Three Large-Scale Functional Brain Networks from Resting-State Functional MRI in Subjects with Different Levels of Cognitive Impairment

Abstract

Normal aging and to a greater degree degenerative brain diseases such as Alzheimer's disease (AD), cause changes in the brain's structure and function. Degenerative changes in brain structure and decline in its function are associated with declines in cognitive ability. Early detection of AD is a key priority in dementia services and research. However, depending on the disease progression, neurodegenerative manifestations, such as cerebral atrophy, are detected late in course of AD. Functional changes in the brain may be an indirect indicator of trans-synaptic activity and they usually appear prior to structural changes in AD. Resting-state functional magnetic resonance imaging (RS-fMRI) has recently been highlighted as a new technique for interrogating intrinsic functional connectivity networks. Among the majority of RS-fMRI studies, the default mode network (DMN), salience network (SN), and central executive network (CEN) gained particular focus because alterations to their functional connectivity were observed in subjects who had AD, who had mild cognitive impairment (MCI), or who were at high risk for AD. Herein, we present a review of the current research on changes in functional connectivity, as measured by RS-fMRI. We focus on the DMN, SN, and CEN to describe RS-fMRI results from three groups: normal healthy aging, MCI and AD.

Applications of Resting State Functional MR Imaging to Neuropsychiatric Diseases

“…as summarized by Joo 84 . Teipel 85 summarizes studies of cortical connectivity in AD across RS fMRI, EEG rhythms and DTI-defined white matter bundles that explored interrelationships between different forms of brain connectivity.…”

Region-specific aging of the human brain as evidenced by neurochemical profiles measured noninvasively in the posterior cingulate cortex and the occipital lobe using 1 H magnetic resonance spectroscopy at 7 T

“…The PCC is the hub of the default mode network (DMN) (Leech and Sharp, 2014). The DMN is known to deteriorate during both aging (Sambataro et al, 2010, Sala-Llonch et al, 2015, Joo et al, 2016) and Alzheimer’s disease (AD) (Lustig et al, 2003, Dennis and Thompson, 2014). Metabolism and blood flow in the PCC are also impacted by AD (Boulanger et al, 2000, Kantarci et al, 2007, Hof, 2009, Leech and Sharp, 2014, Iizuka and Kameyama, 2016), possibly because of the many types of connections that the PCC has to the hippocampus.…”

Selected neuroplastic effects of cognitive training in aging in MRI/fMRI studies

“…The SN selects which stimuli are deserving of our attention and is critical for detecting behaviourally relevant stimuli and for coordinating the brain's neuronal resources in response to these stimuli. Disruptions of functional connectivity within and between these networks, including anti-correlation between the DMN and CEN, accompany normal aging (Wu et al, 2011;Joo et al, 2016). Their failure to function properly in its more severe forms can lead to numerous neuropsychiatric disorders, including dementia and Alzheimer's disease (Joo et al, 2016).…”

“…Disruptions of functional connectivity within and between these networks, including anti-correlation between the DMN and CEN, accompany normal aging (Wu et al, 2011;Joo et al, 2016). Their failure to function properly in its more severe forms can lead to numerous neuropsychiatric disorders, including dementia and Alzheimer's disease (Joo et al, 2016). The effect of cognitive training on functional connectivity of the DMN, CEN and SN was studied in a group of healthy older adults (Cao et al, 2016).…”