Frontier: Stimulation enhances long-term learning

by Brenda Patoine

November, 2007

Stimulating the brain during learning can improve long-term memory, at least for one type of learning, according to research from the National Institute for Neurological Disorders and Stroke and presented at the meeting.

Researchers working with healthy volunteers used a noninvasive technique called transcranial direct current stimulation (tDCS). Previous research has shown that this technique can change the pattern of nerve cell firing in the cortex and enhance short-term learning of motor tasks, but the effects on long-term learning had not been evaluated.

Transcranial direct current stimulation delivers a low-level electrical current directly to the brain via electrodes placed on the surface of the scalp. By changing the location of the electrodes, researchers can direct the current to a particular area of the cortex. This study used two electrodes; one positioned over the motor cortex, which controls movement, and the other over an area above the eyebrow.

Depending on the type of current used, tDCS can either increase or decrease nerve cell firing. In this study, participants underwent five daily applications of anodal tDCS, which boosts nerve cell firing, lasting 20 minutes each. One group received tDCS during the learning of a task that involved hitting targets on a computer screen with a cursor controlled by a grip-activated, hand-held device, a well-studied model for visual-motor learning. A second group received it immediately following the task, and a third group served as controls, receiving only “sham” tDCS.

Applying the current during the learning period resulted in better learning and recall of the task at all time points, including three months later. “We think this is really clinically relevant,” researcher Janine Reis said. “This is the first time we’ve shown that anodal tDCS during training improves motor learning long-term.”

The findings suggest a possible strategy for enhancing motor skill rehabilitation in people with neurologic injury such as stroke or spinal trauma, the authors said.