linearb,
I couldn't tell from watching the video, how the stimulation is applied. She mentioned an IPhone app and then oddly, a separate device has been built.
I think she was speculating that eventually this could be done with an app, though you'd still need electrodes -- less sure how that would work. I know that their prototype device is built around an Aurdino, and has a headphone output as well as 2 electrodes, think of a TENS machine but
much lower voltage, you are barely aware that it's on.
Do you know if the bi-modal stimulus to desensitize neurons responsible for tinnitus...subjection to stimulus for a couple of hours....is the stimulus sound?...or electrical stimulus to parts of the body near the brain?
They mentioned they have already built a device with pending patents.
Can you shed any further light?
Thanks
I am not a neurologist; I'm a compsci guy and not an especially brilliant one at that. But, I learned as much about this as I could, given that I did significant travel to and from Michigan to be part of the study. Here is my understanding:
* sound signals from the ear travel down the auditory nerve into the brain near the brainstem. The auditory nerve inserts directly into the dorsal cochlear nucleus (DCN), so sound data goes through that structure before it gets to the auditory cortex which is further into the brain.
* sensory information from touch-sensing neurons in the face/jaw also travel through the DCN. So, the DCN is the first place that these different signals are "integrated"
* Witnessed in animal studies: when you subject an animal to an ear-damaging loud noise, the signal strength from the auditory nerve going IN to the DCN is reduced. However, the signal coming OUT of the DCN is
not reduced. Therefore, there is some kind of "auditory gain" happening in the DCN to compensate for the signal loss.
* Also from animal studies: prior to a noise trauma, the DCN has some ratio of auditory-sensing neurons and touch sensing neurons. Lets say it's 50/50, just to make it easy. After the noise trauma, the number of auditory-sensing neurons decreases over the following weeks... and the number of touch-sensing neurons increases! So, they think this has something to do with the "gain" -- they think that touch-sensing data is "crossing over" into the auditory stream. This is why many/most people with tinnitus can modulate it by clenching the jaw or neck... it's not that those muscles are necessary tight or problematic, it's just that the data from those nerves has been cross-wired into the audio, so you are "hearing" your muscles. Note that this treatment will almost certainly
not work for anyone who cannot in any way modulate their tinnitus with muscle movements.
So, that's all pretty basis, as far as neurology goes. Now we get into stuff I barely comprehend:
there is a thing called
spike timing dependent plasticity. This is a general process by which the brain reorganizes itself, constantly. The theory is that this kind of plasticity is what causes the DCN to "misfire" and trigger tinnitus. (I use quotes because the brain is working exactly as it has evolved to do, it's just that in this case the result is distressing, or, at best, annoying to us).
What they have found is that if you stimulate the auditory nerve with a sound, and then also stimulate the muscles in that area with electricity at a
very very specific time offset from the sound (milliseconds, or even more fine-grained than that), it can impact that neuroplasticity, and hopefully reduce the extent to which muscle data is "heard".
So, that's how this is supposed to work. My understanding is that their belief is that this is
not, and will never be, a cure: someone using the device may not experience any benefit for a couple weeks. If they do experience a benefit, the effect is almost certain to wear off within a couple weeks of ceasing use of the device. So, this is a palliative, ongoing treatment -- and, of course, even if it works, no one knows if the effect stays stable for many months or years. The only human trial to date was only for 4 weeks.
Finally, given that this entire model is predicated on bimodal stimulation, it is a dead end for anyone who is deaf and/or has dead facial nerves.
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