Electrodermatography is the recording of the electrical resistance of the skin. In skin conductance, an electrodermographer imposes an imperceptible current across the skin and measures how easily it travels through the skin. The electrodermatogram (EDG) is derived by a particular method of measuring skin resistance and the subject of this article. 
The famous Galen of the second century divided nerves into sensory and motor. In 1810, Bell the neurologist differentiated between the anterior insensible nerve roots and the sensible posterior roots. But it was Magendie in 1822 who made the final distinction between motor and sensory nerves . Magendie's protege Jean-Baptiste Sarlandiere proposed the first heroic therapy of electroacupuncture in 1825. He plunged large needles into muscles along the lines of the ancient Japanese practice of acupuncture. "I know I am in the muscle by the fact that all of the muscle contracts when I apply the smallest sparks .... I believe that I have often stimulated nerves directly. The magnitude of the contraction following the application of very weak sparks convinced me of that". Magendie tried to introduce the needle directly into nerves, but the method was too painful to remain popular.
In 1833, Duchenne de Boulogne became so interested in the procedure of electropuncture that he devoted much of the remainder of his long life to electrical stimulation. He soon found that he could stimulate muscles electrically without piercing the skin and devised cloth-covered electrodes for percutaneous stimulation, the basic design of which is still used. Duchenne called his method of application "localized electrization" and was one of the first to use the alternating current for treatment. Duchenne mapped out the muscles of facial expression.
Although Duchenne's major interest in medical electricity was therapeutic, by his development of electrodes and apparatus, he furnished the tools and stimulated the interest which made the birth of electrodiagnosis possible. He was a difficult person and as a result was given a difficult time by the University physicians, but his perseverance, intelligence and industry have made his name better and longer remembered than the names of most of his detractors. Although Duchenne knew that "there are certain spots along the surface of the body and limbs that give peculiar responses to the electrode in producing ample muscle contraction", he offered no written explanation of what he was accomplishing. The German Remak explained those "spots or border points" where the muscles were most easily stimulated as the points of entry of the muscular nerves. The priority controversy between these two men was one of the bitter academic battles of the century, heightened by the spirit of nationalism, which in their own generation was to result in war. While this argument was raging, von Ziemssen in 1857 carefully mapped out the whole surface of the body, marking the motor points on the skin of agonal patients with silver nitrate, and proved by dissection immediately after death, that his clinical markings corresponded with the entrance of nerves into muscles. Duchenne's unworthy recognition of this masterpiece was, "We must not praise this work too much, for the writer has fallen under the influence of Remak". It is unfortunate that Duchenne, a lonely, proud and bitter man, thus repeatedly lowered world opinion of himself. His contributions to neurology, kinesiology and electrical stimulation were great indeed. He is regarded by many as the founder of electrodiagnosis. It would be more accurate to say that he stimulated the founders.
The history of our modern day forms of electrodiagnosis was closely associated with war traumas of the 20th century. During the First World War large numbers of casualties survived and carried residual effects of nerve injuries. The use of clinical electrodiagnosis increased markedly and the surge continued for several years after the war. There followed a relative lull until the Second World War began. There were even larger numbers of peripheral nerve casualties. Although interest in electrodiagnosis was slow in starting, there grew a postwar interest which received an even greater stimulus from newer electronic technology.
Dermal conductance analysis is the galvanic measurement of skin resistance on sensitive points on the skin. This includes humans and animals. It is a measurement of nervous activity associated with internal function of the organs and bowels. In the 1890s Sir Henry Head discovered certain areas of the skin that develop tenderness (allodynia) in the course of visceral disease. These areas were later termed “Head zones” (viscerocutaneous reflexes). Sir Henry Head was an English neurologist who conducted pioneering work (1896) into the somatosensory system and sensory nerves. Much of this work was conducted on himself, in collaboration with the psychiatrist W. H. R. Rivers, by severing and reconnecting sensory nerves and mapping how sensation returned over time. Head-Holmes syndrome and Head-Riddoch syndrome are named after him. In addition, he also emphasized the existence of specific points within these zones, that he called “maximum points”, a finding that seems to be forgotten today. The search for anatomical correlates of acupuncture-related structures (acupoints, conduits, etc.) has been an ongoing effort since the very first days of Head's research, both Occidental and Oriental. The Russian therapeutist G.A. Zakharin in 1893 also described certain zones of the skin in which the reflected pain, as well as pain and temperature (hyperesthesia) often take place. The anatomical structures most often investigated in this context are those of the nervous system, specifically the dermatomes. This popularity is easily understandable because the nervous system offers mechanisms for both afferent and efferent transmission of signals which decidedly alters skin conductance due to influence on vascularity, sweat and tonus.
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Head's statements on maximum points.
(a) “Every such area of cutaneous tenderness has one or more maximum points, the position of which is exceedingly important, for it is to the situation of these maxima that the patient refers his pain”.
(b) “There is great cutaneous tenderness […] Yet firm deep pressure relieves, rather than aggravates, his pain”.
(c) “Thus, mustard leaves applied to the maximum spots of the affected areas of the chest or back, […] will remove the nausea and vomiting in this mild and purely reflex type of gastric disturbance”.
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Physiologist C. Sherrington (Great Britain, 1905) developed a doctrine about human receptive fields, and divided receptors into exteroreceptors, interoreceptors and proprioreceptors. He formulated one of the main concepts of the workings of the nervous system - the concept of common tract. He showed qualitative predominance of afferent conductive tracts over efferent ones, introduced the notion of the integrative activity of the nervous system and the notion of the synapse as a mechanism of the interneuron bond. In addition he considered the reflex as an elementary functional unit of nervous activity and suggested principles of integration of the reflex at the level of the spinal cord.
The French doctor G. Yavorsky in 1912 suggested the term "reflexo-therapy" which united different manipulation treatments based on stimulation of one's body's surface at certain zones rich in nerve endings. This term is widely used nowadays, though it does fully reflect the essence of a number of diagnostic, therapeutical and preventive methods included in it.
"Electrodermatograms" then emerged because of the great quantity of papers on the subject which appeared since World War II in the medical periodicals of Germany and Austria. In those countries, and especially in the former, there has been an interest for the entire 20th century in reflex pain points and reflex massage. It was believed that considerable value was present if these pain points could be validated by the shear numbers involved in electrical resistance measurements. The subject has received little attention outside of Germany until the 1950's. The acupuncture connection opened research worldwide since then with the author being clinically involved since 1976 to date.
DERMAL CONDUCTANCE
Chemically pure water does not conduct an electric current, but chemically pure water is not found in or on the human body. When water contains even small amounts of salt ions it becomes a conductor. Compare skin conductance to a garden hose. Electrical quantities of voltage, current, and resistance are analogous to pressure, water flow rate, and resistance moving through the hose. The amount of pressure used to drive the water through the hose is analogous to voltage; the rate at which water flows through the hose is analogous to current; and the resistance of the nozzle to the water flow is analogous to electrical resistance. What is required for electrodermal measurement is a source of electrical energy, a sensitive meter (microammeter), a variable resistance circuit to regulate current flow, and the skin contacts or electrodes, one usually held in the hand, the other the probe of interest.
The combined volume of blood and lymph is known as the body's "volume conductor" and is the basis for the electrocardiogram. The skin, its moisture and tonus, is the basis of the electrodermatogram. Depending upon the environmental temperature and humidity, the skin of healthy person is coated with a thin layer of water containing salts. The quantity of water in the skin is governed not only by the atmosphere but also by the number of sweat glands in the skin. This varies markedly from a high concentration in the palm and soles to a much lower level in the trunk and extremities. Moist skin conducts electricity; dry skin resists its passage. The surface electrical resistance of the skin is a function of its wetness (and electrolyte content), thus an index of its sweating and thus sympathetic nerve activity. The ability to sweat is a function of the autonomic nervous system. Loss of perspiration on one area of the skin surface indicates interruption of sympathetic (sudorific) nerve supply to the area. By mapping the "dry" area, an area of reduced conductance, a peripheral nerve or more central lesion can be identified. The measurement of the electrical resistance of the skin is a measure of its wetness and all conclusions drawn from this measurement are based on interpretation and mapping. Thus, when an area of resistance mapped electrically is inconsistent with the healthy clinical picture, the test can be interpreted.
The body's connective tissues are composed of a ground substance of glycosaminosglycans (protein molecules that are held under tension by the collagen fibers). These molecules have water binding properties and vary under influence of hormones, e.g. insulin, and sympathetic nerve influences. Disturbances of the sympathetic nerve activity can change local hydration and thus conductance of electric current. Autonomic nerve dysfunction leads to tissue changes not unlike those seen in reflex sympathetic dystrophy [RSD], but certainly not on that scale of disturbance. These are very subtle changes and not easily recognizable to the naked eye, but measureable with a calibrated electronic device. Gunn developed the "match-stick test": by gently pushing a matchstick into the skin, it leaves a microscopic pitting (the "connective tissue reflex"). We note from probe stylus measurements in DCA, that the more pathological the reading, the more a 3-5 mm pit is left in the skin.
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An important neuronal concept is the so-called Head zones, discovered more than 100 years ago by Sir Henry Head (1861–1940). In a seminal series of papers he published data collected on hundreds of clinical cases. In his studies, Head pursued a 2-fold approach comparing areas of cutaneous tenderness (i.e., dynamic or thermal allodynia) in viscerally diseased patients with patterns observed in rashes of herpes zoster (shingles). Today Head zones are thought to coincide to a large extent with dermatomes, that is, areas of skin innervated by one and the same spinal nerve. The most often cited theory for the mechanism of Head zones is that of viscerocutaneous reflexes: Viscero- and somatoafferent (nociceptive) neurons converge on the level of the spinal cord. This convergence is thought to take place near the lateral column, although the exact location in terms of Rexed laminae as well as the mechanism leading to the false reference of visceral to cutaneous pain signals are still unknown. It is interesting to note that such a common diagnostic tool as the Head zones, is still so poorly recognized more than 100 years after its discovery given the volminous amount of data that acupuncture research has provided.
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Counter-Irritation
Reciprocal to pain and sensations to referred pain zones in the skin, counter-irritation of the skin is an ancient therapy which supports the observations of viscerocutaneous reflexes. These are physical remedies which, by irritation of the skin, are intended to counter or check deeper-lying affections. Counter-irritation is a very old method of treatment, and it still holds a prominent place in therapeutics, today being practiced by acupuncturists. The mode of action of counterirritants has been the subject of much investigation, but the recognition in the last 100 years of a relationship between the viscera and certain areas of the skin and body-wall through the nervous system has thrown much light upon the mechanisms. As early as 1887, Dana called attention to "referred pains" as being due to the distribution of the nerves, and Head (1893) and Mackenzie (1902) determined that tenderness of the superficial tissues to be a manifestation of inflammation or injury of one of the internal organs. The pain in inflamed viscera being distributed to the surface is thus due to a reflex effect through the cerebrospinal nerves. Hence the tenderness of appendicitis is mostly localized at one point, i.e. McBurney's point, though the actual situation of the appendix is very variable; the tenderness of cholelithasis is spread over an area much greater than that of the gall-bladder; and in pulmonary tuberculosis the superficial tissues are sometimes so tender as almost to preclude examination by percussion. Hertz (1911) concluded that pain in disease of the alimentary tract may be situated not only in the skin, but also the muscles, and connective tissues, all locations where acupuncture needles can be placed therapeutically.
These works were endorsed in 1924 by Lemaire who also proposed the treatment of visceral pains using metameric cutaneous injections of Procaine, discovered by Einhorn in 1905. Afterwards, Leriche in 1925 and Sicard and Lichwitz in 1929, demonstrated the importance of dermis in the treatment of visceral pain. In 1933 F. Huneke observed that the paravenous injection of procaine at the loco dolenti produced an almost immediate relief of migraine crises. This is due to the richness of perivascular neuro-vegetative plexi, and this led to today's practice of NEURALTHERAPY - treatment of interference fields from cicatricial zones, responsible for distant pain and pathologies.
Skin Measurement Devices
Skin conductance, also known as galvanic skin response (GSR), electrodermal response (EDR), psychogalvanic reflex (PGR), skin conductance response (SCR) or skin conductance level (SCL), are methods of measuring the electrical conductance of the skin, which varies with its moisture level and the parameters of the device used. This is of interest because the sweat glands are controlled by the sympathetic nervous system, so skin conductance is used as an indication of psychological or physiological arousal. There has been a long history of electrodermal activity research. Richter (1929) devised a skin ohmmeter utilizing a 4.5 volt battery and a 1000 ohm potential divider. Jasper (1945) offered a modification of the dermohmmeter with a tapped 13 volt battery and a tapped 24,000 ohm resistor. Ray and Console (1948) used a 15 volt. battery, and Van Metre (1949) recommended a 22.5 volt battery. Batteries of higher voltage are more suitable for patients with high skin resistance but relatively worthless in studies since that amount of voltage produces a localized effect by decreasing resistance during time of application. Jasper and Robb (1945) and others have showed that the direct current was more desirable than alternating current for testing skin resistance (rather than skin impedance).
Thus, there are many approaches to the study of skin galvanic response, that being (1) macroresponses of sweat gland activity over large surface areas; or (2) microresponses of discrete skin spots over areas of only 2-3 square millimeters, i.e. topographic acupuncture points of reference. Macroresponses of skin conductance measurement, for example, is one component of polygraph devices and is used in research of emotional or physiological arousal. The famous E-meter, which is used by the Church of Scientology, is also a macroresponsive skin conductance measurement device. Skin conductance measurement is also becoming more popular in hypnotherapy and psychotherapy practice where it can be used as a method of detecting depth of hypnotic trance prior to suggestive therapy commencing. When traumatic material is experienced by the client, immediate changes in sweat rate can indicate that the client is experiencing emotional arousal. It is also used in behavior therapy to measure physiological reactions such as fear.
Electroacupuncture studies today are confined to microresponses to body sites confined to 2-3 mm spots using an ultrasenstive detector of less than 1.5 volts on the order of 100 microamperes using a D'Arsonval meter. The basic concept for all of today's ElectroDermal Screening [EDS] devices was the original invention of Dr. Reinhardt Voll, who in the 1950s, discovered that the electrical skin resistance of the human body is not homogenous and that the meridians of Chinese acupuncture influenced skin resistance over the body which may be examined as micro-focalized electrical fields. The same research during this period was being carried out by Dr. Maurice Mussat in France, and Dr. Nakatani in Japan. Nakatani is credited for the discovery of Ryodoten or Electropermeable Points (EPP). Nakatani and Voll both discovered that the number of electro permeable points varied with any disease process. Nakatani called these Responsive Ryodo-points or Reactive Electropermeable points (REPPs). These points often correspond with trigger points or Ah Shi (tender to touch) points. Nakatani theorized, like many before him, that they occurred along tracts of the nervous system and were representative of internal disorder/dysfunction and/or disease. By the 1950s Voll had learned that the body had at least 800 sensitive points on the skin which more or less followed the 12 energy patterns of the classical Chinese meridians. Each of these specific points, on adults and children, Voll called a Measurement Point (MP). Working with an engineer, Fritz Werner, Voll created an instrument to measure the skin resistance at each of the acupuncture points, patterned after Galvanic Skin Resistance (GSR). In 1953, Voll had established the procedure that became known as Electro-Acupuncture according to Voll (EAV). This included three parts:
1. The first part was point testing in which a conductance measurement was taken at selected acupuncture points. Normal measurement values were established on healthy school children, pathologic values were deteremined on numerous patients.
2. The second part was the engineering development to balance these points by the use of controlled electronic pulses.
3. A third technique that developed was the accidental discovery that certain medicines, by virtue of their energy field could influence the conductance at specific points. This became known as Medication Testing. This method due to its transient nature has been most controversial and its confirmation remains for more scientific validation.
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Dr. Reinhold Voll
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Dr. Yoshio Nakatani
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During the 1950s, many investigators studied the electrical conductance of the skin. They evaluated the elasticity, resistance, permeability, and chemistry among many other properties of the skin and found that there was a much lower skin resistance (higher conductance) at specific points on the skin. These points overlapped the classical Chinese acupuncture points. Skin resistance can vary from a few thousand to 1 million ohms, normally. Body resistance is not a fixed quantity. It varies minutely from person to person and from time to time due to weather, from internal disease, and environmental conditions as Burr concluded. Ohm's law states that the electric current or flow drawn depends on the resistance of the body's tissues. So, just as temperature conditions vary, so do electrical conditions. And just as in thermography where room conditions must be stable and ambient, so too with measuring skin conductance, the skin must not be too moist or dry, nor too cold nor hot.
A more precise understanding of these viscerocutaneous reflexes emerged as the Chinese art of acupuncture began to become a popular study in Europe. It was claimed by Becher in 1952 that in the presence of disease, these areas develop an elevated resistance on the side and in the location corresponding to the nervous projection (Head's zones) of the viscus involved. The principal American writer on this subject (Korr) reported in 1949 that the areas corresponding to the involved viscus show a lowered skin resistance. Korr reported the results of a preliminary investigation to determine if paraspinal skin resistance patterns were related to visceral disease. He stated that after examining hundreds of patients, “each had a rather characteristic pattern that remained fairly constant; the size of the areas might vary but the segmental distributions retained the individual’s characteristic pattern. We could identify the subject from his ESR — electrical skin resistance chart — almost as readily as one can from fingerprints. …Repeatedly it has been demonstrated that the distribution of low skin resistance — that is, areas of sympathetic nerve activity — correspond quite well to the actual nerve distribution of the lesioned segment in the spine.”
According to Croon (1960) there are very small areas of skin (two millimeters in diameter) called reaction points, which constitute "neural reflections of intracerebral autonomic nervous junctions of corresponding organs and segments". H. Heine in 1987 histologically pointed out the morphology of the acupuncture points as perforation of fascides of the connecting tissue-vessel-nerves of the superficial fascia of the body and facilitated this way a physical explanation for the electric measurement of acupuncture. Thereby the relation between skin points and distant organs could be understood.
Research Points of the author
The Organizing Principle
Reinhold Voll determined the normal voltage in young children and the normal amount of skin resistance. Abnormal activity in skin spots exhibit either (1) normotonia, (2) hypertonia, and 3 (hypotonia). However, the importance of thiese findings take on even another higher level of understanding. In 1937, Harold Saxton Burr, Ph.D., a Professor of Anatomy at the Yale University School of Medicine, began a series of experiments that sought to measure and characterize the "bio-magnetic field" associated with living organisms. Burr steadfastly believed that life not only exhibited electromagnetic properties, but that these same properties were, in his words, "the organizing principle" that kept living tissue from falling into a chaotic state. The only way to accomplish all of this was to build a volt-ohmeter that had extremely high electrical sensitivity. Whenever a connection is made to a voltage source (whether it is a human being or a salamander egg), a current is going to flow from the voltage source through the connection, and in this case the skin, and back to the meter. The amount of current that flows is directly proportional to the voltage level but inversely proportional to the resistance of the connection, i.e. the skin. The greater the resistance of the connection, the smaller the current flow. This is the basis of an electrodermal device.
Burr reasoned that, since normal biologic growth and development was accompanied by a bio-electric field that appeared antecedent to the beginning of development (Burr's studies showed that the maximum voltage location in the unfertilized salamander egg was a blueprint for the alignment of the fully-developed salamander’s nervous system), abnormal growth would likely be preceded by the appearance of an abnormal bio-electric signature. To test this new hypothesis, Burr and his colleagues "initiated a series of studies designed to investigate the bio-electric properties of an organism before, during, and after the onset of cancer." Briefly, starting at the age of 150 days and continuing until the end of the mouse’s life, Burr made measurements on each of the mice every two weeks. At the 150-day point, all of the mice used in the experiment were free of cancer. Using the microvoltmeter described above, voltages were measured. For the cancer-susceptible mice in which cancer appeared before the 260th day, the voltage across the chest of the mouse increased by several thousand microvolts between ten days and two weeks in advance of the malignant tumor being detected by palpation.
Based on these findings (drawn from more than 10,000 measurements), Burr concluded the appearance of abnormal tissue in the organism was preceded by an abnormal distribution of voltages in the affected area of the body relative to the voltage distribution found in mice that exhibited no palpable cancer. Burr made hundreds of other studies of the bio-electric field as it relates to normal and abnormal processes in living organisms. These studies include, but are by no means limited to
• voltage fluctuations antecedent to ovulation in rabbits, Rhesus Monkeys and humans
• bio-electric concomitants of growth and differentiation in the healing of wounds of guinea-pigs and of humans
• the effect of drugs on the electrical potentials in rats
• correlation between the integrity of the peripheral somatic nervous system and voltage differences measured on the surface of the arm or leg of a human
• detection of malignancy of the human female genital tract
Burr (as well as Voll and the author) was able to demonstrate an accurate, stable, and repeatable technique for measuring the microvolt levels of living organisms. Using this technique he was able to verify his hypothesis of the existence of a bio-electric field that appeared to accompany, or even precede an organism’s biochemistry and patterns of disorganization.
REFERENCES
BECHER H. Electrodermatogram of Head's zones in abdominal diseases. Med Monatsschr. 1952 Mar;6(3):176-9.
Bersenev VA. Structure of the viscerocutaneous sensitive syndrome (pathogenesis of Zakhar'in--Head zones). Zh Nevropatol Psikhiatr Im S S Korsakova. 1979;79(7):884-8.
Burr, H.S. The Fields of Life. New York: Ballantine, 1972.
DUCHENNE, G. B. Treatise on Localised Electrisation. London, 1871.
Heine, H.: Anatomical Structure of Acupuncture Points (Deutsche Zeitschrift für Akupunktur 2/1988, S. 26 - 30)
Heine, H., Koenig, L.: "Morphologische Grundlagen der Elektroakupunktur nach Voll" (Deutsche Zeitschrift für Akupunktur 37, 1/1994, S. 3 - 11)
Korr IM, Thomas PE, Wright HM: “Patterns of electrical skin resistance in man.” J Neural Transmission 1958;17:77.
Korr IM: “Abstract: skin resistance patterns associated with visceral disease.” Federation Proceedings 1949;8:87. In: The Collected Papers of Irvin M. Korr. American Academy of Osteopathy. Indianapolis, IN. 1979. P. 23.
MacKenzie, J. Remarks on the meaning and mechanism of visceral pain as shown by the study of visceral and other sympathetic (autonomic) reflexes. British Medical Journal, vol. 1, pp. 1523–1528, 1906.
REGELSBERGER H. and SEYDEWITZ, H. Early diagnosis of liver disorders with aid of the electrodermatogram. Medizinische 25(47):1743-6 (1957).
REMAK, R. Galvanotherapie. Berlin, 1858.
SARLANDIERE. Memoires sur l'Electropuncture. Paris, 1825.
ON ZIEMSSEN, H. Die Elektricitiit in der Medizin. Berlin, 1866.
March 4, 2011 First posting 2007
