Using LED lights flickering at a specific frequency, researchers have shown that they can substantially reduce the beta amyloid plaques seen in Alzheimer’s disease, in the visual cortex of mice.

This treatment appears to work by inducing brain waves known as gamma oscillations, which the researchers discovered help the brain suppress beta amyloid production and invigorate cells responsible for destroying the plaques.

Further research will be needed to determine if a similar approach could help Alzheimer’s patients, the researchers say. The study was published in Nature.

In a study of mice that were genetically programmed to develop Alzheimer’s but did not yet show any plaque accumulation or behavioral symptoms, the researchers found impaired gamma oscillations during patterns of activity that are essential for learning and memory while running a maze.

Next, the researchers stimulated gamma oscillations at 40 hertz in a brain region called the hippocampus, which is critical in memory formation and retrieval. These initial studies relied on a technique known as optogenetics, co-pioneered by Boyden, which allows scientists to control the activity of genetically modified neurons by shining light on them. Using this approach, the researchers stimulated certain brain cells known as interneurons, which then synchronize the gamma activity of excitatory neurons.

The researchers then began to wonder if less-invasive techniques might achieve the same effect. They came up with the idea of using an external stimulus — in this case, light — to drive gamma oscillations in the brain. The researchers built a simple device consisting of a strip of LEDs that can be programmed to flicker at different frequencies.

Using this device, the researchers found that an hour of exposure to light flickering at 40 hertz enhanced gamma oscillations and reduced beta amyloid levels by half in the visual cortex of mice in the very early stages of Alzheimer’s. However, the proteins returned to their original levels within 24 hours.

The researchers then investigated whether a longer course of treatment could reduce amyloid plaques in mice with more advanced accumulation of amyloid plaques. After treating the mice for an hour a day for seven days, both plaques and free-floating amyloid were markedly reduced. The researchers are now trying to determine how long these effects last.

Furthermore, the researchers found that gamma rhythms also reduced another hallmark of Alzheimer’s disease: the abnormally modified Tau protein, which can form tangles in the brain.

The researchers are now studying whether light can drive gamma oscillations in brain regions beyond the visual cortex, and preliminary data suggest that this is possible. They are also investigating whether the reduction in amyloid plaques has any effects on the behavioral symptoms of their Alzheimer’s mouse models, and whether this technique could affect other neurological disorders that involve impaired gamma oscillations.

Paper: “Gamma frequency entrainment attenuates amyloid load and modifies microglia”
Reprinted from materials provided by MIT.

március 9, 2017