Researchers find causal link between running speed and enhanced learning

April 16, 2018, Champalimaud Centre for the Unknown
From left to right: Tatiana Silva, Catarina Albergaria, Dominique Pritchett and Megan Carey. Credit: Paco Romero

A new study, published in the journal Nature Neuroscience by a team from the Champalimaud Centre for the Unknown, in Lisbon, Portugal, has shown that the faster mice run, the faster and better they are at learning.

"Our main finding was that we could make mice learn better by having them run faster," says Catarina Albergaria, first author of the new study.

The neuroscientists were studying something else altogether. "Our initial goal was to relate cellular plasticity in the brain to learning," adds Albergaria. Ultimately, they sought to understand how neural circuits in a part of the brain called the are changed by the learning of a motor task.

"The cerebellum is important for learning skilled movements," says Megan Carey, who led the study. "It calibrates movements in the face of a changing environment to coordinate them in a very precise way."

To understand the cellular changes in the cerebellum that accompany learning, the researchers were studying a classical conditioning learning task, akin to Pavlov's famous dog conditioned behavior of salivating when it heard a bell just because it had learned to associate that sound with being fed.

In these experiments, while running on a treadmill, the mice had to learn to close their eyelids in response to a light flashed immediately before they received an air puff to the eye (which normally evokes a reflexive blink). This is a form of learning that takes place in the cerebellum.

However, the experiments the scientists undertook to look into this question just didn't work. The team couldn't see any effects of the learning task because there was too much variability in the data they obtained from different mice—and even from trial to trial with the same animal. What created this recurring contaminant noise? "The experiments were unsuccessful for a long time," recalls Albergaria.

At a certain point, they understood what was happening .The mutant mice they were using couldn't really run very well. When they took into account their running speed, the "noise" in the data cleared. Further, when all the animals were set to run at faster speeds, they had similar learning curves and maximum eyelid conditioning performance. "This was a pretty surprising result," says Carey.

This confirmed that there was a causal link between running speed and enhanced learning—and not just a correlation. "The finding that externally imposed changes in running speed are sufficient to modulate learning (...) provide[s] causal evidence that increases in locomotor activity enhance learning," the authors write in their paper.

The team further showed that once the mice had learned the task, their subsequent performance of that task still depended on their running speed. "The mice performed less well when we slowed down the treadmill, and this happened at time scales of a few seconds," says Albergaria. "That's how the the apparently random variability in learning and performance, which we were trying to eliminate, became the story," says Albergaria. "Now, we wanted to figure out the brain mechanism behind this link between running and learning."

Where in the brain was this enhancement happening? First, the scientists asked whether the effect of running on learning was specific to the visual system. For example, was it just that the mice could see better when running, and thus learned better?

They trained the mice to close their eyelids when experiencing other types of sensory stimuli (such as hearing a tone or feeling a vibration on their whiskers) before the air puff. And indeed, they found the same effect of running speed on learning in all of these different sensory modalities, just as they had with the visual stimuli.

What this commonality meant was that the neural process driving the learning enhancement was independent of the sensory system involved, suggesting that it might take place after the sensory signals had been processed by visual, auditory or tactile areas in cerebral cortex. The researchers then turned to the cerebellum.

Using the technique of optogenetics, which allowed them to stimulate specific neurons directly with laser light, they stimulated neurons that project to the cerebellum through axons dubbed mossy fibers. "We substituted motor activity with direct stimuli to the cerebellum and we found that if you are able to increase the activity of the mossy fibers, you enhance learning," explains Albergaria."We found the place in the cerebellum where this modulation takes place," emphasizes Carey.

What about humans? "The cerebellum is a well-conserved structure across species, and there are circuits that are common across species," replies Albergaria, speculating that the finding "could well apply to other forms of cerebellar learning in humans." One implication of their findings was that "it doesn't necessarily need to be locomotion; anything that drives an increase in mossy fiber activity could provide an equivalent modulation of learning," says Albergaria. However, she cautions, "we don't know whether this is true for other, non-cerebellar kinds of learning."

If it were so, this could have general implications for learning in humans. Ever wonder why you sometimes need to pace around the room when you have a difficult problem to solve? Might it be because we think better when we walk, because we are better at organizing our ideas on the move? "We tend to think that to manipulate the plasticity of the brain, so that people learn faster and slow learners improve, we have to use drugs," says Carey. "But here, all we had to do was control how fast were running to obtain an improvement. It would be interesting to see if this holds for humans, for cerebellar forms of learning—and even for other types of learning."

Explore further: Scientists illuminate mechanism at play in learning

More information: Catarina Albergaria et al, Locomotor activity modulates associative learning in mouse cerebellum, Nature Neuroscience (2018). DOI: 10.1038/s41593-018-0129-x

Related Stories

Scientists illuminate mechanism at play in learning

March 15, 2018
The process we call learning is in fact a well-orchestrated symphony of thousands of molecular reactions, but the exact interplay between these reactions remains largely unknown. Now, researchers at the Okinawa Institute ...

Mice, motor learning, and making decisions

March 1, 2018
Early understandings of the brain viewed it as a black box that takes sensory input and generates a motor response, with the in-between functioning of the brain as a mystery.

Getting a leg up: Hand task training transfers motor knowledge to feet

March 30, 2017
The human brain's cerebellum controls the body's ability to tightly and accurately coordinate and time movements as fine as picking up a pin and as muscular as running a foot race. Now, Johns Hopkins researchers have added ...

Running helps the brain counteract negative effect of stress, study finds

February 14, 2018
Most people agree that getting a little exercise helps when dealing with stress. A new BYU study discovers exercise—particularly running—while under stress also helps protect your memory.

Our elegant brain: Motor learning in the fast lane

August 3, 2015
It takes a surprisingly small cluster of brain cells deep within the cerebellum to learn how to serve a tennis ball, or line up a hockey shot. Researchers at McGill University led by Kathleen Cullen from the Department of ...

Researchers optimize methods to study neurons during motor activity

March 10, 2016
Researchers have optimized the techniques for studying motor learning in order to repeatedly assess the activity of neurons for days, weeks, or even months. These sophisticated approaches allow the further characterization ...

Recommended for you

Study of protein 'trafficker' provides insight into autism and other brain disorders

September 22, 2018
In the brain, as in business, connections are everything. To maintain cellular associates, the outer surface of a neuron, its membrane, must express particular proteins—proverbial hands that reach out and greet nearby cells. ...

Breast milk may be best for premature babies' brain development

September 21, 2018
Babies born before their due date show better brain development when fed breast milk rather than formula, a study has found.

Early warning sign of psychosis detected

September 21, 2018
Brains of people at risk of psychosis exhibit a pattern that can help predict whether they will go on to develop full-fledged schizophrenia, a new Yale-led study shows. The findings could help doctors begin early intervention ...

White matter repair and traumatic brain injury

September 20, 2018
Traumatic brain injury (TBI) is a leading cause of death and disability in the U.S., contributing to about 30 percent of all injury deaths, according to the CDC. TBI causes damage to both white and gray matter in the brain, ...

Gut branches of vagus nerve essential components of brain's reward and motivation system

September 20, 2018
A novel gut-to-brain neural circuit establishes the vagus nerve as an essential component of the brain system that regulates reward and motivation, according to research conducted at the Icahn School of Medicine at Mount ...

Genomic dark matter activity connects Parkinson's and psychiatric diseases

September 20, 2018
Dopamine neurons are located in the midbrain, but their tendril-like axons can branch far into the higher cortical areas, influencing how we move and how we feel. New genetic evidence has revealed that these specialized cells ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.