Have you ever wondered what your dog is thinking? As a neurologist, I'm well aware that a dog's brain is quite different from my human brain. The distinctions became even clearer to me when I viewed a brain imaging study of our Bernese Mountain dog to gauge the extent of her nasopharyngeal carcinoma. Her brain was small, had fewer folds, and almost no frontal lobes compared with my brain. There was a huge olfactory apparatus — 10 percent of her brain volume — which should come as no surprise to any dog owner who is reminded daily that smell is very important to a dog.
Having owned dogs for several decades, I've also become aware of their personalities, expressions, and even their ability to intuit my mood. I fully recognize that there is a tendency to project our own thoughts and feelings onto animals — to anthropomorphize — yet it's hard for me to fully accept a behaviorist's view that our dogs' actions are solely a result of conditioning and that they can't, to at least some extent, think.
Fortunately, Gregory Berns, a neurobiologist who has studied human reward systems for a decade using functional brain MRI (fMRI), has pondered this issue as well and has designed experiments to find out what his dog might be thinking. In How Dogs Love Us, Berns describes training his dog to lie motionless in a noisy MRI so that he can record fMRI sequences that demonstrate what parts of his dog's brain respond to varying stimuli. Having seen a photograph of a dog wearing oxygen while strapped to the chest of a soldier parachuting out of an airplane at 30,000 feet, Berns was convinced that if a dog could accomplish that feat, he could train his dog to lie still. Fortunately, all of his laboratory team also owned dogs and were dog lovers so they were as enthusiastic as he was to undertake the “Dog Project.”
The book, written for a general audience, includes pictures of Callie — a 19-pound black and white terrier mix Berns obtained from an animal shelter — while in training, and offers insights on the impact the consuming experimental approach has on his family. Berns' training of Callie mirrored the classical conditioning experiments of the Russian physiologist Ivan Pavlov. For the most part he used a positive training method, rewarding Callie with small pieces of a hot dog whenever his dog responded as required.
There were a myriad of obstacles to overcome in training the dog. First, Berns built a simulator of the MRI in his home. To create the confined space of the MRI's bore he adapted a mold that is used in construction to form concrete pillars. He had to train Callie to be comfortable in this confined space with the dog's head in a bird-cage-like coil, snout resting on a chin rest, and wearing earmuffs to dampen the 100dB sound of the MRI scanner. Berns even recorded the actual MRI sounds during a scan and played them on a sound system he installed in his home simulator.
Including clear descriptions of brain anatomy and how to measure activity in the brain with fMRI, Berns describes well the many pitfalls he overcame during the months he spent training Callie to lie motionless in a very noisy and confined space while still focusing on his hand signals in hope of receiving a morsel of hot dog. When Callie refused to enter the simulated coil, Berns overcame Callie's fear with peanut butter on his nose as he reclined in the coil. When foam proved too soft as a chin rest and allowed motion, Berns cut up strips of boogie board he bought off-season on sale in a sporting goods store.
Those of us who have conducted clinical trials will readily identify with the many regulatory hurdles that Berns had to overcome before he was allowed to scan Callie in an MRI suite normally used for human studies. He needed to assure his Institutional Animal Care and Use Committee that the experiments did not include animal cruelty. At the same time, he had to convince hospital risk managers and the Occupational Safety and Health Administration that humans working in the MRI suite were not at risk of rabies. He also had to answer to lawyers who expressed concern over liability if a dog became aggressive. Beyond those obstacles, he had to find a brain similar to the size of a dog's head so the MRI technologists could undertake preliminary simulations before bringing a dog into the scanner. He solved that problem by using a lamb's head that he purchased in a Middle Eastern supermarket.
Neurologists will be particularly interested in the regions of the dog's brain that showed increased signal following a hand command that the dog anticipated would or would not lead to a hot dog reward. Since Berns had studied how the caudate plays a key role in the anticipation of things humans enjoy, he initially focused on that region in his dog experiments. To obtain meaningful data, he calculated that the dog would have to lie motionless between 10 to 20 seconds after his hand signal before he provided the reward. This delay would allow the fMRI time needed for a hemodynamic response function, blood vessels dilating surrounding activated neurons. His initial strategy for a control was to use a pea held in the opposite hand as a less desirable reward. That design turned out not to work since the dog perseverated on presentation from one side, regardless if he held up the fragment of a hot dog or a pea. Undaunted, he changed the design to variable reinforcement using only the bits of hot dog.
The experiments demonstrated selective caudate activation in both Callie as well as in a second dog. The researchers also found activation in motor areas of the dogs. Although speculative, Berns suggests that the motor area activation may be firing mirror neurons in the dogs. Berns is quick to point out that he cannot infer that activity in a particular part of the brain is evidence for a particular emotion or cognitive function. This same type of reverse inference has been questioned by reviewers of the plethora of human fMRI studies that have been undertaken in the last decade to evaluate regional brain responses to specific stimuli.
Berns' research team is also exploring the location of a dog's reaction to familial versus strange human and animal scents. Although the studies are preliminary, they do demonstrate proof of concept: an awake animal can be trained to remain motionless long enough to capture brain fMRI localization patterns.
Will this research help us to better understand human behavior? Berns would argue yes. He refers readers to The Expression of the Emotions in Man and Animals, a less well-known book by Charles Darwin, which argued that if we understand the emotional systems of animals, it will help us to better comprehend the origins of human feelings.
How Dogs Love Us offers a personal view into the investigative mind of this gifted neuroscientist and the impact he has on his research collaborators, as well as on his wife and children. He has previously published a book titled Iconoclast, in which he reveals barriers a scientist has to overcome to think outside the box. Readers will enjoy thinking outside the box along with Berns and will learn a lot at the same time.
Dr. Ringel, Neurology Today's editor-in-chief, is professor and director of the Neuromuscular Division of the University of Colorado School of Medicine in Aurora, CO.