Step aside Cesar Millan—these days when you want to know what the dog really saw, ask a scientist not a Dog Whisperer. While studies of domestic dogs (Canis familiaris) have been fundamental to neuroscience—it was Pavlov’s dog after all that drooled when it heard that bell—dog studies are undergoing a renaissance due to advances in genetic and brain-scanning techniques, and dogs are emerging as unique research subjects, due to their evolutionary history, close relationship with humans, high intelligence, and most importantly their ability to sit. (Sit still while their brain is being scanned that is.)
In this blog post I’ll discuss recent research: evolutionary studies comparing dogs to wolves, studies probing whether dogs understand what we say and how their brains process speech, and finally how millennia of selectively breeding dogs is now helping in the search for genetic markers of mental illness and has even lead to the development of a new drug to treat insomnia.
The Origin of Man’s Best Friend
Pop quiz: which animal is more closely related to humans—a mouse or a dog?
It’s unclear how the human’s relationship with dogs began, and what lead dogs to diverge from wolves. For example, did humans actively seek out and domesticate wolves, or did wolves flock to early farms, eating human food scraps, and we were more likely to let the less-aggressive, cuter ones stick around?
We do know that dogs evolved with us. At the time of the agricultural revolution 10,000 years ago, humans and dog genomes both evolved, modifying enzymes to allow for better processing of the carbohydrates found in the grains we cultivated. (If you want to hear more, check out this interview with the study’s author.)
A study published just last week suggests that this change from hunter to scavenger may have also affected dog’s appetite for risk. Although C.M. Coolidge immortalized dogs as gamblers for a series of cigar advertisements, the domestication of dogs may have actually rendered them risk-adverse. Given a choice between receiving a reward of guaranteed but inferior food, or a 50-50 chance at getting either a tastier treat or nothing, 80% of wolves chose the risky option, whereas dogs did so only 58% of the time[1]. The authors of this study argue that these results are constant with other cross-species comparisons that show that species with unstable food sources tend to be risk-takers, possibly because these species need to explore to find food, and because exploration is inherently risky these species tend to be greater risk-takers. Note that the dogs and wolves used in this study all grew up in the same conditions at the Wolf Science Center in Dorfes, Austria, so differences observed are likely to stem from genes not different developmental experiences.
What do dogs understand?
Dogs were the first species that humans domesticated, and as such have acquired the ability to understand and communicate with humans, but how much do they really understand and how do they do it?
Gregory Burns wondered that same question. He was using fMRI to scan brain activity in humans, and he wondered if it could be applied to dogs. fMRI brain scans depend on the research subject staying completely still. We can tell humans to stay still, but the few previous fMRI studies of animals had used anesthesia or immobilization.
Watching a TV program about military dogs, Berns had a hunch. If dogs could be trained to stay calm and jump out of a noisy helicopter, they could also be train to stay still and calm through the loud racket generated by an fMRI machine. By scanning the brains of dogs, we could apply the techniques of modern cognitive science to study how dogs had adapted to understand us and become integrated into our families. His hunch was right. He trained his own dog Callie, to sit inside the fMRI machine and made history, generating the first fMRI scan of an unrestrained thinking dog’s brain—showing how the dog’s brain responded when it saw a hand signal that indicated it would get a reward. Berns outlines the story of his pioneering research and findings in his book, How Dogs Love Us.
Since then, a variety of groups have begun to study dog brain activity, during a variety of tasks using fMRI:
From Thompkins et al., 2016 Early days of dog MRI studies show upward trend.
Just last week, a new study published in Science, Hungarian researcher Attila Andics and his group showed that with dogs, it’s not just ‘what you say’ but ‘what you say, how you say it, and the combination of the two’ (gotta workshop that one).
Inside the scanner, they played the dogs recordings of either praising words, like ‘clever’—actually, they used the Hungarian equivalent ‘ügyes’—or separate words they thought would have no meaning to the dogs like ‘olyan,’ which means ‘such.’ These words were said both in neutral tones and in tones consistent with praise. Dogs showed three distinct patterns of neural activity: a set of responses sensitive to the words themselves, another sensitive to the intonation of words, and a final pattern when the praise words were combined with the congratulatory intonation.
Here, researcher Attila Andics explains his research:
Interestingly consistent with what has been observed in humans, the left hemisphere appeared more involved in the dogs’ processing of words themselves, possibly due to the left hemisphere’s preferential ability to process rapidly changing acoustic signals, as has been observed in humans and gerbils. Also, like humans, the dogs preferentially processed intonation using their right hemisphere. Perhaps most interestingly, only one sound combination activated the dogs’ reward systems, the combination of both praise words and praise intonation, indicating that the dogs may be combining information from these lexical and tonal processing systems to inform their decisions.
From Information is Beautiful – How does your dog stack up?
Dog Breeds and Brain Disease
Selective breeding to generate inbred or ‘purebred’ lines of dogs selected for certain traits, has also lead some breeds to become enriched for genetic disorders. The presence of these afflicted breeds, combined with dog’s high intelligence and complex behavior and now our ability to scan their brains in various behavioral tasks, makes the dog an amazing model organism for discovering and understanding the genetics and mechanisms of brain diseases.
One of modern neuroscience’s greatest success stories has been discovering the cause of narcolepsy. Many Dobermann pinschers suffer from narcolepsy, and Emmanuel Mignot of Stanford University studied these Dobermanns, eventually discovering the gene that made them narcoleptic.
Mignot found a mutation to the dog’s hypocretin receptor 2 (also known as the orexin receptor 2), was found to be the culprit, in 1999. While the exact same mutation does not cause narcolepsy, in humans, this study identified the hypocretin pathway as a key pathway in regulating sleep that was disrupted in narcolepsy. Based on these findings, in 2000, doctors realized that a majority of patients with narcolepsy show undetectable levels of hypocretin in their cerebral spinal fluid, while it was detectable in every control.
These discoveries led to pharmaceutical research into an orexin blocker suvorexant, which the FDA approved it in 2014 as the first in a new class of sleeping pill to help treat insomnia. Throughout history, most drugs that target the brain have been discovered serendipitously, and this is one of the few success stories of a basic science finding informing drug synthesis and clinical trials, and finally resulting in an FDA-approved product.
So far research into dog narcolepsy has only resulted in suvorexant, a drug for human insomnia that blocks the hypocretin receptor, and therefore functionally mimics the insomnia seen in dogs. However, treatments for narcolepsy are being investigated, and may be on the way, for example promising drug that stimulates the hypocretin receptor was reported last year. (But keep in mind only a small percentage of promising drugs make their way through clinical trials, and when they do it still takes years.)
Conclusion
You can learn a lot about a person by meeting their best friend. As we learn more about dogs we’ll learn more about ourselves—our history, our language, and our idiosyncrasies. In addition to being loving and devoted pets and disciplined service animals, dogs can act as valuable research subjects. I think research can be ethically and thoughtfully performed on dogs, the way it is ethically and thoughtfully perfomed on humans, and I hope dogs’ contribution to science, will further elevate our respect for them and treatment of them–I mean, when’s the last time a cat contributed to science? (Actually there’s an interesting story about that, but I’ll leave it for another day.)
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[1] Authors did earlier tests to calibrate the tasty food given, to ensure that wolves and dogs showed equal preference for the food and they were only measuring preference for risk.
