Scientists say they have discovered a "maintenance" protein that helps keep nerve fibres that transmit messages in the brain operating smoothly.
The University of Edinburgh team says the finding could improve understanding of disorders such as epilepsy, dementia, MS and stroke.
In such neurodegenerative disorders, electrical impulses from the brain are disrupted.
This leads to an inability to control movement, and muscles wasting away.
The brain works like an electrical circuit, sending impulses along nerve fibres in the same way that current is sent through wires.
These fibres can measure up to a metre, but the area covered by the segment of nerve that controls transmission of messages is no bigger than the width of a human hair.
The scientists discovered that the protein Nfasc186 is crucial for maintaining the health and function of the segment of nerve fibres - called the axon initial segment (AIS) - that controls transmission of messages within the brain.
They found that the AIS and the protein within it are important in ensuring the nerve impulse has the right properties to convey the message as it should.
Professor Peter Brophy, director of the University of Edinburgh's Centre for Neuroregeneration, said: "Knowing more about how signals in the brain work will help us better understand neurodegenerative disorders and why, when these illnesses strike, the brain can no longer send signals to parts of the body."
Dr Matthew Nolan, of the university's Centre for Integrative Physiology, said: "At any moment tens of thousands of electrical impulses are transmitting messages between nerve cells in our brains.
"Identifying proteins that are critical for the precise initiation of these impulses will help unravel the complexities of how brains work and may lead to new insights into how brains evolved."
The work was funded by the Wellcome Trust and the Medical Research Council.