Search Results (62)

Ultrasound mid-air haptics (UMAH) can create touch sensations without physical contact, but it remains unclear whether they evoke steady-state somatosensory evoked potentials (SSSEPs) that could serve as objective markers relevant to evaluating haptic perception in UMAH interfaces. This study tested whether 20 Hz UMAH delivered with a commercial device at maximum available intensity elicited SSSEPs comparable to those produced by vibrotactile stimulation (VTS). Electroencephalography was recorded from 26 participants during three stimulation conditions: full-intensity VTS, subjectively matched-intensity VTS, and full-intensity UMAH. Signal-to-noise ratio (SNR) and power spectral density (PSD) at 20 Hz were analyzed over contralateral and ipsilateral somatosensory regions using linear mixed-effects models, with baseline estimates derived from no-stimulation intervals. Full-intensity VTS produced clear contralateral SSSEPs, and subjectively matched-intensity VTS yielded weaker but significant responses. In the present setup, UMAH did not yield a detectable 20 Hz SSSEP relative to baseline in either SNR or PSD. These findings support SSSEPs as sensitive markers of contact vibrotactile stimulation, but suggest that, with the present apparatus and analysis approach, they are not yet a robust objective measure for evaluating UMAH interface experience. Full article

Background: The perception of tactile locations is an important function of human’s somatosensory system during body movements and its interactions with the surroundings. Our previous study on the perception of locations found that the gamma-frequency band provides better decoding accuracy than all the lower frequencies on the legs. In the present study, we recorded electroencephalography (EEG) responses evoked by four vibrotactile stimulators placed on the arms of 18 human subjects. Methods: Human subjects were instructed to sit in a chair while somatosensory-evoked potentials were obtained using a 64-channel EEG. A linear classifier and an artificial neural network with 10 hidden-layer neurons were separately used to predict tactile locations based on EEG power obtained from various frequency bands. Results: We found that the beta (13–30 Hz) and high-gamma (50–100 Hz) bands can best predict the tactor locations on the arms. Interestingly, power information carried by the high-gamma band was uncorrelated to information contained in the lower frequency bands. Consequently, combining the beta and high-gamma bands significantly improved the prediction accuracy. Conclusions: Our findings prove that tactile location information can be decoded from EEG signals, which agrees with previous studies regarding the importance of the gamma band during tactile perception. Full article

Background/Objectives: Chronic ankle instability (CAI) is a common sequela of lateral ankle sprain and is characterized by recurrent episodes of giving way, sensorimotor deficits, impaired postural control, and diminished functional performance. While exercise-based rehabilitation, including neuromuscular training and proprioceptive exercises, remains the gold standard for managing CAI, patients often require additional support during daily activities. Orthotic interventions predominantly address mechanical instability, yet there is a clinical gap in providing integrated solutions that simultaneously offer mechanical support and sensory feedback to enhance postural control. This study aimed to investigate the effects of a semi-rigid ankle brace combined with vibro-stimulation on tactile sensation and center of pressure excursion in individuals with CAI. Methods: A randomized clinical trial was designed with two parallel groups and repeated measurements over time. Thirty adults (n = 15 per group) aged 18–35 years, who met the International Ankle Consortium criteria for CAI, were recruited. Participants in the experimental group received a semi-rigid ankle brace integrated with a wearable vibro-stimulation system, whereas those in the comparison group used the ankle brace alone. Outcome measures were collected at baseline, after 10 min, and after 2 and 4 weeks. Primary outcomes included Vibration Detection Rate and phase plane portraits assessed using a 128 Hz tuning fork and a force plate. Results: The ankle bracing plus vibration band group demonstrated significantly greater improvement at 4 weeks than the orthosis group in Vibration Detection Rate (F (3,26) = 31.93, p < 0.001, η² = 0.78). Also, the largest effect was observed for the anteroposterior phase plane portrait at 4 weeks (MD = −2.10 ± 0.42, 95% CI: −2.96 to −1.23, p < 0.001, d = −1.79). Conclusions: The findings suggest that combining a semi-rigid ankle bracing with vibro-stimulation provides additional benefits over the use of bracing alone in individuals with CAI. Full article

This is a narrative review that explores the development of non-implantable vestibular devices designed to address postural instability, particularly in aging populations and patients with vestibular hypofunction. It establishes that balance relies on complex sensory integration and that the functional decline of this system creates a significant medical need. Three principal technological strategies are examined: sensory substitution devices, galvanic vestibular stimulation (GVS), and immersive visual feedback systems. Sensory substitution devices, which convert balance data into auditory, tactile, or electrotactile cues, demonstrate significant promise. Examples like vibrotactile belts provide feedback that reduces postural sway, enhancing stability and patient confidence. Parallel to this, GVS—using electrical currents applied to the mastoids—emerges as a potent non-invasive method to modulate vestibular pathways, improving balance control and even inducing neuroplastic changes, especially with stochastic “noisy” signals. The most recently developed devices include augmented and virtual reality technologies that offer innovative visual feedback, creating enriched rehabilitation environments that accelerate recovery by promoting sensory reweighting and neural adaptation. This review concludes that while implantable prostheses are advancing, non-invasive devices offer versatile, affordable, and complementary solutions for balance restoration. The future success of non-invasive alternatives hinges on developing more sophisticated stimulation protocols that account for the complexity of natural movement and individual patient contexts, expanding therapeutic options for vestibular disorders. Full article

Virtual reality heritage experiences can be understood as multisensory interaction systems, yet how auditory, haptic, and gestural cues combine at the system level to shape electronic word-of-mouth (eWOM) intention remains insufficiently understood. Addressing this problem from a configurational systems perspective, this study applies fuzzy-set qualitative comparative analysis (fsQCA) to five auditable interaction cues (acoustic clarity, rhythmic drive, vibrotactile actuation level, gesture complexity, and compound gesture frequency) across a set of widely used VR cultural heritage applications. The results identify two sufficient system-level pathways to high eWOM intention: a rhythm-driven, low-burden pathway and a coordination-driven pathway characterized by clearer audio, stronger rhythmic structure, and tighter haptic and gestural action closure. Low eWOM intention is most consistently associated with weak cue interpretability, limited temporal drive, or unbalanced stimulation patterns, suggesting that isolated enhancement of single channels does not reliably translate into downstream sharing intentions. These findings reposition VR heritage design as a problem of configuring coherent multisensory interaction systems rather than maximizing individual stimuli. The study contributes a bounded, case-comparative account of how auditable cue bundles shape eWOM intention and offers system design guidance for resource-sensitive multisensory coordination in VR heritage applications. Full article

Background/Objectives: Bimanual movements with a 90° relative phase are typically unstable but can be facilitated by Lissajous visual feedback, which integrates the movements of the two hands into a single visual representation. We examined whether such visual integration leads to a unified sensorimotor representation by testing whether unilateral tactile stimulation suppresses motor output bilaterally during bimanual force production. Methods: Fifteen healthy participants produced rhythmic bimanual index finger flexion with a 90° relative phase under two feedback conditions: Lissajous feedback and individual visual feedback. In each trial, vibrotactile stimulation was applied to either hand or not applied at one of four phases of the force cycle. Force trajectory error and post-stimulus electromyographic (EMG) activity of the first dorsal interosseous muscle were analyzed. Results and Discussion: Lissajous feedback reduced force trajectory error compared with individual feedback. Tactile stimulation did not produce bilateral suppression of motor output. This indicates that visual integration of bimanual movements does not lead to global bilateral suppression of motor output induced by unilateral tactile stimulation. A significant reduction in post-stimulus EMG amplitude was observed only when the right hand was stimulated during one phase of the Lissajous feedback task. This suppression may reflect the unmasking of the tactile stimulus-induced inhibition within sensorimotor processes in the left hemisphere when visual feedback of the two hands is merged into a single representation. Full article

Tactile working memory limits the amount of information that can be processed through touch, with important implications for the design of haptic communication systems. Although visual and auditory working memory have been extensively investigated, tactile working memory, particularly for spatial and spatiotemporal sequences, remains less well understood. The present study examined tactile working memory capacity in two psychophysical experiments. Participants reproduced sequential vibrotactile stimuli delivered to the forearm via a 3 × 3 array of voice-coil actuators by entering responses through keypresses. Both experiments employed an adaptive 3-up/1-down staircase procedure, in which sequence length was adjusted according to response accuracy, and thresholds were estimated from reversal points. In Experiment 1 (Ordered Recall), participants reproduced both the spatial locations and the temporal order of stimulation, yielding a memory capacity threshold of approximately four items. In Experiment 2 (Unordered Recall), participants recalled only the set of stimulated locations without regard to order, resulting in a higher threshold of approximately five items. These results demonstrate that incorporating temporal sequencing demands into spatial recall substantially increases cognitive load and reduces effective tactile memory capacity. The findings clarify fundamental limits of tactile working memory and provide practical guidance for the development of haptic interfaces, wearable feedback systems, and sensory substitution technologies that must balance information complexity with human cognitive constraints. Full article

This research presents a new glove-shaped wearable device, designed to deliver torsional cues on the wrist as a tactile guidance tool. The device integrates four tactile modules that apply modulated shallow torque to the anatomical wrist articulation, providing torsional hints for both ulnar–radial deviation and flexion–extension degrees of freedom (DOF). The aim of this research is to evaluate whether this new type of stimulation can convey accurate directional cues on 2-DOF wrist movements, with the main target application as a guidance and support tool in virtual motor rehabilitation. Effectiveness was tested in virtual reality (VR) serious games designed to exercise wrist movements through a virtual navigation task. The glove-shaped haptic device was introduced to guide the user by directional cues provided through the shallow-torques approach. Results showed that the tactile sensations were effective in conveying accurate directional cues, reliably guiding subjects’ wrist movements on 2-DOF. This research highlights the potential of a compact, non-bulky glove-shaped device for providing clear directional cues at the wrist across 2-DOF. The shallow-torque approach, combining the natural interaction of force feedback with hardware simplicity and lightness closer to vibrotactile devices, has the potential of scalability on other body segments, and shows promise for applications in rehabilitation, postural guidance, and virtual interaction. Full article

Vibrotactile interfaces commonly encode information using changes in stimulus amplitude and frequency, yet it remains unclear how reliably these parameters can be distinguished when spatial cues are unavailable. The present study examined discrimination of vibrotactile signals that differed in amplitude, frequency, or both, with sequential stimulation delivered to a single location on the wrist. Vibrotactile stimuli were presented through a wearable actuator, and participants judged whether pairs of signals were the same or different. Discrimination performance was high when stimuli differed in amplitude, whereas signals differing only in frequency were difficult to distinguish and often produced performance near chance. Importantly, adding frequency differences to amplitude differences did not improve discrimination beyond amplitude differences alone. These findings indicate that, under non-spatial and sequential presentation conditions, amplitude provides a robust cue for vibrotactile signal discrimination, whereas frequency modulations on their own offer limited benefits for perceptual discrimination. The results highlight basic constraints on vibrotactile perception that are relevant for the design of wearable tactile interfaces and sensory substitution devices. Full article

This study aims to investigate the effects of a synchronous rhythmic–auditory stimulation (RAS) and vibrotactile wristband system on walking performance and subjective responses of older adults in a public transportation context. In the experiment, five older participants walked along an indoor corridor under two sequential conditions: (1) normal walking and (2) walking with the auditory–tactile synchronous cue. For each condition, walking speed and stride length were measured, followed by a five-point Likert questionnaire assessing perceptual comprehension and behavioural effectiveness. Neither the paired-sample t-test nor the Wilcoxon signed-rank test reached statistical significance. However, the synchronous cue condition exhibited a small increase in overall walking speed, and questionnaire results indicated high comprehensibility of the cueing device. These findings suggest that cross-modal synchronous prompting has potential benefits, and they warrant future studies with larger samples and refined stimulus designs to confirm its practical value. Full article

The lack of reliable sensory input from prosthetic limbs limits transfemoral amputees’ ability to perceive limb movement without visual monitoring. This study evaluated design parameters of a proposed forearm-based vibrotactile system in a pre-clinical, design-level perceptual evaluation, conveying prosthetic joint positions through patterned vibrations to provide non-invasive proprioceptive feedback. Healthy participants completed two experiments assessing detection of tactile cues from dual-actuator bands on the wrist and elbow representing assumed ankle and knee positions. The effects of temporal structuring (sequential vs. simultaneous stimulation), actuator configuration, amplitude and frequency settings, and signal duration on response accuracy were examined. Sequential vibrations produced significantly higher recognition accuracy than simultaneous presentation (72.4% vs. 42.7%, p < 0.001) in a variety of vibration signal parameter values. Actuator placement also influenced performance: simultaneous stimulation on opposite forearm sides yielded significantly lower accuracy (p < 0.001) than same-side configurations, whereas this directional effect was not significant for sequential presentation. Accuracy did not differ significantly between equal and unequal amplitude or frequency levels across actuators. Longer stimulus durations improved accuracy, increasing from 82.3% at 60 ms to 92.5% at 240 ms, though the results indicated a saturation point, suggesting an optimal temporal window. These findings inform the design of forearm-based sensory feedback systems for improved prosthetic limb control. Full article

Functional ankle instability (FAI) is a common consequence of lateral ankle sprains, characterized by impaired sensorimotor control. While orthoses and localized vibration have shown individual benefits for FAI, their combined application in a wearable device has not been previously investigated. This pilot randomized trial compared the effects of a vibrotactile foot orthosis (VFO) and a vibrotactile ankle orthosis (VAO) on joint position sense (JPS) and postural control in individuals with FAI. Sixteen participants were randomized to receive either a VFO or a VAO, both delivering 30–50 Hz pulsed vibration in 20 min sessions, three times a week, for two weeks. Outcome measures included joint position sense (JPS) error (°), center of pressure (COP) velocity (mm/s), the Star Excursion Balance Test (SEBT), and the Six-Meter Hop Test (SMHT), which were assessed pre-intervention, immediately post-intervention, and after two weeks of use. The analysis showed a statistically significant interaction between time and intervention group for JPS error (p = 0.02, η² = 0.42). Specifically, the VFO group improved JPS significantly more than VAO at two weeks follow-up (MD = −1.75°, p = 0.005, d = −1.68). Both groups significantly reduced in anteroposterior COP velocity after two weeks (VFO: MD = 1, p = 0.003, d = 1.47; VAO: MD = 1.39, p ˂ 0.001, d = 2.05) with no between-group differences. No changes were observed in the SEBT or SMHT. Plantar-based vibrotactile stimulation was more effective than ankle-based stimulation in enhancing proprioceptive acuity in individuals with FAI. Both interventions improved static postural stability, supporting the potential of integrated vibrotactile orthoses in FAI rehabilitation. No major practical issues were reported during the intervention. Two participants experienced minor discomfort related to the electronic housing bulk in the first week, which was resolved by week two. No further complaints regarding device weight or usability were observed. Full article

Epilepsy is increasingly conceptualized as a disorder of large-scale network instability, involving impairments in interhemispheric connectivity, prefrontal inhibitory control, and slow-frequency temporal processing. Rhythmic sensory stimulation—auditory, vibrotactile, or multisensory—can entrain neuronal oscillations and modulate attentional and sensorimotor networks, yet its mechanistic relevance to epileptic network physiology remains insufficiently explored. This conceptual and mechanistic article integrates empirical findings from entrainment research, prefrontal timing theories, multisensory integration, and network-based models of seizure dynamics and uses them to formulate a hypothesis-driven framework for multisensory exogenous rhythmic stimulation (ERS) in focal epilepsy. Rather than presenting a tested intervention, we propose a set of speculative mechanistic pathways through which low-frequency rhythmic cues might serve as an external temporal reference, engage fronto-parietal control systems, facilitate multisensory-driven sensorimotor coupling, and potentially modulate interhemispheric frontal coherence. These putative mechanisms are illustrated by exploratory neurophysiological observations, including a small pilot study reporting frontal coherence changes during mobile ERS exposure, but they have not yet been validated in controlled experimental settings. The framework does not imply therapeutic benefit; instead, it identifies theoretical pathways through which rhythmic sensory cues may transiently interact with epileptic networks. The proposed model is intended as a conceptual foundation for future neurophysiological validation, computational simulations, and early feasibility research in the emerging field of digital neuromodulation, rather than as evidence of clinical efficacy. This Hypothesis article formulates explicitly testable predictions regarding how multisensory ERS may transiently modulate candidate physiological markers of prefrontal network stability in focal epilepsy. Full article

Background: Although both rhythmic auditory stimulation (RAS) and vibrotactile feedback have been shown to yield beneficial effects in stroke rehabilitation, evidence regarding their combined application remains limited. This study investigates the effects of RAS gait training alone (RG) versus RAS combined with vibrotactile feedback (RAS-V) on balance and gait in individuals post-stroke. Methods: Twenty-two people with stroke were randomly assigned to either an RAS-V or an RG group. The RAS-V group performed RAS gait training combined with vibrotactile feedback while the RG group performed RAS gait training. Both groups participated in 30-min gait training sessions, 5 times a week for 4 weeks. Balance ability was assessed using the Berg Balance Scale (BBS) and Timed Up and Go test (TUG). Gait ability was evaluated using the G-Walk gait analyzer and the 10-m Walk Test (10 mWT), including gait cadence, velocity, and stride length. Results: Within-group comparisons showed significant improvements in BBS (p < 0.001) and TUG scores (p < 0.05) in both groups. The RAS-V group demonstrated significant post-intervention improvements in gait velocity, 10 mWT (p < 0.05), and gait cadence (p < 0.001). Between-group comparisons revealed that the RAS-V group achieved significantly greater improvements than the RG group in TUG, gait cadence, gait velocity, and 10 mWT (p < 0.05). Conclusions: RAS gait training with vibrotactile feedback enhances balance and gait ability more effectively than RAS gait training alone, suggesting additional benefits of incorporating vibrotactile feedback. Full article

Objectives: Sports-related concussion (SRC) is mostly associated with contact and combat sports. However, emerging evidence suggest that cyclists are also at risk of repeated concussion injury. Moreover, long-term neurophysiological outcomes in cycling cohorts remain underexplored. This novel study investigated the long-term effect of repetitive concussions in cyclists. Road, mountain biking (MTB), and BMX riders with a history of concussions and self-reported persistent symptoms were assess for neurophysiology and cognitive–motor performance compared to previously concussed cyclists with no ongoing symptoms. Both groups were compared to age-matched with controls. Methods: Using a cross-sectional between-group design, 25 cyclists with a history of concussions (15 symptomatic, 10 asymptomatic) and 20 controls completed symptom reporting, cognitive and balance assessments (SCAT5), sensorimotor testing using vibrotactile stimulation, and neurophysiological assessments via transcranial magnetic stimulation (TMS). Results: Symptomatic cyclists reported a higher number of concussions compared to asymptomatic cyclists (p = 0.041). Cognitive testing revealed large effects (d > 1.0), with impaired concentration in symptomatic cyclists compared to controls (p = 0.005). Motor assessments demonstrated large effects (d > 1.0), with slower tandem gait times (p < 0.001) and greater errors (p = 0.02) in the symptomatic group. Sensorimotor testing indicated slowed simple reaction times (p = 0.001) and poorer temporal order judgement (p = 0.038). TMS showed large effects (d > 1.0) in increased cortical inhibition in the symptomatic group, with prolong cortical silent periods (p < 0.05) and large effects (d > 1.0), and reduced short interval intracortical inhibition (p = 0.001) compared to asymptomatic cyclists and controls. Conclusions: Cyclists reporting persistent symptoms showed greater cortical inhibition and impaired cognitive–motor performance, consistent with findings in contact sport athletes. These results suggest that repeated concussions in cycling carry risk of chronic neurophysiological alterations. Cycling disciplines should consider more rigorous concussion identification protocols and stricter management strategies to mitigate persistent and long-term consequences. Full article