Flashing Light, Sound Restore Memory in Alzheimer's Mice

An innovative light and sound stimulation therapy reduced the number of amyloid plaques found in the brains of laboratory mice with Alzheimer's disease, improving memory and cognitive function. Could an hour of light and sound a day keep Alzheimer's at bay in people?

Alzheimer's disease is a type of degenerative brain disease that causes memory loss and language problems. Over 5.8 million Americans are currently living with Alzheimer's disease, including one in 10 people age 65 or older, according to the Alzheimer's Association.

The disease is caused by the buildup of two proteins in the brain—amyloid beta and tau—that clump together to form plaques or neurofibrillary tangles that impair memory function.

The research was published March 14 in Cell.

The noninvasive treatment induces brain waves called gamma oscillations.

Alzheimer's patients have impairments in gamma-frequency oscillations. Although the exact function of these oscillations, which range from 25-90 hertz, is unknown, it's believed to contribute to attention perception and memory in the brain.

In 2016, Li-Huei Tsai, director of MIT's Picower Institute for Learning and Memory, and her team exposed laboratory mice that genetically predisposed to Alzheimer's disease to a light flickering at 40 hertz for one hour a day. They found that this treatment reduced the levels of tau and amyloid beta in visual cortex of the brain and stimulated the activity of debris-clearing immune cells.

For the current study, Tsai and her team sought to improve on these results. By adding sound stimuli, they hoped the treatment would be able to reach other brain regions.

They played a 40-hertz tone one hour a day for seven hours for laboratory mice predisposed to Alzheimer's disease. At the conclusion of the study, the mice had dramatically lowered levels of beta amyloid in the auditory cortex, which process sound, and the brain's memory center, the hippocampus.

The treated mice also displayed improvements in cognition when navigating a maze that required them to remember key landmarks.

Next, the researchers administered both light and sound together. This had an even greater effect than either one given alone. Amyloid plaques reduced throughout a greater part of the brain, including teh prefrontal cortex, where higher cognitive functions take place.

Preliminary safety tests for this type of brain stimulation have already been performed in healthy human subjects, although more research is needed to determine if the treatment will work in people with Alzheimer's disease.

"As our intervention is completely non-invasive, there is minimal safety concerns. We still need to conduct human trials to determine if this is effective," Tsai said.