Hippocampus in relation to mental sweating response evoked by memory recall and mental calculation: a human electroencephalography study with dipole tracing

A novel lotion formulation of 20% oxybutynin hydrochloride for the treatment of primary palmar hyperhidrosis: A randomized, placebo-controlled, double-blind, phase III study

BACKGROUND

No previous controlled studies have been specifically designed or adequately powered to show the efficacy of topical oxybutynin for palmar hyperhidrosis by using quantitative measures.

OBJECTIVE

To evaluate efficacy of 20% oxybutynin hydrochloride lotion (20% OL) in reducing palmar sweat volume in patients with primary palmar hyperhidrosis (PPHH).

METHODS

In a randomized controlled trial, Japanese patients with PPHH aged 12 years and older received either 20% OL (n = 144) or placebo (n = 140) on both palms once daily for 4 weeks. Palmar sweat volume was measured by the ventilated capsule method. For the primary outcome, response was defined as a reduction of sweat volume of at least 50% from baseline.

RESULTS

At week 4, the responder rate for sweat volume was significantly higher in the 20% OL arm than in the placebo arm (52.8% vs 24.3%, respectively; treatment difference, 28.5% [95% CI, 17.7% to 39.3%]; P < .001). No serious adverse events occurred, and no adverse events led to treatment discontinuation.

LIMITATIONS

The treatment period was only 4 weeks.

CONCLUSIONS

In patients with PPHH, 20% OL is superior to placebo in reducing palmar sweat volume.

Heatstroke risk informing system using wearable perspiration ratemeter on users undergoing physical exercise

We constructed an informing system to users for the heatstroke risk using a wearable perspiration ratemeter and the users' thirst responses. The sweating ratemeter was constructed with a capacitive humidity sensor in the ventilated capsule. The timing point for informing heatstroke risk was decided to change from positive to negative on the second derivative of sweating curve. In addition, a wearable self-identification and -information system of thirst response was constructed with a smartphone. To evaluate the validity of wearable apparatus, we aimed to conduct human experiments of 16 healthy subjects with the step up and down physical exercises. The blood and urine samples of the subjects were collected before and after the 30-min physical exercise. The concentrations of TP, Alb, and RBC increased slightly with the exercise. In contrast, the concentrations of vasopressin in all subjects remarkably increased with the exercise. In almost subjects, they identified their thirst response until several min after the informing for heatstroke risk. In conclusion, the wearable ratemeter and self-information system of thirst response were suitable for informing system of heatstroke risk. The validity of timing point for informing heatstroke risk was confirmed with changes in the thirst response and concentrations of vasopressin in blood.

Real sweating in a virtual stress environment: Investigation of the stress reactivity in people with primary focal hyperhidrosis

Background

Hyperhidrosis (excessive sweating, OMIM %114110) is a complex disorder with multifactorial causes. Emotional strains and social stress increase symptoms and lead to a vicious circle. Previously, we showed significantly higher depression scores, and normal cortisol awakening responses in patients with primary focal hyperhidrosis (PFH). Stress reactivity in response to a (virtual) Trier Social Stress Test (TSST-VR) has not been studied so far. Therefore, we measured sweat secretion, salivary cortisol and alpha amylase (sAA) concentrations, and subjective stress ratings in affected and non-affected subjects in response to a TSST-VR.

Method

In this pilot study, we conducted TSST-VRs and performed general linear models with repeated measurements for salivary cortisol and sAA levels, heart rate, axillary sweat and subjective stress ratings for two groups (diagnosed PFH (n = 11), healthy controls (n = 16)).

Results

PFH patients showed significantly heightened sweat secretion over time compared to controls (p = 0.006), with highest quantities during the TSST-VR. In both groups, sweating (p < 0.001), maximum cortisol levels (p = 0.002), feelings of stress (p < 0.001), and heart rate (p < 0.001) but not sAA (p = 0.068) increased significantly in response to the TSST-VR. However, no differences were detected in subjective ratings, cortisol concentrations and heart rate between PFH patients and controls (p_all > 0.131).

Conclusion

Patients with diagnosed PFH showed stress-induced higher sweat secretion compared to healthy controls but did not differ in the stress reactivity with regard to endocrine or subjective markers. This pilot study is in need of replication to elucidate the role of the sympathetic nervous system as a potential pathway involved in the stress-induced emotional sweating of PFH patients.

Eyes Closing and Drowsiness in Human Subjects Decrease Baseline Galvanic Skin Response and Active Palmar Sweating: Relationship Between Galvanic Skin and Palmar Perspiration Responses

We previously constructed a perspiration ratemeter for the measurement of palmar sweating in human subjects. Although galvanic skin response (GSR) has been used to evaluate emotional responses in human subjects, little is known about the relationships between the phasic and baseline components in GSR and active palmar sweating. From the aforementioned, we aimed to investigate the relationships in human subjects with handgrip exercise and eyes closing or opening. Fifteen healthy volunteers (mean age: 26.9 ± 8.7 years) participated in the present experiments. We investigated the effects of maximal handgrip exercise, eyes closing or opening, and self-awareness of drowsy on the GSR, active palmar sweating, R-R interval in electrocardiograph (ECG), and percentage of α wave in EEG. The faster phasic component in GSR completely agreed with the starting point of active palmar sweating. Handgrip exercise induced significantly faster spike in GSR, active palmar sweating, and decrease in R-R interval in ECG. Eyes closing produced significant decreases in baseline GSR and active palmar sweating in all human subjects. The percentage of α wave in electroencephalograph (EEG) also increased. In contrast, eyes opening increased significantly the baseline GSR and active palmar sweating. In the equivalent electrical model of human skin, the eyes closing-mediated time-dependent decrease in the baseline GSR completely agreed with the hypothesis that the palmar skin voltage only in the model decreased time dependently to 0.4 of the control during 6 min. The self-awareness of drowsy in mid-night working with computer produced similar decreases in baseline GSR and active palmar sweating to the responses with eyes closing in all human subjects. In conclusion, the faster spike in GSR completely agreed with the starting point of active palmar sweating. Eyes closing and opening or self-awareness of drowsy significantly produced changes in baseline GSR and active palmar sweating, which may become useful tools for evaluating clearness or drowsiness in human subjects.

Effects of very high-frequency sound and ultrasound on humans. Part I: Adverse symptoms after exposure to audible very-high frequency sound

Various adverse symptoms resulting from exposure to very high-frequency sound (VHFS) and ultrasound (US) have previously been reported. This study aimed to establish whether these symptoms are experienced under controlled laboratory conditions and are specific to VHFS/US. To do this, participants were exposed to VHFS/US (at frequencies between 13.5 and 20 kHz and sound pressure levels between 82 and 92 dB) and to a 1 kHz reference stimulus, both at 25 dB above their hearing threshold. The VHFS/US and reference stimuli were presented 4 times, each time for 3 min, during which participants performed a sustained attention task, rated their symptom severity, and had their galvanic skin response (GSR) measured to assess their level of anxiety. Prior to exposure, participants were assigned either to a symptomatic or an asymptomatic group, based on their prior history of symptoms that they attributed to VHFS/US. In both groups, overall discomfort ratings were higher in the VHFS/US condition than the reference condition. In the symptomatic group only, difficulty concentrating and annoyance were also rated higher in the VHFS/US than the reference condition. No difference between the two stimulus conditions was seen in performance on the attention task or on average GSRs for either group.

Preservation of cognitive performance with age during exertional heat stress under low and high air velocity

Older adults may be at greater risk for occupational injuries given their reduced capacity to dissipate heat, leading to greater thermal strain and potentially cognitive decrements. Purpose. To examine the effects of age and increased air velocity, during exercise in humid heat, on information processing and attention. Methods. Nine young (24 ± 1 years) and 9 older (59 ± 1 years) males cycled 4 × 15 min (separated by 15 min rest) at a fixed rate of heat production (400 W) in humid heat (35°C, 60% relative humidity) under 0.5 (low) and 3.0 (high) m·s⁻¹ air velocity wearing coveralls. At rest, immediately following exercise (end exercise), and after the final recovery, participants performed an abbreviated paced auditory serial addition task (PASAT, 2 sec pace). Results. PASAT numbers of correct responses at end exercise were similar for young (low = 49 ± 3; high = 51 ± 3) and older (low = 46 ± 5; high = 47 ± 4) males and across air velocity conditions, and when scored relative to age norms. Psychological sweating, or an increased sweat rate with the administration of the PASAT, was observed in both age groups in the high condition. Conclusion. No significant decrements in attention and speeded information processing were observed, with age or altered air velocity, following intermittent exercise in humid heat.

Relationship between Sympathetic Skin Responses and Auditory Hypersensitivity to Different Auditory Stimuli

[Purpose] Auditory hypersensitivity has been widely reported in patients with autism spectrum disorders. However, the neurological background of auditory hypersensitivity is currently not clear. The present study examined the relationship between sympathetic nervous system responses and auditory hypersensitivity induced by different types of auditory stimuli. [Methods] We exposed 20 healthy young adults to six different types of auditory stimuli. The amounts of palmar sweating resulting from the auditory stimuli were compared between groups with (hypersensitive) and without (non-hypersensitive) auditory hypersensitivity. [Results] Although no group × type of stimulus × first stimulus interaction was observed for the extent of reaction, significant type of stimulus × first stimulus interaction was noted for the extent of reaction. For an 80 dB-6,000 Hz stimulus, the trends for palmar sweating differed between the groups. For the first stimulus, the variance became larger in the hypersensitive group than in the non-hypersensitive group. [Conclusion] Subjects who regularly felt excessive reactions to auditory stimuli tended to have excessive sympathetic responses to repeated loud noises compared with subjects who did not feel excessive reactions. People with auditory hypersensitivity may be classified into several subtypes depending on their reaction patterns to auditory stimuli.

Hands and feet: physiological insulators, radiators and evaporators

The purpose of this review is to describe the unique anatomical and physiological features of the hands and feet that support heat conservation and dissipation, and in so doing, highlight the importance of these appendages in human thermoregulation. For instance, the surface area to mass ratio of each hand is 4-5 times greater than that of the body, whilst for each foot, it is ~3 times larger. This characteristic is supported by vascular responses that permit a theoretical maximal mass flow of thermal energy of 6.0 W (136 W m(2)) to each hand for a 1 °C thermal gradient. For each foot, this is 8.5 W (119 W m(2)). In an air temperature of 27 °C, the hands and feet of resting individuals can each dissipate 150-220 W m(2) (male-female) of heat through radiation and convection. During hypothermia, the extremities are physiologically isolated, restricting heat flow to <0.1 W. When the core temperature increases ~0.5 °C above thermoneutral (rest), each hand and foot can sweat at 22-33 mL h(-1), with complete evaporation dissipating 15-22 W (respectively). During heated exercise, sweat flows increase (one hand: 99 mL h(-1); one foot: 68 mL h(-1)), with evaporative heat losses of 67-46 W (respectively). It is concluded that these attributes allow the hands and feet to behave as excellent radiators, insulators and evaporators.

Brain stem representation of thermal and psychogenic sweating in humans

Functional MRI was used to identify regions in the human brain stem activated during thermal and psychogenic sweating. Two groups of healthy participants aged 34.4 ± 10.2 and 35.3 ± 11.8 years (both groups comprising 1 woman and 10 men) were either heated by a water-perfused tube suit or subjected to a Stroop test, while they lay supine with their head in a 3-T MRI scanner. Sweating events were recorded as electrodermal responses (increases in AC conductance) from the palmar surfaces of fingers. Each experimental session consisted of two 7.9-min runs, during which a mean of 7.3 ± 2.1 and 10.2 ± 2.5 irregular sweating events occurred during psychogenic (Stroop test) and thermal sweating, respectively. The electrodermal waveform was used as the regressor in each subject and run to identify brain stem clusters with significantly correlated blood oxygen level-dependent signals in the group mean data. Clusters of significant activation were found with both psychogenic and thermal sweating, but a voxelwise comparison revealed no brain stem cluster whose signal differed significantly between the two conditions. Bilaterally symmetric regions that were activated by both psychogenic and thermal sweating were identified in the rostral lateral midbrain and in the rostral lateral medulla. The latter site, between the facial nuclei and pyramidal tracts, corresponds to a neuron group found to drive sweating in animals. These studies have identified the brain stem regions that are activated with sweating in humans and indicate that common descending pathways may mediate both thermal and psychogenic sweating.

Regional variations in transepidermal water loss, eccrine sweat gland density, sweat secretion rates and electrolyte composition in resting and exercising humans

Literature from the past 168 years has been filtered to provide a unified summary of the regional distribution of cutaneous water and electrolyte losses. The former occurs via transepidermal water vapour diffusion and secretion from the eccrine sweat glands. Daily insensible water losses for a standardised individual (surface area 1.8 m2) will be 0.6-2.3 L, with the hands (80-160 g.h-1) and feet (50-150 g.h-1) losing the most, the head and neck losing intermediate amounts (40-75 g.h-1) and all remaining sites losing 15-60 g.h-1. Whilst sweat gland densities vary widely across the skin surface, this same individual would possess some 2.03 million functional glands, with the highest density on the volar surfaces of the fingers (530 glands.cm-2) and the lowest on the upper lip (16 glands.cm-2). During passive heating that results in a resting whole-body sweat rate of approximately 0.4 L.min-1, the forehead (0.99 mg.cm-2.min-1), dorsal fingers (0.62 mg.cm-2.min-1) and upper back (0.59 mg.cm-2.min-1) would display the highest sweat flows, whilst the medial thighs and anterior legs will secrete the least (both 0.12 mg.cm-2.min-1). Since sweat glands selectively reabsorb electrolytes, the sodium and chloride composition of discharged sweat varies with secretion rate. Across whole-body sweat rates from 0.72 to 3.65 mg.cm-2.min-1, sodium losses of 26.5-49.7 mmol.L-1 could be expected, with the corresponding chloride loss being 26.8-36.7 mmol.L-1. Nevertheless, there can be threefold differences in electrolyte losses across skin regions. When exercising in the heat, local sweat rates increase dramatically, with regional glandular flows becoming more homogeneous. However, intra-regional evaporative potential remains proportional to each local surface area. Thus, there is little evidence that regional sudomotor variations reflect an hierarchical distribution of sweating either at rest or during exercise.

Sudomotor responses from glabrous and non-glabrous skin during cognitive and painful stimulations following passive heating

AIM

It is widely accepted that thermal and psychological sweating are independently controlled and respectively restricted to non-glabrous (hairy) and glabrous skin. These assumptions were evaluated in six experiments conducted across eight body segments, in which 38 glabrous and non-glabrous skin surfaces were investigated.

METHODS

Sweating was measured in 30 passively heated individuals using ventilated sweat capsules, with passive heating used to first establish steady-state sweating, averaging 0.30 mg cm(-2) min(-1) (±0.03) across all sites, prior to the application of cognitive and painful stimuli.

RESULTS

These non-thermal (psychological) stimulations significantly increased sweat secretion at more than 70% of the sites investigated [cognitive: 28 of 38 sites (P < 0.05); pain: 23 of 32 sites (P < 0.05)], eliciting peak sweat rates averaging 0.51 mg cm(-2) min(-1) (±0.05) and 0.47 mg cm(-2) min(-1) (±0.4 respectively) across all sites. Furthermore, non-thermal sweating was evident from both the glabrous and non-glabrous surfaces and occurred without mean body or local skin temperatures changes (P > 0.05). Indeed, neither thermal nor psychological sweating was restricted to discrete skin surfaces, and there were no consistent sudomotor differences between these two skin classifications. Finally, at no site was thermal sweating inhibited during a non-thermal stimulation.

CONCLUSION

These generalized sudomotor responses challenge the hypotheses that glabrous skin sweating is driven by psychological stimuli, and that thermal sweating is a phenomenon restricted to the non-glabrous skin surfaces.

State Anxiety Dependent on Perspiration during Mental Stress and Deep Inspiration

In this study, we focused on two types of perspiration, one triggered by anticipatory anxiety and the other by voluntary deep inspiration. We have previously found that the anticipation of anxiety causes increases of respiratory frequency, and that these increases are related to an activation of the temporal pole and amygdala in humans. Our interest is in the difference between the two natures of perspiration, both of which are closely related to respiratory responses. The level of sweating responses did not differ between deep and active inspiration or between three trials. This means that there was no habituation with repetitive trials for voluntary breathing. On the other hand, sweating responses during anticipation of anxiety showed habituation with repetitive trials. Habituation and nonhabituation differences with respect to these two characteristics of perspiration could be the result of differences in the related central networks. The former might be involved cortical structures associated with conscious changes of respiration. The latter was induced unconsciously, and this unconscious response is similar to the respiratory response during anticipatory anxiety, which may be related to the activation of the limbic system. Further, there was a positive correlation found between the amount of perspiration response and the state anxiety scores in deep inspiration, and also in trial 1 of the anticipatory anxiety experiment. Both types of responses were related to the individual state anxiety scores, and this may contribute to the defense mechanism with regard to adjustments to changes in the outer environment and situations.

Mental strain in medical students during simulator training measured by forehead sweating

Forehead sweating developed in 78% of medical students when they attempted tracheal intubation on a simulator, and increased during subsequent attempts if the first attempt was not successful. Thus, forehead sweating may be a useful index of mental strain.

Effects of exercise intensity, posture, pressure on the back and ambient temperature on palmar sweating responses due to handgrip exercises in humans

We have, by using newly developed ratemeters, attempted to examine the effects of exercise intensity, posture, pressure on the skin of the back, and ambient hyperthermic conditions (approximately 30 degrees C) on the 5-s handgrip exercise-mediated responses of active palmar sweating in humans. Thirty-five right-handed male (n=5) and female (n=30) volunteer students (20.2+/-1.3 years old) participated in the present study. Oral explanation of only the isometric handgrip exercise (IHG) caused a rapid and oscillatory response (pre-operational) of active palmar sweating in almost all subjects (10 of 14 subjects). Performing the IHG for 5-s caused a significant increase in active sweating rate (operation-mediated response) in both ipsi- and contra-lateral palmar surfaces of the thumbs of all subjects. The operation-mediated responses of active palmar sweating to the IHG were reproducible, resulting in no habituation. The increase of operation-mediated responses to the IHG was dependent upon exercise intensity (100-25% maximal voluntary contractions). The IHG-mediated ipsi- and contra-lateral responses of active palmar sweating were significantly decreased by changing the body posture from a seated to a supine position or by pressing the skin of the back. Ambient hyperthermic conditions (approximately 30 degrees C) for 60 min also resulted in a significant decrease in the back-pressure-dependent reduction of the operation-mediated responses of active palmar sweating to the IHG. In conclusion, in order to optimize the precision and reproducibility of clinical tests involving palmar sweating responses, it is important that subjects maintain a constant handgrip force and posture and that ambient temperature be kept under normothermic conditions.

Arithmetic calculation, deep inspiration or handgrip exercise-mediated pre-operational active palmar sweating responses in humans

We examined the effects of repetitive mental stimulation such as arithmetic calculations with sequential subtraction or physical tasks such as handgrip exercise and deep breathing on active palmar sweating responses in humans. Thirty-three healthy, male and female volunteer students (20.4+/-2.1 years) participated in the present study. The responses of active palmar sweating were evaluated by using the newly developed ratemeter. The galvanic skin response (GSR) was also recorded in 10 out of 33 subjects. The oral explanation of the stimulation or tasks caused a rapid and wavy active palmar sweating response. The pre-operational responses of active palmar sweating to the stimulation or tasks were also observed by the GSR recording. The mental stimulation- and physical tasks-mediated pre-operational responses were significantly reduced by the trials. The mental stimulation or physical tasks also caused a rapid and oscillatory response of active palmar sweating during operation of the stimulation or tasks. The operation-mediated responses to physical tasks were observed ipsilaterally and contralaterally. The physical task-mediated responses were also reproducible, resulting in no habituation. In contrast, the operation-mediated responses to mental stimulation were reduced significantly by the trials, resulting in a marked habituation. The findings suggest that the mental stimulation- and physical tasks-mediated pre-operational responses of active palmar sweating obtained by using the newly developed ratemeter will make useful tests for evaluating neuronal activity of limbic system including amygdala, sympathetic sudomotor activity in the palmar skin and functional properties of the palmar sweat glands.

Skin potential response in letter recognition task as an alternative communication channel for individuals with severe motor disability

OBJECTIVES

Skin potential responses (SPRs) to target and non-target stimuli in letter recognition tasks were studied to evaluate their potential as communication channels for individuals with severe motor disability.

METHODS

SPRs were recorded from the palm or sole of 5 subjects with cerebral palsy and 6 healthy subjects. Subjects discriminated target letters from non-target ones in a random sequence of single letters. In Task 1, subjects made a behavioral response upon presentation of the target. In Task 2, the target letters were presented as "go" or "nogo" signals.

RESULTS

For target letters, irrespective of behavioral requirements ("go" or "nogo"), skin potential waves frequently occurred with latency consistent with the sympathetic skin response (SSR) latency, and were regarded as SPRs evoked by target stimuli. In Task 1, the occurrence rate of the SPR was 47% for target, and 4% for non-target stimuli. In Task 2, the SPR occurred in 34% of "go" target, 29% of "nogo" target, and 2% of non-target stimuli.

CONCLUSIONS

SPRs with SSR latency are potentially useful in controlling signals of communication tools for individuals with severe motor disability.

Generator sources of EEG large waves elicited by mental stress of memory recall or mental calculation

Preceding mental sweating response (MSR) during mental stress, small wavelets and large waves are observed on EEG. In the present study, locations of current sources of the large waves were estimated. The results revealed that the current dipole was estimated around the orbits, reflecting activity of the eyelid or eye muscles.