Biswal B, Hudetz A G, Yetkin F Z, Haughton V M, Hyde J S
Biophysics Research Institute, Medical College of Wisconsin, Milwaukee 53226-0509, USA.
J Cereb Blood Flow Metab. 1997 Mar;17(3):301-8. doi: 10.1097/00004647-199703000-00007.
Using magnetic resonance (MR) echo-planar imaging (EPI), we recently demonstrated the presence of low-frequency fluctuations (< 0.1 Hz) in MR signal intensity from the resting human brain that have a high degree of temporal correlation (p < 10(-3)) within and across associated regions of the sensorimotor cortex. These fluctuations in MR signal intensity are believed to arise from fluctuations in capillary blood flow and oxygenation. A substantial overlap between the activation map generated by bilateral finger tapping and temporally-correlated voxels from the sensorimotor cortex obtained during rest was observed. In the work reported here, we investigated whether respiratory hypercapnia, which is known to suspend spontaneous oscillations in regional cerebral blood flow, influences these low-frequency fluctuations. The magnitude of low-frequency fluctuations was reversibly diminished during hypercapnia, resulting in a substantial decrease of the temporal correlation both within and across contralateral hemispheres of the sensorimotor cortex. After the breathing mixture was returned to ambient air, the magnitude and spatial extent of the temporal correlation of low-frequency fluctuations returned to normal. Results of this study support the hypothesis that low-frequency physiological fluctuations observed by MR in the human cortex and spontaneous flow oscillations observed in early studies by laser-Doppler flowmetry (LDF) in the cortex of the rat are identical and are secondary to fluctuations in neuronal activity.
我们最近利用磁共振（MR）回波平面成像（EPI）证明，静息人类大脑的MR信号强度中存在低频波动（<0.1Hz），这些波动在感觉运动皮层的相关区域内及区域间具有高度的时间相关性（p<10^(-3)）。据信，MR信号强度的这些波动源于毛细血管血流和氧合作用的波动。我们观察到，双侧手指轻敲所产生的激活图与静息期间从感觉运动皮层获得的时间相关体素之间存在大量重叠。在本文报道的研究中，我们调查了已知会中止局部脑血流自发振荡的呼吸性高碳酸血症是否会影响这些低频波动。在高碳酸血症期间，低频波动的幅度可逆性减小，导致感觉运动皮层对侧半球内及半球间的时间相关性大幅降低。当呼吸混合气恢复到环境空气后，低频波动时间相关性的幅度和空间范围恢复正常。本研究结果支持以下假设：MR在人类皮层中观察到的低频生理波动与早期激光多普勒血流仪（LDF）在大鼠皮层中观察到的自发血流振荡相同，并且是神经元活动波动的继发结果。
