Journal Scan: The brains behind the breeds

2019-11-21
Sarah Mouton Dowdy

A recent study suggests that selective breeding has significantly altered the anatomy of dogs brains.

Bianca/stock.adobe.comWhy they did it

Humans have been breeding dogs for thousands of years, but it wasn't until recently that someone thought to ask if human preferences for certain canine traits have affected brain anatomy.

That someone is Erin Hecht, PhD, an assistant professor of neuroscience from Harvard University. She found inspiration as a graduate student at Emory University while watching a nature program about domestic dogs and selectively bred Russian foxes. According to an interview with The Harvard Gazette, Hecht was surprised to learn that the scientists were only concerned with genetics and evolution-not neuroscience. “I thought, ‘How is this possible? No one's thought about looking at their brains,” she told the Gazette.

What they did

Eager to fill in the gap, Hecht reached out to Marc Kent, DVM, DACVIM, a professor of small animal neurology at the University of Georgia College of Veterinary Medicine, who gave her access to magnetic resonance imaging (MRI) scans from dozens of his canine patients.

“The first question we wanted to ask was, are the brains of different breeds of dogs different?” Hecht said in an interview with The Washington Post. And after analyzing the MRIs of 62 dogs representing 33 breeds, she and her colleagues found that their brains are indeed different, that the differences aren't randomly distributed and that the differences aren't caused by variations in brain size, body size or skull shape.

What they found

The researchers discovered that neuroanatomic variation is focused in specific networks of the brain that significantly correlate with behavioral specializations like sight hunting, scent hunting, guarding and companionship. They also note that most of the variation was observed in the terminal branches of the phylogenetic tree, which indicates strong, recent selection in individual breeds. “Together,” the researchers conclude in the abstract, “these results establish that brain anatomy varies significantly in dogs, likely due to human-applied selection for behavior.”

Study limitations

In a Washington Post interview, Jeffrey Stevens, PhD, director of the University of Nebraska's Canine Cognition and Human Interaction Lab, discussed some of the study's limitations. For starters, he explained that not everyone is convinced of the usefulness of mapping behaviors to breeds because individuals within the same breed can vary a lot. Stevens also noted that the dogs weren't performing breed-specific tasks at the time of their MRI scans, calling into question whether any big conclusions linking breed and behavior can be drawn.

Further potential limitations stem from the fact that all of the research participants were house pets, not working dogs that regularly put their breed-specific talents to serious use. This fact is important because, as Dr. Hecht explained to The Washington Post, studies have shown that the brain changes as it learns a new language or motor skill. In other words, the brain anatomy of an old English sheepdog who spends his days herding sheep in the New Zealand countryside could look very different from that of an old English sheepdog who lives the life of a pampered Instagram darling in a Chicago apartment (lending further support to Stevens' first concern). With this in mind, Stevens suggested that a future focus on working dogs could reveal even stronger correlations.

Future research

Speaking of the future, Hecht, whose lab also studies brain evolution in humans, told The Harvard Gazette that further research on dog brains could provide insight into the brains of their masters-an idea that wasn't taken very seriously by other scientists and funding agencies when Hecht first began her research back in 2012. Using border collies as an example (perhaps because she has two of her own), she explained that while they're remarkable herders, they aren't born knowing how to herd.

“Learning plays a crucial role, but there's clearly something about herding that's already in their brains when they are born,” she said. “It's not innate behavior, it's a predisposition to learn that behavior. That's analogous to what goes on with humans with language. They don't pop out of the womb being able to speak, but clearly all humans are predisposed in a very significant way to learn language. If we can figure out how evolution got those skills into dog brains, it might help us understand how humans evolved the skills that separate us from other animals.”

Hecht is now specifically studying working dogs-both champions and their less successful littermates-in an attempt to better understand how dog brain anatomy has been shaped by recent evolution. “We're looking for animals raised in the same environment where, for whatever reason, one has excelled and one dropped out,” she told the Gazette.

Dr. Hecht's study was published in The Journal of Neuroscience. To read the abstract, click here.

Reference

1. Hecht EE, Smaers JB, Dunn WD, et al. Significant neuroanatomical variation among domestic dog breeds. J Neurosci 2019;39(39):7748-7758.

Sarah Mouton Dowdy, a former associate content specialist for dvm360.com, is a freelance writer and editor in Kansas City, Missouri.