Missing Myelin Disrupts Vital Brain Signal Transmission in Mice

Recent research by a team led by Maarten Kole at the Netherlands Institute for Neuroscience has unveiled critical insights into the role of myelin in the rapid transmission of signals in the brain. The study, published in March 2025 in the journal Nature Communications, highlights how the absence of this protective layer around nerve cells impacts communication between the cerebral cortex and the thalamus, a key relay station in the brain.

Myelin acts as insulation for nerve fibers, enabling swift signal transmission across long distances. The study focused on mice to understand the implications of myelin loss, particularly in the corticothalamic loop, which is crucial for processing sensory information. When mice use their whiskers to explore their surroundings, this loop facilitates effective communication between the brain’s outer layer and the thalamus. The findings emphasize the significance of these loops not only in mice but also in human cognitive functions.

To investigate the effects of myelin degradation, the researchers introduced a toxic substance that targeted myelin. Contrary to expectations that the entire nerve fiber would be affected, the degradation occurred predominantly near the cell bodies. This mimics the development of lesions seen in Multiple Sclerosis (MS), where cognitive impairments can emerge, leading to challenges such as difficulty recalling familiar names or navigating environments.

The team’s analysis revealed that the loss of myelin results in both slower and less consistent signal transmission to the thalamus. Kole noted, “We had anticipated this, because myelin is known to be essential for fast signal transmission, but what was new to us was that we lost the first wave of signals entirely.” He likened this phenomenon to a barcode scanner that fails to recognize an item when the initial part of the barcode is missing, emphasizing the importance of complete myelin coverage for effective signal processing.

This disruption in communication has profound implications. When a mouse’s whiskers touch an object, the cerebral cortex amplifies the thalamic signals, allowing for accurate identification of the object’s nature and location. The research demonstrated that while this amplification still occurs following myelin loss, it is less precise. Consequently, the communication loop between the cerebral cortex and thalamus is compromised, leading to a decreased ability to identify stimuli accurately.

The findings shed light on the anatomical characteristics of specific nerve cells and their myelin sheathing. Kole explained, “We’ve known for a while that these cells are wrapped in myelin in a very particular way. Now we finally understand why that’s the case.” This knowledge lays the groundwork for further exploration into the cognitive symptoms associated with grey matter lesions, which are often more severe and carry a poorer prognosis for individuals with MS.

Understanding how myelin loss alters the brain’s communication codes is crucial for developing strategies to mitigate cognitive issues. The research underscores the need for future studies aimed at exploring potential recovery methods for myelin damage, which could lead to alleviating symptoms associated with grey matter lesions.

Kole’s team aims to uncover pathways for restoring myelin integrity in the hopes of improving outcomes for individuals suffering from the debilitating effects of MS. As research progresses, these insights may pave the way for innovative treatments that address the cognitive challenges faced by those affected by this condition.