University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
J Cogn Neurosci. 2010 Apr;22(4):655-69. 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. Current Directions in Psychological Science, 17, 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. Behavioral and Brain Sciences, 24, 87-114, 2001] model of working memory and theories of impaired inhibitory processes in aging.
神经影像学数据强调，对于相似的客观难度水平，老年人的大脑激活程度往往比年轻人更大。对这一发现的一种可能解释是，老年人需要比年轻人在较低的负荷下招募神经元资源，而没有资源用于更高的负荷，从而导致表现下降[补偿相关的神经回路利用假说；例如，Reuter-Lorenz，P. A.和 Cappell，K. A.神经认知老化和补偿假说。当前心理学科学的趋势，17，177-182，2008]。补偿相关的神经回路利用假说导致了这样的预测，即当任务难度在主观上变得可比时，年轻人和老年人之间的激活差异应该消失。在 Sternberg 记忆搜索任务中，这可以通过评估大脑活动作为与个体记忆跨度相关的负荷的函数来实现，而记忆跨度随着年龄的增长而下降。具体来说，我们假设了负荷与表现和大脑活动之间的非线性关系，并预测大脑激活函数中的渐近线应该与表现渐近线（对应于工作记忆跨度）相关。结果表明，大脑激活中的年龄差异可以很大程度上归因于工作记忆跨度的个体差异。有趣的是，大脑激活数据与负荷呈类 S 形关系。结果根据 Cowan 的[Cowan，N.短期记忆中的神奇数字 4：对心理存储容量的重新思考。行为与脑科学，24，87-114，2001]工作记忆模型和衰老中受损抑制过程的理论进行了讨论。
