Span, CRUNCH, and Beyond: Working Memory Capacity and the Aging Brain

• Published in: Journal of cognitive neuroscience Vol. 22; no. 4; pp. 655 - 669
• Main Authors: Schneider-Garces, Nils J., Gordon, Brian A., Brumback-Peltz, Carrie R., Shin, Eunsam, Lee, Yukyung, Sutton, Bradley P., Maclin, Edward L., Gratton, Gabriele, Fabiani, Monica
• Format: Journal Article
• Language: English
• Published: One Rogers Street, Cambridge, MA 02142-1209, USA MIT Press 01.04.2010; MIT Press Journals, The
• Subjects: Adolescent; Adult; Age Factors; Aged; Aged, 80 and over; Aging; Aging - physiology; Analysis of Variance; Brain; Brain - blood supply; Brain - physiology; Brain Mapping; Cognition & reasoning; Female; Functional Laterality; Humans; Image Processing, Computer-Assisted - methods; Information processing; Magnetic Resonance Imaging - methods; Male; Medical imaging; Memory, Short-Term - physiology; Models, Neurological; Neuropsychological Tests; Neurosciences; Oxygen - blood; Photic Stimulation; Reaction Time - physiology; Young Adult
• ISSN: 0898-929X; 1530-8898
• DOI: 10.1162/jocn.2009.21230

Neuroimaging data emphasize that older adults often show greater extent of brain activation than younger adults for similar objective levels of difficulty. A possible interpretation of this finding is that older adults need to recruit neuronal resources at lower loads than younger adults, leaving no resources for higher loads, and thus leading to performance decrements [Compensation-Related Utilization of Neural Circuits Hypothesis; e.g., Reuter-Lorenz, P. A., & Cappell, K. A. Neurocognitive aging and the compensation hypothesis. 177–182, 2008]. The Compensation-Related Utilization of Neural Circuits Hypothesis leads to the prediction that activation differences between younger and older adults should disappear when task difficulty is made subjectively comparable. In a Sternberg memory search task, this can be achieved by assessing brain activity as a function of load relative to the individual's memory span, which declines with age. Specifically, we hypothesized a nonlinear relationship between load and both performance and brain activity and predicted that asymptotes in the brain activation function should correlate with performance asymptotes (corresponding to working memory span). The results suggest that age differences in brain activation can be largely attributed to individual variations in working memory span. Interestingly, the brain activation data show a sigmoid relationship with load. Results are discussed in terms of Cowan's [Cowan, N. The magical number 4 in short-term memory: A reconsideration of mental storage capacity. 87–114, 2001] model of working memory and theories of impaired inhibitory processes in aging.