Non-invasive treatment improves memory and reduces amyloid plaques in mice – ScienceDaily

This non-invasive treatment, which acts by inducing brain waves known as gamma oscillations, has also significantly reduced the number of amyloid plaques found in the brains of these mice. Plates have been cleaned in large areas of the brain, including areas critical to cognitive functions such as learning and memory.

"When we badociate visual and auditory stimulation for a week, we find commitment to the prefrontal cortex and a very dramatic reduction in amyloid," said Li-Huei Tsai, director of the Picower Institute for learning and memory at MIT. study.

According to her, further studies will be needed to determine if this type of treatment will work in humans. Researchers have already conducted preliminary safety tests for this type of stimulation in healthy subjects.

Anthony Martorell, a graduate student at MIT, and Abigail Paulson, graduate student at Georgia Tech, are the lead authors of the study, which appears in the March 14 issue of Cell.

Improved memory

Brain neurons generate electrical signals that synchronize to form brain waves in different frequency ranges. Previous studies have suggested that patients with Alzheimer's disease have impaired gamma-frequency oscillations between 25 and 80 hertz (cycles per second), and that they would contribute to brain function such as attention, perception and memory.

In 2016, Tsai and his colleagues first reported the beneficial effects of restoring gamma oscillations in the brains of mice genetically predisposed to the development of Alzheimer 's symptoms. In this study, researchers used a slight flicker at 40 hertz, delivered one hour a day. They discovered that this treatment reduced levels of beta-amyloid plaques and another pathogen marker linked to Alzheimer's disease, the phosphorylated tau protein. The treatment also boosted the activity of immune cells removing debris, called microglia.

In this study, the improvements generated by the flickering light were limited to the visual cortex. In their new study, researchers sought to determine whether they could reach other areas of the brain, such as those needed for learning and memory, using sound stimuli. They found that exposure to one hour of 40 Hz sounds per day for seven days significantly reduced the amount of beta-amyloid in the auditory cortex (which treats the sound) as well as in the hippocampus, a Key memory site located near the auditory cortex.

"What we have demonstrated here is that we can use a totally different sensory modality to induce gamma oscillations in the brain, and secondly, this gamma induced by auditory stimulation can reduce the pathology of the brain." Amyloid and Tau in the sensory cortex, but also in the human body, hippocampus, "says Tsai, a founding member of the MIT Brain Aging Initiative.

The researchers also tested the effect of auditory stimulation on the cognitive abilities of mice. They found that after a week of treatment, the mice got much better results when they navigated through a labyrinth, forcing them to remember important landmarks. They were also better able to recognize the objects they had encountered before.

They also found that auditory processing induced changes not only in microglia, but also blood vessels, thus facilitating clearance of amyloid.

Dramatic effect

The researchers then decided to try to combine the visual and auditory stimulations and, to their surprise, they found that this double treatment had an even greater effect than one or the other. Amyloid plaques have been reduced in a larger part of the brain, including in the prefrontal cortex, where higher cognitive functions occur. The response of microglia was also much stronger.

"These microglia are superimposed around the plates," says Tsai. "It's very dramatic."

The researchers found that if they treated the mice for one week and then waited another week for the tests, many positive effects faded, suggesting that the treatment should be administered continuously to maintain advantages.

In an ongoing study, researchers are currently badyzing how gamma oscillations affect certain types of brain cells, in the hope of discovering the molecular mechanisms underlying the phenomena they observed. Tsai said that she also hoped to explore why the specific frequency used, 40 hertz, had such a profound impact.

Combined visual and auditory treatments have already been tested on healthy volunteers to evaluate its safety. Researchers are now starting to recruit patients with early-stage Alzheimer's disease to study its possible effects on the disease.

The research was funded in part by the Robert and Renee Belfer Family Foundation, the Halis Family Foundation, the JPB Foundation, the National Institutes of Health, and the MIT Aging Brain Initiative.