Vivian L. Smith Department of Neurosurgery, University of Texas Medical School, Houston, Texas 77030, USA.
J Neurosci. 2011 Sep 7;31(36):12855-65. doi: 10.1523/JNEUROSCI.1457-11.2011.
The relationship between blood oxygenation level-dependent (BOLD) functional MRI (fMRI) signal and the underlying neural electrical activity in humans is a topic of intense interest to systems neuroscience. This relationship has generally been assumed to be invariant regardless of the brain region and the cognitive task being studied. We critically evaluated these assumptions by comparing the BOLD-fMRI response with local field potential (LFP) measurements during visually cued common noun and verb generation in 11 humans in whom 1210 subdural electrodes were implanted. As expected, power in the mid-gamma band (60-120 Hz) correlated positively (r(2) = 0.16, p < 10(-16)) and power in the beta band (13-30 Hz) correlated negatively (r(2) = 0.09, p < 10(-16)) with the BOLD signal change. Beta and mid-gamma band activity independently explain different components of the observed BOLD signal. Importantly, we found that the location (i.e., lobe) of the recording site modulates the relationship between the electrocorticographic (ECoG) signal and the observed fMRI response (p < 10(-16), F(21,1830) = 52.7), while the type of language task does not. Across all brain regions, ECoG activity in the gamma and beta bands explains 22% of the fMRI response, but if the lobar location is considered, 28% of the variance can be explained. Further evaluation of this relationship at the level of individual gyri provides additional evidence of differences in the BOLD-LFP relationship by cortical locus. This spatial variability in the relationship between the fMRI signal and neural activity carries implications for modeling of the hemodynamic response function, an essential step for interregional fMRI comparisons.
血氧水平依赖（BOLD）功能磁共振成像（fMRI）信号与人类大脑中潜在的神经电活动之间的关系是系统神经科学研究的热点。通常认为，无论研究的脑区和认知任务如何，这种关系都是不变的。我们通过比较 11 名被试在视觉提示下进行常见名词和动词生成时的 BOLD-fMRI 响应与局部场电位（LFP）测量，对这些假设进行了严格评估。正如预期的那样，中伽马频段（60-120 Hz）的功率与 BOLD 信号变化呈正相关（r²=0.16，p<10⁻¹⁶），β频段（13-30 Hz）的功率与 BOLD 信号变化呈负相关（r²=0.09，p<10⁻¹⁶）。β和中伽马频段活动独立地解释了观察到的 BOLD 信号的不同成分。重要的是，我们发现记录部位的位置（即脑叶）调节了脑电图（ECoG）信号与观察到的 fMRI 响应之间的关系（p<10⁻¹⁶，F(21,1830)=52.7），而语言任务类型则不影响。在所有脑区，γ和β频段的 ECoG 活动解释了 fMRI 响应的 22%，但如果考虑脑叶位置，则可以解释 28%的方差。在个体脑回层面进一步评估这种关系，为皮质位置不同的 fMRI-LFP 关系提供了更多证据。这种 fMRI 信号与神经活动之间关系的空间变异性对血流动力学响应函数的建模具有影响，血流动力学响应函数是进行区域间 fMRI 比较的重要步骤。
