More youthful brain activations observed in older adults with better cognition

We investigated factors that influence the maintenance of youthful functional activation for a working memory task in healthy older adults. While task-related functional activation has been found to increase in extent and intensity in aging, there have been few investigations into the factors that enable more youthful-appearing activation patterns. Similarity to young-like templates underlying more successful cognitive aging is an attractive idea and has been operationalized in a variety of different data domains in neuroscience. We applied an operationalization of such template similarity in a well-understood verbal working-memory task examined in 135 older adults (age=64.9 {+/-} 3.17 years) using 44 younger adults (age=26.0 {+/-} 2.9 years) as the reference group. Topographic similarity to the young-reference pattern was computed as spatial correlation across voxels between a young- and an older-group pattern. Similarity to the young-reference pattern was evaluated via two approaches: group-wise and at the individual level. In group-wise similarity, moderating factors were dichotomized, splitting older adults into two group. Examining the similarity between these group patterns and the young-reference pattern, we observed more youthful-appearing activation patterns for females than males, participants with thicker than thinner cortex, less white matter hyperintensity than more, and better performance in vocabulary, processing speed, memory, and reasoning. No difference in similarity was observed for high vs. low education groups. Individual-level similarity was quantified between the young-reference pattern template and each older adults pattern, for which linear regression showed that the degree of similarity to the young pattern was associated with more accurate performance on the working-memory task, even after covarying out age, sex, education, and three brain structural measures. Overall, using a novel approach to quantify topographic similarity between younger and older adults, we provided evidence that older adults with better overall cognition recruit more youthful-appearing activation patterns during working-memory rehearsal, and we discussed its relevance to resilience mechanisms in aging.