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1. The inner core enables transient touch detection in the Pacinian corpuscle

   https://doi.org/10.1126/sciadv.adt4837  

   Ziolkowski, Luke H; Nikolaev, Yury A; Chikamoto, Akitoshi; Oda, Mai; Feketa, Viktor V; Monedero-Alonso, David; Ardasheva, Serafima A; Bae, Samuel S; Xu, C Shan; Pang, Song; et al (February 2025, Science Advances)

   NA (Ed.)

   Pacinian corpuscles detect transient touch and vibration in vertebrates. Corpuscles are composed of a mechanoreceptor afferent surrounded by lamellar Schwann cells (LSCs), enclosed by a multilayered outer core. The spatial arrangement of these components and their contribution to sensory tuning are unclear. We report the three-dimensional architecture of the Pacinian corpuscle and reveal the role of its cellular components in touch detection. In the prevailing model, the outer core acts as a mechanical filter that limits static and low-frequency stimuli from reaching the afferent terminal—the presumed sole site of touch detection. We show that the outer core is dispensable for the sensory tuning to transient touch and vibration; instead, these properties arise from the inner core. By acting as additional touch sensors, LSCs potentiate mechanosensitivity of the terminal, which detects touch via fast inactivating ion channels. Thus, functional tuning of the Pacinian corpuscle is enabled by an interplay between mechanosensitive LSCs and the afferent terminal in the inner core. 

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2. 3D architecture and a bicellular mechanism of touch detection in mechanosensory corpuscle

   https://doi.org/10.1126/sciadv.adi4147  

   Nikolaev, Yury A; Ziolkowski, Luke H; Pang, Song; Li, Wei-Ping; Feketa, Viktor V; Xu, C Shan; Gracheva, Elena O; Bagriantsev, Sviatoslav N (September 2023, Science Advances)

   Mechanosensory corpuscles detect transient touch and vibration in the skin of vertebrates, enabling precise sensation of the physical environment. The corpuscle contains a mechanoreceptor afferent surrounded by lamellar cells (LCs), but corpuscular ultrastructure and the role of LCs in touch detection are unknown. We report the three-dimensional architecture of the avian Meissner (Grandry) corpuscle acquired using enhanced focused ion beam scanning electron microscopy and machine learning-based segmentation. The corpuscle comprises a stack of LCs interdigitated with terminal endings from two afferents. Simultaneous electrophysiological recordings from both cell types revealed that mechanosensitive LCs use calcium influx to trigger action potentials in the afferent and thus serve as physiological touch sensors in the skin. The elaborate architecture and bicellular sensory mechanism in the corpuscles, which comprises the afferents and LCs, create the capacity for nuanced encoding of the submodalities of touch. 

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3. Lamellar cells in Pacinian and Meissner corpuscles are touch sensors

   https://doi.org/10.1126/sciadv.abe6393  

   Nikolaev, Yury A.; Feketa, Viktor V.; Anderson, Evan O.; Schneider, Eve R.; Gracheva, Elena O.; Bagriantsev, Sviatoslav N. (December 2020, Science Advances)

   null (Ed.)

   The skin covering the human palm and other specialized tactile organs contains a high density of mechanosensory corpuscles tuned to detect transient pressure and vibration. These corpuscles comprise a sensory afferent neuron surrounded by lamellar cells. The neuronal afferent is thought to be the mechanical sensor, whereas the function of lamellar cells is unknown. We show that lamellar cells within Meissner and Pacinian corpuscles detect tactile stimuli. We develop a preparation of bill skin from tactile-specialist ducks that permits electrophysiological recordings from lamellar cells and demonstrate that they contain mechanically gated ion channels. We show that lamellar cells from Meissner corpuscles generate mechanically evoked action potentials using R-type voltage-gated calcium channels. These findings provide the first evidence for R-type channel-dependent action potentials in non-neuronal cells and demonstrate that lamellar cells actively detect touch. We propose that Meissner and Pacinian corpuscles use neuronal and non-neuronal mechanoreception to detect mechanical signals. 

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4. Investigating mechanoreceptor variability and morphometric proxies in Rhesus Macaques: Implications for primate precision touch studies

   https://doi.org/10.1002/ar.25587  

   Covarrubias, Brandon_Vera; Kamminga, Jordan_M; Muchlinski, M_N; Munds, R_A; Villero_Núñez, V.; Bauman_Surratt, S.; Cayo_Biobank_Research_Unit; Martinez, M_I; Montague, M_J; Higham, J_P; et al (October 2024, The Anatomical Record)

   Abstract The origin of primates has long been associated with an increased emphasis on manual grasping and touch. Precision touch, facilitated by specialized mechanoreceptors in glabrous skin, provides critical sensory feedback for grasping‐related tasks and perception of ecologically‐relevant stimuli. Despite its importance, studies of mechanoreceptors in primate hands are limited, in part due to challenges of sample availability and histological methods. Dermatoglyphs have been proposed as alternative proxies of mechanoreceptor density. We investigated the relationships between mechanoreceptors (Meissner and Pacinian corpuscles), dermatoglyphs, and demography in the apical finger pads of 15 juvenile to adult rhesus macaques (Macaca mulatta) from a free‐ranging population at Cayo Santiago Primate Field Station (Puerto Rico). Our results indicate substantial interindividual variation in mechanoreceptor density (Meissner corpuscles: 11.9–43.3 corpuscles/mm²; Pacinian corpuscles: 0–4.5 corpuscles/mm²). While sex and digit were generally not associated with variation, there was strong evidence of a developmental effect. Specifically, apical pad length, Meissner corpuscle size, and Pacinian corpuscle depth increased while mechanoreceptor densities decreased throughout juvenescence, suggesting that primate mechanoreceptors change as fingers grow during adolescence and then stabilize at physical maturity. We also found Meissner corpuscle density was significantly associated with dermatoglyph ridge width and spacing, such that density predicted by a dermatoglyph model was strongly correlated with observed values. Dermatoglyphs thus offer a useful proxy of relative Meissner corpuscle density in primates, which opens exciting avenues of noninvasive research. Finally, our results underscore the importance of considering demographic factors and methodology in comparative studies of primate touch. 

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5. An individual's skin stiffness predicts their tactile discrimination of compliance

   https://doi.org/10.1113/JP285271  

   Li, Bingxu; Gerling, Gregory J. (November 2023, The Journal of Physiology)

   AbstractIndividual differences in tactile acuity have been correlated with age, gender and finger size, whereas the role of the skin's stiffness has been underexplored. Using an approach to image the 3‐D deformation of the skin surface during contact with transparent elastic objects, we evaluate a cohort of 40 young participants, who present a diverse range of finger size, skin stiffness and fingerprint ridge breadth. The results indicate that skin stiffness generally correlates with finger size, although individuals with relatively softer skin can better discriminate compliant objects. Analysis of contact at the skin surface reveals that softer skin generates more prominent patterns of deformation, in particular greater rates of change in contact area, which correlate with higher rates of perceptual discrimination of compliance, regardless of finger size. Moreover, upon applying hyaluronic acid to soften individuals’ skin, we observe immediate, marked and systematic changes in skin deformation and consequent improvements in perceptual acuity in differentiating compliance. Together, the combination of 3‐D imaging of the skin surface, biomechanics measurements, multivariate regression and clustering, and psychophysical experiments show that subtle distinctions in skin stiffness modulate the mechanical signalling of touch and shape individual differences in perceptual acuity.Key pointsAlthough declines in tactile acuity with ageing are a function of multiple factors, for younger people, the current working hypothesis has been that smaller fingers are better at informing perceptual discrimination because of a higher density of neural afferents.To decouple relative impacts on tactile acuity of skin properties of finger size, skin stiffness, and fingerprint ridge breadth, we combined 3‐D imaging of skin surface deformation, biomechanical measurements, multivariate regression and clustering, and psychophysics.The results indicate that skin stiffness generally correlates with finger size, although it more robustly correlates with and predicts an individual's perceptual acuity.In particular, more elastic skin generates higher rates of deformation, which correlate with perceptual discrimination, shown most dramatically by softening each participant's skin with hyaluronic acid.In refining the current working hypothesis, we show the skin's stiffness strongly shapes the signalling of touch and modulates individual differences in perceptual acuity. 

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