Hippocampus (image) University of Pennsylvania School of Medicine Caption This is a mouse hippocampus expressing the Cre- virus. Credit Julie Blendy, Ph.D.; Brigitta Gunderson, Ph.D.; Perelman School of Medicine, University of Pennsylvania Usage Restrictions Please credit the names provided. 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.