To add: Water has an absorption band that is clear to most visible light and the near IR, but it starts to absorb as you go deeper into IR. Many tissues and their light absorption curves can be seen here:

https://en.wikipedia.org/wiki/Near-infrared_window_in_biolog...

People have actually used infrared to stimulate neurons directly. The mechanism is a little weird, and may be a combination of direct heating (e.g., causing chemical reactions to run faster) and activation of temperature-dependent ion channels.

https://www.sciencedirect.com/science/article/pii/S105381191...

Radio is probably much too fast--the time constant of a neuron is on the order of 10ms, so unless you're pumping a lot of instantaneous power into the neuron, the net effect is likely to be zero.