Default Mode, Executive Function, and Language Functional Connectivity Networks are Compromised in Mild Alzheimer´s Disease
Lilian H.P. Massabki,
Tatila M. Lopes,
Alexandre R. Franco,
Benito P. Damasceno,
Marcio L.F. Balthazar.
Alzheimer´s disease (AD) is characterized by mental and cognitive problems, particularly with memory, language,
visuospatial skills (VS), and executive functions (EF). Advances in the neuroimaging of AD have highlighted dysfunctions
in functional connectivity networks (FCNs), especially in the memory related default mode network (DMN).
However, little is known about the integrity and clinical significance of FNCs that process other cognitive functions than
memory. We evaluated 22 patients with mild AD and 26 healthy controls through a resting state functional MRI scan. We
aimed to identify different FCNs: the DMN, language, EF, and VS. Seed-based functional connectivity was calculated by
placing a seed in the DMN (posterior cingulate cortex), language (Broca´s and Wernicke´s areas), EF (right and left dorsolateral
prefrontal cortex), and VS networks (right and left associative visual cortex). We also performed regression analyses
between individual connectivity maps for the different FCNs and the scores on cognitive tests. We found areas with
significant decreases in functional connectivity in patients with mild AD in the DMN and Wernicke´s area compared with
controls. Increased connectivity in patients was observed in the EF network. Regarding multiple linear regression analyses,
a significant correlation was only observed between the connectivity of the DMN and episodic memory (delayed recall)
scores. In conclusion, functional connectivity alterations in mild AD are not restricted to the DMN. Other FCNs related
to language and EF may be altered. However, we only found significant correlations between cognition and functional
connectivity in the DMN and episodic memory performance.
Keywords: Alzheimer’s disease, cognition, default mode network, functional connectivity, functional networks, resting-state
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