The phonological loop in medicated patients with Parkinson's disease: presence of phonological similarity and word length effects.

OBJECTIVE To test the verbal subsystem of Baddeley's working memory model (the phonological loop) in patients with Parkinson's disease. METHODS Fifteen patients with idiopathic Parkinson's disease and 15 controls were tested with a span paradigm to assess the effects reflecting the functioning of the phonological loop: the phonological similarity effect (in verbal and visual presentation), and the word length effect (in visual presentation). RESULTS AND CONCLUSIONS The patients did not show any dysfunction of the phonological loop, reflected by the presence of phonological similarity and word length effects, but had lower spans than controls. The implications of these results for the working memory model are discussed.