How a Recent Study Reveals What a Dog’s Nose Knows

For dogs, scent is a primary way of making sense of the world, much as humans depend on vision. We still understand relatively little about the way dogs interpret smells, but a recent study may bring us nearer to knowing what a dog’s nose truly understands.

Dogs are naturally equipped for smell detection. An average dog’s nose contains more than 10 million scent receptors, whereas humans possess only around 6 million.

As a result, a canine nose can detect scents more than 10,000 times better than ours. Dogs can identify extremely small amounts of an odour: forensic detection dogs, for instance, can detect 0.01 microlitres of petrol. One microlitre is one millionth of a litre.

People have put dogs’ remarkable olfactory abilities to use in many settings, undoubtedly helping to forge the close bond developed with our canine companions during 40,000 years of living alongside them.

They continue to work with us as hunting partners, using scent to locate food. Dogs also serve as essential members of crime-fighting teams by finding illicit substances; as medical colleagues detecting disease; and in conservation work, locating rare and endangered species.

Yet, despite dogs’ extensive role as natural scent detectors, we remain largely unaware of how they make sense of what they smell or perceive the world they inhabit.

Studying how dogs detect scent

Investigating dogs’ brain activity while they encounter particular smells can reveal which brain regions are linked with scent detection. This may help scientists establish what a dog is experiencing and could improve the selection and training of sniffer dogs.

Previously, studying canine brains required costly equipment and research techniques that depended on dogs remaining still. Consequently, we know less about the brains of active working dogs, which may find it difficult to stay motionless for extended periods.

Nor can data from dogs able to sit still simply be applied to all dogs, as breeds differ in both their training and scenting abilities.

Sensing scents

The recent study mentioned at the start of this article used a new, inexpensive and non-invasive approach to investigate how the canine brain responds to scent. The researchers believe the technique - called AI speckle pattern analysis - could support future research into how dogs’ brains react to smells, and what this reveals about the way they perceive and respond to their surroundings.

The team designed an optical sensor to focus on three brain regions involved in canine scent discrimination: the amygdala, olfactory bulb and hippocampus. The amygdala governs emotional reactions to stimuli.

The olfactory bulb processes odours, while the hippocampus is linked to the formation of memories.

The study equipment comprised a high-resolution digital camera connected to a computer and a green laser. Laser light, which can pass through dog fur and skull bone, was directed at the heads of four relaxed, blindfolded study dogs exposed to four distinct scents: alcohol, marijuana, menthol and garlic. Each of these substances appears to trigger similar olfactory responses in dogs.

As the laser light reflected off the three brain regions, the camera registered interference in the form of a distinctive "speckle" pattern. It recorded for five seconds, with this repeated four times for every scent.

AI examined variations in speckle patterns across the brain regions to build models showing how the dogs’ brains responded to each smell.

Dogs’ emotional responses to scent

The findings emphasised the amygdala’s role in canine scent discrimination. This indicates that dogs may have an emotional element to the way they sense their environment. In humans, taste and odour detection are also understood to be connected with memory formation and emotional state.

Since dogs seem to respond emotionally to scents, this may need to be considered in training methods and experiences. Dogs, for example, often associate the recognisable smell of the veterinary surgery with situations that are less than enjoyable.

Dogs being trained for scent detection would probably also benefit from being in a positive emotional state when introduced to training odours.

From scent detection to wearable technology

This work may even open the way for specialised equipment that detects and translates dogs’ olfactory responses. Fast-working mobile devices could enable us to interpret, in real time, what a dog’s nose is telling it.

That possibility is not as far-fetched as it sounds. Anyone who has seen the Disney film Up may recall Dug, the dog with a collar that translated his barks. Scientists have, in fact, created a real collar claimed to explain what a dog’s vocalisations mean.

It is hard to judge its accuracy without examining the data used to train the collar’s AI, although its database expands as more dogs wear the collars. Should the collars prove accurate, wearable technology may soon be able to tell us precisely what our dogs are saying and smelling.

Jacqueline Boyd, Senior Lecturer in Animal Science, Nottingham Trent University

This article is republished from The Conversation under a Creative Commons licence. Read the original article.