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The Way To Dogs’ Brain Is Through Their Noses
Scent Stimulation
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The Way To Dogs’ Brain Is Through Their Noses

It’s a beautiful summer day. You and your dog are walking near a patch of grass when she stops dead, then sniffs … and sniffs … and sniffs. Gently, you tug on the leash, but—muzzle buried in the turf—she braces herself and continues her nosework.

Scent is extremely important to dogs, much more so than to humans. All dogs have smart noses. In fact, MRI studies show that when a dog recognizes the smell of a familiar human, the caudate nucleus in her brain lights up, signaling a happy event.

For the average dog, a small pile of foliage contains a world of information. Though the canine brain is about one-tenth the size of a human brain, its smell center is 40 times larger. We have roughly 5 to 6 million scent receptors, a fraction of the 125 to 300 million available to our canine companions.

Dog’s moist noses are cute, but there’s function behind that soft form. The mucus on a dog’s nose helps capture scent particles; when a dog’s nose is dry, she may lick it to improve reception. Dogs can also wiggle their nostrils independently, thereby detecting the direction of odors. Some, like the Bloodhound, use their ears to direct even more potential scent particles up to their noses.

Despite the fact that the olfactory system is an ancient neurological pathway, we still do not completely understand how it works, either in ourselves or in our dogs. New studies are under way, however; in September 2015, the National Science Foundation (NSF) awarded three interdisciplinary teams of scientists $15 million to “crack the olfactory code” as part of President Obama’s BRAIN initiative. As the NSF web page notes, “Olfaction is critical for the survival of species across the animal kingdom. Yet how the brain processes and identifies odors—and how this information influences behavior— remains, largely, an enigma.”

Though we may not understand it, most of us are aware that scent can influence behavior. In the realm of human holistic treatments, the use of essential oils and herbal fragrances has become increasingly trendy, and yoga teachers will sometimes use aromatic oils during classes.

Exposure to certain herbal or spice scents has been shown to have positive effects on humans. For example, Mark Moss and Lorraine Oliver, working at the Brain Performance and Nutrition Research Centre at Northumbria University in the UK, designed an experiment to investigate the pharmacology of 1,8-cineole, one of the main components of rosemary.

After exposing 20 human subjects to varying levels of 1,8-cineole, the investigators tested their cognitive performance. Speed and accuracy test results showed that the concentration of 1,8-cineole in the blood was related to an individual’s cognitive performance: higher concentrations resulted in increased speed and accuracy. If scent can have positive effects on olfactorychallenged humans, it might be expected to have an even more pronounced effect on dogs.

While research on canines is limited, a study done at the University of Belfast explored the influence of four types of olfactory stimulation (lavender, chamomile, rosemary and peppermint) on the behavior of 55 dogs housed in a rescue shelter. The control condition used no odors other than those arising naturally from the dogs’ environment (e.g., odors from disinfectants and other animals). Using diffusions of essential oils and allowing two days between stimulants, the dogs were exposed to the scents four hours a day for five days.

According to the study, dogs exposed to lavender and chamomile spent more time resting and less time moving than with other olfactory stimuli used in the experiment. These odorants also were found to reduce barking and vocalization in caged animals. On the other hand, fragrances such as rosemary and peppermint were found to encourage significantly more standing, moving and vocalizing.

Shelters are safe but sterile environments, and, recognizing that as an issue, some have looked for ways to enrich those environments for their animals; an increasing number are introducing scent. For example, on its web page, the Humane Society of Miami describes its scent enrichment program, which incorporates essential oils such as lavender, Valor (a blend) and vanilla as well as herbs and spices.

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Sheldon Siporin is an adjunct associate professor in the psychology department at Pace University in New York City and has volunteered in several Manhattan animal shelters.

Dog Walk by Holly Meade courtesy of shebeargallery.com

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