category clustering abilities. PD patients were never significantly impaired in encoding word engrams; their impairment was confined to automatic and intentional retrieval and to the ability to benefit from explicit semantic clues.