[superkuh]

>selective expression of nano-magnetoreceptors in specific neuronal types and brain circuits and activating them with rotating magnetic fields at precise moments, allowing for spatiotemporal control of neural activity.

So invasive genetic engineering used to express the magnetically sensitive (instead of light or ultrasound or whatever) ion channels in the neuronal populations of choice.

Cool stuff, another tool, but there is a way to directly control brains using only magnetic fields and no invasive genetic engineering: transcranial magnetic stimulation. It's where a very, very, very fast changing magnetic field induces a voltage in a tissue. The rate of change of field being proportional to the induced voltage. Generally this means ramping up from 0 to ~5000 amps in a small magnetic coil in less than 10 ms. Unfortunately TMS is not very focal and engineering limits mean the effected tissue regions are about ~5-10 mm spheroids in general (with a slow fall off over large scales); too big for mouse models but fine for humans.

[action-k]

how safe is TMS - has that been studied?

[superkuh]

It has been studied widely in both research and clinical practice for almost 40 years but most extensively since ~1990 to now. With repetitive TMS (rTMS) there are very small chances of inducing a seizure if say, the patient has temporal lobe epilepsy, but it is generally considered a very safe procedure. And there are well established intensity/repetition frequency limits for such cases defined by stimulation region. It is even done in psychiatric (non-hospital) settings. See chapter 5 for more information: http://erewhon.superkuh.com/library/Neuroscience/Magnetic%20... (Magnetic stimulation in clinical neurophysiology / Mark Hallett and Sudhansu Chokroverty. 2nd ed, 10MB PDF)

[paulhart]

I was a research subject for a TMS study a few years ago (I made myself eligible by way of a bicycle accident). Having your thumb twitch because the researcher “shot” magnetic fields at my brain was an amusing experience; she said some people completely freak out at it.