LISTENING to low-pitched noise seems to induce high-speed brainwaves that break down protein plaques in the brain linked with Alzheimer鈥檚. 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鈥檙e 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鈥檚 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鈥檚-like symptoms, they found that this reduced deposits of amyloid and tau proteins 鈥� key features of Alzheimer鈥檚 disease.
The flickering light seemed to be boosting the activity of the brain鈥檚 immune cells, which can break down proteins like amyloid. But this effect was apparently confined to the brain鈥檚 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).
鈥淢ice played frequencies near the lowest E on a piano had half as many amyloid plaques鈥�
Now it looks as if sound is a more promising therapy. For an hour a day, Tsai鈥檚 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 鈥� the gaps between neurons 鈥� says of MIT, who presented the team鈥檚 work at the Society for Neuroscience conference in Washington DC in November.
The findings are promising, says David Reynolds of the charity Alzheimer鈥檚 Research UK. But we can鈥檛 assume that people with Alzheimer鈥檚 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鈥檚 drugs usually undergo. Tsai鈥檚 spin-off company, , has already begun trialling a form of gamma wave therapy in people with Alzheimer鈥檚.
The approach they are trying combines sound, light and vibration 鈥� 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鈥檚 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鈥檚 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鈥檛 get their hopes up just yet, because Alzheimer鈥檚 in mice is different from the human disease. However, tests should show if it works in humans too. 鈥淟istening to a noise is an entirely doable kind of therapy,鈥� he says.
This article appeared in print under the headline 鈥淏rainwave therapy for Alzheimer鈥檚鈥�
