Older brains are not all alike: Individual differences in brain activation patterns during working memory performance

Abstract

Event Abstract Back to Event Older brains are not all alike: Individual differences in brain activation patterns during working memory performance Ulman Lindenberger1* 1 Max Planck Institute for Human Development, Germany Individual differences in cognitive performance increase from early to late adulthood. In this talk, I will examine this heterogeneity at genetic and neural levels of analysis. First, I will present the hypothesis that losses in neurochemical and anatomical brain resources in normal aging modulate the effects of common genetic variations on cognitive functioning. This hypothesis is based on the assumption that the function relating brain resources to cognition is nonlinear, so that genetic differences exert increasingly large effects on cognition as resources recede from high to medium levels in the course of aging. I will present empirical support for this hypothesis involving the effects of the COMT and BDNF genes on working memory and episodic memory. Second, I will note that performance heterogeneity generally has been largely neglected in fMRI aging studies of working memory. As a result, age differences in activation patterns are often confounded with individual differences in performance level. I will report data from two studies addressing this issue by comparing younger and older adults whose working memory performance is either low or high. In the first study (Nagel et al., 2009), 30 younger (20-30 years) and 30 older (60-70 years) healthy adults were tested on a spatial WM task with three load levels. In both age groups, a region-of-interest (ROI) analysis revealed marked differences in the activation patterns between high and low performers. Critically, among the older adults, a more “youth-like” load-dependent modulation of the BOLD signal was associated with higher levels of spatial WM performance. In the second study (Nagel et al., submitted), 30 younger adults (21-31) and 30 older adults (60-71) were tested in a parametric letter n-back task, again with three load levels. Across age groups, individual differences in the WM network’s responsivity to increasing task difficulty were related to individual differences in WM performance, with a more responsive BOLD signal predicting greater WM proficiency. Furthermore, individuals with higher WM performance showed greater change in connectivity between left dorsolateral prefrontal cortex and left premotor cortex with load. The results of both studies underscore the need of taking performance level into account when studying adult age differences in functional brain activation patterns. Our results suggest that a more responsive and connectivity-modulated WM network contributes to higher WM performance, regardless of adult age.