The FDA has approved a new drug for Alzheimer's. But a lot of experts are skeptical about whether the drug works. Rhitu Chatterjee talks with science correspondent Jon Hamilton about the controversial drug aducanumab and why the U.S. Food and Drug Administration approved it. For more of Jon's reporting, read "For Those Facing Alzheimer's, A Controversial Drug Offers Hope."You can email Short Wave at ShortWave@NPR.org.