Researchers have only recently been able to use brain scans to detect Alzheimer's risk factors in living people. iStockphoto hide caption

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Having a perfect memory can put a strain on relationships, because every slight is remembered. Katherine Streeter for NPR hide caption

itoggle caption Katherine Streeter for NPR

A newly discovered neural circuit in the brain of the common fruit fly seems to serve as a sort of "volume control," turning up and down the perception of sound and light. Nicholas Monu/iStockphoto hide caption

itoggle caption Nicholas Monu/iStockphoto

A technique called optogenetics is being used in the laboratory to observe and control what brain circuits are doing in real time. Henning Dalhoff/Getty Images/Science Photo Library RM hide caption

itoggle caption Henning Dalhoff/Getty Images/Science Photo Library RM

Surgeons use a grid of electrodes laid on a patient's brain. They record electrical activity and can deliver a tiny jolt. Courtesy of Dr. Josef Parvizi hide caption

itoggle caption Courtesy of Dr. Josef Parvizi

Children under age 2 can reason abstractly, researchers say. Jandrie Lombard/iStock hide caption

itoggle caption Jandrie Lombard/iStock

President Obama has pledged millions of dollars to fuel research into understanding the workings of the human brain. Zephyr/Science Source hide caption

itoggle caption Zephyr/Science Source

A brain that can let other thoughts bubble up despite being in pain might help its owner benefit from meditation or other cognitive therapies. iStockphoto.com hide caption

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Illustration by Daniel Horowitz for NPR