Advanced Biofeedback Center

"Myo" in the Greek language refers to "muscle." The "electro" refers to the electrical activity that is generated when muscle fibers contract. "Graphic" refers to the measurement of the amount of electrical activity generated when a muscle is contracted. In the biofeedback field, EMG activity is measured in microvolts (μv ), or a millionth of a volt. EMG activity can be detected from the skin surface, using painless skin surface sensors (also called electrodes). These skin surface sensors do not apply any voltage to your skin. Rather, they detect or measure the electrical activity you are generating.

A small sensor either taped or affixed with velcro to one's finger or toe is used to measure skin temperature. Why is skin surface temperature important? Skin temperature is an indicator of blood circulation. If hands and feet are cold, there is likely a vasoconstriction, meaning a narrowing of blood vessels (veins, arteries, capillaries). What causes this narrowing? There may be many causes, but worry, anxiety, poor psychological coping, and behavioral problems are known to cause the "autonomic arousal" ("sympathetic activation") associated with this stress response. Human beings are capable of learning how to elevate skin surface temperature to the 95^oF to 96^oF level that is considered "normal."  Skin temperature biofeedback is known to change the vascular (circulatory) system so that individuals can more effectively deal with high blood pressure (hypertension), migraine headaches, Raynaud's Phenomenon, and RSD / CRPS (Reflex Sympathetic Dystrophy / Chronic Regional Pain Syndrome). There are some studies suggesting that skin temperature biofeedback can help patients with diabetes maintain more consistent blood glucose (blood sugar) levels. (Diabetic specialists will acknowledge that patients who effectively deal with stress maintain more consistent blood sugar levels. Skin temperature biofeedback is one approach to deal with stress.)

Neurofeedback is a natural extension of traditional biofeedback modalities like EMG and thermal biofeedback. It represents the measurement of brainwave activity. "Encephalo" is Greek and refers to the brain. In neurofeedback, the "electro" refers to the electrical activity generated by the neurons (nerve cells, brain cells) of the brain. "Graphic" refers to the measurement of this electrical activity, and as in EMG biofeedback, the electrical activity is measured in microvolts, or millionths of a volt. Sensors are attached to the scalp and ears. Generally, neurofeedback helps people to learn how to access and voluntarily control the mechanisms in the brain that regulate attention and sleep. When human beings are agitated, upset, obsessing, ruminating, fretting, and so on, it is not unusual to see predominant EEG activity in the 23 - 38 Hz (Hertz or cycles per second) range (High Beta range). When people are appropriately attentive --- without being worried or distraught --- the predominant EEG activity is typically in the 15 - 18 Hz range in the left hemisphere (Good Beta on the left side of the brain) and 12 - 15 Hz in the right hemisphere (Good Beta [or "Sensory Motor Rhythm"] activity on the right side of the brain). By closing your eyes --- and purposefully disengaging from the environment --- you can achieve Alpha wave activity on both sides of the brain, typically in the 8 - 12 Hz range. A meditative state called Theta wave activity --- almost psychologically "leaving" the environment, again with eyes closed --- is achieved when the predominant frequency is 4 - 7 Hz. Sleep is associated with Delta wave activity, with the predominant frequency at 0.1 - 3 Hz.

Heart Rate Variability (HRV) biofeedback typically involves the use of a photoplethysmograph (PPG) that is attached to your thumb or index finger. There are "red" LED (light emitting diode) sensors that measure blood flow and oxygen saturation (a "pulse-ox" [pulse-oxygen saturation] machine). Some sensors use infrared light --- invisible to the eye --- but nonetheless "shine" a light into the skin surface in conjunction with another sensor that detects how much light is reflected back. Through sophisticated analog to digital (A/D) hardware and software, the PPG --- in conjunction with the appropriate type of signal detection software --- can detect the amount of blood flow into the finger, calculate heart rate, and display breathing patterns. Research has shown that the greater variability in heart rate, the healthier, less stressed, and more emotionally stable one becomes.

Two "silver-silver chloride" (Ag-AgCl) sensors are typically attached with a velcro band the the third and fourth fingers on the patient's hand. Skin conductance level (SCL) is an excellent measure of worry or tension. When your autonomic arousal or sympathetic activation is high, your SCL will be relatively high. When you are fairly relaxed, your SCL level should range between 4 - 8 micromhos (μmhos). (A mho is a unit of conductance whereas an ohm is a unit of resistance.)

Some biofeedback practitioners utilize manual or automatically inflating blood pressure cuffs wrapped around the middle of your arm. You would be taught certain relaxation techniques, and your blood pressure would be made known to you so that you would know if your accomplishing your goal of lowering blood pressure. Another approach is somewhat more indirect, but nonetheless fairly effective. This approach uses relaxation techniques and skin temperature biofeedback. As you voluntarily raise the skin temperature of your index finger (or great toe), for example, you are actually causing a vasodilation. (Your blood vessels [veins, arteries, capillaries] become larger in diameter).  As this widening of your blood vessels occurs, your blood pressure decreases. It is fairly well-accepted that worry and stress increase autonomic arousal, thus causing your blood vessels to constrict (vasoconstriction). Such vasoconstriction causes your blood pressure to become elevated. When you voluntarily decrease worry, tension, and stress  through relaxation and biofeedback techniques, you reverse this process, and your blood pressure lowers. Several studies conducted through the Voluntary Controls Program at the world-famous Menninger Clinic in Kansas demonstrated how skin surface temperature biofeedback was a useful technique for helping research subjects decrease their blood pressure. This allowed some patients to decrease antihypertensive medication dosages, and some others were allowed to discontinue medication completely.

Sensors detecting abdominal (diaphragmatic) breathing versus chest breathing are typically used. A device called a "strain gage" is placed around the abdomen, and as the abdomen increases in diameter as a result of inhalation, the change in the length of this expandable strain gage is detected electronically by the analog to digital converter. A second strain gage may be placed around the chest. The goal is to have the abdominal ("belly," stomach) strain gage move more than the chest strain gage. Ultimately, the expansion and contraction of these strain gages are displayed on a line graph, scrolling graph, or other visual on a computer monitor. By viewing this information, the patient is able to voluntarily increase abdominal breathing and suppress excessive chest breathing. This abdominal breathing --- or "yoga breathing" --- allows for the optimal exchange of inhaled oxygen and exhaled carbon dioxide. This is a much more healthy behavior that benefits virtually every cell in your body.

Either a "red" LED or an infrared device is used to "shine" a light into an area of the brain. Patients learn to increase blood flow to certain areas of the brain that may need to become more activated. Proponents of hemoencephalography have observed anecdotally that HEG feedback requires fewer sessions than neurofeedback to help enhance attention in ADD/ADHD children. Further research is needed to fully delineate HEG applications and expected outcomes.