transcranial magnetic stimulation (TMS) circuit model

[Jonathan Cline]

attached picture for the enjoyment of all.

approx 100 us pulse

RTFM

## Jonathan Cline
## jcl...@ieee.org
## Mobile: +1-805-617-0223
########################

[Kermit Henson]

does TMS work or is just another miracle cure? any review?

[John Griessen]

On 08/01/2016 01:19 AM, Jonathan Cline wrote:
> attached picture for the enjoyment of all.
>
> approx 100 us pulse
>
> RTFM

RTFM or ROTFL?

The stim suggested is a little strong...

[Nathan McCorkle]

On Mon, Aug 1, 2016 at 10:03 AM, John Griessen <jo...@industromatic.com> wrote:
> On 08/01/2016 01:19 AM, Jonathan Cline wrote:
>>
>> attached picture for the enjoyment of all.
>>
>> approx 100 us pulse
>>
>> RTFM
>
>
> RTFM or ROTFL?

I am also wondering the implication... what manual if 'RTFM'... even
the image posted looks cut-off and incomplete. I wonder if this is
some sick joke to influence endangerment of people who are not
cautious (or beginners).

[Brian Degger]

500v 1amp is dangerous and deadly.
Something seems very wrong with this circuit.

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[Raza]

Ignoring this particular circuit for a moment, TMS does work. It's become a pretty standard tool in the non-invasive neuroscience research toolkit.

What it does for a given stimulation protocol and target location on the scalp is a different question. Some options are pretty well validated, even have clinical trials behind them, but those encompass only a tiny fraction of the full range of possible protocols and answer an equally small fraction of the full range of behavioral questions we might have asked about the effects of those.

[Kermit Henson]

so, if there are clinical trials.. do you have the data?

homepathy also have clinical trials

i have been hearing about this lately, but i'm still waiting to see real data. I understund it can be hard since this is mainly applied to pain-relative diseases, which have a strong subjective evaluation component

also, how does it work? really dont understand how FDA approved such treatment unknowing the action mechanism. 

if there is no data, for me is just more snake oil

[Cathal (Phone)]

Of course it works: with enough current you can even put someone to sleep, permanently. That's a result, right? :)

More seriously though, if electroconvulsive therapy counts as TDS then it actually has a long history of efficaceous use.. for a handful of conditions. I have a feeling most people would consider TDS more narrowly focused, literally and figuratively, than ECT though.

I'm also aware of no double blind studies but would be interested to read. TDS is something I won't try until I see others living a long, healthy life after, but it's fascinating to watch.

--
Sent from my Android device with K-9 Mail. Please excuse my brevity.

[Raza]

No, look. TMS and tDCS are different things. Transcranial magnetic stimulation (TMS) is strong, spatially focused magnetism applied to superficial brain tissue through the skull; this isn't usually DIY'd, as it requires expensive and powerful equipment and is considered safe only when used with some expertise. Transcranial direct current stimulation (tDCS) is running a weak current through the skull, which diffuses across the total path of least resistance between the electrodes, passing through some obvious/predictable and a lot of non-obvious/poorly-predictable brain tissue in so doing; this one is often DIY'd, since the equipment is extremely affordable to put together, and when you stick within certain protocol parameters it is pretty generally safe-ish. ECT isn't generally considered part of the tDCS spectrum.

A fair bit is known about their mechanisms, but they're not so easily explained. The brief summary is that neurons are electrical signalling nodes that decide whether or not they fire based on currents passing through their membranes, and changing electrical or magnetic fields across the susceptible parts of these membranes will therefore change their firing behavior. When you have a lot of neurons that are aligned in the same direction, as in the important projecting neurons of the neocortex, changing a magnetic or electric field across all of them can have predictable effects. So when you can aim the current or magnetism at a piece of neocortex of which you (partially) know what it does, and that happens to be aligned so that you can hit it in the right direction with electrodes placed on the skull, you can make educated guesses at what the effects are going to be.

Mostly, these stimulation methods are used as research tools, and in this they are pretty well established, especially TMS. There are large literatures about their use in figuring out brain activity-behavior relationships. You use them to show causally that brain area X is involved in cognitive process Y, and provide some puzzle pieces as to in what way. Knowing that they do change neuronal behavior - and this has really been established beyond reasonable doubt - the theoretical probability of their usefulness in achieving desired cognitive effects when you find the right protocol is pretty good. However, this is a far less developed field, although quite a few protocol-disease pairings have gained noteworthy traction. I'm not certain about any being FDA-approved as of yet, although I think some might be? Here's a grab with a clinical theme, TMS for depression and tDCS for schizophrenia:

https://scholar.google.nl/scholar?q=TMS+depression&hl=en&as_sdt=0%2C5&as_ylo=2010&as_yhi=
https://scholar.google.nl/scholar?q=tDCS+schizophrenia&btnG=&hl=en&as_sdt=0%2C5&as_ylo=2010

However, if you want to get more confident about their fundamental effectiveness, you might be better off taking a step back to more fundamental research:
https://scholar.google.nl/scholar?q=transcranial+magnetic+stimulation+mechanism&btnG=&hl=en&as_sdt=0%2C5&as_ylo=2000

[Cathal (Phone)]

Ah, thanks for the call out on TMS:tDCS, my bad. :)

[Nathan McCorkle]

On Wed, Aug 3, 2016 at 12:30 AM, Kermit Henson <kerm...@gmail.com> wrote:
> so, if there are clinical trials.. do you have the data?

I read this recently:
"Evidence that transcranial direct current stimulation (tDCS)
generates little-to-no reliable neurophysiologic effect beyond MEP
amplitude modulation in healthy human subjects: A systematic review"
http://www.sciencedirect.com/science/article/pii/S0028393214004394

[Jonathan Cline]

On 8/3/16 2:13 AM, Raza wrote:
> [TMS] isn't usually DIY'd, as it requires expensive and powerful

> equipment and is considered safe only when used with some expertise.

Key phrases..

0. " is considered safe "
1. " it requires expensive equipment "
2. " it requires powerful equipment "
3. " it requires some expertise "

Key solutions, respectively..

0. prerequisite, otherwise do not continue
1. get rid of lawyers + managers, then cost optimize various designs,
verified against a valid circuit model
2. modernize + miniaturize the design
3. RTFM

[Raza]

Nathan McCorkle wrote:

>I read this recently:
>"Evidence that transcranial direct current stimulation (tDCS)
>generates little-to-no reliable neurophysiologic effect beyond MEP
>amplitude modulation in healthy human subjects: A systematic review"
>http://www.sciencedirect.com/science/article/pii/S0028393214004394

Yeah, for tDCS there's a fraction of strong skeptics. Moderating key words there are "reliable" and "beyond MEP", though.

The motor evoked potential (MEP) is the most robust, simple and direct neurophysiological metric that we have available to measure this sort of thing, so it would be expected be the most reliable tool for showing a real-but-variable effect of a neurostimulation method; and since all neocortex operates along slight variations of the same general mechanism, knowing that the MEP is affected carries generalizable weight. Other neurophysiological measurements generally have more intermediate steps for variation to occur at than the MEP does.

"Reliable" is also an important one, since tons of effects have been shown on other metrics, and the primary complaints as I've heard them (I haven't read that particular paper) are that the effects are too spatially diffuse (and correspondingly unpredictable) and show too much individual variations to make reliable predictions for them on the scale typical, manageable samples. That's all definitely important, but it's still some distance removed from 'snake oil', to place it in the context of the current discussion.

On Wednesday, August 3, 2016 at 8:22:48 PM UTC+2, Jonathan Cline wrote:
>Key solutions, respectively..
>
>0.  prerequisite, otherwise do not continue
>1.  get rid of lawyers + managers, then cost optimize various designs,
>verified against a valid circuit model
>2.  modernize + miniaturize the design
>3.  RTFM

Agreed, wholeheartedly! M'not saying that people not DIYing TMS is as it should be, merely observing it as it is. From what I know about it (I haven't worked with it personally), it shouldn't be too much more difficult than tDCS, if you can muster the patience to read the protocols until nothing in them seems vague or confusing. But you'd be experimenting directly on a person's brain, so getting it right the first time is a bit more important than with the average DIY project.