A comparison of vibrotactile patterns in an early warning system for obstacle detection using a haptic vest.

Technical devices can enhance safety by warning people of unrecognized obstacles, particularly in traffic, wilderness, and industrial settings. This study aims to identify the most effective vibrotactile stimuli for localization tasks by developing and evaluating various types of vibrotactile alerts presented through a tactile vest with visual patterns. The study design involved comparing the time and consistency of interpreting visual stimuli and subsequent tactile stimuli. The tactile stimuli included: a 'point' vibration on the left or right side of the back, a 'column' pattern of five vibrations on one side of the back, and a 'wave' pattern of vibrations running along the back from left to right or vice versa. The results indicated that reaction times to visual stimuli were significantly shorter than to vibration stimuli, suggesting that visual stimuli are suitable for alert systems with low cognitive load. The 'point' and 'column' patterns were recognized significantly faster and more clearly than the'wave' pattern. Consequently, the haptic vest was classified as a potentially effective low cognitive load device in localization performance. The findings could inform the design of early warning systems for obstacle detection in real traffic situations.

The Use of TheraBracelet Upper Extremity Vibrotactile Stimulation in a Child with Cerebral Palsy-A Case Report.

Background: TheraBracelet is peripheral vibrotactile stimulation applied to the affected upper extremity via a wristwatch-like wearable device during daily activities and therapy to improve upper limb function. The objective of this study was to examine feasibility of using TheraBracelet for a child with hemiplegic cerebral palsy. Methods: A nine-year-old male with cerebral palsy was provided with TheraBracelet to use during daily activities in the home and community settings for 1.5 years while receiving standard care physical/occupational therapy. Results: The child used TheraBracelet independently and consistently except during summer vacations and elbow-to-wrist orthotic use from growth spurt-related contracture. The use of TheraBracelet did not impede or prevent participation in daily activities. No study-related adverse events were reported by the therapist, child, or parent. Conclusion: Future research is warranted to investigate TheraBracelet as a propitious therapeutic device with focus on potential impact of use to improve the affected upper limb function in daily activities in children with hemiplegic cerebral palsy.

Optimality of multisensory integration while compensating for uncertain visual target information with artificial vibrotactile cues during reach planning.

BACKGROUND: Planning and executing movements requires the integration of different sensory modalities, such as vision and proprioception. However, neurological diseases like stroke can lead to full or partial loss of proprioception, resulting in impaired movements. Recent advances focused on providing additional sensory feedback to patients to compensate for the sensory loss, proving vibrotactile stimulation to be a viable option as it is inexpensive and easy to implement. Here, we test how such vibrotactile information can be integrated with visual signals to estimate the spatial location of a reach target. METHODS: We used a center-out reach paradigm with 31 healthy human participants to investigate how artificial vibrotactile stimulation can be integrated with visual-spatial cues indicating target location. Specifically, we provided multisite vibrotactile stimulation to the moving dominant arm using eccentric rotating mass (ERM) motors. As the integration of inputs across multiple sensory modalities becomes especially relevant when one of them is uncertain, we additionally modulated the reliability of visual cues. We then compared the weighing of vibrotactile and visual inputs as a function of visual uncertainty to predictions from the maximum likelihood estimation (MLE) framework to decide if participants achieve quasi-optimal integration. RESULTS: Our results show that participants could estimate target locations based on vibrotactile instructions. After short training, combined visual and vibrotactile cues led to higher hit rates and reduced reach errors when visual cues were uncertain. Additionally, we observed lower reaction times in trials with low visual uncertainty when vibrotactile stimulation was present. Using MLE predictions, we found that integration of vibrotactile and visual cues followed optimal integration when vibrotactile cues required the detection of one or two active motors. However, if estimating the location of a target required discriminating the intensities of two cues, integration violated MLE predictions. CONCLUSION: We conclude that participants can quickly learn to integrate visual and artificial vibrotactile information. Therefore, using additional vibrotactile stimulation may serve as a promising way to improve rehabilitation or the control of prosthetic devices by patients suffering loss of proprioception.

Transformation of neural coding for vibrotactile stimuli along the ascending somatosensory pathway.

In mammals, action potentials fired by rapidly adapting mechanosensitive afferents are known to reliably time lock to the cycles of a vibration. How and where along the ascending neuraxis is the peripheral afferent temporal code transformed into a rate code are currently not clear. Here, we probed the encoding of vibrotactile stimuli with electrophysiological recordings along major stages of the ascending somatosensory pathway in mice. We discovered the main transformation step was identified at the level of the thalamus, and parvalbumin-positive interneurons in thalamic reticular nucleus participate in sharpening frequency selectivity and in disrupting the precise spike timing. When frequency-specific microstimulation was applied within the brainstem, it generated frequency selectivity reminiscent of real vibration responses in the somatosensory cortex and could provide informative and robust signals for learning in behaving mice. Taken together, these findings could guide biomimetic stimulus strategies to activate specific nuclei along the ascending somatosensory pathway for neural prostheses.

Age related changes in skin sensitivity assessed with smartphone vibration testing.

The capacity to perceive tactile input at the fingertips, referred to as tactile sensitivity, is known to diminish with age due to regressive changes to mechanoreceptor density and morphology. Sensitivity is measured as perceptual responses to stimuli of varying intensity. Contrary to traditional sensitivity monitoring instruments, smartphones are uniquely suited for remote assessment and have shown to deliver highly calibrated stimuli along a broad spectrum of intensity, which may improve test reliability. The aim of this study was to evaluate a vibration-emitting smartphone application, the Vibratus App, as a mode of estimating tactile sensory thresholds in the aging adult. The peripheral nerve function of 40 neurologically healthy volunteers (ages 18-71) was measured using monofilaments, a 128-Hz tuning fork, the Vibratus App, and nerve conduction studies (NCS). Between group differences were analyzed to determine each measurement's sensitivity to age. Spearman correlation coefficients depicted the associative strength between hand-held measurements and sensory nerve action potential (SNAP) amplitude. Inter-rater reliability of traditional instruments and the software-operated smartphone were assessed by intraclass correlation coefficient (ICC2,k). Measurements taken with Vibratus App were significantly different between age groups (p < 0.001). The inter-rater reliability of monofilament, smartphone vibration, and tuning fork testing was moderate to good (ICC2,k = 0.65, 0.69, and 0.79, respectively). The findings of this study support further investigation of smartphones as sensitivity monitoring devices for at home monitoring of skin sensitivity.

Laryngeal Vibrotactile Stimulation Is Feasible, Acceptable To People With Unexplained Chronic Cough.

OBJECTIVES: Unexplained chronic cough (UCC) is common and has significant impacts on quality of life. Ongoing cough can sensitize the larynx, increasing the urge to cough and perpetuating the cycle of chronic cough. Vibrotactile stimulation (VTS) of the larynx is a noninvasive stimulation technique that can modulate laryngeal somatosensory and motor activity. Study objectives were to assess feasibility and acceptability of VTS use by people with UCC. Secondarily, changes in cough-related quality of life measures were assessed. METHODS: Adults with UCC recorded cough measures at baseline and after completing 2 weeks of daily VTS. Feasibility and acceptability were assessed through participant-reported device use and structured feedback. Cough-related quality of life measures were the Leicester Cough Questionnaire (LCQ) and the Newcastle Laryngeal Hypersensitivity Questionnaire (NLHQ). RESULTS: Nineteen adults participated, with mean age 67 years and cough duration 130 months. Notably, 93% of planned VTS sessions were logged, 94% of participants found the device comfortable to wear, 89% found it easy to operate and 79% would recommend it to others. Pre-post LCQ change achieved a minimal important difference (MID) (mean 1.3 [SD 2.4, p = 0.015]). NLHQ scores improved, but did not reach an MID. CONCLUSIONS: Laryngeal VTS use was feasible and acceptable for use by patients with UCC and was associated with a meaningful improvement in cough-related quality of life. Future studies will include VTS dose refinement and the inclusion of a comparison arm to further assess the potential for laryngeal VTS as a novel treatment modality for UCC. LEVEL OF EVIDENCE: 4 Laryngoscope, 2024.

Sensitivity to Vibrotactile Stimulation in the Hand and Wrist: Effects of Motion, Temporal Patterns, and Biological Sex.

OBJECTIVE: We investigated the impact of low-tempo, repetitive hand movements on vibrotactile sensitivity by employing various temporal and spatial patterns in the hand and wrist area. BACKGROUND: The investigation of a human's ability to perceive vibrotactile stimuli during dynamic hand movements remains understudied, despite the prevalence of slow to mild hand motions in applications such as hand navigation or gesture control using haptic gloves in Virtual Reality (VR) and Augmented Reality (AR). METHOD: We investigated vibrotactile sensitivity, analyzing the impact of various factors, including Motion (static and low-tempo repetitive hand movements), Temporal Patterns (Single or Double vibrations with varying onset times), Tactor Placements (hand and wrist), Spatial Patterns, and Biological Sex. RESULTS: Our study revealed that Motion significantly influences vibrotactile sensitivity in the hand and wrist areas, leading to reduced accuracy rates during dynamic conditions. Additionally, as the stimulus onset approached in Double vibrations, accuracy rates markedly decreased. Notably, Hand Placement resulted in significantly higher accuracy rates compared to the Wrist Placement. CONCLUSION: Our findings underscore the impact of motion in reducing vibrotactile sensitivity on the back of the hand and around the wrist. APPLICATION: This research has wide-ranging practical applications, particularly in the field of VR/AR experiences, rehabilitation programs, and accessibility solutions through the use of haptic gloves. Insights from our study can be harnessed to enhance the efficacy of haptic gloves in conveying vibrotactile cues within these contexts.

Vibrotactile Foot Device for Freezing of Gait in Parkinson's Disease: A Pilot Study.

BACKGROUND: Vibrotactile stimulation has been studied in its efficacy of reducing freezing of gait (FOG) in patients with Parkinson's disease (PD). However, the results are still controversial. We evaluated the efficacy of a newly developed vibrotactile foot device on freezing severity and gait measures in PD patients with FOG. OBJECTIVE: To evaluate the efficacy of vibrotactile foot device on PD patients with FOG. METHODS: Thirty-three PD patients with FOG were examined during their "off" medication state. The efficacy of the vibrotactile foot device was evaluated using a gait protocol comprising walking trials with vibrotactile stimulation "off" and "on." Walking trials were videotaped for the offline rating by two movement disorder specialists. The Opal inertial sensor unit (128 Hz; Mobility Lab; APDM Inc., Portland, OR, USA) was used for quantitative gait analysis. RESULTS: The results demonstrated 33.1% reduction in number of FOG episodes (P < 0.001) and 32.6% reduction of freezing episodes (P < 0.001). Quantitative gait analysis showed a significant increase in step length (P = 0.033). A moderate negative correlation was observed between the change of percent time frozen and age (r = -0.415, P = 0.016). 73% of participants reported minimal to substantial improvement in walking with this vibrating stimulation delivered by the vibrotactile foot device. CONCLUSIONS: The vibrotactile foot device is an efficient device that could significantly reduce freezing severity and provide gait regulation to patients with PD experiencing frequent freezing. It could potentially be used in the home environment for improving the quality of life.

Vibrotactile spatial acuity on the back.

Vibrotactile feedback can be built into clothing such as vests. This means that often vibrotactile information is presented to the back. It is known that the back has a relatively low spatial acuity. Spatial acuity varies across different limbs and sometimes with different locations on a limb. These known anisotropies suggest that there might be systematic variations in vibrotactile spatial acuity for different areas of the back and also for different orientations (i.e. horizontal vs. vertical). Here we systematically measured spatial acuity in four areas of the back for both horizontal and vertical orientations. The results show no significant differences in spatial acuity for the back areas that were tested. Spatial acuity was, however, higher in the horizontal direction than in the vertical direction by roughly a factor of two. This means that when designing vibrotactile displays for the back the tactor density can be lower in the vertical direction than in the horizontal direction and density should be constant for different areas of the back.

AiroTouch: enhancing telerobotic assembly through naturalistic haptic feedback of tool vibrations.

Teleoperation allows workers to safely control powerful construction machines; however, its primary reliance on visual feedback limits the operator's efficiency in situations with stiff contact or poor visibility, hindering its use for assembly of pre-fabricated building components. Reliable, economical, and easy-to-implement haptic feedback could fill this perception gap and facilitate the broader use of robots in construction and other application areas. Thus, we adapted widely available commercial audio equipment to create AiroTouch, a naturalistic haptic feedback system that measures the vibration experienced by each robot tool and enables the operator to feel a scaled version of this vibration in real time. Accurate haptic transmission was achieved by optimizing the positions of the system's off-the-shelf accelerometers and voice-coil actuators. A study was conducted to evaluate how adding this naturalistic type of vibrotactile feedback affects the operator during telerobotic assembly. Thirty participants used a bimanual dexterous teleoperation system (Intuitive da Vinci Si) to build a small rigid structure under three randomly ordered haptic feedback conditions: no vibrations, one-axis vibrations, and summed three-axis vibrations. The results show that users took advantage of both tested versions of the naturalistic haptic feedback after gaining some experience with the task, causing significantly lower vibrations and forces in the second trial. Subjective responses indicate that haptic feedback increased the realism of the interaction and reduced the perceived task duration, task difficulty, and fatigue. As hypothesized, higher haptic feedback gains were chosen by users with larger hands and for the smaller sensed vibrations in the one-axis condition. These results elucidate important details for effective implementation of naturalistic vibrotactile feedback and demonstrate that our accessible audio-based approach could enhance user performance and experience during telerobotic assembly in construction and other application domains.

[Rehabilitation in bilateral vestibulopathy: trends and perspectives]. / Reabilitatsiya patsientov s dvustoronnei vestibulopatiei: tendentsii i perspektivy razvitiya.

A review of the literature on rehabilitation methods for bilateral vestibulopathy is presented using RSCI, Scopus and PubMed databases. The principles and effectiveness of physical vestibular rehabilitation, vestibular implants, galvanic vestibular stimulation, and biofeedback-based sensory substitution and augmentation systems are described. The advantages and disadvantages of each method and perspectives for their improvement are presented.

Influence of Ambient Temperature on Autonomic Nerve Function and Peripheral Sensation from Moderate-Intensity Treadmill Exercise.

Objective: The main objective was to ascertain the acute responses in autonomic nervous activity and peripheral sensation induced by moderate-intensity treadmill exercise performed under different ambient temperatures. Methods: Twelve young healthy subjects underwent three sessions of moderate-intensity treadmill exercise (warming, 5 min and running, 25 min), on different days under 10°C, 20°C and 30°C room temperatures. Pre- and post-intervention, heart rate variability (HRV) and plantar vibrotactile perception threshold (VPT) were measured. Additionally, rate of perceived exertion (RPE) was recorded after intervention. Results: In comparison with the corresponding baseline values, after intervention, low frequency power (LF) and LF/high frequency power (HF) of HRV increased significantly and HF decreased significantly under the condition of 10°C only (p < .005). Following intervention, VPT increased significantly at the hallux for 31.5 Hz test frequency under 30°C and at the heel for 31.5 Hz test frequency under 10°C (both p < .05). In contrast, VPT decreased significantly at the hallux for 125 Hz test frequency under 10°C (p < .005). Exposure under the temperature of 20°C did not result in any significant change in VPT. After intervention, RPE under 30°C showed significantly higher values than those under 20°C (p < .01) and 10°C (p < .005) conditions with no difference between the latter two conditions. Conclusions: Treadmill exercise under 20°C ambient temperature did not exert any negative impacts on autonomic and peripheral nerve function and resulted in a perceived exertion of moderate intensity among the study participants. Therefore, an ambient temperature around 20°C might be recommended for the mentioned purpose.

The independent storage mechanisms of visual and vibrotactile working memory.

Whether information in working memory (WM) is stored in a domain-independent or domain-specific system is still the subject of intense debate. This study used the delayed match-to-sample paradigm, the dual-task paradigm, and the selective interference paradigm to investigate the mechanism of cross-modal storage in visual and vibrotactile WM. We postulated that WM may store cross-modal data from haptics and vision independently, and we proposed domain-specific WM storage. According to the findings, the WM can store cross-modal information from vision and haptics independently, and the storage of visual and tactile WM may be domain-specific. This study provides early support for the hypothesis that haptic and visuospatial sketchpads are dissociated. In addition, the current study provides evidence to elucidate the mechanisms by which WM stores and processes data from different modalities and content. The results also indicate that a cross-modal approach can broaden the cognitive processing bandwidth of WM.

On the Effect of Vibrotactile Stimulation in Essential Tremor.

(1) Background: Vibrotactile stimulation has been studied for tremor, but there is little evidence for Essential Tremor (ET). (2) Methods: This research employed a dataset from a previous study, with data collected from 18 individuals subjected to four vibratory stimuli. To characterise tremor changes before, during, and after stimuli, time and frequency domain features were estimated from the signals. Correlation and regression analyses verified the relationship between features and clinical tremor scores. (3) Results: Individuals responded differently to vibrotactile stimulation. The 250 Hz stimulus was the only one that reduced tremor amplitude after stimulation. Compared to the baseline, the 250 Hz and random frequency stimulation reduced tremor peak power. The clinical scores and amplitude-based features were highly correlated, yielding accurate regression models (mean squared error of 0.09). (4) Conclusions: The stimulation frequency of 250 Hz has the greatest potential to reduce tremors in ET. The accurate regression model and high correlation between estimated features and clinical scales suggest that prediction models can automatically evaluate and control stimulus-induced tremor. A limitation of this research is the relatively reduced sample size.

Evaluating User Perceptions of a Vibrotactile Feedback System in Trunk Stabilization Exercises: A Feasibility Study.

Low back pain patients often have deficits in trunk stability. For this reason, many patients receive physiotherapy treatment, which represents an enormous socio-economic burden. Training at home could reduce these costs. The problem here is the lack of correction of the exercise execution. Therefore, this feasibility study investigates the applicability of a vibrotactile-controlled feedback system for trunk stabilisation exercises. A sample of 13 healthy adults performed three trunk stabilisation exercises. Exercise performance was corrected by physiotherapists using vibrotactile feedback. The NASA TLX questionnaire was used to assess the practicability of the vibrotactile feedback. The NASA TLX questionnaire shows a very low global workload 40.2 [29.3; 46.5]. The quality of feedback perception was perceived as good by the subjects, varying between 69.2% (anterior hip) and 92.3% (lower back). 80.8% rated the feedback as helpful for their training. On the expert side, the results show a high rating of movement quality. The positive evaluations of the physiotherapists and the participants on using the vibrotactile feedback system indicate that such a system can reduce the trainees fear of independent training and support the users in their training. This could increase training adherence and long-term success.

Cross-Modal Sensory Boosting to Improve High-Frequency Hearing Loss: Device Development and Validation.

Background: High-frequency hearing loss is one of the most common problems in the aging population and with those who have a history of exposure to loud noises. This type of hearing loss can be frustrating and disabling, making it difficult to understand speech communication and interact effectively with the world. Objective: This study aimed to examine the impact of spatially unique haptic vibrations representing high-frequency phonemes on the self-perceived ability to understand conversations in everyday situations. Methods: To address high-frequency hearing loss, a multi-motor wristband was developed that uses machine learning to listen for specific high-frequency phonemes. The wristband vibrates in spatially unique locations to represent which phoneme was present in real time. A total of 16 participants with high-frequency hearing loss were recruited and asked to wear the wristband for 6 weeks. The degree of disability associated with hearing loss was measured weekly using the Abbreviated Profile of Hearing Aid Benefit (APHAB). Results: By the end of the 6-week study, the average APHAB benefit score across all participants reached 12.39 points, from a baseline of 40.32 to a final score of 27.93 (SD 13.11; N=16; P=.002, 2-tailed dependent t test). Those without hearing aids showed a 10.78-point larger improvement in average APHAB benefit score at 6 weeks than those with hearing aids (t14=2.14; P=.10, 2-tailed independent t test). The average benefit score across all participants for ease of communication was 15.44 (SD 13.88; N=16; P<.001, 2-tailed dependent t test). The average benefit score across all participants for background noise was 10.88 (SD 17.54; N=16; P=.03, 2-tailed dependent t test). The average benefit score across all participants for reverberation was 10.84 (SD 16.95; N=16; P=.02, 2-tailed dependent t test). Conclusions: These findings show that vibrotactile sensory substitution delivered by a wristband that produces spatially distinguishable vibrations in correspondence with high-frequency phonemes helps individuals with high-frequency hearing loss improve their perceived understanding of verbal communication. Vibrotactile feedback provides benefits whether or not a person wears hearing aids, albeit in slightly different ways. Finally, individuals with the greatest perceived difficulty understanding speech experienced the greatest amount of perceived benefit from vibrotactile feedback.

Transparent and Flexible Actuator Based on a Hybrid Dielectric Layer of Wavy Polymer and Dielectric Fluid Mixture.

Transparent and flexible vibrotactile actuators play an essential role in human-machine interaction applications by providing mechanical stimulations that can effectively convey haptic sensations. In the present study, we fabricated an electroactive, flexible, and transparent vibrotactile actuator with a dielectric layer including a dielectric elastomer and dielectric fluid mixture. The dielectric fluid mixture of propylene carbonate (PC) and acetyl tributyl citrate (ATBC) was injected to obtain a transparent dielectric layer. To further improve the haptic performance, different weight ratios of dielectric fluid (PC: ATBC) were injected. The fabricated vibrotactile actuators based on a transparent dielectric layer were investigated for their electrical and electromechanical behavior. The proposed actuators generate a large vibrational intensity (~2.5 g) in the range of 200-250 Hz. Hence, the proposed actuators open up a new class of vibrotactile actuators for possible use in various domains, including robotics, smart textiles, teleoperation, and the metaverse.

Comparison of the effects of rhythmic vibrotactile stimulations and rhythmic auditory stimulations on Parkinson's disease patients' gait variability: a pilot study.

INTRODUCTION: Parkinson's disease patients' gait is characterized by shorter step length, reduced gait velocity and deterioration of temporal organization of stride duration variability (modified Long Range Autocorrelations). The objective of this study was to compare effects of rhythmic auditory stimulations (RAS) and Rhythmic Vibrotactile Stimulations (RVS) on Parkinson's disease patients' gait. METHODS: Ten Parkinson's disease patients performed three walking conditions lasting 5-7 min each: control condition (CC), RAS condition and RVS condition. Inertial measurement units were used to assess spatiotemporal gait parameters. Stride duration variability was assessed in terms of magnitude using coefficient of variation and in terms of temporal organization (i.e., Long Range Autocorrelations computation) using the evenly spaced averaged Detrended Fluctuation Analysis (α-DFA exponent). RESULTS: Gait velocity was significantly higher during RAS condition than during CC (Cohen's d = 0.52) and similar to RVS condition (Cohen's d = 0.17). Cadence was significantly higher during RAS (Cohen's d = 0.77) and RVS (Cohens' d = 0.56) conditions than during CC. Concerning variability, no difference was found either for mean coefficient of variation or mean α-DFA between conditions. However, a great variability of individual results between the RAS and the RVS conditions is to be noted concerning α-DFA. CONCLUSIONS: RAS and RVS improved similarly PD patients' spatiotemporal gait parameters, without modifying stride duration variability in terms of magnitude and temporal organization at group level. Future studies should evaluate the relevant parameters for administering the right cueing type for the right patient. TRIAL REGISTRATION: ClinicalTrial.gov registration number NCT05790759, date of registration: 16/03/2023, retrospectively registered.

Virtual reality exposure with vibrotactile stimulation for the treatment of fear of flying: A pilot study.

BACKGROUND AND OBJECTIVES: Virtual reality (VR) interventions are becoming more prevalent in treating fear of flying (FoF). Since multisensory stimulation can enhance the sense of presence in a virtual environment, the present study compared virtual reality exposure with and without vibrotactile cues to determine its contribution to the realism of the virtual experience. METHODS: A repeated measures design was used. Thirty-one participants were exposed to two experimental conditions with a minimum of a one-week interval between them: one in which participants were exposed to the virtual environment with vibrotactile cues (smart chair, SC), and another in which participants were exposed to the virtual environment without vibrotactile cues (ordinary chair, OC). The administration order of both conditions was counterbalanced to avoid possible order effects. RESULTS: Participants felt higher levels of sense of presence when using the SC than the OC. However, the addition of vibrotactile stimulation partially influenced experienced anxiety. Some personality traits were also associated with participants' sense of presence and anxiety responses during the exposure. LIMITATIONS: The sample size was smaller than required. Moreover, only self-reported measures were used. Finally, a roller coaster instead of an airplane scenario was used for the exposure, which might not have been suitable enough for provoking anxiety in participants with FoF. CONCLUSIONS: Vibrotactile cues enhanced the sense of presence. However, the addition of vibrotactile stimulation did not have a consistent effect on anxiety experienced during exposure. Therefore, the benefits of incorporating vibrotactile cues in virtual reality environments for exposure therapy are not clear.

Evidence for vibration coding of sliding tactile textures in auditory cortex.

Introduction: Psychophysical studies suggest texture perception is mediated by spatial and vibration codes (duplex theory). Vibration coding, driven by relative motion between digit and stimulus, is involved in the perception of very fine gratings whereas coarse texture perception depends more on spatial coding, which does not require relative motion. Methods: We examined cortical activation, using functional Magnetic Resonance Imaging associated with fine and coarse tactile spatial gratings applied by sliding or touching (sliding vs. static contact) on the index finger pad. Results: We found regions, contralateral to the stimulated digit, in BA1 in S1, OP1, OP3, and OP4 in S2, and in auditory cortex, which were significantly more activated by sliding gratings but did not find this pattern in visual cortex. Regions in brain areas activated by vibrotactile stimuli (including auditory cortex) were also modulated by whether or not the gratings moved. In a control study we showed that this contrast persisted when the salience of the static condition was increased by using a double touch. Discussion: These findings suggest that vibration from sliding touch invokes multisensory cortical mechanisms in tactile processing of roughness. However, we did not find evidence of a separate visual region activated by static touch nor was there a dissociation between cortical response to fine vs. coarse gratings as might have been expected from duplex theory.