Have you ever noticed that when you think a lot, you feel tired? New research shows that there is a reason (MSN.com, August 11, 2022)! When we tax our brains during a “long, grueling day sitting at a desk,” a chemical by-product is released (glutamate) that is toxic to the brain. We produce this chemical when we use our brains heavily, and it builds up in the pre-frontal cortex.