Noninvasive treatment improves memory and reduces amyloid plaques in mice — ScienceDaily

Neuroscientists at the Massachusetts Institute of Technology have demonstrated that they can improve cognitive and memory impairment similar to those with Alzheimer's disease by exposing mice to unique light and sound combinations.

This non-invasive treatment works by inducing brain waves called gamma oscillations, and also greatly reduces the number of amyloid plaques found in the brains of these mice. Plaques are removed from large areas of the brain, including areas critical to cognitive functions such as learning and memory.

"When we combine visual and auditory stimuli for a week, we see the involvement of the prefrontal cortex and the dramatic reduction of amyloid," said Li-Huei, director and senior student of the Institute of Learning and Memory at the Massachusetts Institute of Technology. Tsai said. The author of the study.

She said that further research is needed to determine whether this treatment is applicable to human patients. Researchers have conducted some preliminary safety tests for this type of stimulation in healthy human subjects.

Anthony Martorell, a graduate student at the Massachusetts Institute of Technology, and Abigail Paulson, a graduate student at the Georgia Institute of Technology, are the lead authors of the study, published in the March 19th issue of Cell .

Improved Memory

The electrical signals produced by neurons in the brain synchronously form brain waves in several different frequency ranges. Previous studies have shown that patients with Alzheimer's disease have impaired gamma frequency oscillations ranging from 25 to 80 Hz (cycles per second) and are thought to contribute to brain function such as attention, perception and memory.

In 2016, Tsai and her colleagues reported for the first time the beneficial effects of restoring gamma oscillations in the brains of mice that are genetically predisposed to symptoms of Alzheimer's disease. In that study, the researchers used a slight flash of 40 Hz to deliver an hour a day. They found that this treatment can reduce the level of phosphorylated tau protein in beta amyloid plaques and another pathogen associated with Alzheimer's disease. This treatment also stimulates the activity of immune cells called debris-cleaving debris.

In that study, the improvement produced by scintillation light was limited to the visual cortex. In their new study, researchers began to explore whether sound can be used to reach other brain regions, such as the brain regions needed for learning and memory. They found that exposure to a 1 hour 40 Hz tone per day for 7 days greatly reduced the amount of beta amyloid in the auditory cortex (the treated sound) and the hippocampus located in the key memory area nearby. Hearing cortex.

"What we show here is that we can use completely different sensory patterns to induce gamma oscillations in the brain. Second, this auditory stimulus-induced gamma can not only reduce amyloid and Tau pathology in the sensory cortex. Also in the hippocampus," Tsai said, a founding member of the MIT Ageing Brain Initiative.

The researchers also tested the effects of auditory stimulation on cognitive performance in mice. They found that after a week of treatment, the mice performed much better when navigating the maze, asking them to remember the key landmarks. They can also better identify the objects they have encountered before.

They also found that auditory therapy not only causes changes in microglia, but also causes changes in blood vessels that may promote amyloid clearance.

Theatrical effect

The researchers then decided to try to combine visual and auditory stimuli, and to their surprise, they found that this dual treatment had a greater impact than either alone. Amyloid plaques are reduced in a larger part of the brain, including the prefrontal cortex, where higher cognitive function occurs. The reaction of microglia is also stronger.

"These microglia are just stacked around the plaque," Tsai said. "This is very eye-catching."

The researchers found that if they treated the mice for a week and then waited a week for testing, many of the positive effects had subsided, suggesting that treatment is needed to maintain their benefits.

In an ongoing study, researchers are analyzing how gamma oscillations affect specific brain cell types, hoping to discover the molecular mechanisms behind the phenomena they observe. Cai said she also wants to explore why the specific frequency they use, 40 Hz, has such far-reaching effects.

Joint vision and auditory therapy have been tested in healthy volunteers to assess their safety, and researchers are now recruiting patients with early Alzheimer's disease to study their possible effects on the disease. .

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

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