Jean-Benoit Legault, The Canadian Press
MONTREAL — The legendary ability of cats to land on their paws might one day help humans walk better following a spinal cord injury, suggests research carried out at the University of Sherbrooke.
The knowledge generated by Professor Alain Frigon and his colleagues might also help seniors whose sense of balance is more precarious.
“During evolution, humans have decided to adopt the most unstable walking position possible,” said Mr. Frigon, from the department of pharmacology-physiology at the University of Estrie.
Even though humans “have balance control that is much more sensitive, much greater” than quadrupeds, he goes on to explain how studying four-legged animals might one day help the bipeds we are, “the circuitry as such” remains the same.
“It’s just that there are additional mechanisms” in humans, said Frigon, whose lab is interested in gait control and the basics of gait recovery following injuries. of the spinal cord, among other things by trying to unlock the secrets of the central nervous system.
The researchers were more specifically interested in somatosensory feedback, namely receptors in the skin, in the muscles or in the joints that send information to the central nervous system, therefore to the spinal cord and the brain.
Mice, because they are so stocky, are less likely to lose their balance if this feedback is lacking. The same is not true for cats or humans.
So when you want to generate results that are potentially applicable to humans, Frigon said, you have to eventually “work with bigger models that have more like control, a high center of gravity, musculature that looks alike,” d especially since the organization of the spinal cord of mice does not resemble that of humans at all.
In collaboration with researchers from the American universities Georgia Tech and Drexel, Mr. Frigon wanted to better understand how this somatosensory feedback allows the cat to coordinate the movement of its four legs.
It specifically stimulated ― in cats trained to walk at human speed on a treadmill ― the superficial peroneal nerve to simulate a stumble (the equivalent, for a hiker, of hitting a rock or a root with the toe of the boot) to examine how the cat was recovering.
The stumbling sensation, researchers detail in the medical journal eNeuro, triggers reflexes that ensure the other three legs stay in contact with the ground, preventing the animal from falling while the fourth leg flies over the obstacle.
“It’s really a coordinated response across all four limbs,” Frigon said. These are responses that will also be described in humans, and it will allow us to see how these adjustments are made following different types of spinal cord lesions.
Such spinal cord injuries, he continues, frequently present with balance and coordination problems; their gait is often ‘non-functional’, and even those who have recovered very well may be unable to avoid an obstacle or have difficulty turning.
The reflex that prevents us from falling when we stumble occurs extremely quickly. But as we age, nerve signals travel more slowly, muscle responses are slower to come, and the risk of falling increases in seniors who are unable to adjust quickly.
“It’s the same thing with spinal cord injuries, but there is also a loss of coordination, explained Mr. Frigon. It’s not that the responses are slower, because many people with spinal cord injuries are young, it’s that the interactions with the central nervous system (…) are not done in the same way.
Such work might one day lead, for example, to the development of electrical stimulation of the spinal cord to facilitate somatosensory feedback, and therefore walking.
“By providing better understandings of how the system works, we’ll be able to develop more targeted strategies and maybe even completely new strategies to promote recovery from gait, but more importantly from functional gait, not just to be able to put one foot in front of the other, but to be able to respond to disturbances, to avoid obstacles… to go hiking”, concluded Mr. Frigon.
