Hippocampus (image) Max-Planck-Gesellschaft Caption Mice lacking functional NMDA receptors in the dentate gyrus (DG) and in the CA1 region of their hippocampi (Grin1ΔDGCA1) can, just as normal control animals, locate the position of a hidden island in a pond, using external objects. If the island is marked by a beacon and a second identical beacon without an escape platform is located elsewhere, the genetically altered mice use, even after many trials, the beacons and not the orientation points to search for the island (see figure below). Example swimming patterns are shown as dotted arrows (wild type, black; Grin1ΔDGCA1 mouse, red). Credit MPI for Medical Research 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.