November 29, 2022

Study offers hope for potential Alzheimer’s treatment

Read Time:7 Minute, 50 Second

(CNN) — Want some non-invasive brain stimulation to boost your memory for that next big project, work meeting, or family get-together? Science may one day offer such treatments, new research suggests.

According to a study conducted by a team from Boston University and published this Monday in the academic journal Nature Neurosciencesending electrical currents to two parts of the brain known for their ability to store and recall information modestly increased immediate word recall in people over the age of 65.

“Whether these improvements occur in everyday memories and not just word lists remains to be seen,” Masud Husain, a professor of neurology and cognitive neuroscience at the University of Oxford, said in a statement. Husain was not part of the study.

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

The improvements were most 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 those 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 such as Alzheimer’s disease,” he added.

Drive brain change

Scientists used to think that after a certain point in adulthood the brain was fixed, unable to grow or change. It is now known 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 function with a device that delivers wave-shaped electrical currents to specific areas of the brain through electrodes on the scalp. The electrical waves can mimic or change brain wave activity to stimulate growth and hopefully change the brain’s neural network.

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

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

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

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

“The consequence of changing the activation times of brain cells is that this plasticity process is induced. Plasticity is what allows the effects to be prolonged in time even when the stimulation has already ended,” he added.

memories fade

As the brain ages, it is common to lose some of the ability to remember. For some people, short-term memory suffers the most: where did I park the car in the mall on this shopping trip? Others may have trouble remembering things for a longer period of time: where did I park the car two weeks ago before I boarded the plane for vacation? And some have problems with both types of memory.

The Boston University researchers looked separately at long-term memory and short-term or working memory in two experiments, each involving randomized groups of 20 people aged 65 to 88.

The experiments alternated the application of gamma waves at 60 hertz and theta waves at 4 hertz to two brain centers that play key roles in memory.

Gamma waves are the shortest and fastest of the brainwave frequencies, and they operate between 30 and 80 hertz, or cycles per second. Some so-called “high gamma” brain waves have been recorded up to 100 hertz.

The brain receives intense stimulation with gamma waves. Stressed people who need to concentrate intensely, for example when taking an exam, solving a complex problem, or fixing a difficult mechanical problem, can produce gamma waves.

Theta waves are much slower, ranging between four and eight cycles per second. When you’re in theta mode, you’re probably on autopilot: driving to work without thinking about the route, brushing your teeth or hair, even daydreaming. It’s often when people ponder an idea or come up with a solution to a problem. The studies have found that theta activity can predict learning success.

Target the memory areas of the brain

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

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

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

Sessions were held for four consecutive days. Each person performed five 20-word recall tests during daily 20-minute stimulation. They were asked to immediately recall as many words as they could at the end of each of the five trials.

The research team assessed performance in two ways: How well did the participants remember the words at the bottom of the list, which they had just heard? That would be the measure of short-term or working memory. How many words could they remember from the beginning of each list that would have been heard minutes ago?

That result would assess the ability to remember over a somewhat longer period of time.

The results showed that 17 of the 20 people who received high-frequency gamma stimulation improved their ability to remember words from the beginning of the test, which the researchers called long-term memory.

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

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

“Importantly, the study mainly shows a modest but significant improvement in short-term memory, but shows no clear effect on long-term memory, as the test was based on word recall for only about a minute, after learning the words,” Tanzi said.

“Cognitive experts would say that what is remembered from an hour ago is long-term memory,” Tanzi added. “But when it comes to clinical symptoms of Alzheimer’s and age-related memory decline, we would lump it under short-term memory. When we say that Alzheimer’s patients retain long-term memory, we mean remembering details of the their wedding day.”

Symptoms of Alzheimer’s or signs of aging? 3:32

personalized treatment

The study found that changing the brain areas that received theta and gamma stimulation in a second experiment produced no benefit. A third experiment was carried out with 30 people 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 were long-lasting.

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.

“Depending on the spatial location and frequency of electrical stimulation, we can improve either short-term memory or long-term memory separately,” explained Reinhart, an associate professor in the department of brain and psychological sciences at Boston University.

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

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

“In an ideal world, the ultimate goal would be to have a portable device for the home that could deliver this therapy,” said Isaacson, administrator of the McKnight Foundation for Brain Researchwhich funds research on the aging brain.

“For now, it’s cumbersome to get these treatments because you need specialized equipment. Plus, it can be time-consuming and expensive,” adds Isaacson. “Still, treatment options for cognitive aging, which affects tens of millions of people, are limited, so this is a hopeful step toward addressing symptoms and improving brain health.”

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