Engineering Memory (image) NIH/National Institute of Mental Health Caption Scientists have switched a fear memory on and off in genetically-engineered rats -- using a flash of light. Optogenetic technology produced this first cause-and-effect evidence that memories are formed by strengthened connections between neurons. Credit Roberto Malinow, M.D., Ph.D., of the University of California, San Diego Usage Restrictions None Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.