his silence speaks volumes
his silence speaks volumes
Why didn’t the hound of the Baskervilles bark? Sir Arthur Conan Doyle (in the guise of Sherlock Homes) deduced that the hound recognized the killer -case solved. But wait: the hound recognized many people, and surely he would bark at some of them; why then not bark at the owner? What was going on in his brain to make this discrimination? Was it fear of an abusive owner? Or may be expectation of reward for good behavior? The novel doesn’t tell us, because both Holmes and the much- maligned Dr. Watson couldn’t know. In fact, psychologists, dog behaviorists, and anthropologists weaved theories galore, but definitive data have been are hard to come by.
A major theory about dog/man relationship posits that dogs ingratiated themselves with early humans between 9,000 and 30,000 years B.C.E because they acquired the capacity to understand and communicate with humans. Research revealed a surprising range variability of cognitive skills that dogs can learn: following pointing and gaze cues (think it’s trivial? try to teach this to a cat, or a laboratory mouse), fast mapping of novel words (heel, come here, pick up the newspaper), and the conjecture that dogs have emotions (the dog is smiling, the dog looks at you adoringly, which makes you feel good). But when all is said and done, we don’t know what’s really going on in the dog’s brain. That is, until now.
Canine fMRI?
Easier said than done. Have you ever try to keep a dog motionless long enough for an fMRI study? The only way to do it, it was thought, was either to anesthetize or restrain them -neither way suitable for getting a true picture of brain activity. Gregory S. Burns of Emory University in Atlanta and his colleagues, obviously dog owners, knew how to keep pooch quiet. In a paper in PLoS ONE they describe how the did it. They constructed MRI simulators to gradually acclimate Callie, a 2 year-old feist of indeterminate pedigree, and McKenzie, a 3 year-old border collie who was already well-trained in agility competition. The owner-scientists, under the supervision of a professional trainer, gradually habituated the dogs to sitting quietly in the machine and tolerate its noise for 30 seconds. Head movement was less than 1mm; remarkable! I don’t think many humans can do that. The study was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. All procedures were approved by the Institutional Animal Care and Use Committee of Emory University.
Initial results
A hand signal was given that indicated the presence or absence of a food reward that would be received. The left hand up indicated a hot dog reward, while both hands pointing toward each other horizontally indicated no reward.
The results were not surprising: just like in other mammals, the ventral striatum, which secretes dopamine, is the locus of the reward system in dogs.
the yellow-orange indicates the locus of the ventral striatum, where the reward system resides
This is not the end of the story, it is the beginning. This is the first demonstration of either MRI or fMRI in completely awake, unrestrained dogs. It paved the way to investigating a wide variety of dog cognition traits. Why should we care about it, in the first place? Here is the authors’ reply:
“Dogs have had a prolonged evolution with humans, and they are uniquely attuned to our behaviors. For example, one might reasonably ask to what extent the dog mentalizes the minds of humans. Dogs are intensely visual and pay attention to our facial expressions and where we look and point. How do they represent these actions? How do dogs distinguish humans, and is it by vision or smell? Is human language processed as arbitrary sounds, or do dogs have neural structures that respond in a deeper manner to language? What is the difference between how dogs represent humans and other dogs or animals? The questions are endless. And while the study of the canine mind is fascinating for its own sake, it also provides a unique mirror into the human mind. Because humans, in effect, created dogs through domestication, the canine mind reflects back to us how we see ourselves through the eyes, ears, and noses of another species”.
And maybe one day we’ll also be able to really tell why the hound of the Baskervilles didn’t bark.