Affiliations: [a] Applied Neuroscience Research Group, CEITEC – Central European Institute of Technology, Masaryk University, Brno, Czech Republic | [b] First Department of Neurology, School of Medicine, Masaryk University and St. Anne's University Hospital, Brno, Czech Republic | [c] Multimodal and Functional Imaging Research Group, CEITEC – Central European Institute of Technology, Masaryk University, Brno, Czech Republic
Correspondence:
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Correspondence to: Irena Rektorova, MD, PhD, First Department of Neurology, St. Anne's University Hospital and School of Medicine, Masaryk University, Pekarska 53, 656 91 Brno, Czech Republic. Tel.: +420 543 182 639; Fax: +420 543 182 624; E-mail: irena.rektorova@fnusa.cz.
Abstract: Background:The default mode network (DMN) decreases its activity when switching from a resting state to a cognitive task condition, while activity of the network engaged in the given task increases. Visual processing is typically disturbed in Parkinson’s disease dementia (PDD). Objective:Using functional MRI, we studied the DMN effective connectivity patterns in PDD as compared with cognitively normal patients with Parkinson’s disease (PD) and healthy controls (HC) when switching from baseline to a visual cognitive task condition. Methods:In all, 14 PDD, 18 PD, and 18 age-matched healthy controls participated in this functional MRI study. We used a psychophysiological interaction analysis with the precuneus (PCu) as a seed. The threshold was set at p(FWE) <0.05. Results:The healthy controls showed greater PCu connectivity with the bilateral middle temporal/middle occipital gyri at baseline than during the task condition. The correlation direction changed from positive to negative. Both PD and PDD showed disturbed DMN connectivity with the brain regions that are involved in bottom-up visual processing. In PD, we also found impaired integration of the areas engaged in the ventral attentional network, which might reflect specific attentional deficits observed during the early course of PD. In mild PDD, we detected increased engagement of areas involved in the dorsal attentional network, which corresponds to increased top-down control in this patient group as compared to the healthy controls. Conclusion:Our results show impaired dynamic interplay between large scale brain networks in PD that spread far beyond the motor system.
