Dogs are known for their ability to identify and track objects based on their scent. Now it has been revealed that they amplify this talent with special brain structures that link it to their eyesight.
A study released this month in the Journal of Neuroscience revealed that vision and smell are linked in the canine brain, something not yet found in any other species.
“The most interesting thing about this research is the connections from the nose to the occipital lobe, which houses the visual cortex,” said veterinary neurologist Philippa Johnson, associate professor in the College of Veterinary Medicine at Cornell University and senior author of the study.
She and her colleagues examined MRI scans of the brains of 23 dogs, which showed neurological connections between the olfactory bulb, where smell is recognized, and their occipital lobe, where vision is processed.
Humans, who rely primarily on sight, don’t have such connections in their brains, although it’s possible there’s something similar in other animals that rely heavily on smell, Johnson said.
The discovery suggests that smell and sight are somewhat integrated in dogs, although how dogs perceive the interaction of the two senses is unknown.
“Smell contributes to the visual cortex in dogs, but a dog’s experience is difficult for us to discern,” Johnson said. “But I think they can use smells to figure out where things are.”
She explained that when people enter a room, they primarily use their sense of sight to determine who is there or how furniture is positioned. But dogs seem to incorporate smells into how they interpret and navigate their surroundings, she said.
This is corroborated by the behavior of dogs that have lost their sight but do not appear to be greatly affected by the fact that they have gone blind.
“One of the ophthalmologists at the hospital here said he regularly has owners who bring their dogs in and when he tests their vision they’re totally blind – but the owners literally won’t believe him,” she said. “The blind dogs behave quite normally. You can play fetch. They can orient themselves in their surroundings and don’t bump into one another.”
Johnson and her colleagues plan further studies to examine the brains of other animals, such as cats and horses, which are highly dependent on smell.
“A horse’s head is primarily a nasal organ, but they use scent differently than dogs because they are prey animals and use it to warn themselves,” she said. “So it’s going to be interesting to see how their nasal systems integrate with their brains.”
Dogs’ sense of smell is known to be much more sensitive than humans’: the olfactory bulb in a dog’s brain is about 30 times larger than in the human brain. Dogs have up to a billion olfactory receptors in their noses, compared to just 5 million olfactory receptors in humans, Johnson said.
But the discovery suggests that the sense of smell is much more important for dogs than previously thought.
“We already have an indication that their vision is not sharp and as complex as human vision. However, we now know that smells are part of their visual processing, so dogs may have a completely different experience of the world than we do,” she said.
James Serpell, a professor emeritus of ethics and animal welfare at the University of Pennsylvania School of Veterinary Medicine who was not involved in the study, said the finding suggests that dogs somehow incorporate elements of smell and sight into their perception of the world integrate around them.
“This would certainly help explain why dogs going blind seem to function so well, at least when they are in a familiar environment where their sense of smell can map their visual memories of spatial relationships,” he said in an E -Mail.
Paleoanthropologist Pat Shipman, author of “Our Eldest Companions: The History of the First Dogs‘, suggests that dogs’ superior ability to recognize and analyze smells was one of the reasons for their domestication of wolves up to 40,000 years ago – along with their ability to see in the dark, run much faster than humans and to hunt cooperatively.
“The whole benefit of domesticating another predator must have been to give humans something they didn’t otherwise have,” she said.
Such advantages appear to make dogs particularly useful to early humans, who had to rely on hunting for much of their sustenance.
“It has been shown in several different ethnographic studies in several parts of the world that hunters who take a dog outperform hunters without a dog,” Shipman said. “Even if you take into account that the dog eats some of the meat – because he needs to get some of it too – you end up with higher yields.”
Their heightened sense of smell and other advantages may also have made dogs useful in protecting captured prey from other predators like wild wolves, she said.
“The easiest way to get food is to take it from someone else who went to all the trouble to catch it,” she said. “But if you’re there with your dogs — or your wolfhounds or whatever you want to call them — they’ll spot another animal around much sooner.”
https://www.nbcnews.com/science/weird-science/dogs-can-see-noses-study-suggests-rcna39333 According to a study, dogs can “see” with their noses.