Frequency band neurofeedback is based on training of amplitudes of certain frequency bands in the EEG. The raw EEG consists of waves or frequencies that vary in time, much like a sound signal, or a vibration. These frequencies can be grouped into frequency bands and are named using Greek letters. Each of these frequency bands possess specific characteristics and are involved in various behaviors.
EEG provides useful information but adding other physiological signals like EMG, HRV or skin conductance show state changes via moment to moment autonomic responses.
There are multiple frequency band protocols. All frequency bands can be addressed in training. Some common predefined training protocols are:
The SMR training protocol is based on up-training beta activity in the frequency range of 12-15 Hz. The SMR rhythm is a spindle-like waveform in the EEG, originating from the thalamus and projected to the sensorimotor cortex in case there is reduced activity in the sensory and motor pathways. In other words, when you are physically inactive and mentally alert (but not over-alert), your brain produces more SMR rhythms.
The Theta/Beta ratio is computed by dividing the absolute theta power (4-8 Hz) by the absolute beta power (13-21 Hz). The theta/beta ratio (TBR), or the ratio of slow waves/fast waves in the EEG been used as a marker for the arousal of the central nervous system.
Alpha/theta training uses feedback of slow wave EEG activity to bring a person into a state of deeper relaxation, a hypnagogic state or even an early sleep stage, but without falling asleep. In this state some forms of therapy and/or biofeedback are more effective than in the active waking state.
The gamma rhythm is a pattern of neural oscillations, which can be observed in the entire brain. There is no consensus about the exact frequency range of the gamma rhythm, but it is mostly defined as 35-45 Hz.