Erin E. Hecht, Jeroen B. Smaers, William J. Dunn, Marc Kent, Todd M. Preuss and David A. Gutman, Significant neuroanatomical variation among domestic dog breeds, Journal of Neuroscience 2 September 2019, 0303-19; DOI: https://doi.org/10.1523/JNEUROSCI.0303-19.2019.
Abstract
Humans have bred different lineages of domestic dogs for different tasks, like hunting, herding, guarding, or companionship. These behavioral differences must be the result of underlying neural differences, but surprisingly, this topic has gone largely unexplored. The current study examined whether and how selective breeding by humans has altered the gross organization of the brain in dogs. We assessed regional volumetric variation in MRI studies of 62 male and female dogs of 33 breeds. Notably, neuroanatomical variation is plainly visible across breeds. This variation is distributed non-randomly across the brain. A whole-brain, data-driven independent components analysis established that specific regional sub-networks covary significantly with each other. Variation in these networks is not simply the result of variation in total brain size, total body size, or skull shape. Furthermore, the anatomy of these networks correlates significantly with different behavioral specialization(s) such as sight hunting, scent hunting, guarding, and companionship. Importantly, a phylogenetic analysis revealed that most change has occurred in the terminal branches of the dog phylogenetic tree, indicating strong, recent selection in individual breeds. Together, these results establish that brain anatomy varies significantly in dogs, likely due to human-applied selection for behavior.
Significance statement:
Dog breeds are known to vary in cognition, temperament, and behavior, but the neural origins of this variation are unknown. In an MRI-based analysis, we found that brain anatomy covaries significantly with behavioral specializations like sight hunting, scent hunting, guarding, and companionship. Neuroanatomical variation is not simply driven by brain size, body size, or skull shape, and is focused in specific networks of regions. Nearly all of the identified variation occurs in the terminal branches of the dog phylogenetic tree, indicating strong, recent selection in individual breeds. These results indicate that through selective breeding, humans have significantly altered the brains of different lineages of domestic dogs in different ways.
Reminds me of Darwin's finches.
There were some surprises. For example, skill in hunting by scent was not associated with the anatomy of the olfactory bulb. “Rather, this skill was linked to higher-order regions that are involved in more complex aspects of scent processing,” she said. “It’s not about having a brain that can detect if the scent is there. It’s about having the neural machinery to decide what to do with that information.” [...]
“Border collies are amazing at herding, but they aren’t born knowing how to herd. They have to be exposed to sheep; there is some training involved. Learning plays a crucial role, but there’s clearly something about herding that’s already in their brains when they are born. 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,” she said.
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