Biofeedback is a form of alternative medicine that involves measuring a subject's quantifiable bodily functions such as blood pressure, heart rate, skin temperature, sweat gland activity, and muscle tension, conveying the information to the patient in real-time. This raises the patient's awareness and conscious control of their unconscious physiological activities.
By providing the user access to physiological information about which he or she is generally unaware, biofeedback allows users to gain control of physical processes previously considered an automatic response of the autonomous nervous system. Interest in biofeedback has waxed and waned since its inception in the 1960s; it is, however, undergoing something of a renaissance during the early 21st century, which some experts attribute to the general rise in interest about all alternative medicine modalities. Neurofeedback, a type of biofeedback treatment, has also become a popular treatment for Attention Deficit/Hyperactivity Disorder (ADHD); electromyogram biofeedback, used for muscle tension, has been widely studied and is currently accepted as a treatment for incontinence disorders, and small biofeedback machines are becoming available for a variety of uses in the home. The role of biofeedback in controlling hypertension is also becoming recognised.
The Association for Applied Psychophysiology and Biofeedback, or AAPB is the non-profit scientific and professional society for biofeedback, much akin to the American Psychological Association.
The hypotheses proposed by the Miller group make up one of three major approaches to understanding the mechanism of self-regulation of the body. Voluntary control of the autonomic nervous system had previously been considered impossible, something only controlled by conditioning.
Other threads of inquiry that led to the present-day "biofeedback" emerged from clinical attempts to use mind/body self-regulation techniques in healthcare. Dr. Elmer Green of the Menninger Foundation performed some of the original research on the limits of human self-regulation of processes normally controlled by the unconscious mind and then applied these techniques successfully to the treatment of migraine headaches and hypertension. Dr. Barbara Brown was the first to coin the word "biofeedback" during the early days of experimentation, at the same time as the formation of the Biofeedback Research Society. Other early pioneers were interested in the study of "consciousness" and looked towards electroencephalogram (EEG) self-regulation as a way to approach mind vs. brain dichotomy (see the work of Dr.Kamiya). Other early efforts in the field of biofeedback were directed toward the examination of claims by yogis and others who meditate who were able to demonstrate mind/body control and markers of states of consciousness. See Elmer Green et al Beyond Biofeedback and Barbara Brown Stress & The Art of Biofeedback for some early writings. The Biofeedback Research Society evolved into the Biofeedback Society of America and more recently the Association for Applied Psychophysiology and Biofeedback.
The following biofeedback protocols have received a level 3 efficacy rating: alcoholism/substance abuse, arthritis, chronic pain, epilepsy, fecal elimination disorders, pediatric migraines, insomnia, traumatic brain injury, vulvar vestibulitis.
Biofeedback treatment protocol for urinary incontinence in females has been given a level 5 efficacy rating.
An electromyograph, or EMG is the one of the most commonly used modalities in biofeedback treatment. An EMG in a biofeedback setting typically uses electrodes in order to measure muscle action potentials. These action potentials result in muscle tension. The patient can learn to recognize the way tension subjectively feels by using the objective EMG readings, and as a result learn to control the muscle tension. EMG is used as a relaxation technique to ease tension in the muscles causing backaches, neck pain, TMD, incontinence, and tension, migraine, and cluster headaches. EMG is also used in the process of muscle rehabilitation, such as in cases of paralysis resulting from Cerebral Palsy, stroke, and incomplete spinal cord lesions.
A thermistor attached to the subject's digits or web dorsum measures the subject's skin temperature. Because there is a correlation between a drop in body temperature and the patient's experience of stress, a low temperature reading indicates the need to begin relaxation techniques. Temperature biofeedback can also help in treating certain circulatory disorders, such as Raynaud's disease, and can reduce the frequency and severity of migraines. The physiological processes which are being trained in this modality are vasoconstriction and vasodialation, where blood vessel size is a result of the contraction and relaxation of smooth musculature in the vessel walls. The mechanism being trained in warming exercises is a beta-adrenergic vasodilator mechanism.
In electrodermograph training, sensors measure the activity of a patient's sweat glands. The amount of electrical resistance measured on the skin indicates the level of anxiety. This information can then be used to treat emotional disorders such as phobias, anxiety and stuttering. The best-known use of this method of biofeedback is in polygraph machines. Galvanic skin response meters are currently gaining popularity in hypnotherapy and psychotherapy practices, so subtle physiological changes that indicate emotional arousal can be more easily detected.
An electroencephalograph, or EEG monitors the activity of brain waves. These brain waves correspond to different mental states, such as wakefulness (Beta waves), relaxation (Alpha waves), calmness (Theta waves), and light sleep and deep sleep (Delta waves). EEGs are useful in the treatment of anxiety and ADHD, in which the protocols have been awarded a level 4 efficacy rating by the AAPB.
Photoplethysmographs, or PPGs, in biofeedback are used to measure peripheral blood flow, heart rate, and heart rate variability(HRV). To measure HRV, PPGs measure the varying distances between heart beats, also known as the interbeat interval (IBI). This data guides users in finding a breathing pattern that increases their variability. PPGs are also helpful in biofeedback treatment for some types of cardiac arrhythmias.
A pneumograph measures abdominal/chest movement (as when breathing), usually with a strain gauge. They are used to detect breathing rate, and correct ineffective breathing patterns such as thoracic breathing, reverse breathing, and apnea. They are also often used in conjunction with a PPG in HRV training.
A capnometer measures end-tidal CO2 with an infrared detector. All biofeedback training that employs the use of a capnometer aims at normalizing end-tidal CO2 at 5%. Capnometric biofeedback is useful in the treatment of hyperventilation syndrome. During hyperventilation, end-tidal CO2 lowers from a normal level of 5% to 2.5%.
Hemoencephalography, or HEG biofeedback is a method of functional infrared imaging that indirectly measures neural activity in the brain. There are two known types of HEG, passive infrared (pIR) and near infrared (nIR). Near infrared HEG measures the differences in color of light reflected back through the scalp, based on the relative amount of oxygenated and unoxygenated blood in the brain. Passive infrared measures the amount of heat that is radiated by the scalp at various locations of interest.
David Rosenboom has worked to develop musical instruments that would respond to mental and physiological commands. Playing these instruments can be learned through a process of biofeedback.