In his twenties, Mike Merzenich dreamed of mapping the neurobiology of the soul. "I was interested in the genesis of the self," he says. Four decades later, he has scaled back his ambitions. Now a graying 64, he hopes merely to reverse the toll of aging on the brain and cure schizophrenia. Without surgery or drugs. Merzenich, a neuroscience professor at the University of California at San Francisco, aspires to "fix" brains with a series of innovative computer programs that he and his colleagues have designed. His work relies on a process called plasticity -- the brain's innate capacity to reshape itself and even increase its complexity throughout a lifetime, depending on experience. "We're going to revolutionize the way an older person looks at the end of life," he vows.
