Training proprioception with sound: effects of real-time auditory feedback on intermodal learning

Influence of age and feedback modality on the proprioceptive sense of force: insights from motor unit recordings

The primary purpose of our study was to compare the influence of feedback modality (visual vs. auditory) on force-reproduction accuracy in middle-aged and older adults. As a secondary objective, we investigated whether expected differences would be reflected in the neural drive sent to a hand muscle during the task. Participants (n = 42; 40-84 yr) performed a force-reproduction task with the first dorsal interosseus muscle at two target forces [5% and 20% of maximal voluntary contraction (MVC)]. Each trial involved a target phase that was guided by visual or auditory feedback and then a reproduction phase without feedback. The neural drive was characterized by measures of force steadiness and motor unit discharge characteristics during the target phase. Force-reproduction accuracy at the lower target force declined with increasing age and with visual feedback compared with auditory feedback. In contrast, there was no evidence of an effect of age or condition on force-reproduction accuracy at the moderate target force (20% MVC). Force steadiness was worse and motor unit coherence in the delta and beta bands was greater when the task was guided by auditory feedback at both target forces. These findings indicate that greater accuracy during the low-force task in the auditory-feedback condition was accompanied by a noisier control signal and differences in motor unit coherence in the delta and beta bands during the target phase.NEW & NOTEWORTHY The sense of force can be assessed with force-reproduction tasks, which typically involve visual feedback of the applied force during the target phase. Middle-aged and older adults improved force-reproduction accuracy when using auditory instead of visual feedback. This effect was accompanied by an increase in motor unit coherence in the beta band. This provides evidence for different sensorimotor processing of proprioceptive inputs when these sensory modalities are used to provide feedback of the applied force.

Auditory Cues and Feedback in the Serial Reaction Time Task: Evidence for Sequence Acquisition and Sensory Transfer

The present experiment used the Serial Reaction Time Task(SRTT) to investigate if auditory cueing or feedback in the form of spatially compatible tones benefited sequence learning similarly. Fifty-three neurotypical adults (18-35 years; 32 cis-females; 21 cis-males) were randomly assigned to three groups in which they practiced a visual SRTT: Group AC was supplemented with auditory cues; group AF received auditory feedback; group NS performed without sound. Retention and transfer tests (i.e., in the other two sensory conditions), and an explicit awareness test were conducted 48 h after practice. Changes in Total Sequence Time (TST), Total Error (TE), and acquired knowledge of the 10-item sequence order quantified sequence learning and were assessed using a two-way mixed ANOVA with repeated measures (p ≤ 0.05). A significant group-by-time interaction indicated only the AC group maintained their performance improvements when the sequence was perturbed. Overall, improvements in TST on day 1 and day 2 were consistent with all groups acquiring task-general and sequence-specific knowledge. TE outcomes suggested no speed-accuracy tradeoff. On Day 2, all groups performed best in the no-sound condition, indicating performance was maintained when sound cues or feedback were removed. All groups acquired equivalent implicit motor sequence knowledge regardless of sound condition.

Effect of Weight-Shifting Practice Using Auditory Feedback on Postural Control in Patients With Body Lateropulsion: A Single-Case Experimental Design

Body lateropulsion (BL) is a postural control disorder commonly associated with unilateral brainstem or cerebellar lesions. Patients with BL exhibit a tendency to lean toward one side and experience difficulty maintaining stable standing and walking. Although exercises focused on visual or somatosensory cues have been proposed, no standardized interventions have been established. Auditory feedback has emerged as a promising new approach, as it can complement visual and somatosensory inputs to improve balance. This single-case study investigated whether incorporating auditory feedback into standing weight-shifting exercises could enhance postural control in patients with BL. A man in his 60s with BL following a left cerebellar hemorrhage participated in an ABA (A: control phase, B: intervention phase) single-case study design. Each phase (A1, B, A2) lasted seven days, with weight-shifting exercises performed daily. During the A1 and A2 phases, the patient performed weight-shifting exercises without auditory feedback. In the B phase, auditory feedback was incorporated using a shoe-based load meter. Primary outcomes included center of pressure (COP) measures, COP velocity, perimeter area, and mediolateral COP position, recorded under eyes-open and eyes-closed conditions. Secondary outcomes included the Scale for the Assessment and Rating of Ataxia (SARA), the Berg Balance Scale (BBS), and subjective visual vertical (SVV). Compared to the A1 phase, the B phase demonstrated significant improvements in COP velocity, perimeter area, and mediolateral COP position. These improvements were maintained after auditory feedback was removed in the A2 phase. Although ataxia and balance ability improved over time, the changes did not exceed the minimal detectable change (MDC) or the minimal clinically important difference (MCID). The SVV deviation showed slight improvement but remained outside the normal range. Incorporating auditory feedback into weight-shifting exercises improved postural stability in a patient with BL. These findings suggest that auditory cues may facilitate proprioceptive reweighting and motor learning in postural control, independently of improvements in vestibular function or visual vertical perception. Further studies with larger sample sizes are needed to validate these results and elucidate the underlying mechanisms.

Online reach adjustments induced by real-time movement sonification

Movement sonification can improve motor control in both healthy subjects (e.g., learning or refining a sport skill) and those with sensorimotor deficits (e.g., stroke patients and deafferented individuals). It is not known whether improved motor control and learning from movement sonification are driven by feedback-based real-time ("online") trajectory adjustments, adjustments to internal models over multiple trials, or both. We searched for evidence of online trajectory adjustments (muscle twitches) in response to movement sonification feedback by comparing the kinematics and error of reaches made with online (i.e., real-time) and terminal sonification feedback. We found that reaches made with online feedback were significantly more jerky than reaches made with terminal feedback, indicating increased muscle twitching (i.e., online trajectory adjustment). Using a between-subject design, we found that online feedback was associated with improved motor learning of a reach path and target over terminal feedback; however, using a within-subjects design, we found that switching participants who had learned with online sonification feedback to terminal feedback was associated with a decrease in error. Thus, our results suggest that, with our task and sonification, movement sonification leads to online trajectory adjustments which improve internal models over multiple trials, but which themselves are not helpful online corrections.

Probiotic Potential of Lactobacillus and Enterococcus Strains Isolated From the Faecal Microbiota of Critically Endangered Hangul Deer (Cervus hanglu hanglu): Implications for Conservation Management

The mammalian gut microbiota plays a crucial role in promoting host health, and lactic acid bacteria (LAB) are commonly employed as probiotics for their beneficial effects. The Hangul deer (Cervus hanglu hanglu), a critically endangered red deer subspecies found in the Indian subcontinent, requires meticulous health management for its conservation. This pioneering study aimed to isolate, identify, and evaluate the in-vitro probiotic functional properties of LAB strains from the faeces of Hangul deer. A total of 27 LAB strains were isolated and identified using 16S rDNA gene sequencing, followed by comprehensive probiotic characterization and safety assessment. Remarkably, four species exhibited robust resistance and survivability against varying pH levels and bile salts, along with high aggregation and co-aggregation capacities. Notably, Lactobacillus acidophilus and Enterococcus mundtii strains displayed antibacterial activities. Safety assessment revealed the absence of hemolytic activity and virulence genes in all four strains. Antibiotic susceptibility testing showed that Lactobacillus acidophilus and Enterococcus casseliflavus were susceptible to all tested antibiotics, while Enterococcus mundtii exhibited resistance to clindamycin, and Enterococcus gallinarum exhibited resistance to erythromycin. These findings suggest that the isolated LAB strains possess advantageous probiotic characteristics and hold potential as dietary supplements for promoting the health and disease management of Hangul deer.

Adapted Training to Boost Upper Body Sensorimotor Control and Daily Living Functionality in Visually Impaired Baseball Players

Background and Objectives: Vision significantly contributes to postural control, balance, coordination, and body kinematics, thus deeply influencing everyday functionality. Sight-impaired subjects often show upper body anatomofunctional and kinetic chain alterations negatively impacting daily living efficiency and autonomy. The present study aimed to investigate and train, for the first time, upper body sensorimotor control in an Italian blind baseball team to boost global and segmental functionality while contemporarily prevent injuries. Materials and Methods: The whole team underwent a validated test battery using both quantitative traditional tools, such as goniometric active range of motion and muscular/functional tests, and an innovative biofeedback-based device, a Libra proprioceptive board. Consequently, a 6-week adapted training protocol was designed and leaded to improve sensorimotor control and, hence, counteract disability-related deficits and sport-specific overuse syndromes. Results: Statistically significant improvements were observed in all the investigated parameters. Noteworthy, an overall boost of global and segmental stability was detected through an orthostatic dynamic balance enhancement during the Y Balance test (p = 0.01) and trunk multiplanar control improvement on the Libra board (p = 0.01). Concurrently, the comparison of baseline vs. post-intervention outcomes revealed a consistent increase in upper body mobility (p < 0.05 for all the assessed districts), core recruitment (p = 0.01 for all the administered functional tests), and proprioceptive postural control (p = 0.01 for the Libra board validated test). Conclusions: Our findings suggest that a tailored sensorimotor training, conceived and led by an adapted physical activity kinesiologist, may effectively improve upper body functional prerequisites and global proprioceptive control, thus potentially promoting autonomy, quality of life, and physical activity/sport practice adherence in visually impaired individuals.

Does Music Therapy Improve Gait after Traumatic Brain Injury and Spinal Cord Injury? A Mini Systematic Review and Meta-Analysis

There is a growing body of research examining the potential benefits of music therapy-based auditory stimulation (MT) for individuals with movement disorders in improving gait performance. However, there is limited knowledge about the effects of MT on gait outcomes in individuals with traumatic brain injury (TBI) or spinal cord injury (SCI). A previous review of MT's impact on gait in TBI had limitations, and there are no studies on its effects on gait in SCI. In this study, we conducted a meta-analysis to more thoroughly evaluate the impact of MT on gait outcomes in individuals with TBI and SCI. We systematically searched through eight databases and found six studies on MT in TBI and four on SCI. Our meta-analysis showed that MT has positive medium effect improvements on spatiotemporal aspects of gait in individuals with TBI (Hedge's g: 0.52) and SCI (0.53). These findings suggest that MT could be a practical intervention for enhancing different aspects of gait in these populations, although the limited number and "fair" quality of the studies included in the meta-analysis may affect the generalizability of the outcomes. Further research is needed to fully understand the mechanisms by which MT may influence gait and determine the optimal parameters for its use.

Auditory Stimulation Improves Gait and Posture in Cerebral Palsy: A Systematic Review with Between- and Within-Group Meta-Analysis

The past decade has seen an increased interest in the implementation of auditory stimulation (AStim) for managing gait and postural deficits in people with cerebral palsy. Although existing reviews report beneficial effects of AStim on the spatiotemporal and kinematic parameters of gait, there are still numerous limitations that need to be addressed to correctly interpret these results. For instance, existing reviews have failed to characterize the effects of AStim by conducting separate between and within-group meta-analyses, these reviews have not evaluated the influence of AStim on postural outcomes, and nor have included several high-quality existing trials. In this study, we conducted between- and within-group meta-analyses to establish a state of evidence for the influence of AStim on gait and postural outcomes in people with cerebral palsy. We searched the literature according to PRISMA-P guidelines across 10 databases. Of 1414 records, 14 studies, including a total of 325 people with cerebral palsy, met the inclusion criterion. We report a significant enhancement in gait speed, stride length, cadence, and gross motor function (standing and walking) outcomes with AStim compared to conventional physiotherapy. The findings from this analysis reveal the beneficial influence of AStim on the spatiotemporal and kinematic parameters of gait and postural stability in people with cerebral palsy. Furthermore, we discuss the futurized implementation of smart wearables that can deliver person-centred AStim rehabilitation in people with cerebral palsy.

How does the modality of delivering force feedback influence the performance and learning of surgical suturing skills? We don’t know, but we better find out! A review

Background

Force feedback is a critical element for performing and learning surgical suturing skill. Force feedback is impoverished or not present at all in non-open surgery (i.e., in simulation, laparoscopic, and robotic-assisted surgery), but it can be augmented using different modalities. This rapid, systematic review examines how the modality of delivering force feedback influences the performance and learning of surgical suturing skills.

Methods

An electronic search was performed on PubMed/MEDLINE, Web of Science, and Embase databases to identify relevant articles. The results were synthesized using vote counting based on direction of effect.

Results

A total of nine studies of medium-to-low quality were included. The synthesis of results suggests that the visual modality could be more beneficial than the tactile and auditory modalities in improving force control and that auditory and tactile modalities could be more beneficial than the visual modality in improving suturing performance. Results are mixed and unclear with regards to how modality affects the reduction of force magnitude and unclear when unimodal was compared to multimodal feedback. The studies have a general low level of evidence.

Conclusion

The low number of studies with low methodological quality and low level of evidence (most were proof of concept) prevents us from drawing any meaningful conclusion and as such it is currently unknown whether and how force feedback modality influences surgical suturing skill. Speculatively, the visual modality may be more beneficial for improving the control of exerted force, while auditory and tactile modalities may be more effective in improving the overall suturing performance. We consider the issue of feedback modality to be highly relevant in this field, and we encourage future research to conduct further investigation integrating principles from learning psychology and neuroscience: identify feedback goal, context, and skill level and then design and compare feedback modalities accordingly.

Review of Real-Time Biomechanical Feedback Systems in Sport and Rehabilitation

Real-time biomechanical feedback (BMF) is a relatively new area of research. The potential of using advanced technology to improve motion skills in sport and accelerate physical rehabilitation has been demonstrated in a number of studies. This paper provides a literature review of BMF systems in sports and rehabilitation. Our motivation was to examine the history of the field to capture its evolution over time, particularly how technologies are used and implemented in BMF systems, and to identify the most recent studies showing novel solutions and remarkable implementations. We searched for papers in three research databases: Scopus, Web of Science, and PubMed. The initial search yielded 1167 unique papers. After a rigorous and challenging exclusion process, 144 papers were eventually included in this report. We focused on papers describing applications and systems that implement a complete real-time feedback loop, which must include the use of sensors, real-time processing, and concurrent feedback. A number of research questions were raised, and the papers were studied and evaluated accordingly. We identified different types of physical activities, sensors, modalities, actuators, communications, settings and end users. A subset of the included papers, showing the most perspectives, was reviewed in depth to highlight and present their innovative research approaches and techniques. Real-time BMF has great potential in many areas. In recent years, sensors have been the main focus of these studies, but new types of processing devices, methods, and algorithms, actuators, and communication technologies and protocols will be explored in more depth in the future. This paper presents a broad insight into the field of BMF.

Deliberate Practice and Motor Learning Principles to Underpin the Design of Training Interventions for Improving Lifting Movement in the Occupational Sector: A Perspective and a Pilot Study on the Role of Augmented Feedback

Spine posture during repetitive lifting is one of the main risk factors for low-back injuries in the occupational sector. It is thus critical to design appropriate intervention strategies for training workers to improve their posture, reducing load on the spine during lifting. The main approach to train safe lifting to workers has been educational; however, systematic reviews and meta-analyses have shown that this approach does not improve lifting movement nor reduces the risk of low back injury. One of the main limitations of this approach lies in the amount, quality and context of practice of the lifting movement. In this article, first we argue for integrating psychologically-grounded perspectives of practice design in the development of training interventions for safe lifting. Principles from deliberate practice and motor learning are combined and integrated. Given the complexity of lifting, a training intervention should occur in the workplace and invite workers to repeatedly practice/perform the lifting movement with the clear goal of improving their lifting-related body posture. Augmented feedback has a central role in creating the suitable condition for achieving such intervention. Second, we focus on spine bending as risk factor and present a pilot study examining the benefits and boundary conditions of different feedback modalities for reducing bending during lifting. The results showed how feedback modalities meet differently key requirements of deliberate practice conditions, i.e., feedback has to be informative, individualized and actionable. Following the proposed approach, psychology will gain an active role in the development of training interventions, contributing to finding solutions for a reduction of risk factors for workers.

Neurophysiological Changes Induced by Music-Supported Therapy for Recovering Upper Extremity Function after Stroke: A Case Series

Music-supported therapy (MST) follows the best practice principles of stroke rehabilitation and has been proven to instigate meaningful enhancements in motor recovery post-stroke. The existing literature has established that the efficacy and specificity of MST relies on the reinforcement of auditory-motor functional connectivity in related brain networks. However, to date, no study has attempted to evaluate the underlying cortical network nodes that are key to the efficacy of MST post-stroke. In this case series, we evaluated changes in connectivity within the auditory-motor network and changes in upper extremity function following a 3-week intensive piano training in two stroke survivors presenting different levels of motor impairment. Connectivity was assessed pre- and post-training in the α- and the β-bands within the auditory-motor network using magnetoencephalography while participants were passively listening to a standardized melody. Changes in manual dexterity, grip strength, movement coordination, and use of the upper extremity were also documented in both stroke survivors. After training, an increase in the clinical measures was accompanied by enhancements in connectivity between the auditory and motor network nodes for both the α- and the β-bands, especially in the affected hemisphere. These neurophysiological changes associated with the positive effects of post-stroke MST on motor outcomes delineate a path for a larger scale clinical trial.

Differential effects of visual versus auditory biofeedback training for voluntary postural sway

Augmented sensory biofeedback training is often used to improve postural control. Our previous study showed that continuous auditory biofeedback was more effective than continuous visual biofeedback to improve postural sway while standing. However, it has also been reported that both discrete visual and auditory biofeedback training, presented intermittently, improves bimanual task performance more than continuous visual biofeedback training. Therefore, this study aimed to investigate the relative effectiveness of discrete visual biofeedback versus discrete auditory biofeedback to improve postural control. Twenty-two healthy young adults were randomly assigned to either a visual or auditory biofeedback group. Participants were asked to shift their center of pressure (COP) by voluntary postural sway forward and backward in line with a hidden target, which moved in a sinusoidal manner and was displayed intermittently. Participants were asked to decrease the diameter of a visual circle (visual biofeedback) or the volume of a sound (auditory biofeedback) based on the distance between the COP and the target in the training session. The feedback and the target were given only when the target reached the inflection points of the sine curves. In addition, the perceptual magnitudes of visual and auditory biofeedback were equalized using Stevens’ power law. Results showed that the mean and standard deviation of the distance between COP and the target were reduced int the test session, removing the augmented sensory biofeedback, in both biofeedback training groups. However, the temporal domain of the performance improved in the test session in the auditory biofeedback training group, but not in the visual biofeedback training group. In conclusion, discrete auditory biofeedback training was more effective for the motor learning of voluntarily postural swaying compared to discrete visual biofeedback training, especially in the temporal domain.

Audio Feedback for Device-Supported Balance Training: Parameter Mapping and Influencing Factors

Recent studies suggest that real-time auditory feedback is an effective method to facilitate motor learning. The evaluation of the parameter mapping (sound-to-movement mapping) is a crucial, yet frequently neglected step in the development of audio feedback. We therefore conducted two experiments to evaluate audio parameters with target finding exercises designed for balance training. In the first experiment with ten participants, five different audio parameters were evaluated on the X-axis (mediolateral movement). Following that, in a larger experiment with twenty participants in a two-dimensional plane (mediolateral and anterior-posterior movement), a basic and synthetic audio model was compared to a more complex audio model with musical characteristics. Participants were able to orient themselves and find the targets with the audio models. In the one-dimensional condition of experiment one, percussion sounds and synthetic sound wavering were the overall most effective audio parameters. In experiment two, the synthetic model was more effective and better evaluated by the participants. In general, basic sounds were more helpful than complex (musical) sound models. Musical abilities and age were correlated with certain exercise scores. Audio feedback is a promising approach for balance training and should be evaluated with patients. Preliminary evaluation of the respective parameter mapping is highly advisable.

Virtual Reality Enhances Gait in Cerebral Palsy: A Training Dose-Response Meta-Analysis

Virtual-reality-based training can influence gait recovery in children with cerebral palsy. A consensus concerning its influence on spatiotemporal gait parameters and effective training dosage is still warranted. This study analyzes the influence of virtual-reality training (relevant training dosage) on gait recovery in children with cerebral palsy. A search was performed by two reviewers according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines on nine databases: PEDro, EBSCO, PubMed, Cochrane, Web of Science, EMBASE, ICI, Scopus, and PROQUEST. Of 989 records, 16 studies involving a total of 274 children with cerebral palsy met our inclusion criteria. Eighty-eight percent of the studies reported significant enhancements in gait performance after training with virtual reality. Meta-analyses revealed positive effects of virtual-reality training on gait velocity (Hedge's g = 0.68), stride length (0.30), cadence (0.66), and gross motor function measure (0.44). Subgroup analysis reported a training duration of 20–30 min per session, ≤4 times per week across ≥8 weeks to allow maximum enhancements in gait velocity. This study provides preliminary evidence for the beneficial influence of virtual-reality training in gait rehabilitation for children with cerebral palsy.

Effects of (music-based) rhythmic auditory cueing training on gait and posture post-stroke: A systematic review & dose-response meta-analysis

Gait dysfunctions are common post-stroke. Rhythmic auditory cueing has been widely used in gait rehabilitation for movement disorders. However, a consensus regarding its influence on gait and postural recovery post-stroke is still warranted. A systematic review and meta-analysis was performed to analyze the effects of auditory cueing on gait and postural stability post-stroke. Nine academic databases were searched according to PRISMA guidelines. The eligibility criteria for the studies were a) studies were randomized controlled trials or controlled clinical trials published in English, German, Hindi, Punjabi or Korean languages b) studies evaluated the effects of auditory cueing on spatiotemporal gait and/or postural stability parameters post-stroke c) studies scored ≥4 points on the PEDro scale. Out of 1,471 records, 38 studies involving 968 patients were included in this present review. The review and meta-analyses revealed beneficial effects of training with auditory cueing on gait and postural stability. A training dosage of 20–45 minutes session, for 3–5 times a week enhanced gait performance, dynamic postural stability i.e. velocity (Hedge’s g: 0.73), stride length (0.58), cadence (0.75) and timed-up and go test (−0.76). This review strongly recommends the incorporation of rhythmic auditory cueing based training in gait and postural rehabilitation, post-stroke.

Role of Sonification and Rhythmic Auditory Cueing for Enhancing Gait Associated Deficits Induced by Neurotoxic Cancer Therapies: A Perspective on Auditory Neuroprosthetics

Patients undergoing chemotherapy, radiotherapy, and immunotherapy experience neurotoxic changes in the central and peripheral nervous system. These neurotoxic changes adversely affect functioning in the sensory, motor, and cognitive domains. Thereby, considerably affecting autonomic activities like gait and posture. Recent evidence from a range of systematic reviews and meta-analyses have suggested the beneficial influence of music-based external auditory stimulations i.e., rhythmic auditory cueing and real-time auditory feedback (sonification) on gait and postural stability in population groups will balance disorders. This perspective explores the conjunct implications of auditory stimulations during cancer treatment to simultaneously reduce gait and posture related deficits. Underlying neurophysiological mechanisms by which auditory stimulations might influence motor performance have been discussed. Prompt recognition of this sensorimotor training strategy in future studies can have a widespread impact on patient care in all areas of oncology.