That's not right: electric and magnetic fields are used to alter brain activity, even non-invasively. Transcranial magnetic stimulation uses pulsed magnetic fi

That's not right: electric and magnetic fields are used to alter brain activity, even non-invasively. Transcranial magnetic stimulation uses pulsed magnetic fields produced by a strong electromagnet. It's currently an FDA-approved treatment for depression and a pretty common research tool. The fact that it has (some) biological effect is pretty clear: aim it at motor cortex and you can make someone's finger (leg, etc) twitch! Transcranial electrical stimulation (tES) is a family of techniques that apply weak electric current to the scalp to affect brain activity. These include tDCS (with Direct Current) and tACS (Alternating Current). While their effectiveness has been debated, my group has collected data demonstrating robust effects on the activity of neurons, even deep in the brain. Check out Figure 1 of this paper: https://www.pnas.org/doi/10.1073/pnas.1815958116 https://www.pnas.org/doi/10.1073/pnas.1815958116 It's not always that simple, and it interacts in complicated ways with ongoing brain activity, but it does do something too. You can get much strong effects if the electrodes are inserted directly into the brain (or muscle) too but it's not all the case that EMFs are biologically "inert".