Department of Psychology, University of Michigan, Ann Arbor, MI 48109, USA.
Neuroimage. 2012 Jan 2;59(1):853-60. doi: 10.1016/j.neuroimage.2011.07.064. Epub 2011 Jul 30.
In functional magnetic resonance imaging (fMRI) studies, researchers often attempt to ensure that group differences in brain activity are not confounded with group differences in mean reaction time (RT). However, even when groups are matched for performance, they may differ in terms of the RT-BOLD relationship: the degree to which brain activity varies with RT on a trial-by-trial basis. Group activation differences might therefore be influenced by group differences in the relationship between brain activity and time on task. Here, we investigated whether correcting for this potential confound alters group differences in brain activity. Specifically, we reanalyzed data from a functional MRI study of response conflict in children and adults, in which conventional analyses indicated that conflict-related activity did not differ between groups. We found that the RT-BOLD relationship was weaker in children than in adults. Consequently, after removing the effect of RT on brain activity, children exhibited greater conflict-related activity than adults in both the posterior medial prefrontal cortex and the right dorsolateral prefrontal cortex. These results identify the RT-BOLD relationship as an important potential confound in fMRI studies of group differences. They also suggest that the magnitude of the RT-BOLD relationship may be a useful biomarker of brain maturity.
在功能磁共振成像（fMRI）研究中，研究人员通常试图确保大脑活动的组间差异不会与平均反应时间（RT）的组间差异混淆。然而，即使组在表现上相匹配，它们在 RT-BOLD 关系方面也可能存在差异：即大脑活动在逐次基础上随 RT 变化的程度。因此，组激活差异可能受到大脑活动与任务时间之间关系的组间差异的影响。在这里，我们研究了纠正这种潜在混杂因素是否会改变大脑活动的组间差异。具体来说，我们重新分析了儿童和成人反应冲突的功能磁共振成像研究的数据，其中常规分析表明组间的冲突相关活动没有差异。我们发现，与成年人相比，儿童的 RT-BOLD 关系较弱。因此，在去除 RT 对大脑活动的影响后，儿童在后部内侧前额叶皮层和右侧背外侧前额叶皮层中表现出比成年人更大的冲突相关活动。这些结果确定了 RT-BOLD 关系是 fMRI 研究中组间差异的一个重要潜在混杂因素。它们还表明，RT-BOLD 关系的幅度可能是大脑成熟度的有用生物标志物。
