Emotion seemed to fuel plenty of sighs by Humphrey Bogart's character Rick (right) in the 1942 film classic Casablanca, and even Rick's good friend Sam, played by actor Dooley Wilson, couldn't console him. Archive Photos/Getty Images hide caption

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Jeffrey Iliff (left), a brain scientist at Oregon Health & Science University, has been studying toxin removal in the brains of mice. He'll work with Bill Rooney, director of the university's Advanced Imaging Research Center, to enroll people in a similar study in 2016. Courtesy of Oregon Health & Science University hide caption

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Brain imaging experiments found patterns associated with attention span. iStockphoto hide caption

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An image from the Allen Institute's Brain Explorer shows gene expression across the human brain. Courtesy of Allen Institute For Brain Science hide caption

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Neuroscientist Takashi Kitamura works in the lab of Nobel laureate Susumu Tonegawa at the Massachusetts Institute of Technology. One of their recent projects helped identify a brain circuit involved in processing the "where" and "when" of memory. "Ocean cells" (red) and "island cells" (blue) play key roles. Takashi Kitamura/MIT hide caption

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Researchers have used MRI scanners to learn that preemies are born with weak connections in some critical brain networks. iStockphoto hide caption

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Alan Hoffman, shown with his wife, Nancy, at their home in Dumfries, Va., found that his Parkinson's symptoms improved when he took a cancer drug. Claire Harbage for NPR hide caption

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Rough night? Depending on specific tweaks to their genes, some fruit flies have trouble falling asleep, and others can't stay asleep. Getting too little shut-eye hurts their memory. David M. Phillips/Science Source hide caption

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