Stretching the term "High Frequency", there was/is a group at Newcastle University who were attempting to treat epilepsy using a small brain implant which influenced neurons by producing red light
https://www.epilepsysociety.org.uk/p...tment-07-04-14.
Many epileptic conditions respond very poorly to current drugs, pushing researchers to try alternative approaches. I haven't seen/heard anything more recently about this work.
B