使用 MRI 寻找神经元电流：与频繁局灶性癫痫放电时间锁定的快速 MR 信号变化的 EEG-fMRI 研究。
Looking for neuronal currents using MRI: an EEG-fMRI investigation of fast MR signal changes time-locked to frequent focal epileptic discharges.
机构信息
Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, London, UK.
出版信息
Neuroimage. 2010 Apr 15;50(3):1109-17. doi: 10.1016/j.neuroimage.2009.12.076. Epub 2009 Dec 28.
RATIONALE
Reproducible direct measurement of neuronal electrical activity using MRI signal changes due to local magnetic field perturbations would represent a step change in neuroimaging methods. While some previous studies using experiments based on evoked and spontaneous activity provided encouraging results no clear demonstration of neuronal current-related MR changes in the human brain has emerged to date. The availability of simultaneously acquired EEG-fMRI in patients with frequent interictal epileptic discharges (IED), which have significantly greater amplitude than evoked potentials, offers the opportunity to further investigate the phenomenon.
METHODS
We re-analysed simultaneously acquired EEG-fMRI data in 6 epilepsy patients with very frequent focal IED and a well-localised generator. A model of MRI signal changes due to fast activity and BOLD signal changes was used to identify fast MR signal changes, potentially directly reflecting neuronal activity. Simultaneously-acquired EEG allowed the comparison of electrical source localisation (ESI), clinical epilepsy localisation and BOLD signal changes with the fast MR signal changes.
RESULTS
Clusters of IED-related fast MR signal change were observed in all cases. Spatial correspondence between the IED-related fast MR, BOLD, ESI clusters and irritative zone (IZ) was observed in one slice of a single dataset. The other IED-related fast MR clusters were remote from electro-clinically determined generators of interictal activity. The sign and magnitude of the fast MR signal changes varied across regions and subjects.
CONCLUSION
The observed fast MR changes cannot be confidently attributed to the direct effect of neuronal currents due to lack of spatial concordance with generators of interictal activity, IED-related BOLD clusters and ESI estimates.
原理
利用 MRI 信号变化来重现直接测量神经元电活动，这种方法由于局部磁场扰动而产生，这将代表神经影像学方法的一个重大突破。虽然之前有一些使用基于诱发和自发性活动的实验的研究提供了令人鼓舞的结果，但迄今为止，尚未在人类大脑中出现明确证明与神经元电流相关的 MR 变化的证据。在频繁出现局灶性癫痫发作间期放电（IED）的癫痫患者中，同时获取 EEG-fMRI 的方法具有更大的可用性，因为这些放电的幅度明显大于诱发电位，这为进一步研究这一现象提供了机会。
方法
我们重新分析了 6 名癫痫患者的同时获取的 EEG-fMRI 数据，这些患者具有非常频繁的局灶性 IED 和一个定位良好的发生器。使用 MRI 信号变化模型和 BOLD 信号变化模型来识别快速 MR 信号变化，这些变化可能直接反映神经元活动。同时获取的 EEG 允许将电信号源定位（ESI）、临床癫痫定位和 BOLD 信号变化与快速 MR 信号变化进行比较。
结果
在所有病例中都观察到了与 IED 相关的快速 MR 信号变化簇。在一个数据集的一个切片中观察到了 IED 相关的快速 MR、BOLD 和 ESI 簇与刺激性区域（IZ）之间的空间对应关系。其他与 IED 相关的快速 MR 簇远离癫痫间活动的电临床确定发生器。快速 MR 信号变化的符号和幅度在不同区域和受试者之间有所不同。
结论
由于缺乏与癫痫间活动的发生器、IED 相关的 BOLD 簇和 ESI 估计值的空间一致性，因此观察到的快速 MR 变化不能被明确归因于神经元电流的直接影响。
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