Center for MR-Research, University Children's Hospital, Zurich, Switzerland.
PLoS One. 2012;7(7):e39447. doi: 10.1371/journal.pone.0039447. Epub 2012 Jul 6.
In humans, theta band (5-7 Hz) power typically increases when performing cognitively demanding working memory (WM) tasks, and simultaneous EEG-fMRI recordings have revealed an inverse relationship between theta power and the BOLD (blood oxygen level dependent) signal in the default mode network during WM. However, synchronization also plays a fundamental role in cognitive processing, and the level of theta and higher frequency band synchronization is modulated during WM. Yet, little is known about the link between BOLD, EEG power, and EEG synchronization during WM, and how these measures develop with human brain maturation or relate to behavioral changes. We examined EEG-BOLD signal correlations from 18 young adults and 15 school-aged children for age-dependent effects during a load-modulated Sternberg WM task. Frontal load (in-)dependent EEG theta power was significantly enhanced in children compared to adults, while adults showed stronger fMRI load effects. Children demonstrated a stronger negative correlation between global theta power and the BOLD signal in the default mode network relative to adults. Therefore, we conclude that theta power mediates the suppression of a task-irrelevant network. We further conclude that children suppress this network even more than adults, probably from an increased level of task-preparedness to compensate for not fully mature cognitive functions, reflected in lower response accuracy and increased reaction time. In contrast to power, correlations between instantaneous theta global field synchronization and the BOLD signal were exclusively positive in both age groups but only significant in adults in the frontal-parietal and posterior cingulate cortices. Furthermore, theta synchronization was weaker in children and was--in contrast to EEG power--positively correlated with response accuracy in both age groups. In summary we conclude that theta EEG-BOLD signal correlations differ between spectral power and synchronization and that these opposite correlations with different distributions undergo similar and significant neuronal developments with brain maturation.
在人类中，执行认知要求高的工作记忆 (WM) 任务时，θ 频段 (5-7Hz) 的功率通常会增加，同时 EEG-fMRI 记录显示，在 WM 期间，θ 频段的功率与默认模式网络中的 BOLD（血氧水平依赖）信号呈反比关系。然而，同步在认知处理中也起着至关重要的作用，在 WM 期间，θ 频段和更高频段的同步水平会发生调制。然而，人们对 WM 期间 BOLD、EEG 功率和 EEG 同步之间的联系知之甚少，也不知道这些测量值如何随着人类大脑成熟而发展，以及与行为变化有何关联。我们检查了 18 名年轻成年人和 15 名学龄儿童在负荷调制 Sternberg WM 任务期间的 EEG-BOLD 信号相关性，以研究年龄对这些相关性的影响。与成年人相比，儿童的额叶负荷（不）依赖 EEGθ 频段功率明显增强，而成年人则表现出更强的 fMRI 负荷效应。儿童的全局 θ 频段功率与默认模式网络中的 BOLD 信号之间呈现出更强的负相关，而成年人则相反。因此，我们得出结论，θ 频段功率介导了对无关网络的抑制。我们进一步得出结论，儿童对该网络的抑制作用甚至超过了成年人，这可能是由于他们的任务准备程度更高，以弥补认知功能尚未完全成熟的情况，这反映在较低的反应准确率和更长的反应时间上。与功率不同，两组年龄的即时θ 频段全局场同步与 BOLD 信号之间的相关性均为正相关，但仅在成年人的额顶叶和后扣带回皮质中具有统计学意义。此外，θ 频段同步在儿童中较弱，与反应准确率呈正相关，这与 EEG 功率相反，在两组年龄中均呈正相关。总之，我们得出结论，θ EEG-BOLD 信号相关性在谱功率和同步之间存在差异，并且这些具有不同分布的相反相关性随着大脑成熟而经历类似且显著的神经发育。
