Georgia Institute of Technology and Emory University, Biomedical Engineering, Atlanta, GA, USA.
Neuroimage. 2013 Dec;83:826-36. doi: 10.1016/j.neuroimage.2013.07.036. Epub 2013 Jul 19.
Functional connectivity between brain regions, measured with resting state functional magnetic resonance imaging, holds great potential for understanding the basis of behavior and neuropsychiatric diseases. Recently it has become clear that correlations between the blood oxygenation level dependent (BOLD) signals from different areas vary over the course of a typical scan (6-10 min in length), though the changes are obscured by standard methods of analysis that assume the relationships are stationary. Unfortunately, because similar variability is observed in signals that share no temporal information, it is unclear which dynamic changes are related to underlying neural events. To examine this question, BOLD data were recorded simultaneously with local field potentials (LFP) from interhemispheric primary somatosensory cortex (SI) in anesthetized rats. LFP signals were converted into band-limited power (BLP) signals including delta, theta, alpha, beta and gamma. Correlation between signals from interhemispheric SI was performed in sliding windows to produce signals of correlation over time for BOLD and each BLP band. Both BOLD and BLP signals showed large changes in correlation over time and the changes in BOLD were significantly correlated to the changes in BLP. The strongest relationship was seen when using the theta, beta and gamma bands. Interestingly, while steady-state BOLD and BLP correlate with the global fMRI signal, dynamic BOLD becomes more like dynamic BLP after the global signal is regressed. As BOLD sliding window connectivity is partially reflecting underlying LFP changes, the present study suggests it may be a valuable method of studying dynamic changes in brain states.
脑区之间的功能连接，通过静息态功能磁共振成像来测量，对于理解行为和神经精神疾病的基础具有很大的潜力。最近，人们已经清楚地认识到，不同区域之间的血氧水平依赖（BOLD）信号的相关性在典型扫描过程中（长度为 6-10 分钟）会发生变化，尽管这些变化被假设关系是稳定的标准分析方法所掩盖。不幸的是，由于相似的可变性也存在于没有时间信息共享的信号中，因此尚不清楚哪些动态变化与潜在的神经事件有关。为了研究这个问题，在麻醉大鼠的大脑两半球初级体感皮层（SI）同时记录了局部场电位（LFP）和 BOLD 数据。LFP 信号被转换为带限功率（BLP）信号，包括 delta、theta、alpha、beta 和 gamma。在滑动窗口中对来自两半球 SI 的信号进行相关性分析，以产生 BOLD 和每个 BLP 带的随时间变化的相关性信号。BOLD 和 BLP 信号都显示出随时间变化的相关性的大幅变化，BOLD 的变化与 BLP 的变化显著相关。当使用 theta、beta 和 gamma 波段时，相关性最强。有趣的是，虽然稳态 BOLD 和 BLP 与全局 fMRI 信号相关，但在回归全局信号后，动态 BOLD 变得更像动态 BLP。由于 BOLD 滑动窗口连接部分反映了潜在的 LFP 变化，本研究表明它可能是研究大脑状态动态变化的一种有价值的方法。
