# Los primeros días de la actividad electrodérmica

Henrique Sequeira, Pascal Deren, Bernard Maitte

► To cite this version:

Henrique Sequeira, Pascal Deren, Bernard Maitte. Los primeros días de la actividad electrodérmica. Anales de Psicología, 2021, Anales de Psicología, 37 (3), p.406-411. 10.6018/analesps.483051. hal-04453246

HAL Id: hal-04453246

https://hal.univ-lille.fr/hal-04453246

Submitted on 14 Feb 2024

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>
<figure><img src="image_1.png" /></figure>

# The early days of electrodermal activity

Henrique Sequeira<fnref n="1" />,², Pascal Deren² and Bernard Maitte²

1 Université Lille, CNRS, UMR 9193 - SCALab - Sciences Cognitives et Sciences Affectives, F-59000 Lille (France).

2 Université Lille, Faculté des Sciences et des Technologies, UFR de Physique, F-59655, Villeneuve d'Ascq (France).

**Título:** Los primeros días de la actividad electrodérmica.

**Resumen:** Este artículo enfatiza las etapas principales del descubrimiento de uno de los marcadores autónomos más destacados de las expresiones mentales, la actividad electrodérmica (EDA). La contribución de las escuelas de fisiología francesa y alemana, orientada por las necesidades clínicas y el deseo de conocer más sobre los mecanismos fisiológicos, constituyen las primeras raíces de dicha actividad. En este marco, Féré y Tarchanoff, descubridores franceses y rusos respectivamente, establecieron el vínculo entre la actividad mental y la EDA, por un lado, y sentaron las bases metodológicas de la utilización moderna de este neuromarcador, por el otro. Este legado, asociado con medidas neuronales centrales, promete un futuro en expansión en neuropsicología, psicopatología, neurología, criminología y en neurociencia cognitiva y afectiva.

**Palabra clave:** Actividad electrodérmica. Conductancia cutánea. Potencial cutáneo. Sistema nervioso autónomo. Emoción. Féré. Tarchanoff.

**Abstract:** This paper emphasises main steps of the discovery of one of the most salient autonomic markers of mind expressions, the electrodermal activity (EDA). The contribution of French and German schools of physiology, aimed by clinical needs and the desire to know further about physiological mechanisms, constitutes the very early roots of such activity. In this frame, Féré and Tarchanoff, respectively a French and a Russian discoverers, established the link between mind activity and the EDA on the one hand and laid the methodological foundations of modern utilisation of this neuromarker on the other hand. This heritage, associated with central neural measures, is promised to an expanding future in neuropsychology, psychopathology, neurology, criminology and in cognitive and affective neuroscience.

**Keywords:** Electrodermal activity. Skin conductance. Skin potential. Autonomic nervous system. Emotion. Féré. Tarchanoff.

## Introduction

The electrodermal activity (EDA) is currently considered as one of the most important neurophysiological indices of emotional and cognitive functions<fnref n="1" />. EDA corresponds to electrical skin variations related to the sweat glands functioning and has been used as a reliable physiological indicator of central activations. The very early electrodermal recordings were carried out at the end of the XIXth century by Féré and Tarchanoff, respectively a French and a Russian researchers. Their experiments, conducted independently, have created the foundations of modern recording techniques of EDA. The contribution of these researchers also revealed the strong scientific interactions through European physiological institutions, particularly involved to find very early markers to reliably measure mental functions. Before considering the early roots of the EDA, we recall below some characteristics underlying this physiological activity as they are known in our days.

## 1. The electrodermal activity: An autonomic window on the mind

The EDA is the electrical expression of the activity developed by the eccrine sweat glands, mainly located in deep layers of palmar and plantar skin. These glands are under the exclusive control of the sympathetic branch of the autonomic nervous system. Through the sympathetic control, sweat production and consequent EDA variations express activations produced by brain areas. EDA thus reveals high functions subtended by the brain functioning, a sort of body signature allowing access to the mind space.

In experimental practice, EDA is usually recorded, thanks to different techniques, like dermal conductance or potential, and using electrodes placed in contact with the skin of index and middle fingers. Following recommendations of Fowles et al. (1981) and Boucsein et al. (2012), the EDA is generally recorded as cutaneous conductance variations and expressed in terms of electrodermal responses, known as skin conductance responses (SCRs; see Fig 1A-B). The amplitude of SCRs is strongly sensitive to activations generated by the central nervous system and transmitted to eccrine sweat glands by sympathetic fibers. Consequently, SCRs characteristics reveal mind functions requiring central activations like novelty, attention, action, memory or emotion. In this frame, SCRs are now recognized as a good marker of the cerebral impact of emotion on the body. Indeed, during emotional stimulation, SCRs amplitude increases with the subjective assessment of the emotional activation of the stimulus, regardless of emotional valence (Lang et al., 1993; Bradley et al., 2001a). Therefore, SCRs constitute a reliable and robust index of the somato-visceral impact of brain activations engaged in the processing of emotional information (Sequeira et al., 2009).

<footnote>* Correspondence address [Dirección para correspondencia]:
Henrique Sequeira. Univ. Lille, CNRS, UMR 9193 - SCALab - Sciences Cognitives et Sciences Affectives, F-59000 Lille (France).
E-mail: Henrique.Sequeira@univ-lille.fr
(Article received: 9-6-2021, revised: 22-6-2021, accepted: 4-7-2021)</footnote>

<footnote n="1">1 Parts of this paper were published in "Sequeira, H., Deren, P., Maitte, B. (2016). The Electrodermal Activity: Looking for French-Russian contributions. In J.C. Dupont, J.G. Barbara, E.I. Kolchinsky and M. Loskutova (Eds.), *Russian, French, German links in Embriology, Physiology and Medicine* (pp. 169-181). Hermann".</footnote>
<figure><img src="image_2.png" /></figure>

# The early days of electrodermal activity

Henrique Sequeira<fnref n="1" />,², Pascal Deren² and Bernard Maitte²

¹ Université Lille, CNRS, UMR 9193 - SCALab - Sciences Cognitives et Sciences Affectives, F-59000 Lille (France).

² Université Lille, Faculté des Sciences et des Technologies, UFR de Physique, F-59655, Villeneuve d'Ascq (France).

**Título:** Los primeros días de la actividad electrodérmica.

**Resumen:** Este artículo enfatiza las etapas principales del descubrimiento de uno de los marcadores autónomos más destacados de las expresiones mentales, la actividad electrodérmica (EDA). La contribución de las escuelas de fisiología francesa y alemana, orientada por las necesidades clínicas y el deseo de conocer más sobre los mecanismos fisiológicos, constituyen las primeras raíces de dicha actividad. En este marco, Féré y Tarchanoff, descubridores franceses y rusos respectivamente, establecieron el vínculo entre la actividad mental y la EDA, por un lado, y sentaron las bases metodológicas de la utilización moderna de este neuromarcador, por el otro. Este legado, asociado con medidas neuronales centrales, promete un futuro en expansión en neuropsicología, psicopatología, neurología, criminología y en neurociencia cognitiva y afectiva.

**Palabra clave:** Actividad electrodérmica. Conductancia cutánea. Potencial cutáneo. Sistema nervioso autónomo. Emoción. Féré. Tarchanoff.

**Abstract:** This paper emphasises main steps of the discovery of one of the most salient autonomic markers of mind expressions, the electrodermal activity (EDA). The contribution of French and German schools of physiology, aimed by clinical needs and the desire to know further about physiological mechanisms, constitutes the very early roots of such activity. In this frame, Féré and Tarchanoff, respectively a French and a Russian discoverers, established the link between mind activity and the EDA on the one hand and laid the methodological foundations of modern utilisation of this neuromarker on the other hand. This heritage, associated with central neural measures, is promised to an expanding future in neuropsychology, psychopathology, neurology, criminology and in cognitive and affective neuroscience.

**Keywords:** Electrodermal activity. Skin conductance. Skin potential. Autonomic nervous system. Emotion. Féré. Tarchanoff.

## Introduction

The electrodermal activity (EDA) is currently considered as one of the most important neurophysiological indices of emotional and cognitive functions<fnref n="1" />. EDA corresponds to electrical skin variations related to the sweat glands functioning and has been used as a reliable physiological indicator of central activations. The very early electrodermal recordings were carried out at the end of the XIXth century by Féré and Tarchanoff, respectively a French and a Russian researchers. Their experiments, conducted independently, have created the foundations of modern recording techniques of EDA. The contribution of these researchers also revealed the strong scientific interactions through European physiological institutions, particularly involved to find very early markers to reliably measure mental functions. Before considering the early roots of the EDA, we recall below some characteristics underlying this physiological activity as they are known in our days.

## 1. The electrodermal activity: An autonomic window on the mind

The EDA is the electrical expression of the activity developed by the eccrine sweat glands, mainly located in deep layers of palmar and plantar skin. These glands are under the exclusive control of the sympathetic branch of the autonomic nervous system. Through the sympathetic control, sweat production and consequent EDA variations express activations produced by brain areas. EDA thus reveals high functions subtended by the brain functioning, a sort of body signature allowing access to the mind space.

In experimental practice, EDA is usually recorded, thanks to different techniques, like dermal conductance or potential, and using electrodes placed in contact with the skin of index and middle fingers. Following recommendations of Fowles et al. (1981) and Boucsein et al. (2012), the EDA is generally recorded as cutaneous conductance variations and expressed in terms of electrodermal responses, known as skin conductance responses (SCRs; see Fig 1A-B). The amplitude of SCRs is strongly sensitive to activations generated by the central nervous system and transmitted to eccrine sweat glands by sympathetic fibers. Consequently, SCRs characteristics reveal mind functions requiring central activations like novelty, attention, action, memory or emotion. In this frame, SCRs are now recognized as a good marker of the cerebral impact of emotion on the body. Indeed, during emotional stimulation, SCRs amplitude increases with the subjective assessment of the emotional activation of the stimulus, regardless of emotional valence (Lang et al., 1993; Bradley et al., 2001a). Therefore, SCRs constitute a reliable and robust index of the somato-visceral impact of brain activations engaged in the processing of emotional information (Sequeira et al., 2009).

<footnote>* Correspondence address [Dirección para correspondencia]:
Henrique Sequeira. Univ. Lille, CNRS, UMR 9193 - SCALab - Sciences Cognitives et Sciences Affectives, F-59000 Lille (France).</footnote>

<footnote>E-mail: Henrique.Sequeira@univ-lille.fr</footnote>

<footnote>(Article received: 9-6-2021, revised: 22-6-2021, accepted: 4-7-2021)</footnote>

<footnote n="1">1 Parts of this paper were published in "Sequeira, H., Deren, P., Maitte, B. (2016). The Electrodermal Activity: Looking for French-Russian contributions. In J.C. Dupont, J.G. Barbara, E.I. Kolchinsky and M. Loskutova (Eds.), *Russian, French, German links in Embriology, Physiology and Medicine* (pp. 169-181). Hermann".</footnote>
In a more general way, the EDA is considered as a very useful physiological activity, highly sensitive to any content with a specific signification for an individual. For this reason, the EDA constitutes one of the best physiological *windows* of brain activity. Indeed, for more than a century, the EDA has been used as a tentative neural index of cognitive and emotional functions in healthy and pathological individuals. In this frame, the EDA recording has been extensively recorded in rats, cats, monkeys and humans (see Sequeira and Roy, 1997 for a review). Thus, the generalized utilization of the EDA among modern neuromarkers in the field of neuroscience (e.g.), greatly increased the researcher's interest to elucidate and understand early steps of electrodermal recordings.

## 2. Early observations on electrical skin variations

The very early history of electrodermal activity begins probably with experiments performed by DuBois-Reymond (1849), in Germany; participants put either hands or feet into a zinc sulfate solution and this author observed an electrical current going from the limb at rest to the other one which was voluntary contracted. He explained this phenomenon as corresponding to muscle action potentials. Three decades later, Hermann & Luchsinger (1878), carried out a first experiment in which they showed a link between the sweat gland activity and the existence of a current flow, recorded through the skin cat's paw. In Paris, one year later, Vigouroux (1879) observed that different doses of anesthesia modified the psychological reactivity and induced skin current variations in hysterical patients. This author explained such variations as being due to the vascular conductivity. Also in humans, Hermann (1882) described skin currents, particularly intense in areas able to easily produce sweating, like palms and fingers, when participants execute movements similar to those executed by subjects of Dubois-Reymond, in 1849. On the basis of this experimental paradigm, Hermann, for the first time, proposed the implication of sweat glands to explain variations of skin currents. In fact, such currents were classically considered as the result of muscular or vascular activities, which could be modulated by the autonomic control of blood flow. Thus, the Herman's proposition about the potential role of sweat glands was an essential step in the way to link these glands to electrodermal phenomena; however, at this stage, proofs linking sweat glands to the EDA and the EDA to brain functions remained to be found. In this frame, experimental arguments brought by Féré (1888) and Tarchanoff (1889) will constitute a determinant contribution.

## 3. Féré's contribution: Solving clinical issues

In Paris, the medical environment, sustained since Cabanis (1757-1808) and afterwards through Pinel (1745-1826), de-

veloped close links between emotional shocks and mental disorders. However, after 1870's, new theoretical and therapeutic trends appear at the hospital "La Salpêtrière", still in Paris. Indeed, at that period, Charcot (1825-1893) was appointed as the new director (1862) of Salpêtrière's clinical department; between 1881 and 1887, Féré (1852-1907) became member of the same department where he presented his medical doctorate, in 1882. During this period, Charcot's greatly influenced Féré's scientific orientations to the psychological field, such influence mostly corresponding to the idea that the mental pathology was favored by emotional vulnerability. Concomitantly, there were significant scientific progresses related to the physiology of emotions. Firstly, there was an increasing transfer of electrical phenomena knowledge from the physics to the physiology; this will gave rise to a new discipline, the electrophysiology, which became an essential tool for early physiological and psychophysiological explorations. Secondly, at the same time, Bernard (1813-1878) was looking for *physiology of emotions*, through researches about the *autonomic nervous system*.

### 3.1. Charcot's influence at «La Salpêtrière»

The Charcot's influence at «La Salpêtrière» was marked by a positivist attitude by which the Psychology was considered as a branch of Physiology. In this context, the Charcot's research program, mainly focusing on hysteria, was based on two main orientations. The first postulates that emotions could induce organic lesions and, by this way, generate mental disorders like hysteria. Consequently, it was necessary to find objective markers revealing the mental impact of emotions and, finally, to be able to classify different types of patients. In coherence with this orientation, Charcot asked Féré to evaluate available knowledge about emotions and to quantify the impact of physical and emotional stimulations in the genesis of mental pathology, particularly hysteria. The second idea was based on the belief that electrophysiological techniques could be used as interesting means for diagnosis and therapeutics. Thus, both ideas will orient Féré's work and future issues about the discovery of skin electrical variations to different kind of stimulations.

### 3.2. Féré's approach: Emotions and electrical skin variations

In this context, enriched by recent developments of electrophysiological techniques, the Féré's approach was however limited by conceptions still strongly linked to the clinical practice. Indeed, he considered that there was no need of statistical procedures because clinical facts present a high degree of variability and are inherent to individuals and specific circumstances. In addition, Féré did not believe on the possibility and interest to transfer data from normal subjects to patients. Despite these methodological restrictions, Féré's environment presented a rich variety of technical tools to go further on physiological exploration, like dynamometer,
In a more general way, the EDA is considered as a very useful physiological activity, highly sensitive to any content with a specific signification for an individual. For this reason, the EDA constitutes one of the best physiological *windows* of brain activity. Indeed, for more than a century, the EDA has been used as a tentative neural index of cognitive and emotional functions in healthy and pathological individuals. In this frame, the EDA recording has been extensively recorded in rats, cats, monkeys and humans (see Sequeira and Roy, 1997 for a review). Thus, the generalized utilization of the EDA among modern neuromarkers in the field of neuroscience (e.g.), greatly increased the researcher's interest to elucidate and understand early steps of electrodermal recordings.

## 2. Early observations on electrical skin variations

The very early history of electrodermal activity begins probably with experiments performed by DuBois-Reymond (1849), in Germany; participants put either hands or feet into a zinc sulfate solution and this author observed an electrical current going from the limb at rest to the other one which was voluntary contracted. He explained this phenomenon as corresponding to muscle action potentials. Three decades later, Hermann & Luchsinger (1878), carried out a first experiment in which they showed a link between the sweat gland activity and the existence of a current flow, recorded through the skin cat's paw. In Paris, one year later, Vigouroux (1879) observed that different doses of anesthesia modified the psychological reactivity and induced skin current variations in hysterical patients. This author explained such variations as being due to the vascular conductivity. Also in humans, Hermann (1882) described skin currents, particularly intense in areas able to easily produce sweating, like palms and fingers, when participants execute movements similar to those executed by subjects of Dubois-Reymond, in 1849. On the basis of this experimental paradigm, Hermann, for the first time, proposed the implication of sweat glands to explain variations of skin currents. In fact, such currents were classically considered as the result of muscular or vascular activities, which could be modulated by the autonomic control of blood flow. Thus, the Herman's proposition about the potential role of sweat glands was an essential step in the way to link these glands to electrodermal phenomena; however, at this stage, proofs linking sweat glands to the EDA and the EDA to brain functions remained to be found. In this frame, experimental arguments brought by Féré (1888) and Tarchanoff (1889) will constitute a determinant contribution.

## 3. Féré's contribution: Solving clinical issues

In Paris, the medical environment, sustained since Cabanis (1757-1808) and afterwards through Pinel (1745-1826), de-

veloped close links between emotional shocks and mental disorders. However, after 1870's, new theoretical and therapeutic trends appear at the hospital "La Salpêtrière", still in Paris. Indeed, at that period, Charcot (1825-1893) was appointed as the new director (1862) of Salpêtrière's clinical department; between 1881 and 1887, Féré (1852-1907) became member of the same department where he presented his medical doctorate, in 1882. During this period, Charcot's greatly influenced Féré's scientific orientations to the psychological field, such influence mostly corresponding to the idea that the mental pathology was favored by emotional vulnerability. Concomitantly, there were significant scientific progresses related to the physiology of emotions. Firstly, there was an increasing transfer of electrical phenomena knowledge from the physics to the physiology; this will gave rise to a new discipline, the electrophysiology, which became an essential tool for early physiological and psychophysiological explorations. Secondly, at the same time, Bernard (1813-1878) was looking for *physiology of emotions*, through researches about the *autonomic nervous system*.

### 3.1. Charcot's influence at «La Salpêtrière»

The Charcot's influence at «La Salpêtrière» was marked by a positivist attitude by which the Psychology was considered as a branch of Physiology. In this context, the Charcot's research program, mainly focusing on hysteria, was based on two main orientations. The first postulates that emotions could induce organic lesions and, by this way, generate mental disorders like hysteria. Consequently, it was necessary to find objective markers revealing the mental impact of emotions and, finally, to be able to classify different types of patients. In coherence with this orientation, Charcot asked Féré to evaluate available knowledge about emotions and to quantify the impact of physical and emotional stimulations in the genesis of mental pathology, particularly hysteria. The second idea was based on the belief that electrophysiological techniques could be used as interesting means for diagnosis and therapeutics. Thus, both ideas will orient Féré's work and future issues about the discovery of skin electrical variations to different kind of stimulations.

### 3.2. Féré's approach: Emotions and electrical skin variations

In this context, enriched by recent developments of electrophysiological techniques, the Féré's approach was however limited by conceptions still strongly linked to the clinical practice. Indeed, he considered that there was no need of statistical procedures because clinical facts present a high degree of variability and are inherent to individuals and specific circumstances. In addition, Féré did not believe on the possibility and interest to transfer data from normal subjects to patients. Despite these methodological restrictions, Féré's environment presented a rich variety of technical tools to go further on physiological exploration, like dynamometer,
pneumograph, tensiometer, plethysmograph, etc. In particu-
lar, Féré could use until 15 techniques to identify physiologi-
cal markers of emotions.

In this frame, the first contribution of Féré linking emo-
tions and body electrical activity was published in 1888 (So-
ciété de Biologie, January 14th, 1888: *Note sur des modifications
de la tension électrique, dans le corps humain*). In this pioneer pub-
lication, he wrote: «...local modifications of tension under the influ-
ence of peripheral excitations or emotions ...this supposes that the or-
ganism can produce electrical activity». This publication will origi-
nate a sustained debate about the electrical nature of record-
ings carried out at skin surface. Vigouroux, in a paper pub-
lished one month later (Société de Biologie, February 11th,
1888) assumed a clear opposition to the explanation based in
the electrical nature of recordings carried out at skin surface:
«... the existence of electrical charges at the skin surface remains to be
demonstrated ...». In the opposite direction, and in the same
publication issue, D'Arsonval (Société de Biologie, February
11th, 1888) confirms, in spite of some critics, the reality of
electrical skin variations linked to sensory stimulations. Fi-
nally, in early March of the same year (Société de Biologie,
March 3rd, 1888: *Note sur des modifications de la résistance élec-
trique sous l'influence des excitations sensorielles et des émotions*), Féré
expressed, for the first time, the link between emotion and
electrical skin variations: «...several kind of sensory excitations
(visual, auditive, taste, olfaction) ... and emotion ... induce a rapid in-
crease of current conductance (at the skin level)...», even if such link
is not specific to emotion. At this stage, both Féré and
D'Arsonval tried to explain respectively new observed facts:
«...the organism is able to produce electrical activity» and
«...excitation modifies the hygrometric state of the skin». Here begins
the idea of promising relationships between emotion, sweat-
ing and electrical skin variations.

4. Tarchanoff's contribution: Exploring physi-
ological mechanisms

Tarchanoff was born (1846) in Tbilissi (Georgia) and ap-
pears as a highly colored personage. For instance, in the sci-
entific literature, his name had been written as thirteen dif-
ferent forms. He expressed an extended scientific curiosity,
developed rich relationships with most representative Euro-
pean laboratories in Physiology and was affiliated with the
French *Société de Biologie*.

Tarchanoff integrated the Russian team of Sechenof,
recognized as an expert in the field of electrophysiology, and
presented his medical doctorate in 1871. Some years later
(1877), Tarchanoff became the successor of Cyon at the
Chair of Physiology of the University of St. Petersburg. Dur-
ing next years, he travelled through Europe and visited
France, Germany and Italy. In particular, he met Dubois-
Reymond and Hermann in Berlin and Bernard in Paris and
developed local scientific collaborations, exploring several
aspects of the animal physiology related to batrachians,
birds, etc. In next years (1880-1886) his scientific interests

became more focused on human physiology (heart rate, etc.)
and psychology.

In 1889, appeared the first publication in «Message» (St.
Petersburg) in which the main discussed topic was similar to
that previously published by Féré, in 1888. Later in the same
year, Tarchanoff presented at the Société de Biologie (June
29th, 1889) a communication entitled: «Décharges électriques de
la peau de l'homme sous l'influence de l'excitation des organes des sens
et de différentes formes d'activité psychique». This title strongly
matches with that of Féré, presented at the same society on
March 3rd, 1888. Finally, a longer version of the Tarchanoff's
work was published in Pflüger's Archiv, in 1890.

It should be emphasized that Féré and Tarchanoff's pub-
lications differ significantly in terms of experimental ap-
proach. Contrary to Féré, Tarchanoff detailed experimental
steps, describing carefully the material used, like the galva-
nometer or recording electrodes. In the same vein, he chose
sensory (hot or cold water, pain, auditory, cry, taste, olfac-
tion) and mental (calculations, fear, joy, etc.) stimulations,
applied during experiments. In addition, given references are
mainly related to German authors (e.g. Hermann).

In conclusion, Féré and Tarchanoff followed different
ways to analyze and interpret similar physiological variations:
Féré, influenced by the French school, assumed a clinical
approach and explore individual observations; Tarchanoff,
influenced by German neurophysiology, adopted a scientific
approach, based on experimental steps. Despite such differ-
ences, both authors have been able to build a common and
an inseparable scientific heritage, based on relationships be-
tween nervous system activity, sweat glands and associated
skin electrical variations.

5. Two pioneers: A complementary heritage

Some years later (1892), Féré synthetized his work in a book entitled «Pathology of Emotions». Curiously, the recording of electrical variations of the skin appeared as a method among others and no reference was given to the Tarchanoff's work. Moreover, since that date, no more work was carried out by Féré on the electrophysiology of the skin and emotion. This could be explained by the fact that Féré had no specific competencies in electrophysiology. In addition, the installation of Janet as the official successor of Charcot at "La Salpétrière" and the new position of Féré at Bicêtre hospital (1887), certainly contributed to reinforce the early clinical interests of Féré. In this context, emotional states were analyzed as potential determinants of health modulations and electrical variations of skin henceforth considered as having a limited interest for clinical purposes.

Following the Tarchanoff's communication of 1889, in
which the Féré's work was not cited, there was no reaction
from the scientific community. This communication closed
the cycle of the methodological discovery of the EDA and
Tarchanoff followed other scientific orientations. Thus, ex-
cept a communication at the International Congress of Med-
icine (1894, Roma), related to music influences on skin elec-
pneumograph, tensiometer, plethysmograph, etc. In particu-
lar, Féré could use until 15 techniques to identify physiologi-
cal markers of emotions.

In this frame, the first contribution of Féré linking emo-
tions and body electrical activity was published in 1888 (So-
ciété de Biologie, January 14th, 1888: *Note sur des modifications
de la tension électrique, dans le corps humain*). In this pioneer pub-
lication, he wrote: «...local modifications of tension under the influ-
ence of peripheral excitations or emotions ...this supposes that the or-
ganism can produce electrical activity». This publication will origi-
nate a sustained debate about the electrical nature of record-
ings carried out at skin surface. Vigouroux, in a paper pub-
lished one month later (Société de Biologie, February 11th,
1888) assumed a clear opposition to the explanation based in
the electrical nature of recordings carried out at skin surface:
«... the existence of electrical charges at the skin surface remains to be
demonstrated ...». In the opposite direction, and in the same
publication issue, D'Arsonval (Société de Biologie, February
11th, 1888) confirms, in spite of some critics, the reality of
electrical skin variations linked to sensory stimulations. Fi-
nally, in early March of the same year (Société de Biologie,
March 3rd, 1888: *Note sur des modifications de la résistance élec-
trique sous l'influence des excitations sensorielles et des émotions*), Féré
expressed, for the first time, the link between emotion and
electrical skin variations: «...several kind of sensory excitations
(visual, auditive, taste, olfaction) ... and emotion ... induce a rapid in-
crease of current conductance (at the skin level)...», even if such link
is not specific to emotion. At this stage, both Féré and
D'Arsonval tried to explain respectively new observed facts:
«...the organism is able to produce electrical activity» and
«...excitation modifies the hygrometric state of the skin». Here begins
the idea of promising relationships between emotion, sweat-
ing and electrical skin variations.

4. Tarchanoff's contribution: Exploring physi-
ological mechanisms

Tarchanoff was born (1846) in Tbilissi (Georgia) and ap-
pears as a highly colored personage. For instance, in the sci-
entific literature, his name had been written as thirteen dif-
ferent forms. He expressed an extended scientific curiosity,
developed rich relationships with most representative Euro-
pean laboratories in Physiology and was affiliated with the
French *Société de Biologie*.

Tarchanoff integrated the Russian team of Sechenof,
recognized as an expert in the field of electrophysiology, and
presented his medical doctorate in 1871. Some years later
(1877), Tarchanoff became the successor of Cyon at the
Chair of Physiology of the University of St. Petersburg. Dur-
ing next years, he travelled through Europe and visited
France, Germany and Italy. In particular, he met Dubois-
Reymond and Hermann in Berlin and Bernard in Paris and
developed local scientific collaborations, exploring several
aspects of the animal physiology related to batrachians,
birds, etc. In next years (1880-1886) his scientific interests

became more focused on human physiology (heart rate, etc.)
and psychology.

In 1889, appeared the first publication in «Message» (St.
Petersburg) in which the main discussed topic was similar to
that previously published by Féré, in 1888. Later in the same
year, Tarchanoff presented at the Société de Biologie (June
29th, 1889) a communication entitled: «Décharges électriques de
la peau de l'homme sous l'influence de l'excitation des organes des sens
et de différentes formes d'activité psychique». This title strongly
matches with that of Féré, presented at the same society on
March 3rd, 1888. Finally, a longer version of the Tarchanoff's
work was published in Pflüger's Archiv, in 1890.

It should be emphasized that Féré and Tarchanoff's pub-
lications differ significantly in terms of experimental ap-
proach. Contrary to Féré, Tarchanoff detailed experimental
steps, describing carefully the material used, like the galva-
nometer or recording electrodes. In the same vein, he chose
sensory (hot or cold water, pain, auditory, cry, taste, olfac-
tion) and mental (calculations, fear, joy, etc.) stimulations,
applied during experiments. In addition, given references are
mainly related to German authors (e.g. Hermann).

In conclusion, Féré and Tarchanoff followed different
ways to analyze and interpret similar physiological variations:
Féré, influenced by the French school, assumed a clinical
approach and explore individual observations; Tarchanoff,
influenced by German neurophysiology, adopted a scientific
approach, based on experimental steps. Despite such differ-
ences, both authors have been able to build a common and
an inseparable scientific heritage, based on relationships be-
tween nervous system activity, sweat glands and associated
skin electrical variations.

5. Two pioneers: A complementary heritage

Some years later (1892), Féré synthetized his work in a book entitled «Pathology of Emotions». Curiously, the recording of electrical variations of the skin appeared as a method among others and no reference was given to the Tarchanoff's work. Moreover, since that date, no more work was carried out by Féré on the electrophysiology of the skin and emotion. This could be explained by the fact that Féré had no specific competencies in electrophysiology. In addition, the installation of Janet as the official successor of Charcot at "La Salpétrière" and the new position of Féré at Bicêtre hospital (1887), certainly contributed to reinforce the early clinical interests of Féré. In this context, emotional states were analyzed as potential determinants of health modulations and electrical variations of skin henceforth considered as having a limited interest for clinical purposes.

Following the Tarchanoff's communication of 1889, in
which the Féré's work was not cited, there was no reaction
from the scientific community. This communication closed
the cycle of the methodological discovery of the EDA and
Tarchanoff followed other scientific orientations. Thus, ex-
cept a communication at the International Congress of Med-
icine (1894, Roma), related to music influences on skin elec-
trical variations, Tarchanoff pursued known research activi-
ties in several topics (e.g. «...hallucinations ...in frogs ...»)
until 1900. In particular, since 1896, at St Petersburg, his new
scientific interest was focused on physiological effects of X-
ray, becoming a recognized specialist in this field.

Finally, although Tarchanoff initiated a significant tech-
nical background for the future of the electrodermal record-
ings, this contribution was just a step in his scientific career,
as the Féré's contribution was for his clinical practice. Both
pioneers died in 1907, ignoring thus the emerging interest of
their scientific contribution, applied to explore normal and
pathological mechanisms linked to the physiology and the
psychology.

5.1. Electrical variations of skin along the XXth cen-
tury

The period 1904-1909 brought new avenues for the
knowledge and applications of electrical variations of the
skin. This was due to the contribution of several authors:
Müller, Veraguth, Jung and Peterson. More precisely, the re-
birth of the interest for cutaneous electrical signals corre-
sponds to the work of Veraguth about the Psychogalvanic
reflex, published in 1909 as "Das Psychogalvanische Reflexphe-
nomen". At the same time, the publication of major works on
«galvanometer and emotions» (Peterson, 1907; Peterson and Jung,
1907) initiates a new era for the international career of elec-
trodermal signals as innovative tools for the exploration of
emotions and the unconscious.

The XXth century, through an important contribution of
animal and human experimental research, will be a long and
rich period in the comprehension of electrodermal signals.
The diversity of methods to record electrical skin variations
led to a confused way to name these variations. Thus, as
previously indicate, the term "Psychogalvanic reflex", ap-
peared with Peterson and Jung (1907) and renamed by
Veraguth (1909) as "galvanic skin reflex" (GSR), remained in
most databases until our days. Meanwhile, and waiting for an
international nomenclature, electrical skin variations had
been identified as: "skin potential reflex", "neuro-galvanic
response", "skin potential response", "skin resistance re-
sponse", "skin conductance response", "electrodermal re-
sponse" (Ruckmic, 1933). Finally, in 1981, the term "Elec-
trodermal Activity" (EDA) was adopted as an international
standard designation to identify spontaneous and induced
electrical skin activity, recorded thanks the use of several
techniques able to measure potential, resistance, or conduct-
ance electrical variations of the skin (Fowles et al., 1981).

5.2. Féré's methodological heritage: Skin Conduct-
ance technique

The Féré's contribution for EDA recordings originates
the current exosomatic techniques (skin conductance, SC;
skin resistance, SR; skin impedance, SI; skin admittance, SA).
These techniques allow to record electric variations of the

skin induced by an external voltage applied to the skin sur-
face, as it was later explained on the basis of the Ohm's law.
Indeed, this law shows that a constant voltage (0.5 V to 1 V)
applied to the skin allows to record variations in the intensity
of the external current which depend on the skin resistance.
The SC is the most used method for recording electrodermal
measures (Fig. 1A-B): the skin conductance level (SCL), a
tonic measure of spontaneous sympathetic traffic; the skin
conductance responses (SCRs), phasic measures of sympa-
thetic discharges following discrete stimulations. Considering
several physical principles and advantages and disadvantages
of the various recording techniques, the SC became the in-
ternational recognized method for recording EDA (Fowles
et al., 1981; Sequeira et al., 2009; Boucsein et al., 2012).

5.3. Tarchanoff's methodological heritage: Skin Po-
tential technique

The Tarchanov's contribution gave origin to the current
skin potential (SP) technique which allows to record poten-
tial differences between two skin sites, one active and the
other inactive (Fig. 1A-B); this is an endosomatic method
because, in contrast with exosomatic techniques, does not
require an external voltage applied to the skin. The SP allows
the acquisition of two measures: skin potential level (SPL)
and skin potential responses (SPRs). Successfully recorded in
animal exploration of central mechanisms of EDA (e.g. Se-
queira et al., 1995), SP recordings present several disad-
vantages linked to the acquisition requirements and skin sites
properties (electrolytes, skin temperature, etc.). Consequent-
ly, despite their technical simplicity, SP recordings are rarely
used in human studies, excepted when related with specific
methodological purposes.

<figure><img src="image_2.png" /><figcaption>**Figure 1.**
Electrodermal recordings as skin conductance and skin potential techniques, taking origin in Féré's and Tarchanoff's approaches respectively. **A:** Illustration of bipolar and unipolar skin sites, respectively for skin conductance (SC) and skin potential (SP) recordings; note also the typical electrodermal responses (uniphasic for SC and biphasic for SP). **B:** Broken and continuous arrows indicate standard skin placements of electrodes for SC and SP recordings, respectively. Iconographic adaptation from experimental apparatus of Kobayashi, Mandai and Sequeira at Ashikaga Institute of Technology (Japan, 2008).</figcaption></figure>
trical variations, Tarchanoff pursued known research activi-
ties in several topics (e.g. «...hallucinations ...in frogs ...»)
until 1900. In particular, since 1896, at St Petersburg, his new
scientific interest was focused on physiological effects of X-
ray, becoming a recognized specialist in this field.

Finally, although Tarchanoff initiated a significant tech-
nical background for the future of the electrodermal record-
ings, this contribution was just a step in his scientific career,
as the Féré's contribution was for his clinical practice. Both
pioneers died in 1907, ignoring thus the emerging interest of
their scientific contribution, applied to explore normal and
pathological mechanisms linked to the physiology and the
psychology.

5.1. Electrical variations of skin along the XXth cen-
tury

The period 1904-1909 brought new avenues for the
knowledge and applications of electrical variations of the
skin. This was due to the contribution of several authors:
Müller, Veraguth, Jung and Peterson. More precisely, the re-
birth of the interest for cutaneous electrical signals corre-
sponds to the work of Veraguth about the Psychogalvanic
reflex, published in 1909 as "Das Psychogalvanische Reflexphe-
nomen". At the same time, the publication of major works on
«galvanometer and emotions» (Peterson, 1907; Peterson and Jung,
1907) initiates a new era for the international career of elec-
trodermal signals as innovative tools for the exploration of
emotions and the unconscious.

The XXth century, through an important contribution of
animal and human experimental research, will be a long and
rich period in the comprehension of electrodermal signals.
The diversity of methods to record electrical skin variations
led to a confused way to name these variations. Thus, as
previously indicate, the term "Psychogalvanic reflex", ap-
peared with Peterson and Jung (1907) and renamed by
Veraguth (1909) as "galvanic skin reflex" (GSR), remained in
most databases until our days. Meanwhile, and waiting for an
international nomenclature, electrical skin variations had
been identified as: "skin potential reflex", "neuro-galvanic
response", "skin potential response", "skin resistance re-
sponse", "skin conductance response", "electrodermal re-
sponse" (Ruckmic, 1933). Finally, in 1981, the term "Elec-
trodermal Activity" (EDA) was adopted as an international
standard designation to identify spontaneous and induced
electrical skin activity, recorded thanks the use of several
techniques able to measure potential, resistance, or conduct-
ance electrical variations of the skin (Fowles et al., 1981).

5.2. Féré's methodological heritage: Skin Conduct-
ance technique

The Féré's contribution for EDA recordings originates
the current exosomatic techniques (skin conductance, SC;
skin resistance, SR; skin impedance, SI; skin admittance, SA).
These techniques allow to record electric variations of the

skin induced by an external voltage applied to the skin sur-
face, as it was later explained on the basis of the Ohm's law.
Indeed, this law shows that a constant voltage (0.5 V to 1 V)
applied to the skin allows to record variations in the intensity
of the external current which depend on the skin resistance.
The SC is the most used method for recording electrodermal
measures (Fig. 1A-B): the skin conductance level (SCL), a
tonic measure of spontaneous sympathetic traffic; the skin
conductance responses (SCRs), phasic measures of sympa-
thetic discharges following discrete stimulations. Considering
several physical principles and advantages and disadvantages
of the various recording techniques, the SC became the in-
ternational recognized method for recording EDA (Fowles
et al., 1981; Sequeira et al., 2009; Boucsein et al., 2012).

5.3. Tarchanoff's methodological heritage: Skin Po-
tential technique

The Tarchanov's contribution gave origin to the current
skin potential (SP) technique which allows to record poten-
tial differences between two skin sites, one active and the
other inactive (Fig. 1A-B); this is an endosomatic method
because, in contrast with exosomatic techniques, does not
require an external voltage applied to the skin. The SP allows
the acquisition of two measures: skin potential level (SPL)
and skin potential responses (SPRs). Successfully recorded in
animal exploration of central mechanisms of EDA (e.g. Se-
queira et al., 1995), SP recordings present several disad-
vantages linked to the acquisition requirements and skin sites
properties (electrolytes, skin temperature, etc.). Consequent-
ly, despite their technical simplicity, SP recordings are rarely
used in human studies, excepted when related with specific
methodological purposes.

<figure><img src="image_3.png" /><figcaption>**Figure 1.**
Electrodermal recordings as skin conductance and skin potential techniques, taking origin in Féré's and Tarchanoff's approaches respectively. **A:** Illustration of bipolar and unipolar skin sites, respectively for skin conductance (SC) and skin potential (SP) recordings; note also the typical electrodermal responses (uniphasic for SC and biphasic for SP). **B:** Broken and continuous arrows indicate standard skin placements of electrodes for SC and SP recordings, respectively. Iconographic adaptation from experimental apparatus of Kobayashi, Mandai and Sequeira at Ashikaga Institute of Technology (Japan, 2008).</figcaption></figure>
# 6. Electrodermal heritage: Looking to the future

Along the last century, EDA became a central physiological tool to explore most psychophysiological topics. Since 1980's, new approaches and disciplines reinforced its interest and enlarged its use in basic and clinical research.

Besides Féré's and Tarchanoff's contributions, the identification and applications of EDA are a typical result of interdisciplinary exchanges. In fact, in early days of EDA, three main influences can be considered: experimental rulers, initiated in German laboratories; clinical applications, emerging from French positions to deal with mental health and, finally, American psychologists looking for new methods of recording and analysis of electrodermal signals. These influences are also the expression of theoretical and technical information coming from physics, physiology, mental medicine, psychology and even spiritism (see Deren, 2011). More precisely, EDA became a privileged link between physiology and psychology interrogations, especially oriented to the comprehension of emotional behaviors (Boucsein, 2012). This corresponds to the need to explain emotional processes in normal individuals and the role of EDA as a potential indicator of emotional vulnerability in mental disorders (Miossec et al., 1986).

In more recent years, appeared new trends aiming to clarify the EDA's as a potential marker of cognitive and affective processes in different subfields of neuroscience. The first important point is related to the discovery of neural mechanisms subtending EDA central control. In this frame,

animal research developed at the University of Lille represents a strong and significant input revealing main neural structures implicated in the excitatory and inhibitory command of electrodermal responses (Bloch, 1965; Roy et al., 1993; Sequeira et al., 1995). Secondly, many studies tried to establish the capacity of EDA to reveal the impact of arousal and valence dimensions of emotional stimuli; several researches confirm the fact that EDA is a robust index of emotional arousal (Lang et al., 1993; Sequeira et al., 2009; D'Hondt et al., 2010; Delannoy et al., 2015; Kosonogov et al., 2017) whereas it fails to discriminate negative from positive valence. Finally, other works used the EDA as a promising marker of cognitive or emotional processes related to decision making (Damasio et al., 1990), anticipatory and circumdian behaviors (Amiez et al., 2003; Hot et al., 2005), subliminal stimulations (Silvert et al., 2004), reasoning (Carbonnel et al., 2006), cognitive loading (Salvia et al., 2012), psychosomatic interactions (D'Hondt et al., 2010), frontal lesions (Naveteur et al., 1993; Sanchez-Navarro et al., 2005), sleep processes and psychopathology (Delannoy et al., 2015; Martinez-Velazquez et al., 2017).

In conclusion, Féré and Tarchanoff, two discoverers with two different methodological and technical approaches, transmitted us a common scientific heritage, the EDA, still alive one hundred years later and promised to an expanding future in neuropsychology, psychopathology, neurology, chronobiology, criminology and in cognitive and affective neuroscience. Last but not least, Féré and Tarchanoff represented the early European ideal for the free transfer of knowledge between individuals, institutions and cultures.

## References

* Amiez, C., Procyk, E., Honoré, J., Sequeira, H., Joseph, J. P. (2003). Reward anticipation, cognition, and electrodermal activity in the conditioned monkey. *Experimental Brain Research, 149*, 267-75.

* Bloch, V. (1965). Le contrôle central de l'activité électrodermale. [Central control of electrodermal activity]. *Journal de Physiologie, 57*, suppl. 13, 1-132.

* Boucsein, W. (2012). *Electrodermal Activity*. Springer.

* Boucsein, W., Fowles, D. C., Grimnes, S., Ben-Shakhar, G., Roth, W. T., Dawson, M. E. and Filion, D. L. (2012). Publication recommendations for electrodermal measurements. *Psychophysiology, 49*, 1017-1034.

* Bradley, M. M., Lang, P. J. (2000). Measuring emotion: behavior, feeling, and physiology. In R. D. Lane, & L. Nadel (Eds.), *Cognitive Neuroscience of Emotion* (pp.242-276). Oxford University Press.

* Carbonnell, L., Vidal, F., Sequeira, H., Caverni, J. P. (2006). A reasoning basis revealed by electrodermal activity. *Psychophysiology, 43*, 387-93.

* Damasio, A. R., Tranel, D., Damasio, H. (1990). Individuals with socio-pathic behavior caused by frontal damage fail to respond autonomically to social stimuli. *Behavioral and Brain Research, 41*, 81-94.

* D'Arsonval, A. (1888). Remarques à propos de la production d'électricité chez l'homme. [Notes on the production of electricity in humans]. *Comptes-rendus des séances hebdomadaires de la Société de Biologie, 5*, 142-144.

* Delannoy, J., Mandai, O., Honore, J., Kobayashi, T., & Sequeira, H. (2015). Diurnal emotional states impact the sleep course. *PloS One, 10* (11), e0142721.

* Deren, P. (2011). *Aux sources d'un marqueur neurophysiologique des émotions: l'activité électrodermale*. [At the source of a neurophysiological marker of

emotions: electrodermale activity]. Thèse de Doctorat d'Histoire des Sciences et Epistémologie, Université de Lille 1, 298 p.

* D'Hondt, F., Lassonde, M., Collignon, O., Dubarry, A. S., Robert, M., Rigoulot, S., Honoré, J., Lepore, F., and Sequeira, H. (2010). Early brain-body impact of emotional arousal. *Frontiers in Human Neuroscience, 4*, 1-10.

* DuBois-Reymond, E. (1849). *Untersuchungen über thierische Elektrizität*. [Investigations into animal electricity]. Reimer.

* Féré, C. (1888). Note sur les modifications de la tension électrique dans le corps humain. [Note on changes in electrical voltage in the human body]. *Comptes-rendus des séances hebdomadaires de la Société de Biologie, 5*, 28-33.

* Féré, C. (1888). Note sur des modifications de la résistance sous l'influence des excitations sensorielles et des émotions. [Note on changes in resistance under the influence of sensory excitations and emotions]. *Comptes-rendus des séances hebdomadaires de la Société de Biologie, 5*, 217-219.

* Féré, C. (1892). *La pathologie des Emotions*. [Pathology of Emotions]. G. Baillière.

* Fowles, D. C., Christie, M. J., Edelberg, R., Grings, W. W., Lykken, D. T., Venables, P. H. (1981). Publication recommendations for electrodermal measurements. *Psychophysiology, 18*, 232-239.

* Hermann, L. (1882). Neue Untersuchungen über Hautströme. [New research on skin currents]. *Pfluger's Archiv, 27*, 280-288.

* Hermann, L., Luchsinger, B. (1878). Ueber die Secretionsströme der Haut der Katze. [About the secretion currents of the cat's skin]. *Pfluger's Archiv, 19*, 300-319.

* Hot, P., Leconte, P., & Sequeira, H. (2005). Diurnal autonomic variations and emotional reactivity. *Biological Psychology, 69*, 261-270.
## 6. Electrodermal heritage: Looking to the future

Along the last century, EDA became a central physiological tool to explore most psychophysiological topics. Since 1980's, new approaches and disciplines reinforced its interest and enlarged its use in basic and clinical research.

Besides Féré's and Tarchanoff's contributions, the identification and applications of EDA are a typical result of interdisciplinary exchanges. In fact, in early days of EDA, three main influences can be considered: experimental rulers, initiated in German laboratories; clinical applications, emerging from French positions to deal with mental health and, finally, American psychologists looking for new methods of recording and analysis of electrodermal signals. These influences are also the expression of theoretical and technical information coming from physics, physiology, mental medicine, psychology and even spiritism (see Deren, 2011). More precisely, EDA became a privileged link between physiology and psychology interrogations, especially oriented to the comprehension of emotional behaviors (Boucsein, 2012). This corresponds to the need to explain emotional processes in normal individuals and the role of EDA as a potential indicator of emotional vulnerability in mental disorders (Miossec et al., 1986).

In more recent years, appeared new trends aiming to clarify the EDA's as a potential marker of cognitive and affective processes in different subfields of neuroscience. The first important point is related to the discovery of neural mechanisms subtending EDA central control. In this frame,

animal research developed at the University of Lille represents a strong and significant input revealing main neural structures implicated in the excitatory and inhibitory command of electrodermal responses (Bloch, 1965; Roy et al., 1993; Sequeira et al., 1995). Secondly, many studies tried to establish the capacity of EDA to reveal the impact of arousal and valence dimensions of emotional stimuli; several researches confirm the fact that EDA is a robust index of emotional arousal (Lang et al., 1993; Sequeira et al., 2009; D'Hondt et al., 2010; Delannoy et al., 2015; Kosonogov et al., 2017) whereas it fails to discriminate negative from positive valence. Finally, other works used the EDA as a promising marker of cognitive or emotional processes related to decision making (Damasio et al., 1990), anticipatory and circumdian behaviors (Amiez et al., 2003; Hot et al., 2005), subliminal stimulations (Silvert et al., 2004), reasoning (Carbonnel et al., 2006), cognitive loading (Salvia et al., 2012), psychosomatic interactions (D'Hondt et al., 2010), frontal lesions (Naveteur et al., 1993; Sanchez-Navarro et al., 2005), sleep processes and psychopathology (Delannoy et al., 2015; Martinez-Velazquez et al., 2017).

In conclusion, Féré and Tarchanoff, two discoverers with two different methodological and technical approaches, transmitted us a common scientific heritage, the EDA, still alive one hundred years later and promised to an expanding future in neuropsychology, psychopathology, neurology, chronobiology, criminology and in cognitive and affective neuroscience. Last but not least, Féré and Tarchanoff represented the early European ideal for the free transfer of knowledge between individuals, institutions and cultures.

## References

* Amiez, C., Procyk, E., Honoré, J., Sequeira, H., Joseph, J. P. (2003). Reward anticipation, cognition, and electrodermal activity in the conditioned monkey. *Experimental Brain Research, 149*, 267-75.

* Bloch, V. (1965). Le contrôle central de l'activité électrodermale. [Central control of electrodermal activity]. *Journal de Physiologie, 57*, suppl. 13, 1-132.

* Boucsein, W. (2012). *Electrodermal Activity*. Springer.

* Boucsein, W., Fowles, D. C., Grimnes, S., Ben-Shakhar, G., Roth, W. T., Dawson, M. E. and Filion, D. L. (2012). Publication recommendations for electrodermal measurements. *Psychophysiology, 49*, 1017-1034.

* Bradley, M. M., Lang, P. J. (2000). Measuring emotion: behavior, feeling, and physiology. In R. D. Lane, & L. Nadel (Eds.), *Cognitive Neuroscience of Emotion* (pp.242-276). Oxford University Press.

* Carbonnell, L., Vidal, F., Sequeira, H., Caverni, J. P. (2006). A reasoning basis revealed by electrodermal activity. *Psychophysiology, 43*, 387-93.

* Damasio, A. R., Tranel, D., Damasio, H. (1990). Individuals with socio-pathic behavior caused by frontal damage fail to respond autonomically to social stimuli. *Behavioral and Brain Research, 41*, 81-94.

* D'Arsonval, A. (1888). Remarques à propos de la production d'électricité chez l'homme. [Notes on the production of electricity in humans]. *Comptes-rendus des séances hebdomadaires de la Société de Biologie, 5*, 142-144.

* Delannoy, J., Mandai, O., Honore, J., Kobayashi, T., & Sequeira, H. (2015). Diurnal emotional states impact the sleep course. *PloS One, 10* (11), e0142721.

* Deren, P. (2011). *Aux sources d'un marqueur neurophysiologique des émotions: l'activité électrodermale*. [At the source of a neurophysiological marker of

emotions: electrodermale activity]. Thèse de Doctorat d'Histoire des Sciences et Epistémologie, Université de Lille 1, 298 p.

* D'Hondt, F., Lassonde, M., Collignon, O., Dubarry, A. S., Robert, M., Rigoulot, S., Honoré, J., Lepore, F., and Sequeira, H. (2010). Early brain-body impact of emotional arousal. *Frontiers in Human Neuroscience, 4*, 1-10.

* DuBois-Reymond, E. (1849). *Untersuchungen über thierische Elektrizität*. [Investigations into animal electricity]. Reimer.

* Féré, C. (1888). Note sur les modifications de la tension électrique dans le corps humain. [Note on changes in electrical voltage in the human body]. *Comptes-rendus des séances hebdomadaires de la Société de Biologie, 5*, 28-33.

* Féré, C. (1888). Note sur des modifications de la résistance sous l'influence des excitations sensorielles et des émotions. [Note on changes in resistance under the influence of sensory excitations and emotions]. *Comptes-rendus des séances hebdomadaires de la Société de Biologie, 5*, 217-219.

* Féré, C. (1892). *La pathologie des Emotions*. [Pathology of Emotions]. G. Baillière.

* Fowles, D. C., Christie, M. J., Edelberg, R., Grings, W. W., Lykken, D. T., Venables, P. H. (1981). Publication recommendations for electrodermal measurements. *Psychophysiology, 18*, 232-239.

* Hermann, L. (1882). Neue Untersuchungen über Hautströme. [New research on skin currents]. *Pfluger's Archiv, 27*, 280-288.

* Hermann, L., Luchsinger, B. (1878). Ueber die Secretionsströme der Haut der Katze. [About the secretion currents of the cat's skin]. *Pfluger's Archiv, 19*, 300-319.

* Hot, P., Leconte, P., & Sequeira, H. (2005). Diurnal autonomic variations and emotional reactivity. *Biological Psychology, 69*, 261-270.
Kosonogov, V., De Zorzi, L., Honore, J., Martínez-Velázquez, E. S., Nan-drino, J. L., Martinez-Selva, J. M., & Sequeira, H. (2017). Facial thermal variations: A new marker of emotional arousal. *PloS One, 12* (9), e0183592.

Lang, P. J., Greenwald, M. K., Bradley, M. M., Hamm, A. O. (1993). Looking at pictures: Affective, facial, visceral and behavioural reactions. *Psychophysiology, 30*, 261-273.

Martínez-Velázquez, E. S., Honoré, J., De Zorzi, L., Ramos-Loyo, J., & Sequeira, H. (2017). Autonomic reactivity to arousing stimuli with social and non-social relevance in alexithymia. *Frontiers in Psychology, 11*, 23.

Miossec, Y., Catteau, M. C., Freixa Í Baqué, E., Sequeira-Martinho, H. (1986). Activité électrodermale bilatérale et asymétrie hémisphérique chez les malades psychiatriques. [Bilateral electrodermal activity and hemispherical asymmetry in psychiatric patients]. *Psychologie Médicale, 18*, 1227-1230.

Naveteur, J., Godefroy, O., & Sequeira, H. (1998). Electrodermal level asymmetry in a unilateral brain-damaged patient. *International Journal of Psychophysiology, 29*, 237-245.

Peterson, F. (1907). The galvanometer as a measurer of emotions. *British Medical Journal, 2*, 804-806.

Peterson, F. and Jung, C. G. (1907). Psychophysical investigations with the galvanometer and pneumograph in normal and insane individuals. *Brain, 30*, 153-218.

Roy, J. C., Sequeira, H., Delerm, B. (1993). Electrodermal activity: spinal and reticular mechanisms. In J. C. et al (Eds.), *Progress on Electrodermal Activity*. (pp. 73-92). Plenum Press.

Ruckmick, C. A. (1933). Terminology in psychogalvanic reflex. *Psychological Review, 40*, 97-98.

Salvia, E., Guillot, A., Collet, C. (2012). Autonomic nervous system correlates to readiness state and negative outcome during visual discrimination tasks. *International Journal of Psychophysiology, 84*, 211-218.

Sánchez-Navarro, J. P., Martínez-Selva, J. M., & Román, F. (2005). Emotional Response in Patients With Frontal Brain Damage: Effects of Affective Valence and Information Content. *Behavioral Neuroscience, 119*, 87-97.

Sequeira, H., Ba-M'Hamed, S., Roy, J. C. (1995). Fronto-parietal control of electrodermal activity in the cat. *Journal of the Autonomic Nervous System, 53*, 103-14.

Sequeira, H., Deren, P., Maitte, B. (2016). The Electrodermal Activity: Looking for French-Russian contributions. In J.C. Dupont, J.G. Barbara, E.I. Kolchinsky and M. Loskutova (Eds.), *Russian, French, German links in Embriology, Physiology and Medicine* (pp. 169-181). Hermann.

Sequeira, H., Hot, P., Silvert, L., Delplanque, S. (2009). Electrical autonomic correlates of emotion. *International Journal of Psychophysiology, 71*, 50-56.

Sequeira, H., Roy, J.C. (1997). Neural control of electrodermal activity. In M. Jordan (Ed.), *Central Nervous Control of Autonomic Function, vol. 11* (pp. 259-293). Harwood Academic Publishers.

Silvert, L., Delplanque, S., Bouwalerh, H., Verpoort, C., Sequeira, H. (2004). Autonomic responding to aversive words without conscious valence discrimination. *International Journal of Psychophysiology, 53*, 135-45.

Tarchanoff, J. (1889). Décharges électriques dans la peau de l'homme sous l'influence de l'excitation des organes des sens et de différentes formes d'activité psychique. [Electric shocks in the skin of man under the influence of the excitement of the sense organs and various forms of psychic activity]. *Comptes-rendus des séances hebdomadaires de la Société de Biologie, 41*, 447-451.

Tarchanoff, J. (1890). Sur les manifestations galvaniques de la peau de l'homme par stimulations des organes des sens et différentes formes d'activité psychique. [On the galvanic manifestations of human skin by stimulation of the sense organs and various forms of psychic activity]. *Pfluger's Archiv, 46*, 46-55.

Veraguth, O. (1909). *Das Psychogalvanischen Reflexphenomen*. [The psychogalvanic reflex phenomenon]. Karger.

Vigouroux, R. (1879). Sur le rôle de la résistance électrique des tissus dans l'électrodiagnostic. [On the role of the electrical resistance of tissues in electrodiagnosis]. *Comptes-rendus des séances hebdomadaires de la Société de Biologie, 31*, 336-339.

Vigouroux, R. (1888). L'électricité du corps humain. [Electricity of the human body]. *Comptes-rendus des séances hebdomadaires de la Société de Biologie, 5*, 138-142.
Kosonogov, V., De Zorzi, L., Honore, J., Martínez-Velázquez, E. S., Nan-drino, J. L., Martínez-Selva, J. M., & Sequeira, H. (2017). Facial thermal variations: A new marker of emotional arousal. *PloS One, 12* (9), e0183592.

Lang, P. J., Greenwald, M. K., Bradley, M. M., Hamm, A. O. (1993). Looking at pictures: Affective, facial, visceral and behavioural reactions. *Psychophysiology, 30*, 261-273.

Martínez-Velázquez, E. S., Honoré, J., De Zorzi, L., Ramos-Loyo, J., & Sequeira, H. (2017). Autonomic reactivity to arousing stimuli with social and non-social relevance in alexithymia. *Frontiers in Psychology, 11*, 23.

Miossec, Y., Catteau, M. C., Freixa Í Baqué, E., Sequeira-Martinho, H. (1986). Activité électrodermale bilatérale et asymétrie hémisphérique chez les malades psychiatriques. [Bilateral electrodermal activity and hemispherical asymmetry in psychiatric patients]. *Psychologie Médicale, 18*, 1227-1230.

Naveteur, J., Godefroy, O., & Sequeira, H. (1998). Electrodermal level asymmetry in a unilateral brain-damaged patient. *International Journal of Psychophysiology, 29*, 237-245.

Peterson, F. (1907). The galvanometer as a measurer of emotions. *British Medical Journal, 2*, 804-806.

Peterson, F. and Jung, C. G. (1907). Psychophysical investigations with the galvanometer and pneumograph in normal and insane individuals. *Brain, 30*, 153-218.

Roy, J. C., Sequeira, H., Delerm, B. (1993). Electrodermal activity: spinal and reticular mechanisms. In J. C. et al (Eds.), *Progress on Electrodermal Activity*. (pp. 73-92). Plenum Press.

Ruckmick, C. A. (1933). Terminology in psychogalvanic reflex. *Psychological Review, 40*, 97-98.

Salvia, E., Guillot, A., Collet, C. (2012). Autonomic nervous system correlates to readiness state and negative outcome during visual discrimination tasks. *International Journal of Psychophysiology, 84*, 211-218.

Sánchez-Navarro, J. P., Martínez-Selva, J. M., & Román, F. (2005). Emotional Response in Patients With Frontal Brain Damage: Effects of Affective Valence and Information Content. *Behavioral Neuroscience, 119*, 87-97.

Sequeira, H., Ba-M'Hamed, S., Roy, J. C. (1995). Fronto-parietal control of electrodermal activity in the cat. *Journal of the Autonomic Nervous System, 53*, 103-14.

Sequeira, H., Deren, P., Maitte, B. (2016). The Electrodermal Activity: Looking for French-Russian contributions. In J.C. Dupont, J.G. Barbara, E.I. Kolchinsky and M. Loskutova (Eds.), *Russian, French, German links in Embriology, Physiology and Medicine* (pp. 169-181). Hermann.

Sequeira, H., Hot, P., Silvert, L., Delplanque, S. (2009). Electrical autonomic correlates of emotion. *International Journal of Psychophysiology, 71*, 50-56.

Sequeira, H., Roy, J.C. (1997). Neural control of electrodermal activity. In M. Jordan (Ed.), *Central Nervous Control of Autonomic Function, vol. 11* (pp. 259-293). Harwood Academic Publishers.

Silvert, L., Delplanque, S., Bouwalerh, H., Verpoort, C., Sequeira, H. (2004). Autonomic responding to aversive words without conscious valence discrimination. *International Journal of Psychophysiology, 53*, 135-45.

Tarchanoff, J. (1889). Décharges électriques dans la peau de l'homme sous l'influence de l'excitation des organes des sens et de différentes formes d'activité psychique. [Electric shocks in the skin of man under the influence of the excitement of the sense organs and various forms of psychic activity]. *Comptes-rendus des séances hebdomadaires de la Société de Biologie, 41*, 447-451.

Tarchanoff, J. (1890). Sur les manifestations galvaniques de la peau de l'homme par stimulations des organes des sens et différentes formes d'activité psychique. [On the galvanic manifestations of human skin by stimulation of the sense organs and various forms of psychic activity]. *Pfluger's Archiv, 46*, 46-55.

Veraguth, O. (1909). *Das Psychogalvanischen Reflexphenomen*. [The psychogalvanic reflex phenomenon]. Karger.

Vigouroux, R. (1879). Sur le rôle de la résistance électrique des tissus dans l'électrodiagnostic. [On the role of the electrical resistance of tissues in electrodiagnosis]. *Comptes-rendus des séances hebdomadaires de la Société de Biologie, 31*, 336-339.

Vigouroux, R. (1888). L'électricité du corps humain. [Electricity of the human body]. *Comptes-rendus des séances hebdomadaires de la Société de Biologie, 5*, 138-142.