ITHACA, N.Y. - Scientists studying the neurology of tame foxes identified changes in a part of the brain that has previously been associated with aggression, according to a new paper that compared the brains of domesticated, aggressive and wild foxes.
According to Cornell University researchers, the changes occurred in an area at the base of the brain called the ventromedial hypothalamus, which is known to drive aggression, control decisions related to energy use and is important for maternal instincts and social behaviors in mice.
The study , published Nov. 2 in the journal Current Biology, takes advantage of a classic experiment that started in Siberia in the late 1950s in which Russian geneticists noticed some foxes on silver fox farms were friendlier toward human caretakers while others were more aggressive.
They then selectively bred friendlier foxes with each other and after only six generations of this selection, they had litters of puppies that interacted with humans. The cuddlier foxes also had physical features characteristic of animal domestication, including floppy ears and shorter snouts.
"We wanted to understand, what are the neurological underpinnings of these changes in behaviors that occurred very rapidly with this selection," said Eirene Markenscoff-Papadimitriou , assistant professor of molecular biology and genetics and the paper's senior author.
The research has implications for how environmental pressures of all kinds can alter brain structure on short timescales, Markenscoff-Papadimitriou said.
Previously, other scientists had employed a technique called optogenetics in experiments with mice where light was used to activate specific neurons that express a receptor protein called estrogen receptor alpha in the ventromedial hypothalamus.
"If you activate them, the mouse will immediately attack another mouse," Markenscoff-Papadimitriou said. "We hypothesized that there would be differences in the abundance of this particular cell type, and we did find that the tame fox hypothalamus had fewer of these estrogen receptor-expressing neurons, which are known to be part of the aggression circuit," she said.
Now that the paper's authors observed this difference, next steps will involve trying to understand why domestication leads to these changes in the ventromedial hypothalamus, a brain area that has not been well studied before this work.
