Neurofeedback is a type of operant conditioning which may be classified as biofeedback. Part of the patient's scalp derived BEG is recorded in approximately real-time and the patient is offered a reward when the local BEG approaches or remains within specified parameters. A general proposition for biofeedback of various kinds is that those who use the technique may become able to modify their behavior by learning to control various physical functions such as heart rate, breathing, localized muscle activity and so forth.
Biofeedback may be considered part of a very wide variety of techniques by which an individual may learn to control aspects of his physiological and brain function consciously and/or unconsciously so as to achieve a different behavioral state. Such techniques would include yoga, meditation, various forms of military drill, the practices of "whirling dervishes", self-flagellation, religious ecstasy and so forth.
In therapeutic practice, the person being trained by biofeedback commonly is offered awareness of a bodily function which he or she might not usually notice as such and can learn to control that function by responding to changes in the function. For instance, the trainee may be made aware of his or her own heart rate, for instance with a loudspeaker and may be able to learn to make the heart beat faster or slower. Often, the person being trained is made aware of the degree of muscle tension in some part of the body, for instance the forehead, and can learn to control that. In this sort of biofeedback, the operant stimulus is the awareness of that particular body function and the person being trained is rewarded by becoming aware of his or her own ability to change some aspect of the function.
An aspect of the complexity of physiology is that it may be possible to modify an individual's unconscious as well as conscious behavior in ways not immediately or obviously related to the stimulus/response cycle being trained with biofeedback. Consequently, learning, for instance, to relax forehead muscle tension, may allow the person being trained to develop the ability to relax mentally in other ways.
These kinds of biofeedback depend on relatively easily measured and presented physiological stimuli. Awareness of change of the physiological parameter may by itself be considered the reward. Alternatively, this may be related to some other form of reward such as music, changing lights, encouragement, and so on.
All these types of biofeedback and other techniques such as those mentioned above in fact depend on modification of brain activity via indirect measurement of changes in the effects of such brain activity.
A central proposition for the technique generally known as neurofeedback is that it is possible for an individual to become more directly aware of some aspects of his or her brain function and to learn to control the measured phenomena which more directly represent that brain function. The usual method is to record the scalp electroencephalogram from one or more locations on the individual's scalp and, by measuring that signal in real-time and representing it to the individual in the form of a reasonably easily recognized and modifiable sensory signal allow the subject to learn to modify cerebral function in such a way that the scalp electroencephalogram changes.
The electroencephalogram (EEG) and its changes may be represented as music, lights, movies and in other ways. The individual is rewarded by improved quality of the sensory experience when his or her EEG changes towards the desired pattern. It is considered that this "treatment" may produce rapid change in behavior over a few minutes and that repeating the process frequently may produce long-term change in cerebral function and associated long-term change in the individual's behavior. Depending on the situation, this long-lasting change may be produced by relatively few sessions or may need frequent reinforcement.
Looked at this way, neurofeedback may be classified as a method of directly altering brain electrical activity. There are other generally accepted methods of direct electrical modification of brain function.