Such “epigenetic markings” tend to diminish with age, but in the animals with stimulating living conditions, the decrease in methyl groups was comparatively small. Thus, in old mice raised in a varied environment, gene activity had, in a sense, remained young. In particular, this affected a series of genes relevant to growing new neurons and cellular connections in the hippocampus. “Epigenetically, these animals retained a younger hippocampus,” Kempermann says. Therefore, the brains of these mice were more malleable – experts speak of greater “neuroplasticity” – than in conspecifics of the same age that had grown up in a low-stimulus environment.
The current study did not include behavioral experiments. However, Kempermann points out that many other studies have shown that mice raised in high-stimulus settings perform better on memory tests than those from low-stimulus environments. “It is fair to assume that this mental fitness is due to the stabilization of methylation patterns that we observed,” the neuroscientist says. “Of course, the question is to what extent our findings also apply to humans. Here, the situation is likely to be more complicated. After all, it is about how living conditions influence behavior and the way humans react to external stimuli is much more complex than in mice. However, we have good reasons to believe that the basic epigenetic principles are the same in humans as in mice.”