It is never too early to start enriching a child's mind, some claim, which is why many pregnant women read aloud to their unborn babies or expose them to classical music. A new study in mice suggests that truly diligent mothers-to-be can begin such efforts even earlier—before their children are even conceived.

Environmental enrichment is known to benefit brain function in animals, and previous research led by Larry Feig (Tufts University School of Medicine, Boston, MA) found that young mice that were exposed to enrichment showed improvements in long-term potentiation, a synaptic mechanism associated with learning and memory. Now, Feig and colleagues have discovered that enriched female mice can pass these benefits on to their future offspring (J. Neurosci. 29, 1496–1502; 2009).

Credit: Sarah Salmela

The researchers examined wild-type mice and mutant mice with genetically engineered defects in long-term potentiation and in memory formation. For several hours a day for two weeks, juvenile mice were given access to enrichment items such as running wheels, toys and nesting material. The mice were later mated, and their offspring, which were raised in a barren environment, were evaluated at age 30 days.

Remarkably, compared with pups born to nonenriched dams, wild-type pups born to enriched dams showed enhanced long-term potentiation (evaluated by assays on hippocampal slices), even though the pups themselves had never been exposed to enrichment. In mutant mice born to enriched dams, defects in long-term potentiation were completely 'rescued'. Though the memory-forming ability of these mice was still slightly impaired, they performed better in a memory acquisition task than did mutant mice born to nonenriched dams. The benefits were transient, disappearing by the time mice were about 3 months old.

The effects of enrichment were passed on by the dam only (it did not matter whether the sire had been exposed to enrichment) and were transmitted to only one generation. The effects were not a result of nurturing: when biological offspring of enriched dams were raised by nonenriched foster females, the effects were still observed, whereas pups born to nonenriched mothers but raised by enriched foster females did not show enhanced long-term potentiation or memory acquisition.

This research suggests that exposure to environmental enrichment can create heritable traits that are not reflected in changes to DNA structure. Feig and colleagues speculate that the source of the effect may be hormonal and are currently working to uncover the mechanisms underlying it.