Proceedings of the University of Sherbrooke | Cats land on their feet, which can help humans walk better

(Montreal) Cats’ legendary ability to land on their paws may one day help people walk better after spinal cord injuries, suggests work at the University of Sherbrooke.

The knowledge gained by Professor Alain Frigon and his colleagues may also help the elderly, whose sense of balance is more precarious.

“During evolution, humans decided to adopt the most unstable walking position possible,” said Mr. Frigon from the Department of Pharmacology-Physiology at Estrie University.

Although humans “have more sensitive, greater balance control” than quadrupeds, he goes on to explain how studying quadrupeds could one day help us bipeds.

Humans simply have additional mechanisms, according to Frigo, whose lab is interested in the fundamentals of gait control and gait recovery after injury. system.

Researchers were more interested in somatosensory feedback, that is, receptors in the skin, muscles, or joints that send information to the central nervous system, and thus to the spinal cord and brain.

Mice, being so plump, are less likely to lose their balance in the absence of this feedback. The same is not true for cats and humans.

According to Frigo, when you want to get results that are potentially applicable to humans, “you have to work with larger models that have more control, a higher center of gravity, similar musculature.” the spinal cord of mice is not at all like that of humans.

Collaborating with researchers at Georgia Tech and Drexel universities in America, Mr. Frigon wanted to better understand how this somatosensory feedback allows the cat to coordinate the movements of its four legs.

He specifically—in cats trained to walk at human speed on a treadmill—stimulated the superficial peroneal nerve to simulate stumbling (the pedestrian equivalent of hitting a rock or root with a toe). the cat was recovering.

As the researchers detail in the medical journal eNeuro, the sensation of stumbling triggers reflexes that keep the other three legs in contact with the ground and prevent the animal from falling as the fourth leg flies over an obstacle.

“It’s really a coordinated response in all four limbs,” Frigon said. These are responses that will also be described in humans, which will allow us to see how these adjustments are made after different types of spinal cord injuries. »

Such people with spinal cord injuries often have problems with balance and coordination; their gait is often “dysfunctional” and even people who have recovered very well will be unable to avoid an obstacle or have difficulty turning.

When we stumble, the reflex that prevents us from falling occurs extremely quickly. However, as we age, nerve signals travel more slowly, muscle responses become slower, and seniors who cannot adapt quickly are at increased risk of falling.

“It’s the same thing with spinal cord injuries, but there’s a loss of coordination,” Mr. Frigon said. It’s not that the responses are slower because most people with spinal cord injuries are young, it’s the interaction with the central nervous system. […] it is not done in the same way. »

Such work may one day, for example, lead to the development of electrical stimulation of the spinal cord to facilitate somatosensory feedback and therefore walking.

“With a better understanding of how the system works, we will be able to develop more targeted strategies and perhaps entirely new strategies to promote recovery from gait, but more importantly from functional gait, which is not just putting one foot in front of the other, but being able to respond to perturbations.” , to avoid obstacles… going for a walk,” Mr. Frigon concluded.

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