Tactile Acuity Research Articles

The iSTOPP study: Protocol for a proof-of-concept randomised clinical trial of sensory discrimination training in people with persistent neck pain

BackgroundNeck pain can be associated with a reduction in tactile acuity that is thought to reflect disrupted sensory processing. Tactile acuity training may normalise sensory processing and improve symptoms. This proof-of-concept trial will assess the feasibility of a novel tactile acuity training method and whether this intervention improves tactile acuity in people with persistent neck pain. Methodsand analysis: In this two-arm randomised clinical proof-of-concept trial we will recruit participants with neck pain receiving usual care physiotherapy in a secondary outpatient healthcare setting. Thirty-six participants will be randomised 2:1 to receive four weeks of either tactile acuity training using the Imprint Tactile Acuity Device (iTAD) or a placebo intervention, in addition to usual care. The placebo intervention will consist of a de-activated TENS machine (iTENS) said to deliver a sub-threshold inhibitory therapy. Outcomes will be assessed at baseline, mid-treatment, and at 5-weeks and 2-months follow-up. The primary outcome tactile acuity will be evaluated using the two-point discrimination test and locognosia tests. Feasibility will be informed by recruitment and attrition rates, adherence, credibility of the interventions, treatment satisfaction and blinding. Pain intensity and anatomical spread will be analysed as secondary outcomes. The effect of iTAD training on tactile acuity will be assessed using a 2 (Group: iTAD vs. iTENS) x 4 (Time: baseline, mid-treatment, 5-week and 2-month outcome assessment) mixed ANOVA. Secondary outcomes including pain and pain spread, will be analysed with a focus on informing sample size calculations in future trials. Ethics and disseminationRisks associated with this study are minor. Usual care is not withheld, and participants consent to random allocation of either iTAD or iTENS. Potential benefits to participants include any benefit associated with the interventions and contributing to research that may assist people with chronic pain in the future. Trial results will be disseminated via academic journals and conference presentations. The study is approved by the Human Research Ethics Committee of Griffith University (2017/128).

Joint position sense, motor imagery and tactile acuity in lateral elbow tendinopathy: A cross-sectional study

BackgroundImpairments of sensorimotor function are evident in individuals with lateral elbow tendinopathy (LET), although understanding of the mechanisms for this is lacking. ObjectivesTo determine if motor imagery, tactile acuity and wrist joint position sense (JPS) are impaired in participants with unilateral LET compared to controls, whether deficits are localised to the affected side, and whether deficits relate to severity of pain. DesignCross-sectional study with control group. Methods14 participants with unilateral LET of 6 weeks or longer and 14 matched control participants were assessed bilaterally for motor imagery (left/right hand judgement task), tactile acuity (two-point discrimination test) and wrist JPS (reposition test for flexion and extension). Pain levels were measured using a numeric rating scale. ResultsSignificant differences in JPS were observed for wrist extension only, such that participants with LET adopted less extended postures with their affected side when compared to their unaffected side (MD = 2.97°; p = 0.01) and to the matched-affected side of controls (MD = 4.89°; p < 0.01). No differences in tactile acuity or motor imagery were observed. ConclusionAltered wrist extension JPS, but not motor imagery or tactile acuity, was found in the affected side of patients with unilateral LET when compared to non-injured side and asymptomatic controls.

Individual differences impacting skin deformation and tactile discrimination with compliant elastic surfaces.

Individual differences in tactile acuity are observed within and between age cohorts. Such differences in acuity may be attributed to various sources, including aspects of nervous system, skin mechanics, finger size, cognitive and behavioral factors, etc. This work considers individual differences, within a younger cohort of participants, in discriminating compliant surfaces. These participants exhibit a range of finger size and stiffness. Interestingly, both their finger size and stiffness well predict their discriminative performance, where softer/smaller fingers outperform stiffer/larger fingers. Stereo imaging captured biomechanical cues in the skin's deformation, including contact area and penetration depth, and their change rates. In those individuals with stiffer/larger fingers, who perceptually performed worse, we observed less distinguishable contact areas and eccentricities, compared to softer/smaller fingers. These particular cues well predicted individual differences observed in perceptual discrimination. In comparison, with two other cues, curvature and penetration depth, the imaging readily distinguished the compliant surfaces irrespective of finger stiffness/size, not aligned with discrimination. In conclusion, in passive touch, we find that individuals with softer/smaller fingers were better at discriminating compliances, and that certain skin deformation cues predict individual differences in perception.

Individual Performance in Compliance Discrimination is Constrained by Skin Mechanics but Improved under Active Control.

Tactile acuity differs between individuals, likely a function of several interrelated factors. The extent of the impact of skin mechanics on individual differences is unclear. Herein, we investigate if differences in skin elasticity between individuals impact their ability to distinguish compliant spheres near limits of discriminability. After characterizing hyperelastic material properties of their skin in compression, the participants were asked to discriminate spheres varying in elasticity and curvature, which generate non-distinct cutaneous cues. Simultaneous biomechanical measurements were used to dissociate the relative contributions from skin mechanics and volitional movements in modulating individuals' tactile sensitivity. The results indicate that, in passive touch, individuals with softer skin exhibit larger gross contact areas and higher perceptual acuity. In contrast, in active touch, where exploratory movements are behaviorally controlled, individuals with harder skin evoke relatively larger gross contact areas, which improve and compensate for deficits in their acuity as observed in passive touch. Indeed, these participants exhibit active control of their fingertip movements that improves their acuity, amidst the inherent constraints of their less elastic finger pad skin.

Investigating the Mechanisms of Graded Sensorimotor Precision Training in Adults With Chronic Nonspecific Low Back Pain: Protocol for a Causal Mediation Analysis of the RESOLVE Trial.

BackgroundChronic low back pain (CLBP) is a global health problem associated with an increasing burden on individuals, health care systems, and society. Common treatments for people with CLBP produce, on average, small short-term improvements in pain and function compared with minimal care. The RESOLVE trial randomly allocated 276 people with CLBP to a new complex treatment strategy, pain education integrated with graded sensorimotor precision training (RESOLVE), or a sham control. The RESOLVE treatment was developed within a theoretical framework to target possible treatment mechanisms associated with CLBP development and persistence.ObjectiveThis protocol describes the planned evaluation of these proposed treatment mechanisms. Improved understanding of the mechanisms underpinning the RESOLVE treatment may guide its refinement and implementation.MethodsWe will use causal mediation analysis to evaluate the proposed treatment mechanisms, including pain self-efficacy, back beliefs, pain catastrophizing, kinesiophobia, back perception, tactile acuity, and movement coordination. The primary outcomes are pain intensity and function at 18 weeks following allocation. Data were collected blind to allocation and hypotheses at baseline (mediators, outcomes, confounders), end of treatment (mediators), and at 18 weeks following allocation (outcomes). We will test the robustness of our findings by conducting planned sensitivity analyses.ResultsEthical approval was granted by the University of New South Wales Human Research Ethics Committee (HC15357). A total of 276 participants have been recruited from primary care practices and the community in Sydney, Australia.ConclusionsThe RESOLVE treatment constitutes a new paradigm for CLBP management with potentially wide-reaching implications. This mechanistic evaluation will provide evidence for the hypothesized treatment mechanisms and help explain why the treatment strategy did or did not have an effect on patient-reported outcomes. These results will help guide the treatment refinement and implementation.Trial RegistrationAustralian and New Zealand Clinical Trials Registry ACTRN12615000610538; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=368619&isReview=trueInternational Registered Report Identifier (IRRID)DERR1-10.2196/26053

Correlation between tactile acuity, pain intensity, and functional capacity in individuals with chronic neck pain.

The aim of this study was to verify the correlation between tactile acuity, intensity of pain at rest, and movement and functional capacity in individuals with chronic neck pain. This was a cross-sectional study composed of two groups: individuals with chronic neck pain and individuals without neck pain. Evaluations were performed using the Numerical Rating Pain Scale at rest and movement, Neck Disability Index, and two-point discrimination test. The final sample consisted of 100 volunteers, 50 in each group. The groups did not show significant differences (p>0.05) in personal characteristics. It was observed that volunteers with cervical pain presented alterations in tactile care, with a significant and clinical increase in the perceived distance (Median 6.66; 95%CI 6.29-7.02; Cohen's d 7.22; 95%CI 6.15-8.30), and yet, positive, moderate, and significant correlation between two-point discrimination test, intensity of pain at rest and movement, and neck disability index (r=0.778-0.789, p<0.05). Tactile acuity is associated with pain intensity at rest and movement and functional capacity in individuals with chronic neck pain.

Visual Capture of a Tactile Sensation is Influenced by Repeated, Structured Exposure of a Visual Stimulus in Virtual Reality

Phantom limb pain is commonly known as a neurological condition, where an amputee will continue to feel a limb that is no longer present in a painful fashion. Virtual mirror therapy (VMT) has been suggested as a method for alleviating phantom limb pain. The inclusion of tactile sensation in VMT has shown to be beneficial; however, delivering a tactile sensation to a phantom limb, without the use of invasive procedures, can be difficult. The current approach for transferring a tactile sensation to a phantom limb is called visual capture. The ability to establish visual capture has been demonstrated in VMT applications. However, there is little research into whether an established visual capture effect can be relocated to a more distal location for phantom limb pain management. This paper investigates whether a passive vibrotactile sensation can be moved to a distal location from its veridical location using a series of distally located lights presented in either a random or a structured fashion. Eight non-amputee participants were tasked with localising a static tactile sensation on a virtual arm. These vibrotactile sensations were presented simultaneously with a visual light stimulus, either co-located or located distally at three different locations. Findings show that a tactile sensation without a visual stimulus was difficult for participants to localise; however, when a visual stimulus was added, they were better able to locate the veridical tactile position. The structured group exhibited a larger range of tactile relocation responses than the random group. However, this result was unreliable, with the majority of the responses situated at the vibrotactile actuator. There was a significant difference between the random and structured group’s ability to retain a visual capture at the veridical vibrotactile location when the lights were located distally. The random group did not express a visual capture response when the lights were presented distally while the structured group did, suggesting the structured group developed a more robust association between the visual stimulus and the vibrotactile stimulus. Findings may be of use where increasing tactile acuity without significant alteration of a veridical location is a desired therapeutic outcome.

Effects of acute pain and strain of the periodontium due to orthodontic separation on the occlusal tactile acuity of healthy individuals

ObjectivesThe aim of this study was to assess whether pain and strain of the periodontal ligament (PDL), induced by orthodontic separation, alter the somatosensory ability to perceive small thicknesses between occluding teeth (occlusal tactile acuity, OTA).MethodsThe OTA was tested at baseline (T0), using 9 aluminum foils (range 8–72 μm), randomly placed between the molar teeth, and 1 sham test (without foil), asking the participants whether they felt the foil between their teeth. Afterwards, orthodontic separators were placed, and subjects were randomly assigned to one of the two experimental groups: Group Pain (GP: 18 males; 14 females mean age 25.22 ± 2.28 years) had separators removed after 24 h; Group Strain (GS: 14 males; 17 females, mean age 24.03 ± 3.06 years) had separators removed after 7 days. The OTA measurement was repeated in both groups immediately after orthodontic separators removal (T1). A within-group comparison (T1 vs T0) was performed for each testing thickness (ANOVA for repeated measurements, with Bonferroni correction for multiple testing) (p < 0.005).ResultsGP showed statistically significant reduction of the OTA at T1, as compared to T0, for the thicknesses 24 μm (p = 0.004) and 32 μm (p = 0.001). No significant reduction was observed in GS (all p > 0.005).ConclusionsAcute periodontal pain tends to disturb the tactile ability of the teeth, while strain of the PDL in absence of painful sensation determines a return to OTA baseline values.Clinical relevanceThe reduction of OTA might explain the uncomfortable occlusal sensation referred by patients during acute periodontal pain.

Toward an index of oral somatosensory acuity: Comparison of three measures in adults.

Somatosensory targets and feedback are instrumental in ensuring accurate speech production. Individuals differ in their ability to access and respond to somatosensory information, but there is no established standard for measuring somatosensory acuity. The primary objective of this study was to determine which of three measures of somatosensory acuity had the strongest association with change in production accuracy in a vowel learning task, while controlling for the better-studied covariate of auditory acuity. Three somatosensory tasks were administered to 20 female college students: an oral stereognosis task, a bite block task with auditory masking, and a novel phonetic awareness task. Individual scores from the tasks were compared to their performance on a speech learning task in which participants were trained to produce novel Mandarin vowels with visual biofeedback. Of the three tasks, only bite block adaptation with auditory masking was significantly associated with performance in the speech learning task. Participants with weaker somatosensory acuity tended to demonstrate larger increases in production accuracy over the course of training. The bite block adaptation task measures proprioceptive awareness rather than tactile acuity and assesses somatosensory knowledge implicitly, with limited metalinguistic demands. This small-scale study provides preliminary evidence that these characteristics may be desirable for the assessment of oral somatosensory acuity, at least in the context of vowel learning tasks. Well-normed somatosensory measures could be of clinical utility by informing diagnosis/prognosis and treatment planning.

Transcranial direct-current stimulation (tDCS) in the primary motor cortex and its effects on sensorimotor function: a quasi-experimental single-blind sham-controlled trial

The main aim was to assess the short-term effects of active-tDCS (a-tDCS) in the primary motor cortex (anodal stimulation-M1) on sensorimotor variables. These variables included discriminative sensation through the two-point discrimination (2-PD) test, tactile acuity threshold and pressure pain threshold (PPT), and electromyographic (EMG) activity compared with a sham-tDCS (s-tDCS) in healthy individuals. A total of 100 participants were included. Fifty of the participants received the a-tDCS application of 2 mA for 20 min, whereas the remaining fifty received the s-tDCS. The 2-PD and tactile acuity threshold in thenar eminence of the hand and in the dorsal part of the foot and also, PPT and EMG activity during maximal voluntary contraction in the biceps brachii and rectus femoris were assessed before and after the tDCS application. The a-tDCS intervention was not significantly superior to the s-tDCS in any variable. However, significant within-group pre- and post-intervention differences were found in the a-tDCS, such as the tactile acuity threshold in thenar eminence of the hand, with a small effect size (p = .012, d = 0.20) and in the PPT of the rectus femoris, also with a small effect size (p = .001, d = − 0.17). Regarding EMG activity, a trend towards greater activity was observed in participants with a-tDCS compared with s-tDCS, which showed a trend towards decreased EMG activity. In fact, although no differences were found between the groups, within-group differences were statistically significant in the biceps brachii pre- and postintervention (p = .023, d = − 0.16, and p = .002, d = 0.18, respectively), and also in the rectus femoris, only in the a-tDCS, with a small effect size (p = .011, d = − 0.14). This study showed no significant between-group differences in sensorimotor outcomes. A single session of tDCS in isolation appears to produce immediate effects in healthy participants on sensorimotor function; however, these effects were very small.

Tactile acuity of fingertips and hand representation size in human Area 3b and Area 1 of the primary somatosensory cortex

Intracortical mapping in monkeys revealed a full body map in all four cytoarchitectonic subdivisions of the contralateral primary somatosensory cortex (S1), as well as positive associations between spatio-tactile acuity performance of the fingers and their representation field size especially within cytoarchitectonic Area 3b and Area 1. Previous non-invasive investigations on these associations in humans assumed a monotonous decrease of representation field size from index finger to little finger although the field sizes are known to change in response to training or in disease. Recent developments improved noninvasive functional mapping of S1 by a) adding a cognitive task during repetitive stimulation to decrease habituation to the stimuli, b) smaller voxel size of fMRI-sequences, c) surface-based analysis accounting for cortical curvature, and d) increase of spatial specificity for fMRI data analysis by avoidance of smoothing, partial volume effects, and pial vein signals.We here applied repetitive pneumatic stimulation of digit 1 (D1; thumb) and digit 5 (D5; little finger) on both hands to investigate finger/hand representation maps in the complete S1, but also in cytoarchitectonic Areas 1, 2, 3a, and 3b separately, in 21 healthy volunteers using 3T fMRI. The distances between activation maxima of D1 and D5 were evaluated by two independent raters, blinded for performance parameters. The fingertip representations showed a somatotopy and were localized in the transition region between the crown and the anterior wall of the post central gyrus agreeing with Area 1 and 3b. Participants were comprehensively tested for tactile performance using von Freyhair filaments to determine cutaneous sensory thresholds (CST) as well as grating orientation thresholds (GOT) and two-point resolution (TPD) for spatio-tactile acuity testing. Motor performance was evaluated with pinch grip performance (Roeder test). We found bilateral associations of D1-D5 distance for GOT thresholds and partially also for TPD in Area 3b and in Area 1, but not if using the complete S1 mask. In conclusion, we here demonstrate that 3T fMRI is capable to map associations between spatio-tactile acuity and the fingertip representation in Area 3b and Area 1 in healthy participants.

Haptic Perception, Mechanics, and Material Technologies for Virtual Reality

AbstractEmerging virtual and augmented reality technologies can transform human activities in myriad domains, lending tangible, embodied form to digital data, services, and information. Haptic technologies will play a critical role in enabling human to touch and interact with the contents of these virtual environments. The immense variety of skilled manual tasks that humans perform in real environments are only possible through the coordination of touch sensation, perception, and movement that together comprise the haptic modality. Consequently, many research groups are vigorously investigating haptic technologies for virtual reality. A longstanding research goal in this area has been to create haptic interfaces that allow their users to touch and feel plausibly realistic virtual objects. In this progress report, the perspective on this unresolved research challenge is shared, guided by the observation that no technologies can even approximately match the capabilities of the human sense of touch. Factors that have it challenging to engineer haptic technologies for virtual reality, including the extraordinary spatial and temporal tactile acuity of the skin, and the complex interplay between continuum mechanics, haptic perception, and interaction are identified. The perspective on how these challenges may be overcome through convergent research on haptic perception, mechanics, electronics, and material technologies is presented.

Feeling Touched: Empathy Is Associated With Performance in a Tactile Acuity Task.

The concept of empathy describes our capacity to understand the emotions and intentions of others and to relate to our conspecifics. Numerous studies investigated empathy as a state as well as a stable personality trait. For example, recent studies in neuroscience suggest, among other brain areas such as the insula or the ACC, a role of the somatosensory cortices for empathy (e.g., when observing someone else being touched). Since the classic understanding of the primary somatosensory cortex is to represent touch on the body surface, we here aimed to test whether tactile performance is linked to the personality trait empathy. To test this, we examined the tactile acuity of 95 healthy participants (mean age 31 years) by using a two-point discrimination threshold task at the index fingers. Trait empathy was assessed by employing the interpersonal reactivity index (IRI), which measures self-reported empathy with four scales (empathic concern, perspective taking, fantasy, and personal distress). Results of regression analyses suggested the subscale empathic concern to be positively associated with performance in the tactile acuity task. We discuss this finding in the light of recent studies on empathy and consider possible implications of tactile training to enhance empathy.

The self-perceived body size in obesity: Evidence from the implicit representation of the hand.

To locate our body in the space, we rely on an implicit representation of body size and shape: the body model. Evidence about the implicit representation of bodily dimensions in obesity is rare. Nevertheless, it seems to suggest that such representation is not altered in obesity compared to healthy weight individuals. To probe further this hypothesis, we investigated the implicit representation of hand dimensions with a landmark localisation task, comparing individuals with obesity and healthy weight individuals. Furthermore, as body model distortions may be related to tactile acuity, the tactile acuity threshold was measured using a two-point discrimination task. In accordance with the previous evidence, we observed that healthy weight participants showed a significant underestimation of finger length and overestimation of hand width. Interestingly, comparable body model distortions were shown also in participants with obesity. No differences in tactile acuity emerged between the two groups; also, when considering the whole sample, as tactile acuity decreases hand width overestimation increases. Thus, obesity seems to have no effect on the characteristics of the body model relative to the hand. Accordingly, the physiological mechanisms supporting the development of the implicit representation of hand dimensions in the healthy weight population may be preserved in obesity.

Non-informative Visual Resolution of the Body Modulates Tactile Acuity

Non-informative Visual Resolution of the Body Modulates Tactile Acuity

Perception and liking of yogurts with different degrees of granularity in relation to ethnicity, preferred oral processing and lingual tactile acuity

Food perception and liking depend on both product properties and consumer characteristics. The aim of this study was to investigate the effect of ethnicity, preferred oral processing and lingual tactile acuity on the consumer perception and liking of yogurt. To achieve the aim, six yogurt samples were prepared, including a homogeneous yogurt, a yogurt manufactured with micro particles, and four samples with addition of flakes or cut grains in different concentrations into homogeneous yogurt. Adults (n = 152) including seventy-five Asian Chinese subjects and seventy-seven Caucasian Danish subjects rated their perception and liking of yogurts. Subjects' preferred oral processing were identified according to how they prefer to manipulate food in their mouth ('soft processing likers' and 'firm processing likers'), and their tactile acuity was assessed by von Frey filaments. A descriptive sensory analysis of the yogurt was conducted by a trained panel consisting of 10 assessors. Results showed that ethnicity had a considerable influence on the liking of yogurts. Chinese subjects liked both yogurts containing macro particles (grains or low level of flakes) and homogeneous yogurts with no added particles, whereas Danish subjects significantly decreased their liking of yogurts with addition of particles, either micro or macro. Subjects' preferred oral processing and oral tactile acuity had a less pronounced effect on the liking of yogurts. Differences in texture perception of yogurts were negligible. The present results highlight a significant cultural effect on consumer acceptability and thus underline the importance of conducting the cross-cultural sensory research to the yogurt market.

Effects of a movement control and tactile acuity training in patients with nonspecific chronic low back pain and control impairment \u2013 a randomised controlled pilot study

BackgroundNonspecific chronic low back pain (NSCLBP) is a heterogeneous condition that is associated with complex neuromuscular adaptations. Exercise is a widely administered treatment, but its effects are small to moderate. Tailoring patient-specific exercise treatments based on subgroup classification may improve patient outcomes.ObjectiveIn this randomised controlled pilot study, our objective was to compare the feasibility and possible effects of a specific sensorimotor treatment (SMT) with those of a general exercise (GE) programme on patients with NSCLBP and control impairment (CI).MethodsPatients with NSCLBP and CI were randomised into an SMT or a GE programme spanning 6 sessions each. The feasibility criteria included the study design, assessments, interventions and magnitudes of effects, and costs. Adverse events were documented. Primary (pain, physical function, and quality of life) and secondary outcomes were assessed three times: twice at baseline (t1a and t1b) to estimate parameter stability and once after the intervention (t2).ResultsTwo-hundred and twenty-seven patients were screened to include 34 participants with NSCLBP and CI. Both treatment programmes and the assessments seemed feasible because their durations and contents were perceived as adequate. The total cost per participant was €321. Two adverse events occurred (one not likely related to the SMT, one likely related to the GE intervention).The SMT showed a tendency for superior effects in terms of pain severity (SMT t1a 3.5, t2 1.1; GE t1a 3.0, t2 2.0), pain interference (SMT t1a 1.9, t2 0.4; GE t1a 1.5, t2 0.9), physical component of quality of life (SMT t1a 39, t2 46; GE t1a 45, t2 48), and movement control.ConclusionsThe SMT approach proposed in this study is feasible and should be tested thoroughly in future studies, possibly as an addition to GE. To ensure the detection of differences in pain severity between SMT and GE in patients with NSCLBP with 80% power, future studies should include 110 patients. If the current results are confirmed, SMT should be considered in interventions for patients with NSCLBP and CI.Trial registrationRegistered in the German Register for Clinical Trials (Trial registration date: November 11, 2016; Trial registration number: DRKS00011063; URL of trial registry record); retrospectively registered.

Untangling Complexities of Glial-Neuronal Communications: Astroglial Metabolic Cascades Orchestrate Tonic Inhibition in the Thalamus

In this issue of Neuron, Kwak etal. describe novel astroglial pathway for synthesis of GABA, which is subsequently released through plasmalemmal Best1 channels to control neuronal excitability and tactile acuity through tonic inhibition of thalamic neurons.

Test–retest reliability of the two-point discrimination test on the sole of the foot in people with multiple sclerosis

Background: Two-point discrimination (TPD) is an assessment of tactile acuity. People with multiple sclerosis (MS) can have reduced foot sole tactile acuity, which has been linked to impaired balance. Objective: To quantify the test–retest reliability of TPD on the sole of the foot in people with MS. Approach: 41 participants (32 females), with mean (SD) age of 60 (9) years, and Expanded Disability Status Scale of <7.5, had their TPD measured at the head of the first metatarsal and the heel on two occasions, 2–14 d apart. Mean systematic change, within-subjects SD, limits of agreement (LOA), coefficient of variation and the intraclass correlation coefficient (ICC) were quantified as point estimates (95% CI). Main results: Systematic learning effects were evident. The within-subjects SD at the metatarsal and the heel was 6.7 mm (5.5–8.6) and 8.3 mm (6.7–10.8), and the LOAs were 18.6 mm (15.2–24.) and 23.7 mm (18.7–30.1), respectively. ICCs for metatarsal and heel was 0.87 (0.76–0.93) and 0.90 (0.80–0.95), respectively, but these were likely inflated by sample heterogeneity. Significance: In people with MS, TPD on the sole of the foot has an adequate test–retest reliability for research purposes, but there is substantial measurement variability for individual patients.

Deficits of Tactile Passive Perception Acuity in Patients With Schizophrenia.

Background: Scarce literature has yet to characterize the tactile discrimination capability as well as the underlying mechanism of tactile deficits in psychotic disorder. In particular, very little is known regarding the tactile perception acuity in schizophrenia.Methods: A total of 131 clinically stable patients with schizophrenia (SCZ) and 79 healthy control (HC) volunteers were enrolled in the study. All the participants were tested on a tactile stimulus device which could quantify the tactile discrimination capability with right index finger scanned over the angles via the passive finger-movement apparatus. The MATRICS Consensus Cognitive Battery (MCCB) was adapted to assess the neurocognition of the participants. Correlation analysis and multivariate linear regression analysis were performed to investigate the relationship between tactile perception performance and neurocognitive function.Results: It was discovered that there existed a significant deficits in the tactile passive perception acuity (i.e., tactile angle discrimination threshold) in patients with schizophrenia compared with their healthy controls (F (3, 206) = 11.458, P = 0.001,partial η2 = 0.053). The MCCB total score and its six domains were significantly lower in SCZ patients than those in HCs (all p < 0.001). In the SCZ group, the composite score of the MCCB (r = −0.312, P < 0.001) and domains of neurocognition including speed of processing (r = −0.191, P = 0.031), attention/vigilance (r = −0.177, P = 0.047), working memory (r = −0.316, P < 0.001), verbal learning (r = − 0.332, P < 0.001), visual learning (r = −0.260, P = 0.004), and reasoning and problem solving (r = −0.209, P = 0.018) showed significant negative correlations with the tactile angle discrimination threshold. Multivariate linear regression analysis revealed that neurocognition impairment, especially the decline of working memory (B = −0.312, P < 0.001),underpin the tactile perception discrimination deficits in patients with SCZ.Conclusion: To the best of our knowledge, this is the first study to unravel the deficits of tactile passive perception acuity and its underlying neurocognition basis in patients with SCZ. This finding adds novel evidence to the subtle variation in haptic discrimination skills in schizophrenia which contributes to a more comprehensive understanding of the sensory profiles of this disorder.