A Physical Perspective to the Inductive Function of Myelin—A Missing Piece of Neuroscience
Authors: Yansong Qu
Jiahui Wang
Tianzhun Wu
Hao Wang
Guangyi Cai
Yonghong Liu
Journal: Frontiers in Neural Circuits (2021)
Discipline: NEUROSCIENCE & BEHAVIOR
Keywords: magnetic nerve stimulation; magnetic resonance imaging; myelin; opposite spiraling; piezoelectric cell membrane.
Affiliations: Institute of Biomedical & Health Engineering, Shenzhen Institutes of Advanced Technology (SIAT), Chinese Academy of Sciences (CAS), Shenzhen, China., Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore., Key Laboratory of Health Bioinformatics, Chinese Academy of Sciences, Shenzhen, China.

Abstract:  Starting from the inductance in neurons, two physical origins are discussed, which are the coil inductance of myelin and the piezoelectric effect of the cell membrane. The direct evidence of the coil inductance of myelin is the opposite spiraling phenomenon between adjacent myelin sheaths confirmed by previous studies. As for the piezoelectric effect of the cell membrane, which has been well-known in physics, the direct evidence is the mechanical wave accompany with action potential. Therefore, a more complete physical nature of neural signals is provided. In conventional neuroscience, the neural signal is a pure electrical signal. In our new theory, the neural signal is an energy pulse containing electrical, magnetic, and mechanical components. Such a physical understanding of the neural signal and neural systems significantly improve the knowledge of the neurons. On the one hand, we achieve a corrected neural circuit of an inductor-capacitor-capacitor (LCC) form, whose frequency response and electrical characteristics have been validated by previous studies and the modeling fitting of artifacts in our experiments. On the other hand, a number of phenomena observed in neural experiments are explained. In particular, they are the mechanism of magnetic nerve stimulations and ultrasound nerve stimulations, the MRI image contrast issue and Anode Break Excitation. At last, the biological function of myelin is summarized. It is to provide inductance in the process of neural signal, which can enhance the signal speed in peripheral nervous systems and provide frequency modulation function in central nervous systems. 

Retracted: No

PubPeer comments:
 Focusing on the **inductance** of the myelin sheath seems irrelevant. According to the authors its inductance is in the nanohenry range. Accepting this at face value, it appears nevertheless to lead to an utterly negligible impedance. $Z = i omega L$ With a characteristic frequency of 1 kHz and the quoted inductance value, we achieve an approximate impedance of 1e3 Hz * 1e-9 H = 1e-6 $Omega$. It is hard to see the relevance of such an impedance in a biological setting. Fig. 2. ![image] , 
 Thanks for your comment. If you only check the impedance of the inductance generated by the myelin, the value is quite small. However, the spiraling current within the myelin sheath generates a magnetic field. This magnetic field, at least, determines the spiraling direction of adjacent myelin sheaths. This is the reason that adjacent myelin sheaths on the same axon have the opposite spiraling directions, and myelin sheaths on the adjacent axons have the same spiraling direction. I am happy to know if there is an alternative theoretical explanation for these phenomena. As seen, its biological importance is based the experimental observation, not calculation. Meanwhile, there is another equivalent inductance generated by the flexoelectric effect of the plasma membrane, in which myelin sheath is also involved. (This is also an importance part of this paper.)The value of this equivalent inductance is huge, which is also confirmed by the original paper of H-H model. It has such a huge value and huge biological importance, which is still neglected for more than half century. So personally, I do not see any reason should we evaluate the biological importance based on some calculation value. Since anything which is contradictory with current mainstream theory will always be considered as  not important . ,