Novel Sound and Light Therapy for Alzheimer's Disease

Novel Sound and Light Therapy for Alzheimer's Disease

Alzheimer's disease is the most prevalent neurodegenerative disease in the world. Its pathological features are the accumulation of beta amyloid fragments and tau fragments, and patients often show a decline in cognitive ability. Although this disease has a major impact on humans, the journey of finding a cure to it through new drug research and development is very difficult. According to statistics, between 1998 and 2017, 146 attempts to develop new drugs for Alzheimer's disease failed. In the past 20 years, only 4 drugs have been successfully approved for the treatment of Alzheimer's disease. That is to say, the ratio of success to failure is 1:37!

Against this backdrop, scientists began to reflect on whether there is a bias in our understanding of the cause of Alzheimer's disease. For example, a recent popular opinion is that the deposition of amyloid beta is not a "cause" but a "result." It is more like the traces left by the brain's immune system against infection. Coincidentally, many studies have linked viral infections, bacterial infections to Alzheimer's disease, trying to interpret this disease from a new perspective.

Recently, an interesting finding was published in Cell. The team of Professor Cai Lihui from the Massachusetts Institute of Technology (MIT) found that it may be possible to use a light and sound therapy with a specifical frequency to treat Alzheimer's disease. In mouse experiments, the researchers not only reduced the pathological features of the disease, but also improved the cognitive ability of the mice.

This is not the widest imagination of scientists. In fact, Professor Cai Lihui's team has worked hard for many years in the field of Alzheimer's disease. In December 2016, her team published a research paper in Nature, which found that 40 Hz of light per second can stimulate brain gamma brain waves and reduce beta amyloid fragments (or protein) in mouse brain.

Although the results of this study are interesting, the practical value is very limited. This is because in the mouse brain, only the "visual center" of amyloid beta is reduced, but the visual center is not a key area for the progression of Alzheimer's disease. If there is any way to influence the hippocampus that controls memory, the potential of this light therapy to humans will be greater.

This is exactly the breakthrough brought by Professor Cai Lihui's team. The researchers found that a 40 Hz sound can also stimulate gamma brain waves in the brain. But unlike light, these sounds not only affect the "auditory center," but also the key CA1 sites in the hippocampus, as well as the medial prefrontal cortex (mPFC). These results suggest that "sound therapy" may improve neurological activity in the hippocampus.

This idea was validated in the mouse experiment. In a 6-month-old mouse model of Alzheimer's disease, the researchers evaluated the effects of "sound therapy." The experiment found that after 7 days of treatment, the mice in the "40 Hz" group improved their object recognition ability and spatial recognition ability, reflecting their enhanced cognitive ability. In contrast, mice that did not receive sound stimulation or were stimulated by random frequency sounds had no change in cognitive ability.

Behind the improvement in cognitive ability, the mouse's brain has also changed. The researchers found that this "sound therapy" can reduce beta amyloid in the auditory center and hippocampus in a mouse model. At the same time, the number of microglia that exercise phagocytosis in the brain has increased, and the diameter of blood vessels in the brain has also increased. These findings suggest that it is possible for the brain to clear beta amyloid by these mechanisms.

Interestingly, when the 40 Hz sound is used in conjunction with light, it seems to have a better effect in stimulating microglia response and scavenging beta amyloid. Microglia are stacked around beta amyloid, as revealed by Professor Cai Lihui.

But as to why the 40 Hz sound stimulus has such a wide impact, it still remains an unresolved issue.

It should be noted that the results observed in this study were based on genetically edited mouse models. Whether this sound and light therapy will also work in the human body is still unsure. If it is proven to be safe and effective, it will undoubtedly change the treatment of Alzheimer's disease.

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