Michael Arnott, of Cambridge, Mass., says he used to have trouble staying awake on long drives. Sleep specialists discovered he has obstructive sleep apnea, though not for the most common reasons — he isn't overweight, and doesn't smoke or take sedatives. M. Scott Brauer for NPR hide caption

itoggle caption M. Scott Brauer for NPR

A nanosecond pulsed laser beam starts the photoacoustic imaging process. Geoff Story/Courtesy of Washington University in St. Louis hide caption

itoggle caption Geoff Story/Courtesy of Washington University in St. Louis

Giedre (left) and Tal Cohen in March 2013, while Giedre was still healthy. Since then, she's begun having symptoms of Alzheimer's disease. In Giedre's case, the illness is tied to a rare genetic mutation she inherited. Courtesy of Tal Cohen hide caption

itoggle caption Courtesy of Tal Cohen

Women with mild cognitive impairment, which can be a precursor to Alzheimer's, tend to decline faster than men. Lizzie Roberts/Getty Images/Ikon Images hide caption

itoggle caption Lizzie Roberts/Getty Images/Ikon Images

In this colorized image of a brain cell from a person with Alzheimer's, the red tangle in the yellow cell body is a toxic tangle of misfolded "tau" proteins, adjacent to the cell's green nucleus. Thomas Deerinck/NCMIR/Science Source hide caption

itoggle caption Thomas Deerinck/NCMIR/Science Source

"Shout, shout, let it all out. These are the things I can do without." Simone Golob/Corbis hide caption

itoggle caption Simone Golob/Corbis
Roy Scott/Ikon Images/Corbis

Joy (left, voiced by Amy Poehler) and Sadness (voiced by Phyllis Smith) catch a ride on the Train of Thought in Pixar's Inside Out. The movie opens in theaters nationwide June 19. Disney/Pixar hide caption

itoggle caption Disney/Pixar

Kanzi the bonobo (a species closely related to chimps) holds a pan of vegetables he cooked at the Great Ape Trust in Des Moines, Iowa, November 2011. Kanzi was taught to cook. However, a new study is the first to show that animals can acquire a cooking-like skill on their own. Laurentiu Garofeanu/Barcroft Media /Landov hide caption

itoggle caption Laurentiu Garofeanu/Barcroft Media /Landov

Experimental medicines related to ketamine, an anesthetic and club drug, are making progress in clinical tests. Wikipedia hide caption

itoggle caption Wikipedia

Sam Swiller and his dog, Sully, in their home in Washington, D.C. Meredith Rizzo/NPR hide caption

itoggle caption Meredith Rizzo/NPR

The Allen Cell Types Database catalogs all sorts of details about each type of brain cell, including its shape and electrical activity. These cells, taken from the visual area of a mouse brain, are colored according to the patterns of electrical activity they produce. Courtesy of Allen Institute for Brain Science hide caption

itoggle caption Courtesy of Allen Institute for Brain Science

The ill-fated Sultana in Helena, Ark., just before it exploded on April 27, 1865, with about 2,500 people aboard. Most were Union soldiers, newly released from Confederate prison camps. Library of Congress hide caption

itoggle caption Library of Congress

A color-enhanced cerebral MRI showing a glioma tumor. Scott Camazine/Science Source hide caption

itoggle caption Scott Camazine/Science Source