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More on the Making of Brainiac Mice

Time to stir up the nature-versus-nurture debate a bit.

New research from Tufts University School of Medicine indicates that severity of learning disorders can not only be improved by enhancing a child's environment but enhancing the environment their mother was exposed to as an adolescent.

In the study, published in last week's Journal of Neuroscience, scientists found memory improvements induced in mice through exposure to enriched environments can be passed on to their next generation.

The research team, led by biochemistry professor Larry Feig, had previously shown that exposing juvenile mice to two weeks of enriched environments - those with novel objects, extra social interactions, and voluntary exercise opportunities - reversed genetically induced memory defects. The enriched environments unlocked a latent cellular mechanism involved in learning and memory called "long-term potentiation," which you may recall from last week's "Mice in the Ivory Tower." While the affect does eventually wear off throughout a mouse's lifetime, the team wanted to know if it lasted long enough to be passed on to their offspring.

To do this, the researchers placed 15 day old female mice with genetically-created learning disorders in enriched environments for two weeks. Then, months later, they assessed the memory function of the female's offspring.

Even though the new generation of mice had the same genetic defect and were never exposed to enriched environments, the memory improvement remained.

Interestingly, better nurturing by the mothers was not responsible for the better memory function. The scientists found the improved learning abilities were maintained whether or not the offspring were raised by their genetic mothers or "non-enriched," memory-deficient foster mothers.

The enhanced memory capabilities, however, were only passed on to the first generation of mice. The researchers theorize that the subsequent generations of mice expressed the original memory disorder because "the effects of [environmental enrichment] wears off faster in the offspring, such that it is not present when they become fertile."

The research team believes this is an example of epigenetics, when a change in inherited gene expression occurs without an actual alteration to DNA sequences. While the exact mechanism is not yet understood, it is likely the concentration of the proteins that trigger long-term potentiation are elevated in the mother such that they are passed to the offspring in concentrated amounts during pregnancy.

In their article, the researchers indicated their results could have significant implications for humans, saying, "If a similar phenomenon occurs in humans, the effectiveness of one's memory during adolescence, particularly in those with defective cell signaling mechanisms that control memory, can be influenced by environmental stimulation experienced by one's mother during her youth."

Now if only someone would finally get around to building a time machine, so we could tell our mothers to do a few more sets of jumping jacks before turning 13 ...