Transcranial magnetic stimulator

Bill Skaggs skaggs at bns.pitt.edu
Tue Feb 1 13:27:14 EST 2000

Marco de Innocentis <mdeinnocentis at hotmail.com> writes:

> In his book "Phantoms in the brain", V.S. Ramachandran writes
> about a device called a transcranial magnetic stimulator, which,
> in his words, is 'relatively easy to construct' and can stimulate
> any part of your brain. If this is true, then why has such a
> device not been used for commercial purposes so far? Is it because
> its use can be dangerous?
> Marco

The physics of magnetic fields greatly limit the utility of such a
device.  It can only be used to stimulate the neocortex, and only
parts of it that lie within sulci (folds), which make up a rather
small fraction of the whole.  Also, it is impossible to get very much
specificity for the stimulation.  As a result, you can use magnetic
stimulation to get things like limb twitches (by stimulating motor
cortex), or perception of flashes of light (by stimulating visual
cortex), or perception of a buzzing sound (by stimulating auditory
cortex), or a few more subtle effects, but nothing, as far as I know,
that would be commercially desireable.

I don't think magnetic stimulation is particularly dangerous unless
(a) the fields are very strong, or (b) the person being stimulated is
prone to epileptic seizures.

	-- Bill

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