Investigating the Autonomic Nervous System Response to Anxiety in Children with Autism Spectrum Disorders

Assessment of anxiety symptoms in autism spectrum disorders (ASD) is a challenging task due to the symptom overlap between the two conditions as well as the difficulties in communication and awareness of emotions in ASD. This motivates the development of a physiological marker of anxiety in ASD that is independent of language and does not require observation of overt behaviour. In this study, we investigated the feasibility of using indicators of autonomic nervous system (ANS) activity for this purpose. Specially, the objectives of the study were to 1) examine whether or not anxiety causes significant measurable changes in indicators of ANS in an ASD population, and 2) characterize the pattern of these changes in ASD. We measured three physiological indicators of the autonomic nervous system response (heart rate, electrodermal activity, and skin temperature) during a baseline (movie watching) and anxiety condition (Stroop task) in a sample of typically developing children (n = 17) and children with ASD (n = 12). The anxiety condition caused significant changes in heart rate and electrodermal activity in both groups, however, a differential pattern of response was found between the two groups. In particular, the ASD group showed elevated heart rate during both baseline and anxiety conditions. Elevated and blunted phasic electrodermal activity were found in the ASD group during baseline and anxiety conditions, respectively. Finally, the ASD group did not show the typical decrease in skin temperature in response to anxiety. These results suggest that 1) signals of the autonomic nervous system may be used as indicators of anxiety in children with ASD, and 2) ASD may be associated with an atypical autonomic response to anxiety that is most consistent with sympathetic over-arousal and parasympathetic under-arousal.     

Functional topography of the dorsomedial hypothalamus

The dorsomedial hypothalamus (DMH) has been proposed to play key roles in both the defense reaction to acute stress and in the thermoregulatory response to cold. We reasoned that the autonomic/respiratory motor patterns of these responses would be mediated by at least partly distinct DMH neuron populations. To test this, we made simultaneous recordings of phrenic nerve and plantar cutaneous vasoconstrictor (CVC) activity in 14 vagotomized, ventilated, urethane-anesthetized rats. Microinjections of d,l-homocysteic acid (DLH; 15 nl, 50 mM) were used to cause localized, short-lasting (<1 min) activation of DMH neuron clusters. Cooling the rat's trunk skin by perfusing cold water through a water jacket-activated plantar CVC activity but depressed phrenic burst rate (cold-response pattern). The expected "stress/defense response" pattern would be phrenic activation, with increased blood pressure, heart rate, and possibly CVC activity. DLH microinjections into 76 sites within the DMH region never reduced phrenic activity. They frequently increased phrenic rate and/or plantar CVC activity, but the magnitudes of those two responses were not significantly correlated. Plantar CVC responses were evoked most strongly from the dorsal hypothalamic area and most dorsal part of the dorsomedial nucleus, whereas peak phrenic rate responses were evoked from more caudal sites; their relative magnitudes varied systematically with rostrocaudal position. Tachycardia correlated with plantar CVC responses but not phrenic rate. These findings indicate that localized activation of DMH neurons does not evoke full "cold-response" or stress/defense response patterns, but they demonstrate the existence of significant functional topography within the DMH region.     

Odor Hedonics: Connection With Emotional Response Estimated by Autonomic Parameters

The aim of this paper is to analyse the relationship betweenself-report hedonic evaluations and the physiological expressionof emotion in response to odorants. We try to solve the followingquestions: (1) Is it possible to find any experimental evidencethat the sense of smell is linked with emotion? (2) What kindof odorants can be distinguished by autonomic analysis? (3)Is there a link between hedonics and autonomic information?The effects of odorants on the emotional process were estimated,in terms of autonomic nervous system (ANS) activity. Fifteensubjects inhaled five odorants as olfactory stimuli: lavender(LAV), ethyl acetoacetate (EAA), camphor (CAM), acetic acid(AA) and butyric acid (BA). After inhaling the odorant, subjectswere requested to fill out an 11-point hedonic scale to rateits pleasantness versus unpleasantness. ANS parameters wereas follows: two electrodermal responses, skin potential (SP)and resistance (SR); two thermovascular parameters, skin bloodflow (SBF) and skin temperature (ST); and two cardiorespiratoryparameters: instantaneous respiratory frequency (IRF) and instantaneousheart rate (IHR). Simultaneous recording of six parameters showedthat specific autonomic patterns were associated with each odorant.An analysis of variance made it possible to differentiate amongthe five odorants. Two-by-two odorant comparisons for autonomicresponses using Tukey's HSD multiple comparison test only permitteddifferentiation between pleasant odorants (LAV and EAA) andunpleasant (AA and BA) ones, but camphor was differentiatedfrom both pleasant and unpleasant odorants. Each odorant elicitedresponses in the different parameters, yet subjects respondedthrough their preferential channels; an average of two channelswas used by each subject. These results when compared with thoseobtained with other senses (visual and auditory). did not evidencethe postulated preferential link between olfaction and emotion.A'strong link between hedonics and ANS response could be demonstratedwhen considering each subject and mainly through his/her preferentialchannel(s); conversely a weak correlation (SR duration excepted)was obtained between inter-subjects' hedonic evaluation. Itseems that for a given population the autonomic response reflectthe odor valence only through some parameters related to themain preferential channel(s) and thus the global autonomic patternhas to be considered. Chem. Senses 22: 237–248, 1997.     

Evoked autonomic skin potentials (Present views of the mechanisms)

This article presents the present views on the mechanisms of the evoked autonomic skin potentials (EASP). Consideration is given to the research history of the electrodermal phenomena, methodological features of EASP recording, and possibilities of their implementation in clinical neurology. The EASP is a suprasegmental somatoautonomic reflex, whose effector is presented by sweat glands, and the posterior hypothalamus acts as a response “generator.” Besides the afferent and efferent parts, the reflex arc includes the hierarchical CNS structures that modulate the response expression. The EASP recorded from healthy humans in supine position in the state of rest under the usual ambient temperature is presented by a triphase curve. The first phase is manifested by a slight positive deflection from the baseline. It is associated with the initial decrease in perspiration in response to stimulation. The amplitude of this deflection reflects the activity of the hypothalamic centers that inhibit perspiration and is a measure of parasympathetic activity. The following second phase consists of the ascending and descending parts. The ascending part reflects the increase in perspiration in response to stimulation and is represented by a pronounced negative deflection of the potential. The descending part of the second phase is associated with the recovery of the normal (tonic) perspiration level. The amplitude of the second phase reflects the activity of the suprasegmental (primarily, hypothalamic) sympathetic centers. The third phase represents the trace wave, the mechanisms of which are still vague. The EASP latencies reflect a synaptic delay in the structures of the CNS and ganglia of the sympathetic trunk as well as the time of impulse conduction by the postganglionic sympathetic fibers. The EASP changes under conditions of exposure to high temperature and humidity and under the influence of some drugs (Reserpine [Rauwolfia alcaloid], Pyrroxanum, Sydnocarb [syn. Mesocarbum], Aethimizolum, Gammalon [syn. Aminalonum, GABA], and Phenazepamum) are considered.     

Changes in amplitude and temporal characteristics of evoked potentials in the sensomotor cortex after division of the spinocervical tracts in cats

Temporal and amplitude characteristics of evoked potentials of the sensomotor cortex in waking cats were studied during variation in the intensity of electrodermal stimulation. The results obtained in experiments on intact animals and on the same animals for several months after division of the spinocervical tracts at the cervical level were compared. After blocking of the inflow of afferent impulses along these tracts of the spinal cord, statistically significant changes in evoked potentials were observed, mainly in response to medium and strong stimulation. These changes were more clear in the motor and second somatosensory areas of the cortex. A decrease in sensitivity to pain also was found. During recovery of the motor functions, cutaneous sensation remained impaired and the amplitude characteristics of the evoked somatosensory activity were not restored. The results suggest that thinner fibers predominate among the primary afferent fibers of the spinocervical tract, and their projections are more widely represented in the second somatosensory and motor areas of the cortex.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 4, No. 5, pp. 516–523, September–October, 1972.     

Interaction between responses evoked by acoustic and somatosensory stimuli in neurons of the magnocellular part of the medial geniculate body

Interaction between responses to acoustic clicks and to electrodermal stimulation of the contralateral forelimb was investigated in 78 neurons in the magnocellular part of the medial geniculate body of curarized cats. Of this number, 33 neurons responded by discharges both to clicks and to electrodermal stimulation, 25 responded to clicks only, and 20 to electrodermal stimulation only, or to stimulation of the dorsal funiculus of the spinal cord. Conditioning stimulation evoked inhibition of the response to the testing stimulus in 32 of 33 neurons responding by spike discharges to both clicks and electrodermal stimulation. Electrodermal stimulation inhibited responses to clicks in all the neurons tested which responded only to clicks, whereas clicks evoked inhibition of responses to electrodermal stimulation (or to stimulation of the dorsal funiculus) in only four of the 20 neurons which responded to these types of stimulation only. It is suggested that inhibition of excitability arising in neurons of the magnocellular part of the medial geniculate body during interaction between auditory and somatosensory afferent volleys is based on postsynaptic inhibition.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 4, pp. 368–374, July–August, 1980.     

Contribution of infralimbic cortex in the cardiovascular response to acute stress

The infralimbic region of the medial prefrontal cortex (IL) modulates autonomic and neuroendocrine function via projections to subcortical structures involved in the response to stress. We evaluated the contribution of the IL to the cardiovascular response evoked by acute stress. Under anesthesia (80 mg/kg ketamine-11.5 mg/kg xylazine), rats were implanted with telemetry probes or arterial lines for recording heart rate and blood pressure. Guide cannulas were implanted to target the IL for microinjection of muscimol (100 pmol/100 nl), N-methyl-d-aspartate (NMDA) (6 pmol/100 nl), or vehicle (100 nl). Microinjection of muscimol, an agonist of GABA(A) receptors, into the IL had no effect on stress-evoked cardiovascular and thermogenic changes in any of the paradigms evaluated (cage switch, restraint plus air-jet noise, or air-jet stress). However, microinjection of the excitatory amino acid NMDA into the IL attenuated the pressor and tachycardic response to air-jet stress. Pretreatment with the selective NMDA antagonist dl-2-amino-5-phosphonopentanoic acid (AP-5, 100 pmol/100 nl) blocked the effect of NMDA on the cardiovascular response to air-jet stress. We conclude that 1) the IL region is not tonically involved in cardiovascular or thermogenic control during stress or under baseline conditions, and 2) activation of NMDA receptors in the IL can suppress the cardiovascular response to acute stress exposure.     

Thermal biofeedback and lower extremity blood flow in adults with diabetes: is neuropathy a limiting factor?

Thermal biofeedback may be a useful adjunctive technique for enhancing cutaneous blood flow in patients with lower-extremity vascular complications of diabetes. However, autonomic, sensory, and/or motor neuropathies may impair vasomotion and limit the ability to alter blood flow and achieve significant foot warming with thermal biofeedback. We examined nerve function associated with four common types of diabetic neuropathy (sympathetic–autonomic, vagal–autonomic, sensory, and motor), hypothesizing that both sympathetic–autonomic and sensory neuropathies would limit the acquisition of biofeedback-mediated foot warming. Twenty-four participants with diabetes mellitus (19 with type II and 5 with type I) received a nerve conduction study and neurological evaluation of the upper and lower extremities. Hand temperature, foot temperature, and electrodermal gradient at the toes were monitored across six thermal biofeedback sessions. Participants were able to significantly raise p < .01) foot temperatures across sessions, an average of 2.2°F. Consistent with our hypotheses, 41% of the variance in foot warming was explained by lower-extremity sympathetic–autonomic and sensory nerve function tests. This study demonstrated that a general diabetic population, including patients with mild-to-moderate neuropathy, can increase skin perfusion with thermal biofeedback. As hypothesized, lower-extremity sympathetic–autonomic and sensory neuropathies interfered with foot warming.     

Multisensory convergence on neurons of the motor cortex in unanesthetized cats

Postsynaptic potentials (PSPs) of 83 neurons in the motor cortex of unanesthetized cats in response to electrodermal, photic, and acoustic stimulation were investigated by intra-and quasi-intracellular recording methods. Most cells responded to stimulation of at least one limb. About 60% of neurons of the posterior and over 75% of neurons of the anterior sigmoid gyrus responded to stimulation of two (or more) limbs. In 29 of 39 neurons of the anterior and 12 of 44 of the posterior sigmoid gyrus PSPs with a short (less than 50 msec) and stable latent period were evoked by flashes and clicks. On presentation of two somesthetic stimuli complete blocking (if the interval was less than 30–60 msec) or weakening (interval 30–200 msec) of responses to the second (testing) stimulus was observed. On presentation of paired photic (or acoustic) stimuli or paired stimuli of different modalities at various intervals from 0 to 100 msec, the testing response was often potentiated. The character of the responses and their interaction thus differed from those obtained under chloralose anesthesia [6, 7]. It is postulated that under the action of chloralose a system of neurons with strong excitatory feedback is formed in the motor cortex which may respond to stimuli of different modalities by something resembling the "all or nothing" principle.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 3, No. 6, pp. 563–573, November–December, 1971.     

Comparison of skin sympathetic nerve responses to isometric arm and leg exercise.

Measurement of skin sympathetic nerve activity (SSNA) during isometric exercise has been previously limited to handgrip. We hypothesized that isometric leg exercise due to the greater muscle mass of the leg would elicit greater SSNA responses than arm exercise because of presumably greater central command and muscle mechanoreceptor activation. To compare the effect of isometric arm and leg exercise on SSNA and cutaneous end-organ responses, 10 subjects performed 2 min of isometric knee extension (IKE) and handgrip (IHG) at 30% of maximal voluntary contraction followed by 2 min of postexercise muscle ischemia (PEMI) in a normothermic environment. SSNA was recorded from the peroneal nerve. Cutaneous vascular conductance (laser-Doppler flux/mean arterial pressure) and electrodermal activity were measured within the field of cutaneous afferent discharge. Heart rate and mean arterial pressure significantly increased by 16 +/- 3 and 23 +/- 3 beats/min and by 22 +/- 2 and 27 +/- 3 mmHg from baseline during IHG and IKE, respectively. Heart rate and mean arterial pressure responses were significantly greater during IKE compared with IHG. SSNA increased significantly and comparably during IHG and IKE (52 +/- 20 and 50 +/- 13%, respectively). During PEMI, SSNA and heart rate returned to baseline, whereas mean arterial pressure remained significantly elevated (Delta12 +/- 2 and Delta13 +/- 2 mmHg from baseline for IHG and IKE, respectively). Neither cutaneous vascular conductance nor electrodermal activity was significantly altered by either exercise or PEMI. These results indicate that, despite cardiovascular differences in response to IHG and IKE, SSNA responses are similar at the same exercise intensity. Therefore, the findings suggest that relative effort and not muscle mass is the main determinant of exercise-induced SSNA responses in humans.     

Interweaving and overlapping of evoked potentials

The refractory effect of one stimulus upon the response to a closely following stimulus in a different modality is much less than upon the response to a stimulus in the same modality. It is therefore far more efficient to record responses to stimuli in different modalities concurrently than to record each one separately. We evaluated 2 techniques for concurrent recording. Interweaving involves recording the response to one stimulus in the intervals between recording responses to other stimuli. Overlapping occurs when two or more responses are at times being simulateneously recorded. Interweaving and overlapping reduced the time required to record auditory brain-stem responses, short-latency somatosensory evoked potentials and pattern-reversal visual evoked potentials by a factor of 3 over the time required to record each response separately. Overlapping caused no significant change in the evoked potentials. Depending upon the actual timing schedule, interweaving may distort the evoked potentials if later parts of the response to one stimulus override the evoked potential to a following stimulus. Filtering and randomization of stimulus timing may attenuate the effects of these overriding potentials.     

用独立分量分析和小波变换方法研究实验过程中脑诱发电位信号强度的变化

诱发电位的提取通常依靠相干平均方法,需要进行多次的重复刺激,实验时间较长。随着实验时间的增加,受试者生理因素及环境因素的变化,会影响诱发电位的正常形态(波形、强度和相位)。利用独立分量分析和小波变换方法,通过时域信息和空域信息的综合应用,可成功提取到听觉诱发电位晚成分的强度在实验过程中的变化,对由于实验时间增加对晚成分的影响做出定量评价。结果表明,在10min左右的实验过程中,听觉诱发电位晚成分的幅度会下降约40％。     

May the Best Joint-Actions Win: Physiological Linkage During Competition

Previous work showed that, when we interact with other people, an alignment of psychophysiological measures occur as a clue about the intensity of the social interaction. Available evidence highlighted increase autonomic synchrony, known as physiological linkage, during intense dyadic situations, like conflictual conversations within romantic couples, friends, or therapeutic settings. Starting from the idea that higher physiological linkage could support better performance and be correlated with approach attitudes (Behavioral Activation System, BAS), in the present study a conflictual situation was proposed by making subjects compete during an attentional task and stressing the importance to win as a measure of future professional success. Autonomic activity (electrodermal: skin conductance level and response: SCL, SCR; and cardiovascular indices: heart rate: HR) was recorded during the task, where subjects received trial-related feedbacks on their performance, and an average score halfway which (fictitiously) assessed their position in terms of accuracy and reaction times with respect to the opponent. In parallel, behavioral inhibition and activation have been assessed by means of the Behavioral Inhibition/Activation System Questionnaire (BIS/BAS). 32 subjects coupled in 16 dyads were recruited. Intra-subject analyses revealed that, after the general evaluation assessing a winning condition, the behavioral performance improved and the electrodermal response increased. Also, correlational analyses showed a relation between BAS, and specifically BAS reward, with SCR. Inter-subject analyses showed higher synchrony in SCR and HR after the feedback. Such results confirm the increased synchronic effect after a highly conflictual condition, and the presence of a relation between subjective performance, approach-related motivations, and physiological linkage.     

Assessment of sympathoneural activity in clinical research

The assessment of autonomic nervous activity is a frequent and challenging goal of clinical research. The diverse current approaches are reviewed. Direct recording from the sympathetic input to muscle has the advantage of excellent time resolution and directness, but gives no information on the sympathetic input to the internal organs. Plasma noradrenaline concentration has limitations of specificity, some of which are overcome by single isotope radiotracer kinetic techniques. Other chemical markers are less satisfactory. End organ responses are generally limited to cardiovascular and cutaneous autonomic assessment, but sophisticated information is obtainable using power spectral analysis of heart rate variability. Assessment of receptor systems, of first and second messengers and radionuclide imaging of adrenergic nerves all give complimentary information. It is likely that a combination of these diverse techniques will advance understanding of the role of the autonomic nervous system in many disease states.     

Visual acuity of the midland banded water snake estimated from evoked telencephalic potentials

The visual acuity of seven midland banded water snakes was measured by recording evoked responses from telencephalon to temporally modulated square wave grating patterns. Using conventional electrophysiological techniques and signal averaging, high contrast square wave gratings of different spatial frequencies were presented. Acuity was estimated by extrapolating relative response amplitude/log₁₀ spatial frequency functions which yielded an average acuity of 4.25 cycles/degree. Refractive state was also estimated by recording evoked potentials to intermediate spatial frequencies with different lenses in front of the eye. Polynomial fits indicated that under the experimental conditions the snakes were around 6.4 diopters hyperopic suggesting a corrected acuity of 4.89 cycles/degree. Reduction of grating luminance resulted in a reduction in evoked potential acuity measurements. These results indicate that the spatial resolution of midland banded water snakes is the equal of cat; about 20/120 in human clinical terms.     

Anticipatory Electrodermal Response as a Differentiating Somatic Marker Between Children with ADHD and Controls

Six children with Attention Deficit Hyperactivity Disorder (ADHD) and five control children between the ages of 9 and 11 years were administered an adapted version of the Iowa Gambling Task while measuring anticipatory electrodermal response (EDR). Anticipatory EDR measures were compared between groups. Results indicate that the ADHD group exhibited significantly lower autonomic reactivity to anticipated consequences, evidencing a neuropsychological profile similar to patients with lesions in the ventromedial prefrontal cortex.     

Responses of units in the magnocellular part of the medial geniculate body to acoustic and somatosensory stimulation

Responses of 150 neurons in the magnocellular part of the medial geniculate body to clicks and to electrodermal stimulation of the contralateral forelimb were investigated in cats immobilized with myorelaxin. Of the total number of neurons 65% were bimodal, 16.6% responded only to clicks, and 15.4% only to electrodermal stimulation. The unitary responses were excitatory (spike potentials) and inhibitory (inhibition of spontaneous activity). Responses beginning with excitation occurred more frequently to stimulation by clicks than to electrodermal stimulation, whereas initial inhibition occurred more often to electrodermal stimulation. The latent period of the initial spike potentials in response to clicks and to electrodermal stimulation was 5–27 and 6–33 (mean 11.6 and 16.2) msec respectively. Positive correlation was found between the latent periods of spike potentials recorded in the same neurons in response to clicks and to electrodermal stimulation, and also to electrodermal stimulation and to stimulation of the dorsal funiculus of the spinal cord. It is concluded that the magnocellular division of the medial genicculate body is a transitional structure between the posterior ventral nucleus and the parvocellular division of the medial geniculate body, and that in addition, it is connected more closely with the auditory than with the somatosensory system. It is suggested that the somatosensory input into the magnocellular division of the medial geniculate body is formed mainly by fibers of the medial lemniscus.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 10, No. 2, pp. 133–141, March–April, 1978.     

Discrimination of the dynamic properties of sound source spatial location in humans: Electrophysiology and psychophysics

The spatial resolution of the human auditory system was studied under conditions, where the location of the sound source was changed according to different temporal patterns of interaural time delay. Two experimental procedures were run in the same group of subjects: a psychophysical procedure (the transformed staircase method) and an electrophysiological one (which requires recording of mismatch negativity, the auditory evoked response component). It was established that (1) the value of the mismatch negativity reflected the degree of spatial deviation of the sound source; (2) the mismatch negativity was elicited even at minimum (20μs) interaural time delays under both temporal patterns (abrupt azimuth change and gradual sound movement at different velocities); (3) an abrupt change of the sound source azimuth resulted in a greater mismatch negativity than gradual sound movement did if the interaural time delay exceeded 40 μs; (4) the discrimination threshold values of the interaural delay obtained in the psychophysical procedure were greater than the minimum interaural delays that elicited mismatch negativity, with the exception of the expert listeners, who exhibited no significant difference.     

Heart Rate Variability and Skin Conductance During Repetitive TMS Course in Children with Autism

Autism spectrum disorder (ASD) is a developmental disorder marked by difficulty in social interactions and communication. ASD also often present symptoms of autonomic nervous system (ANS) functioning abnormalities. In individuals with autism the sympathetic branch of the ANS presents an over-activation on a background of the parasympathetic activity deficits, creating an autonomic imbalance, evidenced by a faster heart rate with little variation and increased tonic electrodermal activity. The objective of this study was to explore the effect of 12 sessions of 0.5 Hz repetitive transcranial magnetic stimulation (rTMS) over dorsolateral prefrontal cortex (DLPFC) on autonomic activity in children with ASD. Electrocardiogram and skin conductance level (SCL) were recorded and analyzed during each session of rTMS. The measures of interest were time domain (i.e., R–R intervals, standard deviation of cardiac intervals, NN50-cardio-intervals >50 ms different from preceding interval) and frequency domain heart rate variability (HRV) indices [i.e., power of high frequency (HF) and low frequency (LF) components of HRV spectrum, LF/HF ratio]. Based on our prior pilot studies it was proposed that the course of 12 weekly inhibitory low-frequency rTMS bilaterally applied to the DLPFC will improve autonomic balance probably through improved frontal inhibition of the ANS activity, and will be manifested in an increased length of cardiointervals and their variability, and in higher frequency-domain HRV in a form of increased HF power, decreased LF power, resulting in decreased LF/HF ratio, and in decreased SCL. Our post-12 TMS results showed significant increases in cardiac intervals variability measures and decrease of tonic SCL indicative of increased cardiac vagal control and reduced sympathetic arousal. Behavioral evaluations showed decreased irritability, hyperactivity, stereotype behavior and compulsive behavior ratings that correlated with several autonomic variables.     

The characteristics of the electrodermal activity during changes in the level of human wakefulness

The wake-drowsiness transition during the performance of a monotonous psychomotor test was studied using polygraphic recording, with particular emphasis on changes in the electrodermal activity (EDA) and occurrence of electrodermal reactions (EDR). It was found that decrease in wakefulness was accompanied by a drop of the EDA. The EDR gradually disappeared for several minutes and did not reappear without activation; their dependence on sex and individual features of a subject significantly increased. It is suggested that discrepancies in the experimental results of psychophysiological studies with EDA may be explained by an insufficient control of the subject's alertness throughout the experiment. Examples of such discrepancies are given: disagreement of sex differences in the EDA, differentiation between EDA-labile and EDA-stable persons, on a possibility of recording the "emotional" EDA from different parts of human body etc. The ways of reproducibility of the results are discussed including the recording of several wake-drowsiness transitions and better recognition of the EDR.