Word-list learning was studied in patients with Parkinson's disease (PD) an
d normal control (NC) participants by means of the selective-reminding proc
edure of H. Buschke and P. A. Fuld (1974) in 3 learning conditions using se
mantically unrelated items; semantically related items, whose implicit cate
gorical structure had to be spontaneously guessed; and semantically related
items, whose explicit categorical structure was known in advance. The PD p
atients displayed poor learning in all 3 conditions. To identify the functi
onal 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 signif
icantly impaired in encoding word engrams; their impairment was confined to
automatic and intentional retrieval and to the ability to benefit from exp
licit semantic clues.