A "Killer App" for Transcranial Magnetic Stimulation

Transcranial Magnetic Stimulation is the process of inducing an electrical current in the brain using electromagnetic induction .  This works using the same mechanism that creates a current of electricity in one wire when it is placed near another wire passing alternating current, which is used in electrical transformers, AC electric motors, inductive cooktops, etc.

What’s exciting about this technology is that it allows you to stimulate areas of the brain in ways that previously required cutting holes in the skull. There have been many interesting experiments where electrodes are implanted directly ( cortical implants ) into the brain which can then be used to trigger emotional reactions or even transmit information. Many people think that TMS may allow us to achieve the same results without surgery, which makes the whole thing a lot more practical.  It also makes it more feasible for experimentation outside of the medical field.

X-ray of early implanted
electrodes

_X-ray of early experimental implanted electrodes (more info at http://www.pages.drexel.edu/~dh329/bmes212/cortical.html ) _

While the idea of sending images directly to the brain is enticing, and certainly something we want to explore, doing so with TMS is complicated because experiments that have done this so far with traditional electrodes have involved arrays of individual probes arranged in grids (similar to pixels on the screen) and this sort of array is difficult to achieve at with TMS (at least so far).  Other senses may be simpler to trigger, but we don’t know as much about simulating them because traditionally computer simulations have only stimulated two human senses: vision and sound.

I’ve been listening to a lot of music on my iPod lately and have become more aware of how uncomfortable headphones, earbuds, etc. can get after several hours of wearing them.  I’ve also noticed that there are distinct “gaps” forming the frequency range of my hearing (I’m sure it has nothing to do with practicing Metallica songs at concert volume in Derek ’s basement).  This got me thinking about ways to reduce the physical components of listening hardware as well as ways to compensate for partial hearing loss, and then a light went on. Audio reaches our ears in waves, and while creating arrays of stimulation with TMS is hard, transmitting a wave to a particular spot of the brain is much simpler.  Perhaps TMS could be used to transmit audio directly to the auditory cortex of the brain?

If so, there’s a few immediately interesting applications:

  • Overcoming hearing loss that is due to damage of the ear
  • Listening to music and other audio with less intrusive physical apparatus
  • Hearing sounds that are beyond the range capable with human ears

The reason I think this is a “killer app” is that it has the traits of being achievable within the limits of imaginable technology, and the work to carry out this application will uncover information necessary for additional and more ambitious future projects.  Especially when you consider the market for high-end headphones, it’s not hard to imagine a device like this with a cost that might seem reasonable in this range.

Like anything else that deals directly with the brain, the process of testing and proving whether or not this is possible isn’t simple, but a path for the experiment is conceivable, and the cost of the equipment necessary is rather low in comparison to the potential value of any application imaginable.  I plan to carry out some of the research and experiments myself, but if you find this interesting and would like to participate, or have something you’d like to contribute to the work, please let me know.

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- Jason

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