Pressure Stimuli Research Articles

Two-dimensional lead halide perovskite lateral homojunctions enabled by phase pinning

Two-dimensional organic-inorganic hybrid halide perovskites possess diverse structural polymorphs with versatile physical properties, which can be controlled by order-disorder transition of the spacer cation, making them attractive for constructing semiconductor homojunctions. Here, we demonstrate a space-cation-dopant-induced phase stabilization approach to creating a lateral homojunction composed of ordered and disordered phases within a two-dimensional perovskite. By doping a small quantity of pentylammonium into (butylammonium)2PbI4 or vice versa, we effectively suppress the ordering transition of the spacer cation and the associated out-of-plane octahedral tilting in the inorganic framework, resulting in phase pining of the disordered phase when decreasing temperature or increasing pressure. This enables epitaxial growth of a two-dimensional perovskite homojunction with tunable optical properties under temperature and pressure stimuli, as well as directional exciton diffusion across the interface. Our results demonstrate a previously unexplored strategy for constructing two-dimensional perovskite heterostructures by thermodynamic tuning and spacer cation doping.

The impact of size on middle-ear sound transmission in elephants, the largest terrestrial mammal.

Elephants have a unique auditory system that is larger than any other terrestrial mammal. To quantify the impact of larger middle ear (ME) structures, we measured 3D ossicular motion and ME sound transmission in cadaveric temporal bones from both African and Asian elephants in response to air-conducted (AC) tonal pressure stimuli presented in the ear canal (PEC). Results were compared to similar measurements in humans. Velocities of the umbo (VU) and stapes (VST) were measured using a 3D laser Doppler vibrometer in the 7-13,000 Hz frequency range, stapes velocity serving as a measure of energy entering the cochlea-a proxy for hearing sensitivity. Below the elephant ME resonance frequency of about 300 Hz, the magnitude of VU/PEC was an order of magnitude greater than in human, and the magnitude of VST/PEC was 5x greater. Phase of VST/PEC above ME resonance indicated that the group delay in elephant was approximately double that of human, which may be related to the unexpectedly high magnitudes at high frequencies. A boost in sound transmission across the incus long process and stapes near 9 kHz was also observed. We discuss factors that contribute to differences in sound transmission between these two large mammals.

Ultrasensitive Biomimetic Skin with Multimodal and Photoelectric Dual-Signal Sensing.

Mimicking biological skin enabling direct, intelligent interaction between users and devices, multimodal sensing with optical/electrical (OE) output signals is urgently required. Owing to this, this work aims to logically design a stretchable OE biomimetic skin (OE skin), which can sensitively sense complex external stimuli of pressure, strain, temperature, and localization. The OE skin consists of elastic thin polymer-stabilized cholesteric liquid crystal films, an ion-conductive hydrogel layer, and an elastic protective membrane formed with thin polydimethylsiloxane. The as-designed OE skin exhibits customizable structural color on demand, good thermochromism, and excellent mechanochromism, with the ability to extend the full visible spectrum, a good linearity of over 0.99, fast response speed of 93 ms, and wide temperature range of 119 °C. In addition, the conduction resistance variation of ion-conductive hydrogel exhibits excellent sensing capabilities under pressure, stretch, and temperature, endowing a good linearity of 0.99998 (stretching from 0 to 150%) and high thermal sensitivity of 0.86% per °C. Such an outstanding OE skin provides design concepts for the development of multifunctional biomimetic skin used in human-machine interaction and can find wide applications in intelligent wearable devices and human-machine interactions.

Artificial multisensory system with optical feedback for multimodal perceptual imaging

Artificial sensory systems require appropriate input–output modalities to enhance interaction efficiency and accuracy. It is crucial to mimic an organism to perceive and integrate multiple external stimuli and to construct systems with multiple sensory inputs. In addition, the application of optical output to the sensory system not only solves the problem of electrical signal transmission, but also enables direct imaging through optical output. Here, we propose an artificial multisensory system with optical feedback (AMSOF), which can simultaneously receive pressure and thermal stimuli and then generate neuromorphic optical responses along with feedback. Among them, the triboelectric nanogenerator (TENG) is responsible for receiving pressure stimuli, while the artificial light-emitting synaptic device utilizes the quantum dot thermal quenching mechanism to processes temperature signals and generate optical feedback. Additionally, if the AMOFS is applied to the fingerprint recognition system, it can enable fingerprint imaging through dual recognition of these two signals. In other words, it can enhance the security of biometric authentication by adding the capability to distinguish the live nature of objects on top of traditional fingerprint recognition. Therefore, this system aims to achieve more intelligent and efficient human–computer interaction and environmental perception capabilities, bringing forth a multitude of applications and innovations for smart systems.

Analysis of pressure-activated Piezo1 open and subconductance states at a single channel level

Mechanically activated Piezo1 channels undergo transitions from closed to open-state in response to pressure and other mechanical stimuli. However, the molecular details of these mechanosensitive gating transitions are unknown. Here, we used cell-attached pressure-clamp recordings to acquire single channel data at steady-state conditions (where inactivation has settled down), at various pressures and voltages. Importantly, we identify and analyze subconductance states of the channel which were not reported before. Pressure-dependent activation of Piezo1 increases the occupancy of open and subconductance state at the expense of decreased occupancy of shut-states. No significant change in the mean open time of subconductance states was observed with increasing negative pipette pressure or with varying voltages (ranging from -40 to -100 mV). Using Markov-chain modeling we identified a minimal four-states kinetic scheme, which recapitulates essential characteristics of the single channel data, including that of the subconductance level. This study advances our understanding of Piezo1 gating mechanism in response to discrete stimuli (such as pressure and voltage) and paves the path to develop cellular and tissue level models to predict Piezo1 function in various cell types.

Pain catastrophizing in the elderly: An experimental pain study.

Pain catastrophizing in the aging population has not been studied in great detail. Existing investigations have reported conflicting results on the effects of age on pain catastrophizing in relation to pain responses. This study investigated the relationship between pain catastrophizing, and its individual components (rumination, magnification, and helplessness), and the responses to standardized experimental pain stimuli in old and young, healthy adults. Sixty-six volunteers (32 old: 65-87, 18 females; 34 young: 20-35, 17 females) participated in the study. Pain catastrophizing including the components of rumination, magnification, and helplessness was assessed with the pain catastrophizing scale (PCS). Experimental pain was induced by applying predefined pressure stimulations to the trapezius muscle. Pain intensity and unpleasantness were assessed using numerical rating scales. Pain catastrophizing levels and pain responses were statistically compared between the two age groups. Elderly individuals reported significantly (p = 0.028) lower scores of pain catastrophizing (Med = 5; interquartile range [IQR] = 14) than younger individuals; this difference was driven by the significantly lower components of rumination (Med = 2; IQR = 4; p = 0.017) and helplessness (Med = 2; IQR = 7; p = 0.049). A larger proportion of young (57.8%) rated pain catastrophizing at high levels, with scores above the 75th percentile (Med = 20). Additionally, elderly reported the lowest pain intensity (Med = 5; p = 0.034) and pain unpleasantness (Med = 4.5; p = 0.011) responses to the experimental pressure stimuli. In the elderly group, pain unpleasantness was positively and significantly associated with pain catastrophizing (r s = 0.416, p = 0.021), rumination (r s = 0.42, p = 0.019), and helplessness (r s = 0.434, p = 0.015), respectively. No associations were found in the young group. Elderly reported lower PCSs than young adults. Rumination and helplessness were reduced in the elderly group. The elderly population showed positive correlations between catastrophizing levels and pain unpleasantness to standardized pressure pain stimuli. Results supported the view that elderly possess resilience over specific domains of pain catastrophizing that could counteract pain perception due to physiological decline.

Aged females unilaterally hypersensitize, lack descending inhibition, and overexpress alpha1D adrenergic receptors in a murine posttraumatic chronic pain model.

Vulnerability to chronic pain is found to depend on age and sex. Most patients with chronic pain are elderly women, especially with posttraumatic pain after bone fracture that prevails beyond the usual recovery period and develops into a complex regional pain syndrome (CRPS). There, a distal bone fracture seems to initiate a pathophysiological process with unknown mechanism. To investigate whether sex, age, and alpha adrenergic receptors also contribute to a CRPS-like phenotype in animals, we performed experiments on tibia-fractured mice. Those mice commonly are resilient to the development of a CRPS-like phenotype. However, we found them to be vulnerable to long-lasting pain after distal bone fracture when they were of old age. These mice expressed mechanical and thermal hypersensitivity, as well as weight-bearing and autonomic impairment following bone trauma, which persisted over 3 months. Site-specific and body side-specific glycinergic and α1D-noradrenergic receptor expression in the spinal cord and the contralateral locus coeruleus were misbalanced. Aged female tibia-fractured mice lost descending noradrenergic inhibition and displayed enhanced spinal activity on peripheral pressure stimuli. Together, changes in the noradrenergic, hence, glycinergic system towards excitation in the pain pathway-ascending and descending-might contribute to the development or maintenance of long-lasting pain. Conclusively, changes in the noradrenergic system particularly occur in aged female mice after trauma and might contribute to the development of long-lasting pain. Our data support the hypothesis that some patients with chronic pain would benefit from lowering the adrenergic/sympathetic tone or antagonizing α1(D).

Beetle‐Inspired Gradient Slant Structures for Capacitive Pressure Sensor with a Broad Linear Response Range

AbstractFlexible pressure sensors with broad linearity range and excellent sensor‐to‐sensor uniformity have attracted unprecedented attention in the electronic skins, human–machine interfaces, and environmental monitoring. However, challenges including poor sensor‐to‐sensor uniformity owing to the randomness of the used nanomaterials or porous structures and saturated response that leads to a restricted linearity range because of structural stiffening have been yet addressed. Herein, a novel dielectric layer based on beetle‐inspired gradient slant structures (GSS) is proposed to endow capacitive pressure sensors with extensive linearity range and excellent sensor‐to‐sensor uniformity. The excellent compressibility of the GSS due to the bending deformation of the slant pillars significantly enhances sensor sensitivity. The broad linearity range comes from the compensation of contact area during sequential contact of the GSS dielectric layer from tall to low slant pillars with electrodes. The high sensor‐to‐sensor uniformity is ascribed to the excellent batch‐to‐batch consistency of prepared GSS via 3D printing‐based fabrication process. Moreover, the proposed GSS‐based pressure sensors present rapid response/recovery, low detection limit, excellent dynamic response, negligible hysteresis, and outstanding long‐term stability. Finally, the excellent applicabilities of proposed capacitive pressure sensors in diverse scenarios including external pressure stimuli detection, a flexible perception array, and a smart insole system are demonstrated.

All laser direct writing process for temperature sensor based on graphene and silver

A highly sensitive temperature sensing array is prepared by all laser direct writing (LDW) method, using laser induced silver (LIS) as electrodes and laser induced graphene (LIG) as temperature sensing layer. A finite element analysis (FEA) photothermal model incorporating a phase transition mechanism is developed to investigate the relationship between laser parameters and LIG properties, providing guidance for laser processing parameters selection with laser power of 1–5 W and laser scanning speed (greater than 50 mm/s). The deviation of simulation and experimental data for widths and thickness of LIG are less than 5% and 9%, respectively. The electrical properties and temperature responsiveness of LIG are also studied. By changing the laser process parameters, the thickness of the LIG ablation grooves can be in the range of 30–120 μm and the resistivity of LIG can be regulated within the range of 0.031–67.2 Ω·m. The percentage temperature coefficient of resistance (TCR) is calculated as − 0.58%/°C. Furthermore, the FEA photothermal model is studied through experiments and simulations data regarding LIS, and the average deviation between experiment and simulation is less than 5%. The LIS sensing samples have a thickness of about 14 μm, an electrical resistivity of 0.0001–100 Ω·m is insensitive to temperature and pressure stimuli. Moreover, for a LIS-LIG based temperature sensing array, a correction factor is introduced to compensate for the LIG temperature sensing being disturbed by pressure stimuli, the temperature measurement difference is decreased from 11.2 to 2.6 °C, indicating good accuracy for temperature measurement.Graphical

A Review on the Role of Neuroplasticity in Neurodegenerative Disorders and Its Possible Pharmacological and Non-Pharmacological Interventions

Neuroplasticity is the capability of brain cells to interchange as well as modify for the ultimate cause of higher proficiency to acclimatize to the new situations. Neuroplasticity also plays a very pivotal role in the development and then further progressing of neurodegenerative disorders. The severe adjustments in neural plasticity caused by high pressure, anxiety and other terrible stimuli like stress play a considerable role in the onset and cause of depression. This comprehensive review explores the pivotal role of neuroplasticity in neurodegenerative disorders, shedding light on the dynamic adaptive processes of the nervous system in response to pathological conditions. The paper synthesizes current research findings to elucidate the intricate interplay between neuroplasticity and the progression of neurodegenerative diseases. Furthermore, it delves into potential pharmacological and non-pharmacological interventions aimed at modulating neuroplasticity to ameliorate or mitigate the impact of these disorders. By examining diverse strategies, from pharmaceutical interventions to lifestyle modifications, this review contributes to a nuanced understanding of the multifaceted mechanisms underlying neurodegeneration and offers insights into promising avenues for therapeutic development.

A biomimetic nociceptor system with tactile perception based on Ni-Al layered double hydroxides/gelatin heterojunction memristor

The sensations of touch and pain are fundamental components of our daily existence, serving as conduits for providing crucial insights into our environment and ensuring the safeguarding of our health. To date, the exploration of artificial systems that combine pain and touch perception has remained very limited. Moreover, memristor based visualization of pain degree is rarely reported. The electronic simulation of the from pressure stimuli to nociceptors was conducted in this work. For this purpose, a bionic sensory system has been developed to present tactile perception. In this system, the piezoelectric film sensor serves as an electronic skin to mimic artificial mechanoreceptors for sensing external pressure stimulation and generating signals. Meanwhile, the Ni-Al layered double hydroxides (LDHs)/gelatin heterojunction memristor emulates biological nociceptors to receive and process receptor signals, with luminous diode used as displays to indicate the degree of artificial contusion. The Ni-Al LDHs/gelatin heterojunction memristor demonstrates essential characteristics of nociceptors, including threshold, no adaptation, relaxation, and sensitization phenomena of allodynia and hyperalgesia. This biomimetic artificial tactile and pain perception system successfully simulates the perception threshold and sensitivity to pressure stimuli. The potential ability of humanoid robots could be demonstrated by utilizing the system as an artificial tactile alarm system.

Examining Reactivity and Recovery Patterns of Pain-Evoked Cortisol and Alpha-Amylase Trajectories: Relations Between Psychological Markers of Risk and Resilience

Chronic low back pain (cLBP) is one of the leading causes of disability globally and represents an enormous burden to aging adults. While numerous factors contribute to cLBP, dysregulation in the hypothalamic-pituitary-adrenal axis and autonomic nervous system functioning have been implicated in its pathogenesis. It is well documented that negative psychological states can modulate biological stress responsivity in chronic pain; however, little is known regarding the influence of positive psychological factors in this relationship. The aim of this study was to examine the association between psychological risk and resilience factors with patterns of physiological stress reactivity and recovery in 60 older adults with cLBP. Participants completed measures of hope, optimism, pain catastrophizing, and perceived stress, and underwent psychophysical pain testing assessing responses to painful pressure, heat, and cold stimuli. Salivary samples were obtained prior to pain induction and at 7 time points spanning 90 minutes after pain testing terminated. To examine reactivity and recovery profiles in hypothalamic-pituitary-adrenal axis and autonomic nervous system function, samples were assayed for cortisol and alpha-amylase, respectively. Results revealed higher levels of hope and optimism were associated with increased cortisol reactivity (p’s < .003) and more rapid recovery (p’s = .001). Further, pain catastrophizing and perceived stress were associated with cortisol reactivity, with lower levels of these factors predicting larger increases in cortisol from baseline to peak levels (p’s < .04). No significant differences in reactivity or recovery patterns emerged for alpha-amylase. Overall, findings highlight the role of psychological risk and resilience factors in modulating physiological stress reactivity. PerspectiveThis article investigated whether psychosocial risk and resilience factors were associated with stress reactivity and recovery in response to laboratory-based pain testing in older adults with chronic low back pain. Results indicate that high resilience factors may be protective by modulating adrenocortical reactivity and recovery profiles.

Pressure Stimuli and Spatiotemporal Illusions on the Forearm.

To design complex wearable haptic interfaces using pressure, we have to explore how we can use pressure stimuli to their full potential. Haptic illusions, such as apparent motion and apparent location, can be a part of this. If these illusions can be evoked with pressure, haptic patterns can increase in complexity without increasing the number of actuators or combining different types of actuators. We did two psychophysical experiments with pressure stimuli on the forearm using a pneumatic sleeve with multiple, individually controlled McKibben actuators. In Experiment 1, we found that spatial integration of two simultaneously presented stimuli occurred for distances up to 61 mm. In Experiment 2, we found that apparent motion can be elicited with distinct pressure stimuli over a range of temporal parameters. These results clearly show spatio-temporal integration in the somatosensory system for pressure stimuli. We discuss these findings in relation to effects found for vibration and the mechanoreceptors in the glabrous skin.

Perception Threshold for Pressure by a Soft Textile Actuator.

Electroactive textile (EAT) has the potential to apply pressure stimuli to the skin, e.g. in the form of a squeeze on the arm. To present a perceivable haptic sensation we need to know the perception threshold for such stimuli. We designed a set-up based on motorized ribbons around the arm with five different widths (range 3 - 49 mm) for psychophysical studies. We investigated the perception threshold of force pressure and ribbon reduction in two studies, using two methods (PSI and 1up/3down staircase), comparing sex, the left and right arm, the lower and upper arm, and stimulated surface area with a total of 57 participants. We found that larger stimulation surfaces require less pressure to reach the perception threshold (0.151 N per cm 2 for 3 mm width, 0.00972 N per cm 2 for 49 mm width on the lower arm). This indicates a spatial summation effect for these pressure stimuli. We did not find significant differences in perception threshold for the left and right arm and, the upper and lower arm. Between male and female participants we found significant differences for two conditions (10 mm and 25 mm) in Experiment 1, but we could not reproduce this in Experiment 2.

Decoding Human Somatosensory Sensitivity Through Resting EEG and Behavioral Analysis: A Multimodal Fusion Approach.

In precision medicine and clinical pain management, the creation of quantitative, objective indicators to assess somatosensory sensitivity was essential. This study proposed a fusion approach for decoding human somatosensory sensitivity, which combined multimodal (quantitative sensory test and neurophysiology) features to classify the dataset on individual somatosensory sensitivity and reveal distinct types of brain activation patterns. Sixty healthy participants took part in the experiment on somatosensory sensitivity that implemented cold, heat, mechanical punctate, and pressure stimuli, and the resting-state electroencephalography (EEG) was collected using BrainVision. The quantitative sensory testing (QST) scores of the participants were clustered using the unsupervised k-means algorithm into four subgroups: generally hypersensitive (HS), generally non-sensitive (NS), predominantly thermally sensitive (TS), and predominantly mechanically sensitive (MS). Furthermore, two types of power spectral density (PSD), band-based PSD (BB-PSD) and frequency-based PSD (FB-PSD), and two types of inter-electrode connectivity (IEC), band-based connectivity (BBC) and frequency-based connectivity (FBC), derived from resting-state EEG were subjected to feature selection with a proposed prior-compared minimum-redundancy maximum-relevance (PCMRMR) protocol. Their effectiveness was then tested by the supervised classification tasks using support vector machine (SVM), k-nearest neighbor (kNN), random forest (RF), and Gaussian classifier (GC). Brain networks of four somatosensory types were revealed by decoding fused multimodal data, namely type-averaged connectivity. The data from sixty healthy individuals were divided into training (n =59) and validation (n =1) datasets according to leave-one-subject-out (LOSO) criteria. The FBC was identified, which can serve as better brain signatures than BB-PSD, FB-PSD, and BBC to classify subjects as HS, NS, TS, or MS groups. Using the SVM, kNN, RF, and GC models, the best accuracy of 87% was obtained when classifying participants into HS, NS, TS, or MS groups. Moreover, the brain networks were decoded from HS, NS, TS, and MS groups by decoding the type-averaged connectivity fused from somatosensory phenotypes and selected FBC. It indicated that quantified multi-parameter somatosensory sensitivity could be achieved with acceptable accuracy, leading to considerable possibilities for using objective pain perception evaluation in clinical practice.

Comparison of Thermal and Mechanical Pain Testing Modalities in Sprague Dawley and Fischer 344 Rats (Rattus norvegicus).

While rodents are used extensively for studying pain, there is a lack of reported direct comparisons of thermal and mechanical pain testing methods in rats of different genetic backgrounds. Understanding the range of interindividual variability of withdrawal thresholds and thermal latencies based on these testing methods and/or genetic background is important for appropriate experimental design. Testing was performed in two common rat genetic backgrounds: outbred Sprague-Dawley (SD) and inbred Fischer 344 (F344). Male and female, 10- to 14-wk-old F344 and SD rats were used to assess withdrawal thresholds in 3 different modalities: the Randall-Selitto test (RST), Hargreaves test (HT), and tail flick test (TFT). The RST was performed by using an operator-controlled handheld instrument to generate a noxious pressure stimulus to the left hind paw. The HT and the TFT used an electronically controlled light source to deliver a noxious thermal stimulus to the left hind paw or tail tip, respectively. Rats of each sex and genetic background underwent one type of test on day 0 and day 7. Withdrawal thresholds and thermal latencies were compared among tests. No significant differences were observed. Our findings can serve as a guide for researchers considering these nociceptive tests for their experiments.

Association between myofascial trigger point therapy and conditioned pain modulation

IntroductionMyofascial trigger point therapy (MTrP) is a widely used therapeutic approach, although the underlying mechanisms remain unclear. Mechanisms discussed include peripheral involvement of muscles as well as central pain modulating processes such as the conditioned pain modulation (CPM). The aim of this study was to investigate whether the analgesic response of MTrP and the analgesic response of CPM correlate in asymptomatic participants in order to identify shared underlying mechanisms of MTrP and CPM. MethodBoth, CPM and MTrP protocols consisted of heat-based test stimuli (heat pain thresholds before and after the intervention) and pressure-based (conditioning) stimuli. Asymptomatic participants (n = 94) were randomly assigned to receive either mild, intense or no pressure stimuli (between-group design) to both the fingernail and the MTrP of the infraspinatus muscle (within-group design). Pressure stimuli at both locations (fingernail, MTrP) were applied with a pressure algometer for 120 s and continuously adjusted to maintain a constant pain intensity of mild or intense pain. All thermal stimuli were applied on the lower leg with a thermal stimulator. ResultsA significant correlation was shown between the analgesic effect of CPM and MTrP therapy for mild (r = 0.53, p = 0.002) and intensive stimuli (r = 0.73, p < 0.001). 17.3% of the variance of the MTrP effect were explained by CPM after mild stimulation, and 47.1% after intense stimulation. Pain-related characteristics did not explain the variance within the analgesic response using a regression analysis. ConclusionsBetween the analgesic responses following MTrP and CPM paradigms, a moderate to strong correlation was observed, suggesting shared underlying mechanisms.

Artificial Tactile Perception System Based on Spiking Tactile Neurons and Spiking Neural Networks.

The artificial tactile perception system of this work utilizes a fully connected spiking neural network (SNN) comprising two layers. Its architecture is streamlined and energy-efficient as it directly integrates spiking tactile neurons with piezoresistive sensors and Pt/NbOx/TiN memristors as input neurons. These spiking tactile neurons possess the ability to perceive and integrate pressure stimuli from multiple sensors and encode the information into rate-coded electrical spikes, closely resembling the behavior of a biological tactile neuron. The system's real-time information processing capability is demonstrated through an artificial perceptual learning system that successfully encodes and decodes the Morse code; the artificial perceptual learning system accurately recognizes and displays 26 English letters. Furthermore, the artificial tactile perception system is evaluated for the recognition of the MNIST data set, achieving a classification accuracy of 85.7% with the supervised spiking-rate-dependent plasticity learning rule. The key advantages of this artificial tactile perception system are its simple structure and high efficiency, which contributes to its practicality for various real-world applications.

Straining the root on and off triggers local calcium signalling.

A fundamental function of an organ is the ability to perceive mechanical cues. Yet, how this is accomplished is not fully understood, particularly in plant roots. In plants, the majority of studies dealing with the effects of mechanical stress have investigated the aerial parts. However, in natural conditions roots are also subjected to mechanical cues, for example when the root encounters a hard obstacle during its growth or when the soil settles. To investigate root cellular responses to root compression, we developed a microfluidic system associated with a microvalve allowing the delivery of controlled and reproducible mechanical stimulations to the root. In this study, examining plants expressing the R-GECO1-mTurquoise calcium reporter, we addressed the root cell deformation and calcium increase induced by the mechanical stimulation. Lateral pressure applied on the root induced a moderate elastic deformation of root cortical cells and elicited a multicomponent calcium signal at the onset of the pressure pulse, followed by a second one at the release of the pressure. This indicates that straining rather than stressing of tissues is relevant to trigger the calcium signal. Although the intensity of the calcium response increases with the pressure applied, successive pressure stimuli led to a remarkable attenuation of the calcium signal. The calcium elevation was restricted to the tissue under pressure and did not propagate. Strain sensing, spatial restriction and habituation to repetitive stimulation represent the fundamental properties of root signalling in response to local mechanical stimulation. These data linking mechanical properties of root cells to calcium elevation contribute to elucidating the pathway allowing the root to adapt to the mechanical cues generated by the soil.

Pressure stimulus study on acupuncture points with multi-channel multimode-fiber diffuse speckle contrast analysis (MMF-DSCA).

A multi-channel multimode-fiber deep tissue flowmetry system has been constructed based on diffuse speckle contrast analysis (DSCA) for simultaneous blood flow measurements at different locations on the human body. This system has been utilized in an acupuncture study within the field of traditional Chinese medicine (TCM), primarily focusing on acupuncture points along the large intestine meridian. Deep tissue blood flow was monitored at four different acupuncture points (LI1, LI5, LI10, and ST25) with a sampling rate of 60 Hz while applying pressure stimulus on LI4 (hegu or hapgok). Although the blood flow index (BFI) and blood volume (BV) did not exhibit significant changes after the pressure stimulus, an increase in the amplitude and complexity of low-frequency oscillations (LFOs) in microcirculation was observed.