Multimodal integration of functional neuroimaging data

越来越多的非侵入性神经成像技术现在可以用来研究正常的大脑功能，但也可以研究大脑疾病。然而，它不存在任何理想的探测技术，能够精确地测量大脑中活动发生的时间(毫秒级)和地点(毫米级)。每种神经成像技术都通过不同的机制(神经元电流、氧气消耗)测量大脑活动的一部分，有时更专注于“在哪里？”这个问题。(良好的空间分辨率)还是“什么时候？”(良好的时间分辨率)。这些技术每一种都有其特定的优点和局限性，单独分析每一种技术只能提供有关潜在大脑活动的部分信息。我的研究项目的目标是开发适当地组合这些多模式数据的方法，即数据融合方法，以便检测通过单独考虑每种模式而可能遗漏的额外信息。一个典型的挑战是将直接测量具有高时间分辨率的神经元活动的模式与以高空间分辨率间接测量相同功能的其他模式相结合，例如通过血流动力学过程。我的项目将涉及三种很有前途的功能模式的整合：(1)同步脑电(EEG)-脑磁图(MEG)采集，直接在头皮上测量神经元同步活动产生的信号的电和磁分量(以毫秒为尺度)。(2)同步EEG-功能磁共振成像fMRI采集，以第二尺度在整个大脑内测量与头皮EEG上检测到的信号相关的血流动力学响应。(3)通过放置在头部表面的光纤利用脑组织内红外光的吸收特性，同时进行EEG-近红外光谱(NIRS)采集，以测量在头皮EEG上检测到信号时局部氧合和脱氧血红蛋白的变化。该项目的主要临床应用将是使用多模式数据融合技术将这三种模式结合起来，以表征癫痫活动中涉及的大脑区域。

More and more non-invasive neuroimaging techniques are now available to study normal brain functions but also brain disorders. However, it does not exist any ideal exploration technique able to measure precisely when (at a ms scale) and where (at a mm scale) an activity occurred in the brain. Each neuroimaging technique measures through different mechanisms (neuronal electricity, oxygen consumption) part of brain activity, being sometimes more dedicated to the question "where?" (good spatial resolution) or to the question "when?" (good temporal resolution). Each of these techniques having its specific advantages and limitations, analyzing each of them individually only provides partial information regarding underlying brain activity. The objective of my research project is to develop methods to appropriately combine these multimodal data, i.e., data fusion methods, in order to detect additional information that could be missed by considering each modality individually. A typical challenge is to combine modalities measuring directly neuronal activity with high temporal resolution with other modalities measuring indirectly the same function with high spatial resolution, through hemodynamic processes for instance. My project will involve the integration of three promising functional modalities: (1) Simultaneous ElectroEncephaloGraphy (EEG) - MagnetoEncephaloGraphy (MEG) acquisitions, measuring directly on the scalp electric and magnetic components of signals generated by neurons synchronously active (at a ms scale). (2) Simultaneous EEG - functional Magnetic Resonance Imaging fMRI acquisitions to measure, within the whole brain at a second scale, hemodynamic responses that correlate with signals detected on scalp EEG. (3) Simultaneous EEG - Near InfraRed Spectroscopy (NIRS) acquisitions to measure local changes in oxy- and deoxy-hemoglobin at the time of signals detected on scalp EEG, by exploiting absorption properties of infrared light within brain tissues using optic fibres placed on the surface of the head. The principal clinical application of this project will be to combine these three modalities using multimodal data fusion techniques to characterize brain regions involved during epileptic activity.