Aim

Aiming at analysing the signal conduction in muscular fibres, the spatio-temporal dynamics of the magnetic field generated by the propagating muscle action potential (MAP) is studied.

Method

In this prospective, proof of principle study, the magnetic activity of the intrinsic foot muscle after electric stimulation of the tibial nerve was measured using optically pumped magnetometers (OPMs). A classical biophysical electric dipole model of the propagating MAP was implemented to model the source of the data. In order to account for radial currents of the muscular tubules system, a magnetic dipole oriented along the direction of the muscle was added.

Results

The signal profile generated by the activity of the intrinsic foot muscles was measured by four OPM devices. Three OPM sensors captured the spatio-temporal magnetic field pattern of the longitudinal intrinsic foot muscles. Changes of the activation pattern reflected the propagating muscular action potential along the muscle. A combined electric and magnetic dipole model could explain the recorded magnetic activity.

Interpretation

OPM devices allow for a new, non-invasive way to study MAP patterns. Since magnetic fields are less altered by the tissue surrounding the dipole source compared to electric activity, a precise analysis of the spatial characteristics and temporal dynamics of the MAP is possible. The classic electric dipole model explains major but not all aspects of the magnetic field. The field has longitudinal components generated by intrinsic structures of the muscle fibre. By understanding these magnetic components, new methods could be developed to analyse the muscular signal transduction pathway in greater detail. The approach has the potential to become a promising diagnostic tool in peripheral neurological motor impairments.

中文翻译：

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光泵磁力计揭示了肌肉动作电位的磁场分量

目标

为了分析肌肉纤维中的信号传导，研究了由传播的肌肉动作电位（MAP）产生的磁场的时空动态。

方法

在这项前瞻性的原理研究中，使用光泵磁力计（OPM）测量了胫神经电刺激后固有足部肌肉的磁活动。实现了传播MAP的经典生物物理电偶极子模型来对数据源进行建模。为了说明肌肉小管系统的径向电流，添加了沿肌肉方向定向的磁偶极子。

结果

由脚部固有肌肉的活动产生的信号轮廓通过四个OPM设备进行了测量。三个OPM传感器捕获了纵向足内在肌肉的时空磁场模式。激活模式的变化反映了沿肌肉传播的肌肉动作电位。电磁偶极子模型可以解释所记录的磁活动。

解释

OPM设备允许使用一种新的，非侵入性的方式来研究MAP模式。由于与电活动相比，偶极子源周围的组织对磁场的影响较小，因此可以对MAP的空间特征和时间动态进行精确分析。经典的电偶极子模型解释了磁场的主要而非全部方面。该场具有由肌肉纤维的固有结构产生的纵向分量。通过了解这些磁性成分，可以开发出新方法来更详细地分析肌肉信号转导途径。该方法有可能成为周围神经运动障碍的有前途的诊断工具。