An anonymous reader writes "According to new study published in Nature (abstract), MIT researchers have figured out how to trigger specific memories in rats by hitting certain neurons with a pulse of light. From the article: 'The researchers first identified a specific set of brain cells in the hippocampus that were active only when a mouse was learning about a new environment. They determined which genes were activated in those cells, and coupled them with the gene for channelrhodopsin-2 (ChR2), a light-activated protein used in optogenetics. The light-activated protein would only be expressed in the neurons