Electrical stimulation of the nervous system can improve motor learning

Scientists meticulously calculate the process. First, electricity is delivered to a nerve in the forearm of a test subject. Milliseconds later, magnetic stimulation is applied to the motor area of their brain using a coil placed on their head. The immediate effect is visible as small, involuntary twitches in the subject's hand. Ten seconds later, the process is repeated.

While this may evoke images of Dr. Frankenstein at work, the reality is that of pioneering research into the brain’s capacity to learn that could unlock new understandings of brain function and provide new avenues for motor training and rehabilitation. The young, healthy test subjects reportedly felt almost nothing during the process, but displayed enhanced benefits from their motor training session thereafter.

“The goal of the stimulation is to influence spinal cord networks from two sides using electrical impulses. When done repeatedly and timed precisely, the network's efficiency can be increased. Our new findings show that this can also enhance people’s abilities to learn motor skills afterward. That’s what our research demonstrates,” explains Jonas Rud Bjørndal, a Ph.D. from the Department of Nutrition, Exercise, and Sports and one of the study’s lead researchers.

In the study by Bjørndal, Jesper Lundbye-Jensen and their colleagues, now published in Nature Communications, test subjects were shown to be able to enhance their training outcomes and boost their performance of motor tasks by up to 30% after receiving a stimulation prior to training.

On average, participants improved their abilities by about 20% with training alone, making the stimulation-induced gains significant. The research involved a series of four experiments using so-called paired stimulations of the brain and peripheral nerves.

But Jesper Lundbye-Jensen, an associate professor and head of the Movement and Neuroscience Section at the Department of Nutrition, Exercise, and Sports, cautions that this is no miracle method:

“You won’t get better at something – or become a champion javelin thrower – just by having weak currents sent through your nervous system. That probably comes as no surprise. But our research does show that combining stimulation with subsequent training can significantly enhance the benefits of one’s training, potentially making it a major help along the way.”

Brain plasticity is the key to learning

When learning motor-intensive tasks, whether it’s moving one’s fingers as quickly as possible – as in the study – playing guitar, or throwing a javelin, the brain must be able to physically change with practice. This is possible due to its plasticity.

“The brain and central nervous system networks must be able to physically adapt because that’s how we learn. These changes in the nervous system are also essential for memory, allowing us to retain and recall what we’ve learned,” explains Lundbye-Jensen.

The new study builds on previous research showing that brain plasticity can be positively influenced by stimulation of the brain and peripheral nerves e.g. through the forearm. The researchers have succeeded in demonstrating that, with precise settings and timing, this plasticity – and a readiness to learn – can be enhanced with such repeatedly paired electrical and magnetic stimulations which collide in the spinal cord.

“Since we and others have shown in earlier studies that the ability to learn motor skills is linked to plastic changes in the nervous system, it was a logical step to explore whether these two factors could have a combined effect. Our findings demonstrate that there is indeed a significant benefit,” says Bjørndal.

The researchers emphasize the importance of precise timing for the paired stimulations as a critical contribution to the field. Should the timing of the stimulations be off, the effect is much less pronounced.

“This makes the method more challenging to apply, but it aligns with our knowledge of the mechanisms involved in brain plasticity – that precisely timed, repeated activations can contribute to strengthening nervous system connections. What’s new here is that subsequent training can leverage the effects that the stimulation creates in the nervous system. This knowledge is fundamentally interesting and will be exciting to expand upon in future research,” Bjørndal adds.

New perspectives for rehabilitation – and perhaps elite sports

The findings provide fresh insight into the relationship between brain plasticity and the effects of motor training. While the extent to which this knowledge will help people improve motor function remains uncertain, the researchers hope that their results benefit society.

Initially, the technique could open new possibilities for rehabilitation strategies used in physiotherapy, healthcare and eldercare.

“There are people in our society who, due to nervous system injuries, for example, face steep uphill battles to regain mobility. Obviously, training is essential. But if new methods – including our research, in the long run – can make this training more effective, even by a small margin, it would be extremely satisfying,” says Lundbye-Jensen.

Additionally, stimulation techniques could also prove beneficial to elite athletes, particularly in disciplines that involve ballistic movements which are reliant upon explosive muscle power. However, anyone eager to test these experimental methods to boost their own training may find it challenging to access the equipment, which is currently limited to university and hospital researchers and staff.

About the Study

The research consisted of four experiments with a total of 82 participants aged 20-30. Participants practiced a so-called ballistic motor task involving rapid movements of the index finger.

The effect is believed to stem from strengthening neural connections through repeated, simultaneous activations of neural pathways – a principle that can be summarized as, “what fires together, wires together.”

Researchers tested nerve conduction in participants before the experiments in order to precisely time the stimulations, a critical factor for the study's success.

The effect lasted for up to a week after training, indicating a lasting impact. However, further research is needed to explore long-term effects, as this study focused on short-term outcomes.

This research project is a proof-of-principle study that primarily serves to prove the mechanism's effect. Future studies will investigate its practical applications in various contexts and possibly, its potential effects on other types of learning.

The following researchers contributed to the study:

Jonas Rud Bjørndal, Lasse Jespersen and Jesper Lundbye-Jensen from the University of Copenhagen’s Department of Nutrition, Exercise and Sports.

Mikkel Malling Beck from the MR-research section at Hvidovre and Amager Hospital.

Lasse Christiansen from the MR-research section at Hvidovre and Amager Hospital and the University of Copenhagen’s Department of Nutrition, Exercise and Sports.