Dynamic functional reorganizations and relationship with working memory performance in healthy aging.

eSala-Llonch, Roser; eArenaza-Urquijo, Eider M.; eValls-Pedret, Cinta; eVidal-Piñeiro, Dídac; eBargalló, Nuria; eJunque, Carme; eJunque, Carme; eBartrés-Faz, David; eBartrés-Faz, David · 2012 · DOAJ

DOI: 10.3389/fnhum.2012.00152

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Summary

This study investigates the neural mechanisms underlying successful cognitive aging, specifically focusing on working memory performance. While aging is often associated with cognitive decline, some older adults maintain performance levels comparable to young adults. The authors sought to integrate theories of compensatory brain activity and network disruption by simultaneously examining functional connectivity and brain activity during both resting states and task performance. The research aimed to distinguish between high-performing and low-performing older adults to identify specific network reorganizations associated with preserved cognitive function. The study utilized functional MRI (fMRI) data from 29 healthy elders (mean age 62.55) and 16 young adults (mean age 21.31). Participants underwent resting-state scans and performed a verbal n-back working memory task with varying cognitive loads (0-back to 3-back). Elders were subdivided into high-performers (high-HE) and low-performers (low-HE) based on their 3-back task accuracy. Data analysis employed Independent Component Analysis (ICA) to identify intrinsic networks, specifically the Default Mode Network (DMN) and left/right Frontoparietal Networks (FPN). A dual-regression approach assessed group differences in connectivity, while region-of-interest (ROI) analyses evaluated BOLD signal changes during task execution. Results indicated distinct network patterns between groups. During resting state, low-HE subjects showed decreased DMN connectivity in frontal areas compared to young adults and high-HE subjects. Conversely, high-HE subjects exhibited decreased connectivity in the frontoparietal systems at rest. During task performance, high-HE subjects demonstrated increased activation in frontal regions, including the anterior cingulate cortex and bilateral inferior frontal gyri, particularly under moderate cognitive loads. Network analysis revealed that high-HE subjects had decreased DMN connectivity but increased connectivity within the right FPN during the task, creating a more bilateral frontal activation pattern. In contrast, low-HE subjects did not show these compensatory activations or connectivity shifts. High-HE subjects also recruited DMN regions, such as the precuneus and middle frontal cortex, during task performance, unlike young adults who deactivated these areas. The findings suggest that successful cognitive aging is characterized by a balanced and plastic reorganization of brain networks. High-performing elders compensate for age-related changes by recruiting additional neural resources, including bilateral frontal areas and DMN nodes, to maintain working memory performance. This supports the integration of compensatory theories, such as the Posterior-anterior Shift in Aging (PASA) and the Compensation-Related Utilization of Neural Circuits (CRUNCH) hypothesis. The study concludes that the ability to dynamically reorganize functional networks, rather than mere preservation of youthful patterns, underlies successful cognitive aging.

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• cognitive aging