Mental flexibility in Parkinson's disease with central fatigue: Data from the frontal assessment battery

Background and aims Central fatigue is defined as a reduced energy level or an increased perception of effort, often associated to a failure in initiating and maintaining tasks that require self-motivation. It is common in Parkinson's disease population and it has been hypothesized to be related to a dysfunction in the striato-talamo- prefrontal loop. The aim of the present study was to explore the association between fatigue and executive functions as index of integrity of the striato-thalamo-prefrontal loop. Methods Twenty-nine non-demented PD patients without fatigue - PDnF, 28 non-demented PD patients with fatigue - PDF and 26 age and sex- matched controls underwent an evaluation with the Frontal Assessment Battery (FAB), MMSE, PSQI, BDI, STAI Y1-2, PDQ-39. Differences between groups in FAB scores (total and subitems) were analyzed by means of Kruskal-Wallis test. Moreover, a correlation between fatigue and FAB was also analyzed. Results Overall parkinsonian population displayed worse performance than controls in frontal scores especially inhibitory control (p = 0.008) and sensitivity to interference (p = 0.014). PDF displayed significantly worse than PDnF in verbal fluency (p = 0.05). Fatigue severity inversely correlated with executive performance (p b 0.001). Conclusions Phonemic fluency tasks are thought to reflect the simultaneous engagement of several executive functions such as attention, working memory, retrieval, information processing. The association of central fatigue with a deficit in mental flexibility, could support the hypothesis that central fatigue is a reliable index of the impairment of higher executive functions needed in order to effectively assess costs and benefits related to adaptive decision- making behavior.