Affiliations: [a] First Department of Neurology, School of Medicine, Masaryk University, Brno, Czech Republic | [b] Applied Neuroscience Research Group, CEITEC - Central European Institute of Technology, Masaryk University, 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, Professor of Neurology, First Department of Neurology, St. Anne's Teaching 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: Changes in connectivity of the posterior node of the default mode network (DMN) were studied when switching from baseline to a cognitive task using functional magnetic resonance imaging. In all, 15 patients with mild to moderate Alzheimer's disease (AD) and 18 age-, gender-, and education-matched healthy controls (HC) participated in the study. Psychophysiological interactions analysis was used to assess the specific alterations in the DMN connectivity (deactivation-based) due to psychological effects from the complex visual scene encoding task. In HC, we observed task-induced connectivity decreases between the posterior cingulate and middle temporal and occipital visual cortices. These findings imply successful involvement of the ventral visual pathway during the visual processing in our HC cohort. In AD, involvement of the areas engaged in the ventral visual pathway was observed only in a small volume of the right middle temporal gyrus. Additional connectivity changes (decreases) in AD were present between the posterior cingulate and superior temporal gyrus when switching from baseline to task condition. These changes are probably related to both disturbed visual processing and the DMN connectivity in AD and reflect deficits and compensatory mechanisms within the large scale brain networks in this patient population. Studying the DMN connectivity using psychophysiological interactions analysis may provide a sensitive tool for exploring early changes in AD and their dynamics during the disease progression.
