Spontaneous baby movements are important for the development of a coordinated sensorimotor system

According to new research led by the University of Tokyo, spontaneous, random baby movements help develop their sensorimotor systems. Detailed motion capture of newborns and infants was combined with a musculoskeletal computer model that enabled researchers to analyze the communication between muscles and sensations throughout the body.

Researchers found patterns of muscle interaction based on children’s random exploratory behavior that later enabled them to perform sequential movements as infants. A better understanding of how our sensorimotor system develops can help us gain insight into the origins of human movement as well as earlier diagnosis of developmental disorders.

From birth—and even in the womb—babies begin kicking, heeling, and moving without a goal or external stimulation. These are called “spontaneous movements” and researchers believe that they play an important role in the development of the sensorimotor system, that is, the ability to control muscles, movement and coordination. If researchers can better understand these seemingly random movements and how they are involved in early human development, we may even be able to identify early indicators for some developmental disorders, such as cerebral palsy.

Currently, there is limited knowledge about how newborns and infants learn to move. “Previous research on sensorimotor development has focused on kinematic properties, the muscle movements that cause movement at a joint or part of the body,” said Hoshinori Kanazawa, a project assistant professor in the Graduate School of Information Science and Technology.

“However, our study focused on muscle activity and sensory input signals for the whole body. By combining a musculoskeletal model and a neuroscientific method, we discovered that spontaneous movements, which seem to have no clear function or purpose, contribute to coordinated sensorimotor development. “

First, the team recorded the joint movements of 12 healthy newborns (less than 10 days old) and 10 young infants (about three months old) using motion capture technology. Next, they estimated the children’s muscle activity and sensory input signals with the help of a whole-body, infant-scale musculoskeletal computer model they created. Finally, they used computer algorithms to analyze the spatiotemporal (both space and time) features of the interaction between input signals and muscle activity.

“We were surprised that during spontaneous movements, infants’ movements ‘wandered’ and they followed different sensorimotor interactions. We named this phenomenon ‘sensorimotor wandering,'” Kanazawa said. “It is generally assumed that the development of the sensorimotor system generally depends on the occurrence of repeated sensorimotor interactions, meaning that the more you perform the same task the more likely you are to learn and remember it.

“However, our results imply that infants develop their own sensorimotor system based on exploratory behavior or curiosity, so they do not repeat the same action but different actions. In addition, our findings provide a conceptual link between early spontaneous movements and spontaneous neuronal activity.”

Previous studies in humans and animals have shown that motor behavior (movement) involves a small set of primitive muscle control patterns. These are patterns that are typically seen in task-specific or cyclical movements, such as walking or reaching. The results of this latest study support the theory that infants and toddlers can acquire sensorimotor modules, i.e., synchronized muscle activities and sensory input, through spontaneous whole-body movements without a clear purpose or function.

Even through sensorimotor wandering, children showed increases in coordinated whole-body movements and anticipatory movements. Compared to the random movements of the newborn group, the movements performed by the infant group showed more regular patterns and sequential movements.

Next, Kanazawa wants to see how sensorimotor degeneration affects later development, such as walking and reaching, along with more complex behaviors and higher cognitive functions. “My original background is in infant rehabilitation. My big goal through my research is to understand the mechanisms underlying early motor development and find knowledge to help promote child development.”

The work is published in the journal Proceedings of the National Academy of Sciences.