Which breed of dog has the largest brain?

We have changed the brain structure of our four-legged hunting companions

"We have not only changed the appearance of our four-legged hunting companions, but also the structure of their brains."

Humans have bred dogs for a variety of purposes. So also for the hunt. And even for the hunt there are different specialists, such as the pointing dog or the bloodhound.
A recently published study by Hecht et al. (2019) from Harvard University examined 62 purebred dogs of 33 different breeds using MRI scans, among other things. Dogs have not been researched in this way before, which is why this study is a really impressive piece of work, according to psychologist Daniel Horschler of the University of Arizona.

Breeding a certain breed of dog pursues the intention to develop a certain characteristic that fulfills a certain purpose. For example, a bloodhound with its fine nose should have different character traits than a poke dog or a police service dog. It is already known that different breeds have different perceptions, temperaments, and behaviors, but the neural origins of these changes were previously unknown. Hecht and colleagues found out that the behaviors and character traits they bred are reflected in the structure of the brain. These changes have now been made visible for the first time by MRI scans. To do this, the researchers examined the brain regions that had the greatest variance within the races. They found six neural networks within the brain, which were larger or smaller depending on the race and which have changed along with the race. Hecht and colleagues suspect that these networks work together differently in different behaviors.

Therefore, the team looked at the traits the dogs were bred for (e.g. Beagle - fine nose, Border Collie - keeping flocks of sheep together) and examined the relationship with the six identified networks in the dogs' brains. Each of the six networks in the dog's brain correlates with at least one characteristic. They could prove that z. B. Dobermans and Boxers, which are sometimes used as police service dogs, showed significant differences compared to other breeds on the net, which is related to sight and smell. Dog breeds bred for dog fighting have shown significant changes in the web that is associated with anxiety and stress.

Hecht and colleagues were particularly interested in the differences between dogs that hunt for smell and dogs that hunt by sight. Dogs who specialize in scent hunting showed no differences in the areas of the brain that recognize scents, but instead in more complex areas that help the dog understand and communicate the information. From Hecht's point of view, this makes sense, because it is common knowledge that you don't have to teach a dog that is known for a fine nose to smell, but to communicate the smell to the handler, e.g. B. - I have found a track - indicate by track volume or track volume.

The dogs in the study were not active service, sport or hunting dogs, but merely domestic dogs. It is amazing that these differences become visible in the brains, even though these dogs have never actively pursued the activities for which they were bred, says Hecht.

Research shows that humans have significantly changed the brain structures of different breeds of dogs. Neuroanatomical variations are not simply influenced by brain size, body size or head shape, but by special networks within the brain regions. The anatomy of the brain therefore depends significantly on cultivated behavioral specializations, such as B. the guard instinct or the hunting instinct. Regarding the implications of the study, Hecht says that the fact that we change the species around us through breeding and that this even has an impact on their brain structures should make us aware of our responsibility towards living things.

Source: Erin E. Hecht, Jeroen B. Smaers, William D. Dunn, Marc Kent, Todd M. Preuss and David A. Gutman (2019): Significant Neuroanatomical Variation Among Domestic Dog Breeds, Journal of Neurosciences (39), pp. 7748-7758.