Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA.
Brain Res. 2010 Mar 8;1318:110-21. doi: 10.1016/j.brainres.2009.12.075. Epub 2010 Jan 6.
Recently we introduced a robust measure, integrated local correlation (ILC), of local connectivity in the brain using fMRI data which reflects the temporal correlation of brain activity in every voxel neighborhood. The current work studies ILC in fMRI data obtained in the absence and presence of sevoflurane anesthesia (0%, 2%, and 1% end-tidal concentration, respectively) administered to healthy volunteers. ILC was determined specifically in regions of the default mode network (DMN) to address local changes in each state. In addition, a potential confound in analyses based on correlations due to signal-to-noise variations was addressed by wavelet denoising. This accommodated decreases in signal power commonly seen during anesthesia without artificially reducing derived correlations. Results showed that ILC was significantly reduced in the entire DMN during 2% sevoflurane yet recovered in the posterior and anterior cingulate cortices as well as inferior parietal cortex during 1% sevoflurane. By contrast, ILC remained attenuated prefrontally in the 1% condition, which indicates uncoupling of the frontal areas of DMN during light anesthesia. These results confirm widespread anesthetic-induced cortical suppression but also demonstrate that the local connectivity of the prefrontal cortex is rapidly reduced by sevoflurane. It remains to be seen whether these alterations arise locally as a direct consequence of anesthetic action on local neurons or are driven by distant changes in oscillations and activity elsewhere in the brain.
最近，我们使用 fMRI 数据引入了一种强大的局部连接度量方法，即整合局部相关（ILC），它反映了每个体素邻域中大脑活动的时间相关性。目前的工作研究了在健康志愿者中施用七氟醚麻醉（分别为 0%、2%和 1%呼气末浓度）时获得的 fMRI 数据中的 ILC。特别在默认模式网络（DMN）的区域中确定了 ILC，以解决每种状态下的局部变化。此外，通过小波去噪解决了由于信号噪声变化而导致基于相关性的分析中的潜在混杂因素。这适应了麻醉期间常见的信号功率下降，而不会人为地降低衍生相关性。结果表明，在 2%七氟醚期间，整个 DMN 的 ILC 显著降低，但在 1%七氟醚期间，后扣带皮层和前扣带皮层以及下顶叶皮层恢复。相比之下，在 1%条件下 ILC 在前额叶仍被抑制，这表明在轻度麻醉期间 DMN 的额叶区域解耦。这些结果证实了广泛的麻醉诱导的皮质抑制，但也表明七氟醚迅速降低了前额叶的局部连接。这些改变是局部产生的，还是由于麻醉作用于局部神经元的直接后果，还是由于大脑其他部位的振荡和活动的远处变化而引起的，还有待观察。
