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For years, researchers have sought to untangle a complicated question: Can gently stimulating the human brain with electrical currents enhance learning and memory? Despite several indications that it may do so, questionable and sometimes conflicting results (especially those touted by biotechnology companies selling alleged memory-enhancing wearables) have made it difficult to draw definitive conclusions. However, new research that tested whether transcranial alternating current stimulation (tACS), a technique that transmits a mild electrical current through the brain via electrodes on the scalp, suggests that it can enhance some people’s ability to remember new things.
The study, published today (August 22) in Nature Neuroscience, involved 150 volunteers between the ages of 65 and 88 who received 18 to 20 minutes of tACS during a single session. Compared with controls that received sham stimulation, those that received tACS were better able to recall words from a list of 30 words presented to them minutes prior to stimulation. Their improved ability to recall words became measurable as soon as two days later and lasted for at least a month after. It also showed how targeting different brain regions conferred different benefits, with stimulation of the parietal cortex enhancing working memory and stimulation of the prefrontal cortex improving long-term memory, both by roughly 50 to 65 percent over controls.
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The study “provides important evidence that stimulating the brain with small amounts of electrical current is safe and can also improve memory,” Richard Isaacson, director of the Alzheimer's Prevention Clinic in the Center for Brain Health at Florida Atlantic University's Schmidt College of Medicine, tells CNN.
But it’s the specificity of the study that really makes it novel compared to similar work, experts say.
“This is one of the first—maybe the first—study to look at, not just stimulating the brain, but really a brain area with a specific frequency to have a specific effect on memory,” Daniel Press, chief of cognitive neurology at Beth Israel Deaconess Medical Center in Boston, tells The Wall Street Journal. “That’s really one of the take home messages here—that it’s not just about stimulating a brain area, but it’s about stimulating a brain area at a specific frequency, so that it can then drive network communication,” adds Press, who wasn’t involved in the research.
The researchers say the work may one day lead to new ways to help people with Alzheimer’s, Parkinson’s, or other neurodegenerative diseases. Though none of the study volunteers had diagnosed neurological conditions, the researchers found that those with lower baseline cognitive performance experienced greater memory boosts than those who were already performing better at the memory task.
Study coauthor and Boston University neuroscientist Robert Reinhart tells The Financial Times, that the finding “bodes well for transferring this [procedure] over to a proper clinical study in people with Alzheimer’s disease who are suffering from more severe memory impairments.”