Imaging the default mode network in aging and dementia

Abstract

Although in the last decade brain activation in healthy aging and dementia was mainly studied using task-activation fMRI, there is increasing interest in task-induced decreases in brain activity, termed deactivations. These deactivations occur in the so-called default mode network (DMN). In parallel a growing number of studies focused on spontaneous, ongoing 'baseline' activity in the DMN. These resting state fMRI studies explored the functional connectivity in the DMN. Here we review whether normal aging and dementia affect task-induced deactivation and functional connectivity in the DMN. The majority of studies show a decreased DMN functional connectivity and task-induced DMN deactivations along a continuum from normal aging to mild cognitive impairment and to Alzheimer's disease (AD). Even subjects at risk for developing AD, either in terms of having amyloid plaques or carrying the APOE4 allele, showed disruptions in the DMN. While fMRI is a useful tool for detecting changes in DMN functional connectivity and deactivation, more work needs to be conducted to conclude whether these measures will become useful as a clinical diagnostic tool in AD. This article is part of a Special Issue entitled: Imaging Brain Aging and Neurodegenerative disease.

Determinants of theory of mind performance in Alzheimer's disease: A data-mining study

“…Moreover, some imaging studies evidenced common cerebral activations during ToM and selfprojection in other times, places or other's mind (Buckner & Carroll, 2007;Rabin, Gilboa, Stuss, Mar, & Rosenbaum, 2010); this set of overlapping regions being related to the default mode network (Raichle et al, 2001;Spreng & Grady, 2010), a functional network particularly fragile in AD (Hafkemeijer, van der Grond, & Rombouts, 2012;Simic, Babic, Borovecki, & Hof, 2014). Taken together, these results support the need for future studies to investigate components of ToM that could be selectively impaired or preserved in AD with concomitant atrophy of these regions A number of limitations in our study warrant consideration.…”

Aging and large-scale functional networks: White matter integrity, gray matter volume, and functional connectivity in the resting state

“…Ageing has previously been associated with reduced neural activity, and we expected to find a similar reduction in resting state activity for older adults in each of the three large-scale networks (Hafkemeijer et al, 2012;Koch et al, 2010;Wu et relates directly to cognitive performance and aberrant processing (Chen et al, 2013;Fornito et al, 2012;. The lack of recruitment of FPN and SN in older adults might thus indicate that older adults do not switch between large-scale networks as readily and frequently as young adults do, which might contribute to their reduced cognitive performance.…”

Structure and function of the aging brain

“…Investigations of network changes associated with normal aging have typically implicated the default network, a collection of functionally connected brain regions including the posterior cingulate cortex (PCC), medial PFC (MPFC), inferior parietal lobule as well as medial and lateral temporal lobes [70,[108][109][110][111][112][113][114]. The default network is activated during social or internally-directed cognitive processes, including access to stored knowledge representations and experiences [65] and is typically suppressed during performance of externally-directed tasks [115].…”