Karadas Mürsel, Olsson Christoffer, Winther Hansen Nikolaj, Perrier Jean-François, Webb James Luke, Huck Alexander, Andersen Ulrik Lund, Thielscher Axel
Department of Health Technology, Technical University of Denmark, Kongens Lyngby, Denmark.
Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
Front Neurosci. 2021 May 13;15:643614. doi: 10.3389/fnins.2021.643614. eCollection 2021.
Magnetometry based on nitrogen-vacancy (NV) centers in diamond is a novel technique capable of measuring magnetic fields with high sensitivity and high spatial resolution. With the further advancements of these sensors, they may open up novel approaches for the 2D imaging of neural signals . In the present study, we investigate the feasibility of NV-based imaging by numerically simulating the magnetic signal from the auditory pathway of a rodent brainstem slice (ventral cochlear nucleus, VCN, to the medial trapezoid body, MNTB) as stimulated by both electric and optic stimulation. The resulting signal from these two stimulation methods are evaluated and compared. A realistic pathway model was created based on published data of the neural morphologies and channel dynamics of the globular bushy cells in the VCN and their axonal projections to the principal cells in the MNTB. The pathway dynamics in response to optic and electric stimulation and the emitted magnetic fields were estimated using the cable equation. For simulating the optic stimulation, the light distribution in brain tissue was numerically estimated and used to model the optogenetic neural excitation based on a four state channelrhodopsin-2 (ChR2) model. The corresponding heating was also estimated, using the bio-heat equation and was found to be low (<2°C) even at excessively strong optic signals. A peak magnetic field strength of ∼0.5 and ∼0.1 nT was calculated from the auditory brainstem pathway after electrical and optical stimulation, respectively. By increasing the stimulating light intensity four-fold (far exceeding commonly used intensities) the peak magnetic signal strength only increased to 0.2 nT. Thus, while optogenetic stimulation would be favorable to avoid artefacts in the recordings, electric stimulation achieves higher peak fields. The present simulation study predicts that high-resolution magnetic imaging of the action potentials traveling along the auditory brainstem pathway will only be possible for next generation NV sensors. However, the existing sensors already have sufficient sensitivity to support the magnetic sensing of cumulated neural signals sampled from larger parts of the pathway, which might be a promising intermediate step toward further maturing this novel technology.
基于金刚石中氮空位（NV）中心的磁力测量是一种能够以高灵敏度和高空间分辨率测量磁场的新技术。随着这些传感器的进一步发展，它们可能为神经信号的二维成像开辟新途径。在本研究中，我们通过数值模拟来自啮齿动物脑干切片听觉通路（从腹侧耳蜗核，VCN，到内侧梯形体，MNTB）在电刺激和光刺激下的磁信号，研究基于NV成像的可行性。对这两种刺激方法产生的信号进行了评估和比较。基于已发表的VCN中球状浓密细胞的神经形态和通道动力学及其向MNTB中主细胞的轴突投射数据，创建了一个真实的通路模型。使用电缆方程估计了响应光刺激和电刺激的通路动力学以及发射的磁场。为了模拟光刺激，对脑组织中的光分布进行了数值估计，并基于四态通道视紫红质-2（ChR2）模型对光遗传学神经兴奋进行建模。还使用生物热方程估计了相应的加热情况，发现即使在光信号过强的情况下，加热也很低（<2°C）。电刺激和光刺激后，分别从听觉脑干通路计算出的峰值磁场强度约为0.5和0.1 nT。将刺激光强度增加四倍（远远超过常用强度），峰值磁信号强度仅增加到0.2 nT。因此，虽然光遗传学刺激有利于避免记录中的伪迹，但电刺激能实现更高的峰值场强。本模拟研究预测，只有下一代NV传感器才能对沿听觉脑干通路传播的动作电位进行高分辨率磁成像。然而，现有传感器已经具有足够的灵敏度来支持对从通路较大部分采样的累积神经信号进行磁传感，这可能是使这项新技术进一步成熟的一个有希望的中间步骤。
