Validity of the 1984 Interim Guidelines on Airborne Ultrasound and Gaps in the Current Knowledge.

ABSTRACT: Airborne ultrasound is used for various purposes both in industrial and public settings, as well as being produced as a by-product by a range of sources. The International Radiation Protection Association (IRPA) published interim guidelines on limiting human exposure to airborne ultrasound in 1984, based on the limited scientific evidence that was available at that time. In order to investigate whether research since 1984 requires the development of revised exposure guidelines we considered (a) within the context of ultrasound exposure the relevance to health of the biological endpoints/mechanisms listed in the IRPA guidelines, (b) the validity of the exposure limits, and (c) whether there are biological endpoints/mechanisms not covered in the guidelines. The analysis of the available evidence showed that the biological endpoints that form the basis of the guidelines are relevant to health and the guidelines provide limits of exposure based on the evidence that was available at the time. However, the IRPA limits and their associated dosimetry were based on limited evidence, which may not be considered as scientifically substantiated. Further, there is no substantiated evidence of biological endpoints/mechanisms not covered by the IRPA guidelines. These two observations could mean that IRPA's limits are too low or too high. Research since the IRPA guidelines has made some improvements in the knowledge base, but there are still significant data gaps that need to be resolved before a formal revision of the guidelines can be made by ICNIRP, including research needs related to health outcomes and improved dosimetry. This statement makes a number of recommendations for future research on airborne ultrasound.

How to improve IARC's RF-EMF cancer hazard communication.

A crucial aspect of IARC's evaluation of the relative carcinogenicity of agents is the communication of its conclusions. The present paper addressed the experimental risk perception literature pertaining to IARC's radiofrequency electromagnetic field evaluation communication, and derived specific recommendations for improving it.

ICNIRP Statement on Short Wavelength Light Exposure from Indoor Artificial Sources and Human Health.

ABSTRACT: Concerns have been raised about the possibility of effects from exposure to short wavelength light (SWL), defined here as 380-550 nm, on human health. The spectral sensitivity of the human circadian timing system peaks at around 480 nm, much shorter than the peak sensitivity of daytime vision (i.e., 555 nm). Some experimental studies have demonstrated effects on the circadian timing system and on sleep from SWL exposure, especially when SWL exposure occurs in the evening or at night. The International Commission on Non-Ionizing Radiation Protection (ICNIRP) has identified a lack of consensus among public health officials regarding whether SWL from artificial sources disrupts circadian rhythm, and if so, whether SWL-disrupted circadian rhythm is associated with adverse health outcomes. Systematic reviews of studies designed to examine the effects of SWL on sleep and human health have shown conflicting results. There are many variables that can affect the outcome of these experimental studies. One of the main problems in earlier studies was the use of photometric quantities as a surrogate for SWL exposure. Additionally, the measurement of ambient light may not be an accurate measure of the amount of light impinging on the intrinsically photosensitive retinal ganglion cells, which are now known to play a major role in the human circadian timing system. Furthermore, epidemiological studies of long-term effects of chronic SWL exposure per se on human health are lacking. ICNIRP recommends that an analysis of data gaps be performed to delineate the types of studies needed, the parameters that should be addressed, and the methodology that should be applied in future studies so that a decision about the need for exposure guidelines can be made. In the meantime, ICNIRP supports some recommendations for how the quality of future studies might be improved.

Genetic Transformation of Plasmid DNA into Escherichia coli Using High Frequency Electromagnetic Energy.

We present a novel technique of genetic transformation of bacterial cells mediated by high frequency electromagnetic energy (HF EME). Plasmid DNA, pGLO (5.4 kb), was successfully transformed into Escherichia coli JM109 cells after exposure to 18 GHz irradiation at a power density between 5.6 and 30 kW m-2 for 180 s at temperatures ranging from 30 to 40 °C. Transformed bacteria were identified by the expression of green fluorescent protein (GFP) using confocal scanning microscopy (CLSM) and flow cytometry (FC). Approximately 90.7% of HF EME treated viable E. coli cells exhibited uptake of the pGLO plasmid. The interaction of plasmid DNA with bacteria leading to transformation was confirmed by using cryogenic transmission electron microscopy (cryo-TEM). HF EME-induced plasmid DNA transformation was shown to be unique, highly efficient, and cost-effective. HF EME-induced genetic transformation is performed under physiologically friendly conditions in contrast to existing techniques that generate higher temperatures, leading to altered cellular integrity. This technique allows safe delivery of genetic material into bacterial cells, thus providing excellent prospects for applications in microbiome therapeutics and synthetic biology.

Assessing the safety of new germicidal far-UVC technologies.

The COVID-19 pandemic underscored the crucial importance of enhanced indoor air quality control measures to mitigate the spread of respiratory pathogens. Far-UVC is a type of germicidal ultraviolet technology, with wavelengths between 200 and 235 nm, that has emerged as a highly promising approach for indoor air disinfection. Due to its enhanced safety compared to conventional 254 nm upper-room germicidal systems, far-UVC allows for whole-room direct exposure of occupied spaces, potentially offering greater efficacy, since the total room air is constantly treated. While current evidence supports using far-UVC systems within existing guidelines, understanding the upper safety limit is critical to maximizing its effectiveness, particularly for the acute phase of a pandemic or epidemic when greater protection may be needed. This review article summarizes the substantial present knowledge on far-UVC safety regarding skin and eye exposure and highlights research priorities to discern the maximum exposure levels that avoid adverse effects. We advocate for comprehensive safety studies that explore potential mechanisms of harm, generate action spectra for crucial biological effects and conduct high-dose, long-term exposure trials. Such rigorous scientific investigation will be key to determining safe and effective levels for far-UVC deployment in indoor environments, contributing significantly to future pandemic preparedness and response.

Translocation and fate of nanospheres in pheochromocytoma cells following exposure to synchrotron-sourced terahertz radiation.

The routes by which foreign objects enter cells is well studied; however, their fate following uptake has not been explored extensively. Following exposure to synchrotron-sourced (SS) terahertz (THz) radiation, reversible membrane permeability has been demonstrated in eukaryotic cells by the uptake of nanospheres; nonetheless, cellular localization of the nanospheres remained unclear. This study utilized silica core-shell gold nanospheres (AuSi NS) of diameter 50 ± 5 nm to investigate the fate of nanospheres inside pheochromocytoma (PC 12) cells following SS THz exposure. Fluorescence microscopy was used to confirm nanosphere internalization following 10 min of SS THz exposure in the range 0.5-20 THz. Transmission electron microscopy followed by scanning transmission electron microscopy energy-dispersive spectroscopic (STEM-EDS) analysis was used to confirm the presence of AuSi NS in the cytoplasm or membrane, as single NS or in clusters (22% and 52%, respectively), with the remainder (26%) sequestered in vacuoles. Cellular uptake of NS in response to SS THz radiation could have suitable applications in a vast number of biomedical applications, regenerative medicine, vaccines, cancer therapy, gene and drug delivery.

Cannabidiol as a Treatment for Neurobiological, Behavioral, and Psychological Symptoms in Early-Stage Dementia: A Double-Blind, Placebo-Controlled Clinical Trial Protocol.

Rationale: The slowing of disease progression in dementia in the early stages of diagnosis is paramount to improving the quality of life for those diagnosed and their support networks. Accumulating evidence suggests that CBD, a constituent of Cannabis sativa, is associated with neuroprotective, neuroendocrine, and psychotherapeutic effects, suggesting that it may be beneficial to dementia treatment. However, no published human study to date has examined this possibility. This trial aims to determine whether daily treatment with CBD over a 12-week period is associated with improved neurobiological, behavioral, and psychological outcomes in individuals living with early-stage dementia. Methods: Sixty participants with early-stage dementia will be recruited for a randomized, double-blind, placebo-controlled clinical trial. Participants will be randomized into either 99.9% pure CBD or placebo treatment conditions and administered two capsules per day for 12 weeks. Participants will commence a 200 mg/day dose for 2 weeks before escalating to 300 mg/day for the remaining 10 weeks. Neuroimaging and blood-based neuroendocrine profiles will be assessed at baseline and post-treatment. Psychological and behavioral symptoms will be assessed at baseline, 6 weeks, and post-treatment. Monitoring of health and side-effects will be conducted through weekly home visits. Discussion: This study is among the first to investigate the effects of isolated CBD in improving neuroanatomical and neuroendocrine changes, alongside psychological symptoms, during the early stages of dementia diagnosis. The outcomes of this trial have the capacity to inform a potential novel and accessible treatment approach for individuals living with early-stage dementia, and in turn, improve quality of life, prognoses, and treatment outcomes. Trial Registration: This trial has been registered with the Therapeutic Goods Administration (CT-2020-CTN-03849-1v2) and the Australian and New Zealand Clinical Trials Registry (ACTRN12621001364864).

Localization of nanospheres in pheochromocytoma-like cells following exposure to high-frequency electromagnetic fields at 18 GHz.

Exposure to high-frequency (HF) electromagnetic fields (EMFs) at 18 GHz was previously found to induce reversible cell permeabilization in eukaryotic cells; however, the fate of internalized foreign objects inside the cell remains unclear. Here, silica core-shell gold nanospheres (Au NS) of 20 ± 5 nm diameter were used to study the localization of Au NS in pheochromocytoma (PC 12) cells after exposure to HF EMFs at 18 GHz. Internalization of Au NS was confirmed using fluorescence microscopy and transmission electron microscopy. Analysis based on corresponding scanning transmission electron microscopy energy-dispersive spectroscopy revealed the presence of the Au NS free within the PC 12 cell membrane, cytoplasm, enclosed within intracellular vesicles and sequestered in vacuoles. The results obtained in this work highlight that exposure to HF EMFs could be used as an efficient technique with potential for effective delivery of drugs, genetic material, and nanomaterials into cells for the purpose of cellular manipulation or therapy.

Mobile phone carrying locations and risk perception of men: A cross-sectional study.

Little was known about the relationship between carrying mobile phone handsets by men and their risk perception of radiofrequency-electromagnetic field (RF-EMF) exposure due to carrying handsets close to the body. This study aimed to determine where men usually carried their handsets and to assess the relationship to risk perception of RF-EMF. Participants completed a self-administered questionnaire about mobile phone use, handset carrying locations, and levels of risk perception to RF-EMF. Data were analysed using linear regression models to examine if risk perception differed by mobile phone carrying location. The participants were 356 men, aged 18-72 years. They owned a mobile phone for 2-29 years, with over three quarters (78.7%) having a mobile phone for over 20 years. The most common locations that men kept their handsets when they were 'indoors' were: on a table/desk (54.0%) or in close contact with the body (34.7%). When outside, 54.0% of men kept the handset in the front trouser pocket. While making or receiving calls, 85.0% of men held their mobile phone handset against the head and 15.0% either used earphones or loudspeaker. Men who carried their handset in close contact with the body perceived higher risks from RF-EMF exposure compared to those who kept it away from the body (p<0.01). A substantial proportion of men carried their mobile phone handsets in close proximity to reproductive organs i.e. front pocket of trousers (46.5%). Men who kept their handset with the hand (p < .05), and those who placed it in the T-shirt pocket (p < .05), while the phone was not in use, were more likely to perceive health risks from their behaviour, compared to those who kept it away from the body. However, whether this indicates a causal relationship, remains open.

Effect of ambient lighting on frequency dependence in transcranial electrical stimulation-induced phosphenes.

Inconsistencies have been found in the relationship between ambient lighting conditions and frequency-dependence in transcranial electric stimulation (tES) induced phosphenes. Using a within-subjects design across lighting condition (dark, mesopic [dim], photopic [bright]) and tES stimulation frequency (10, 13, 16, 18, 20 Hz), this study determined phosphene detection thresholds in 24 subjects receiving tES using an FPz-Cz montage. Minima phosphene thresholds were found at 16 Hz in mesopic, 10 Hz in dark and 20 Hz in photopic lighting conditions, with these thresholds being substantially lower for mesopic than both dark (60% reduction) and photopic (56% reduction), conditions. Further, whereas the phosphene threshold-stimulation frequency relation increased with frequency in the dark and decreased with frequency in the photopic conditions, in the mesopic condition it followed the dark condition relation from 10 to 16 Hz, and photopic condition relation from 16 to 20 Hz. The results clearly demonstrate that ambient lighting is an important factor in the detection of tES-induced phosphenes, and that mesopic conditions are most suitable for obtaining overall phosphene thresholds.

The profile of unusual beliefs associated with metacognitive thinking and attributional styles.

Cognitive interpretations of daily events may differ in people from the general population who hold unusual beliefs. It is also important to understand whether different belief profiles exist to appreciate which patterns of beliefs are less psychologically healthy. Cluster analysis was used to form unusual belief profiles in a general population sample (n = 578; Mage  = 22 years, SD = 6.98; 80% female) across paranoid, paranormal, and magical ideation beliefs, and we assessed whether they differed in attribution style and metacognitive beliefs about worry. Four clusters were formed: low on all measures (low all); high on all measures (high all); comparably higher on paranormal beliefs (paranormal group); and comparably higher on paranoid beliefs (paranoid group). For total Metacognitions Questionnaire-30, the high all and high paranoid clusters did not differ, and both clusters scored higher than the high paranormal group, who all scored higher than the low all cluster. For attributional styles (Attributional Styles Questionnaire), lower scores on internal positive attribution were found for the high all and high paranoid clusters compared to the low all and high paranormal clusters. The high paranormal cluster had higher scores than the high paranoid cluster on self-serving bias. Differences in attributional style appeared to be driven by mental health diagnosis. Our results suggest different profiles of unusual beliefs are detectable in the general population that differ in their metacognitive beliefs and perceived causation of events in their environment. Future studies investigating delusional proneness need to consider multiple unusual beliefs as well as assessing mood state and distress.

Acute effects of Δ9-tetrahydrocannabinol and cannabidiol on auditory mismatch negativity.

RATIONALE: Mismatch negativity (MMN) is a candidate endophenotype for schizophrenia subserved by N-methyl-D-aspartate receptor (NMDAR) function and there is increasing evidence that prolonged cannabis use adversely affects MMN generation. Few human studies have investigated the acute effects of cannabinoids on brain-based biomarkers of NMDAR function and synaptic plasticity. OBJECTIVES: The current study investigated the acute effects of Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) alone and in combination on the mismatch negativity (MMN). METHODS: In a randomised, double-blind, crossover placebo-controlled study, 18 frequent and 18 less-frequent cannabis users underwent 5 randomised drug sessions administered via vaporiser: (1) placebo; (2) THC 8 mg; (3) CBD 400 mg; (4) THC 8 mg + CBD 4 mg [THC + CBDlow]; (5) THC 12 mg + CBD 400 mg [THC + CBDhigh]. Participants completed a multifeature MMN auditory oddball paradigm with duration, frequency and intensity deviants (6% each). RESULTS: Relative to placebo, both THC and CBD were observed to increase duration and intensity MMN amplitude in less-frequent users, and THC also increased frequency MMN in this group. The addition of low-dose CBD added to THC attenuated the effect of THC on duration and intensity MMN amplitude in less-frequent users. The same pattern of effects was observed following high-dose CBD added to THC on duration and frequency MMN in frequent users. CONCLUSIONS: The pattern of effects following CBD combined with THC on MMN may be subserved by different underlying neurobiological interactions within the endocannabinoid system that vary as a function of prior cannabis exposure. These results highlight the complex interplay between the acute effects of exogenous cannabinoids and NMDAR function. Further research is needed to determine how this process normalises after the acute effects dissipate and following repeated acute exposure.

Wi-fi related radiofrequency electromagnetic fields (RF-EMF): a pilot experimental study of personal exposure and risk perception.

The impact of providing people with an objectively measured personal radiofrequency electromagnetic fields (RF-EMF) exposure information on the risk perception of people is not well understood. We conducted an experimental study, among three groups of participants, to investigate the risk perception of people towards RF-EMF from Wi-Fi sources (ISM 2.4 GHz) by providing participants with either basic text, precautionary information, or a summary of their personal RF-EMF exposure measurement levels. Participants provided with personal RF-EMF exposure measurement information were more confident in protecting themselves from RF-EMF exposure, compared to those provided with only basic information. Nonetheless, neither the exposure perception nor the risk perception of people to Wi-Fi related RF-EMF differed by the type of information provided. The measured Wi-Fi signal levels were far below international exposure limits. Furthermore, self-rated levels of personal RF-EMF exposure perception were not associated with objectively measured RF-EMF exposure levels. Providing people with objectively measured information may help them build confidence in protecting themselves from Wi-Fi related RF-EMF exposure.

The Effect of GSM Electromagnetic Field Exposure on the Waking Electroencephalogram: Methodological Influences.

Although there is consistent evidence that exposure to radiofrequency electromagnetic fields (RF-EMF) increases the spontaneous resting alpha spectral power of the electroencephalogram (EEG), the reliability of this evidence is uncertain as some studies have also failed to observe this effect. The present study aimed to determine whether the effect of RF-EMF exposure on EEG alpha power depends on whether EEG is derived from eyes open or closed conditions and assessed earlier (<5-min) versus later (>25-min) in the exposure interval. Thirty-six adults participated in three experimental sessions, each involving one exposure: "Sham," "Low," and "High" RF-EMF corresponding to peak spatial specific absorption rates averaged over 10 g of 0, 1, and 2 W/kg, respectively. Resting EEG was recorded at baseline (no exposure), during, and after exposure. Alpha power increase was found to be greater for the eyes open than eyes closed EEG during both the High (P = 0.04) and Low (P = 0.04) RF-EMF exposures. There was also a trend toward it being larger at the end, versus the start of the "High" 30-min exposure (P < 0.01; eyes open condition). This suggests that the use of eyes closed conditions, and insufficient RF-EMF exposure durations, are likely explanations for the failure of some studies to detect an RF-EMF exposure-related increase in alpha power, as such methodological choices decrease signal-to-noise ratios and increase type II error.

Retinal and Cortical Contributions to Phosphenes During Transcranial Electrical Current Stimulation.

It is generally believed that the phosphenes induced by transcranial electric current stimulation (tECS) are a product of retinal activation, even when electrode placement is directly over the primary visual cortex. However, the origins of these tECS-induced phosphenes have not yet been conclusively determined. In this study, phosphene detection thresholds using an FPz-Oz montage were compared with those from (i) an Oz-Cz montage to determine whether prefrontal regions, such as the retina, contribute to phosphenes and (ii) an FPz-Cz montage to determine whether the visual cortex in the occipital lobe contributes to phosphenes. Twenty-two participants received transcranial current stimulation with each of these montages (as well as a T3-T4 montage included for exploratory purposes) at 6, 10, 16, 20, 24, 28, and 32 Hz. To estimate differences in current density at the retina and occipital lobe across montages, modeling of current density at phosphene thresholds was measured across 20 head models. Consistent with the proposal that tECS-induced phosphenes are generated in the retina, increasing current density near the retina (FPz-Oz relative to Oz-Cz montage) reduced phosphene thresholds. However, increasing current density near the occipital cortex (FPz-Oz relative to FPz-Cz montage) also reduced phosphene thresholds while also requiring less current density at the retina according to the modeling estimates. This suggests that tECS of this occipital cortex also contributed to phosphene perception. © 2020 Bioelectromagnetics Society.

Effects of Acceleration-Induced Reductions in Retinal and Cerebral Oxygenation on Human Performance.

BACKGROUND: Ischemic hypoxia induced by suprathreshold G-force loading can adversely affect vision, cognition, and lead to loss of consciousness (LOC). The purpose of this study was to determine whether reductions in cerebral oxygenation, caused by subthreshold G-forces (up to 4 Gz and of limited durations that do not lead to LOC), would affect visual perception and working memory performance.METHODS: Sixteen subjects performed visual perception and working memory tasks both before and during Gz exposures (1, 2.2, 3, 4 with leg pressurization, 4 with leg and abdomen pressurization) within a human-use centrifuge.RESULTS: As measured using near-infrared spectroscopy, blood oxygenation over medial prefrontal cortex was similar in the 1 and 2.2 Gz conditions, but was reduced to a similar extent in the 3 and 4 Gz conditions. In parallel, visual perception accuracy was reduced in the 3 and 4 Gz conditions, with no difference between the 3 and 4 Gz conditions. No change in reaction time was seen. Conversely, neither accuracy nor reaction time changes were observed for the visual working memory task.DISCUSSION: These results indicate that although visual working memory is not affected, the ability to visually discriminate between stimuli is reduced at G-forces as low as 3 and 4 Gz. This may have important ramifications for pilots who are routinely subjected to such forces.Croft RJ, Klegrd R, Tribukait A, Taylor NAS, Eiken O. Effects of acceleration-induced reductions in retinal and cerebral oxygenation on human performance. Aerosp Med Hum Perform. 2021; 92(2):7582.

Translocation of silica nanospheres through giant unilamellar vesicles (GUVs) induced by a high frequency electromagnetic field.

Membrane model systems capable of mimicking live cell membranes were used for the first time in studying the effects arising from electromagnetic fields (EMFs) of 18 GHz where membrane permeability was observed following exposure. A present lack of understanding of the mechanisms that drive such a rapid change in membrane permeabilization as well as any structural or dynamic changes imparted on biomolecules affected by high-frequency electromagnetic irradiation limits the use of 18 GHz EMFs in biomedical applications. A phospholipid, 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) labelled with a fluorescent marker 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(lissamine rhodamine B sulfonyl) (rhodamine-DOPE) was used in constructing the giant unilamellar vesicles (GUVs). After three cycles of exposure, enhanced membrane permeability was observed by the internalisation of hydrophilic silica nanospheres of 23.5 nm and their clusters. All-atom molecular dynamics simulations of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membranes exposed to high frequency electric fields of different field strengths showed that within the simulation timeframe only extremely high strength fields were able to cause an increase in the interfacial water dynamics characterized by water dipole realignments. However, a lower strength, high frequency EMF induced changes of the water hydrogen bond network, which may contribute to the mechanisms that facilitate membrane permeabilization in a longer timeframe.

Hyperthermia, but not dehydration, alters the electrical activity of the brain.

PURPOSE: Whole-body thermal and hydration clamps were used to evaluate their independent and combined impact on the electrical activity of the brain. It was hypothesised that those stresses would independently modify the electroencephalographic (EEG) responses, with those changes being greater when both stresses were superimposed. METHODS: Alpha and beta spectral data (eyes closed) were collected from the frontal, central-parietal and occipital cortices of both hemispheres in resting, healthy and habitually active males (N = 8; mean age 25 years). Three dehydration states were investigated (euhydrated and 3% and 5% mass decrements) in each of two thermal states (normothermia [mean body temperature 36.3 °C] and moderate hyperthermia [38.4 °C]). The combination of those passively induced states yielded six levels of physiological strain, with the EEG data from each level separately examined using repeated-measures ANOVA with planned contrasts. RESULTS: When averaged across the frontal cortices, alpha power was elevated relative to the occipital cortices during moderate hyperthermia (P = 0.049). Conversely, beta power was generally reduced during hyperthermia (P = 0.013). Neither the alpha nor beta power spectra responded to dehydration, nor did dehydration elevate the heat-induced responses (P > 0.05). CONCLUSION: Moderate hyperthermia, but neither mild nor moderate dehydration, appeared to independently alter brain electrical activity. Moreover, the combination of moderate hyperthermia with 5% dehydration did not further increase those changes. That outcome was interpreted to mean that, when those states were superimposed, the resulting neurophysiological changes could almost exclusively be attributed to the thermal impact per se, rather than to their combined influences.

Hyperthermia and dehydration: their independent and combined influences on physiological function during rest and exercise.

PURPOSE: This experiment was designed to quantify the independent and combined influences of hyperthermia and dehydration on effector control during rest and exercise. METHODS: To achieve that, whole-body hydration of healthy adults (N = 8) was manipulated into each of three states (euhydrated, 3% and 5% dehydrated), and then clamped within each of two thermal states (normothermia [mean body temperature: 36.1 °C] and moderate hyperthermia [mean body temperature: 38.2 °C]). Those treatment combinations provided six levels of physiological strain, with resting physiological data collected at each level. The effects of isothermal, thermally unclamped and incremental exercise were then investigated in normothermic individuals during each level of hydration. RESULTS: At rest, dehydration alone reduced urine flows by 83% (3% dehydrated) and 93% (5% dehydrated), while the reduction accompanying euhydrated hyperthermia was 86%. The sensitivities of renal water conservation to 3% dehydration (-21% mOsm-1 kg H2O-1) and moderate hyperthermia (-40% °C-1) were independent and powerful. Evidence was found for different renal mechanisms governing water conservation between those treatments. Cutaneous vasomotor and central cardiac responses were unresponsive to dehydration, but highly sensitive to passive thermal stress. Dehydration did not impair either whole-body or regional sweating during rest or exercise, and not even during incremental cycling to volitional exhaustion. CONCLUSION: In all instances, the physiological impact of these thermal- and hydration-state stresses was independently expressed, with no evidence of interactive influences. Renal water-conservation was independently and powerfully modified, exposing possible between-treatment differences in sodium reabsorption.

Frequency-dependent and montage-based differences in phosphene perception thresholds via transcranial alternating current stimulation.

It is well known that applying transcranial alternating current stimulation (tACS) to the scalp can generate artefactual visual perceptions of flashing or shimmering light known as phosphenes. The thresholds for generating these phosphenes have been used by international standards bodies to provide conservative estimates of the field strength required to interfere with human neural functioning and set safety limits accordingly. However, the precise relationship between electric currents and phosphene perception thresholds remains uncertain. The present study used tACS to systematically investigate the effects of the location and the frequency of stimulation on phosphene perception thresholds. These thresholds were obtained from 24 participants using a within-subject design as a function of scalp stimulation sites (FPz-Cz versus Oz-Cz) and stimulation frequency (2-30 Hz in steps of 2 Hz). Phosphene perception thresholds were consistently lower for FPz-Cz stimulation, and regardless of tACS location were lowest for 16 Hz stimulation. Threshold variation between participants was very small, which is meaningful when setting standards based on phosphenes. Bioelectromagnetics. 2019;40:365-374. © 2019 Bioelectromagnetics Society.