The pilot killed Saturday in a light plane crash near Borrego Springs was a renowned Alzheimer's researcher at the University of California, San Diego, it was reported Monday.Dr. Leon J. Thal, 62, the chairman of UCSD's neurosciences department, died when his Mooney M20 crashed in mountainous terrain about eight miles southwest of the Borrego Valley Airport, according to The San Diego Union Tribune.Thal, who was flying alone, took off at San Diego's Montgomery Field at about 6:15 p.m., Federal Aviation Administration duty officer Bruce Nelson said.Thal's wife, neuropsychologist Donna Thal, a professor emeritus at San Diego State University, notified authorities Saturday night when her husband failed to arrive in Borrego Springs, Vicky Cole, manager of the Borrego Springs airport told the Union-Tribune.Volunteers with the California Civil Air Patrol picked up a distress signal from Thal's plane at about 10 p.m.Sheriff's deputies reached the crash by helicopter and found the body in the plane at about 1 a.m.The National Transportation Safety Board is in charge of the investigation.Thal directed the Alzheimer's Disease Cooperative Study, a consortium of more than 70 research centers in the United States and Canada that investigates experimental therapies. Thal also managed UCSD's Shiley-Marcos Alzheimer's Disease Research Center.Thal was born in New York City in 1944. He earned a medical degree from the State University of New York's Downstate Medical Center in Brooklyn and received his neurology training at the Albert Einstein College of Medicine in the Bronx, according to the newspaper.Thal took a job at UCSD in 1985 as an associate professor of neurosciences. In 1993, he was named department chair.