Brain Imaging Center, McLean Hospital, Belmont, MA 02478, USA.
Neuroimage. 2010 Nov 1;53(2):553-64. doi: 10.1016/j.neuroimage.2010.06.049. Epub 2010 Jun 28.
Low frequency oscillations (LFOs), characterized by frequencies in the range 0.01-0.1 Hz are commonly observed in blood-related brain functional measurements such as near-infrared spectroscopy (NIRS) and functional magnetic resonance imaging (fMRI). While their physiological origin and implications are not fully understood, these signals are believed to reflect some types of neuronal signaling, systemic hemodynamics, and/or cerebral vascular auto-regulation processes. Here, we examine a new method of integrated processing of concurrent NIRS and fMRI data collected on six human subjects during a whole brain resting state acquisition. The method combines the high spatial resolution offered by fMRI (approximately 3mm) and the high temporal resolution offered by NIRS (approximately 80 ms) to allow for the quantitative assessment of temporal relationships between the LFOs observed at different spatial locations in fMRI data. This temporal relationship allowed us to infer that the origin of a large proportion of the LFOs is independent of the baseline neural activity. The spatio-temporal pattern of LFOs detected by NIRS and fMRI evolves temporally through the brain in a way that resembles cerebral blood flow dynamics. Our results suggest that a major component of the LFOs arise from fluctuations in the blood flow and hemoglobin oxygenation at a global circulatory system level.
低频振荡（LFOs），其特征是频率在 0.01-0.1 Hz 范围内，在与血液相关的脑功能测量中很常见，如近红外光谱（NIRS）和功能磁共振成像（fMRI）。虽然它们的生理起源和意义尚未完全理解，但这些信号被认为反映了某些类型的神经元信号、全身血液动力学和/或脑血管自动调节过程。在这里，我们研究了一种新的方法，用于对 6 名人类受试者在整个大脑静息状态采集期间同时收集的 NIRS 和 fMRI 数据进行综合处理。该方法结合了 fMRI（约 3mm）提供的高空间分辨率和 NIRS（约 80ms）提供的高时间分辨率，以允许对 fMRI 数据中不同空间位置观察到的 LFOs 之间的时间关系进行定量评估。这种时间关系使我们能够推断出大量 LFOs 的起源与基线神经活动无关。通过 NIRS 和 fMRI 检测到的 LFOs 的时空模式在大脑中随时间演变，类似于脑血流动力学。我们的结果表明，LFOs 的一个主要组成部分来自于全身循环系统水平的血流和血红蛋白氧合的波动。
