Over the past 25 years, Pablo Celnik has performed dozens of studies aimed at determining precisely how the brain learns new skills following a stroke and identifying which areas of the brain help orchestrate them. Now, the director of the Johns Hopkins Department of Physical Medicine and Rehabilitation and fellow researchers have drawn from previous behavioral and neurophysiological studies using transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) to review how these treatments can activate neural regions and enhance motor skill learning. 

“By reassessing data from numerous studies,” says Celnik, “we can better define and understand the ‘bigger picture’ about motor learning.”

The paper, “Multiple Motor Learning Processes in Humans: Defining Their Neurophysiological Bases,” was published in The Neuroscientist and reviews studies on four different forms of learning: error-based learning, reinforcement learning, use-dependent learning and cognitive strategies. “Each has a different process involved, weighting different nodes of the motor system network, altogether helping inform how overall motor learning occurs,” he says.

Earlier data from Celnik’s lab and other researchers’ work on TMS and tDCS studies documented the parts of the brain involved in the acquisition and retention of voluntary movements and motor skills. Overall, the researchers found that when tDCS was applied over specific brain regions that control some aspects of motor function, patients and healthy individuals showed increased brain activity and better retention of new memories. 

“Those results offer hope in teaching patients with stroke to improve motor function,” says Celnik, who also leads the Clinical Noninvasive Brain Stimulation Program at the Johns Hopkins University School of Medicine. 

“In the long run, we hope to see if stimulating specific parts of the brain in patients recovering from a brain injury can increase motor neuron function,” says Celnik. “For instance, if a person has brain damage in one region, affecting one of the motor learning processes, then we could recruit another brain region to compensate for the deficit. Brain stimulation could help augment an alternative motor learning process to help learn the new behavior.” 

The next step for Celnik and his colleagues is to determine whether different learning processes supplement each other during an illness. If so, that suggests that when one area of the brain has a lesion, another part of the brain might be able to compensate. This finding could enable clinicians to develop approaches to reinforce that learning, in hopes of hastening progress after a brain injury.