Texture Discrimination Research Articles

Human Tactile Discrimination of Pulse Shape Is Possible Without Pre-Adaptation.

Recent progress in the field of tactile coding suggests that discrimination of texture may involve the instantaneous kinematic analysis of frictional stick-slip movements. The idea has received support from analytical psychophysical experiments employing changes of pulsatile skin deflections in a well-adapted state - i.e. when changing repetitive pulsatile stimulation from one pulse shape to another. Here we investigated whether perception of pulse shapes is possible with single, isolated pulses. In other words, whether the well-described neuronal 'onset-responses' in central parts of the tactile pathway, which differ largely from 'adapted responses', carry information about pulse shape. We tested human participants on a pulse shape 2AFC discrimination paradigm: in each trial, 3 pulsatile skin indentations were presented at an interval of 0.5s. Either the first or the last pulse deviated in its shape, which the participants had to correctly identify. The task could not be solved by simply integrating tactile response across the 3 pulses. A majority of the participants (18 out of 30) yielded a performance of p(correct)>0.75, indicating that isolated pulse shapes reach perception. The performance was enhanced by presenting the same shape changes in the context of a preadapting series of pulses. Participants confronted with the 3-pulse test did not show a systematic preference for the kinematic parameter used to change the shape. We conclude that perceptual processes in principle have access to the kinematic shape of isolated pulsatile skin deflections. However, sensory adaption plays a crucial role for the quality and specificity of encoding kinematic pulse profiles.

Role of TRPV channels in texture discrimination during Bactrocera dorsalis egg-laying behaviour.

Deciding where to lay an egg is critical for the survival of insects' offspring. Compared with our understanding of the chemosensory assessment of egg-laying sites, the mechanisms of texture detection are largely unknown. Here, we show that Bactrocera dorsalis, a notoriously agricultural pest laying its eggs within ripening fruits, can discriminate substrate texture during the egg-laying process. Exposure to drugs targeting transient receptor potential vanilloid (TRPV) mechanosensory channels abolished their oviposition preference for hard textures. BdorNan and BdorIav are two members of the TRPV subfamily, and their transcripts were detected in the labellum, the foreleg tarsi and the ovipositor. Then, we successfully obtained knockout strains of each gene using the CRISPR/Cas9 technique. The results showed that BdorNan is required for the discrimination of stiffness difference. BdorIav knockout had no significant effect on the ability of B. dorsalis to choose harder substrates. Our study thus reveals that BdorNan plays a substantial role in the texture assessment of egg-laying behaviour in B. dorsalis.

Generalization in perceptual learning across stimuli and tasks

Perceptual learning, known to improve visual perception, demonstrates the plasticity of brain processes underlying vision. Early studies, using the backward-masked texture discrimination task (TDT), focused on the lack of generalizing learning to stimulus features, relating learning specificity to the selectivity of the brain networks involved in the visual task. Learning was found to be highly specific to the stimulus features, as expected from the processing selectivity found in early visual areas as well as to the task employed in training, pointing to top-down effects. More recent studies demonstrate the generalization of learning to untrained features under specifically designed training procedures. Here we suggest that transfer of learning takes place when the trained and untrained stimuli and task activate overlapping brain processes. We tested the effect of TDT learning, under conditions with and without visual adaptation, on the contrast detection (CD) of localized Gabor targets, either alone or backward masked (BM). At the TDT peripheral-target location, we found that the transfer of learning between TDT to CD and BM occurs under the TDT adaptation condition, but not under the no-adaptation condition, whereas at the TDT center-target location we found that transfer occurs for both conditions. Our results suggest that learning generalization across experimental conditions depends on overlapping neural processes within brain networks, here dominated by the inhibitory effects involved in adaptation and in spatiotemporal masking. Importantly, increased adaptation during training, due to increased stimulus consistency, enabled the transfer of learning to other tasks limited by sensory adaptation.

Processing the fine-grained features of tactile textures involves the primary somatosensory cortex

Abstract Dynamic tactile perception and discrimination of textures require the ability to encode and differentiate complex vibration patterns elicited at the level of the skin when sliding against a surface. Whether the primary somatosensory cortex (S1) can encode the fine-grained spectrotemporal features distinguishing textures remains debated. To address this question, EEG frequency-tagging was used to characterize responses to vibrotactile oddball contrasts between two textures. In a first session designed to identify the topographical distribution of responses originating from the hand and foot representations in S1, standard and deviant stimuli were pure sinusoidal vibrations differing in frequency and intensity. In a second session, standard and deviant stimuli were two different snippets of bandpass-filtered white noise matched in terms of intensity and average frequency content, but differing in terms of their complex spectrotemporal content. Using the S1 functional localizer, we showed that oddball responses to a spectrotemporal contrast follow the somatotopical organization of S1. Our results suggest that the encoding of fine-grained spectrotemporal features associated with different vibration patterns involves S1.

Biometric-Tuned E-Skin Sensor with Real Fingerprints Provides Insights on Tactile Perception: Rosa Parks Had Better Surface Vibrational Sensation than Richard Nixon.

The dense mechanoreceptors in human fingertips enable texture discrimination. Recent advances in flexible electronics have created tactile sensors that effectively replicate slowly adapting (SA) and rapidly adapting (RA) mechanoreceptors. However, the influence of dermatoglyphic structures on tactile signal transmission, such as the effect of fingerprint ridge filtering on friction-induced vibration frequencies, remains unexplored. A novel multi-layer flexible sensor with an artificially synthesized skin surface capable of replicating arbitrary fingerprints is developed. This sensor simultaneously detects pressure (SA response) and vibration (RA response), enabling texture recognition. Fingerprint ridge patterns from notable historical figures - Rosa Parks, Richard Nixon, Martin Luther King Jr., and Ronald Reagan - are fabricated on the sensor surface. Vibration frequency responses to assorted fabric textures are measured and compared between fingerprint replicas. Results demonstrate that fingerprint topography substantially impacts skin-surface vibrational transmission. Specifically, Parks' fingerprint structure conveyed higher frequencies more clearly than those of Nixon, King, or Reagan. This work suggests individual fingerprint ridge morphological variation influences tactile perception and can confer adaptive advantages for fine texture discrimination. The flexible bioinspired sensor provides new insights into human vibrotactile processing by modeling fingerprint-filtered mechanical signals at the finger-object interface.

Amelioration of behavioral and histological impairments in somatosensory cortex injury rats by limbal mesenchymal stem cell transplantation.

Cortical lesions can cause major sensory and motor impairments, representing a significant challenge in neuroscience and clinical medicine. Limbal mesenchymal stem cells (LMSCs), renowned for their remarkable ability to proliferate and distinct characteristics within the corneal epithelium, offer a promising opportunity for regenerative treatments. This study aimed to assess whether the transplantation of LMSCs could improve tactile ability in rats with lesions of the barrel cortex. In this experimental study, we divided 21 rats into three groups: a control group, a lesion group with cortical cold lesion induction but no stem cell treatment, and a group receiving LMSC transplantation following cold lesion induction. We conducted 3-week sensory assessments using a texture discrimination test and an open-field test. We also performed Nissl staining to assess changes on the cellular level. Rats in the LMSC transplantation group demonstrated significant improvements in their ability to discrimination textures during the second and third weeks compared to those in the lesion group. The open-field test results showed an increased exploratory behavior of rats in the LMSC transplantation group by the third week compared to the lesion group. Additionally, Nissl staining revealed cellular alterations in the damaged cortex, with a significant distinction observed between rats in the LMSCs and lesion group. The findings suggest that LMSC transplantation enhances sensory recovery in rats with cortical lesions, particularly their ability to discriminate textures. LMSC transplantation benefits brain tissue reparation after a cold lesion on the somatosensory cortex.

Developmental Cajal-Retzius cell death contributes to the maturation of layer 1 cortical inhibition and somatosensory processing

The role of developmental cell death in the formation of brain circuits is not well understood. Cajal-Retzius cells constitute a major transient neuronal population in the mammalian neocortex, which largely disappears at the time of postnatal somatosensory maturation. In this study, we used mouse genetics, anatomical, functional, and behavioral approaches to explore the impact of the early postnatal death of Cajal-Retzius cells in the maturation of the cortical circuit. We find that before their death, Cajal-Retzius cells mainly receive inputs from layer 1 neurons, which can only develop their mature connectivity onto layer 2/3 pyramidal cells after Cajal-Retzius cells disappear. This developmental connectivity progression from layer 1 GABAergic to layer 2/3 pyramidal cells regulates sensory-driven inhibition within, and more so, across cortical columns. Here we show that Cajal-Retzius cell death prevention leads to layer 2/3 hyper-excitability, delayed learning and reduced performance in a multi-whisker-dependent texture discrimination task.

An effective textured Novel Object Recognition Test (tNORT) for repeated measure of whisker sensitivity of rodents

Rodents use their whisker system to discriminate surface texture. Whisker-based texture discrimination tasks are often used to investigate the mechanisms encoding tactile sensation. One such task is the textured Novel Object Recognition Test (tNORT). It takes advantage of a tendency of rodents to explore novel objects more than familiar ones and assesses the sensitivity of whiskers in discriminating different textures of objects. It requires little training of the animals and the equipment involved is a simple arena with typically two objects placed inside. The success of the test relies on rodents spending sufficient time exploring these objects. Animals may lose interests in such tasks when performed repetitively within a limited time frame. However, such repeated tests may be crucial when establishing a sensitivity threshold of the whisker system. Here we present an adapted rodent tNORT protocol designed to maintain sustained interest in the objects even with repeated testing. We constructed complex objects from three simple-shaped objects. Different textures were provided by sandpapers of varying grit sizes. To minimise olfactory clues, we used the sandy and the laminar side of the same sandpaper as the familiar and novel textures assigned at random. We subsequently conducted repeated tNORTs on eight rats in order to identify a critical threshold of the sandpaper grit size below which rats would be unable to discriminate the sandy from the laminar side. With an inter-test-interval of seven days and after five tNORTs, the protocol enabled us to successfully identify the threshold. We suggest that the proposed tNORT is a useful tool for investigating the sensitivity threshold of the whisker system of rodent, and for testing the effectiveness of an intervention by comparing sensitivity threshold pre- and post-intervention.

Enhancing touch sensibility with sensory electrical stimulation and sensory retraining

A large proportion of stroke survivors suffer from sensory loss, negatively impacting their independence, quality of life, and neurorehabilitation prognosis. Despite the high prevalence of somatosensory impairments, our understanding of somatosensory interventions such as sensory electrical stimulation (SES) in neurorehabilitation is limited. We aimed to study the effectiveness of SES combined with a sensory discrimination task in a well-controlled virtual environment in healthy participants, setting a foundation for its potential application in stroke rehabilitation. We employed electroencephalography (EEG) to gain a better understanding of the underlying neural mechanisms and dynamics associated with sensory training and SES. We conducted a single-session experiment with 26 healthy participants who explored a set of three visually identical virtual textures—haptically rendered by a robotic device and that differed in their spatial period—while physically guided by the robot to identify the odd texture. The experiment consisted of three phases: pre-intervention, intervention, and post-intervention. Half the participants received subthreshold whole-hand SES during the intervention, while the other half received sham stimulation. We evaluated changes in task performance—assessed by the probability of correct responses—before and after intervention and between groups. We also evaluated differences in the exploration behavior, e.g., scanning speed. EEG was employed to examine the effects of the intervention on brain activity, particularly in the alpha frequency band (8–13 Hz) associated with sensory processing. We found that participants in the SES group improved their task performance after intervention and their scanning speed during and after intervention, while the sham group did not improve their task performance. However, the differences in task performance improvements between groups only approached significance. Furthermore, we found that alpha power was sensitive to the effects of SES; participants in the stimulation group exhibited enhanced brain signals associated with improved touch sensitivity likely due to the effects of SES on the central nervous system, while the increase in alpha power for the sham group was less pronounced. Our findings suggest that SES enhances texture discrimination after training and has a positive effect on sensory-related brain areas. Further research involving brain-injured patients is needed to confirm the potential benefit of our solution in neurorehabilitation.

Early cortical GABAergic interneurons determine the projection patterns of L4 excitatory neurons.

During cerebral cortex development, excitatory pyramidal neurons (PNs) establish specific projection patterns while receiving inputs from GABAergic inhibitory interneurons (INs). Whether these inhibitory inputs can shape PNs' projection patterns is, however, unknown. While layer 4 (L4) PNs of the primary somatosensory (S1) cortex are all born as long-range callosal projection neurons (CPNs), most of them acquire local connectivity upon activity-dependent elimination of their interhemispheric axons during postnatal development. Here, we demonstrate that precise developmental regulation of inhibition is key for the retraction of S1L4 PNs' callosal projections. Ablation of somatostatin INs leads to premature inhibition from parvalbumin INs onto S1L4 PNs and prevents them from acquiring their barrel-restricted local connectivity pattern. As a result, adult S1L4 PNs retain interhemispheric projections responding to tactile stimuli, and the mice lose whisker-based texture discrimination. Overall, we show that temporally ordered IN activity during development is key to shaping local ipsilateral S1L4 PNs' projection pattern, which is required for fine somatosensory processing.

Implications of tactile enrichment on the behaviour and whisker movements of four species of carnivorans

Caniformia include a range of aquatic, semi-aquatic and terrestrial species, which reveal diversity in their whisker arrangements and shape. Whisker movements play a crucial role in the perception of tactile information, allowing whiskered mammals to distinguish between shapes, sizes, and textures. Despite the significance of whisker movements in sensory perception, few studies have focussed on measuring whisker movements during tactile sensing. Whisker enrichment tasks have the potential to expand behavioural repertoires of animals in captivity and reduce stereotypical behaviours. However, despite whiskers being essential in guiding foraging and exploration in many mammalian species, tactile whisker enrichment tasks are rare. Here, we utilised a novel tactile enrichment device to investigate the whisker movements in four Caniform species in captivity, including two pinnipeds- South African fur seals (Arctocephalus pussilus) and harbour seals (Phoca vitulina), a mustelid – Eurasian otter (Lutra lutra), and a canid – red fox (Vulpes vulpes) during a texture discrimination task. This study is the first to explore the impact of tactile enrichment on the behavioural repertoire of caniforms in captivity and provides the first insight of whisker movements in South African fur seals. The introduction of the tactile enrichment device did not increase the behavioural repertoire, nor did it lead to an increase in stereotypical behaviours or aggression in any of the species. However, it did successfully encourage natural whisker movements in the pinnipeds and otter. The whisker amplitude measure was especially high in the South African fur seals. We suggest that such a complex, discrimination-based enrichment task might only be feasible for more trainable caniforms, such as pinnipeds, rather than more neophobic species, such as the red fox, which did not interact with the enrichment device throughout the study. Therefore, while our enrichment device increased natural whisker movements, an even simpler foraging task might encourage tactile sensing without the requirement for training, making tactile whisker enrichment available to a wider group of species.

Alterations of Perineuronal Net Expression and Abnormal Social Behavior and Whisker-dependent Texture Discrimination in Mice Lacking the Autism Candidate Gene Engrailed 2

GABAergic interneurons and perineuronal nets (PNNs) are important regulators of plasticity throughout life and their dysfunction has been implicated in the pathogenesis of several neuropsychiatric conditions, including autism spectrum disorders (ASD). PNNs are condensed portions of the extracellular matrix (ECM) that are crucial for neural development and proper formation of synaptic connections.We previously showed a reduced expression of GABAergic interneuron markers in the hippocampus and somatosensory cortex of adult mice lacking the Engrailed2 gene (En2-/- mice), a mouse model of ASD. Since alterations in PNNs have been proposed as a possible pathogenic mechanism in ASD, we hypothesized that the PNN dysfunction may contribute to the neural and behavioral abnormalities of En2-/- mice. Here, we show an increase in the PNN fluorescence intensity, evaluated by Wisteria floribunda agglutinin, in brain regions involved in social behavior and somatosensory processing. In addition, we found that En2-/- mice exhibit altered texture discrimination through whiskers and display a marked decrease in the preference for social novelty.Our results raise the possibility that altered expression of PNNs, together with defects of GABAergic interneurons, might contribute to the pathogenesis of social and sensory behavioral abnormalities.

An Ensemble Method for EEG-based Texture Discrimination during Open Eyes Active Touch

Touch sensation is a key modality that allows humans to understand and interact with their environment. More often than not, touch sensation depends on vision to accumulate and validate the received information. The ability to distinguish between materials and surfaces through active touch consists of a complex of neurophysiological operations. To unveil the functionality of these operations, neuroimaging and neurophysiological research tools are employed, with electroencephalography being the most used. In this paper, we attempt to distinguish between brain states when touching different natural textures (smooth, rough, and liquid). Recordings were obtained with a commercially available EEG wearable device. Time and frequency-based features were extracted, transformed with PCA decomposition, and an ensemble classifier combining Random Forest, Support Vector Machine, and Neural Network was utilized. High accuracy scores of 79.64% for the four-class problem and 89.34% for the three-class problem (Null-Rough-Water) were accordingly achieved. Thus, the methodology's robustness indicates its ability to classify different brain states under haptic stimuli.

Behavior-relevant top-down cross-modal predictions in mouse neocortex.

Animals adapt to a constantly changing world by predicting their environment and the consequences of their actions. The predictive coding hypothesis proposes that the brain generates predictions and continuously compares them with sensory inputs to guide behavior. However, how the brain reconciles conflicting top-down predictions and bottom-up sensory information remains unclear. To address this question, we simultaneously imaged neuronal populations in the mouse somatosensory barrel cortex and posterior parietal cortex during an auditory-cued texture discrimination task. In mice that had learned the task with fixed tone-texture matching, the presentation of mismatched pairing induced conflicts between tone-based texture predictions and actual texture inputs. When decisions were based on the predicted rather than the actual texture, top-down information flow was dominant and texture representations in both areas were modified, whereas dominant bottom-up information flow led to correct representations and behavioral choice. Our findings provide evidence for hierarchical predictive coding in the mouse neocortex.

Reliability and stability of tactile perception in the whisker somatosensory system.

Rodents rely on their whiskers as vital sensory tools for tactile perception, enabling them to distinguish textures and shapes. Ensuring the reliability and constancy of tactile perception under varying stimulus conditions remains a fascinating and fundamental inquiry. This study explores the impact of stimulus configurations, including whisker movement velocity and object spatial proximity, on texture discrimination and stability in rats. To address this issue, we employed three distinct approaches for our investigation. Stimulus configurations notably affected tactile inputs, altering whisker vibration's kinetic and kinematic aspects with consistent effects across various textures. Through a texture discrimination task, rats exhibited consistent discrimination performance irrespective of changes in stimulus configuration. However, alterations in stimulus configuration significantly affected the rats' ability to maintain stability in texture perception. Additionally, we investigated the influence of stimulus configurations on cortical neuronal responses by manipulating them experimentally. Notably, cortical neurons demonstrated substantial and intricate changes in firing rates without compromising the ability to discriminate between textures. Nevertheless, these changes resulted in a reduction in texture neuronal response stability. Stimulating multiple whiskers led to improved neuronal texture discrimination and maintained coding stability. These findings emphasize the importance of considering numerous factors and their interactions when studying the impact of stimulus configuration on neuronal responses and behavior.

Real-response Texture Discriminator for Quality Evaluation of Carbonated Beverages

Real-response Texture Discriminator for Quality Evaluation of Carbonated Beverages

Histone deacetylase 4‐dependent regulation of cortical synaptic plasticity and the higher cognitive function during adulthood

AbstractBackgroundIt is known that the primary sensory cortex contributes to the higher cognitive function, such as decision‐making. Still, a detailed synaptic mechanism explaining the relationship between sensory input and perceptual decision‐making remains elucidated. Previously, we demonstrated sensory deprivation restores critical‐period‐like synaptic plasticity to the barrel cortex in unilateral infraorbital injury (IO) mice.MethodTherefore, we explored the relationship between adult primary synaptic input and perceptual decision‐making in adult IO mice using the head‐fixed texture discrimination test and brain slice patch‐clamp technique. We also explored a molecular mechanism underlying IO‐induced reactivation of thalamocortical (TC) synaptic plasticity in the barrel cortex using immunoblotting of HDAC4 and BDNF as well as AAV/shRNA‐mediating knockdown of HDAC4.ResultIO mice learned the spared TC input‐mediated perceptual decision‐making task more effectively than sham‐controls. This improvement in perceptual learning was intimately correlated with spared TC synaptic efficacy. In terms of a possible molecular mechanism for the IO‐induced reactivation of TC synaptic plasticity, histone deacetylase 4 (HDAC4) and brain‐derived neurotrophic factor (BDNF) expression was significantly reduced in layers 4 and 5 of the barrel cortex from PO7 to PO9 in IO mice compared with Sham‐controls. The IO‐induced potentiation of spared TC synaptic efficacy was nearly prevented by blockage of BDNF/TrkB signaling with cyclotraxin B. In addition, HDAC4 knockdown by injecting AAV5‐U6‐mHDAC4‐shRNA‐CMV‐EGFP to the S1 barrel cortex significantly increased BDNF expression and TC synaptic efficacy in the layer4 barrel cortex. Similarly, the application of HDAC4 inhibitor to the S1 barrel cortex via an osmotic pump effectively potentiated TC synaptic efficacy without alteration of excitation/inhibition balance, similar to IO mice.ConclusionThese results suggest that the reactivation of synaptic plasticity of primary TC input may regulate the higher cognitive function by modulating HDAC4/BDNF/TrKB signaling during adulthood.

Oral somatosensory alterations and salivary dysfunction in head and neck cancer patients

PurposePatients with head and neck cancer (HNC) are at high risk of malnutrition due to eating difficulties partly mediated by sensory alterations and salivary dysfunction. Clinical studies have mostly focused on taste and smell alterations, while changes in oral somatosensory perception are largely understudied. The study aimed to investigate oral somatosensory (tactile, texture, chemesthetic, and thermal) responses and salivary functions of HNC patients in comparison to healthy controls.MethodsA cross-sectional study was conducted using psychophysical tests in HNC patients (n = 30) and in age- and gender-matched control subjects (n = 30). The tests included measurements of point-pressure tactile sensitivity, whole-mouth chemesthetic stimulation, food texture discrimination, and temperature discrimination. Salivary functions, including hydration, saliva consistency, pH, volume, and buffering capacity, were also evaluated.ResultsHNC patients demonstrated significantly lower chemesthetic sensitivity (for medium and high concentrations, p < 0.05), thermal sensitivity (p = 0.038), and salivary functions (p = 0.001). There were indications of lower tactile sensitivity in the patient group (p = 0.101). Patients were also less sensitive to differences in food roughness (p = 0.003) and firmness (p = 0.025).ConclusionThis study provided evidence that sensory alterations in HNC patients extend beyond their taste and smell. The measurements demonstrated lower somatosensory responses, in part associated with their reduced salivary function. Oral somatosensory alterations and salivary dysfunction may consequently impart the eating experience of HNC patients. Thus, further investigations on food adjustments for this patient group seem warranted.

Dual discriminators generative adversarial networks for unsupervised infrared super-resolution

The breakthrough of sensor resolution has always been focused on the computer vision area, which is an urgent need when infrared sensor technology progresses slowly. We propose a novel unsupervised infrared super-resolution (UISR) method based on the photoelectric characteristics of infrared images. The UISR, without high-resolution ground truth, establishes a fully unpaired generative adversarial framework to enrich the image details and improve the visual perception of human eyes. In the process of SR, UISR corrects the abnormal pixel values, blurred edges, and mosaic effect by maintaining the image style uniformity and mining the texture distribution characteristics in the image domain. Specifically, the dual discriminator module is designed to enhance both global structures and local textures. The style discriminator captures the natural structure characteristics of large image patches to control the authenticity. In contrast, the texture discriminator captures the texture characteristics of small image patches to improve the detail generation performance. Besides, the content constraint module is designed to maintain the basic content of the image. Experiments show that, compared to the supervised algorithm, the proposed UISR presents more real SR infrared images and is simpler to generalize in higher scales beyond sensor resolution.

The Effect of Visual Movement Information on Texture Discrimination Performance and Movement Control in Active Touch

The Effect of Visual Movement Information on Texture Discrimination Performance and Movement Control in Active Touch