In sighted people, the part of the brain that recognizes faces is linked to the brain's visual system. But in blind people it seems wired to circuits that process sound. Tina Zellmer/Ikon Images/Corbis hide caption

itoggle caption Tina Zellmer/Ikon Images/Corbis

A tangle of protein (green) in this scanning electron micrograph of a brain cell of an Alzheimer's patient lies within the cytoplasm (blue) of the cell. The tangle consists of clumps of a toxic form of tau. Thomas J. Deerinck/Corbis hide caption

itoggle caption Thomas J. Deerinck/Corbis

A screen presents the winners of the Nobel Prize in Medicine, U.S.-British scientist John O'Keefe and Norwegian husband and wife Edvard Moser and May-Britt Moser, for their discoveries of cells that constitute a positioning system in the brain. TT News Agency/Reuters/Landov hide caption

itoggle caption TT News Agency/Reuters/Landov

Dr. Allan Ropper speaks with residents and fellows as they do rounds at the neuroscience intensive care unit at Brigham and Women's Hospital in Boston. M. Scott Brauer for NPR hide caption

itoggle caption M. Scott Brauer for NPR

Klotho (right) is one of the three Greek Fates depicted in this Flemish tapestry at the Victoria and Albert Museum in London. Wikimedia Commons hide caption

itoggle caption Wikimedia Commons

People smoke marijuana, presumably, because it affects their brains, not despite that fact. Above, people in Sao Paulo, Brazil, campaign for the legalization of marijuana. Nelson Almeida/AFP/Getty Images hide caption

itoggle caption Nelson Almeida/AFP/Getty Images

Images of the developing fetal brain show connections among brain regions. Allen Institute for Brain Science; Bruce Fischl, Martinos Center for Biomedical Imaging, Massachusetts General Hospital hide caption

itoggle caption Allen Institute for Brain Science; Bruce Fischl, Martinos Center for Biomedical Imaging, Massachusetts General Hospital