The Impact of Age-Related Changes on Working Memory Functional Activity

Steffener, Jason; Brickman, Adam M.; Rakitin, Brian C.; Gazes, Yunglin; Stern, Yaakov · 2009 · OpenAlex-citations

DOI: 10.1007/s11682-008-9056-x

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Summary

This study investigates the relationship between age-related structural brain changes and functional neural networks involved in working memory, specifically testing the neural compensation hypothesis. The authors sought to determine whether older adults recruit additional neural resources to maintain performance in the face of age-associated grey matter atrophy, or if such recruitment represents a detrimental dedifferentiation of brain function. The researchers analyzed data from 37 young adults (mean age 25) and 15 older adults (mean age 74) performing a delayed item recognition task while undergoing functional magnetic resonance imaging (fMRI). Structural integrity was assessed using voxel-based morphometry (VBM) on T1-weighted anatomical images. Multivariate Linear Modeling (MLM) was employed to identify load-dependent functional networks. Two distinct networks were identified during the retention phase: a primary network (Network 1) utilized by both groups, and a secondary network (Network 2) significantly expressed only by older adults. The study examined associations between the expression of these networks, whole-brain volume, and regional grey matter volume, particularly within the primary network. Results indicated that older adults had significantly lower normalized whole-brain volume than younger participants. Crucially, global volume loss was not associated with the expression of the secondary network. However, decreased regional grey matter volume in the left pre-central gyrus (part of the primary network) was significantly associated with increased utilization of the secondary network, independent of age group. Behaviorally, increased expression of the secondary network in older adults was associated with a steeper increase in reaction times as memory load increased, though accuracy remained high. This suggests that while the secondary network helps maintain accuracy, it comes at the cost of slower processing speed. The findings support the neural compensation hypothesis. The recruitment of the secondary network appears to be a compensatory mechanism triggered by specific structural deficits in the primary working memory network, rather than a global response to whole-brain atrophy. The association between regional grey matter loss in the left pre-central gyrus and secondary network activation indicates that older adults mobilize extra resources to offset localized structural decline. This study clarifies that age-related functional reorganization is not merely a non-specific consequence of aging but is specifically linked to regional structural integrity, providing evidence that neural compensation serves to preserve cognitive performance despite underlying neurobiological changes.

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• cognitive aging