“Whether these improvements would occur for everyday memories, and not just word lists, remains to be tested,” Masud Husain, professor of neurology and cognitive neuroscience at the University of Oxford, said in a statement. He did not participate in the study. However, the study “provides important evidence that stimulating the brain with small amounts of electricity is safe and may also improve memory,” said Dr. Richard Isaacson, director of the Alzheimer’s Prevention Clinic at the Florida Atlantic University Schmidt Brain Health Center. . College of Medicine, who was not involved in the research. The improvements were more pronounced in people in the study with the poorest memories, who “would be considered to have 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 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 investigation into the use of bioelectronic approaches for disorders such as Alzheimer’s disease,” he added.
Enhancing brain change
Scientists used to think that up until a certain point in early adulthood the brain was fixed, unable to grow or change. Today, it is widely understood 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 boost brain function with a device that applies electrical currents in waves to specific areas of the brain through electrodes on the scalp. Electric waves can mimic or alter brain wave activity to stimulate growth and hopefully change the brain’s neural networking. An alternative version that uses magnetic fields, called transcranial magnetic stimulation, or TMS, has been approved by the US Food and Drug Administration to treat depression. “I think this is the future of neurological intervention, to help strengthen networks in our brain that may be failing,” said Dr. Gayatri Devi, clinical professor of neurology and psychiatry at the Zucker School of Medicine at Hofstra University/Northwell in New . York. He was not involved in the new study. “Also, treatment can be tailored to each individual, based on the individual’s strengths and weaknesses, which drug therapy cannot do,” Devi said. In the new findings, published in Nature Neuroscience, brain cells “are activated at specific points in time and this is defined by the frequency of (electrical) stimulation,” said study co-author Shrey Grover, a postdoctoral fellow in brain, behavior and psychology. knowledge. program at Boston University. “The consequence of changing the time points at which the brain cells are activated is that it causes this plasticity process. It is the plasticity that allows the effects to carry over time even after the stimulation has ended,” he added.
Memories fade
As the brain ages, it is common to lose some of the ability to remember. For some people it may be short-term memory that suffers the most: Where do I park my car at the mall on this shopping trip? Others may have trouble remembering things for longer periods of time: Where did I park my car two weeks ago before getting on a plane for vacation? And some people struggle with both types of memory. Boston University researchers analyzed both short-term memory and short-term or working memory separately in two experiments, each with randomized groups of 20 people aged 65 to 88. Experiments alternated between applying gamma waves at 60 Hertz and theta waves at 4 Hertz. in two brain centers that play key roles in memory. Gamma waves are the shortest and fastest of the brain wave frequencies, operating between 30 and 80 Hertz, or cycles per second. Some brain waves referred to as high gamma have been clocked as high as 100 Hertz. A brain in gamma waves is intensely and fully engaged. People under stress who must focus on the laser — such as when taking a test, solving a complex problem, or solving a difficult engineering problem — may produce gamma waves. Theta waves are much slower and range between four and eight cycles per second. You’re probably running on autopilot when you’re in theta mode — driving to work without thinking about the route, brushing your teeth or hair, or even daydreaming. This often happens when people think of an idea or come up with a solution to a problem. Studies have found that theta activity can predict learning success.
Targeting memory areas of the brain
In the first experiment, one group received high-frequency (60 hertz) gamma waves in their prefrontal cortex, which is located just behind the eyes and forehead. As the center of learning and cognition, the prefrontal lobe helps store long-term memories. A different group of 20 people received low-frequency (4 hertz) theta stimulation in the parietal cortex, an area of the brain located just below where a ponytail would sit. The parietal cortex lies above the hippocampus, another part of the brain that plays an important role in learning and memory. People with Alzheimer’s often have a shrunken hippocampus as the organ loses tissue and shrinks. A third set of 20 subjects underwent a sham procedure to act as a control group. The sessions were held over four consecutive days. Each subject performed five 20-word recall tests during the daily 20-minute stimulation. They were asked to immediately recall as many words as they could at the end of each of the five tests. The research team assessed performance in two ways: How well did participants remember words from the end of the list that they would have 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 of time. The results showed that 17 of the 20 subjects who received high-frequency gamma stimulation improved in their ability to recall words from the beginning of the word test — what the researchers called long-term memory. Similarly, 18 of the 20 participants who underwent lower-frequency theta stimulation improved their short-term working memory, or their ability to recall the last words they heard. Compared to the group of people who received the sham stimulation or placebo, those who received the treatments saw results that “translated into older people recalling, on average, four to six more words from the 20-word list by end of the 4-day intervention,” said study co-author Robert Reinhart, director of the Cognitive & Clinical Neuroscience Laboratory at Boston University. “It is important to emphasize that the study mainly shows a modest but significant improvement in short-term memory, but does not show clear effects in long-term memory, as the test was based on word recall only about a minute after learning the words. Tanzi said. “Cognitive experts would say that what you remember an hour ago is long-term memory,” Tanzi added. “But in terms of the clinical symptoms of Alzheimer’s and age-related memory decline, we’ll group them under short-term memory. When we say Alzheimer’s patients retain long-term memory, we’re referring to recalling details of their wedding day.”
Personalized treatment
The study found that reversing the brain regions that received theta and gamma stimulation in a second experiment did not produce benefits. A third experiment with 30 people was done to verify the previous results.
One month after the intervention, the participants were asked to take 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, while higher-frequency gamma stimulation did not. The opposite was true for longer-term memories — gamma, but not theta, improved performance.
“Based on the spatial location and frequency of electrical stimulation, we can improve either short-term or long-term memory separately,” explained Reinhart, an assistant professor in Boston University’s department of psychological and brain sciences.
That means researchers can tailor treatment to an individual’s needs, Reinhart said.
How would that be? The devices are well tolerated, with little 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 on the aging brain.
“Currently, these treatments are difficult to obtain as specialized equipment is required. It can also be time-consuming and expensive,” Isaacson added. “Still, there are limited treatment options for cognitive aging, which affects tens of millions of people, so this is a hopeful step toward addressing symptoms and improving brain health.”
