LISTENING to low-pitched noise seems to induce high-speed brainwaves that break down protein plaques in the brain linked with Alzheimer’s. The approach has had promising results in mice and is now being tested in people with the condition.
Brainwaves are the result of large networks of brain cells firing rhythmically and in synchrony. Much about their function is unclear, but measuring these waves via electrodes on the scalp tells us that their frequency tends to reflect how awake and alert we feel.
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Brainwaves are slowest during deep sleep, and faster when we’re awake and relaxed. The fastest brainwaves are called gamma waves, and they cycle at around 40 times a second, or 40 hertz, when we are concentrating, making decisions and using our memory.
People with Alzheimer’s disease often produce fewer gamma waves, prompting researchers to experiment with ways of inducing this type of brain activity. Last year, group at the Massachusetts Institute of Technology showed that exposing mice to a light flickering at a frequency of 40 hertz induces gamma waves in the part of the brain that processes information from the eyes, the visual cortex.
When they tried the light treatment for 1 hour a day in mice genetically altered to develop Alzheimer’s-like symptoms, they found that this reduced deposits of amyloid and tau proteins – key features of Alzheimer’s disease.
The flickering light seemed to be boosting the activity of the brain’s immune cells, which can break down proteins like amyloid. But this effect was apparently confined to the brain’s visual cortex, leaving the crucial memory region unaffected. This area, called the hippocampus, is among the first regions of the brain to be affected by amyloid plaques (see picture).
“Mice played frequencies near the lowest E on a piano had half as many amyloid plaques”
Now it looks as if sound is a more promising therapy. For an hour a day, Tsai’s team played mice a 40 hertz noise, which is similar to the lowest E on a standard piano. When slices of brain were then viewed under a microscope, there were about half as many amyloid plaques in both the auditory cortex regions, where sound is processed, and the hippocampus, as were seen in control mice, the team found.
The effect of 40 hertz frequencies may spread more easily to the hippocampus when induced by sound, because these areas are closer to the auditory cortex than the visual cortex.
Alternatively, the pathways linking the auditory cortex to the hippocampus could be more direct, involving fewer synapses – the gaps between neurons – says of MIT, who presented the team’s work at the Society for Neuroscience conference in Washington DC in November.
The findings are promising, says David Reynolds of the charity Alzheimer’s Research UK. But we can’t assume that people with Alzheimer’s will respond to the 40 hertz in the same way as the mice, he says.
Trying it right away
However, because gamma wave therapy seems relatively safe, it can be tried right away, without the years of animal testing that potential Alzheimer’s drugs usually undergo. Tsai’s spin-off company, , has already begun trialling a form of gamma wave therapy in people with Alzheimer’s.
The approach they are trying combines sound, light and vibration – all at 40 hertz. Flickering light, low sounds and vibrating pads placed on the hands are being tested together on 12 people with mild or moderate Alzheimer’s disease at a nursing home in Boston. There is no placebo group, but the firm is planning a larger, placebo-controlled trial.
Some people are already trying the therapy for themselves, however. Since the team’s first results were announced last year, lamps that flicker at 40 hertz have been marketed as a dementia treatment, and several websites play a 40 hertz sound on loop.
Reynolds says, though, that families shouldn’t get their hopes up just yet, because Alzheimer’s in mice is different from the human disease. However, tests should show if it works in humans too. “Listening to a noise is an entirely doable kind of therapy,” he says.
This article appeared in print under the headline “Brainwave therapy for Alzheimer’s”
