A Single Engram Cell (IMAGE) RIKEN Caption This image depicts a single memory engram cell in the hippocampal dentate gyrus region of a mouse model of early Alzheimer's disease. To optically manipulate specific connections to these engram cells, a blue light-sensitive protein oChIEF was expressed in an upstream brain region, i.e., medial entorhinal cortical inputs (red) to the DG. The majority of DG granule cells were not active during engram labeling (blue, non-engram cells). Credit RIKEN Usage Restrictions credit RIKEN License Licensed content 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.