Researchers Discover a Secret of the Neuronal Communication Code

Researchers at the HUN-REN Institute of Experimental Medicine (HUN-REN IEM) have deciphered how nerve cells (neurons) transmit uniform signals to each other, writes the website of the Hungarian research institute.

The researchers studied action potentials along segments of axons (elongated extensions) of varying diameters and found that these signals act as true digital signals, ensuring communication between neurons. The results were published in the scientific journal PLOS Biology with János Brunner as lead author.

The researchers, led by János Szabadics, used state-of-the-art technologies to study the behavior of action potentials along axonal segments of varying diameters. Due to the small size of axons, such detailed measurements had not been possible before.

A key communication tool of neurons is the action potential, a brief electrical impulse that travels along the axon, a projection of neurons that rapidly transmits information to other neurons, glands, or muscles,

the article states.

Disruption of this process can lead to serious neurological problems, such as epilepsy or muscle weakness.

However, the axon is not a simple tubular structure. It is more like an uneven string of pearls with segments of varying diameters. The diameter has a significant effect on the propagation of electrical signals, and as such, should theoretically influence the course of the action potential.

The researchers first examined the mossy fiber axons in the hippocampus (part of the brain responsible for memory and learning). Using electrophysiological measurements, optical techniques, and computational analyses, the researchers demonstrated that the shape of the action potential remains constant.

The research has revealed that the constant shape of the action potential is due to the uneven distribution of certain ion channels. A particular group of potassium channels, called the Kv1 family, is not uniform along the axon. In the narrower segments, where the electrical signal would naturally slow down, the Kv1 channels have a greater effect, accelerating the course of action potential.

As a result, the shape of the action potential remains the same along axonal segments of all diameters. The action potential thus acts as a real “digital” signal.

The researchers also examined action potentials in other types of axons that do not have unusually large structures but vary in diameter, similar to the axonal projections of most known neurons, according to the article. They found that while the shape of the action potential may vary between different axon types, the diameter within a given axon type does not affect the shape of the signal. The findings of the HUN-REN researchers shed new light on the functioning of neurons.