Overall picture of the electrode (IMAGE) University of California - San Diego Caption The electrodes can record brain activity as deep as 10 cm/4 in inside the brain. They are just 15 micron thick, or one-fifth the width of a human hair, and 1.2 millimeters wide. Credit David Baillot/University of California San Diego Usage Restrictions Please credit 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.