Earlier quoted context omitted.
Yes, https://en.m.wikipedia.org/wiki/Directed-energy_weapon 2.4 GHz is used to heat your food in the microwave. Pulses that increase the fluence by an order of magnitude or more could probably boil water for a microsecond inside the brain and cause some strange reactions. What is unproven though, is how one would ever shrink the size of an electronic weapon like this.
The Active Denial System, listed on your link, causes pain by heating water in the skin. What is the proposed system for getting microwaves past the skin into the brain without creating the same effect as the ADS?
Could it be there is some way to target a location with multiple radio beams such that the damaging effect occurs at the point of interference? Maybe just constructive interference from multiple weaker beams? Something like this would need to be aimed precisely of course.
I was further led to thinking about the way you can generate sound at a distance from beams of ultrasound. [0] Either the fluid within the beam or an object struck by the beam acts as a demodulator. I don't really know if something like this could apply with radio.
The other thing that I thought of was the way microwave ovens excite water molecules specifically. Maybe there is some other wavelength or combination of them which excites other specific molecules or structures present in the brain?