Study finds brain searches for the best way to move the body

The study of how the body adapts to new motions sheds fresh information on how the nervous system learns and might serve to guide a wide range of applications, from personalised rehabilitation and sports training to wearable technologies for healthcare. The findings were published in the journal Current Biology this week.

“How does our brain figure out how to best move our body? It turns out that this can be a challenging problem for the nervous system, considering we have hundreds of muscles that can be coordinated hundreds of times per second — with more possible coordination patterns to choose from than moves on a chessboard,” says study senior author and SFU professor Max Donelan, director of SFU’s Locomotion Lab.

“We often experience changes to our body and our environment. Perhaps you enjoy a long run on a Saturday morning — your muscles may fatigue as the length of the run increases. Perhaps you choose to run on the beach on vacation — the sand may be uneven and loose in comparison to the pavement on the sidewalk. While we might register that these changes have occurred, we might not appreciate how our body adapts to these changes.”

Donelan’s team of motor learning neuroscientists cooperated with a Stanford University team of mechanical engineers who construct human-robot systems. They worked together to monitor the walking patterns of research participants wearing exoskeletons.

Findings

The nervous system tackles the difficulty of learning a new movement coordination pattern by first investigating and assessing numerous possible coordination patterns, according to the researchers. This investigation was measured as a general increase in variability throughout the entire movement, joint, and muscle levels.

With practise, the neural system adjusts to certain characteristics of movement while decreasing variability along these features. The researchers also discovered that these adaptive adjustments enhanced overall locomotion, lowering the energy cost of walking by around 25%.

“We created new contexts using exoskeletons that act to assist walking, and then studied how people explore new movements and learn more optimal ones,” says Sabrina Abram, the study lead author and former graduate student in the Locomotion Lab. Participants experienced walking in this context over six days, resulting in about 30 hours of lab time for each and an extraordinary amount of data collected by co-author Katherine Poggensee.

While the nervous system appears to benefit from first searching among many different coordination patterns, it also benefits from reducing this search space over time, Abram adds. “This is because continuing to search among coordination patterns that already reduce energy can in turn increase energy, as well as add to the already challenging problem of figuring out the best way to move.”

Source: Simon Fraser University