Those seemingly random kicks or wiggles a newborn baby makes have a purpose.
With each movement, the baby is developing its sensorimotor system, which it will later use to perform sequential movements. The sensorimotor system lets a person control muscles, movement and coordination.
Researchers studying these “spontaneous” newborn movements and comparing them to babies a few months older found patterns of muscle interaction developing based on the newborns' exploratory behavior.
“Previous research into sensorimotor development has focused on kinematic properties, muscle activities which cause movement in a joint or a part of the body,” said Hoshinori Kanazawa, a project research associate at the University of Tokyo in Japan.
“However, our study focused on muscle activity and sensory input signals for the whole body. By combining a musculoskeletal model and neuroscientific method, we found that spontaneous movements, which seem to have no explicit task or purpose, contribute to coordinated sensorimotor development,” Kanazawa said in a university news release.
For the study, the researchers used motion capture technology to record the joint movements of 12 healthy babies under 10 days of age as well as 10 infants who were about 3 months old.
The researchers used a computer model to estimate the babies' muscle activity and sensory signals. Computer algorithms helped them analyze features of the interaction in both the space and time between input signals and muscle activity.
“We were surprised that during spontaneous movement, infants' movements ‘wandered' and they pursued various sensorimotor interactions,” Kanazawa said. He noted that it is often assumed that sensorimotor development depends on repeated interactions, "meaning the more you do the same action the more likely you are to learn and remember it.”
But the investigators found that infants appeared to develop their own sensorimotor system based on explorational behavior or curiosity, not just repeating the same action, but a variety of actions.
“In addition to this, our findings provide a conceptual linkage between early spontaneous movements and spontaneous neuronal activity,” Kanazawa explained.
These results support the theory that babies can acquire synchronized muscle activities and sensory inputs through spontaneous whole-body movements without a specific purpose, the study authors noted. Even in their "wandering," the babies showed an increase in coordinated whole-body movements.
The older infants had more common patterns and movements compared to the newborns' random movements, the findings showed.
Knowing how the sensorimotor system develops could be used to better understand the origin of human movement and to diagnose developmental disorders, such as cerebral palsy, earlier.
Scientists know from past research that human and animal movement involves a small set of primitive muscular control patterns, which are typically seen in cyclic or task-specific movements, like walking or reaching.
Kanazawa plans to study how sensorimotor wandering affects later development, such as walking and reaching, along with more complex behaviors and higher thinking functions.
“My big goal through my research is to understand the underlying mechanisms of early motor development and to find knowledge that will help to promote baby development,” he said.
The report was published Dec. 27 in the Proceedings of the National Academy of Sciences.
Northeastern University in Boston has more about human movement science.
SOURCE: University of Tokyo, news release, Dec. 26, 2022