Both Genetic and Environmental Changes Can Enhance Learning and Memory.

This review discusses two papers from the same lab that directly compared the effects of genetic enhancement with environmental enrichment on learning and memory in mice. In the first study mice were genetically manipulated to have an increased expression of the NR2B component of the NMDA receptor, associated with learning. These transgenic (Tg) mice showed greater current flow, larger EPSPs, and improved learning and memory on a variety of tasks. In the second experiment both the Tg mice and normal wild type (Wt) mice were raised in either a standard environment or given an enriched environment for two weeks. The differences in behavior and in receptor expression were compared among the four groups. The enriched Wt mice performed as well as both Tg groups on measures of fear conditioning. For the more difficult task of novel object recognition the enriched Wt mice performed as well as the Tg raised in a standard environment, but the enriched Tg mice performed significantly better than all other groups. Environmental enrichment caused an increase in receptor expression in both the Wt and Tg groups, but the Tg enriched mice had the highest expression levels. These papers clearly demonstrated that the mice's environmental enrichment caused behavioral differences for both Wt and Tg-enriched mice - with important implications for humans. They also raise questions about how a lab animal's environment might change its brain and/or behavior, with a potential impact on the results of studies using animals raised in impoverished conditions.