Abstract
Alzheimer’s disease (AD) is a neurodegenerative disorder associated with the progressive dysfunction of cognitive ability. Previous research has indicated that the default mode network (DMN) is closely related to cognition and is impaired in Alzheimer’s disease. Because recent studies have shown that different frequency bands represent specific physiological functions, DMN functional connectivity studies of the different frequency bands based on resting state fMRI (RS-fMRI) data may provide new insight into AD pathophysiology. In this study, we explored the functional connectivity based on well-defined DMN regions of interest (ROIs) from the five frequency bands: slow-5 (0.01–0.027 Hz), slow-4 (0.027–0.073 Hz), slow-3 (0.073–0.198 Hz), slow-2 (0.198–0.25 Hzs) and standard low-frequency oscillations (LFO) (0.01–0.08 Hz). We found that the altered functional connectivity patterns are mainly in the frequency band of slow-5 and slow-4 and that the decreased connections are long distance, but some relatively short connections are increased. In addition, the altered functional connections of the DMN in AD are frequency dependent and differ between the slow-5 and slow-4 bands. Mini-Mental State Examination scores were significantly correlated with the altered functional connectivity patterns in the slow-5 and slow-4 bands. These results indicate that frequency-dependent functional connectivity changes might provide potential biomarkers for AD pathophysiology.
Highlights
Alzheimer’s disease is a progressive mental disorder associated with age and afflicts millions of elderly people with symptoms that evolve from initial memory loss to complete cognitive function decline
We investigated the altered functional connectivity patterns in four different frequency bands and the standard low-frequency oscillations (LFO) based on the default mode network (DMN) under no–task conditions in 35 patients with Alzheimer’s disease (AD) and 27 age-matched normal cognitive (NC) volunteers
In the slow-3 and slow-2 bands, the network-based statistic (NBS) shows no significant difference between the AD and NC groups in the DMN
Summary
Alzheimer’s disease is a progressive mental disorder associated with age and afflicts millions of elderly people with symptoms that evolve from initial memory loss to complete cognitive function decline. In RS-fMRI, the default mode network (DMN) is the moststudied resting state network It shows a high level of activity during rest and deactivates its performance during the cognitive tasks (Lin et al, 2011; Vidal-Pineiro et al, 2014; Raichle, 2015; Lin et al, 2016, 2017). Previous studies have demonstrated that AD patients have significantly decreased functional connectivity of the DMN and that it is closely related with cognitive dysfunction (Li et al, 2002; Greicius et al, 2004; Rombouts et al, 2005; Wang et al, 2006, 2007; Allen et al, 2007; Supekar et al, 2008; Zhang et al, 2010; Zhou et al, 2010; Balthazar et al, 2014; Toussaint et al, 2014). Recent RS-fMRI studies showed enhance connectivity in a part of the DMN region in AD patients (Zhou et al, 2010)
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