Athletic Mice Have Bigger Midbrains, UC Riverside Research Shows

Study shows mice bred for athleticism have larger midbrains than "regular" mice

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    NEWSLETTERS

    UCR Department of Biology
    The mouse on left was bred for its voluntary high level of wheel-running, while the mouse on right is a control. New UCR research found exercising-loving mice have 13 percent larger midbrains.

    Jocks, often stereotyped as dolts, may actually have bigger brains, new research produced by the University of California at Riverside suggests.

    Jock mice, that is, and only part of their brains are larger than non-exercise-loving mice.

    A study published this week found that mice bred selectively for athleticism had significantly bigger midbrains – a region of the brain important for reward-learning, motivation and reinforcing behavior – than their non-athletic peers.

    For 20 years, a UCR lab run by biology professor Theodore Garland and colleagues has bred mice for their voluntary affinity for running on exercise wheels, calling them "high-runner" mice. They wanted to find out if breeding for a particular trait led to an increase in brain size.

    Overall, it didn't. But after dissecting the rodent brains, researchers found that the volume of midbrains were nearly 13 percent larger in high-runner mice than in regular mice.

    The result answered another question they had posed: whether the change in brain size would be seen over the entire brain or only in certain sections. The latter finding supports a "mosaic" theory of brain evolution, Garland told UCR Today.

    The study is the first to show that selective breeding for a "particular mammalian behavior" caused a change in the size of a brain region, according to the research, which was published Jan. 16 in the Journal of Experimental Biology (PDF).

    It's not clear what the implications are for human athletes' brains.

    "It is possible that individual differences in the propensity or ability for exercise in humans are associated with individual differences in the size of the midbrain, but no one has studied that," Garland told UCR Today.

    "If it were possible to take MRIs of babies’ midbrains before these babies started ‘exercising’ and then follow these babies through life, it may be that inherent, genetically-based differences in midbrain size detected soon after birth will influence how much they would be likely to exercise as adults."

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