The hippocampus continues to add new neurons even in adulthood. When animals are housed in 'enriched' or stimulating environments with opportunities for exercise and/or games, they show greater neurogenesis in the hippocampus. Animals exposed to these more complex cages also show improvements in several tasks of memory and anxiety.

A study by René Hen and colleagues on page 729 reports, however, that there is no link between the increased neurogenesis that comes with enriched environments and improvements in the memory tasks. The authors used a focused dose of radiation to prevent neurogenesis selectively in the hippocampus of mice before placing them in enriched cages. When tested six weeks later on an anxiety and spatial memory task, these animals still did better than animals housed in standard cages, suggesting that the lack of neurogenesis did not matter to their learning ability.