Scientists found that when rats get rewards at certain places, their mental map of the location gets redrawn. Their experiment had two open-top boxes, the bottom of each scattered with crushed cereal. The rats were able to forage around freely and eat any crumbs they found in both, but one box was special: it had an unmarked reward zone in one corner.
Rats learned that if they navigated to this reward zone when they heard a certain sound, they got a guaranteed cereal reward that was bigger and better than the scattered crumbs. It was kind of like a store giving out free samples at a certain aisle for a limited time after announcing it over a loudspeaker.
The rats had electrodes connected to their heads, which told scientists that some types of cells related to spatial mapping changed their firing patterns when the rats got near the reward zone, regardless of whether the cue had sounded, which implied that the rats had a higher spatial resolution of the reward location.
In other words, the rats had developed new mental maps where they could see the reward location better after learning its significance.