Altered functional brain networks in amnestic mild cognitive impairment: a resting-state fMRI study

Abstract

Amnestic mild cognitive impairment MCI (aMCI) has a high progression to Alzheimer's disease (AD). Recently, resting-state functional MRI (RS-fMRI) has been increasingly utilized in studying the pathogenesis of aMCI, especially in resting-state networks (RSNs). In the current study, we aimed to explore abnormal RSNs related to memory deficits in aMCI patients compared to the aged-matched healthy control group using RS-fMRI techniques. Firstly, we used ALFF (amplitude of low-frequency fluctuation) method to define the regions of interest (ROIs) which exhibited significant changes in aMCI compared with the control group. Then, we divided these ROIs into different networks in line with prior studies. The aim of this study is to explore the functional connectivity between these ROIs within networks and also to investigate the connectivity between networks. Comparing aMCI to the control group, our results showed that 1) the hippocampus (HIPP) had decreased FC with the medial prefrontal cortex (mPFC) and inferior parietal lobe (IPL), and the mPFC showed increased connectivity to IPL in the default mode network; 2) the thalamus showed decreased FC with the putamen and HIPP, and the HIPP showed increased connectivity to the putamen in the limbic system; 3) the supplementary motor area had decreased FC with the middle temporal gyrus and increased FC with the superior parietal lobe in the sensorimotor network; 4) increased connectivity between the lingual gyrus and middle occipital gyrus in the visual network; and 5) the DMN has reduced inter-network connectivities with the SMN and VN. These findings indicated that functional brain networks involved in cognition such as episodic memory, sensorimotor and visual cognition in aMCI were altered, and provided a new sight in understanding the important subtype of aMCI.

Functional Connectivity Disruption in Subjective Cognitive Decline and Mild Cognitive Impairment: A Common Pattern of Alterations

“…These connectivity decreases over DMN critical areas have been extensively reported (Sorg et al, 2007; Zarahn et al, 2007; Hsiao et al, 2013). In addition, MCI patients showed decreased FC between parietal regions and occipital regions consistent with recent findings reporting decreased FC between DMN regions and visual network (Cai et al, 2016). Beyond marked decreases among posterior cortical regions, MCI patients also showed increased FC over anterior-ventral areas, involving temporal and frontal structures.…”

Decoupling of inter-regional functional connectivity and regional neural activity in Alzheimer Disease

“…where the primary motor or M1 cortex resides) in AD patients. Moreover, reduced task-related FC of the SMA (Cai, et al, 2017; Zheng, et al, 2017), and a paradoxical increase in task-related FC between the SMA and M1 cortex with the sensorimotor, cingulate, and fusiform cortices (Cai, et al, 2017; Vidoni, et al, 2012), i.e. loss of local, and enhanced long-range clustering in functional connectome of the SMA, are in line with reduced CC in the precentral gyrus and SMA of MCI/AD patients in our study.…”

Negative Affectivity, Aging, and Depression: Results From the Neurobiology of Late-Life Depression (NBOLD) Study

“…ALFF is a measure that quantifies the amplitude of these low frequency oscillations [41]. Differences in ALFF in key brain regions have been noted in a variety of neuropsychiatric disorders, including major depression [42], Attention Deficit Hyperactivity Disorder [41], mild cognitive impairment [43] and psychosis [44]. We conducted seed-to-voxel rsFC analyses using 116 regions of interests (ROIs) based on the Automated Anatomical Labeling (AAL) template as seeds.…”