**3.2 Alternately (simultaneous recording at different skin sites) recording SC and SP**

Articles presented here are associated with authors, who tried to measure EDA parameters simultaneously, but not at the same skin site, i.e., EDA parameters were recorded alternately.

Wilcott [29] had recorded SR (SC) and SP simultaneously contralateral from the left and right-palm-upper-arm locations to study the correlation between both these EDA parameters. He obtained significant correlations between the SC and the SP amplitudes. Regarding the possibility of recording EDA parameters at the same skin site, Wilcott claimed that simultaneous measurement of EDA parameters is impossible and stated that "As it is of course not possible to record the two types of bioelectrical activity (e.g., SC and SP) from the same skin area simultaneously, they were recorded alternately from the same skin area and simultaneously from different skin areas" [29].

To elucidate mechanisms underlying the appearance of the diphasic potential (SP) curve, SC and SP simultaneously from the palm and the dorsum of the hand were recorded by Yokota et al. [30]. SC and SP simultaneously from the palm and the dorsum of the hand were recorded by Yokota et al. [30]. Sequence recording of SC and SP was applied so as to enable a comparison of the results with each other. When the SP was recorded simultaneously with SC from different parts of the same palm, diphasic potential curve changes usually corresponded to larger resistance changes [30].

According to Edelberg and Burch [31], both SC and SP are widely used as indicators of autonomic activity in psychological and pharmacological investigations, but the many fundamental controversies to be found in the literature testify to the questionable reliability of these measures [31]. In addition to the external stimuli and central excitatory state, various outside factors constitute a third category of variables (skin temperature, current density, electrode composition and size, contact medium, and electronic circuitry) affecting SP and SC responses. These factors are difficult to control, when comparisons between SP and SC are to be made separately (recording each of which at certain time). However, when they are compared simultaneously, effect of such variables can be canceled out [31].

Relations between simultaneously recorded SC and SP changes are obtained at high and low levels of bodily excitation by Darrow [22]. Electrodes were connected to the palm and the wrist of both hands in order to simultaneously record SC and SP between two opposite sites.

**103**

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

conditions of passivity and motor activity [33].

simultaneously at two different skin sites [36].

phenomena [34].

Burstein et al. [32] reported simultaneous recording of SR (SC) and SP responses generated by different psychological stimuli. The aim was to show effects of such stimuli on responses of both EDA parameters and to determine the significance of the different wave forms of skin potential [32]. SC responses were recorded from middle and index fingers of the left hand, and SP responses were recorded from the right ear lobe and the right index finger. They found that both SC and SP are highly effective in assessing differential emotional responses. However, total SP yields slightly more significant results than does the SC measure. They finally suggested that the skin potential response merits further investigation because the

qualitative differences in its wave forms may be of special significance [32]. Hupka and Levinger [33] recorded palmar SC and SP simultaneously with nonpolarizing electrodes, connected to the thenar eminence of the right and left palm and on the dorsal right or left forearm. Authors aimed to investigate whether the SPR negativity remains a constant correlation with the SCR during different

SC and SP were recorded simultaneously from opposite hands during a stress period and a subsequent prolonged relaxation by Lykken et al. [34]. Their aim was to investigate certain interrelationships between concurrent measures of SC and SP through employing a simple equivalent circuit model of steady-state electrodermal

The correlation of change measures and prestimulus level in SC and SP and the amount of correlation between SP and SC measures were studies by Gaviria et al.

The effect of repeated stimuli on reader and nonreader child with respect to physiological orienting response patterns in the autonomic nervous system was investigated by Hunter et al. [36]. Authors aimed to fined difference between those two groups through simultaneously recording SC and SP. For SC recording electrodes were placed to the volar pads of the first and third fingers, and for SP recordings the active electrode was placed on the volar pad of the middle finger, and the reference electrode was placed on the forearm; thus both SC and SP are recorded

In order to investigate possible differences between healthy subjects and unhealthy (schizophrenic) subjects, Patterson and Venables [37] recorded SC and SP at the same time but at two different skin sites by two different measuring systems. Electrodes for SC recording were attached on the medial phalanges of the first and second fingers of both hands and for SP were placed on the hypothenar

The validity of SC and SP for preliminary cystic fibrosis screening has been demonstrated by Williamson et al. [38]. Electrodes for SC recording were attached to the palmar surface of the fingers. For the measurements of SP, the active electrode was being placed on the palmar surface of the distal middle phalanx of the hand [38]. Discriminant analysis using the two best EDA measures (SC and SP) for assignment of experimental group membership yielded 92.7% correct classification of the actual group membership. However, both SP and SC recordings were necessary to obtain such accuracy, since reclassifications of participants by discriminant analysis using only the six SC or the six SP measures lowered the percentage of correct classifications to 77% for SC and 86% for SP. Authors stated that it would simplify clinical procedures to use only the SP or only the SC measures to distinguish between group (health and unhealthy) subjects, because only one hand would be recorded and scored [38]. However, according to their results, recording more than one EDA parameters at the same time would lead to more meaningful results. Collet et al. [39] showed neutral and emotionally loaded pictures to some test subjects in order to evoke happiness, surprise, anger, fear, sadness, and disgust.

eminence of the right hand and an abraded surface of the right arm [37].

[35]. SP and SC were recorded in a sequence at two different skin sites.

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

*Electrochemical Impedance Spectroscopy*

simultaneously [27].

**and SP**

recorded alternately.

ent skin areas" [29].

changes [30].

be canceled out [31].

between two opposite sites.

so highly as to make them equivalent [26].

the elbow on the volar surface of the forearm [28].

presence of the impressed voltage used to measure SC, the two measures were not taken simultaneously. It was found that the two measures are related, although not

The role of sweat gland activity in the mediation of SC and SP levels was investigated by Venables and Martin [27]. Both SP and SC were recorded at the same skin site (tips of the fore, middle, and ring fingers of each hand), but not

Turpin and Siddle [28] presented effects of series of auditory stimuli on the sequential SCR and SPR recordings. Bipolar recording of SC was accomplished by attaching electrodes on the medial phalanx of the index and second fingers of the non-preferred hand of the subject. Unipolar recording of SP was made by placing electrodes on the medial phalanx of the third finger of non-preferred as the active site, while the reference site was a point two thirds of the distance from the wrist to

**3.2 Alternately (simultaneous recording at different skin sites) recording SC** 

Articles presented here are associated with authors, who tried to measure EDA parameters simultaneously, but not at the same skin site, i.e., EDA parameters were

Wilcott [29] had recorded SR (SC) and SP simultaneously contralateral from the left and right-palm-upper-arm locations to study the correlation between both these EDA parameters. He obtained significant correlations between the SC and the SP amplitudes. Regarding the possibility of recording EDA parameters at the same skin site, Wilcott claimed that simultaneous measurement of EDA parameters is impossible and stated that "As it is of course not possible to record the two types of bioelectrical activity (e.g., SC and SP) from the same skin area simultaneously, they were recorded alternately from the same skin area and simultaneously from differ-

To elucidate mechanisms underlying the appearance of the diphasic potential (SP) curve, SC and SP simultaneously from the palm and the dorsum of the hand were recorded by Yokota et al. [30]. SC and SP simultaneously from the palm and the dorsum of the hand were recorded by Yokota et al. [30]. Sequence recording of SC and SP was applied so as to enable a comparison of the results with each other. When the SP was recorded simultaneously with SC from different parts of the same palm, diphasic potential curve changes usually corresponded to larger resistance

According to Edelberg and Burch [31], both SC and SP are widely used as indicators of autonomic activity in psychological and pharmacological investigations, but the many fundamental controversies to be found in the literature testify to the questionable reliability of these measures [31]. In addition to the external stimuli and central excitatory state, various outside factors constitute a third category of variables (skin temperature, current density, electrode composition and size, contact medium, and electronic circuitry) affecting SP and SC responses. These factors are difficult to control, when comparisons between SP and SC are to be made separately (recording each of which at certain time). However, when they are compared simultaneously, effect of such variables can

Relations between simultaneously recorded SC and SP changes are obtained at high and low levels of bodily excitation by Darrow [22]. Electrodes were connected to the palm and the wrist of both hands in order to simultaneously record SC and SP

**102**

Burstein et al. [32] reported simultaneous recording of SR (SC) and SP responses generated by different psychological stimuli. The aim was to show effects of such stimuli on responses of both EDA parameters and to determine the significance of the different wave forms of skin potential [32]. SC responses were recorded from middle and index fingers of the left hand, and SP responses were recorded from the right ear lobe and the right index finger. They found that both SC and SP are highly effective in assessing differential emotional responses. However, total SP yields slightly more significant results than does the SC measure. They finally suggested that the skin potential response merits further investigation because the qualitative differences in its wave forms may be of special significance [32].

Hupka and Levinger [33] recorded palmar SC and SP simultaneously with nonpolarizing electrodes, connected to the thenar eminence of the right and left palm and on the dorsal right or left forearm. Authors aimed to investigate whether the SPR negativity remains a constant correlation with the SCR during different conditions of passivity and motor activity [33].

SC and SP were recorded simultaneously from opposite hands during a stress period and a subsequent prolonged relaxation by Lykken et al. [34]. Their aim was to investigate certain interrelationships between concurrent measures of SC and SP through employing a simple equivalent circuit model of steady-state electrodermal phenomena [34].

The correlation of change measures and prestimulus level in SC and SP and the amount of correlation between SP and SC measures were studies by Gaviria et al. [35]. SP and SC were recorded in a sequence at two different skin sites.

The effect of repeated stimuli on reader and nonreader child with respect to physiological orienting response patterns in the autonomic nervous system was investigated by Hunter et al. [36]. Authors aimed to fined difference between those two groups through simultaneously recording SC and SP. For SC recording electrodes were placed to the volar pads of the first and third fingers, and for SP recordings the active electrode was placed on the volar pad of the middle finger, and the reference electrode was placed on the forearm; thus both SC and SP are recorded simultaneously at two different skin sites [36].

In order to investigate possible differences between healthy subjects and unhealthy (schizophrenic) subjects, Patterson and Venables [37] recorded SC and SP at the same time but at two different skin sites by two different measuring systems. Electrodes for SC recording were attached on the medial phalanges of the first and second fingers of both hands and for SP were placed on the hypothenar eminence of the right hand and an abraded surface of the right arm [37].

The validity of SC and SP for preliminary cystic fibrosis screening has been demonstrated by Williamson et al. [38]. Electrodes for SC recording were attached to the palmar surface of the fingers. For the measurements of SP, the active electrode was being placed on the palmar surface of the distal middle phalanx of the hand [38]. Discriminant analysis using the two best EDA measures (SC and SP) for assignment of experimental group membership yielded 92.7% correct classification of the actual group membership. However, both SP and SC recordings were necessary to obtain such accuracy, since reclassifications of participants by discriminant analysis using only the six SC or the six SP measures lowered the percentage of correct classifications to 77% for SC and 86% for SP. Authors stated that it would simplify clinical procedures to use only the SP or only the SC measures to distinguish between group (health and unhealthy) subjects, because only one hand would be recorded and scored [38]. However, according to their results, recording more than one EDA parameters at the same time would lead to more meaningful results.

Collet et al. [39] showed neutral and emotionally loaded pictures to some test subjects in order to evoke happiness, surprise, anger, fear, sadness, and disgust.

The EDA signals measured were SC, SP, and SR. For EDA recordings electrodes were placed at different skin sites. For SC measurement electrodes were attached to the second phalanx of the fourth and fifth digits of the non-dominant hand; for SP active electrode was attached to the hypothenar eminence, and the reference electrode was attached to the wrist, and finally for SR recording, electrodes were placed on the second phalanx of the index and the third digit of the non-dominant hand [39].

SR (SC) and SP and some other physiological parameters were recorded simultaneously at various skin sites by Ismaili et al. [40], to analyze the relationship between self-report hedonic evaluations and the physiological expression of emotion in response to odorants. Second phalanx of the index and the third digit of the non-dominant hand were selected for SC recording. For SP recording, the active electrode was placed on the hypothenar eminence, and the reference electrode was placed 10 cm higher on the wrist.

Shiihara et al. [41] examined the validity of long-term SC recordings by comparing such recordings with simultaneously recorded SP at two different skin sites. SC was recorded through placing electrode on the middle phalanx of the second and fourth fingers, and SP was recorded via attaching electrodes between the thenar eminence of the palm and the lower portion of the upper arm. Both EDA parameters were recorded simultaneously during sleep.

In a recent study, SC and SP have been recorded simultaneously at different skin sites to evaluate the mental workload during driving by Kajiwara [42]. Author stated that in order to simultaneously measure the SC and SP, the SC was measured on the left arm, and the SP was measured on the right arm.

### **3.3 Simultaneous measurement of SC and SP or SS at the same skin sites**

As noted, earlier studies such as [29] have claimed that simultaneous measurements of EDA parameters are impossible. However, this hypothesis was later criticized and lost ground due to new explanations and newest trends and techniques.

Montagu in [43] performed measurements (SC and SP) on the same skin site simultaneously and continuously through the same pair of electrodes. Montagu aimed to study effects of variety of conditions (different external stimuli) on the simultaneous recordings of SC and SP at a single reacting area.

Grimnes [44] performed DC SP or SC, AC SC, and skin capacitance (i.e., SS) measurements on the same skin site simultaneously by using the three-electrode system. Author pointed out that the examination of the influence of sweat duct cannot be done without also recording the parallel values of the skin admittance. Also he reported that the sensitivity of the DC conductance to a certain reflex intensity is larger than that of the AC SC.

Qiao et al. [45] developed a method for simultaneously recording SC and SS at the same skin site via using a three-electrode lock-in amplifier measuring system. It is indicated that the use of AC excitation is necessary for recording SS.

The exogenous (SC) and endogenous (SP) responses in order to acquire a better understanding of the underlying mechanisms were compared by Jabbari et al. [46]. Both SCR and SPR were simultaneously recorded in the palms using the same electrodes. Authors reported independent information and correlation between SC and SP.

Grimnes et al. [47] developed a special recording system for combining SC with SP recordings from an active electrode at a palmar site together with a large indifferent electrode connected to a physiological NaCl bath in which the forearm was immersed. Their recording system used a small AC current, enabling the SC and SP to be recorded simultaneously at the same site. Authors reported that it is possible

**105**

**Figure 2.**

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

and the resistance of the recording electrode [47].

matic, SS could not be measured.

waveforms [9].

underarm.

current sink electrode (CE).

to measure the SP and skin AC SC simultaneously at the same skin site in a lownoise system. Authors pointed out that both the measuring systems that are used by Grimnes [44] and Montagu [43] had the demerit that the recording electrode must supply the necessary charge/discharge current to the blocking capacitor with changing DC voltages. This also introduced a time constant specified by the capacitance

**3.4 Simultaneous measurement of SC, SP, and SS at the same skin sites**

Pabst et al. [48] designed a measuring system for simultaneously recording AC SC and DC SC at the same skin site and same electrode. Authors aimed to examine the similarities and differences between the AC and DC methods of EDA recording under the same conditions. The measuring system consisted of two bipolar electrodes, which were placed at the thenar and hypothenar sites of the dominant hand.

This type of recording must be done with AC exosomatic, since with DC exoso-

Tronstad et al. [8] used a new method to record SC, SP, and SS simultaneously at the same electrode. Their aim was to investigate the difference between waveform of SC and SP in a new way by comparing their temporal peak differences. It was a PC-based EDA recording system for simultaneous recording of skin admittance (SC and SS) and SP at the same electrode. For recoding EDA parameters, three electrodes were employed, a measuring electrode placed on hypothenar, a reference electrode placed on apex of elbow, and a current sink electrode placed on the

The effect of some external stimuli on simultaneous recordings of SC, SP, and SS at the same skin site has been investigated by Bari et al. [49]. Authors confirmed that the three EDA parameters (SC, SP, and S) could be measured simultaneously under the same electrodes. Each of such EDA parameters showed different wave

**Figure 2** shows an example of a setup for simultaneously measuring SP, SC, and SS at the same skin site. It is a PC-based EDA system for recording EDA by means of skin admittance and SP simultaneously at the same electrode on the same skin site. It consists of one measuring electrode (ME), one reference electrode (RE), and a

forms depending on their relation with the tissue under investigation.

*An example of a setup for simultaneously recording SP, SC, and SS at the same skin site.*

Jabbari et al. [9] developed a measuring system where DC current was replaced by a small AC current. They aimed to record SC, SP, and SS simultaneously at the same skin site. Three electrodes were placed to the skin, two measuring electrodes and one reference electrode [9]. They confirmed that it is possible to measure SP and skin AC SC simultaneously at the same skin site. In addition, they regarded recording SP and SC simultaneously with the same electrode as significant because of the often large skin site dependence of levels and response *Electrodermal Activity: Simultaneous Recordings DOI: http://dx.doi.org/10.5772/intechopen.89025*

*Electrochemical Impedance Spectroscopy*

placed 10 cm higher on the wrist.

larger than that of the AC SC.

between SC and SP.

eters were recorded simultaneously during sleep.

on the left arm, and the SP was measured on the right arm.

simultaneous recordings of SC and SP at a single reacting area.

hand [39].

The EDA signals measured were SC, SP, and SR. For EDA recordings electrodes were placed at different skin sites. For SC measurement electrodes were attached to the second phalanx of the fourth and fifth digits of the non-dominant hand; for SP active electrode was attached to the hypothenar eminence, and the reference electrode was attached to the wrist, and finally for SR recording, electrodes were placed on the second phalanx of the index and the third digit of the non-dominant

SR (SC) and SP and some other physiological parameters were recorded simultaneously at various skin sites by Ismaili et al. [40], to analyze the relationship between self-report hedonic evaluations and the physiological expression of emotion in response to odorants. Second phalanx of the index and the third digit of the non-dominant hand were selected for SC recording. For SP recording, the active electrode was placed on the hypothenar eminence, and the reference electrode was

Shiihara et al. [41] examined the validity of long-term SC recordings by comparing such recordings with simultaneously recorded SP at two different skin sites. SC was recorded through placing electrode on the middle phalanx of the second and fourth fingers, and SP was recorded via attaching electrodes between the thenar eminence of the palm and the lower portion of the upper arm. Both EDA param-

In a recent study, SC and SP have been recorded simultaneously at different skin sites to evaluate the mental workload during driving by Kajiwara [42]. Author stated that in order to simultaneously measure the SC and SP, the SC was measured

As noted, earlier studies such as [29] have claimed that simultaneous measurements of EDA parameters are impossible. However, this hypothesis was later criticized and lost ground due to new explanations and newest trends and techniques. Montagu in [43] performed measurements (SC and SP) on the same skin site simultaneously and continuously through the same pair of electrodes. Montagu aimed to study effects of variety of conditions (different external stimuli) on the

Grimnes [44] performed DC SP or SC, AC SC, and skin capacitance (i.e., SS) measurements on the same skin site simultaneously by using the three-electrode system. Author pointed out that the examination of the influence of sweat duct cannot be done without also recording the parallel values of the skin admittance. Also he reported that the sensitivity of the DC conductance to a certain reflex intensity is

Qiao et al. [45] developed a method for simultaneously recording SC and SS at the same skin site via using a three-electrode lock-in amplifier measuring system. It

Grimnes et al. [47] developed a special recording system for combining SC with SP recordings from an active electrode at a palmar site together with a large indifferent electrode connected to a physiological NaCl bath in which the forearm was immersed. Their recording system used a small AC current, enabling the SC and SP to be recorded simultaneously at the same site. Authors reported that it is possible

The exogenous (SC) and endogenous (SP) responses in order to acquire a better understanding of the underlying mechanisms were compared by Jabbari et al. [46]. Both SCR and SPR were simultaneously recorded in the palms using the same electrodes. Authors reported independent information and correlation

is indicated that the use of AC excitation is necessary for recording SS.

**3.3 Simultaneous measurement of SC and SP or SS at the same skin sites**

**104**

to measure the SP and skin AC SC simultaneously at the same skin site in a lownoise system. Authors pointed out that both the measuring systems that are used by Grimnes [44] and Montagu [43] had the demerit that the recording electrode must supply the necessary charge/discharge current to the blocking capacitor with changing DC voltages. This also introduced a time constant specified by the capacitance and the resistance of the recording electrode [47].

Pabst et al. [48] designed a measuring system for simultaneously recording AC SC and DC SC at the same skin site and same electrode. Authors aimed to examine the similarities and differences between the AC and DC methods of EDA recording under the same conditions. The measuring system consisted of two bipolar electrodes, which were placed at the thenar and hypothenar sites of the dominant hand.

#### **3.4 Simultaneous measurement of SC, SP, and SS at the same skin sites**

This type of recording must be done with AC exosomatic, since with DC exosomatic, SS could not be measured.

Jabbari et al. [9] developed a measuring system where DC current was replaced by a small AC current. They aimed to record SC, SP, and SS simultaneously at the same skin site. Three electrodes were placed to the skin, two measuring electrodes and one reference electrode [9]. They confirmed that it is possible to measure SP and skin AC SC simultaneously at the same skin site. In addition, they regarded recording SP and SC simultaneously with the same electrode as significant because of the often large skin site dependence of levels and response waveforms [9].

Tronstad et al. [8] used a new method to record SC, SP, and SS simultaneously at the same electrode. Their aim was to investigate the difference between waveform of SC and SP in a new way by comparing their temporal peak differences. It was a PC-based EDA recording system for simultaneous recording of skin admittance (SC and SS) and SP at the same electrode. For recoding EDA parameters, three electrodes were employed, a measuring electrode placed on hypothenar, a reference electrode placed on apex of elbow, and a current sink electrode placed on the underarm.

The effect of some external stimuli on simultaneous recordings of SC, SP, and SS at the same skin site has been investigated by Bari et al. [49]. Authors confirmed that the three EDA parameters (SC, SP, and S) could be measured simultaneously under the same electrodes. Each of such EDA parameters showed different wave forms depending on their relation with the tissue under investigation.

**Figure 2** shows an example of a setup for simultaneously measuring SP, SC, and SS at the same skin site. It is a PC-based EDA system for recording EDA by means of skin admittance and SP simultaneously at the same electrode on the same skin site. It consists of one measuring electrode (ME), one reference electrode (RE), and a current sink electrode (CE).

**Figure 2.** *An example of a setup for simultaneously recording SP, SC, and SS at the same skin site.*
