[Neuro] Brain-Brain Interface with tDCS like stimulation

John Withers jwithers at reddagger.org
Tue Aug 6 04:37:01 UTC 2013


I think it depends on the context we are talking about. They both look 
sorta the same. But I think that view can easily gloss over the fact 
that these are fundamentally different technologies, both in presumed 
mechanisms of action and in practice.

And in the caveat area, I have used and experimented with TDCS pretty 
extensively, built out units, and actively consult with companies on 
this. However, I have never touched an ultrasound device (so many fun 
things in neuro bioengineering right now, so little time) and only 
follow the research the same as you.

TDCS only works at essentially the cortical surface. There are some 
claims of a magic AC stimulation device that presumably goes deeper 
safely, but I along with a lot of people find this a questionable claim 
and the only papers on the Fischer device I have seen are authored by 
the guy who helped them build it out. Most likely these claims were 
simply for patent purposes to differentiate in an area with plenty of 
prior art.

Ultrasound can be targeted at deep brain structures.

You already hit on spatial resolution.

TDCS also won't fire neurons per se. It provides a comparatively weak 
bias to fire compared to ultrasound since ultrasound is apparently 
producing repeatable gross motor movement in response to stimulation.

And I do think it is important, if obvious, to really just keep in mind 
that these aren't really varieties of the same thing. To me this is like 
the fact that TDCS is showing very good preliminary results in helping 
alleviate the worst symptoms of some forms of depression. So do certain 
medications. There are different tradeoffs in both cases and we would 
never want to think of these two interventions in anything approaching 
the same way and wouldn't.

I think there is a lot more chance to make that mistake casually with 
two things that are both electronic black boxes to most folks, have some 
overlapping use cases, and both are about applying stimulation through 
the skull. Yet they have different mechanisms of action, capabilities 
and as time goes on we might find much different sets of dangers.


On 08/05/2013 02:14 PM, Grant Taylor wrote:
> Hey John, I agree with the majority of your post, but just wanted to 
> make two comments:
> First, in reference to Kevin's original question: from my 
> understanding (quick credentials: I have a PhD in applied experimental 
> psychology and have experience with various brain measurement 
> techniques, but have never actually used tDCS or FUS, so I wouldn't 
> consider myself an expert on these methods) I would say that focused 
> ultrasound is, in fact, quite similar to transcranial direct current 
> stimulation. Although the two methods use different mediums 
> (oscillating mechanical pressure from ultrasound vs. low-level 
> electrical stimulation from tDCS), they both have the same impact: 
> generalized excitation or inhibition of some localized brain region. 
> That is, they are both manipulating the firing threshold of the 
> neurons within a specific region. You are definitely correct that 
> neither phenomenon is very well understood in terms of exactly how 
> they cause this excitation/inhibition, so there are still many 
> questions to be answered, but from a practical standpoint they can 
> both be used for generally the same purposes, so I think that makes 
> them pretty similar. From what I can tell the biggest differences 
> between the two seems to be that tDCS is easier to implement, but FUS 
> has better spatial resolution (it can be used to manipulate more 
> specific brain regions than tDCS).
> For more information on FUS, see the section titled "Potential 
> mechanisms behind the observed neuromodulation" in this paper by the 
> same lead author: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3342684/
> Second, it's a bit off-topic, but you mentioned that the source was an 
> "odd publication", so I just wanted to mention that you are right, but 
> PLOS ONE is "odd" in a great way. PLOS ONE is an open-access journal, 
> so all of their published articles are available for free to everyone, 
> but they still maintain the same level of peer-reviewed scrutiny as 
> other reputable journals. This journal, and other similar open-access 
> publications, are leading the fight against the paywalls perpetuated 
> by traditional publishers, and have the potential to help disseminate 
> scientific findings to a much broader audience (here's a more detailed 
> explanation 
> <http://theconversation.com/the-great-publishing-swindle-the-high-price-of-academic-knowledge-6667>). 
> I think this movement is directly in line with the Noisebridge 
> philosophy, so I wanted to take this opportunity to spread their message.
> I definitely agree with your point about this just being an 
> attention-grabbing study. There's no real benefit in combining these 
> two technologies together, especially when we still know so little 
> about the individual components. This is an interesting technical 
> demonstration, not a scientific development.
> Sorry this ended up way longer than I anticipated. If you actually 
> read all of this, then congratulations! you must have a 
> longer-than-average attention span.
> -Grant
> On Sun, Aug 4, 2013 at 3:08 PM, John Withers <jwithers at reddagger.org 
> <mailto:jwithers at reddagger.org>> wrote:
>     On 08/04/2013 04:00 AM, Kevin Schiesser wrote:
>         Is focused ultrasound similar to transcranial direct current
>         stimulation?
>         See
>         http://www.plosone.org/article/info:doi/10.1371/journal.pone.0060410
>         for info on BBI.
>         __
>     Probably not. Neither phenomena is all that well understood (TDCS
>     only looks that way until you dig far enough down to get to the
>     "then the magic happens" part. We know what it does, but not
>     really why it should do that).
>     And this seems kinda an odd publication to me unless I am missing
>     something, which is possible.
>     Brain wave entrainment is a well understood phenomenon. Unless I
>     am deeply missing something here, that's all the trigger is. Look
>     at a strobe in a certain frequency range, certain of your
>     brainwaves tend to sync with it. This is the same thing that
>     Mitch's flashy glasses do. Hooking an eeg trigger to that isn't
>     breaking new ground. And it is enormously limited, it is a single
>     channel.
>     Ditto stimulating motor movement in mice using ultrasound techniques.
>     Putting both of them together to create "BCI" seems like nothing
>     but trying to make a sexy headline.
>     Although, it would be cool to do in a space just for the fun of
>     it, yeah.
>     j
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