Electrodeless Neuro-Interfaces
As of now, there are a lot of projects that use electrodes and indirect interfaces via magnets, or vibrators to supply data to the user. But there are a host of potential issues with these methods that I'd like to avoid. It's easy enough to read the current state of the brain via EEG. We can even use tDCS, TMS to change how our brains work without ever sticking an electrode below the skin. The question is, why can't we use a similar method to create a direct interface with a nerve, even if it isn't the brain?
Any thoughts on how this could be done with precision (not just slapping an electrode on the skin are running current between point A and B to stimulate a nerve)?
Any thoughts on how this could be done with precision (not just slapping an electrode on the skin are running current between point A and B to stimulate a nerve)?
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If you want to affect things from a greater distance, you give up specificity and increase energy required, both of which are extremely important in any neural interface.
Sincerely,
John Doe
"Because cutting a hole in the skull is kinda invasive." May I ask why you are using invasive electrodes? The only place I know for certain they are used is epilepsy research, that just caught my eye.
Does anyone know whether the voltage you introduce has a bigger impact on the strength of the signal you introduce into a nerve, or whether it's current?
Apparently they were able to cause nerves to fire using infrared, instead of electrical stimulation. Funny enough, Infrared also happens to include wavelengths as small as, and smaller than the smallest neurons found in humans. Near infrared also penetrates soft tissue, bone, and brain matter according to this. Another interesting article on the subject: Link.
Another issue is that this is only a unidirectional technology: communicating from a device to the brain. The hemodynamic response is too slow for any real neural interfacing (10s+ delay and not consistent). Cool paper and certainly not without application, but still invasive.
If spatial resolution is what you're talking about, couldn't you simply design a device that has an extremely high starting resolution, so that when your IR signals get scattered and absorbed by the tissue, the resolution is decreased to the minimum level needed for an effective neuro-interface? Or does the skin introduce a constant cap for the resolution you'll get?
Example:
Smallest neuron size: ~4 microns(micrometers)
Device Resolution: 2 microns(micrometers)
Resolution Loss: 2 microns per tissue-size unit.
Tissue thickness: 1 tissue-size unit
End Resolution: 4 microns
---- EDIT ----
I didn't think to use square micrometers when I first came up with the example, but now that I've thought about it, it would just make things more complicated if I had.
@TheGreyKnight A spatial resolution of a few millimeters is definitely enough for a working BCI. You can even get a BCI working with EEG, so the mm-range is definitely 'deep' enough. ECoG falls within the same range. Of course, it depends on what you want to do. You're probably not going to control a prosthetic arm with 7 degrees of freedom with minimal training, but doing something like moving a cursor is definitely doable with that type of resolution. I wonder why this EROS method isn't more widely used in research. Can't be that expensive, right? Is it susceptible to signal noise or does the signal easily get messed up with small head movements?
No, I don't know how to improve the SNR here.
Sincerely,
John Doe