Alzheimer's PSA: 40Hz is not 40Hz!
There’s a great new Alzheimer’s therapy...
but everyone is doing it wrong!
My mom called me yesterday, worried about a brain scan she got back.
She’s fine for now, but the risk of Alzheimer’s is real. Did I know of anything new?
I was just reading up on a very promising therapy for Alzheimer’s, simple enough to homebrew. Perfect, why not try it out?
This work was done by a great lab and is hot news in the field (links at end). Human testing is not yet completed, but it seems like a good idea to just do it anyway, given the results in mice and the simplicity and harmlessness of the therapy.
What is it? Basically, flashing lights or sounds (or both) at a particular speed—40Hz.
Studies showed improvement after an hour per day for a week, even with just sound!
So, instead of making my own 40Hz sound, I just went on YouTube. The therapy was such big news I was sure other people would have posted something I could send my mom.
To my horror, I found that almost everything on YouTube is wrong.
There are a ton of homebrewed ‘40Hz sound therapy’ videos, and the vast majority get it wrong. Certainly enough are wrong that trying to find the right thing is hard, and near impossible if you don’t know what you’re looking for.
Here is the mistake everyone makes: Researchers reported using ‘40Hz auditory stimulation’, and most people interpret that as ‘40Hz tone’. These things are not the same!
The tone sounds like a low bass note (you’ll probably need good headphones to hear it at all), and this is mostly what appears on YouTube as ‘Alzheimer’s therapy’. But the click train—the thing actually shown to help Alzheimer’s—sounds more like buzzing bees .
Listen to the difference: 40Hz tone / 40Hz clicks
These are two very different things, and produce very different activity in the brain!
For example, at the first stage of auditory processing, the click-train gets a response from all regions of the cochlea (the ear’s retina), while the tone will not:
And as the signal travels up to cortex this difference in activity will be reflected at all levels of the ascending auditory system: The tone will only evoke activity in a limited neural population, while the clicks will evoke 40Hz modulation in a wide neural population regardless of preferred tone-frequency. In terms of neural processing, this matters a lot.
Nobody is sounding the alarm that people rightly excited about this truly promising therapy may be wasting their time, when they could be doing it right.
If anyone in your life is, or should be, using this kind of therapy, please let them know: The correct type of audio for 40Hz Alzheimer’s therapy should sound like buzzing bees, not like a low tone, even though the latter is much more common online.
A final note: Why sound not light? A standard computer monitor’s refresh rate of 60Hz can’t accurately deliver light therapy at 40Hz. But studies showed sound alone works, and therapy through just your ears lets you do other things at the same time.
Kevin J.P. Woods, Ph.D.