The Effects of Mirror Feedback during Target Directed Movements on Ipsilateral Corticospinal Excitability

Effects of a virtual reality-based mirror therapy system on upper extremity rehabilitation after stroke: a systematic review and meta-analysis of randomized controlled trials

Introduction

Virtual reality-based mirror therapy (VRMT) has recently attracted attention as a novel and promising approach for treating upper extremity dysfunction in patients with stroke. However, the clinical efficacy of VRMT has not been investigated.

Methods

This study aimed to conduct a meta-analysis to evaluate the effects of VRMT on upper extremity dysfunction in patients with stroke. We screened articles published between January 2010 and July 2022 in PubMed, Scopus, MEDLINE, and Cochrane Central Register of Controlled Trials. Our inclusion criteria focused on randomized controlled trials (RCTs) comparing VRMT groups with control groups (e.g., conventional mirror therapy, occupational therapy, physical therapy, or sham therapy). The outcome measures included the Fugl-Meyer assessment upper extremity test (FMA-UE), the box and block test (BBT), and the manual function test (MFT). Risk of bias was assessed using the Cochrane Collaboration risk-of-bias tool 2.0. We calculated the standardized mean differences (SMD) and 95% confidence intervals (95% CI). The experimental protocol was registered in the PROSPERO database (CRD42022345756).

Results

This study included five RCTs with 148 stroke patients. The meta-analysis showed statistical differences in the results of FMA-UE [SMD = 0.81, 95% CI (0.52, 1.10), p < 0.001], BBT [SMD = 0.48, 95% CI (0.16, 0.80), p = 0.003], and MFT [SMD = 0.72, 95% CI (0.05, 1.40), p = 0.04] between the VRMT and the control groups.

Discussion

VRMT may play a beneficial role in improving upper extremity dysfunction after stroke, especially when combined with conventional rehabilitation. However, there were differences in the type of VRMT, stage of disease, and severity of upper extremity dysfunction. Multiple reports of high-quality RCTs are needed to clarify the effects of VRMT.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42022345756.

Effectiveness of Repetitive Transcranial Magnetic Stimulation Combined with Visual Feedback Training in Improving Neuroplasticity and Lower Limb Function after Chronic Stroke: A Pilot Study

After a stroke, sustained gait impairment can restrict participation in the activities listed in the International Classification of Functioning, Disability, and Health model and cause poor quality of life. The present study investigated the effectiveness of repetitive transcranial magnetic stimulation (rTMS) and visual feedback training (VF) training in improving lower limb motor performance, gait, and corticospinal excitability in patients with chronic stroke. Thirty patients were randomized into three groups that received either rTMS or sham stimulation over the contralesional leg region accompanied by VF training groups in addition to the conventional rehabilitation group. All participants underwent intervention sessions three times per week for four weeks. Outcome measures included the motor-evoked potential (MEP) of the anterior tibialis muscle, Berg Balance Scale (BBS) scores, Timed Up and Go (TUG) test scores, and Fugl–Meyer Assessment of Lower Extremity scores. After the intervention, the rTMS and VF group had significantly improved in MEP latency (p = 0.011), TUG scores (p = 0.008), and BBS scores (p = 0.011). The sham rTMS and VF group had improved MEP latency (p = 0.027). The rTMS and VF training may enhance the cortical excitability and walking ability of individuals with chronic stroke. The potential benefits encourage a larger trial to determine the efficacy in stroke patients.

Effects of trunk stabilization exercises using laser pointer visual feedback in patients with chronic stroke: A randomized controlled study

BACKGROUND

Many previous studies have cited the importance of trunk stabilization exercises in patients with stroke. However, the evidence for optimal trunk stabilization exercises for patients with stroke is still lacking.

OBJECTIVE

To investigate the effects of laser pointer visual feedback in trunk stabilization exercises that are important for improving trunk dysfunction in patients with stroke.

METHODS

In total, 30 patients with chronic stroke were randomly assigned to experimental and control groups. The experimental group underwent a traditional stroke rehabilitation program and trunk stabilization exercises using laser pointer visual feedback. The control group underwent a traditional stroke rehabilitation program and trunk stabilization exercises without visual feedback. Pre- and postintervention results after 6 weeks were evaluated using the Berg Balance Scale, static and dynamic plantar pressure, 10-m walk test, and the Korean version of the Fall Efficacy Scale. The results were analyzed using a general linear repeated measurement model.

RESULTS

Both groups showed significant improvements in BBS scores, static plantar pressure, dynamic plantar pressure, 10 MWT, and K-FES scores after 6 weeks of intervention (P< 0.05). Compared to the control group, significant improvements were observed in the experimental group in the Berg Balance Scale scores, dynamic paretic posterior plantar pressure, 10-m walk test, and Korean version of the Fall Efficacy Scale scores (P< 0.025).

CONCLUSION

Our results demonstrated the effectiveness of visual feedback during trunk stabilization exercises for resolving trunk dysfunction in patients with stroke. Trunk stabilization exercises using laser pointer visual feedback have been found to be more effective in balance, walking, and fall efficacy in patients with stroke.

Acute Effect of Unilateral Muscle Training Supported with Visual Feedback on Contralateral Muscle Strength and Joint Position Sense

Aim: Unilateral exercise training is an effective and useful technique, especially in immobilization and neurological conditions, but the effect of unilateral muscle exercise training on muscle strength is modest. Therefore, the aim of this study is to detect the acute concomitant effect of mirror therapy and unilateral exercise training on muscle strength and joint position sense in healthy adults.Method: Thirty-one participants were randomly enrolled in two groups the mirror (n=16) and control groups (n=15). Hand grip (HG), pinch grip (PG) strengths, and joint position sense (JPS) of the wrist were assessed in both hands before and after a single exercise session which include 300 repetitive ball squeezing exercises by right (exercised) hand for all groups. The participants in the mirror group were asked to watch the mirror to see the reflection of their exercised hands, the control group only watched their exercised and unexercised hands without any visual feedback support during the exercise session. Repeated Measure ANOVA and Mixed ANOVA tests were performed to analyze in- and between-group differences.Results: The statistically significant differences were determined in unexercised hand HG and PG strength in the mirror group (F=10,105; p=0,006, ηp2=0,403; F=5,341; p=0,035; ηp2=0,263, respectively). However, any group×time interaction was found in JPS, HG, or PG tests (p&lt;0;05). Additionally, no difference was shown in JPS in-group comparisons (p&lt;0;05).Conclusion: The result of the study suggested that unilateral exercise training should apply concomitant with visual feedback. Further studies are needed to compare the effect of different sensory feedbacks on unilateral exercise training.

The Effects of Sit-to-Stand Training Combined with Real-Time Visual Feedback on Strength, Balance, Gait Ability, and Quality of Life in Patients with Stroke: A Randomized Controlled Trial

This study aimed to investigate the effects of lower limbs muscles' strength, balance, walking, and quality of life through sit-to-stand training combined with real-time visual feedback (RVF-STS group) in patients with stroke and to compare the effects of classic sit-to-stand training (C-STS group). Thirty patients with stroke were randomly divided into two groups. The RVF-STS group received sit-to-stand training combined with real-time visual feedback using a Wii Balance Board (n = 15), and the C-STS group received classic sit-to-stand training (n = 15). All participants received training for 20 min once a day, 5 days a week for 6 weeks, and both groups underwent general physical therapy for 30 min before training. Before and after the training, the muscle strength of the hip flexor, abductor, and knee extensor were measured, and the Wii Balance Board was used to perform the center of pressure test and Berg Balance Scale to evaluate static and dynamic balance. Additionally, the 10 m walking test and the Timed Up and Go test were performed to evaluate gait function. The Stroke-Specific Quality of Life was used to measure the quality of life. The results showed that the lower extremity muscle strength, balance ability, walking ability, and quality of life of the RVF-STS group significantly improved in comparison of the pre- and post-differences (p < 0.05), and it also showed significant differences between groups (p < 0.05). This study showed that sit-to-stand training combined with real-time visual feedback was effective at improving the muscle strength of the lower extremities, balance, gait, and quality of life in patients with stroke. Therefore, repeating sit-to-stand training combined with real-time visual feedback could be used as an effective treatment method for patients with stroke.

Methylphenidate decreases the EEG mu power in the right primary motor cortex in healthy adults during motor imagery and execution

This study investigated the effects of dopaminergic drugs on the EEG mu power during motor imagery, action observation, and execution. This is a double-blind, crossover study with a sample of 15 healthy adults under placebo vs. methylphenidate vs. risperidone conditions during motor imagery, action observation, and execution tasks. The participants had drug dosage adjustment based on body weight/dose (mg/kg). We also analyzed the mu band power by electroencephalography during the study steps. The main result is the interaction between the condition and task factors for the C3 and C4 electrodes, with decreasing EEG mu power in the methylphenidate when compared to risperidone (p ≤ 0.0083). Our results can indicate that the methylphenidate decreases the neurophysiological activity in the central cortical regions during the perceptual experience of tasks with or without body movement.

Reversal of Visual Feedback Modulates Somatosensory Plasticity

Reversed visual feedback during unimanual training increases transfer of skills to the opposite untrained hand and modulates plasticity in motor areas of the brain. However, it is unclear if unimanual training with reversed visual feedback also affects somatosensory areas. Here we manipulated visual input during unimanual training using left-right optical reversing spectacles and tested whether unimanual training with reversed vision modulates somatosensory cortical excitability to facilitate motor performance. Thirty participants practiced a unimanual ball-rotation task using the right hand with either left-right reversed vision (incongruent visual and somatosensory feedback) or direct vision (congruent feedback) of the moving hand. We estimated cortical excitability in primary somatosensory cortex (S1) before and after unimanual training by measuring somatosensory evoked potentials (SEPs). This was done by electrically stimulating the median nerve in the wrist while participants rested, and recording potentials over both hemispheres using electroencephalography. Performance of the ball-rotation task improved for both the right (trained) and left (untrained) hand after training across both direct and reversed vision conditions. Participants with direct vision of the right hand during training showed SEPs amplitudes increased bilaterally. In contrast, participants in the reversed visual condition showed attenuated SEPs following training. The results suggest that cortical suppression of S1 activity supports skilled motor performance after unimanual training with reversed vision, presumably by sensory gating of afferent signals from the movement. This finding provides insight into the mechanisms by which visual input interacts with the sensorimotor system and induces neuroplastic changes in S1 to support skilled motor performance.

Pre-Calibrated Visuo-Haptic Co-Location Improves Execution in Virtual Environments

A common approach to visio-haptic human-machine interfaces adopts a simpler design by shifting grounded force feedback away from the virtual scene. The alternative design favors intuitiveness by displaying visual and grounded force feedback at the same location (i.e. visuo-haptic co-location) but requires a sensibly more complex implementation and a tedious kinematic conception. The benefits of one approach over the other had not been fully investigated. Notably, (i) while users seem to better operate under co-located condition, it's not always the case. (ii) In the case of a desktop interface, the cost of a complex implementation to achieve co-location is challenged. We aim here to resolve (i) by conducting a user-centered experiment in which participants performed two generic tasks in co-located and delocated configurations, and comparing their performances. Additionally, we intend to fill the gap (ii) by testing a design without continuous head tracking, i.e., with static co-location. Participants' performances are assessed in terms of execution time, accuracy and force variation, while their subjective experiences are collected via a survey. Findings indicate that co-located configurations lead to shorter execution times, more accurate motions, better management of forces and are largely preferred by users, even when the co-location is pre-calibrated statically.

EEG Based Analysis of Cortical Activity during Mirror Visual Feedback Target-Directed Movement

In mirror visual feedback (MVF) based rehabilitation, the illusion of mirror reflection of volitional movement of non-paretic limb tends to have a modulatory effect on visuomotor and sensorimotor brain activations. This paper presents EEG based analysis of hemispheric activation asymmetry within the beta band (15-28 Hz) when MVF is combined with a target-directed hand motor task in a block design versus a similar task without any target requirements. MVF coupled with target-directed movement was associated with a decrease in hemispheric asymmetry in both preparation and execution phases of movement. These results emphasize the potential importance of incorporating visuomotor goals into the task to maximize the rehabilitation outcomes of MVF-based training activities.

Effect of Visual Condition on Performance of Balance-Related Tasks in Elite Dance Students

The purpose of this study was to investigate the effects of visual condition (low light, full light, and full light with mirror) on balance control and technical form during two technical dance movements in a group of elite collegiate dance students. Dancers demonstrated higher center of pressure velocity indicating lower control while performing a static dance task (parallel relevé retiré) and a dynamic dance task (fondu relevé en croix) under low light conditions than either lighted condition. Measures of Western ballet technique (pelvic obliquity, knee extension, and ankle plantar flexion) showed no decrement under low light conditions. No effect of concurrent mirror feedback was found on either center of pressure velocity or technical requirements of the dance tasks.

Cortical mapping of mirror visual feedback training for unilateral upper extremity: A functional near-infrared spectroscopy study

INTRODUCTION

Mirror therapy has been shown to be effective in promoting hemiplegic arm recovery in patients with stroke or unilateral cerebral palsy. This study aimed to explore the cortical mapping associated with mirror therapy in a group of healthy adults by using functional near-infrared spectroscopy.

METHODS

Fifteen right-handed healthy adults were recruited by means of convenience sampling. A 2 × 2 factorial design was used: movement complexity with two levels-task-based (T) and movement-based (M), and visual direction with two levels-mirror visual feedback task (MT) and covered mirror with normal visual feedback task (NoT) as the control, constituting four conditions, namely TMT, MMT, TNoT, and MNoT. The regions of interest were the sensorimotor cortex (SMC), the supplementary motor area (SMA), the superior parietal cortex (SPL), and the precuneus in both the contralateral and ipsilateral hemispheres.

RESULTS

Our findings showed that in the ipsilateral hemisphere, MT induced a higher activation in the SMA and SPL than NoT. With regard to the activation of the ipsilateral SMC, only one channel was found showing superior effects of MT compared with NoT. In addition, MT can strengthen the functional connectivity between the SMC and SMA. In the contralateral hemisphere, both movement complexity and visual direction showed significant main effects in the SMC, while only movement complexity showed a significant main effect in the SMA and SPL. The precuneus of both sides was deactivated and showed no significant difference among the four conditions.

CONCLUSIONS

Our experiment implies that the modest activation of ipsilateral SMC during MT is likely to be associated with the enhanced activity of ipsilateral SMA and that the precuneus may not be an essential component of the MT-related neural network.

Effects of mirror training on motor performance in healthy individuals: a systematic review and meta-analysis

Objective

Mirror training (MTr) is a rehabilitation technique for patients with neurological diseases. There is no consensus on its effects on motor function in healthy individuals. This systematic review and meta-analysis considers the effects of MTr on motor function in healthy individuals.

Design

This is a systematic review and meta-analysis.

Data sources

We searched six databases for studies assessing the effects of MTr on motor function in healthy individuals, published between January 1995 and December 2018. The Cochrane risk of bias was used to assess the quality of the studies. A meta-analysis was conducted with narrative synthesis.

Eligibility criteria for selecting studies

English-language randomised controlled trials reporting the behavioural results in healthy individuals were included.

Results

Fourteen randomised controlled trials involving 538 healthy individuals were eligible. Two short-term studies showed MTr was inferior to passive vision pattern (standardised mean difference 0.57 (95% CI 0.06 to 1.08), I²=0%, p=0.03). The methods varied and there is limited evidence supporting the effectiveness of MTr compared with three alternative training patterns, with insufficient evidence to support analyses of age, skill level or hand dominance.

Conclusion

The limited evidence that MTr affects motor performance in healthy individuals is weak and inconsistent among studies. It is unclear whether the effects of MTr on motor performance are more pronounced than the direct vision pattern, passive vision pattern or action observation. Further studies are needed to explore the short-term and long-term benefits of MTr and its effects on motor learning in healthy individuals.

PROSPERO registration number

CRD42019128881.

Effects of visual feedback training and visual targets on muscle activation, balancing, and walking ability in adults after hemiplegic stroke: a preliminary, randomized, controlled study

The aim of this randomized, controlled study was to investigate the effect of visual feedback through visual targets on muscle activity, balance, and gait in stroke patients. Patients were recruited from the inpatient unit of a rehabilitation hospital. Twenty-one patients who had experienced hemiplegic stroke were randomly assigned to two groups: an experimental group (visual feedback training with visual targets on gradual weight shifting), and a control group (visual feedback training on gradual weight shifting). All patients performed 30 minutes of comprehensive rehabilitation therapy followed by an additional 20 minutes of gradual weight shifting using visual feedback training with or without visual targets: three sets per day, five times a week, for 4 weeks. Significantly larger gains were identified in the experimental group compared to the control group due to gluteus medius muscle activation and the weight-bearing ability of the paretic side. Visual feedback training with visual targets during gradual weight bearing on the paretic side appears to improve the muscle activation and balancing abilities of hemiplegic stroke patients compared to visual feedback training alone.

The Effect of Movement Phase on the Contralaterally Coordinated Paired Associative Stimulation-Induced Excitability

Paired associative stimulation (PAS) has been shown to increase corticospinal excitability (CSE) providing a promising adjuvant therapeutic approach for stroke. Combining PAS with movement of the stimulated limb may further increase enhancement of CSE, however, individuals with moderate to severe stroke may not be able to engage in the necessary repetitive voluntary movements of the paretic limb. The objective of this study was to investigate the feasibility of contralaterally coordinated PAS (ccPAS) applied to the resting hand extensors during fast extension of the contralateral hand. A potential dependency of CSE modulation on the phase of the movement of the opposite hand was evaluated. Eleven participants each completed three session: PAS applied to the resting right hand during the preparation phase of the extension of the contralateral (left) hand; PAS applied during the execution phase of the left hand extension; and PAS applied with both hands at rest. Motor evoked potentials (MEPs) were evoked from the right extensor digitorum communis (EDC) and flexor digitorum superficialis (FDS) muscles prior and immediately after each session. PAS delivered during the muscle contraction of the left hand and PAS delivered at rest both increased the MEP amplitude in the right EDC. PAS delivered before the left hand movement onset led to a decrease in the MEP amplitude measured in the right EDC muscle. We conclude that PAS induced bidirectional changes in the amplitude of MEPs that were dependent on the phase of the movement of the opposite hand.

Parietal Activation Associated With Target-Directed Right Hand Movement Is Lateralized by Mirror Feedback to the Ipsilateral Hemisphere

Current research shows promise in restoring impaired hand function after stroke with the help of Mirror Visual Feedback (MVF), putatively by facilitating activation of sensorimotor areas of the brain ipsilateral to the moving limb. However, the MVF related clinical effects show variability across studies. MVF tasks that have been used place varying amounts of visuomotor demand on one’s ability to complete the task. Therefore, we ask here whether varying visuomotor demand during MVF may translate to differences in brain activation patterns. If so, we argue that this may provide a mechanistic explanation for variable clinical effects. To address this, we used functional magnetic resonance imaging (fMRI) to investigate the interaction of target directed movement and MVF on the activation of, and functional connectivity between, regions within the visuomotor network. In an event-related fMRI design, twenty healthy subjects performed finger flexion movements using their dominant right hand, with feedback presented in a virtual reality (VR) environment. Visual feedback was presented in real time VR as either veridical feedback with and without a target (VT+ and VT-, respectively), or MVF with and without a target (MT+ and MT-, respectively). fMRI contrasts revealed predominantly activation in the ipsilateral intraparietal sulcus for the main effect of MVF and bilateral superior parietal activation for the main effect of target. Importantly, we noted significant and robust activation lateralized to the ipsilateral parietal cortex alone in the MT+ contrast with respect to the other conditions. This suggests that combining MVF with targeted movements performed using the right hand may redirect enhanced bilateral parietal activation due to target presentation to the ipsilateral cortex. Moreover, functional connectivity analysis revealed that the interaction between the ipsilateral parietal lobe and the motor cortex was significantly greater during target-directed movements with mirror feedback compared to veridical feedback. These findings provide a normative basis to investigate the integrity of these networks in patient populations. Identification of the brain regions involved in target directed movement with MVF in stroke may have important implications for optimal delivery of MVF based therapy.

Do Robotics and Virtual Reality Add Real Progress to Mirror Therapy Rehabilitation? A Scoping Review

BACKGROUND

Mirror therapy has been used in rehabilitation for multiple indications since the 1990s. Current evidence supports some of these indications, particularly for cerebrovascular accidents in adults and cerebral palsy in children. Since 2000s, computerized or robotic mirror therapy has been developed and marketed.

OBJECTIVES

To map the extent, nature, and rationale of research activity in robotic or computerized mirror therapy and the type of evidence available for any indication. To investigate the relevance of conducting a systematic review and meta-analysis on these therapies.

METHOD

Systematic scoping review. Searches were conducted (up to May 2018) in the Cochrane Library, Google Scholar, IEEE Xplore, Medline, Physiotherapy Evidence Database, and PsycINFO databases. References from identified studies were examined.

RESULTS

In sum, 75 articles met the inclusion criteria. Most studies were publicly funded (57% of studies; n = 43), without disclosure of conflict of interest (59% of studies; n = 44). The main outcomes assessed were pain, satisfaction on the device, and body function and activity, mainly for stroke and amputees patients and healthy participants. Most design studies were case reports (67% of studies; n = 50), with only 12 randomized controlled trials with 5 comparing standard mirror therapy versus virtual mirror therapy, 5 comparing second-generation mirror therapy versus conventional rehabilitation, and 2 comparing other interventions.

CONCLUSION

Much of the research on second-generation mirror therapy is of very low quality. Evidence-based rationale to conduct such studies is missing. It is not relevant to recommend investment by rehabilitation professionals and institutions in such devices.