(including Electromagnetic Harassment)
The head modelled as a ~10 cm sphere is an electromagnetic cavity resonator with a resonant frequency ranging from 400 to 700 MHz depending on its size. It thereby "traps" waves of the resonance frequency via standing-wave generation.
If a signal for reading or influencing brain activity uses a carrier wave of the above frequency range, it will demonstrate maximal interaction with the brain and will therefore exhibit enhanced delivery and EEG enactment.
Brain and body electromagnetism represent an electric/magnetic flux of small intensity which is difficult to measure remotely. However, upon a certain excitation event and specifically spin excitation in the frame of magnetic resonance, it is possible to generate a measurable electric/magnetic flux.
How do we compensate for the low static magnetic field strength of the Earth's magnetic field?