Evidence of grid cell activity has been seen in healthy volunteers asked to imagine moving through an environment. The study used fMRI scans to detect brain activity consistent with grid cell activity in the entorhinal cortex, an important 'hub' for navigation and memory. The entorhinal cortex is one of the first areas affected by Alzheimer's disease, so the latest research could help to explain why people with Alzheimer's can have problems imagining as well as remembering things.