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Sixteen weeks of aerobic exercise does not alter resting-state connectivity of the precuneus in patients with Alzheimer's disease.

INTRODUCTION
In healthy elderly persons and patients with mild cognitive impairment, physical exercise can increase functional brain connectivity in the default mode network (DMN) measured by restingstate functional magnetic resonance imaging (rs-fMRI). However, no studies have so far investigated the effect of physical exercise on functional resting-state connectivity in the DMN in patients with Alzheimer's disease (AD).


OBJECTIVE
In a single-blinded randomized controlled trial, we assessed the effects of an aerobic exercise intervention of 16 weeks of physical exercise on DMN connectivity using rs-fMRI in patients with AD.


METHODS
Forty-five patients were randomly assigned to either a control or exercise group. The exercise group performed 60-min of aerobic exercise three times per week for 16 weeks. All the patients underwent whole-brain rs-fMRI at 3 T, at baseline, and after 16 weeks. Since the posterior cingulate cortex (PCC) and adjacent precuneus constitute a central hub of the DMN, this parietal region was defined as region-ofinterest and used as the seed region for functional connectivity analysis of the rs-fMRI data treating age and gender as covariates.


RESULTS
Neither seed-based analysis, seeded in the PCC/precuneus region nor ICA-based analyses, focusing on components of the DMN network, showed any exercise-induced changes in functional resting-state connectivity from baseline to follow-up.


CONCLUSION
16 weeks of aerobic exercise does not modify functional connectivity of the PCC/precuneus region in patients with AD. A longer intervention may be needed to show the effect of exercise on brain connectivity.