Motor systems in the brain may drive a baby's earliest social thinking and goal imitation. 
Source: XStudio3D/Shutterstock

A groundbreaking new study by neuroscientists and developmental psychologists at the University of Chicago has identified a direct link between neural responses from the motor system and overt social behavior in infants.

The April 2016 study, "Motor System Activation Predicts Goal Imitation in 7-Month-Old Infants," was published today in the journal Psychological Science. The goal of this study was to identify how young infants' brains process other people's actions in a social context.

During the experiment, 7-month-old infants were tested and observed while wearing an electroencephalography (EEG) cap to measure brain activity, while an actor reached for one of two toys. Immediately after observing the actor reaching for a toy, the baby was allowed to select one of either toys. The researchers repeated this procedure 12 times.

Babies' Brains May Process Social Thinking Via Motor Systems

The researchers used EEG to measure a specific aspect of brain activity called "desynchronization" in the mu frequency band. This brain-wave frequency has been linked to motor cortex activity in adults. Interestingly, just like adults, the infants showed similar types of brain activity both when acting themselves and when they were observing the actor’s motor movements.

Life Science Databases/Wikimedia Commons
Motor systems are housed throughout the cerebral cortex of the cerebrum (in red). 
Source: Life Science Databases/Wikimedia Commons

The researchers found that when an infant recruited his or her motor system while observing the actor grasp one of the toys, the infant automatically imitated the actors movements and toy choice. These findings suggest that the motor system plays a central role in babies' perceptions of other people’s actions. Until this study, nobody has tested the link between the motor cortex and social thinking in infants.

Notably, whenever a baby did not imitate the actor, there was no detectable activation of the motor system while watching the actor. It became clear to the researchers monitoring the EEG that the babies' brain activity while watching the actors decision-making could predict which toy the baby would choose based on mimicking the actor's behavior.

In a statement, lead author Courtney Filippi, a doctoral candidate in developmental psychology at the University of Chicago, said, "Our research provides initial evidence that motor system recruitment is contingently linked to infants' social interactive behavior. It provides initial evidence that recruiting the motor system during action encoding predicts infants' subsequent social interactive behavior."

Source: bikeriderlondon/Shutterstock

Fundamentally, the researchers have identified the neural processes that contribute to intelligent social behavior in infants. This is the first evidence showing that motor system activation in infants predicts the imitation of others' actions, as well as an apparent understanding of others' goals.

Amanda Woodward, Professor of Psychology at University of Chicago, and co-author of the study, concluded, 

"This is big news, that babies understand what they are observing, that there is a direct connection between observing others, understanding what others are doing, and learning how to act ... Although this research will not translate directly into new medical treatments or therapies, it could contribute to medical advances down the road by helping to illuminate how the human brain functions and develops.

One reason to engage in basic science is to better understand the development of the brain and mind. Here we looked at the development of social cognition, social behavior, and the motor system, all of which are critical for human development and are often disrupted in developmental disabilities, including autism."

Early Cerebellum Malfunction Hinders Neural Development of Motor Systems

When I read the new study from University of Chicago this morning, the first thing that popped into my head was that it seemed to dovetail with research on the cerebellum (Latin for "little brain") and autism spectrum disorders (ASD) being conducted by Samuel S. Wang. Sam Wang is a professor of molecular biology at Princeton University. 

As a retired athlete, parent, and son of a neuroscientist, I have an ongoing (albeit somewhat esoteric) fascination with the potential role that the cerebellum plays in many aspects of childhood development. I’m always on the lookout for empiric evidence on ways to optimize brain structure and functional connectivity throughout the lifespan by engaging both hemispheres of the cerebellum.

When I was growing up, my father (who was obsessed with the cerebellum) was my tennis coach. From a young age, my dad pounded it into my head that the Purkinje cells of the cerebellum were the seat of muscle memory. His coaching mantra to me was, "Chris, think about hammering and forging the muscle memory of your cerebellum with every stroke." He passed his curiosity about the cerebellum on to me as an athlete, parent, and science writer.

Historically, the cerebellum has been considered by most experts to be the part of our brain that integrates sensory information and coordinates motor movements. However, many leading neuroscientists now believe that the cerebellum plays a pivotal role in our cognitive function, emotional states of mind, and social thinking.

Life Sciences Database/Wikimedia Commons
The cerebellum (in red) fine-tunes and coordinates motor movements, but may also play a role in fine-tuning cerebral functions associated with emotional regulation, cognition, and social thinking. 
Source: Life Sciences Database/Wikimedia Commons

In recent years, I’ve written a wide range of Psychology Today blog posts reporting on cutting-edge research which has identified a previously unrecognized correlation between ASD and abnormalities in the cerebellum. For example, Sam Wang has a theory that early cerebellum malfunction hinders neural development of the cerebral cortex and disrupts the brain's processing of external and internal information, which may be a possible root of autism.

In April 2014, Wang et al. published, "The Cerebellum, Sensitive Periods, and Autism," in the journal Neuron. Based on a review of existing research, Wang and colleagues concluded that a cerebellar injury at birth makes someone 36 times more likely to score highly on autism screening tests. Cerebellar damage is the largest un-inherited ASD risk. (Cerebellar means "relating to or located in the cerebellum.")

Although the cerebellum has been largely overlooked for the role it plays in childhood development, the Princeton University researchers believe that the cerebellum holds many clues for better understanding the onset of autism. From my perspective, the new UChicago research on the role of motor regions in the cerebral cortex being linked to an infant's social development adds another puzzle piece to Wang’s hypothesis.

Sam Wang’s theory is that atypical cerebellar function or structure during early life potentially disrupts neural development and leads to what they call "developmental diaschisis." This term describes the chain reaction caused by a loss of function in one part of the brain that leads to problems in other brain regions.

Based on Sam Wang’s “development diaschisis” theory, malfunction of the cerebellum causes disruptions in how other areas of the brain develop and the brain's overall ability to interpret external stimuli and organize internal processes. In a statement, Wang summed up the ramifications of his hypothesis, 

"It is well known that the cerebellum is an information processor. Our neocortex [the largest part of the brain, responsible for much higher processing] does not receive information unfiltered. There are critical steps that have to happen between when external information is detected by our brain and when it reaches the neural cortex.

At some point, you learn that smiling is nice because Mom smiles at you. We have all these associations we make in early life because we don't arrive knowing that a smile is nice. In autism, something in that process goes wrong and one thing could be that sensory information is not processed correctly in the cerebellum."

In a statement, Mustafa Sahin, a neurologist at Boston's Children Hospital and associate professor of neurology at Harvard Medical School, said that Wang and his co-authors are building on previously identified links between cerebellar damage and ASD. Numerous studies—including research from Sahin's own lab—support Wang's theory. 

"Traditionally, the cerebellum has been studied in relation to motor movement and coordination in adults. Recent studies, however, strongly suggest that it also influences childhood cognition," Wang reiterated. "We hope to get people and scientists thinking differently about the cerebellum or about autism so that the whole field can move forward."

Photo and illustration by Christopher Bergland
This rudimentary sketch illustrates how motor systems in both hemispheres of the cerebrum and cerebellum are interconnected and codependent as part of a feedback loop.
Source: Photo and illustration by Christopher Bergland

"The association between cerebellar deficits and autism has been around for a while," Sahin added. "What Sam Wang and colleagues do in this perspective article is to synthesize these two themes and hypothesize that in a critical period of development, cerebellar dysfunction may disrupt the maturation of distant neocortical circuits, leading to cognitive and behavioral symptoms including autism."

The left hemisphere of the cerebrum controls the right side of the body; the left hemisphere of the cerebellum controls the left side of the body, and vice versa. Jeremy Schmahmann, of Massachusetts General Hospital (MGH) at Harvard Medical School, has a theory that the cerebellum might fine-tune thoughts and ideas much the same way it fine-tunes muscle movements. I think Schmahmann is onto something.

Conclusion: The Cerebellum May Take Center Stage in the 21st Century

The cerebellum is only 10% of brain volume but houses over 50% of the brain's total neurons. Because of this disproportionate distribution of neurons, my dad would often say, "We don't know exactly what the cerebellum is doing. But whatever it's doing, it's doing a lot of it."

When it comes to trying to solve the riddles of the cerebellum, I live by the words of Albert Szent-György, who once said, "Thus, the task is, not so much to see what no one has seen yet, but to think what nobody has thought yet, about what everybody sees." Every morning, I wake up hoping there will be new clues that help us better understand the cerebellum. Connecting the dots of the latest cerebellar research remains a work in progress. 

As an educated guess, I have a hunch that the latest research on the link between motor systems in the cerebral cortex with infants' social learning has strong cerebellar implications. To be clear: this is pure conjecture on my part. The new UChicago study did not involve the cerebellum in any way. That said, I will continue to keep my antennae up for any new research that corroborates my cerebellar hypotheses. Stay tuned!

To read more on this topic, check out my Psychology Today blog posts, 

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