Prior experience with complexity leads to more effective patterns of exploration in an unreinforced novel complex environment, improves learning, and alters patterns of encoding in output stages of hippocampus. Illustration: A rat faces a novel complex arena with various objects, barriers, and multiple possible paths to each location. Its trajectory over one 30 min session reflects the structure of the arena; enriched rats display an exploration strategy that breaks the task up via initially more frequent forays into smaller, more “digestible” parts. Maps of hippocampal encoding sites reveal synaptic changes are concentrated in output stages of hippocampus for enriched compared to control rats.
