Department of Human Services, University of Virginia.
Department of Psychology, Oklahoma State University.
Neuropsychology. 2014 May;28(3):459-71. doi: 10.1037/neu0000050. Epub 2014 Mar 3.
The current study examined competing predictions of the default mode, cognitive neuroenergetic, and functional working memory models of attention-deficit/hyperactivity disorder (ADHD) regarding the relation between neurocognitive impairments in working memory and intraindividual variability.
Twenty-two children with ADHD and 15 typically developing children were assessed on multiple tasks measuring intraindividual reaction time (RT) variability (ex-Gaussian: tau, sigma) and central executive (CE) working memory. Latent factor scores based on multiple, counterbalanced tasks were created for each construct of interest (CE, tau, sigma) to reflect reliable variance associated with each construct and remove task-specific, test-retest, and random error.
Bias-corrected, bootstrapped mediation analyses revealed that CE working memory accounted for 88% to 100% of ADHD-related RT variability across models, and between-group differences in RT variability were no longer detectable after accounting for the mediating role of CE working memory. In contrast, RT variability accounted for 10% to 29% of between-group differences in CE working memory, and large magnitude CE working memory deficits remained after accounting for this partial mediation. Statistical comparison of effect size estimates across models suggests directionality of effects, such that the mediation effects of CE working memory on RT variability were significantly greater than the mediation effects of RT variability on CE working memory.
The current findings question the role of RT variability as a primary neurocognitive indicator in ADHD and suggest that ADHD-related RT variability may be secondary to underlying deficits in CE working memory.
本研究考察了默认模式、认知神经能量和功能工作记忆模型对注意缺陷多动障碍（ADHD）中工作记忆神经认知损伤与个体内变异性之间关系的竞争性预测。
22 名 ADHD 儿童和 15 名正常发育儿童接受了多项测量个体内反应时（RT）变异性（超伽马分布：tau、sigma）和中央执行（CE）工作记忆的任务。针对每个感兴趣的结构（CE、tau、sigma），基于多个平衡任务创建潜在因子得分，以反映与每个结构相关的可靠方差，并消除任务特定、测试-重测和随机误差。
经偏置校正、自举中介分析显示，CE 工作记忆解释了 ADHD 相关 RT 变异性的 88%至 100%，且在考虑 CE 工作记忆的中介作用后，RT 变异性在组间差异不再可检测到。相比之下，RT 变异性解释了 CE 工作记忆组间差异的 10%至 29%，并且在考虑这种部分中介后，CE 工作记忆的大程度缺陷仍然存在。对模型间效应大小估计的统计比较表明了效应的方向性，即 CE 工作记忆对 RT 变异性的中介效应显著大于 RT 变异性对 CE 工作记忆的中介效应。
目前的研究结果对 RT 变异性作为 ADHD 中主要神经认知指标的作用提出了质疑，并表明 ADHD 相关的 RT 变异性可能是 CE 工作记忆缺陷的结果。
