Multichannel single trial MEG of cortical population spikes – SPIKE MEG

进化已经将人类大脑塑造成一个“单一试验”处理器，对环境事件做出快速可靠的反应，大脑对信息的处理是身体最复杂的过程之一。“以思维的速度”观察大脑运作的需求，但不需要在大脑内放置电极，激发了两种时间高分辨率技术：脑电图（EEG）和脑磁图（MEG），它们依赖于测量源自离子神经元电流的电磁场。这些可以分为慢电流和快电流，它们具有不同的微观起源：慢电流-称为突触后电位-发生在一个神经细胞发出的脉冲信号被另一个神经细胞接收时。这种脉冲的发射（将信息传输到下游神经元或肌肉）产生持续仅一毫秒的快速电流-这些“尖峰”被称为动作电位。然而，虽然EEG和MEG的慢电流结果是可靠的，但快电流的结果通常并不可靠。Physikalisch-Technische Bundesanstalt（PTB）是MEG技术发展的先锋，其最近构建的超低噪声磁力计实现了诱发人类皮层群体尖峰的第一个非侵入性单次试验表征，揭示了试验和试验间相关响应延迟之间高度可变的振幅。这些独特的记录开辟了前景，低噪声MEG可能使整体非侵入性测量神经元电流在低和高频率。然而，这些试验性测量是用单通道MEG设备进行的，排除了对皮层网络的协调网络活动中的单个神经元源的分析。拟议的项目将建立在这一势头和设计和构建一个新的超低噪声多通道MEG系统，将使空间分辨的非侵入性测量慢突触电流和快速尖峰活动在同一时间。我们还将利用EEG和MEG的互补性，通过整合我们之前在低噪声EEG上的经验，它们对神经元源特征具有不同的空间敏感性。来自Charité-Universitätsmedizin柏林的神经学家与PTB的物理学家和工程师合作，回答传统上需要侵入性微电极记录的问题。我们将研究这一假设，即躯体感觉皮层中的神经元振荡（慢电流）影响局部尖峰行为（快电流），躯体感觉皮层的一部分中的尖峰抑制相邻区域中的并发尖峰活动。该项目中技术和生理专业知识的迭代交互和紧密集成是开发新型超低噪声MEG/EEG设备的关键，该设备将为人类非侵入性神经生理学带来变革。

Evolution has shaped the human brain as a “single-trial” processor reacting fast and reliably to environmental events, and the cerebral processing of information is one of the body’s most complex processes. The demand to observe the brain’s operation ‘at the speed of thought’, but without the need to place electrodes inside the brain, inspired two temporally high-resolution techniques: electroencephalography (EEG) and magnetoencephalography (MEG) which rely on measuring the electromagnetic field originating from ionic neuronal currents. These can be categorized as slow and fast currents having different microscopic origins: Slow currents—known as postsynaptic potentials—occur when impulse signals, fired by one nerve cell, are received by another. The firing of such impulses (which transmit information to downstream neurons or muscles) produces fast currents which last for just a millisecond – these 'spikes' are known as action potentials. However, while results for slow currents from EEG and MEG are reliable, those for fast currents in general are not. The Physikalisch-Technische Bundesanstalt (PTB) is a spearhead in the development of MEG technology, and its recently constructed ultralow-noise magnetometer enabled the first non-invasive single-trial characterization of evoked human cortical population spikes, revealing amplitudes highly variable between trials and intertrial correlated response latencies. These unique recordings opened up the prospect that low-noise MEG might enable integral non-invasive measurements of neuronal currents at both low and high frequencies. However, these pilot measurements were performed with a single-channel MEG device, precluding analysis of individual neuronal sources in the orchestrated network activity of the cortical network. The proposed project will build on this momentum and design and construct a novel ultralow-noise multichannel MEG system that will enable spatially resolved non-invasive measurements of both slow synaptic currents and fast spiking activity at the same time. We will also make use of the complementary nature of EEG and MEG which have different spatial sensitivities to neuronal source characteristics by integrating our previous experience on low-noise EEG. Neurologists from Charité-Universitätsmedizin Berlin team up with physicists and engineers from PTB to answer questions that conventionally call for invasive microelectrode recordings. We will examine the hypothesis that neuronal oscillations (slow currents) in the somatosensory cortex affects local spiking behavior (fast currents) and that spiking in one part of the somatosensory cortex inhibits concurrent spiking activity in neighboring regions. The iterative interaction and tight integration of technologic and physiologic expertise in this project is key to the development of a novel ultralow-noise MEG/EEG device that will be transformative for human non-invasive neurophysiology.