Cognition abilities contribute to educational and occupational achievement, daily function and motor performance. Unfortunately, cognitive performance declines on average in late life and the prevalence of dementia nearly doubles every five years after the age of 65 years. Over a million people in Canada will have dementia within a generation, as more people live to ages when dementia is common. My research aims to identify ways to optimize cognition across the life course and to prevent dementia in late life. In particular, I investigate the relationship between physical exercise, cognition and brain function using techniques from several disciplines including neuroscience, exercise physiology and epidemiology.