THE SCIENCE SO FAR
It has been known since at least the 1980s that cognitive activity triggers brainwaves (wave-like patterns of activation) at a frequency of 40 Hz in humans and other mammals.
In 1991, researchers from the NYU Medical Center discovered that Alzheimer’s patients have reduced 40 Hz brainwaves compared with healthy people. (paywalled paper)
In 2016, MIT’s Alzheimer’s group did experiments on transgenic mice with early Alzheimer’s disease and found that exposing them to a light flickering at a frequency of 40 Hz (40 times a second) for 1 hour a day for 7 days causes an almost 60% reduction in β-amyloid plaques, which are a molecular hallmark of Alzheimer’s. Flickering at 20 Hz and 80 Hz did not have the same effect. An important qualification here is that the effect was limited to the visual cortex, which is not significantly affected in human Alzheimer’s patients. Here’s an accessibly written report in The Atlantic and here’s the original paper (published in Nature) if you’re strong in science-speak. MIT also made a video about the findings.
In March 2016, scientists at the University of Toronto published the results of a small, placebo-controlled pilot study (paywalled paper), in which they exposed 20 Alzheimer’s patients to a 40 Hz sound. After six 30-minute sessions (done twice a week), the patients’ average score on the 30-point SLUMS scale improved by 4 points, while the placebo group did not improve. It should be noted that the “dosage” of the treatment was rather low, which may explain the modest results.
In January 2017, Cognito Therapeutics, a company formed by some of the members of the MIT team, started conducting preliminary trials to assess the safety of exposing AD patients to simultaneous flickering lights, an audio tone, and vibrations – all at 40 hertz.
In January 2018, the New Scientist reported (paywalled article) that the same MIT team achieved even better results by playing mice a 40 Hz sound. β-amyloid plaques shrank by about 50% in the auditory cortex and – crucially – in the hippocampus, perhaps because the two areas are close to each other. This would be a very important discovery, because the hippocampus is the region of the brain which is involved in forming memories. It is the hippocampus that suffers the most damage in human Alzheimer’s patients. According to the magazine, these results were presented at the Society for Neuroscience conference in Washington in November 2017. However, the published paper described a significantly different protocol (see below), so it is likely that the New Scientist didn’t get the details right.
In July 2018, the International Journal of Alzheimer’s Disease published the results of a pilot study in which 6 human patients were exposed to a 40-hertz flickering light bulb for 2 hours a day for 10 days. The therapy was administered in a home setting by the patients’ caregivers. No difference in β-amyloid plaque was found after therapy. If there was an effect, it must have been smaller than 20%, which is not comparable to the 50% reduction seen in mice.
In March 2019, Cell published another (paywalled) paper about another study done by the MIT group. Here’s a NYT article about it. Here are the main points:
After mice were exposed (for 7 days, 1 hour a day) to a series of clicks repeating at a frequency of 40 Hz, the amount of amyloid plaque in their auditory cortex and their hippocampus was reduced by about 40%. The mice also did better on several tasks involving the use of memory.
When this auditory treatment was combined with light pulses at 40 Hz, microglia (“brain cleaner cells”) started clustering around amyloid plaque, and the reductions in plaque extended to parts of the prefrontal cortex (an area related to functions like attention and short-term memory). This effect was not observed with either audio or light treatment alone.
In 2018, Cognito Therapeutics started three clinical trials of their device (called “GammaSense”) that combines visual and auditory stimulation. The device is essentially LED goggles with over-the-ear headphones.
[NEW] In 2019, Dr Tsai’s MIT group started two small trials of another device – a white screen illuminated with LEDs flashing at 40 Hz combined with a soundbar emitting a 40 Hz “buzzing” or “humming” sound. Here is a summary of Dr Tsai’s presentation on it and here are the pages for the two trials on ClinicalTrials.gov.
[NEW] In April 2021 at the AD/PD conference, Cognito presented preliminary results of the GammaSense trials, most notably, the Overture trial (news story from NJ.com), which is designed to evaluate efficacy. 46 patients with Alzheimer’s Disease received a daily 60-minute session with the GammaSense device for a period of 6 months. The control group comprised 28 patients who received sham treatment (i.e. a placebo-like device that isn’t supposed to do anything).
https://blog.szynalski.com/2018/03/40...
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