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> Transcranial Magnetic Stimulation (TMS)
Shawn
post Jan 11, 2004, 08:36 PM
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this is from an article I found online, to give an overview of the TMS technique, which is several years old now. I found the info at http://www.musc.edu/tmsmirror/intro/layintro.html . There's also a very useful link over TMS at http://www.biomag.hus.fi/tms/Thesis/dt.html


A new potential
One very promising avenue for influencing the living brain has emerged in the last decade, based on the use of pulsed magnetic fields. The skull is a good insulator, and past efforts to alter the electrical activity happening inside it have required high voltages, with little opportunity for fine control or focus of the effects. Consider instead how easily a magnet under a wooden tabletop can move a pin on the surface - magnetic fields pass almost unaffected through insulators, including the skull.

It is easy in principle to get a magnetic field to produce electrical effects: simply change the field over time, and any charge-carriers (like the ions in the cells of the brain) will be influenced to flow, creating an induced current. However, affecting neurons inside the head requires a lot of magnetic force to be changed very quickly, and the technology to do this has only been around for about a decade. The first trans-cranial magnetic stimulation (TMS) machines, capable of delivering a pulse every three seconds, were developed as diagnostic aids for neurologists. For instance, the motor part of the brain can be stimulated, inducing a twitch of the thumb, which tells a neurologist that the intervening nerve pathways are intact. Machines are now available which can give up to 50 stimuli per second (rapid-rate TMS, or rTMS) and their effects are more interesting. Among a wide range of possibilities, it is believed that rTMS may have a place in the treatment of some mental illnesses. It is a non-invasive technique, apparently free of serious side-effects, capable of modifying the activity of specific brain areas.

How it works
The magnetic fields used in TMS are produced by passing current through a hand-held coil, whose shape determines the properties and size of the field. The coil is driven by a machine which switches the large current necessary in a very precise and controlled way, at rates up to 50 cycles per second in rTMS. The coil is held on the scalp - no actual contact is necessary - and the magnetic field passes through the skull and into the brain. Small induced currents can then make brain areas below the coil more or less active, depending on the settings used.

In practice, TMS and rTMS are able to influence many brain functions, including movement, visual perception, memory, reaction time, speech and mood. The effects produced are genuine but temporary, lasting only a short time after actual stimulation has stopped.

Safety issues
Generally, TMS appears to be free from harmful effects. Research using animals and human volunteers has showed little effect on the body in general as a result of stimulation, and examination of brain tissue submitted to thousands of TMS pulses has shown no detectable structural changes. It is possible in unusual circumstances to trigger a seizure in normal patients, but a set of guidelines which virtually eliminate this risk are available. Research continues, but TMS is certainly free of obvious side-effects like those of electro-convulsive therapy (ECT), which still makes quite an impact on patients despite refinements in technique.

TMS / rTMS in the treatment of mental illness
Many mental illnesses can be demonstrated to stem from the abnormal behaviour of particular brain regions, in much the same way that diabetes is the result of malfunctioning cells in the pancreas. It is believed that some mental disorders are the result of nerve cells being over- or under-excitable (in other words, it is too easy or too difficult for them to "fire" and work properly). In this context, successful psychiatric treatment is achieved by modifying these cells' behaviour. The range of effects produced by TMS are a clear indication of its potential to work in this way.

Of course, TMS could only be used to treat diseases whose functional causes are understood. Recent progress in understanding the mechanisms behind depression, obsessive-compulsive disorder, and neurological diseases like Parkinson's and Huntington's, offers some hope in these areas. It must be stressed that most of the excitement about TMS is based on potential rather than proven effectiveness, but research is being conducted around the world. For instance, there is reason to believe that rTMS could replace some ECT treatments currently used for severely depressed patients. Groups in Germany, the United States and Israel have reported positive results from using TMS and rTMS to treat depressed patients. The prospect of replacing ECT with a near-painless treatment, which does not require anaesthesia, would change these people's lives remarkably.

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jbramen
post Feb 20, 2004, 09:55 AM
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More about TMS...

I hate to sound like a synic, but I am not sure that TMS will have any widepread use as a treatment tool. It is limited in that it can only target the brain surface. Much brain pathology is located in deep tissues. Also, I don't know that it will ever replace ECT. While little is known for sure about the underlying reasons for ECT's effectiveness, it is thought that a widespread resetting of synchronous neural firing is at its core. It is also believed that much of the brains synchrony is set my connections to the thalamus, a subcortical region not likely to be effected by TMS any time soon.

the other problem with TMS is that it is messy. For most parts of the brain, it remains unclear what underlying cortex has been effected by the pulse. However, areas such as motor cortex control known behaviors, so human subjects can be assessed and the experimentor can know what part of the brain has been effected by stimulation. Of course, not all cortical regions can be tested in this way.

Now this isn't to say that TMS doesn't have its uses. It is often used to study "lesions." TMS can overexcite neurons and put them into a refractory period, where they are unable to respond to further inputs for a short period of time. This has led to very interesting research on topics like mirror neurons. Basically, work in this area has demonstrated that motor cortex is important for sensory perception. We are able to percieve the actions of others by means of "empathy," or by using the same neurons to percieve an action as we do to create an action, in much the same way as we do for emotions and perhapse language.

For more on this subject, see:

http://www.cbd.ucla.edu/bios/iacoboni.html


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cosmos
post May 30, 2004, 01:06 PM
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Could this have a use for temorary intelligence increase through stimulation of neurons in specific areas related to specific forms of intelligence?
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Unknown
post Jun 05, 2004, 10:24 AM
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Well this sounds really interesting to me since my younger brother suffers from Multiple Sclerosis and the myelin around his nerves are affected, which results in nerve damage. I wonder if this has been implemented in any studies conducted in MS research?
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silverheart
post Jun 05, 2004, 10:45 AM
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The previous unkown post was from me, my brother was diagnosed 4 months ago and has numerous lesions on the left side of his brain, he sees in double vision and has spasticity. I am most interested in any break throughs regarding research in the nerves of the brain, particularly the myelin.
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mayonaise
post Feb 04, 2006, 03:52 AM
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TMS is still being developed and has a IMO a lot of potential. Through cascade effects stimulation of the cortex does affect the deeper structures, albeit not as much as with actual DBS (deep brain stim).

Also, today's TMS is not "messy". The structure that is stimulated can be isolated fairly well, at least with the better systems today. These sophisticated versions often connect to fMRI's which also show in real-time what is happening.



This post has been edited by mayonaise: Feb 04, 2006, 03:55 AM
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lucid_dream
post Feb 04, 2006, 11:24 AM
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"Cascade effects" are of no help if you're trying to stimulate a deep structure with any sort of specificity. Given the connectivity of the brain, you can probably get cascade effects in all brain regions by stimulating any one brain region if you stimulate hard enough and have sensitive enough equipment to pick up the smallest perturbation in other brain regions.
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mayonaise
post Feb 04, 2006, 08:52 PM
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QUOTE(lucid_dream @ Feb 04, 09:24 PM) *

"Cascade effects" are of no help if you're trying to stimulate a deep structure with any sort of specificity.

Probably true. But for something like a general module upgrade you wouldn't maybe be needing any more than that. Like if you just want to get the subcortical circuits stimulated, you could do it.

But I really don't know enough to talk much further.
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lucid_dream
post Feb 04, 2006, 10:10 PM
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mayonaise, do you know where you can buy a TMS? I wouldn't mind getting my hands on one but I bet they're expensive.
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mayonaise
post Feb 05, 2006, 02:20 AM
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QUOTE(lucid_dream @ Feb 05, 08:10 AM) *

mayonaise, do you know where you can buy a TMS? I wouldn't mind getting my hands on one but I bet they're expensive.

I have a link somewhere without prices, but you're right, because they're sold for medical use, I bet they are far from free.

The principles of action are at least in part documented on the web though and I know there has been some DIY building. I would like to get one myself but it would too much of a hassle to do all the work myself. That's why I'm thinking of putting together an openTMS group maybe on Sourceforge to gather people who have the same aim.

The power would not have to be as great as in the commercial units to get decent effects on surface cortex, so possibly there could exist shortcuts to make it less expensive, easier to make, etc.
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Tone
post Mar 04, 2006, 01:05 AM
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The Abolitionist Society would like to see an rTMS device that is cheap, portable and stimulator of the midbrain pleasure centers =D
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cerebral
post Mar 04, 2006, 02:11 AM
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QUOTE
The Abolitionist Society would like to see an rTMS device that is cheap, portable and stimulator of the midbrain pleasure centers =D

point them to http://brainmeta.com/forum/index.php?showtopic=13724&hl=
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BellaMaria
post May 01, 2007, 09:25 PM
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QUOTE(jbramen @ Feb 20, 2004, 09:55 AM) *

...I am not sure that TMS will have any widepread use as a treatment tool. It is limited in that it can only target the brain surface. Much brain pathology is located in deep tissues. Also, I don't know that it will ever replace ECT. While little is known for sure about the underlying reasons for ECT's effectiveness, it is thought that a widespread resetting of synchronous neural firing is at its core.


ECT causes brain damage, though, and in studies so far, rTMS does not. That's a very important difference and makes TMS a much more viable and effective tool... because many patients will never try ECT due to its reputation for brain damage.

The studies on TMS for depression are promising, deep tissue or not.
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Hey Hey
post May 02, 2007, 12:10 PM
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Which studies were those?

Bipolar Disord. 2003 Feb;5(1):40-7.

Left prefrontal transcranial magnetic stimulation (TMS) treatment of depression in bipolar affective disorder: a pilot study of acute safety and efficacy.

Nahas Z,
Kozel FA,
Li X,
Anderson B,
George MS.

Brain Stimulation Laboratory, Department of Psychiatry, Medical University of South Carolina, Charleston 29425, USA.

OBJECTIVES: Repetitive transcranial magnetic stimulation (rTMS) has been shown to improve depressive symptoms. We designed and carried out the following left prefrontal rTMS study to determine the safety, feasibility, and potential efficacy of using TMS to treat the depressive symptoms of bipolar affective disorder (BPAD). METHODS: We recruited and enrolled 23 depressed BPAD patients (12 BPI depressed state, nine BPII depressed state, two BPI mixed state). Patients were randomly assigned to receive either daily left prefrontal rTMS (5 Hz, 110% motor threshold, 8 sec on, 22 sec off, over 20 min) or placebo each weekday morning for 2 weeks. Motor threshold and subjective rating scales were obtained daily, and blinded Hamilton Rating Scale for Depression (HRSD) and Young Mania Rating Scales (YMRS) were obtained weekly. RESULTS: Stimulation was well tolerated with no significant adverse events and with no induction of mania. We failed to find a statistically significant difference between the two groups in the number of antidepressant responders (>50% decline in HRSD or HRSD <10 - 4 active and 4 sham) or the mean HRSD change from baseline over the 2 weeks (t = -0.22, p = 0.83). Active rTMS, compared with sham rTMS, produced a trend but not statistically significant greater improvement in daily subjective mood ratings post-treatment (t = 1.58, p = 0.13). The motor threshold did not significantly change after 2 weeks of active treatment (t = 1.11, p = 0.28). CONCLUSIONS: Daily left prefrontal rTMS appears safe in depressed BPAD subjects, and the risk of inducing mania in BPAD subjects on medications is small. We failed to find statistically significant TMS clinical antidepressant effects greater than sham. Further studies are needed to fully investigate the potential role, if any, of TMS in BPAD depression.
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Orbz
post May 02, 2007, 04:46 PM
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Maybe not for bipolar depression but there's a fair bit of evidence for depression without mania.

J Neuropsychiatry Clin Neurosci 19:179-186, May 2007

Antidepressant Effects of High and Low Frequency Repetitive Transcranial Magnetic Stimulation to the Dorsolateral Prefrontal Cortex A Double-Blind, Randomized, Placebo-Controlled Trial
William M. Stern et al

Repetitive transcranial magnetic stimulation (rTMS) has antidepressant effects in patients with major depressive disorder. The mechanisms of action and optimal stimulation parameters remain unclear. To test the hypothesis that rTMS exerts antidepressant effects either by enhancing left dorsolateral prefrontal cortex (DLPFC) excitability or by decreasing right DLPFC excitability, the authors studied 45 patients with unipolar recurrent major depressive disorder in a double-blind, randomized, parallel group, sham-controlled trial. Patients were randomized to receive 1 Hz or 10 Hz rTMS to the left DLPFC, 1 Hz to the right DLPFC or sham TMS. Left 10 Hz and right 1 Hz rTMS showed similar significant antidepressant effects. Other parameters led to no significant antidepressant effects.
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maximus242
post May 02, 2007, 10:46 PM
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mm, rTMS has alot of potential, the magnets are rediculously strong, like it would rip a necklace right off your neck 6 feet away. But you need strong magents in order to penetrate the skull and change the frequency of the brain. They use a coil based electro-magnet, usually in a 8 shape, you can see the coils wrapped in a white ceramic outer shell.

There are some restrictions, TMS is big, bulky, requires vast amounts of power and will influence the magnetic field around it for miles. There are indeed some safety issues but it is a hell of alot safer than electrostimulation. The main concern is how close the coils need to be placed in relation to the skull, usually its about half an inch or less. These coils become extremely hot and require a closed coolant system flowing throughout the electromagnetic coils.

Because of this, the potential to be burned by the coils is one safety concern. Although I cant remember anyone actually having experienced that.

TMS is overall very intresting, there are certain restrictions to its use, but I imagine that these will diminish over time.
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Hey Hey
post May 03, 2007, 03:14 AM
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QUOTE(Orbz @ May 03, 2007, 01:46 AM) *

Maybe not for bipolar depression but there's a fair bit of evidence for depression without mania.

J Neuropsychiatry Clin Neurosci 19:179-186, May 2007

Antidepressant Effects of High and Low Frequency Repetitive Transcranial Magnetic Stimulation to the Dorsolateral Prefrontal Cortex A Double-Blind, Randomized, Placebo-Controlled Trial
William M. Stern et al

Repetitive transcranial magnetic stimulation (rTMS) has antidepressant effects in patients with major depressive disorder. The mechanisms of action and optimal stimulation parameters remain unclear. To test the hypothesis that rTMS exerts antidepressant effects either by enhancing left dorsolateral prefrontal cortex (DLPFC) excitability or by decreasing right DLPFC excitability, the authors studied 45 patients with unipolar recurrent major depressive disorder in a double-blind, randomized, parallel group, sham-controlled trial. Patients were randomized to receive 1 Hz or 10 Hz rTMS to the left DLPFC, 1 Hz to the right DLPFC or sham TMS. Left 10 Hz and right 1 Hz rTMS showed similar significant antidepressant effects. Other parameters led to no significant antidepressant effects.

This is really interesting. Saying something about depression in bipolar versus depression alone (but importantly, that is actually commonly misdiagnosed bipolar)?
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reyra
post May 13, 2007, 12:04 PM
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depression in bipolar vs. depression alone, what are you talking about? it sounds very interesting. Could you please explain a little bit more about this. thanks.
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Hey Hey
post May 13, 2007, 12:20 PM
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QUOTE(reyra @ May 13, 2007, 09:04 PM) *
depression in bipolar vs. depression alone, what are you talking about? it sounds very interesting. Could you please explain a little bit more about this. thanks.

Bipolar disorder, often referred to as manic-depression in the general literature, is a psychiatric condition defined by periods of extreme mood. These moods can occur on a spectrum ranging from debilitating depression to unbridled mania. Hence bipolar.

http://www.bipolar.com/
http://en.wikipedia.org/wiki/Bipolar_disorder
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Kaloa
post Nov 07, 2010, 04:34 PM
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Exerpt from website above>> http://www.musc.edu/tmsmirror/intro/layintro.html

"The magnetic fields used in TMS are produced by passing current through a hand-held coil, whose shape determines the properties and size of the field."



(Besides the handheld version, Ive also seen the helmet version of this that was used/being used in Isreal I believe.)

This is really interesting to me.
So; then, the figure 8 shape is used to produce the straitest, thinnest, most concentrated line of megneticism?

I mean, what is the nature of the relationship to the geometry of the magnet, its overall geometry, and the geometry of it's magnetic output/field?

Is there a great relationship going on here? If so; what is it?

I am very interested in this particular aspect. (Please forgive my ignorance on the matter in general, which is great) Does anyone here know much about the electromagnetic dynamics of different shaped mangnets in general, and the relative forms of their different outputs/fields, ie. size/shape/distribution/strength weakness?

I know that donut shaped magnets have more power because they complete a circuit, and that's about all I know. I can't read the formulas that describe things mathematically, and so I'm so far unable to persue this particular intrigue of mine. sad.gif... Any help would be awsome!
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