Sensory Thresholds Research Articles

Time dependency and individual variation in human sensory irritation from acrolein – a controlled exposure study

ABSTRACT Acrolein is considered a risk factor for indoor air health problems due to its reactivity. An objective of the study was to investigate prevalence of sensory irritation in terms of time-dependent detection and perceived intensity of symptoms in human volunteers. Another objective was to investigate individual variation in sensory irritation. Participants (n=40) were exposed twice in an exposure chamber (15 min), once to heptane and once to acrolein and heptane. Symptoms and sensory irritation thresholds were rated continuously and 70% of the participants detected eye irritation from the acrolein exposure. A significant interaction between time and exposure (ƞp2=0.19) was identified, indicating time-dependent activation. This group also reported a higher level of stress and lower self-reported health (p<0.05). The results suggest that the eye is the primary system affected by exposure to acrolein, and that duration of exposure and perceived stress play important roles in symptom reactions due to acrolein exposure.

Auditory Noise Facilitates Lower Visual Reaction Times in Humans.

Noise is commonly seen as a disturbance but can influence any system it interacts with. This influence may not always be desirable, but sometimes it can improve the system's performance. For example, stochastic resonance is a phenomenon where adding the right amount of noise to a weak signal makes it easier to detect. This is known as sub-threshold detection. This sub-threshold detection's natural fingerprint is the fact that the threshold values follow an inverse U-shaped curve as the noise intensity increases. The minimum threshold value is the point of maximum sensitivity and represents the optimal point that divides the dynamics in two. Below that point, we can find the beneficial noise branch, where the noise can facilitate better detection. Above that point, the common detrimental noise concept can be found: adding noise hinders signal detection. The nervous system controls the movements and bodily functions in the human body. By reducing the sensory thresholds, we can improve the balance of these functions. Additionally, researchers have wondered if noise could be applied to different senses or motor mechanisms to enhance our abilities. In this work, noise is used to improve human reaction times. We tested the hypothesis that visual reaction times decrease significantly when the subject's perception is in the beneficial noise branch and closer to the optimal point than outside of this condition. Auditory noise was introduced in 101 human subjects using an interface capable of searching for the right amount of noise to place the subject in the beneficial noise branch close to the optimal point. When comparing the results, the reaction times decreased when the subjects were at the optimal point compared to when the subjects were outside of such conditions. These results reveal the possibility of using this approach to enhance human performance in tasks requiring faster reaction times, such as sports.

Central sensitization symptoms in vulvodynia: exploring the role of temperament, personality traits, childhood adverse events, defense mechanisms, and mental pain on quality of life.

Vulvodynia is a chronic pain syndrome characterized by persistent vulvar pain, occurring without clinically identifiable disorders. Central sensitization (CS) is suggested to play a role in the pathophysiology of vulvodynia, as for other nociplastic pain conditions. This study delves into the complex interplay between psychosocial factors and CS burden in women with vulvodynia, aiming to identify potential predictors (temperament, personality traits, childhood adverse events, defense mechanisms, and mental pain) and understand their impact on quality of life (QoL). A cohort-based cross-sectional web survey of 357 women with vulvodynia. Outcomes included 8 self-report measures to assess the Central Sensitization Inventory (CSI) and psychological variables, including sensory processing sensitivity, traumatic experiences, personality traits, defense mechanisms, and mental pain. Hierarchical multiple regression analyses were conducted in study 1, revealing that the following predicted higher CSI scores in women with vulvodynia: higher emotional overexcitability, decreased low sensory threshold, increased bodily threat experiences, elevated psychoticism, greater use of immature and neurotic defense mechanisms, and heightened mental pain. The final regression model identified the following as the strongest predictors of CS: low sensory threshold (β = 0.316), bodily threat experiences (β = 0.145), neurotic defenses (β = 0.210), and mental pain (β = 0.269). In study 2, the model presented interactions among these psychological factors in predicting CSI values explaining 48.9% of the variance in CS, 30.3% in psychological QoL, and 57.1% in physical QoL. This model opens discussion for tailored psychological interventions aimed to improve overall QoL in women with vulvodynia. Strengths of the study include innovative insights into the interplay between psychological variables and the construct of CS and quality of life. As a limitation, the research was conducted as a cross-sectional study with self-reported measures. The study calls for comprehensive assessments that consider physical and mental aspects, paving the way for holistic health care approaches in the management of vulvodynia.

Perceptibility and Pain Thresholds in Low- and High-Frequency Alternating Current Stimulation: Implications for tACS and tTIS

AbstractTranscranial electrical stimulation (tES) has emerged as a promising tool for neuromodulation, but its application is often limited by the discomfort associated with higher stimulation intensities. Newer variants like transcranial temporal interference stimulation (tTIS) utilize high-frequency alternating currents (≥ 500 Hz) to penetrate deeper brain regions while mitigating perceptual discomfort. This study sought to examine sensation and pain thresholds across various stimulation frequencies of alternating currents, aiming to explore the boundaries of comfortable intensities. Additionally, we sought to evaluate the efficacy of an anesthetizing topical cream in increasing participant comfort and potentially extending the range of tolerable stimulation levels. We recruited 37 participants and applied alternating current stimulation to the head at various frequencies (10 Hz, 20 Hz, 500 Hz, 1000 Hz, and 2000 Hz) to determine intensity-dependent perception and pain thresholds. Additionally, thresholds were determined under the influence of a topical anesthetic. Our findings confirm that as stimulation frequency increases, perceptibility decreases, with higher frequencies allowing a manyfold increase in stimulation intensity before becoming perceptible or causing pain. Additionally, the anesthetizing cream was efficacious in further reducing perceptibility and pain sensations across all frequencies. This study lays the groundwork for future research by establishing comfortable limits for stimulation intensities, particularly in the context of high-frequency stimulation. The reduced perceptibility of high-frequency stimulation, coupled with the effectiveness of anesthetizing creams, enables the administration of higher stimulation intensities for more potent neuromodulatory interventions without causing discomfort.

Effect of neoadjuvant chemoradiation on anorectal function assessed with anorectal manometry: A systematic review and meta-analysis.

Improvement in oncological survival for rectal cancer increases attention to anorectal dysfunction. Diagnostic questionnaires can evaluate quality of life but are subjective and dependent on patients' compliance. Anorectal manometry can objectively assess the continence mechanism and identify functional sphincter weakness and rectal compliance. Neoadjuvant chemoradiotherapy is presumed to affect anorectal function. We aim to assess anorectal function in rectal cancer patients who undergo total mesorectal excision, with or without neoadjuvant chemoradiation, using anorectal manometry measurements. MEDLINE, Embase, and Cochrane databases were searched for studies comparing perioperative anorectal manometry between neoadjuvant chemoradiation and upfront surgery for rectal cancers. Primary outcomes were resting pressure, squeeze pressure, sensory threshold volume and maximal tolerable volume. Eight studies were included in the systematic review, of which seven were included for metanalysis. 155 patients (45.3%) had neoadjuvant chemoradiation before definitive surgery, and 187 (54.6%) underwent upfront surgery. Most patients were male (238 vs. 118). The standardized mean difference of mean resting pressure, mean and maximum squeeze pressure, maximum resting pressure, sensory threshold volume, and maximal tolerable volume favored the upfront surgery group but without statistical significance. Currently available evidence on anorectal manometry protocols failed to show any statistically significant differences in functional outcomes between neoadjuvant chemoradiation and upfront surgery. Further large-scale prospective studies with standardized neoadjuvant chemoradiation and anorectal manometry protocols are needed to validate these findings.

Age related changes in skin sensitivity assessed with smartphone vibration testing

The capacity to perceive tactile input at the fingertips, referred to as tactile sensitivity, is known to diminish with age due to regressive changes to mechanoreceptor density and morphology. Sensitivity is measured as perceptual responses to stimuli of varying intensity. Contrary to traditional sensitivity monitoring instruments, smartphones are uniquely suited for remote assessment and have shown to deliver highly calibrated stimuli along a broad spectrum of intensity, which may improve test reliability. The aim of this study was to evaluate a vibration-emitting smartphone application, the Vibratus App, as a mode of estimating tactile sensory thresholds in the aging adult. The peripheral nerve function of 40 neurologically healthy volunteers (ages 18–71) was measured using monofilaments, a 128-Hz tuning fork, the Vibratus App, and nerve conduction studies (NCS). Between group differences were analyzed to determine each measurement’s sensitivity to age. Spearman correlation coefficients depicted the associative strength between hand-held measurements and sensory nerve action potential (SNAP) amplitude. Inter-rater reliability of traditional instruments and the software-operated smartphone were assessed by intraclass correlation coefficient (ICC2,k). Measurements taken with Vibratus App were significantly different between age groups (p < 0.001). The inter-rater reliability of monofilament, smartphone vibration, and tuning fork testing was moderate to good (ICC2,k = 0.65, 0.69, and 0.79, respectively). The findings of this study support further investigation of smartphones as sensitivity monitoring devices for at home monitoring of skin sensitivity.

Vitamin B5 is a context-dependent dietary regulator of nociception.

Chronic pain has an enormous impact on the quality of life of billions of patients, families, and caregivers worldwide. Current therapies do not adequately address pain for most patients. A basic understanding of the conserved genetic framework controlling pain may help us develop better, non-addictive pain therapies. Here, we identify new conserved and druggable analgesic targets using the tissue-specific functional genomic screening of candidate "pain" genes in fly. From these efforts, we describe 23 new pain genes for further consideration. This included Acsl, a fatty acid-metabolizing enzyme, and mammalian orthologs involved in arachidonic acid metabolism. The Acsl knockdown and mutant larvae showed delayed nocifensive responses to localized and global noxious heat. Mechanistically, the Acsl knockdown reduced dendritic branching of nociceptive neurons. Surprisingly, the pain phenotype in these animals could be rescued through dietary intervention with vitamin B5, highlighting the interplay between genetics, metabolism, and nutrient environment to establish sensory perception thresholds. Together, our functional genomic screening within the sensory nociceptor has identified new nociception genes that provide a better understanding of pain biology and can help guide the development of new painkillers.

Validity of Computer-Controlled Skin Sensation Threshold Measurements and Relationship to Balance in Older People.

Falls are an important health issue for older people, as they lead to increased morbidity and mortality and reduced physical function, activities of daily living, and quality of life. Skin sensation is an indicator of the ability to maintain balance, which is a factor in fall risk. We investigated the validity of a computer-controlled plantar-foot sensation-testing instrument (PFS tester) that measures skin sensation. We examined the within-subject reproducibility of skin sensation thresholds and their relationship to balance in older participants. Within-subject skin sensation threshold reproducibility was examined using intraclass correlation coefficients. The skin sensation thresholds showed moderate within-subject reproducibility. The associations between skin sensation thresholds and balance were examined using multiple regression analysis. We found a significant relationship between skin sensation thresholds and balance. The results indicate that the PFS tester is clinically applicable and a reliable indicator of balance ability.

Posterior insula repetitive transcranial magnetic stimulation for chronic pain in patients with Parkinson disease – pain type matters: A double-blinded randomized sham-controlled trial

ObjectivesAltered somatosensory processing in the posterior insula may play a role in chronic pain development and contribute to Parkinson disease (PD)-related pain. Posterior-superior insula (PSI) repetitive transcranial magnetic stimulation (rTMS) has been demonstrated to have analgesic effects among patients with some chronic pain conditions. This study aimed at assessing the efficacy of PSI-rTMS for treating PD-related pain. MethodsThis was a double-blinded, randomized, sham-controlled, parallel-arm trial (NCT03504748). People with PD (PwP)-related chronic pain underwent five daily PSI-rTMS sessions for a week, followed by once weekly maintenance stimulations for seven weeks. rTMS was delivered at 10 Hz and 80% of the resting motor threshold. The primary outcome was a ≥ 30% pain intensity reduction at 8 weeks compared to baseline. Functionality, mood, cognitive, motor status, and somatosensory thresholds were also assessed. ResultsTwenty-five patients were enrolled. Mean age was 55.2 ± 9.5 years-old, and 56% were female. Nociceptive pain accounted for 60%, and neuropathic and nociplastic for 20% each. No significant difference was found for 30% pain reduction response rates between active (42.7%) and sham groups (14.6%, p = 0.26). Secondary clinical outcomes and sensory thresholds also did not differ significantly. In a post hoc analysis, PwP with nociceptive pain sub-type experienced more pain relief after active (85.7%) compared to sham PSI-rTMS (25%, p = 0.032). ConclusionOur preliminary results suggest that different types of PD-related pain may respond differently to treatment, and therefore people with PD may benefit from having PD-related pain well characterized in research trials and in clinical practice.

Parameter optimization of non-invasive vagus nerve stimulation for second language learning in typically developing young adults

Although the ability to acquire a second language (L2) and attain fluency in that language is beneficial for a growing number of people, it is significantly more difficult to acquire such skills in adulthood. While traditional in-person and computer training programs can aid in this process, learning is often slow and retention is quite poor. A method for driving long-lasting neural plasticity during language learning would be valuable for those who need or want to achieve fluency in a second language later in life. However, little is known about the effect of neuromodulation methods on language learning. In the current study, we investigated the effect of non-invasive transcutaneous auricular vagus nerve stimulation (taVNS) on vocabulary word-learning in healthy young adults. Importantly, we approached this research question by investigating two key parameters of taVNS, stimulation frequency (Experiment 1) and current intensity (Experiment 2). Typically developing young adults completed a 1-h training session in which they learned 30 concrete, Palauan nouns while receiving real or sham stimulation to the left posterior tragus (Experiment 1) or stimulation at various intensities (Experiment 2). Participants completed a Palau-to-English translation test immediately after training and seven days later to quantify learning and retention. The results largely revealed that high frequency stimulation above sensory threshold improved retention of learned words. These results suggest that taVNS may improve retention of vocabulary words in a second language and that stimulation frequency may impact efficacy.

Assessing anorectal function in patients with recurrent ulcerative colitis

PurposeUlcerative colitis (UC) is an inflammatory bowel disease with an unclear etiology that can lead to irreversible changes in distal colonic function in chronic patients. This study investigated anorectal function in recurrent UC patients and identified influencing factors.MethodsThis prospective study enrolled 33 recurrent UC patients and 40 newly diagnosed patients from January 2019 to December 2022. Data collection included clinical records, scores, and anorectal function assessments. Regression analyses were used to identify factors impacting anorectal function.ResultsRecurrent UC patients had higher baseline CRP and fecal calprotectin levels, increased anxiety and depression, and more severe fecal incontinence. They also had lower BMIs, serum Hb and albumin (ALB) levels, and Inflammatory Bowel Disease Questionnaire scores than did initial-onset UC patients. Multivariate linear regression analysis revealed that long disease duration (coef. − 0.376, P < 0.001) and high fecal calprotectin level (coef. − 0.656, P < 0.001) independently influenced the initial sensation threshold in recurrent UC patients. Additionally, high fecal calprotectin (coef. − 0.073, P = 0.013) and high Zung Self-Rating Anxiety Scale score (coef. − 0.489, P = 0.001) were identified as two independent determinants of the defecation volume threshold. For the defecation urgency threshold, the independent factors included high disease duration (coef. − 0.358, P = 0.017) and high fecal calprotectin level (coef. − 0.499, P = 0.001). Similarly, the sole independent factor identified for the maximum capacity threshold was high fecal calprotectin (coef. − 0.691, P = 0.001).ConclusionRecurrent UC patients had increased rectal sensitivity and compromised anorectal function, which significantly impacted quality of life. Proactively managing the disease, reducing UC relapses, and addressing anxiety are effective measures for improving anorectal function in these patients.

Assessment of the Efficacy of Nalbuphine as an Adjuvant to Intrathecal Bupivacaine in Endoscopic Urological Surgeries for the Prolongation of Postoperative Analgesia.

Background In anaesthesiology, intrathecal drugs play pivotal roles in spinal anaesthesia. Despite their ability to induce a high sensory block, bupivacaine alone may not be adequate for postoperative analgesia. It often requires a substantial dose of postoperative rescue analgesia to manage pain effectively. Thus, we studied the efficacy of nalbuphine 1.5 mg injected intrathecally as an adjuvant in endoscopic urological surgery. Materials and methods Sixty patients undergoing endoscopic urological surgery were equally divided into two study groups: group B (injection 0.5% hyperbaric bupivacaine 15 mg (3 ml) plus sterile NS 0.15 ml) and group N (injection 0.5% hyperbaric bupivacaine 15 mg (3 ml)+nalbuphine 1.5 mg (0.15 ml)). The first appearance of the sensory and motor blockages and duration required to attain complete sensory and motor threshold was noted. All vitals were recorded. After surgery, it was recorded when the patient first needed rescue analgesia (injection paracetamol 1 gm IV). Any adverse effects were recorded and addressed. The statistical analysis was conducted using IBM SPSS Statistics for Windows, V. 22.0 (IBM Corp., Armonk, NY), with p<0.05 indicating significance in both groups' operations. Results Intrathecal nalbuphine as an adjuvant caused an earlier onset of sensory and motor inhibition, delayed two-segment regression, and prolonged postoperative anaesthesia. The control group experienced sensory block at 3.33±0.61 minutes, while the nalbuphine group had a mean onset of 2.66±0.92 minutes (p=0.001). The patient who received nalbuphine had a mean regression time of 119.60±14.549 minutes, whereas the bupivacaine group had a mean regression time of 88.43±17.196 minutes. Group N had a considerably longer duration of postoperative analgesia, lasting 264.97 minutes, compared to group B's 198.50 minutes (p<0.001). Intrathecal nalbuphine did not influence vital indicators such as heart rate, respiration rate, and oxygen saturation. Conclusion To conclude, endoscopic urological surgery patients who received a subarachnoid block with 1.5 mg (0.15 ml) of nalbuphine hydrochloride with 0.5% hyperbaric bupivacaine 15 mg (3 ml) had longer postoperative pain relief than those who received 3 ml of intrathecal bupivacaine (15 mg). Urinary retention and pruritus were absent. Intrathecal nalbuphine with hyperbaric 0.5% bupivacaine is deemed safe with minimal side effects in endoscopic urology surgery.

TORONTO: A trial-oriented multidimensional psychometric testing algorithm.

Bayesian adaptive methods for sensory threshold determination were conceived originally to track a single threshold. When applied to the testing of vision, they do not exploit the spatial patterns that underlie thresholds at different locations in the visual field. Exploiting these patterns has been recognized as key to further improving visual field test efficiency. We present a new approach (TORONTO) that outperforms other existing methods in terms of speed and accuracy. TORONTO generalizes the QUEST/ZEST algorithm to estimate simultaneously multiple thresholds. After each trial, without waiting for a fully determined threshold, the trial-oriented approach updates not only the location currently tested but also all other locations based on patterns in a reference data set. Since the availability of reference data can be limited, techniques are developed to overcome this limitation. TORONTO was evaluated using computer-simulated visual field tests: In the reliable condition (false positive [FP] = false negative [FN] = 3%), the median termination and root mean square error (RMSE) of TORONTO was 153 trials and 2.0dB, twice as fast with equal accuracy as ZEST. In the FP = FN = 15% condition, TORONTO terminated in 151 trials and was 2.2 times faster than ZEST with better RMSE (2.6 vs. 3.7dB). In the FP = FN = 30% condition, TORONTO achieved 4.2dB RMSE in 148 trials, while all other techniques had > 6.5dB RMSE and terminated much slower. In conclusion, TORONTO is a fast and accurate algorithm for determining multiple thresholds under a wide range of reliability and subject conditions.

Transcriptomic and Metabolomic Correlates of Increased Colonic Permeability in Postinfection Irritable Bowel Syndrome

Background and aimPost-infection irritable bowel syndrome (PI-IBS) is well-known epidemiologically; however, its physiological and molecular characteristics are not well studied. We aimed to determine the physiological phenotypes, colonic transcriptome, fecal microbiome, and metabolome in PI-IBS. MethodsFifty-one Rome III Campylobacter PI-IBS patients and 39 healthy volunteers (HV) were enrolled. Participants completed questionnaires, in vivo intestinal permeability, gastrointestinal transit, and rectal sensation. Fecal samples were collected for shotgun metagenomics, untargeted metabolomics, and sigmoid colonic biopsies for bulk RNAseq. Differential gene expression, differences in microbiota composition and metabolite abundance were determined. Gene and metabolite clusters were identified via weighted gene correlation network analysis and correlations with clinical and physiological parameters determined. ResultsPI-IBS (59% F, 46±2 yrs.) and HV (64% F, 42±2 yrs.) demographics were comparable. Mean IBS-symptom severity score was 227; 94% were non-constipation. 2-24h lactulose excretion was increased in PI-IBS, suggesting increased colonic permeability (4.4±0.5 mg vs. 2.6±0.3 mg, p=0.01). Colonic transit and sensory thresholds were similar between the two groups. Overall, expression of 2036 mucosal genes and 223 fecal metabolites were different, with changes more prominent in females. Fecal N-acetylputrescine was increased in PI-IBS and associated with colonic permeability, worse diarrhea, and negatively correlated with abundance of Collinsella aerofaciens. Histamine and N-acetyl histamine positively associated with 2-24 hr lactulose excretion. Eight weighted gene coexpression modules significantly correlated with phenotypes (sex, stool frequency, colonic permeability, transit). ConclusionsCampylobacter PI-IBS patients demonstrate higher colonic permeability which associated with changes in polyamine and histamine metabolites. Female patients demonstrated greater molecular changes.

Acute Effects of Skeletal Muscle Electrical Stimulation on Central and Lower Extremity Hemodynamics.

Belt electrode-skeletal muscle electrical stimulation (B-SES) is a treatment prescribed for individuals with difficulty performing exercise therapy that improves muscle strength, exercise tolerance, and glucose metabolism. However, the effects of B-SES on the hemodynamics of the central and lower extremity conduit arteries have not been studied. Therefore, this study compared the acute effects of B-SES on the central and lower extremity conduit arteries in healthy young males. This randomized crossover study included nine healthy young males (mean age: 21.0±1.1 years). Participants were assigned to the following experimental conditions, with a washout period of one week: condition 1 included 20 min of electrical stimulation of the lower extremity at the participant's sensation threshold intensity (Sham, n=9)and condition 2included 20 min of electrical stimulation of the lower extremity at the maximum intensity the participant can tolerate (B-SES, n=9). The heart rate (HR), stroke volume (SV), cardiac output (CO), mean arterial pressure (MAP), and total peripheral vascular resistance (TPR) were measured as central hemodynamics. The hemodynamics of the lower extremity conduit arteries were measured and calculated for the shallow femoral artery (SFA), including vessel diameter, mean blood flow velocity (MBFV), shear rate (SR), and mean blood flow (MBF) rate. These indices were measured before stimulation (Pre), 10 min after the start of stimulation (Stimulating), and immediately after the end of stimulation (Post). These indices were compared using a repeated two-way analysis of variance. In B-SES, HR (Pre: 63.2±8.6; Stimulating: 73.7±6.9; Post: 70.0±4.2 bpm, p<0.01), CO (Pre: 5.1±1.0; Stimulating: 6.5±1.5, p<0.01; Post: 6.3±1.2 L/min, p=0.02), and MAP (Pre: 104.0±11.5; Stimulating: 116.4±10.8, p<0.01; Post: 109.6±9.7 mmHg, p=0.02) increased significantly. In addition, B-SES significantly increased MBFV (Pre: 19.2±4.0; Stimulating: 50.5±14.9; Post: 30.1±4.0 cm/s, p<0.01), SR (Pre: 118.9±28.8; Stimulating: 302.7±91. 2, p<0.01; Post: 182.1±70.1/s, p=0.02), and MBF (Pre: 382.0±61.5; Stimulating: 1009.6±321.4; Post: 626.8±176.6 mL/min, p<0.01). However, there were no significant changes in SV and TPR. The findings of this study indicatethat B-SES in healthy young males increases CO without increasing SV or TPR and improves the MBFV and SR in the SFA.

Mechanisms underlying the formation of main volatile odor sulfur compounds in foods during thermal processing.

Volatile sulfur compounds (VSCs) significantly influence food flavor and garner considerable attention in flavor research due to their low sensory thresholds, diverse odor attributes, and high reactivity. Extensive research studies have explored VSC formation through thermal processes such as the Maillard reaction, thermal pyrolysis, oxidation, and enzymatic reactions. However, understanding of the specific reaction mechanisms and processes remains limited. This is due to the dispersed nature of existing studies, the undefined intermediates involved, and the complexity of the matrices and processing conditions. Given these limitations, the authors have shifted their focus from foods to sulfides. The structure, source, and chemical characteristics of common precursors (sulfur-containing amino acids and derivatives, thiamine, thioglucoside, and lentinic acid) and their corresponding reactive intermediates (hydrogen sulfide, thiol, alkyl sulfide, alkyl sulfenic acid, and thial) are provided, and the degradation mechanisms, reaction rules, and matrix conditions are summarized based on their chemical characteristics. Additionally, the VSC formation processes in several typical foods during processing are elucidated, adhering to these identified rules. This article provides a comprehensive overview of VSCs, from precursors and intermediates to end products, and is crucial for understanding the mechanisms behind VSC formation and managing the flavor qualities of processed foods.

Changes in blink reflex after simultaneous supraorbital and mental nerve stimulations in healthy subjects.

In this study, we investigated the blink reflex (BR) after simultaneous and asynchronous stimulation of two trigeminal nerve branches. The objective was to characterize the physiology of trigeminal and facial circuits. We performed three sets of experiments: recording BR response i. after supraorbital nerve stimulation (SON), after mental nerve stimulation (MN), and after simultaneous SON and MN stimulation (SON+MN) in 18 healthy individuals; ii. after MN (at an intensity eliciting BR response) preceding SON at various interstimulus intervals (ISIs) in seven healthy subjects; iii after MN (at sensory threshold) preceding SON at various ISIs. We compared the magnitudes of early and late responses. The R1 amplitude after simultaneous SON+MN stimulation was greater than responses after single stimulation of the same branches. After simultaneous stimulations, the R2 and R2c areas under the curve (AUC) were smaller than the arithmetic sums of R2 and R2c AUC obtained after single stimulations. The second experiment provided a recovery excitability curve. In the third step, we obtained facilitation of R1 and inhibition of late responses. The SON+MN stimulation caused an increased R1 circuit excitability compared to the arithmetic sum of the single stimulations; however, magnitudes of late responses did not potentiate. Thus, we have provided evidence for R1 circuit enhancement by simultaneous stimulation in humans, whereas modulation of late responses exhibited a recovery curve similar to that shown for paired SON stimulation.

Ink-based textile electrodes for wearable functional electrical stimulation: A proof-of-concept study to evaluate comfort and efficacy.

Functional Electrical Stimulation (FES) represents a promising technique for promoting functional recovery in individuals with neuromuscular diseases. Traditionally, current pulses are delivered through self-adhesive hydrogel Ag/AgCl electrodes, which allow a good contact with the skin, are easy-to-use and have a moderate cost. However, skin adherence decreases after a few uses and skin irritations can originate. Recently, textile electrodes have become an attractive alternative as they assure increased durability, easy integration into clothes and can be conveniently cleaned, improving the wearability of FES. However, as various manufacture processes were attempted, their clear validation is lacking. This proof-of-concept study proposes a novel set of ink-based printed textile electrodes and compares them to adhesive hydrogel electrodes in terms of impedance, stimulation performance and perceived comfort. The skin-electrode impedance was evaluated for both types of electrodes under different conditions. These electrodes were then used to deliver FES to the Rectus Femoris of 14 healthy subjects to induce its contraction in both isometric and dynamic conditions. This allowed to compare the two types of electrodes in terms of sensory, motor, maximum and pain thresholds, FES-induced range of motion during dynamic tests, FES-induced torque during isometric tests and perceived stimulation comfort. No statistically significant differences were found both in terms of stimulation performance (Wilcoxon test) and comfort (Generalized Linear Mixed Model). The results showed that the proposed ink-based printed textile electrodes can be effectively used as alternative to hydrogel ones. Further experiments are needed to evaluate their durability and their response to sterilizability and stretching tests.

Lack of association of impaired upper airway sensation with the presence or absence of obstructive sleep apnoea or chronic rhinosinusitis in World Trade Center responders

ObjectiveExamine sensory function of the upper airway in four groups of subjects recruited from the World Trade Centre General Responder Cohort (WTCGRC), with/without obstructive sleep apnoea (OSA), and with/without chronic...

Effect of repeated topical capsaicin gel administration on oral thermal quantitative sensory testing: A two-arm longitudinal study.

Few studies used thermal quantitative sensory testing to assess the effects of repeated capsaicin gel administration in the oral cavity. This study aimed to investigate thermal sensory and pain thresholds before and after repeated capsaicin gel administration. Ten healthy females (22 ± 2 years) applied a capsaicin gel on the gingival mucosa twice daily for 14 days, and heat pain threshold, warm detection threshold, cold pain threshold, and cold detection threshold were assessed on the oral mucosa. Measurements were performed before and after the 14 days and were compared to a control sample (n = 10, all females, 23 ± 3 years). Capsaicin increased heat pain threshold in the anterior maxilla by 2.9°C (95% CI: 1.6-4.2) (p < 0.001) and in the anterior mandible by 2.2°C (95% CI: 1.0-3.4) (p = 0.001), similar to warm detection threshold that increased by Δ1.1°C (95% CI: 0.3-1.9) (p = 0.009). No significant changes were found in the controls. These findings encourage the use of thermal quantitative sensory testing in the oral cavity to assess thermal sensation, which might be useful for assessing the effects of therapies aimed at reducing pain.