Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands.
PLoS One. 2009 Dec 14;4(12):e8307. doi: 10.1371/journal.pone.0008307.
While traditionally quite distinct, functional neuroimaging (e.g. functional magnetic resonance imaging: fMRI) and functional interference techniques (e.g. transcranial magnetic stimulation: TMS) increasingly address similar questions of functional brain organization, including connectivity, interactions, and causality in the brain. Time-resolved TMS over multiple brain network nodes can elucidate the relative timings of functional relevance for behavior ("TMS chronometry"), while fMRI functional or effective connectivity (fMRI EC) can map task-specific interactions between brain regions based on the interrelation of measured signals. The current study empirically assessed the relation between these different methods.
METHODOLOGY/PRINCIPAL FINDINGS: One group of 15 participants took part in two experiments: one fMRI EC study, and one TMS chronometry study, both of which used an established cognitive paradigm involving one visuospatial judgment task and one color judgment control task. Granger causality mapping (GCM), a data-driven variant of fMRI EC analysis, revealed a frontal-to-parietal flow of information, from inferior/middle frontal gyrus (MFG) to posterior parietal cortex (PPC). FMRI EC-guided Neuronavigated TMS had behavioral effects when applied to both PPC and to MFG, but the temporal pattern of these effects was similar for both stimulation sites. At first glance, this would seem in contradiction to the fMRI EC results. However, we discuss how TMS chronometry and fMRI EC are conceptually different and show how they can be complementary and mutually constraining, rather than contradictory, on the basis of our data.
CONCLUSIONS/SIGNIFICANCE: The findings that fMRI EC could successfully localize functionally relevant TMS target regions on the single subject level, and conversely, that TMS confirmed an fMRI EC identified functional network to be behaviorally relevant, have important methodological and theoretical implications. Our results, in combination with data from earlier studies by our group (Sack et al., 2007, Cerebral Cortex), lead to informed speculations on complex brain mechanisms, and TMS disruption thereof, underlying visuospatial judgment. This first in-depth empirical and conceptual comparison of fMRI EC and TMS chronometry thereby shows the complementary insights offered by the two methods.
虽然传统上两者截然不同，但功能神经影像学（例如功能磁共振成像：fMRI）和功能干扰技术（例如经颅磁刺激：TMS）越来越多地针对大脑的功能组织的相似问题，包括连通性、相互作用和因果关系。通过多个脑网络节点的时间分辨 TMS 可以阐明行为的功能相关性的相对时间（“TMS 计时学”），而 fMRI 功能或有效连通性（fMRI EC）可以根据测量信号的相互关系来映射大脑区域之间特定于任务的相互作用。本研究经验性地评估了这些不同方法之间的关系。
方法/主要发现：一组 15 名参与者参加了两项实验：一项 fMRI EC 研究和一项 TMS 计时学研究，这两项研究都使用了一种既定的认知范式，涉及一个视觉空间判断任务和一个颜色判断控制任务。Granger 因果关系映射（GCM），fMRI EC 分析的数据驱动变体，揭示了从前额到顶叶的信息流，从中下额/中额回（MFG）到后顶叶皮层（PPC）。当应用于 PPC 和 MFG 时，基于 fMRI EC 引导的神经导航 TMS 具有行为效应，但这两个刺激部位的效应时间模式相似。乍一看，这似乎与 fMRI EC 结果相矛盾。然而，我们讨论了 TMS 计时学和 fMRI EC 在概念上的不同之处，并根据我们的数据展示了它们如何互补和相互约束，而不是相互矛盾的。
结论/意义：在个体水平上，fMRI EC 可以成功定位功能相关的 TMS 目标区域，反之，TMS 证实了 fMRI EC 识别的功能网络与行为相关，这具有重要的方法和理论意义。我们的结果，结合我们小组的早期研究数据（Sack 等人，2007，大脑皮层），导致了对视觉空间判断的复杂大脑机制及其 TMS 破坏的有根据的推测。这是首次对 fMRI EC 和 TMS 计时学的深入实证和概念比较，因此展示了这两种方法提供的互补见解。
