Increased Functional Connectivity and Brain Atrophy in Elderly with Subjective Memory Complaints

Abstract

Subjective memory complaints (SMC) are common among elderly. Although subtle changes in memory functioning can hardly be determined using neuropsychological evaluation, neuroimaging studies indicate regionally smaller brain structures in elderly with SMC. Imaging of resting-state functional connectivity is sensitive to detect changes in neurodegenerative diseases, but is currently underexplored in SMC. Here, we investigate resting-state functional connectivity and brain structure in SMC. We analyzed magnetic resonance imaging data of 25 elderly with SMC and 29 age-matched controls (mean age of 71 years). Voxel-based morphometry and volume measurements of subcortical structures were employed on the structural scans using FSL. The dual regression method was used to analyze voxel-wise functional connectivity in relation to eight well-characterized resting-state networks. Group differences were studied with two-sample t-tests (p<0.05, Family-Wise Error corrected). In addition to gray matter volume reductions (hippocampus, anterior cingulate cortex (ACC), medial prefrontal cortex, cuneus, precuneus, and precentral gyrus), elderly with SMC showed increased functional connectivity in the default mode network (hippocampus, thalamus, posterior cingulate cortex (PCC), cuneus, precuneus, and superior temporal gyrus) and the medial visual network (ACC, PCC, cuneus, and precuneus). This study is the first which demonstrates that, in addition to smaller regional brain volumes, increases in functional connectivity are present in elderly with SMC. This suggests that self-reported SMC is a reflection of objective alterations in brain function. Furthermore, our results indicate that functional imaging, in addition to structural imaging, can be a useful tool to objectively determine a difference in brain integrity in SMC.

Sleep changes without medial temporal lobe or brain cortical changes in community‐dwelling individuals with subjective cognitive decline

“…In fact, many studies suggest that SCD might be the expression of AD-related brain changes that have already occurred in the MTL [20–27] or in other brain cortical regions [23,27]. However, although some MRI studies found MTL and/or cortical differences between SCD and controls [20–27], other studies failed to find these differences [20,27,28].…”

Chronology and Chronicity of Altered Resting-State Functional Connectivity after Traumatic Brain Injury

“…47 Hippocampal hypersynchrony with proximal regions and/or other regions of the DMN has been noted in risk groups for AD, including individuals positive for the apolipoprotein Ee4 allele [86][87][88] and mild cognitive impairment (MCI) patients 89,90 as well as individuals with early AD itself. 48 Similarly, increased resting-state connectivity between the PCC and other DMN regions has been noted in elderly individuals with elevated regional brain atrophy and memory complaints, 91 in MCI, 47,92,93 and in the very early stages of AD. 85,94,95 The concordance between the current results and those in neurodegenerative disease orients us to the potential consequences of TBIinduced network changes on long-term neurological status.…”

A Longitudinal Study on Resting State Functional Connectivity in Behavioral Variant Frontotemporal Dementia and Alzheimer’s Disease

“…We used standard resting state networks as a reference to study functional connectivity in a standardized way [39,40]. Resting state functional connectivity was determined in terms of similarity of the BOLD fluctuations in the brain in relation to characteristic fluctuations in the predefined resting state networks [41,42].…”