By zapping mouse brains with blue and yellow light beams, scientists have manipulated the animals' social behaviors, according to a study published 27 July in Nature. The report bolsters the popular hypothesis that autism stems from an imbalance between excitatory and inhibitory signals in the brain.Using a technique called optogenetics, the researchers engineered mice to carry light-sensitive proteins in excitatory neurons in the prefrontal cortex, a brain region involved in learning and social behavior. Stimulating these neurons with light raised their firing rates for about a half an hour. During that period, the animals were not interested in sniffing or interacting with other mice, presumably as a result of the increased excitation."They were completely uninterested in engaging socially," says lead investigator Karl Deisseroth, professor of bioengineering and psychiatry at Stanford University in Palo Alto, California. "It was a very profound difference — one of most profound behavioral differences we’ve seen in all our work."Read more at...SFARI, August 2011.