Imagine the aging brain as a bustling city with different neighborhoods, where communication is vital for smooth functioning. A new study, using the UK Biobank project’s extensive neuroimaging data, examined the impact of aging on the brain’s functional networks and their connectivity. The findings revealed a joint decline in both within-network connectivity (communication within neighborhoods) and between-network connectivity (communication between neighborhoods). These declines primarily affected functional domains like the default mode and cognitive control networks. Interestingly, enhanced connectivity occurred mainly between different functional domains, while reduced connectivity was seen not only between different domains but also within the same domain. Additionally, the study unveiled distinct changes within specific networks, such as increased connectivity in the sensorimotor network but decreased connectivity in the default mode network. These insights shed light on the complexities of brain aging and provide valuable evidence for better understanding the aging process on a whole-brain level. For more detailed information, check out the full article!

IntroductionNumerous studies have shown that aging has important effects on specific functional networks of the brain and leads to brain functional connectivity decline. However, no studies have addressed the effect of aging at the whole-brain level by studying both brain functional networks (i.e., within-network connectivity) and their interaction (i.e., between-network connectivity) as well as their joint changes.MethodsIn this work, based on a large sample size of neuroimaging data including 6300 healthy adults aged between 49 and 73 years from the UK Biobank project, we first use our previously proposed priori-driven independent component analysis (ICA) method, called NeuroMark, to extract the whole-brain functional networks (FNs) and the functional network connectivity (FNC) matrix. Next, we perform a two-level statistical analysis method to identify robust aging-related changes in FNs and FNCs, respectively. Finally, we propose a combined approach to explore the synergistic and paradoxical changes between FNs and FNCs.ResultsResults showed that the enhanced FNCs mainly occur between different functional domains, involving the default mode and cognitive control networks, while the reduced FNCs come from not only between different domains but also within the same domain, primarily relating to the visual network, cognitive control network, and cerebellum. Aging also greatly affects the connectivity within FNs, and the increased within-network connectivity along with aging are mainly within the sensorimotor network, while the decreased within-network connectivity significantly involves the default mode network. More importantly, many significant joint changes between FNs and FNCs involve default mode and sub-cortical networks. Furthermore, most synergistic changes are present between the FNCs with reduced amplitude and their linked FNs, and most paradoxical changes are present in the FNCs with enhanced amplitude and their linked FNs.DiscussionIn summary, our study emphasizes the diversity of brain aging and provides new evidence via novel exploratory perspectives for non-pathological aging of the whole brain.

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