The fields here are still very weak. In the patent, they calculate the strength of the electric field produced in a few different scenarios. The largest value

The fields here are still very weak. In the patent, they calculate the strength of the electric field produced in a few different scenarios. The largest value is 0.21 V/m at 70 com from the screen. It’s not clear to me if that’s at the skin (but in the air, where the subject’s head begins) or in it. Even assuming the stronger case, most of the induced current won’t flow into the brain: skin is so much more conductive that current applied to the head mostly shunts through the skin, and only about 20% enters the brain. (This is also the best case where the anode and cathode are both on the head; the path is much weirder with a mostly insulated person). Thus, the field strength in the brain is almost certainly much lower than 0.04 V/m. We know that fields of about 20 V/m in the brain (i.e., 500x stronger) can cause a neuron to fire, but even that’s under the best possible circumstances; You often need 40-100 V/m. Much weaker fields can alter the timing of spikes, making neurons fire a bit sooner or later than they otherwise might; I’ve shown that fields of 0.3 V/m do have an effect in monkeys. I’m loathe to say that a much smaller field has no effect whatsoever, but if so, it must be a very tiny one indeed.