Reduced resting-state brain activity in the “default network” in normal aging

TLDR

Normal aging is linked to cognitive decline, including deficits in attention, information processing, and working memory, and is thought to arise from both regional changes and altered integration of brain activity. The study aimed to investigate whether functional connectivity within the default‑mode network is affected by normal aging and how this relates to cognitive function. Using resting‑state fMRI, ten younger and 22 older adults were scanned while awake with eyes closed to assess spontaneous fluctuations in brain networks. Older adults showed reduced activity in two DMN‑like resting‑state networks compared to younger adults, a difference that persisted after gray‑matter correction and was associated with poorer executive function and processing speed.

Abstract

Normal aging is associated with cognitive decline. Functions such as attention, information processing, and working memory are compromised. It has been hypothesized that not only regional changes, but also alterations in the integration of regional brain activity (functional brain connectivity) underlie the observed age-related deficits. Here, we examined the functional properties of brain networks based on spontaneous fluctuations within brain systems using functional magnetic resonance imaging. We hypothesized that functional connectivity of intrinsic brain activity in the "default-mode" network (DMN) is affected by normal aging and that this relates to cognitive function. Ten younger and 22 older subjects were scanned at "rest," that is, lying awake with eyes closed. Our results show decreased activity in older versus younger subjects in 2 resting-state networks (RSNs) resembling the previously described DMN, containing the superior and middle frontal gyrus, posterior cingulate, middle temporal gyrus, and the superior parietal region. These results remain significant after correction for RSN-specific gray matter volume. The relevance of these findings is illustrated by the correlation between reduced activity of one of these RSNs and less effective executive functioning/processing speed in the older group.