Washington: Athleticism may be linked to brain size, according to a new study which found that exercise-loving mice have larger midbrains.
Researchers at the University of California, Riverside performed laboratory experiments on house mice and found that mice that have been bred for dozens of generations to be more exercise-loving have larger midbrains than those that have not been selectively bred this way.
Researcher Theodore Garland's lab measured the brain mass of these uniquely athletic house mice, bred for high voluntary wheel-running, and analysed their high-resolution brain images.
The researchers found that the volume of the midbrain - a small region of the brain that relays information for the visual, auditory, and motor systems - in the bred-for-athleticism mice was nearly 13 per cent larger than the midbrain volume in the control or "regular" mice.
"To our knowledge, this is the first example in which selection for a particular mammalian behaviour - high oluntary wheel running in house mice in our set of experiments - has been shown to result in a change in size of a specific brain region," said Garland.
In Garland's lab, selection for high voluntary wheel running in lab house mice has been ongoing for nearly 20 years — or more than 65 generations of house mice.
To analyse brain mass and volume on independent samples of house mice, the researchers dissected the brains into two different regions, the cerebellum, a region of the brain crucial for controlling movement, and the non-cerebellar areas. They then weighed these sections separately.
The researchers found that compared to regular mice, those mice that had been selectively bred for high voluntary wheel-running had significantly greater midbrain volume as well as larger non-cerebellar brain mass, but not larger cerebella or total brain mass.
"Our finding that mice bred for high levels of voluntary exercise have an enlarged non-cerebellar brain mass and an enlarged midbrain, but do not show a statistically significant increase in overall brain mass or volume supports the mosaic theory of brain evolution," Garland said in a statement.
"It is possible that individual differences in the ropensity or ability for exercise in humans are associated with individual differences in the size of the midbrain, but no one has studied that," Garland said.
"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," Garland added.
The study was published in the Journal of Experimental Biology.