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A brain scientist from the BU shows that electrostimulation can restore the working memory of a 70-year-old man to that of a 20-year-old man.
During memory tasks, the brain activity associated with working memory lights up in the brain of a 20-year-old man (left), but remains dormant in the brain of the brain. a 70 year old (in the center). After electrostimulation (right), the brain activity of 70 years is similar to that of 20 years. Credit: Reinhart lab / Boston University
By reading the words that extend on this page, your brain is doing something beautiful. Each sentence stays in your mind for a fleeting moment, the letters blending into a symphony of neural signals. These complex electrical rhythms form the language of the brain, language that we have only begun to understand in the last century.
Rob Reinhart, an assistant professor of psychological and cerebral sciences at Boston University, says that we have reached a point where we do not only understand this language, we can speak it and use it to improve the functioning of the mind. . In an innovative study published in April 2019 in Nature NeuroscienceReinhart demonstrates that electrostimulation can improve the working memory of 70-year-olds, so their performance in memory tasks can not be distinguished from those of 20-year-olds.
Reinhart's research targets working memory – the part of the mind where the consciousness lives, the active part every time we make decisions, reason, recall our grocery lists and (hopefully) remember where we have left our keys. Working memory begins to decline in the late twenties and early thirties, he explains, as some areas of the brain become progressively disconnected and poorly coordinated. By the time we reach our 60s and 70s, these neural circuits have deteriorated enough that many of us have significant cognitive difficulties, even in the absence of dementia such as Alzheimer's disease.
But Reinhart has discovered something incredible: by using electrical currents to noninvasively stimulate areas of the brain that have lost their rhythm, we can dramatically improve the performance of working memory.
During the study, funded by a grant from the National Institutes of Health, he asked a group of people in their twenties and a group of 60 and 70-year-olds to perform a series of memory tasks that required them to view an image. after a brief pause, to determine if a second image was slightly different from the original.
Initially, young adults were much more specific in this respect, considerably exceeding the older group. However, when the elderly received 25 minutes of soft stimulation delivered by scalp electrodes and customized according to their own brain circuits, the difference between the two groups disappeared. Even more encouraging? This increase in memory lasted at least until the end of the 50-minute period following the stimulation, at which point the experiment ended.
To understand why this technique is so effective, we need to look at the two mechanisms that allow the working memory to function properly: coupling and synchronization.
Coupling occurs when different types of brain rhythms coordinate, which helps us to process and store working memories. Slow and low-frequency rhythms – theta rhythms – dance in front of your brain, acting as orchestra conductors. They join faster, high-frequency rhythms called gamma, which are generated in the region of the brain that processes the world around us.
Just like a musical band contains flutes, oboes, violins, the gamma rhythms that reside in your brain each contribute to something unique in the orchestra at the electricity that creates your memories. For example, a gamma rhythm can process the color of an object that you keep in your mind, while another captures its shape, another its orientation, and another sound.
But when orchestra conductors pummel with their batons – when theta rhythms lose the ability to connect to these gamma rhythms to monitor, nurture and educate them – the melodies in the brain begin to disintegrate and our memories lose their acuity.
Meanwhile, synchronization – when the theta rhythms of different areas of the brain synchronize – allows separate areas of the brain to communicate with each other. This process serves as a glue for a memory, combining individual sensory details to create a coherent memory. As we age, our theta rhythms become less synchronized and the fabric of our memories begins to fray.
Reinhart's study suggests that by using electrical stimulation, we can restore these pathways that tend to spoil with age, improving our ability to recall our experiences by restoring the flow of information in the brain. And it is not only older adults who will benefit from this technique: it is also promising for the youngest.
In his study, 14 of the young adult participants did poor memory tasks despite their age – so he called them back to stimulate their brains as well.
"We have shown that the underperforming, much younger and in their twenties, could also benefit from the same kind of stimulation," says Reinhart. "We could improve their working memory even if they were not in their sixties or seventies."
Coupling and synchronization, he adds, exist on a continuum: "It's not as if there are people who are not in a relationship as opposed to people who are in a relationship."
At one end of the spectrum, a person with incredible memory can be excellent for synchronization and coupling, while someone with Alzheimer's would probably have a hard time living with both. Others lie between these two extremes – for example, you might be a weak coupler but a powerful synchronizer, or vice versa.
And when we use this stimulation to modify neuronal symphonies, we're not just doing a small minor adjustment, says Reinhart. "It's behaviorally relevant. Now, [people are] perform tasks differently, they remember things better, they perceive better, they learn faster. It's really extraordinary. "
In the future, he plans various future applications for his work.
"This opens a new avenue for potential research and treatment options," he says, "and we are very excited about it."
Reinhart would like to study the effects of electrostimulation on individual brain cells by applying it to animal models. It is curious to know how repeated doses of stimulation could strengthen the brain circuits in humans. Most importantly, he hopes that his discovery will one day lead to treatment for the millions of people in the world with cognitive disabilities, especially those with Alzheimer's disease.
He loves his work as a neuroscientist, especially when he leads to breakthroughs like this one. "It's wild," he adds, a smile in his voice. "It is wild to think that we can target the electricity of a brain circuit in the same way that we would target a chemical neurotransmitter in the brain."
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