Fast fMRI can detect oscillatory neural activity in humans
Fast fMRI can detect oscillatory neural activity in humans
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DOI：
10.1073/pnas.1608117113
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发表时间：
2016-10-25
影响因子：
11.1
通讯作者：
Polimeni, Jonathan R.
中科院分区：
文献类型：
--
作者：
Lewis, Laura D.;Setsompop, Kawin;Polimeni, Jonathan R.
振荡神经动力学在大规模脑网络的协调中起着重要的作用。高水平的认知过程依赖于在数百毫秒内进化的动力学，因此测量这个频率范围内的神经活动对认知神经科学很重要。然而，目前的非侵入性神经成像方法不能精确定位0.2赫兹以上的振荡神经活动。脑电图学和脑磁图学的空间分辨率有限，而功能磁共振成像的时间分辨率有限，因为它测量血管反应，而不是直接记录神经活动。我们假设，最近快速功能磁共振成像技术的发展，结合超高场系统提供的额外灵敏度，可以实现对神经振荡的精确定位。我们以人眼视皮层为模型系统，测试了fMRI是否能检测到神经振荡。我们在单次扫描过程中检测到了小的振荡fMRI信号，这些信号对高达0.75赫兹的刺激做出了反应，这些反应比标准线性模型预测的要大一个数量级。同时的EEG-fMRI和基于血液动力学对神经元活动反应的生物物理模型的模拟表明，对于快速变化的刺激，血氧水平依赖的反应变得更快，从而能够检测到比预期更高的频率。考虑到体素之间的相位延迟，进一步改进了检测，表明识别血管延迟将随着更高频率的活动而变得越来越重要。这些结果挑战了血流动力学反应缓慢的假设，并表明功能磁共振成像有可能直接映射整个大脑的神经振荡。
Oscillatory neural dynamics play an important role in the coordination of large-scale brain networks. High-level cognitive processes depend on dynamics evolving over hundreds of milliseconds, so measuring neural activity in this frequency range is important for cognitive neuroscience. However, current noninvasive neuroimaging methods are not able to precisely localize oscillatory neural activity above 0.2 Hz. Electroencephalography and magnetoencephalography have limited spatial resolution, whereas fMRI has limited temporal resolution because it measures vascular responses rather than directly recording neural activity. We hypothesized that the recent development of fast fMRI techniques, combined with the extra sensitivity afforded by ultra-high-field systems, could enable precise localization of neural oscillations. We tested whether fMRI can detect neural oscillations using human visual cortex as a model system. We detected small oscillatory fMRI signals in response to stimuli oscillating at up to 0.75 Hz within single scan sessions, and these responses were an order of magnitude larger than predicted by canonical linear models. Simultaneous EEG-fMRI and simulations based on a biophysical model of the hemodynamic response to neuronal activity suggested that the blood oxygen level-dependent response becomes faster for rapidly varying stimuli, enabling the detection of higher frequencies than expected. Accounting for phase delays across voxels further improved detection, demonstrating that identifying vascular delays will be of increasing importance with higher-frequency activity. These results challenge the assumption that the hemodynamic response is slow, and demonstrate that fMRI has the potential to map neural oscillations directly throughout the brain.