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“何时”(毫秒尺度)和“何处”(毫米尺度)。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)。每一种技术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。 大多数神经成像技术都是为了对不同的大脑信号敏感而开发的：(1)直接测量神经元的生物电活动(从头皮记录)和(2)通过血液动力学过程间接测量大脑活动，测量向活跃神经元提供氧气的血流量。我的工作目标是在研究正常的大脑活动和异常的癫痫放电时，准确地描述这两种测量之间的联系。第一个目标将是在大脑内定位使用放置在头皮上的光纤测量的血流波动。第二个目标将在于使用这些不同的模式来评估神经元生物电活动和血流动力学过程之间的这种联系的完整性。第三个目标是利用这些多模式数据提取大脑活动的相关信息，以表征静息状态的波动。

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 on 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. Most neuroimaging techniques have been developed in order to be sensitive to different brain signals: (1) direct measurements of neuronal bioelectric activity (from scalp recordings) and (2) indirect measurement of brain activity through hemodynamic processes measuring blood flow providing oxygen to the active neurons. The objective of my work is to accurately characterize the link between these two types of measurements when studying normal brain activity but also abnormal epileptic discharges. The first objective will be to localize, within the brain, fluctuations of blood flow measured using optic fibres placed on the scalp. The second objective will consist in using these different modalities to assess the integrity of this link between neuronal bioelectric activity and hemodynamic processes. The third objective will consist in extracting relevant information on brain activity using these multimodal data to characterize resting state fluctuations.