Mapping Sensory Spots for Moderate Temperatures on the Back of Hand

Habituation of the cold shock response: A systematic review and meta-analysis

Cold water immersion (CWI) evokes the life-threatening reflex cold shock response (CSR), inducing hyperventilation, increasing cardiac arrhythmias, and increasing drowning risk by impairing safety behaviour. Repeated CWI induces CSR habituation (i.e., diminishing response with same stimulus magnitude) after ∼4 immersions, with variation between studies. We quantified the magnitude and coefficient of variation (CoV) in the CSR in a systematic review and meta-analysis with search terms entered to Medline, SportDiscus, PsychINFO, Pubmed, and Cochrane Central Register. Random effects meta-analyses, including effect sizes (Cohen's d) from 17 eligible groups (k), were conducted for heart rate (HR, n = 145, k = 17), respiratory frequency (fR, n = 73, k = 12), minute ventilation (Ve, n = 106, k = 10) and tidal volume (Vt, n = 46, k=6). All CSR variables habituated (p < 0.001) with large or moderate pooled effect sizes: ΔHR -14 (10) bt. min-1 (d: -1.19); ΔfR -8 (7) br. min-1 (d: -0.78); ΔVe, -21.3 (9.8) L. min-1 (d: -1.64); ΔVt -0.4 (0.3) L -1. Variation was greatest in Ve (control vs comparator immersion: 32.5&24.7%) compared to Vt (11.8&12.1%). Repeated CWI induces CSR habituation potentially reducing drowning risk. We consider the neurophysiological and behavioural consequences.

Revisiting a classical theory of sensory specificity: assessing consistency and stability of thermosensitive spots

Thermal sensitivity is not uniform across the skin, and is particularly high in small (∼1 mm2) regions termed "thermosensitive spots." These spots are thought to reflect the anatomical location of specialized thermosensitive nerve endings from single primary afferents. Thermosensitive spots provide foundational support for "labeled line" or specificity theory of sensory perception, which states that different sensory qualities are transmitted by separate and specific neural pathways. This theory predicts a highly stable relation between repetitions of a thermal stimulus and the resulting sensory quality, yet these predictions have rarely been tested systematically. Here, we present the qualitative, spatial, and repeatability properties of 334 thermosensitive spots on the dorsal forearm sampled across four separate sessions. In line with previous literature, we found that spots associated with cold sensations (112 cold spots, 34%) were more frequent than spots associated with warm sensations (41 warm spots, 12%). Still more frequent (165 spots, 49%) were spots that elicited inconsistent sensations when repeatedly stimulated by the same temperature. Remarkably, only 13 spots (4%) conserved their position between sessions. Overall, we show unexpected inconsistency of both the perceptual responses elicited by spot stimulation and of spot locations across time. These observations suggest reappraisals of the traditional view that thermosensitive spots reflect the location of individual thermosensitive, unimodal primary afferents serving as specific labeled lines for corresponding sensory qualities.NEW & NOTEWORTHY Thermosensitive spots are clustered rather than randomly distributed and have the highest density near the wrist. Surprisingly, we found that thermosensitive spots elicit inconsistent sensory qualities and are unstable over time. Our results question the widely believed notion that thermosensitive spots reflect the location of individual thermoreceptive, unimodal primary afferents that serve as labelled lines for corresponding sensory qualities.

Telangiectasia diameter in response to thermal stimulus: experimental data and possible clinical applications

BACKGROUND

Telangiectasias are dilated blood vessels on the skin that develop progressively because of several diseases, including chronic venous disease. The skin blood flow has differences compared to the rest of the circulatory system. These vessels have a permanent vasoconstrictor tone that can respond to vasoconstriction/vasodilation stimulative substances and higher or lower temperatures. The aim of this study was to investigate any possible telangiectasias vasoconstriction or vasodilation in response to temperature changes.

METHODS

This study is a clinical trial with 26 outpatients of vascular surgery with telangiectasias in the lower limbs. We used direct skin digital microscopy to obtain telangiectasias images at room temperature and after the thermal stimulus with cold pads. These photographs were processed using AmScopeAmLite (United Scope LLC Euromex Optics Group b.v., Los Angeles, CA, USA) and the capillary diameter and area were measured in Adobe Illustrator (Adobe Inc., Mountain View, CA, USA). The data collected was analyzed in SPSS Statistics (SPSS Inc., Chicago, IL, USA) with a paired t-test for the telangiectasias area and a Wilcoxon matched-pairs signed-rank test for the telangiectasias diameter.

RESULTS

In comparison to telangiectasias measures at room temperature, we found a statistically significant decrease in the diameter (median of -0.04 mm; interquartile range: -0.10 mm to -0.01 mm; P<0.001) and area (mean of -26.54 mm²; 95% Confidence interval (-36.31, -16.76) mm²; P<0.001 in response to the cold stimulus.

CONCLUSIONS

Telangiectasias respond to cold patch application with a significantly statistical microscale quantifiable vasoconstriction. This intervention has the potential to improve the current state of telangiectasias sclerotherapy due to its mechanism helping to stabilize the applied foam. We speculate that topic cold used as a neoadjuvant treatment could improve the efficiency, stability, and other outcomes of sclerotherapy. Also, complementary use of topical cold stimulus application may be of interest in the therapeutic management of telangiectasias.

Penetrating effect of high-intensity infrared laser pulses through body tissue

Researchers have utilized infrared (IR) lasers as energy sources in laser therapy for curing skin diseases and skin injuries with remarkable effects. Preliminary experiments have also shown that high-intensity IR laser pulses could penetrate thick body tissues, resulting in remarkable effects for recovery from injuries in deep muscles and cartilage tissues. However, for deep-level IR laser therapy, it is unclear how much of the laser power density penetrates the body tissues at certain depths and which of the three major effects of laser irradiation, namely, laser-induced photo-chemical effect, photo-thermal effect and mechanical dragging effect, play a key role in the curing process. Thus, in this study, we developed micro-sized thin-film thermocouple (TFTC) arrays on freestanding Si₃N₄ thin-film windows as sensors for laser power density and local temperature. These devices showed excellent linear responses in output voltage to laser power density with wavelengths in the range of 325-1064 nm, and also indicated the local temperature at the laser spot. We systematically measured the penetrating effect and thermal effect through thick porcine tissues for high-intensity IR pulses with a laser system used in clinical treatment and subtracted the attenuation parameters for the porcine skin, fat and muscle tissue from the experimental data. The results offered reliable quantitative references for safe irradiation doses of high-intensity IR laser pulses in practical laser therapy.