WASHINGTON – Scientists have trained rats to drive tiny cars in exchange for pieces of cereal, and found that learning the task lowered their stress levels. Their study not only demonstrates how sophisticated rat's brains are, but could one day help in developing new nonpharmaceutical forms of treatment for mental illness, said senior author Kelly Lambert of the University of Richmond in Virginia on Wednesday. Lambert said she had long been interested in neuroplasticity -- how the brain changes in response to experience and challenges -- and particularly wanted to explore how well rats that were housed in more natural settings ("enriched environments") performed against those kept in labs. She and colleagues modified a robot car kit by adding a clear plastic food container to form a driver compartment with an aluminum plate placed on the bottom. Copper wire was threaded horizontally across the cab to form three bars: left, center and right.