Brain stimulation improves aging short-term memory for a month, study finds

Sending electrical currents to two parts of the brain known to store and recall information slightly boosted immediate word recall in people over 65, according to a researcher. study by a team from Boston University published Monday in Nature Neuroscience.

“Whether these improvements would occur for everyday memories, rather than word lists, remains to be tested,” said Masud Husain, professor of neurology and cognitive neuroscience at the University of Oxford. , in a press release. He did not participate in the study.

Still, the study “provides important evidence that stimulating the brain with small amounts of electrical current is safe and may also improve memory,” said Dr. Richard Isaacson, director of the Disease Prevention Clinic. Alzheimer’s at the Center for Brain Health at Florida Atlantic’s Schmidt University. College of Medicine, which did not participate in the research.

The improvements were more pronounced in the people in the study with the weakest memories, who “would be considered to have mild cognitive impairment,” said neuroscientist Rudy Tanzi, professor of neurology at Harvard Medical School, who n did not participate in the study.

“There was an apparently beneficial effect on immediate word recall in people with mild cognitive impairment,” said Tanzi, who is also director of the Genetics and Aging Research Unit at Massachusetts General Hospital in Boston. .

“This preliminary but promising finding warrants further exploration of the use of bioelectronic approaches for disorders like Alzheimer’s disease,” he added.

Stimulate brain change

Scientists used to think that at some point in early adulthood the brain was fixed, unable to grow or change. Today, it is widely accepted that the brain is capable of plasticity – the ability to rearrange its structure, functions or connections – throughout life.

Transcranial alternating current stimulation, or tACS, attempts to improve brain functionality with a device that applies electrical currents to specific areas of the brain through electrodes on the scalp. Electrical waves can mimic or alter brain wave activity to stimulate growth and hopefully alter the brain’s neural network.

An alternative version that uses magnetic fields, called transcranial magnetic stimulation, or TMS, is approved by the US Food and Drug Administration to treat depression.

“I believe this is the future of neurological intervention, to help strengthen networks in our brains that may be failing,” said Dr. Gayatri Devi, clinical professor of neurology and psychiatry at the Zucker School of Medicine. Medicine from Hofstra/Northwell University in New York. She was not involved in the new study.

“Also, treatment can be tailored to each person, based on that individual’s strengths and weaknesses, which drug therapy is not able to do,” Devi said.

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In the new findings published in Nature Neuroscience, brain cells are “activated at specific times, and that’s defined by the frequency of the (electrical) stimulation,” said study co-author Shrey Grover, a student. postdoctoral fellowship in brain, behavior and cognition. program at Boston University.

“The consequence of altering the times at which brain cells activate is that it induces this process of plasticity. Plasticity is what allows the effects to continue over time even when the stimulation is over,” he said. -he adds.

Memories fade

As the brain ages, it is common to lose some memory capacity. For some people, it may be short-term memory that suffers the most: Where did I park my car at the mall on that shopping spree? Others may have memory problems over a longer period: Where did I park my car two weeks ago before flying out for vacation? And some struggle with both types of memory.

The Boston University researchers analyzed longer-term memory and short-term or working memory separately in two experiments, each with randomized groups of 20 people between the ages of 65 and 88. The experiments alternated between applying gamma waves at 60 hertz and theta waves at 4 hertz. to two brain centers that play a key role in memory.

Gamma waves are the shortest and fastest of the brainwave frequencies, operating between 30 and 80 hertz, or cycles per second. Certain brain waves called high-gamma were clocked at up to 100 hertz.

A brain on gamma waves is intensely and fully engaged. People under stress who need to be focused on the laser – such as when taking a test, solving a complex problem, or solving a difficult mechanical problem – can produce gamma waves.

Theta waves are much slower, ranging between four and eight cycles per second. You’re probably on autopilot when you’re in theta mode – driving to work without thinking about the route, brushing your teeth or hair, or even daydreaming. It’s often when people brainstorm an idea or find a solution to a problem. Studies have shown that theta activity can predict learning success.

Target brain memory areas

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In the first experiment, one group received high frequency (60 hertz) gamma waves into their prefrontal cortex, which is directly behind the eyes and forehead. As a center of learning and cognition, the prefrontal lobe helps store long-term memories.

Another group of 20 received low-frequency (4 hertz) theta stimulation of the parietal cortex, an area of ​​the brain just below where a ponytail would sit. The parietal cortex sits above the hippocampus, another part of the brain that plays a major role in learning and memory. People with Alzheimer’s disease often have a shrunken hippocampus because the organ is losing tissue and shrinking.

A third group of 20 people underwent a sham process to serve as a control group.

The sessions took place over four consecutive days. Each person took five 20-word recall tests during the daily 20-minute stimulation. They were asked to immediately recall as many words as possible at the end of each of the five tests.

The research team assessed performance in two ways: How well did participants remember the words at the end of the list they had just heard? This would be the measure of short term or working memory. How many words could they remember from the beginning of each list, which would have been minutes in the past? This result would assess the ability to remember for a somewhat longer period.

The results showed that 17 out of 20 people who received high-frequency gamma stimulation improved their ability to remember words since starting the word test – which the researchers called longer-term memory.

Similarly, 18 of 20 participants who underwent low-frequency theta stimulation improved their short-term working memory, or ability to recall the words heard last.

Compared to the group of people receiving the sham or placebo stimulation, those who received the treatments saw results that “translate into older adults remembering, on average, four to six more words on the list. of 20 words at the end of the 4 day intervention,” said study co-author Robert Reinhart, director of the Cognitive & Clinical Neuroscience Laboratory in Boston. University.

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“It is important to emphasize that the study primarily shows a modest but significant improvement in short-term memory, but does not show clear effects on long-term memory since the test was based on recalling words only one minute after learning the words,” Tansi said.

“Cognitive experts would say what you remember an hour ago is long-term memory,” Tanzi added. “But when it comes to clinical symptoms of Alzheimer’s disease and age-related memory impairment, we would lump them together under short-term memory. When we say that patients with Alzheimer’s disease retain long-term memory, we refer to recalling details of their wedding day.”

Personalized treatment

Switching the areas of the brain that received theta and gamma stimulation in a second experiment produced no benefit, according to the study. A third experiment with 30 people was done to verify the previous results.

One month after the intervention, participants were asked to do another word recall test to see if the memory improvements lasted.

Overall, the results showed that low-frequency theta currents improved short-term working memory at one month, unlike high-frequency gamma stimulation. The reverse was true for longer-term memories – gamma, but not theta, performance enhancement.

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“Depending on the spatial location and frequency of electrical stimulation, we can separately enhance short-term memory or long-term memory,” explained Reinhart, assistant professor in the Department of Psychological and Brain Sciences at the Institute. Boston University.

This means researchers can tailor treatment to a person’s needs, Reinhart said.

What would that look like? The devices are well tolerated, with little or no side effects.

“In an ideal world, a portable, home device that could deliver this therapy would be the end goal,” said Isaacson, trustee of the McKnight Brain Research Foundation, which funds research into aging brains.

“Right now, it’s cumbersome to receive these treatments because specialized equipment is required. It can also be time-consuming and expensive,” Isaacson added. “Yet there are limited treatment options for cognitive aging, which affects tens of millions of people, so this is a hopeful step forward in treating symptoms and improving brain health.”

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