A Virtual Reality Application of the Rubber Hand Illusion Induced by Ultrasonic Mid-air Haptic Stimulation

Ultrasonic mid-air haptic technologies, which provide haptic feedback through airwaves produced using ultrasound, could be employed to investigate the sense of body ownership and immersion in virtual reality (VR) by inducing the virtual hand illusion (VHI). Ultrasonic mid-air haptic perception has solely been investigated for glabrous (hairless) skin, which has higher tactile sensitivity than hairy skin. In contrast, the VHI paradigm typically targets hairy skin without comparisons to glabrous skin. The aim of this article was to investigate illusory body ownership, the applicability of ultrasonic mid-air haptics, and perceived immersion in VR using the VHI. Fifty participants viewed a virtual hand being stroked by a feather synchronously and asynchronously with the ultrasonic stimulation applied to the glabrous skin on the palmar surface and the hairy skin on the dorsal surface of their hands. Questionnaire responses revealed that synchronous stimulation induced a stronger VHI than asynchronous stimulation. In synchronous conditions, the VHI was stronger for palmar stimulation than dorsal stimulation. The ultrasonic stimulation was also perceived as more intense on the palmar surface compared to the dorsal surface. Perceived immersion was not related to illusory body ownership per se but was enhanced by the provision of synchronous stimulation.

MORPHOLOGY AND HISTOLOGY OF THE EURASIAN LYNX (Lynx lynx) PLANUM NASALE

This study reveals the macroscopic and microscopic structures of the Eurasian lynx planum nasale using materials from three dead females obtained from the Sivas Forestry Branch of Agriculture and Forestry Ministry of the Republic of Turkey. To accomplish the purpose, planum nasale was investigated using macroscopic, histological, and scanning electron microscopy (SEM) techniques. The microscopic examination showed that the planum nasale consists of hairless, moist, glabrous skin and resembles a ship anchor with arm, palm, stock, and sickle parts. The planum nasale’s surface is formed by epidermal plates or epidermal ridges, which were separated from each other by primary and secondary fissures showed in SEM and macroscopic figures. Based on the microscopic examination, the Mercel’s cells and nerve ends are located in the basal sheet of the planum nasale’s epidermal layers. In addition, the pores situated on the surface of the epidermal ridges and the dense connective bundles were settled in the dermal layers, based on the SEM examination.Key words: Eurasian lynx (Lynx rufus); morphology; nasal plane; planum nasaleMORFOLOGIJA IN HISTOLOGIJA SMRČKA EVRAZIJSKEGA RISA (Lynx lynx)Izvleček: V študiji so opisane makroskopske in mikroskopske strukture smrčka evrazijskega risa, ki je bila opravljena s proučevanjem tkiv treh mrtvih samic, ki so jih pridobili s pomočjo gozdarske podružnice Sivas Ministrstva za kmetijstvo in gozdarstvo Republike Turčije. Strukturo smrčka so raziskovali z uporabo makroskopskih, histoloških metod ter uporabe vrstičnega elektronskega mikroskopa (SEM). Mikroskopska preiskava je pokazala, da smrček sestavlja brezdlaka, vlažna, gola koža, ki po obliki spominja na ladijsko sidro. Površinski del smrčka tvorijo epidermalne plošče ali grebeni, ki jih ločujejo primarne in sekundarne razpoke, vidne na makroskopskih slikah in s pomočjo vrstične mikroskopije. Na histoloških preparatih so bile v bazalni plasti smrčka epidermisa opazne Merkelove celice in živčni končiči. S pomočjo metode SEM so v plasti epidermisa pokazali pore, ki se nahajajo na površini epidermalnih grebenov in snope togega fibrilarnega veziva, ki segajo v plast dermisa.Ključne besede: Evrazijski ris (Lynx rufus); morfologija; nosna ravnina; smrček

Efficacy and Function of Feathers, Hair, and Glabrous Skin in the Thermoregulation Strategies of Domestic Animals

The objective of this review is to describe and analyze the effect of feathers, hair, and glabrous (hairless) skin on the thermoregulation of domestic and endotherm animals, especially concerning the uses and scope of infrared thermography (IRT), scientific findings on heat and cold stress, and differences among species of domestic animals. Clinical medicine considers thermoregulation a mechanism that allows animals to adapt to varying thermal environmental conditions, a process in which the presence of feathers, hair, or glabrous skin influences heat loss or heat retention, respectively, under hot and cold environmental conditions. Evaluating body temperature provides vital information on an individual’s physiological state and health status since variations in euthermia maintenance in vertebrates reflect a significant cellular metabolism deviation that needs to be assessed and quantified. IRT is a non-invasive tool for evaluating thermal responses under thermal stress conditions in animals, where the presence or absence of feathers, hair, and glabrous skin can affect readings and the differences detected. Therefore, anatomical regions, the characteristics of feathers, hair, glabrous skin such as structure, length, color, and extension, and strategies for dissipating or retaining heat together constitute a broad area of opportunity for future research into the phenomena of dermal thermoregulation in domestic species.

Treating complex palmar–plantar wounds using a bilaminar ‘trapdoor’ technique: a case series

Objective: Due to the similarities of glabrous skin, the plantar region is an excellent donor area for covering complex palmar–plantar wounds. However, taking grafts from the plantar area often results in significant morbidity at the donor site or non-integration of the graft due to the greater thickness of the plantar corneal layer. Method: This is a prospective case series including patients with burns or wounds who have been treated with a dermal graft using the bilaminar ‘trapdoor’ technique. This procedure is used to remove a thin graft from the deep plantar dermis after the partial elevation of the first layer including the entire epidermis and superficial part of the dermis. Results: At the donor area in the four patients in this case series, we observed healing at around 10 days, and absence of hypertrophic scar in all patients. There was complete re-epithelialisation between two and three weeks from the periphery to the centre of the deep dermal graft, and from the glandular epithelium transferred with the graft. During the follow-up, patients presented aesthetic and functional features of glabrous and amelanotic skin, with similar resistance to those of the adjacent areas of the wound in the palmar–plantar region. Conclusion: This technique has some advantages, such as less surgical time, minimal morbidity in the plantar donor area, easy integration of the grafts, and maintenance of the functional and aesthetic properties of glabrous skin both in the plantar donor area and in the palmar–plantar recipient region. Declaration of interest: The authors have no conflicts of interest to declare.

Differential responsiveness of glabrous and non-glabrous skin to local transmural pressure elevations; the impact of 5 weeks of iterative local pressure loading

We examined the in vivo pressure-flow relationship in human cutaneous vessels during acute and repeated elevations of local transmural pressure. In 10 healthy men, red blood cell flux was monitored simultaneously on the non-glabrous skin of the forearm and the glabrous skin of a finger during a vascular pressure provocation, wherein the blood vessels of an arm were exposed to a wide range of stepwise increasing distending pressures. Forearm skin blood flux was relatively stable at slight and moderate elevations of distending pressure, whereas it increased ~3-4-fold at the highest levels (P = 0.004). Finger blood flux on the contrary, dropped promptly and consistently throughout the provocation (P < 0.001). Eight of the subjects repeated the provocation trial after a 5-week pressure-training regimen, during which the vasculature in one arm was exposed intermittently (40 min, 3 times･week-1) to increased transmural pressure (from +65 mmHg week-1 to +105 mmHg week-5). The training regimen diminished the pressure-induced increase in forearm blood flux by ~34% (P = 0.02), whereas it inhibited the reduction in finger blood flux (P < 0.001) in response to slight and moderate distending pressure elevations. The present findings demonstrate that, during local pressure perturbations, the cutaneous autoregulatory function is accentuated in glabrous compared to in the non-glabrous skin regions. Prolonged intermittent regional exposures to augmented intravascular pressure blunt the responsiveness of the glabrous skin, but enhance arteriolar pressure resistance in the non-glabrous skin.

Tactile sensitivity in the rat: a correlation between receptor structure and function

Single cutaneous fibers were recorded in the median nerve of the deeply anesthetized rat and the receptor morphology in the forelimb glabrous skin was analyzed to establish a probable correlation between receptor anatomy and physiology. Receptor complexes in the glabrous skin of the rat forelimb were stained immunologically with antibodies NF-200 and PGP-9.5, confirming the presence of Meissner corpuscles and Merkel complexes within the dermal papilla similar to other mammals including primates. Both the Meissner corpuscles and Merkel cell complexes were sparse and located in the pyramidal-shaped palmer pads and the apex of the digit extremities. They were almost totally absent elsewhere in the glabrous skin. No Ruffini receptors or Pacinian corpuscles were found in our samples. A total of 92 cutaneous fibers were retained long enough for analysis. Thirty-five (38%) were characterized as rapidly adapting fibers (RA) and 57 (62%) were slowly adapting afferents (SA). Despite the very limited number of receptors at the tip of the digit, RA receptors outnumbered SA fibers 3.2/1.0. In contrast, SA fibers on the thenar pad outnumbered RA receptors by a ratio of 3–1. Despite the very limited number of low threshold mechanoreceptors in the glabrous skin of the rat forelimb, the prevalence of SA afferents in the palm and more frequent occurrence of RA afferents in the digit extremity suggest differences in functionality both for locomotion and object manipulation.

Mechanical Impedance of Rat Glabrous Skin and Its Relation with Skin Morphometry

The mechanical impedance of intact and epidermis-peeled rat glabrous skin was studied at two sites (digit and sole) and at two frequencies (40 Hz and 250 Hz). The thicknesses of skin layers at the corresponding regions were measured histologically from intact- and peeled-skin samples in every subject. Compared to intact sole skin, digital rat skin has thicker layers and higher mechanical resistance, and it is less stiff. The resistance of the skin significantly decreased after epidermal peeling at both the digit and the sole. Furthermore, peeling caused the reactance to become positive due to inertial effects. As the frequency was increased from 40 to 250 Hz, the resistance and stiffness also increased for the intact skin, while the peeled skin showed less frictional (i.e. resistance) but more inertial (i.e. positive reactance) effects. We estimated the mechanical properties of epidermis and dermis with lumped-element models developed for both intact and peeled conditions. The models predicted that dermis has higher mass, lower stiffness, and lower resistance compared to epidermis, similar to the experimental impedance results obtained in the peeled condition which consisted mostly of dermis. The overall impedance was simulated more successfully at 40 Hz. When both frequencies are considered, the models produced consistent results for resistance in both conditions. The results imply that most of the model parameters should be frequency-dependent, and suggest that mechanical properties of epidermis can be related to its thickness. These findings may help in designing artificial skin for neuroprosthetic limbs.

Low mechano-afferent fibers reduce thermal pain but not pain intensity in CRPS

Background Human hairy (not glabrous skin) is equipped with a subgroup of C-fibers, the C-tactile (CT) fibers. Those do not mediate pain but affective aspects of touch. CT-fiber-activation reduces experimental pain if they are intact. In this pilot study we investigated pain modulating capacities of CT-afferents in CRPS. Methods 10 CRPS-patients (mean age 33 years, SEM 3.3) and 11 healthy controls (mean age 43.2 years, SEM 3.9) participated. CT-targeted-touch (brush stroking, velocity: 3 cm/s) was applied on hairy and glabrous skin on the affected and contralateral limb. Patients rated pleasantness of CT-targeted-touch (anchors: 1 “not pleasant”—4 “very pleasant”) twice daily on 10 days. Pain intensity (NRS: 0 “no pain” – 10 “worst pain imaginable”) was assessed before, 0, 30, 60 and 120 min after each CT-stimulation. To assess sensory changes, quantitative-sensory-testing was performed at the beginning and the end of the trial period. Results CT-targeted-touch was felt more pleasant on the healthy compared to the affected limb on hairy (p < 0.001) and glabrous skin (p 0.002), independent of allodynia. In contrast to healthy controls patients felt no difference between stimulating glabrous and hairy skin on the affected limb. Thermal pain thresholds increased after CT-stimulation on the affected limb (cold-pain-threshold: p 0.016; heat-pain-threshold: p 0.033). Conclusions CT-stimulation normalizes thermal pain thresholds but has no effect on the overall pain in CRPS. Therefore, pain modulating properties of CT-fibers might be too weak to alter chronic pain in CRPS. Moreover, CT-fibers appear to lose their ability to mediate pleasant aspects of touch in CRPS.