It was at this point in her life, while she was twenty-eight and still in graduate school, that a paper came across her desk. Mark Rosenzweig of the University of California at Berkeley had studied rats in stimulating and nonstimulating environments, and in postmortem exams he found that the brains of the stimulated rats had more neurotransmitters, were heavier, and had better blood supply than those from the less stimulating environments. He was one of the first scientists to demonstrate neuroplasticity by showing that activity could produce changes in the structure of the brain.
