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I previously worked on Virtual Reality and other hardware at Valve.  I currently work at Google[x].

Prior to starting at Valve, I built computer peripherals such as keyboards, mice, and joysticks that were designed to be used inside MRI machines.  My company, Mag Design and Engineering, sold these devices directly to researchers at academic institutions who used them to publish scientific papers in peer-reviewed journals.

After work, I spend time on many different types of projects that usually involve circuit design, machining, material selection, and general fabrication/hacking.  My favorite place to be is my home workshop.

ben dot krasnow at gmail




Sunday, August 7, 2011

Transcranial Magnetic Stimulation project - part 2

I achieved neuronal stimulation of my primary motor cortex by using a single 15-turn coil and 1700 volt charge on the capacitor bank of about 190uF. The exact position of the coil on my scalp makes a very big difference in how much stimulation is achieved in the motor cortex. I would have suspected the single coil would produce much more diffuse stimulation and positioning would not be so critical. I never got any decent neuronal stimulation with the butterfly coil.


  1. While watching the first part of the video, I was surprised by the loudness of the discharge and I was getting impression that some of your movement was caused by the sound. Are you sure you weren't just reacting to the sound?


  2. Anonymous, in professional TMS research, the experiment must be designed to account for effects caused by the loud click and scalp muscle twitching. One way to do this is to target the person's motor cortex, then slowly raise the power from a very low level for each successive stimulation. Eventually, the cortex will be stimulated (evidenced by finger twitching), and the power level is recorded. Later in the experiment, the TMS is used at just below and just above the threshold level, so that the click noise and the muscle twitching will be present in both cases, but brain stimulation in only the higher power level.

    In my experiment, I was not so careful, but I could tell the stimulation was genuinely from the motor cortex since the positioning of the coil on my head was so critical. Just moving 5-10mm would not produce any hand twitching at the same power level.

  3. Neat experiment, glad you were already familiar with the outcome. Where did you find that crazy body diagram near the beginning of the video [0:54]?

  4. Keith, search for "primary motor cortex". You'll find many variations of the diagram.

  5. Hi, your experiment is interesting, but isn't it dangerous ? Please, be careful with your brain, you need it to continue posting such interesting articles.

  6. Anonymous, thanks for your concern. As I mentioned in the video, I work with TMS for my day job, and have seen it done a number of times. Having said that, I don't plan to use the TMS on a regular basis.

  7. I read a paper on TMS that reported irreversible damage to the visual cortex of some subjects, this was during tests of a new coil design.

    Sorry I don't have more details, but please be careful TMS can break your brain.

  8. It seems a bit like doing ESD tests on a CPU.
    Without long term data, there is absolutely no information on the kind of damage you could be doing.

  9. Anonymous, listen to the video again -- especially to the part where I say that I work with TMS for my day job. Did it occur to you that I might have knowledge of how TMS is used professionally and how TMS is regarded by those who have studied it for years? Your guess that TMS causes some "kind of damage" doesn't follow from all of the research done on single-pulse TMS, which shows it has no lasting effects.

  10. Hey! Awesome youtube video and great work.......5000 amps.....damn!

  11. Fantastic experiment! I am very intrigued by electro-neural experiments but lack your courage to experiment on myself. I also am not a professional in the field so that makes me more reluctant than yourself. I actually have all the components and equipment to recreate the experiment but as I said, don't know nearly enough to safely preform this. Might I inquire your academic credentials? I'm just finishing up a Electrical Engineering BS and am considering grad school and would like to pursue research in electro-neural stimulation.

  12. Nice work!

    There is interesting book online about the subject:

    I have not followed the progress on coil designs and arrays for some years but would say, that single point stimulation (or maybe even some area mapping with CNC) with low pulse rate is reachable by dedicated amateur relatively cheaply.

    The reference to VC damage by TMS is interesting, if someone has more information, please link.

  13. You're my hero, I watched most of your videos on youtube.
    I noticed that you placed this thing on your occipital lobe. If you want to see things that aren't there you can use this device. It looks suspect but it works. With me it made a virtual landscape that was kind of like a pixelated 3D computer game. The pixels would rapidly change their brilliant colors. It is an intense experience. Very hard to describe, but very cool!


  14. Wait... You work with TNS as part of your day job, but you work for Valve? What kind of games are we looking at here?

  15. @Keith What's even more alarming is he works for Google now...