Variation in sweating patterns: implications for studies of hot flashes through skin conductance

OBJECTIVE: The literature of sweat physiology and population variation in response to heat stress suggests that variation in sweating patterns may affect the measurement of hot flashes. This study examined variation in sweating patterns in Puebla, Mexico, and Amherst, MA, and compared the levels of concordance between subjective and objective measures of hot flashes. DESIGN: Thirteen women in Puebla, Mexico, and 15 women in Amherst, MA, aged 45 to 61, completed surveys, body diagrams of heat flow during a hot flash, anthropometric measures, and the measurement of hot flashes through skin conductance monitoring. Hot flashes were measured through sternal (Mexico and Massachusetts) and nuchal (Mexico only) skin conductance. RESULTS: Mexican women were significantly more likely to describe the heat of hot flashes on the back of their neck (100% vs 40%) and on their arms and/or hands (85% vs 40%) compared with women in Massachusetts. Hot flashes in the midback were associated with concordance between nuchal, but not sternal, measures of skin conductance and subjective report in Mexico. In comparing average scores for concordance between subjective and sternal measures of hot flashes, there was a higher mean score for true positives in Mexico (61% vs 29%, P=0.06) and a significantly higher mean score for false-negative measures in Massachusetts (57% vs 21%, P=0.04). CONCLUSIONS: Variation in rates of concordance between subjective and objective measures were not adequately explained by sweating patterns. Future studies should consider population variation in acclimatization and assess variation in the amount of sweat produced during a hot flash.     

Interstimulus intervals for skin conductance response measurement

This study examined, using the Concealed Information paradigm, whether interstimulus intervals (ISI) typically used for electrodermal measurement can be shortened. An ISI ranging from 16 s to 24 s (with a mean of 20 s) was compared with an ISI shortened by 50% using a within‐participants design. It was demonstrated that this shortening had no effect on the differential skin conductance responses to the personally significant details and nearly identical detection efficiency was observed under the 2 ISIs. However, overall responses were attenuated with the shorter ISI. The implications of these results for various types of studies, using skin conductance responses, were discussed.     

Contribution of skin thermal sensitivities of large body areas to sweating response

The thermal sensitivity of different parts of the body was investigated by heating large areas of the body surface while the mean skin temperature calculated from Hardy and DuBois ' formula (1938) was always kept constant. The right arm sweating responses recorded under a local thermal clamp were related to changes in segmental skin temperatures of the different parts of the body. The results show that: 1) the various local peripheral signals are projected into integrating structures in the central nervous system; 2) the thermal sensitivity is greater for the head-and-trunk area in comparison with other parts of the body. For resting nude subjects, the formula of Hardy and DuBois remains a pertinent way for evaluating the role of skin thermal signals in the central drive for sweating. The peripheral contribution to the central sweating drive depends only on the skin temperature change and on the size of the stimulated area.     

Emotional modulation of skin conductance and eyeblink responses to a startle probe

In this study, I examined emotional modulation of the eyeblink, skin conductance, and cardiac responses to an acoustic startle (103 dB[A] white noise) probe. Twenty-five female and 17 male undergraduates imagined pleasant, neutral, and fearful situations in a tone-cued imagery procedure. Both the eyeblink and skin conductance responses to startle probes were potentiated (larger magnitude, shorter latency) during fear as compared with neutral and pleasant imagery. The amount of emotional modulation in these two response systems was significantly correlated both between and within subjects. The startle probe interrupted ongoing cardiac deceleration during the imagery task, but this interruption was not related to the emotional content of imagery.     

Accurate measurement of skin blood flow by a thermal conductance method

The thermal conduction method of measuring skin blood flow has been shown to be accurate, sensitive, virtually atraumatic and only affected by the cutaneous blood flow. The general fluctuations in skin blood flow are monitored by one probe on an untreated site. The reading from a second probe on the test site is expressed as a ratio of the first probe reading. This combination is shown to accurately reflect changes in blood flow of the treated site. A calibration procedure is described.     

Role of basolateral membrane conductance in the regulation of transepithelial sodium transport across frog skin

Circuit analyses of the principal cell compartment of frog skin ( Rana temporaria and R. esculenta) were made using microelectrode measurements under short-circuit conditions and with the aid of the Na(+) channel blocker amiloride. Under control conditions, intracellular potential ranged between -65 and -5 mV, and the conductances of the apical and basolateral membranes were related directly to the short-circuit current and inversely to the cellular potential. Blockade of apical Na(+) uptake by amiloride hyperpolarized the cells to nearly the same value, irrespective of the potential under transporting conditions. Under these conditions, basolateral membrane conductance increased greatly, which led to paradoxical reactions of the transepithelial Na(+) transport at lower concentrations of amiloride. The half-maximal inhibitory concentration of amiloride estimated from the response of the apical membrane conductance (99+/-10 nM) was about 5 times lower than the value derived from transepithelial current or conductance in the same tissues. The results are discussed in the context of the importance of the membrane potential for acute control of membrane conductance and transepithelial transport.     

Lapses in skin conductance responding across anatomical sites: Comparison of fingers,feet, forehead,and wrist

The fingers are widely accepted as the gold standard for skin conductance (SC) recording, with the feet as a strong alternative. However, there are gaps in the current literature comparing these sites. There is also a great deal of interest in alternative recording sites to permit mobility, but data evaluating these are few and inconsistent. The present report compared multiple sites (fingers, abductor hallucis of the foot, arch of the foot, toes, forehead, and wrist) from 45 college student participants in a short‐term sedentary laboratory setting and found large variation in both tonic and phasic SC responses, as well as crucial lapses in responding at nonpalmar sites. Across‐site correlations between participants and within participants were also examined. The present data show that, in the laboratory setting employing commonly used recording techniques and stimuli, the nonpalmar sites are generally less responsive than the fingers, and the wrist in particular is the lowest in responding, whereas the toes are most similar to the fingers in responding. Within‐participant correlations between the fingers and other sites were greatest for the plantar sites and least for the forehead.     

On periodic sweating from the human skin during rest and exercise

The rhythmic variations in the water evaporation rate (gm ² h ¹1 from the dorsal side of the forearm have heen studied. The evaporaition rate is estimated by calculating the difference between the vapour pressures at two distinet points on a line perpendicular to the evaporative surface. Using autocorrelation technique it is found that the evaporation rate is periodie with a period of around 0.7 s. This value is consistent. al rest as well as prior to profuse sweating in exercise. for all the subjects included in the investigation. During profuse swesting the period becomes slightly longer. It is suggested that the variations in the evaporation rate reflect the periodie activity in the sudomotor nerves.     

Quantitative analysis of the local effect of skin temperature on sweating

Effects of local skin temperature on sweat gland activity were analyzed quantitatively by measuring changes in the rates of thermal sweating and of drug-induced sweating by local heating. The data indicates that a rise in local temperature causes an accelerated increase in the rate of sweat production, the Q10 being around 2.5 regardless of the basal sweat rate with some individual variations. Local heating apparently facilitates transmitter release at the neuroglandular junction and augments glandular responsiveness, their significances being comparable.     

A procedure for the measurement of infant skin conductance and its initial validation using clap induced startle

Studies examining psychophysiologic markers of infant emotional development abound. However, few studies have used skin conductance (SC), though it measure's sympathetic activity, and none have measured SC on infants sitting up and actively engaged with another person, a significant challenge given the measures sensitivity to movement artifact. In this pilot/feasibility study, we present a procedure for measuring infant SC during active engagement with another person who executes a series of startling claps to elicit an SC response. We measured SC on the plantar surface of the foot of seventeen 5-month-old infants. We found unconditioned SC responses that were related to the intensity of physical startle reactions for each clap trial. We also found anticipatory, conditioned SC responses that occurred within 5 s before each clap that occurred when the researcher raised his clasped hands. These conditioned SC responses grew linearly in intensity over trials. We conclude that SC may be a useful addition to the infant researcher's armamentarium and may indeed be used to measure physiologic reactivity in infants even when actively engaged with another person. Addition of SC measurement to research on infant emotion and emotional communication is likely to advance our understanding of the psychophysiologic foundations of infant emotional development.     

Conditioned diminution of the unconditioned skin conductance response

During Pavlovian conditioning the expression of a conditioned response typically serves as evidence that an association between a conditioned stimulus (CS) and an unconditioned stimulus (UCS) has been learned. However, learning-related changes in the unconditioned response (UCR) produced by a predictable UCS can also develop. In the present study, we investigated learning-related reductions in the magnitude of the unconditioned skin conductance response (SCR). Healthy volunteers participated in a differential conditioning study in which one tone (CS+) was paired with a loud white-noise UCS and a second tone (CS-) was presented alone. In addition, probe trials that consisted of UCS presentations paired with the CS+ (CS + UCS) and CS- (CS - UCS), as well as presentations of the UCS alone were included to assess UCR diminution. SCR and participants' expectations of UCS presentation were monitored during conditioning. Greater diminution of the UCR was observed to the UCS when it followed the CS+ compared to when it followed the CS- or was presented alone. Further, UCR amplitude showed an inverse relationship with the participants' ratings of UCS expectancy. However, conditioned UCR diminution was also observed independent of differential UCS expectancies. Our findings demonstrate conditioned diminution of the unconditioned SCR. Further, these findings suggest that although UCR amplitude is modified by conscious expectations of the UCS, conditioned diminution of the UCR can be expressed independent of learning-related changes in these expectations.     

The use of bilateral skin conductance measurement in elucidating stimulus versus response processing influences on the orienting reaction

In three experiments the importance of behavioural consequences as a determinant of the amplitude of the electrodermal response is demonstrated. Bilateral skin conductance responses were examined to same-different stimuli consisting of moderate intensity tones differing in pitch (S1, S2), to a response cue to make a unimanual button-press if the stimulation were judged the same (S3), and to feedback (S4). In the first two experiments in which a right-hand action was required, responses were larger to S2 than S1 on ‘response’, compared with ‘no-response’ trials. This was replicated in the second experiment where the same effect was also found to S3. In the third experiment the hand performing the action was varied; the influence of stimulus consequences on responses to S2 was replicated when the right hand performed the action; when the left hand was involved elevated responses to S2 occurred, irrespective of the perceptual judgement. In all experiments responses tended to be larger on trials where a correct judgement was made. The use of bilateral recording with a unilateral behavioural response confirmed the influence of effector functions on electrodermal responses. Hemispheric influences were contralateral and excitatory. The results were discussed in terms of multiple central determinants on electrodermal responses, the influence of cerebral laterality, and of sympathetic-somatic coupling.     

The heritability of the skin conductance orienting response: a longitudinal twin study

The orienting response is a widely used experimental paradigm that reflects the association between electrodermal activity and psychological processes. The present study examined the genetic and environmental etiology of skin conductance orienting response (SCOR) magnitude in a sample of twins assessed at ages 9-10, 11-13 and 14-16 years. Structural equation modeling at each visit showed that genetic influences explained 56%, 83%, and 48% of the total variance in SCOR at visits 1, 2, and 3, respectively, with the remaining variance explained by non-shared environmental factors. SCOR was moderately stable across ages, with phenotypic correlations between time points ranging from .35 to .45. A common genetic factor explained 36%, 45% and 49% of the variance in SCOR magnitude across development. Additional age-specific genetic effects were found at ages 9-10 and 11-13 years, explaining 18% and 35% of the variance, respectively. The genetic correlations among the three time points were high, ranging from .55 to .73, indicating a substantial continuity in genetic influences from ages 9 to 16. These findings suggest that genetic factors are important influences in SCOR magnitude during late childhood and adolescence.     

Construction,in vitro and in vivo evaluation of an in-house conductance meter for measurement of skin hydration

Different probes are used in dermato-cosmetic research to measure the electrical properties of the skin. The principle governing the choice of the geometry and material of the measuring probe is not well defined in the literature and some device's measuring principles are not accessible for the scientific community. The purpose of this work was to develop a simple inexpensive conductance meter for the objective in vivo evaluation of skin hydration.The conductance meter probe was designed using the basic equation governing wave propagation along Transverse Electromagnetic transmission lines. It consisted of two concentric copper circular electrodes printed on FR4 dielectric material.The performance of the probe was validated by evaluating its measurement depth, its ability to monitor in vitro water sorption–desorption and in vivo skin hydration effect in comparison to that of the Corneometer CM 825. The measurement depth of the probe, 15 μm, was comparable to that of CM 825. The in vitro readings of the probe correlated strongly with the amount of water adsorbed on filter paper. Skin hydration after application of a moisturizer was monitored effectively by the new probe with good correlation to the results of CM 825.In conclusion, a simple probe for evaluating skin hydration was made from off-the-shelf materials and its performance was validated in comparison to a commercially available probe.