**2. Historical background of EDA**

The study of the electrical changes and properties of the human skin began over 100 years ago [3]. Since then, various terms have been utilized to describe this phenomenon including psychogalvanic skin response, skin resistance response, skin conductance response, skin potential response, and EDA. Historically, the most widely used term to label this phenomenon was the galvanic skin response (GSR). However, in 1966, EDA was first introduced by Johnson and Lubin as a common term for all electrical phenomena in the skin, including all passive and active electrical properties which can be traced back to the skin and its appendages [11].

Neumann and Blanton [20] thoroughly reviewed the history of EDA research, which dates back to experiments performed in 1849 by du Bois-Reymond in Germany. In his experiments, du Bois-Reymond used a zinc sulfate solution to put either hands or feet in it and consequently observed that an electrical current going from the limb at rest to the other one was contracted voluntarily. However, du Bois-Reymond considered that the observed phenomenon was due to muscle action potentials [11].

Hermann and Luchsinger from Switzerland in 1878 were the first to experimentally show a connection between sweat gland activity and flow of current in the skin. They observed that an electrical stimulation of the sciatic nerve in the curarized cat caused sweat secretion and an electric current in the footpad on the same side of body [11]. Three years later, the voluntary movement experiment that was performed by du Bois-Reymond more than 30 years ago was repeated by Hermann. It was found that palms and fingers showed greater skin current than other sites of

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*Electrodermal Activity: Simultaneous Recordings DOI: http://dx.doi.org/10.5772/intechopen.89025*

fluidity resistance [3, 11].

focused on [11].

**3. EDA recording systems**

**3.1 Sequentially recording SC and SP**

parameters were sequentially recorded.

the body such as the wrist and elbow areas due to the greater concentration of sweat glands and therefore stronger sweating in that regions [20]. In 1879 Vigouroux was the first who observed that psychological factors are related to EDA. He measured changes in skin resistance (SR) that changed in parallel with the amount of anesthesia in hysterical patients. In addition, he presumed that both phenomena were dependent upon central processes, but he did not believe that the swift changes in SR observed by himself could be resulted by local processes in the skin itself [11]. The pioneering studies of electrodermal phenomena, however, have been done by Fere (1888) and Tarchanoff (1889) [3, 11]. Fere by employing an external direct current observed reduction in SR following emotional stimulation in hysterical patients [11]. Tarchanoff could measure changes in skin electrical potential between

two electrodes connected to the skin surface without the aid of any external electromotive force. He supposed that the EDA phenomena observed by him were due to sweat gland activity, which is dependent on the secretory nerve action. He observed that, even at rest, the current flow from regions of high concentration in sweat glands to those poor in them. In contrast, Fere assumed that decrease in SR following stimulation was due to a decrease in blood flow of the skin, i.e., resulted from partial displacement of the blood peripheral resistance by the lower interstitial

In 1928 and 1929, a decisive contribution to the investigation of the origins of endosomatic EDA was made by Gildemeister and Rein. They for the first time restricted the locus of SP origin to only one of the two recording sites by injuring the skin under the other electrode, where no SP of its own could develop [11]. In 1930 the sweat glands were identified as the seat of the "psychogalvanic phenomena" by McClendon and Hemingway. In the same year (1930), a palmar galvanic test was used for indicating sweat secretion by Wang and Lu. Later EDA measurements became a common mechanism within the field of psychophysiology [19, 21]. SC units were strongly supported by Darrow [22] as well as Lykken and Venables [23] as being sufficient with respect to physiological models of the peripheral mechanisms of EDA. An electrical model of the skin was proposed by Edelberg [24] after having performed EDA research for more than 10 years, which takes into account the existence of polarization capacitances [11]. Using this background, psychophysiological aspects of several EDA components in details were first established by Edelberg [5] including parameters which were subsequently

Nowadays EDA measurement is regarded as "one of the most widely used response systems in the history of psychophysiology" [3] (p. 159). In addition, over the last decades, the areas for application of EDA have been steadily widened such as in the field of engineering psychophysiology as well as in neurology [11]. As EDA is a generic reference that subsumes all methods of measuring the electrical activity

Some authors tried to measure EDA parameters at the same skin site, but such

Venables and Sayer [26] had determined the relationship between the SC and SP, by means of two measuring systems. The idea was to record both EDA parameters at the same skin (palm and inner surface of the left arm), but not simultaneously. They stated that due to the disturbance in the measurement of SP created by the

of the skin, it is the preferred term to label this phenomenon [25].

#### *Electrodermal Activity: Simultaneous Recordings DOI: http://dx.doi.org/10.5772/intechopen.89025*

*Electrochemical Impedance Spectroscopy*

and emotional processes [3, 14, 17, 18].

**Figure 1.**

*Basic components of EDA.*

**2. Historical background of EDA**

analysis is commonly used to quantify the levels of arousal related with cognitive

such as psychopathology, personality disorders, and neuropsychology [14].

The study of the electrical changes and properties of the human skin began over 100 years ago [3]. Since then, various terms have been utilized to describe this phenomenon including psychogalvanic skin response, skin resistance response, skin conductance response, skin potential response, and EDA. Historically, the most widely used term to label this phenomenon was the galvanic skin response (GSR). However, in 1966, EDA was first introduced by Johnson and Lubin as a common term for all electrical phenomena in the skin, including all passive and active electrical properties which can be traced back to the skin and its appendages [11]. Neumann and Blanton [20] thoroughly reviewed the history of EDA research,

which dates back to experiments performed in 1849 by du Bois-Reymond in Germany. In his experiments, du Bois-Reymond used a zinc sulfate solution to put either hands or feet in it and consequently observed that an electrical current going from the limb at rest to the other one was contracted voluntarily. However, du Bois-Reymond considered that the observed phenomenon was due to muscle action

Hermann and Luchsinger from Switzerland in 1878 were the first to experimentally show a connection between sweat gland activity and flow of current in the skin. They observed that an electrical stimulation of the sciatic nerve in the curarized cat caused sweat secretion and an electric current in the footpad on the same side of body [11]. Three years later, the voluntary movement experiment that was performed by du Bois-Reymond more than 30 years ago was repeated by Hermann. It was found that palms and fingers showed greater skin current than other sites of

In spite of sweating being basically a means of thermoregulation, sweat glands located on the plantar and palmar surfaces perhaps evolved to increase grip and enhance sensitivity, possibly more responsive to psychologically stimuli than to thermal stimuli [3, 5, 11, 14]. This relationship between EDA, psychological stimuli, and autonomic nervous system makes this physiological signal broadly popular in neuroscience research studies, including quantification of arousal levels during cognitive and emotional processes, information processing, and clinical research examining predictors and correlates of normal and pathological behavior [3, 17–19],

**100**

potentials [11].

the body such as the wrist and elbow areas due to the greater concentration of sweat glands and therefore stronger sweating in that regions [20]. In 1879 Vigouroux was the first who observed that psychological factors are related to EDA. He measured changes in skin resistance (SR) that changed in parallel with the amount of anesthesia in hysterical patients. In addition, he presumed that both phenomena were dependent upon central processes, but he did not believe that the swift changes in SR observed by himself could be resulted by local processes in the skin itself [11].

The pioneering studies of electrodermal phenomena, however, have been done by Fere (1888) and Tarchanoff (1889) [3, 11]. Fere by employing an external direct current observed reduction in SR following emotional stimulation in hysterical patients [11]. Tarchanoff could measure changes in skin electrical potential between two electrodes connected to the skin surface without the aid of any external electromotive force. He supposed that the EDA phenomena observed by him were due to sweat gland activity, which is dependent on the secretory nerve action. He observed that, even at rest, the current flow from regions of high concentration in sweat glands to those poor in them. In contrast, Fere assumed that decrease in SR following stimulation was due to a decrease in blood flow of the skin, i.e., resulted from partial displacement of the blood peripheral resistance by the lower interstitial fluidity resistance [3, 11].

In 1928 and 1929, a decisive contribution to the investigation of the origins of endosomatic EDA was made by Gildemeister and Rein. They for the first time restricted the locus of SP origin to only one of the two recording sites by injuring the skin under the other electrode, where no SP of its own could develop [11]. In 1930 the sweat glands were identified as the seat of the "psychogalvanic phenomena" by McClendon and Hemingway. In the same year (1930), a palmar galvanic test was used for indicating sweat secretion by Wang and Lu. Later EDA measurements became a common mechanism within the field of psychophysiology [19, 21].

SC units were strongly supported by Darrow [22] as well as Lykken and Venables [23] as being sufficient with respect to physiological models of the peripheral mechanisms of EDA. An electrical model of the skin was proposed by Edelberg [24] after having performed EDA research for more than 10 years, which takes into account the existence of polarization capacitances [11]. Using this background, psychophysiological aspects of several EDA components in details were first established by Edelberg [5] including parameters which were subsequently focused on [11].

Nowadays EDA measurement is regarded as "one of the most widely used response systems in the history of psychophysiology" [3] (p. 159). In addition, over the last decades, the areas for application of EDA have been steadily widened such as in the field of engineering psychophysiology as well as in neurology [11]. As EDA is a generic reference that subsumes all methods of measuring the electrical activity of the skin, it is the preferred term to label this phenomenon [25].
