Perry Michele E, McDonald Carrie R, Hagler Donald J, Gharapetian Lusineh, Kuperman Joshua M, Koyama Alain K, Dale Anders M, McEvoy Linda K
Department of Cognitive Science, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093, USA.
Neuropsychologia. 2009 Nov;47(13):2835-42. doi: 10.1016/j.neuropsychologia.2009.06.008. Epub 2009 Jun 21.
Attentional set-shifting ability, commonly assessed with the Trail Making Test (TMT), decreases with increasing age in adults. Since set-shifting performance relies on activity in widespread brain regions, deterioration of the white matter tracts that connect these regions may underlie the age-related decrease in performance. We used an automated fiber tracking method to investigate the relationship between white matter integrity in several cortical association tracts and TMT performance in a sample of 24 healthy adults, 21-80 years. Diffusion tensor images were used to compute average fractional anisotropy (FA) for five cortical association tracts, the corpus callosum (CC), and the corticospinal tract (CST), which served as a control. Results showed that advancing age was associated with declines in set-shifting performance and with decreased FA in the CC and in association tracts that connect frontal cortex to more posterior brain regions, including the inferior fronto-occipital fasciculus (IFOF), uncinate fasciculus (UF), and superior longitudinal fasciculus (SLF). Declines in average FA in these tracts, and in average FA of the right inferior longitudinal fasciculus (ILF), were associated with increased time to completion on the set-shifting subtask of the TMT but not with the simple sequencing subtask. FA values in these tracts were strong mediators of the effect of age on set-shifting performance. Automated tractography methods can enhance our understanding of the fiber systems involved in performance of specific cognitive tasks and of the functional consequences of age-related changes in those systems.
注意力转换能力通常通过连线测验（TMT）进行评估，在成年人中，该能力会随着年龄的增长而下降。由于转换能力的表现依赖于广泛脑区的活动，连接这些区域的白质束的退化可能是与年龄相关的能力下降的基础。我们使用一种自动纤维追踪方法，在24名年龄在21至80岁的健康成年人样本中，研究了几条皮质联合束的白质完整性与TMT表现之间的关系。扩散张量图像用于计算五条皮质联合束、胼胝体（CC）和皮质脊髓束（CST，作为对照）的平均分数各向异性（FA）。结果显示，年龄的增长与转换能力的下降以及CC和连接额叶皮质与更靠后脑区的联合束（包括额枕下束（IFOF）、钩束（UF）和上纵束（SLF））中FA的降低有关。这些束的平均FA以及右下纵束（ILF）的平均FA的下降与TMT转换子任务的完成时间增加有关，但与简单序列子任务无关。这些束中的FA值是年龄对转换能力表现影响的强有力中介因素。自动纤维束成像方法可以增强我们对参与特定认知任务表现的纤维系统以及这些系统中与年龄相关变化的功能后果的理解。
