Semantic disturbance for verbs in Parkinson's disease patients off medication

Word-association tasks are considered useful tools to assess the normal functioning of the lexico-semantic system in healthy people and patients suffering from neurological disorders. Parkinson's Disease (PD) patients usually present some language dysfunction related to the functioning of the semantic system as a consequence of dopamine depletion. The aim of this study was to check if there were differences in the strength of association of the words generated by a group of non-demented PD patients on and off dopamine medication using a word-association task. In the study, 20 PD patients and 20 healthy-matched controls performed a word association task consisting of 10 nouns and 10 verbs matched by psycholinguistic variables. The participants were asked to generate the first word that came to mind given a specific single target. The results revealed that PD patients off medication said words less associated with the target compared with when they were on medication. Interestingly, comparisons between PD off patients and healthy controls revealed statistical differences only in response to verbs, while differences between PD on and controls were not found. Regarding nouns, we did not find any difference between PD off or PD on and healthy controls. This experiment adds more evidence to the assumption that the lexico-semantic system is disrupted in the absence of dopamine, resulting in poor spreading activation among associative words. (C) 2013 Elsevier Ltd. All rights reserved.