Abstract
An anticorrelated relationship in the spontaneous fluctuations between the default mode network (DMN) and dorsal attention network (DAN) is a robust feature of intrinsic brain organization in healthy individuals. Prior studies have reported a decreased anticorrelation between the DMN and the DAN in Alzheimer's disease (AD) and mild cognitive impairment (MCI). However, it is unclear how this anticorrelation changes as MCI progresses to AD. We hypothesized that dysfunctional connectivity between the DMN and DAN may reflect the gradual decline from MCI to AD. To test this hypothesis, we investigated alterations in functional connectivity between the DMN and DAN in subtypes of amnestic MCI (aMCI) by comparing with the same functional pattern in healthy elderly individuals and patients with AD. We retrospectively collected brain imaging and neuropsychological data from 20 AD participants, 22 participants with multiple-domain aMCI (aMCI-m), 29 participants with single-domain aMCI (aMCI-s) and 23 sex-matched normal controls in this study. Resting-state functional connectivity analysis revealed that aMCI-s and aMCI-m groups demonstrated different magnitudes of increased anticorrelation between the DMN and DAN relative to the AD group. Furthermore, in aMCI-s, aMCI-m and AD participants, hypoconnectivity was found in specific regions within the DMN, including the precuneus and angular gyrus, and hyperconnectivity was found in areas outside the typical DMN networks, including the middle occipital gyrus, lingual gyrus and visual cortex, which indicated disease-related adaptations of brain networks. Our findings suggest that DMN-DAN anticorrelation may shed light on the understanding of the adaptations in brain function during the progression from MCI to AD and may serve as a potential biomarker to detect AD in the preclinical stage.
Highlights
The early detection of Alzheimer's disease (AD) is key for postponing the development of the disease and has led people to focus on the earliest stage of the development of pathological processes, known as amnestic mild cognitive impairment, which represents a probable transitional state between normal www.aging-us.com aging and early dementia [1, 2]
Our results showed that the single-domain of amnestic mild cognitive impairment (aMCI-s) group only had decreased functional connectivity in the left angular gyrus compared with normal controls (NC), which is consistent with the definition of isolated memory impairment
We found that the AD group showed reduced functional connectivity in the right retrosplenial cortex and the right posterior cingulate cortex (PCC) within the default mode network (DMN) compared to the multiple-domain of amnestic mild cognitive impairment (aMCI-m) group and had decreased functional connectivity in the right postcentral gyrus within the dorsal attention network (DAN) compared to the amnestic mild cognitive impairment (aMCI)-s group
Summary
The early detection of Alzheimer's disease (AD) is key for postponing the development of the disease and has led people to focus on the earliest stage of the development of pathological processes, known as amnestic mild cognitive impairment (aMCI), which represents a probable transitional state between normal www.aging-us.com aging and early dementia [1, 2]. As AD progresses, gradual decline of cognitive function spreads to other domains, resulting in aMCI-m [6]. According to this view, we speculate that aMCI-s is an earlier stage of AD than aMCI-m. We speculate that aMCI-s is an earlier stage of AD than aMCI-m This hypothesis is supported by a prior study and other studies which prove a higher risk of developing into AD in aMCI-m than in aMCI-s [6,7,8]. It is necessary to understand neurodegenerative changes that occur in aMCI-s and aMCI-m to identify possible biomarkers for detecting AD in its preclinical stage
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