Charlton R A, Landau S, Schiavone F, Barrick T R, Clark C A, Markus H S, Morris R G
Clinical Neuroscience, St. George's University of London, Cranmer Terrace, London SW17 0RE, UK.
Neurobiol Aging. 2008 Oct;29(10):1547-55. doi: 10.1016/j.neurobiolaging.2007.03.017. Epub 2007 Apr 23.
Cognitive changes in normal aging have been explained by the frontal-executive hypothesis, but the assumptions made by this hypothesis concerning the neurobiological causes are still a matter of debate. Executive functions (EF) may activate neural networks that include disparate grey matter regions, and rely on the integrity of white matter connections. In 118 adults (50-90 years old) from the GENIE study, white matter integrity was measured using diffusion tensor imaging, and information processing speed, fluid intelligence and EF were assessed. A theory-driven structural equation model was developed to test associations between variables. The model was revised, removing non-significant paths. The adjusted model explained well the covariance in our data; and suggested that the reduction in white matter integrity associated with age directly affected only working memory. Fluid intelligence was mediated by all measured cognitive variables. The results suggest that white matter integrity may be particularly important for abilities activating complex neural networks, as occurs in working memory. Integration of the information processing speed and frontal-executive hypotheses may provide important information regarding common, unique, and mediating factors in cognitive aging.
正常衰老过程中的认知变化已由额叶执行假说进行了解释，但该假说关于神经生物学原因的假设仍存在争议。执行功能（EF）可能会激活包括不同灰质区域在内的神经网络，并依赖于白质连接的完整性。在GENIE研究中的118名成年人（50 - 90岁）中，使用扩散张量成像测量白质完整性，并评估信息处理速度、流体智力和执行功能。开发了一个理论驱动的结构方程模型来测试变量之间的关联。对模型进行了修订，去除了无显著意义的路径。调整后的模型很好地解释了我们数据中的协方差；并表明与年龄相关的白质完整性降低仅直接影响工作记忆。流体智力由所有测量的认知变量介导。结果表明，白质完整性对于激活复杂神经网络的能力可能特别重要，如在工作记忆中所发生的那样。信息处理速度假说和额叶执行假说的整合可能会提供有关认知衰老中共同、独特和中介因素的重要信息。
