Biofeedback
Biofeedback is the technique of gaining greater awareness of many physiological functions of one's own body by using electronic or other instruments, and with a goal of being able to control the body's systems at will. Humans conduct biofeedback naturally all the time, at varied levels of consciousness and intentionality. Biofeedback and the biofeedback loop can also be thought of as self-regulation. Some of the processes that can be controlled include brainwaves, muscle tone, skin conductance, heart rate and pain perception.
Biofeedback may be used to improve health, performance, and the physiological changes that often occur in conjunction with changes to thoughts, emotions, and behavior. Recently, technologies have provided assistance with intentional biofeedback. Eventually, these changes may be maintained without the use of extra equipment, for no equipment is necessarily required to practice biofeedback.
Meta-analysis of different biofeedback treatments have shown some benefit in the treatment of headaches and migraines and ADHD, though most of the studies in these meta-analyses did not make comparisons with alternative treatments.
Information coded biofeedback
Information coded biofeedback is an evolving form and methodology in the field of biofeedback. Its uses may be applied in the areas of health, wellness and awareness. Biofeedback has its modern conventional roots in the early 1970s.Over the years, biofeedback as a discipline and a technology has continued to mature and express new versions of the method with novel interpretations in areas utilizing the electromyograph, electrodermograph, electroencephalograph and electrocardiogram among others.
The concept of biofeedback is based on the fact that a wide variety of ongoing intrinsic natural functions of the organism occur at a level of awareness generally called the "unconscious". The biofeedback process is designed to interface with select aspects of these "unconscious" processes.
The definition reads:
Biofeedback is a process that enables an individual to learn how to change physiological activity for the purposes of improving health and performance. Precise instruments measure physiological activity such as brainwaves, heart function, breathing, muscle activity, and skin temperature. These instruments rapidly and accurately feed back information to the user. The presentation of this information—often in conjunction with changes in thinking, emotions, and behavior—supports desired physiological changes. Over time, these changes can endure without continued use of an instrument.
A more simple definition could be:
Biofeedback is the process of gaining greater awareness of many physiological functions primarily using instruments that provide information on the activity of those same systems, with a goal of being able to manipulate them at will.
In both of these definitions, a cardinal feature of the concept is the association of the "will" with the result of a new cognitive "learning" skill. Some examine this concept and do not necessarily ascribe it simply to a willful acquisition of a new learned skill but also extend the dynamics into the realms of a behavioristic conditioning. Behaviorism contends that it is possible to change the actions and functions of an organism by exposing it to a number of conditions or influences. Key to the concept is not only that the functions are unconscious but that conditioning processes themselves may be unconscious to the organism. Information coded biofeedback relies primarily on the behavior conditioning aspect of biofeedback in promoting significant changes in the functioning of the organism.
The principle of information is both complex and, in part, controversial. The term itself is derived from the Latin verb informare which means literally 'to bring into form or shape'. The meaning of information is largely affected by the context of usage. Probably the simplest and perhaps most insightful definition of information was given by Gregory Bateson—"Information is news of change" or another as "the difference that makes a difference". Information may also be thought of as "any type of pattern that influences the formation or transformation of other patterns". Recognizing the inherent complexity of an organism, information coded biofeedback applies algorithmic calculations in a stochastic approach to identify significant probabilities in a limited set of possibilities.
Sensor modalities
Electromyograph
An electromyograph uses surface electrodes to detect muscle action potentials from underlying skeletal muscles that initiate muscle contraction. Clinicians record the surface electromyogram using one or more active electrodes that are placed over a target muscle and a reference electrode that is placed within six inches of either active. The SEMG is measured in microvolts.In addition to surface electrodes, clinicians may also insert wires or needles intramuscularly to record an EMG signal. While this is more painful and often costly, the signal is more reliable since surface electrodes pick up cross talk from nearby muscles. The use of surface electrodes is also limited to superficial muscles, making the intramuscular approach beneficial to access signals from deeper muscles. The electrical activity picked up by the electrodes is recorded and displayed in the same fashion as the surface electrodes. Prior to placing surface electrodes, the skin is normally shaved, cleaned and exfoliated to get the best signal. Raw EMG signals resemble noise and the voltage fluctuates; therefore, they are processed normally in three ways: rectification, filtering, and integration. This processing allows for a unified signal that is then able to be compared to other signals using the same processing techniques.
Biofeedback therapists use EMG biofeedback when treating anxiety and worry, chronic pain, computer-related disorder, essential hypertension, headache, low back pain, physical rehabilitation, temporomandibular joint dysfunction, torticollis, and fecal incontinence, urinary incontinence, and pelvic pain. Physical therapists have also used EMG biofeedback for evaluating muscle activation and providing feedback for their patients.
Feedback thermometer
A feedback thermometer detects skin temperature with a thermistor that is usually attached to a finger or toe and measured in degrees Celsius or Fahrenheit. Skin temperature mainly reflects arteriole diameter. Hand-warming and hand-cooling are produced by separate mechanisms, and their regulation involves different skills. Hand-warming involves arteriole vasodilation produced by a beta-2 adrenergic hormonal mechanism. Hand-cooling involves arteriole vasoconstriction produced by the increased firing of sympathetic C-fibers.Biofeedback therapists use temperature biofeedback when treating chronic pain, edema, headache, essential hypertension, Raynaud's disease, anxiety, and stress.
Electrodermograph
An electrodermograph measures skin electrical activity directly and indirectly using electrodes placed over the digits or hand and wrist. Orienting responses to unexpected stimuli, arousal and worry, and cognitive activity can increase eccrine sweat gland activity, increasing the conductivity of the skin for electric current.In skin conductance, an electrodermograph imposes an imperceptible current across the skin and measures how easily it travels through the skin. When anxiety raises the level of sweat in a sweat duct, conductance increases. Skin conductance is measured in microsiemens. In skin potential, a therapist places an active electrode over an active site and a reference electrode over a relatively inactive site. Skin potential is the voltage that develops between eccrine sweat glands and internal tissues and is measured in millivolts. In skin resistance, also called galvanic skin response, an electrodermograph imposes a current across the skin and measures the amount of opposition it encounters. Skin resistance is measured in kΩ.
Biofeedback therapists use electrodermal biofeedback when treating anxiety disorders, hyperhidrosis, and stress. Electrodermal biofeedback is used as an adjunct to psychotherapy to increase client awareness of their emotions. In addition, electrodermal measures have long served as one of the central tools in polygraphy because they reflect changes in anxiety or emotional activation.
Electroencephalograph
An electroencephalograph measures the electrical activation of the brain from scalp sites located over the human cortex. The EEG shows the amplitude of electrical activity at each cortical site, the amplitude and relative power of various wave forms at each site, and the degree to which each cortical site fires in conjunction with other cortical sites.The EEG uses precious metal electrodes to detect a voltage between at least two electrodes located on the scalp. The EEG records both excitatory postsynaptic potentials and inhibitory postsynaptic potentials that largely occur in dendrites in pyramidal cells located in macrocolumns, several millimeters in diameter, in the upper cortical layers. Neurofeedback monitors both slow and fast cortical potentials.
Slow cortical potentials are gradual changes in the membrane potentials of cortical dendrites that last from 300 ms to several seconds. These potentials include the contingent negative variation, readiness potential, movement-related potentials, and P300 and N400 potentials.
Fast cortical potentials range from 0.5 Hz to 100 Hz. The main frequency ranges include delta, theta, alpha, the sensorimotor rhythm, low beta, high beta, and gamma. The thresholds or boundaries defining the frequency ranges vary considerably among professionals. Fast cortical potentials can be described by their predominant frequencies, but also by whether they are synchronous or asynchronous wave forms. Synchronous wave forms occur at regular periodic intervals, whereas asynchronous wave forms are irregular.
The synchronous delta rhythm ranges from 0.5 to 3.5 Hz. Delta is the dominant frequency from ages 1 to 2, and is associated in adults with deep sleep, critical for memory, cognition, sleep maintenance, and mental health. Disorders that disrupt sleep such as insomnia, traumatic brain injury, obstructive sleep apnea, and other neuropsychiatric conditions are also associated with the delta rhythm.
The synchronous theta rhythm ranges from 4 to 7 Hz. Theta is the dominant frequency in healthy young children and is associated with drowsiness or starting to sleep, REM sleep, hypnagogic imagery, hypnosis, attention, and processing of cognitive and perceptual information.
The synchronous alpha rhythm ranges from 8 to 13 Hz and is defined by its waveform and not by its frequency. Alpha activity can be observed in about 75% of awake, relaxed individuals and is replaced by low-amplitude desynchronized beta activity during movement, complex problem-solving, and visual focusing. This phenomenon is called alpha blocking.
The synchronous sensorimotor rhythm ranges from 12 to 15 Hz and is located over the sensorimotor cortex. The sensorimotor rhythm is associated with the inhibition of movement and reduced muscle tone.
The beta rhythm consists of asynchronous waves and can be divided into low beta and high beta ranges. Low beta is associated with activation and focused thinking. High beta is associated with anxiety, hypervigilance, panic, peak performance, and worry.
EEG activity from 36 to 44 Hz is also referred to as gamma. Gamma activity is associated with perception of meaning and meditative awareness.
Neurotherapists use EEG biofeedback when treating addiction, attention deficit hyperactivity disorder, learning disability, anxiety disorders, depression, migraine, and generalized seizures.