Axonal swelling (IMAGE) University of Zurich Caption Cross-section of nerve fibers from the mouse optic nerve: The dark dense lines show the insulating layer, the myelin. Highlighted in red is a swollen, clogged area of an impaired nerve fiber – caused by non-functioning oligodendrocytes. Credit Zoe Looser and Aiman Saab, University of Zurich Usage Restrictions non License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.