Leaks in a barrier between blood vessels and brain cells could contribute to the development of Alzheimer's. VEM/Science Source hide caption

itoggle caption VEM/Science Source

Spinal MRIs similar to these found infections that many patients hadn't realized they had. Stefano Raffini/iStockphoto.com hide caption

itoggle caption Stefano Raffini/iStockphoto.com

Who's there? A radiologist studies digital X-rays in a viewing room at what is now called the Walter Reed National Military Medical Center in Bethesda, Md. Seth Rossman/U.S. Navy hide caption

itoggle caption Seth Rossman/U.S. Navy

The warmer orange colors show parts of the brain most active during improvisational rap. The blue regions are most active when rappers performed a memorized piece. NIDCD hide caption

itoggle caption NIDCD