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Parkinson’s Disease
Volume 2017, Article ID 2837685, 6 pages
https://doi.org/10.1155/2017/2837685
Clinical Study

Does Dopamine Depletion Trigger a Spreader Lexical-Semantic Activation in Parkinson’s Disease? Evidence from a Study Based on Word Fluency Tasks

1Department of Psychology, Niccolò Cusano University, Rome, Italy
2IRCCS Fondazione Santa Lucia, Rome, Italy
3Department of Systems Medicine, Tor Vergata University, Rome, Italy

Correspondence should be addressed to S. Zabberoni; ti.aiculatnash@inorebbaz.s

Received 11 May 2016; Revised 15 February 2017; Accepted 7 March 2017; Published 11 June 2017

Academic Editor: Elka Stefanova

Copyright © 2017 S. Zabberoni et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

It has been hypothesised that, in Parkinson’s disease (PD), dopamine might modulate spreading activation of lexical-semantic representations. We aimed to investigate this hypothesis in individuals with PD without dementia by assessing word frequency and typicality in verbal fluency tasks. We predicted that the average values of both of these parameters would be lower in PD patients with respect to healthy controls (HC). We administered letter-cued and category-cued fluency tasks to early PD patients in two experimental conditions: the tasks were administered both after 12–18 hours of dopaminergic stimulation withdrawal (“OFF” condition) and after the first daily dose of dopaminergic therapy (“ON” condition). HC were also given the two tasks in two conditions with the same intersession delay as PD patients but without taking drugs. Results showed that in both OFF and ON treatment conditions PD patients did not differ from HC in word frequency or typicality. Moreover, in the PD group, no significant difference was found between the experimental conditions. Our results show that semantic spreading was not altered in the PD sample examined; this suggests that in early PD the functioning of the semantic system is relatively independent from the activity of dopamine brain networks.