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If a simple coil is able to do this to the brain, how come the many Teslas of a superconducting MRI magnet don't do zip?

Genuinely interested...




The 1 T+ field your thinking of is a static magnetic field. Static magnetic fields don't induce currents (except in rapidly moving objects) and have no known effects on the brain or biology (at least for the field strengths available for MRI, really extreme magnetic fields might cause such effects).

MRI machines also use much smaller modulated magnetic fields during a scan. It's conceivable these could have TMS like effects but as far as I know they don't in practice. I imagine TMS uses fields which are stronger than these since I believe the excitation coils are placed in very close proximity to the head.


I don't know anything about brain stimulation but my guess is it's tied to a narrow frequency range so the huge static magnetic field and the high frequency RF pulses don't do a thing. It would be nice to know this frequency range, is it tied to neural oscillation [1]?

[1] https://en.wikipedia.org/wiki/Neural_oscillation


the big field of an MRI scanner is static and very uniform (there is also an RF field during scanning, but it's smaller). TCMS is very dynamic and tight.




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