Laureate Institute for Brain Research, 6655 South Yale Avenue, Tulsa, OK 74136, USA.
Neuroimage. 2013 Oct 1;79:81-93. doi: 10.1016/j.neuroimage.2013.04.068. Epub 2013 Apr 28.
Low-frequency temporal fluctuations of physiological signals (<0.1 Hz), such as the respiration and cardiac pulse rate, occur naturally during rest and have been shown to be correlated with blood-oxygenation-level-dependent (BOLD) signal fluctuation. Such physiological signal modulations have been considered as sources of noise and their effects on BOLD signal are commonly removed in functional magnetic resonance imaging (fMRI) studies. However, possible neural correlates of the physiological fluctuations have not been considered nor examined in detail. In the present study we investigated this possibility by simultaneously acquiring electroencephalogram (EEG) with BOLD fMRI data, respiratory and cardiac waveforms in healthy human subjects at eyes-closed and eyes-open resting. We quantified the concurrent changes of the EEG power in the alpha frequency band, the respiration volume, and the cardiac pulse rate, then assessed the temporal correlations between alpha EEG power and physiological signal fluctuations. In addition, time-shifted time courses of alpha EEG power or physiological data were included as regressors to examine their correlations with the whole-brain BOLD fMRI signals. We observed a significant correlation between alpha EEG global field power and respiration, particularly at eyes-closed resting condition. Similar spatial patterns were observed between the correlation maps of BOLD with alpha EEG power and respiration, with negative correlations coinciding in the visual cortex, superior/middle temporal gyrus, inferior frontal gyrus, and inferior parietal lobule and positive correlations in the thalamus and caudate. Regressing out the physiological variations in the BOLD signal resulted in reduced correlation between BOLD and alpha EEG power. These results suggest a mutual link of neuronal origin between alpha EEG power, respiration, and BOLD signals.
生理信号（<0.1 Hz）的低频时间波动，如呼吸和心搏率，在休息时自然发生，并已被证明与血氧水平依赖（BOLD）信号波动相关。这种生理信号调制已被认为是噪声源，在功能磁共振成像（fMRI）研究中通常会去除其对 BOLD 信号的影响。然而，生理波动的可能神经相关性尚未被考虑或详细研究。在本研究中，我们通过同时采集健康受试者闭眼和睁眼休息时的脑电图（EEG）与 BOLD fMRI 数据、呼吸和心搏波，研究了这种可能性。我们量化了 alpha 频带脑电图功率、呼吸量和心搏率的同时变化，然后评估了 alpha 脑电功率与生理信号波动之间的时间相关性。此外，还包括 alpha 脑电功率或生理数据的时间移位时间历程作为回归量，以检查它们与全脑 BOLD fMRI 信号的相关性。我们观察到 alpha 脑电功率与呼吸之间存在显著相关性，尤其是在闭眼休息状态下。BOLD 与 alpha 脑电功率和呼吸之间的相关图具有相似的空间模式，负相关在视觉皮层、上/中颞叶、下额叶和下顶叶重合，正相关在丘脑和尾状核。在 BOLD 信号中回归生理变化会导致 BOLD 与 alpha 脑电功率之间的相关性降低。这些结果表明 alpha 脑电功率、呼吸和 BOLD 信号之间存在神经元起源的相互联系。
