I have read the following sentences from an article:
The effect that there are also charge displacements on the body surface due to brain activity is used for the capacitive measurement of the EEG. This change of the charge can in turn affect the charge on a metal plate close to the body. Since this electrical plate does not require direct electrical contact to the body, it can be isolated from the body.
how we could affect the charges of metal plate closed to body without direct contact? does the body acts as the first metal plate of a capacitor?
Is there any specifications to define how much the closeness between electrodes and body?