Abstract
Previous studies have shown aberrant functional connectivity in preclinical Alzheimer’s disease (AD). However, the effects of beta-amyloid (Aβ) retention on regional functional synchronization in cognitively normal older adults still remain unclear. The aim of this study was to explore the distinctive association pattern between Aβ retention and regional functional synchronization in cognitively normal older adults. Sixty-one older adults with normal cognition underwent functional magnetic resonance imaging and regional functional synchronizations were quantified using regional homogeneity (ReHo). Subjects were dichotomized using 18F-Florbetaben positron emission tomography imaging into subjects with (Aβ+; n = 30) and without (Aβ-; n = 31) Aβ burden. The Aβ+ group exhibited significantly higher ReHo in the fusiform gyrus and lower ReHo in the precuneus compared with the Aβ- group. We found significant negative correlations between global Aβ retention and ReHo in the precuneus and medial prefrontal cortex and positive correlations between global Aβ retention and ReHo in the bilateral lingual gyrus, left fusiform gyrus, and right middle temporal gyrus in the Aβ+ group. Our findings suggest that regional functional synchronization might have distinctive association patterns with Aβ retention in the cognitively normal older adults. These findings can enrich the functional characterization of early stages of disease progression in AD.
Highlights
Resting state functional MRI reveals spontaneous neuronal activity of the human brain in the resting state and measures useful parameters in evaluating the elderly who have difficulty performing tasks[12,13]
Numerous studies have reported the detrimental effect of Aβ deposition on bimodal functional connectivity (FC) and glucose metabolism in cognitively normal older adults, no study has examined the impact of Aβ deposition on regional homogeneity (ReHo) in cognitively normal elderly[22,23]
We found that the posterior cingulate cortex/precuneus, medial prefrontal cortex, and anterior cingulate cortex had high ReHo values within each group (AlphaSim corrected P < 0.001)
Summary
Resting state functional MRI (fMRI) reveals spontaneous neuronal activity of the human brain in the resting state and measures useful parameters in evaluating the elderly who have difficulty performing tasks[12,13]. ReHo has been reported to reflect intra-regional synchronization, to reveal unpredicted regions and to be more sensitive to the default mode network than other parameters including FC17,18. In these regards, several prior studies have evaluated ReHo changes along the AD continuum. In AD patients, ReHo was decreased in the medial prefrontal cortex, bilateral posterior cingulate cortex, and precuneus, but increased in the bilateral cuneus, left lingual gyrus, and right fusiform gyrus[19,21] These regions are similar to the regions of the default mode network (DMN) and the compensatory region. We postulated that mean ReHo values would have significant sensitivity and specificity for discriminating between the Aβ+ and Aβ− groups
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