Search Results (69)

Postural control relies on the integration of visual, vestibular, and somatosensory inputs under biomechanical constraints. Conventional Romberg testing provides limited quantitative insight, particularly regarding directional control and sensory dependence. Wearable inertial measurement units (IMUs) enable portable, multidimensional assessment of postural sway. Thirty healthy adults (15 females, 15 males) completed a modified Romberg protocol with systematic manipulation of stance (normal, tandem), visual condition (eyes open, eyes closed), and arm position (arms at sides, arms forward), including both left and right leading foot during tandem stance. Whole-body kinematics were recorded using a full-body IMU system comprising 17 wireless sensors. Center-of-mass (CoM) trajectories were derived from a 23-segment biomechanical model, and linear, spatial, and nonlinear sway metrics were computed. Statistical analyses were conducted using repeated-measures ANOVA, with significance set at p < 0.05. Visual deprivation significantly increased sway path length, mean sway velocity, and sway area across all stance conditions (p < 0.001). Tandem stance elicited greater mediolateral sway than normal stance (p < 0.001). Romberg ratios exceeded unity for all metrics and were significantly higher in tandem stance (p < 0.01). Arm position effects were negligible in normal stance but showed significant Vision × Arm interactions during tandem stance (p < 0.05). Leading foot position had no significant main effects. Combining a modified Romberg protocol with full-body IMU-based CoM analysis enables sensitive characterization of sensory dependence and directional postural control. Tandem stance with visual deprivation increases mediolateral postural demands under reduced base-of-support conditions, providing a more challenging context for evaluating directional postural control. Full article

The use of virtual reality (VR) has made significant advancements, and now it is widely used across a range of applications. However, consumers’ capacity to fully enjoy VR experiences continues to be limited by a chronic problem known as cybersickness (CS). This study explores the feasibility of mitigating CS through geometric scene simplification combined with electroencephalography (EEG)-based monitoring. According to the sensory conflict theory, this issue is caused by the discrepancy between the visually induced self-motion (VIMS) through immersive displays and the real motion the vestibular system detects. While prior mitigation strategies have largely relied on hardware modifications or visual field restrictions, this paper introduces a novel framework that integrates geometric scene simplification with EEG-based neurophysiological activity to reduce VIMS during VR immersion. The proposed framework combines EEG neurophysiology, allowing us to monitor users’ brainwave activity and cognitive states during virtual immersion experience. The empirical evidence from our investigation shows a correlation between CS manifestation and neural activation in the parietal and temporal lobes. As an experiment with 15 subjects, statistical differences were significantly different with $P= 0.001$ and large effect size $\eta 2=0.28$, while preliminary trends suggest lower neural activation during simplified scenes. Notably, a decrease in neural activation corresponding to reduced optic flow (OF) suggests that VR environment simplification may help attenuate CS symptoms, providing preliminary support for the proposed strategy. Full article

Due to the highly individualised presentation of sport-related concussion (SRC), multi-domain assessments examining cognitive, migraine, vestibular, ocular, mood, sleep, and neck-related function have been suggested to assist clinicians with diagnosis, management, and rehabilitation. Normative data on such assessments for female, community players from countries outside the U.S. are needed. This study aimed to (i) describe normative data from community-level Ladies Gaelic Football players using a multi-domain assessment, and (ii) compare findings between adolescent and adult players. A total of 138 LGF players without SRC (101 adults, 37 adolescents) completed a multi-domain SRC assessment including Sport Concussion Assessment Tool 5th Edition, Concussion Clinical Profiles Screening, Vestibular/Ocular Motor Screening (VOMS), Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT^®), Patient Health Questionnaire-9, Generalised Anxiety Disorder-7, Pittsburgh Sleep Quality Index, Migraine Disability Assessment, and Neck Bournemouth Questionnaire, and neck dynamometry. Normative data were summarised using descriptive statistics, while differences in test scores between adolescents and adults were examined using parametric or non-parametric tests. While adolescents and adults scored similarly on most measures, adolescents scored worse on ImPACT^® visual–motor speed (d = 0.09) and reaction time (r = 0.52), SCAT5 concentration (V = 0.38), total modified Balance Error Scoring System (r = 0.42), and CP Screen vestibular profile (r = 0.38) (p < 0.05). This is the first study to describe and compare normative data for multidomain SRC assessments in adolescent and adult female, community athletes. Differences in some tests between adolescents and adults highlight the need for demographic-specific normative data when interpreting post-SRC assessment results. Full article

Background: Visual, vestibular, proprioceptive and cutaneous sensory information is important for postural control during quiet stance. When the reliability of one source of sensory information used to detect self-motion for postural control is reduced, there may be a reweighting of inputs within and/or across the remaining sensory systems determining self-motion for postural control. Muscle vibration, which creates an illusion of muscle stretch and a compensatory movement to shorten the vibrated muscle, may be used to determine the weighting of muscle spindle Ia proprioception in postural control. The objective of this study was to determine the effect of vision occlusion on triceps surae (TS) Ia proprioceptive weighting in postural control during quiet stance, utilizing an 80 Hz muscle vibration stimulus and a quantitative measure of the body’s anterior to posterior ground center of pressure (COP) response to TS muscle vibration in subjects standing freely. Methods: Subjects (N = 41; mean (standard deviation), 19.6(2.0) years) were examined as they stood with eyes open (EO) or eyes closed (EC). Ground COP was measured during quiet standing with and without bilateral vibration of the TS muscles. Results: The mean backward COP shift induced by TS vibration was significantly greater during the EC condition compared to EO (EC: −4.93(1.62) centimeters; EO: −3.21(1.33) centimeters; p = 6.85 × 10⁻¹⁰; Cohen’s d = 1.29). Thirty-seven subjects increased, and two subjects decreased their vibration-induced COP backward shift in the EC condition compared to EO, although the magnitude of the change varied. Conclusions: The results support the idea that, for most young subjects, there is an increased triceps surae Ia proprioceptive weighting for postural control during EC stance, possibly due to the need for postural control to depend more on non-visual feedback. Full article

Background/Objectives: Sports-related concussions can result in prolonged symptoms and deficiencies in stability and balance. Effective and standardized rehabilitation protocols remain limited. This case report introduces a novel balance training program using virtual reality and force plate technology to address persistent post-concussion symptoms. Methods: A 20-year-old National Collegiate Athletic Association (NCAA) Division I football player with a history of multiple concussions and balance-related symptoms completed a 10-week intervention. The program utilized a multi-axis force platform and immersive visual tasks to train vestibular, oculomotor, and proprioceptive systems. Each weekly session consisted of seven tasks progressing in difficulty, which were completed three times per session. Performance was measured by the percentage of time a digital cursor remained within task boundaries using the distribution of their center of mass. Symptom self-reports were also recorded. Results: Cumulative mean performance improved from 75.87% in the first session to 91.67% in the final session. All individual template scores increased, including those on the most complex template, which rose from 55.76% to 80.20%. The patient also reported reduced dizziness, disorientation, and improved functional balance across the 10-week period. Conclusions: This virtual-reality-based balance training program shows promise in resolving persistent post-concussion symptoms. Its objective measurement, engaging format, and ease of use suggest potential for broader application in concussion rehabilitation. Full article

Background/Objectives: Previous research has demonstrated that the perception of self-motion, as signaled by cervical proprioception, is significantly altered during neck muscle fatigue, while no similar effects are observed when self-motion is signaled by the vestibular system. Given that in typical natural movements, both proprioceptive and vestibular signals are activated simultaneously, this study sought to investigate whether the misperception of motion persists during neck muscle fatigue when both proprioceptive and vestibular stimulation are present. Methods: The study evaluated the gain of the perceptual responses to symmetric yaw sinusoidal head rotations on a stationary trunk during visual target localization tasks across different rotational frequencies. In addition, the final localization error of the visual target was assessed following asymmetric sinusoidal head rotations with differing half-cycle velocities. Results: The findings indicated that even with combined proprioceptive and vestibular stimulation, self-motion perceptual responses under neck muscle fatigue showed a pronounced reduction in the gain at low-frequency stimuli and a notable increase in localization error following asymmetric rotations. Notably, spatial localization error was observed to persist after asymmetric stimulation conditioning in the light. Additionally, even moderate levels of muscle fatigue were found to result in increased self-motion misperception. Conclusions: This study suggests that neck muscle fatigue can disrupt spatial orientation, even when the vestibular system is activated, so that slow movements are inaccurately perceived. This highlights the potential risks associated with neck muscle fatigue in daily activities that demand precise spatial perception. Full article

Pilot visual behavior safety assessment is a cross-disciplinary technology that analyzes pilots’ gaze behavior and neurocognitive responses. This paper proposes a multimodal analysis method for pilot visual behavior safety, specifically for cognitive state decoding. This method aims to achieve a quantitative and efficient assessment of pilots’ observational behavior. Addressing the subjective limitations of traditional methods, this paper proposes an observational behavior detection model that integrates facial images to achieve dynamic and quantitative analysis of observational behavior. It addresses the “Midas contact” problem of observational behavior by constructing a cognitive analysis method using multimodal signals. We propose a bidirectional long short-term memory (LSTM) network that matches physiological signal rhythmic features to address the problem of isolated features in multidimensional signals. This method captures the dynamic correlations between multiple physiological behaviors, such as prefrontal theta and chest-abdominal coordination, to decode the cognitive state of pilots’ observational behavior. Finally, the paper uses a decision-level fusion method based on an improved Dempster–Shafer (DS) evidence theory to provide a quantifiable detection strategy for aviation safety standards. This dual-dimensional quantitative assessment system of “visual behavior–neurophysiological cognition” reveals the dynamic correlations between visual behavior and cognitive state among pilots of varying experience. This method can provide a new paradigm for pilot neuroergonomics training and early warning of vestibular-visual integration disorders. Full article

The static orientation of the eyes during visual fixation is determined by the simultaneous operation of multiple equilibria. This phenomenon is collectively referred to as poly-equilibrium, which involves multiple systems that work together to cancel each other out and establish gaze direction. While other systems, such as audio- and cervico-ocular systems, may also contribute to gaze direction, this review focuses primarily on the commands issued by the vestibulo- and visuo-oculomotor systems that determine gaze direction, as they play a key role in the poly-equilibrium process. From the visual and vestibular activities accompanying the appearance of an object in the central visual field to the recruitment of premotor neurons responsible for the generation of slow and saccadic eye movements, a delicate balance is maintained. As long as the recruited channels convey commands that counterbalance each other, no movement is initiated. This alternative viewpoint leads to reconsidering the nature of saccadic and pursuit eye movements. Rather than viewing them as the dynamic reduction in brain signals encoding kinematic parameters such as position or velocity, they can be seen as the physical expression of intracerebral processes restoring balanced activities between sensorimotor channels whose recruitment leads to mutually opposed movements. Full article

Tai Chi provides an age-appropriate exercise to decrease fall risks in older adults. However, the exact mechanism underlying the benefits of Tai Chi practice remains an open question. Thus, this study examined how aging and Tai Chi practice impact adaptation to sensory and motor perturbations while standing. We hypothesized that older Tai Chi practitioners would exhibit a decreased reliance on visual processes as sensory and motor perturbations increased, relative to naive healthy older adults. Using rambling and trembling decompositions of the center of pressure (COP) and frequency-domain features, we examined changes in low (0–0.3 Hz), medium (0.3–1 Hz), and high (1–3 Hz) frequency components, reflecting contributions from the visual, vestibular/somatosensory, and proprioceptive systems, respectively, in healthy young adults (HYA), healthy older adults (HOA), and Tai Chi practicing older adults (TCOA). Our results revealed statistically significant condition-by-group interactions in high-frequency COP-x and rambling-x and COP-y components, medium-frequency COP-y components, and all low-frequency components in COP and trembling (p < 0.05). Further, a significant trial-by-group interaction in high-frequency rambling-y was observed (p < 0.05). These results indicate age and Tai-chi-related differences in modulation of sensory contributions to balance as perturbations increase, and with repeated practice, which merit further investigation. Full article

Background/Objective: Sensory integration (SI) involves the central processing of visual, vestibular, and somatosensory inputs. It plays a key role in regulating movements such as gait. However, aging may impair these systems and SI, altering the gait. Therefore, this systematic review and meta-analysis aim to examine the relationship between gait parameters and SI during standing in healthy older adults. Methods: A systematic literature search was conducted in the Web of Science, PubMed, MEDLINE, and PEDro databases. Correlation coefficients between gait speed, sway (area and/or velocity) while standing under different SI conditions, and quotients were extracted. The Romberg Quotient (RQ) and Proprioception Quotient (PQ) were used to assess reliance on visual and somatosensory systems, respectively. The studies were grouped by condition, quotient, and outcome measures for the meta-analysis. Results: Thirteen studies (n = 719, mean age 72.5 years) were included. There were significant associations between gait speed and sway area during standing with eyes open on a stable surface (r: −0.235, p < 0.001), eyes closed on a stable surface (ECS) (r: −0.201, p < 0.001), eyes open on a compliant surface (r: −0.198, p < 0.001), and eyes closed on a compliant surface (r: −0.186, p < 0.004). No associations were found between gait speed and sway velocity in each condition, RQ, and PQ (p > 0.486 for all), except for the ECS (r: −0.149, p: 0.01). Conclusions: This study indicated a partial link between gait speed and SI in older adults. Future research should focus on dynamic SI evaluation to better understand this association. Full article

Self-motion perception is a complex multisensory process that relies on the integration of various sensory signals, particularly visual and vestibular inputs, to construct stable and unified perceptions. It is essential for spatial navigation and effective interaction with the environment. This review systematically explores the mechanisms and computational principles underlying visual–vestibular integration in self-motion perception. We first outline the individual contributions of visual and vestibular cues and then introduce Bayesian inference as a normative framework for the quantitative modeling of multisensory integration. We also discuss multisensory recalibration as a critical mechanism in resolving conflicts between sensory inputs and maintaining perceptual stability. Using heading perception as a model system, we further describe the relevant visual and vestibular pathways involved in this process, as well as the brain regions involved. Finally, we discuss the neural mechanisms mediating visual–vestibular interactions through models of the Bayesian optimal integration and divisive normalization. Full article

Reduced gravity may impair motion perception accuracy, especially in the absence of visual cues, which could degrade astronauts’ driving performance. The lack of prior research makes simulating realistic motion perception for lunar rover driving particularly challenging. We created a simulation system to quantitatively simulate the motion characteristics of a lunar rover at different gravity levels, and a software program based on the spatial orientation observer model was developed for the comparison of motion perception differences between Earth’s and lunar gravity. In comparison to Earth’s gravity, the lunar rover in lunar gravity demonstrates the following differences: (1) The rover exhibits a greater propensity to float and slip, and slower acceleration and deceleration. (2) Dynamic tilt perception may be more complicated with single vestibular information, while static tilt perception is greatly reduced; the introduction of visual information can notably improve the perception accuracy. Simulation results demonstrate that motion characteristics and perception of lunar rover driving exhibit a more variable trend at different gravity levels. An intuitive mathematical formulation was proposed to explain the single vestibular results. Our findings provide a basis for further optimizing lunar rover driving motion simulation strategies. Full article

Background: Sounds that cause disturbances and perturbations to the vestibular (inner ear organ responses) and visual (acute oculomotor responses) systems can impact postural stability. The purpose of this study was to assess the impact of different types of sounds and noises on both static and dynamic PS. Methods: A total of 20 participants (12 females and 8 males; age: 21.35 ± 1.79 years; height: 170.7 ± 9.3 cm; mass: 66.725 ± 14.1 kg) were tested using the limits of stability (LOS) test on the BTrackS™ balance plate and a Timed Up and Go (TUG) test, when exposed to four different sounds and occupational noises [construction noise (CN), white noise (WN), sirens (SRs), and nature sounds (NAs)] in a randomized order with a no sounds (NSs) control performed initially (intensity range of 70–80 dB). The center of pressure (COP) total sway area (cm²) from the LOS and the time to completion of the TUG (seconds) were analyzed using a one-way repeated measures of analysis of variance at an alpha level of 0.05. Results: The observations demonstrated significant differences between the sounds and noises for the TUG (p < 0.001) but not for the LOS test (p = 0.406). Pairwise comparisons for the significant main effect for the TUG revealed that NSs demonstrated significantly slower time to completion compared to CN, WN, and SRs but not NAs. Conclusions: The findings suggest that the different sounds and noises did not impact static PS during the LOS test, which involved the voluntary excursion of the COP while maintaining the same base of support (BOS). However, during dynamic PS with a changing BOS while walking in the TUG, exposure to CN, SRs, and WN demonstrated a faster completion time than NSs or NAs. This finding may be attributed to the anxiety induced by the noise immersion and perception of sounds, compared to calm NAs and no sounds. The findings can aid in better understanding the impact of different occupational noises on PS and emphasize the need for better noise protection and reduction in loud work environments. Full article

Objective: Mental fatigue (MF) induced by prolonged cognitive tasks poses significant risks to postural stability, yet its effects on multi-sensory integration remain poorly understood. Method: This study investigated how MF alters sensory reweighting and postural control in 27 healthy young males. A 45 min incongruent Stroop task was employed to induce MF, validated via subjective Visual Analog Scale (VAS) scores and psychomotor vigilance tests. Postural stability was assessed under four sensory perturbation conditions (O-H: no interference; C-H: visual occlusion; O-S: proprioceptive perturbation; C-S: combined perturbations) using a Kistler force platform. Center of pressure (COP) signals were analyzed through time-domain metrics, sample entropy (SampEn), and Discrete Wavelet Transform (DWT) to quantify energy distributions across sensory-related frequency bands (visual: 0–0.1 Hz; vestibular: 0.1–0.39 Hz; cerebellar: 0.39–1.56 Hz; proprioceptive: 1.56–6.25 Hz). Results: MF significantly reduced proprioceptive energy contributions (p < 0.05) while increasing vestibular reliance under O-S conditions (p < 0.05). Time-domain metrics showed no significant changes in COP velocity or displacement, but SampEn decreased under closed-eye conditions (p < 0.001), indicating reduced postural adaptability. DWT analysis highlighted MF’s interaction with visual occlusion, altering cerebellar and proprioceptive energy dynamics (p < 0.01). Conclusion: These findings demonstrate that MF disrupts proprioceptive integration, prompting compensatory shifts toward vestibular and cerebellar inputs. The integration of nonlinear entropy and frequency-domain analyses advances methodological frameworks for fatigue research, offering insights into real-time sensor-based fatigue monitoring and balance rehabilitation strategies. This study underscores the hierarchical interplay of sensory systems under cognitive load and provides empirical evidence for optimizing interventions in high-risk occupational and clinical settings. Full article

Introduction: In patients refractory to vestibular rehabilitation in the management of bilateral vestibulopathy, the cochleo-vestibular implant has emerged as a viable alternative to enhance both audiovestibular function and quality of life. The main objective of this study is to pioneer the use of PET to assess cortical modifications in patients with cochleo-vestibular implants, aiming to evaluate the safety and functional improvements in individuals with bilateral vestibulopathy and severe to profound hearing loss. Methods: A phase I pilot clinical trial was conducted with participants who received a BIONIC-VEST CI24RE cochleo-vestibular implant, with pre- and post-implantation assessments conducted for twelve months. Audiovestibular testing and two PET studies with 18F-FDG under baseline conditions and with active stimulus to observe cortical-level differences were performed. Results: Five patients were included in the study, all of them treated with a cochleo-vestibular implant, none of whom presented postoperative adverse effects. Audiologically, the mean post-implant gain was 56.63 ± 14.53 dB and 50.40 ± 35.54% in terms of speech intelligibility. From a vestibular perspective, the most remarkable findings were observed at the graviceptive pathway level, where a mean posturographic improvement was observed, with a sensory organization test score of 24.20 ± 13.74 and a subjective visual vertical of 1.57° ± 0.79°, achieving, in most cases, results within the normal range (<2.3°) by the end of the follow-up. PET images confirmed that with the electrical stimulus active (implant ON), there was a supratentorial activation pattern, particularly in areas related to somatosensory integration, emotional regulation, and autonomic control. Conclusions: The BIONIC-VEST implant significantly improved the vestibular system, particularly the graviceptive pathway, enhancing balance and SVV and reducing fall risk. PET revealed distinct uptake patterns in baseline and activated conditions, highlighting a cortical-level response with the use of the cochleo-vestibular implant. Full article