By Tom
Metcalfe
Dogs are famous for their ability to identify and track objects by their scent.
It has now been revealed that they enhance this talent with special brain structures that
link smell to the way they see.
A study published this month in the Journal of Neuroscience reveals that vision and sense of smell are connected in the dog brain, something that has not yet been found in any other species.
"What's most exciting about this research is the connections from the nose to the occipital lobe, which houses the visual cortex," says veterinary neurologist Philippa Johnson, associate professor at Cornell University School of Veterinary Medicine and lead author of the study.
Image of a Golden Retriver dog with a ball.Getty Images
She and her colleagues studied MRIs of the brains of 23 dogs that showed neurological connections between the olfactory bulb, where odors are recognized, and their occipital lobe, where vision is processed.
Humans, which rely primarily on vision, don't have these connections in their brains, though it's possible something similar exists in other animals that rely heavily on scent, Johnson added.
The discovery suggests that smell and vision in dogs are somehow integrated, although it is not known how dogs experience the two senses working together.
"Odor contributes to the visual cortex in dogs, but a dog's experience is hard to know
," Johnson said.
"I think they can use smell to know where things are."
He explained that when humans enter a room, they primarily use their sense of sight to tell who is there or how the furniture is arranged.
However, dogs seem to integrate scent into their interpretation of the environment and their orientation to it.
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This is demonstrated by the behavior of dogs that have lost their sight but do not seem very affected by the fact that they have gone blind.
"One of the ophthalmologists at the hospital here says that the owners regularly bring their dogs and when he tests their eyes they are completely blind, but the owners literally don't believe him," he says.
“Blind dogs act totally normal.
They can play ball.
They can orient themselves in their environment and don't bump into things
. "
Johnson and his colleagues are planning further studies to examine the brains of other animals, such as cats and horses, that rely heavily on smell.
"A horse's head is predominantly a nasal organ, but they use scent differently than dogs, because they are prey animals and use it to alert themselves," he said.
"So it will be interesting to see how their nasal systems integrate with their brain."
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It is known that the sense of smell of dogs is much more sensitive than that of humans: the olfactory bulb of a dog's brain is about 30 times larger than that of a human brain.
Dogs have up to a billion olfactory receptors in their noses, compared to 5 million olfactory receptors in people, Johnson explains.
But the discovery suggests that the sense of smell is much more vital to dogs than previously thought.
“We already have indications that their vision is not as sharp and complex as human vision.
However,
we now know that smell is part of their visual processing,
so dogs could have a completely different experience of the world than we do,” she says.
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James Serpell, an emeritus professor of animal welfare and ethics at the University of Pennsylvania School of Veterinary Medicine, who was not involved in the study, said the finding suggests that dogs somehow combine elements of smell and sight in their perception of world around them.
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"This would help explain why dogs that go blind seem to function so well
, at least when they are in a familiar environment where their sense of smell can be linked to their visual memories of spatial relationships," he said in a report. email.
Paleoanthropologist Pat Shipman, author of
Our Oldest Companions: The Story of the First Dogs,
suspects that dogs' superior ability to detect and analyze odors was one reason they were domesticated from wolves up to 40,000 years ago. along with their abilities to see in the dark, run much faster than humans, and hunt cooperatively.
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"The advantage of taming another predator has to be that the human being gets something that they don't have otherwise," he says.
These advantages appear to have made dogs especially useful to early humans, who relied on hunting for much of their food.
"It has been shown in different ethnographic studies in various parts of the world that hunters who have a dog with them do better than those who don't," Shipman added.
"Even taking into account the fact that the dog is going to eat some of the meat - because he has to get something out of it too - he ends up getting more out of it."
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Their heightened sense of smell and other advantages may also have made dogs useful in protecting captured prey from other predators, such as wild wolves, he said.
"The easiest way to get food is to take it from someone else who has gone out of their way to catch it," he said.
"But if you're out there with your dogs - or your wolfdogs, or whatever you want to call them - then they're going to spot another animal in the area much sooner."
