In 1982, Dr. Francisco Lopera, a Medellin neurologist, was puzzled. A 47-year-old patient was losing his memory, and so had his father, grandfather and seven other relatives. Other cases appeared. Lopera asked one, a 45-year-old lottery-ticket seller, to redraw portraits he had sketched years earlier; the deformed results showed already significant neurological damage. Patients' families said this 'madness' or 'idiocy,' called La Bobera, came from witchcraft, a tree, a Spaniard's statue, a priest angry about being burglarized. Lopera burned to help. His grandfather had had late-onset dementia. He came from the patients' violence-scarred region, Antioquia. Lopera spent years investigating the dementia with two assistants, Lucia Madrigal and Liliana Cadavid. They scoured parish lists, wills, and birth, death, baptism and marriage records. Building elaborate genealogies revealed 25 families all related via a couple of Spanish descent: Javier San Pedro Gomez, born around 1745, and Maria Luisa Chavarriaga Mejia. Determining what La Bobera was required dissecting a brain, but people believed that would leave someone 'completely disfigured,' Lopera said. Then, in 1995, in the village of Angostura 56-year-old Libia Rosa Pineda, died. Lopera telephoned the family: 'Can we have the brain?' No. He contacted Angostura's mayor, priest, and hospital director. No. He and a pathologist drove there, attended the funeral, and beseeched Pineda's 14 children. All agreed but one, a gold-chain-draped policeman linked to narcotraffickers. Finally, minutes before the brain would be scientifically useless, the family appeared, the brother, wildly drunk, demanding 20 million pesos, saying, 'You're going to sell the body to the gringos.' Lopera refused. Ultimately, the brother capitulated, the pathologist removed the brain, and, Lopera said, 'We got out of town.' The brain, in formaldehyde in the pathologist's hand luggage, traveled to the Massachusetts home of Dr. Kenneth S. Kosik, a neuroscientist. He detected telltale Alzheimer's plaques. Now it sits in Lopera's brain bank, with other brains elicited by praying at funerals. 