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


Fancy a little non-invasive brain stimulation to boost your old memory for that next big project, work meeting, or family gathering? One day, science may be able to offer such treatments, new research suggests.

Sending electrical current to two parts of the brain known for storing and recalling information modestly improved instant word recall in people over 65, according to one study. study by a team from Boston University, published Monday in Nature Neuroscience.

“Whether these improvements would occur for everyday memories, rather than just word lists, remains to be tested,” Masud Husain, a professor of neurology and cognitive neuroscience at the University of Oxford, said in a statement. He was not involved in the investigation.

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 Alzheimer’s Prevention Clinic at Schmidt’s Center for Brain Health, Florida Atlantic University. College of Medicine, which was not involved in the study.

Improvements were most pronounced in people in the study with the worst memories, who “would be considered mild cognitive impairment,” said neuroscientist Rudy Tanzi, a professor of neurology at Harvard Medical School, who was not involved in the study.

“There was an apparent beneficial effect on instant 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 more research into the use of bioelectronic approaches for conditions such as Alzheimer’s disease,” he added.

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

Transcranial alternating current stimulation, or tACS, attempts to improve brain functionality with a device that uses wave-like electrical currents to specific areas of the brain through electrodes on the scalp. The 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, has been approved by the U.S. 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, a clinical professor of neurology and psychiatry at the Zucker School of Medicine at Hofstra/Northwell University in New York. York. She was not involved in the new study.

“In addition, treatment can be tailored to each person, based on that person’s strengths and weaknesses, which is something pharmacotherapy cannot do,” Devi said.

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

“The consequence of changing the timing at which brain cells are activated is that it induces this process of plasticity. The plasticity allows the effects to be transferred over time even when the stimulation has ended,” he added.

As the brain ages, it’s common to lose some of its ability to remember. For some people, short-term memory may suffer the most: where did I park my car in the mall during this shopping trip? Others may have trouble remembering things over a longer period of time: Where did I park my car two weeks ago before going on vacation? And some struggle with both types of memory.

The Boston University researchers analyzed both slightly longer-term memory and short-term or working memory separately in two experiments, each involving randomized groups of 20 people ages 65 to 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. Some brain waves are called high-gamma are clocked to 100 hertz.

A brain on gamma waves is intense and fully engaged. People under stress who need laser focus — such as when doing 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, even daydreaming. This is often when people are mulling over an idea or coming up with a solution to a problem. Studies have shown that theta activity can predict learning success.

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

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

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

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

The research team evaluated performance in two ways: how well did participants remember words at the end of the list that they would have just heard? That would be the measure of short-term or working memory. How many words could they remember at the beginning of each list, which in the past would have been minutes? Would rate that result the ability to remember something longer.

The results showed that 17 out of 20 people who received high-frequency gamma stimulation improved in their ability to remember words from the start of the word test — what the researchers say called long-term memory.

Similarly, 18 out of 20 participants who received theta stimulation at a lower rate improved their short-term working memory, or their ability to last heard words.

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

“It is important to emphasize that the study mainly shows a modest but significant improvement in short-term memory, but no apparent effects on long-term memory, as the test was based on the word learning only a minute or so after learning the words.” remembering words,” Tanzi said.

“Cognitive experts would say that what you remember an hour ago is long-term memory,” Tanzi added. “But with regard to the clinical signs of Alzheimer’s and age-related memory impairment, we would group this into short-term memory. When we say Alzheimer’s patients retain long-term memory, we mean remembering details of their wedding day.”

Flipping the brain regions that received the theta and gamma stimulation in a second experiment showed no benefits, the study found. A third experiment with 30 people was done to verify previous results.

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

Overall, the results showed that low-frequency theta currents improved short-term working memory after one month, while higher-frequency gamma stimulation did not. The opposite was true for the long-term memories – gamma, but not theta, improved performance.

“Based on the spatial location and frequency of the electrical stimulation, we can individually improve short-term memory or long-term memory,” explains Reinhart, an assistant professor in Boston University’s department of psychological and brain sciences.

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

How would that be? The devices are well tolerated, with limited to no side effects.

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

“For the time being, it is cumbersome to undergo these treatments, because specialized equipment is needed. It can also be time-consuming and costly,” 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 addressing symptoms and improving brain health.” improve.”

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