Neurofeedback is a type of biofeedback that focuses on the neuronal activity of the brain. The training method is based on reward learning (operant conditioning) where a real-time feedback provided to the trainee is supposed to reinforce desired brain activity or inhibit unfavorable activity patterns.
Different mental states (for example, concentration, relaxation, creativity, distractibility, rumination, etc.) are associated with different brain activities or brain states.
Similarly, symptoms of mental or brain-related health issues are associated with neuronal overarousal, underarousal, disinhibition, or instability. Thus, neurofeedback tries to yield symptom relief through an improved regulation of neuronal activity.
Apart from being a therapeutic approach, neurofeedback is increasingly used for healthy people as well, aiming at improved cognitive regulation skills according to individual goals and needs.
There are various methods of providing feedback of neurological activity. The most common application uses the measurement of electroencephalography (EEG), where the electrical activity of the brain is recorded by electrodes placed on the scalp. Other, less usual methods, rely on functional magnetic resonance (fMRI), functional near-infrared spectroscopy (fNIRS), or hemoencephalography biofeedback (HEG).
In 1898, Edward Thorndike formulated the law of effect. In his work, he theorized that behavior is shaped by satisfying or discomforting consequences. This set the foundation for operant conditioning.
In 1924, the German psychiatrist Hans Berger connected several electrodes to a patient's scalp and detected a small current by using a ballistic galvanometer. In his subsequent studies, Berger analyzed EEGs qualitatively, but in 1932, G. Dietsch applied Fourier analysis to seven EEG records and later became the first researcher to apply quantitative EEG (QEEG).
In 1950, Neal E. Miller of Yale University was able to train mice to regulate their heartbeat frequency. Later on, he continued his work with humans, training them through auditory feedback.