Solitary electromechanical pulses in Lobster neurons

TL;DR

This study provides ultrasensitive measurements of mechanical changes in lobster neurons, showing that nerve pulses involve electromechanical solitons that propagate without dissipation and can pass through each other.

Contribution

The paper presents modern ultrasensitive AFM recordings revealing mechanical nerve pulse dynamics, supporting the electromechanical soliton hypothesis in neurons.

Findings

Mechanical nerve thickness changes are in phase with voltage.

Colliding nerve pulses pass through each other without annihilation.

Mechanical phenomena are integral to nerve impulse propagation.

Abstract

Investigations of nerve activity have focused predominantly on electrical phenomena. Nerves, however, are thermodynamic systems, and changes in temperature and in the dimensions of the nerve can also be observed during the action potential. Measurements of heat changes during the action potential suggest that the nerve pulse shares many characteristics with an adiabatic pulse. First experiments in the 1980s suggested small changes in nerve thickness and length during the action potential. Such findings have led to the suggestion that the action potential may be related to electromechanical solitons traveling without dissipation. However, they have been no modern attempts to study mechanical phenomena in nerves. Here, we present ultrasensitive AFM recordings of mechanical changes on the order of 2 - 12 {\AA} in the giant axons of the lobster. We show that the nerve thickness changes in phase with voltage change. When stimulated at opposite ends of the same axon, colliding action potentials pass through one another and do not annihilate. These observations are consistent with a mechanical interpretation of the nervous impulse.