Missed connections: As people age, memory-related brain activity loses cohesion

Groups of brain regions that synchronize their activity during memory tasks become smaller and more numerous as people age, according to a study published in PLOS Computational Biology.

Typically, research on brain activity relies on average brain measurements across entire groups of people. In a new study, Elizabeth Davison of Princeton University, New Jersey, and colleagues describe a novel method to characterize and compare the brain dynamics of individual people.

The researchers used functional magnetic resonance imaging (fMRI) to record healthy people's brain activity during memory tasks, attention tasks, and at rest. For each person, fMRI data was recast as a network composed of brain regions and the connections between them. The scientists then use this network to measure how closely different groups of connections changed together over time.

They found that, regardless of whether a person is using memory, directing attention, or resting, the number of synchronous groups of connections within one brain is consistent for that person. However, between people, these numbers vary dramatically.

During memory specifically, variations between people are closely linked to age. Younger participants have only a few large synchronous groups that link nearly the entire brain in coordinated activity, while older participants show progressively more and smaller groups of connections, indicating loss of cohesive brain activity–even in the absence of memory impairment.

"This method elegantly captures important differences between individual brains, which are often complex and difficult to describe," Davison says. "The resulting tools show promise for understanding how different brain characteristics are related to behavior, health, and disease."

Future work will investigate how to use individual brain signatures to differentiate between healthily aging brains and brains with age-related impairments.

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In your coverage please use this URL to provide access to the freely available article in PLOS Computational Biology: http://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1005178

Citation: Davison EN, Turner BO, Schlesinger KJ, Miller MB, Grafton ST, Bassett DS, et al. (2016) Individual Differences in Dynamic Functional Brain Connectivity across the Human Lifespan. PLoS Comput Biol 12(11): e1005178. doi:10.1371/journal.pcbi.1005178

Funding: This work was supported by the David and Lucile Packard Foundation and the Institute for Collaborative Biotechnologies through grant W911NF-09-0001 from the U.S. Army Research Office. KJS was supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-1144085. END was supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-1656466 and the Francis Robbins Upton Fellowship in Engineering. END and KJS were additionally supported by the Worster Fellowship. DSB acknowledges support from the John D. and Catherine T. MacArthur Foundation, the Army Research Laboratory and the Army Research Office through contract numbers W911NF-10-2-0022 and W911NF-14-1-0679, the National Institute of Mental Health (2-R01-DC- 009209-11), the National Institute of Child Health and Human Development (1R01HD086888-01), the Office of Naval Research, and the National Science Foundation (#BCS-1441502, #BCS-1430087, and #PHY-1554488). The content of the information does not necessarily reflect the position or the policy of the Government, and no official endorsement should be inferred. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests: The authors have declared that no competing interests exist.

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