Home transcranial magnetic stimulation

blue_magnet.jpgTranscranial magnetic stimulation (TMS) is a technique whereby magnetic fields are used to temporarily alter the function of the brain by inducing an electrical current in the brain tissue.

In neuroscience research, TMS usually refers to the use of powerful magnetic fields (about 1.5 tesla or 40,000 times the earth’s magnetic field) focused on approximately 1x1cm areas of the cortex.

Repetitive TMS (rTMS) can be used either to make the area more active or less active over a specific time period (often 30 minutes or so), while single pulse TMS is used to harmlessly ‘knock out’ an area for approximately 100ms.

Much weaker magnetic fields (about the strength of a loudspeaker) but much more complex in form, have also been used to induce unusual experiences by stimulating the temporal lobes, most notably by neuroscientist Dr Michael Persinger.

A new project called Open-rTMS aims to develop this latter type of system (actually, generally not referred to as TMS in the neuroscience literature) and publish the plans and software online.

They’re currently looking for people to sign up to the mailing list and kick the project off, so if you’re looking for a way to alter your state of consciousness with magnets, this might be your chance.

The project is similar in approach to the OpenEEG project, which aims to provide software and plans for a home EEG system, so you can read the brain’s electrical activity.

Link to Science News article on high-strength TMS.
Link to low-strength Open-rTMS project page.

8 thoughts on “Home transcranial magnetic stimulation”

  1. I don’t know much about ‘low-strength’ rTMS, but I do know that I am not going to allow anybody to use standard lab rTMS on me. It probably is ‘harmless’ when used on areas like primary visual cortex, but who knows what it’s doing in temporal areas?
    It’s a great research tool. (For one thing because it allows you to test causal relationships using perturbations/interventions, which is one of the strongest tests of a causal relationship). But I’m not signing up to be a subject.
    Purely anecdotally, I’ve heard that people who run around TMS-ing each other in their labs have exhibited the occasional lost memory or brief mood changes. Anecdotally again, I’ve also heard the behavioral patterns of subjects who return for testing 1 week post-TMS are often subtly different from controls… so for example their reaction-time means might be the same, but the distributions are altered. I have also heard that TMS is being used therapeutically, which means that it must have some medium-term effects, right?

    1. I have had the clinical treatment and it worked after 30 years of depression. I did not suffer any memory loss or any other effects whatsoever, besides the cure for my depression. Your ANECDOTAL stories are interesting but you have no idea what you are talking about and did not use any empirical evidence to suggest you do.

      1. Dan – Can you please let me know how you obtained the treatment and if your depression has come back i.e. do you require maintenance treatments?

  2. Christopher,
    Your comments on TMS I find intriguing. I agree with the paranoia about temporal areas. I’m curious, though, about your comment in regards to returning participants to testing 1 week post-TMS and their subtle difference from controls…
    What kind of subtle difference are we talking about here? Are you referring to reaction times, cognitive measures? Or something more vague like emotions? Is this something that was tested or just an observation from those performing the trials on the participants?

  3. The cerebral cortex is typically a good 1-1.5cm away from the scalp surface. Since the measured electromagnetic energy from the low-intensity coils decreases as a function of the square of the distance from the source, I suspect that these devices produce extremely low amounts of EMR within the cortex which is closest to the skull. What is the evidence that there is a measurable effect?

  4. Neurointerest — yes, if I remember correctly the reaction time distributions were different, although not at the levels of the mean. But this was all second hand. See the papers below, esp. the second one, for some more reliable evidence about the range of effects rTMS can produce.
    Roy — TMS can be run in single strong pulses or with repeated weak pulses; the pulses can also be more or less diffuse. So the effects differ. But a quick search turned up these two papers:
    “Left prefrontal activation predicts therapeutic effects of repetitive transcranial magnetic stimulation (rTMS) in major depression.”
    Eschweiler et al. (2000) Psychiatry Research
    “Repetitive transcranial magnetic stimulation dissociates working memory manipulation
    from retention functions in prefrontal, but not posterior parietal, cortex”
    Postle et al. (in press) Journal of Cog Neurosci

  5. I can add to anecdotal reports about short-term memory loss using TMS. A former colleague of a labmate’s (yes, the academic equivalent of “a friend of a friend”) reportedly TMSed his girlfriend and was rewarded with two or three days of memory trouble. I’m sure it did wonders for their relationship. My labmate had the sense that the effect was not particularly uncommon – especially while determining proper sequences.
    But, yes — anecdotal.

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