Finding our way in our daily environment is essential for survival, but how do we do it? The answer to this question is relevant to understanding dementia. Mice are a useful experimental model here. A mouse receives a lot of information about its environment and must decide in every situation what information is most helpful and what is misleading. Nerve cells of the central region of the brain, the hippocampus, use NMDA receptors not to store information about the environment, but instead to recognize, judge and decide which items of information are most useful.