Biofeedback describes a process in which a subject is given immediate information about his or her bodily processes (such as heart rate), which are usually unconscious. The subject is able to control those processes through training and practice. It is an experimental treatment for disturbances of bodily regulation, such as hypertension. Biofeedback is mostly effective for treating high blood pressure, migraine, and epilepsy.
For a mechanical analogy, consider the classic feedback device: the steam valve. As the steam causes a rotor to turn, the centrifugal force of the rotation causes levers to rise, or strings to fly out, in the same way that if you rapidly turn yourself, your arms fly outward.
The levers on a steam device control the flow of steam, the faster the rotation the smaller the steam vent, the smaller the vent the slower the rotation. The size of the vent, the speed of rotation and the force of the arms closing the valve can all be adjusted so that the rotating axle maintains a consistent speed, so long as the supply of steam is constant.
The same principles hold for feedback within the human body: as a subject eats food, its mouth and stomach fills, and internal sensors send a signal ("satisfied") causing the subject to stop eating.
The ordinary biological feedback of daily living can be enhanced by using mechanical transducers (devices which measure energies). One can press a piece of plastic against ones palm which turns color depending on my temperature. Quickly one learns to make the color redder and redder (the color is arbitrary, it could be bluer and bluer). If a subject is prone to headaches, it can prevent, inhibit or relieve a headache by warming its hand. One may measure the way one's skin conducts electricity and learn to make the skin less conductive.
There is significant evidence that hyperactive boys tend to make high amplitude slow brain waves which are associated with inefficient faster brain waves. The child can be taught to reduce the amplitude of signals slower than 7 pulses per second (<7 Hz for Hertz) and to increase the strenghth of the signals running 13-14 Herz. Such children tend to become more social, more effective at school work, and they perform more adroitly on IQ and other tests.
There is an enormous literature confirming the efficacy of EEG biofeedback for a number of objective goals at www.isnr.com . EEG biofeedback is used to relieve pain, insomnia and for other purposes; GSR (skin conductance) tends to be used for anxiety suppression; muscle tension (EMG) for headache relief and restoration of movement and strenghth; Heart Rate and blood flow are other variables put to good use in medicine.
Technology allows monitoring of internal sources for nearly silent and invisible information and converts it to visual and/or auditory feedback to provide the user or subject a new basis upon which to act. As a result, autonomic functions can be moderated, as well as new therapies learned.
The learning achieved by biofeedback is robust, stable, reliable and readily acquired.
Blood pressure feedback is less readily accomplished than temperature feedback. However, as temperature and bloodpressure are strongly correlated it is possible to learn to manage one physiological dynamic directly while indirectly influencing another.
A trend which is readily discernible is that biofeedback practitioners who initiated their practice using temperature (TEMP) change (which is easily done and is markedly reliable), tend to add muscle tension (EMG) (which is perhaps even more easily done than temperature). TEMP and EMG are the most widely practiced forms of biofeedback.
Significantly, two methods which are more difficult to achieve and to stabilize, have begun consistently to be used to supplement EMG and TEMP training. These methods are Heart Rate (HRV) and EEG. Heart rate is less commonly observed by the ordinary person, although most individuals have noticed the heart rate acceleration and increase in pressure that accompanies startle, fear and marked physical effort. Animals include the human animal seem to be entirely unconscious of the complex electrical activity of the brain. However, it is relatively simple to train animals and humans to produce specific signals in the brain, or to intensify or to reduce the strenghth of certain frequencies.
In 1970 Barry Sterman noted that he could readily train cats to strenghthen the amplitude of signals at 13 pulses per second generated in the brain's Fissure of Roland. Later he observed that cats trained to make stronger 13-14 Hz signals resisted epileptogenic drugs (specifically injected hydrazine). D.A.Quirk, a Canadian penologist, and G.von Hilsheimer, a Florida psychologist, applied Sterman's 1970 method to 2776 felons imprisoned in the Ontario Correctional Institute near Toronto. The recidivism in these prisoners (15% in 3 years after discharge, compared to 40 - 100% in typical prisons) reduced significantly. Subsequently a professional movement has been created using EEG biofeedback in the treatment of ADHD (pioneered by Lubar at the University of Tennessee). In Europe a significant network of practitioners has been organized by Prof. Dr. Jiri Tyl of Prague who has significantly contributed to the proof of the efficacy of EEG biofeedback.
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