Comparisons of three different modes of digital mirror therapy for post-stroke rehabilitation: Preliminary results of randomized controlled trial.

Objective: Technologically adapted mirror therapy shows promising results in improving motor function for stroke survivors. The treatment effects of a newly developed multi-mode stroke rehabilitation system offering multiple training modes in digital mirror therapy remain unknown. This study aimed to examine the effects of unilateral mirror visual feedback (MVF) with unimanual training (UM-UT), unilateral MVF with bimanual training (UM-BT), and bilateral MVF with bimanual training (BM-BT) on clinical outcomes in stroke survivors, compared to classical mirror therapy (CMT). Methods: Thirty-five participants were randomly assigned to one of four groups receiving fifteen 60-minute training sessions for 3-4 weeks. The Fugl-Meyer Assessment for Upper Extremity (FMA-UE), Chedoke Arm and Hand Activity Inventory (CAHAI), Revised Nottingham Sensory Assessment (rNSA), Motor Activity Log (MAL), and EQ-5D-5L were administered at pre- and post-intervention and at 1-month follow-up. Results: After intervention and follow-up, significant within-group treatment efficacies were found on most primary outcomes of the FMA-UE and CAHAI scores in all four groups. Significant within-group improvements in the secondary outcomes were found on the MAL and EQ-5D-5L index in the UM-BT group, and the rNSA tactile sensation and MAL quality of movement subscales in the BM-BT group. No significant between-group treatment efficacies were found. Conclusions: UM-UT, UM-BT, BM-BT, and CMT led to similar clinical effects on the FMA-UE and can be considered effective alternative interventions for post-stroke upper-limb motor rehabilitation. UM-BT and BM-BT showed within-group improvements in functional performance in the patients' affected upper limbs in real-life activities.

Through the looking-glass: Mirror feedback modulates temporal and spatial aspects of bimanual coordination.

Mirror therapy has become an effective and recommended intervention for a range of conditions affecting the upper limb (e.g. hemiparesis following stroke). However, little is known about how mirror feedback affects the control of bimanual movements (as performed during mirror therapy). In this study, in preparation for future clinical investigations, we examined the kinematics of bimanual circle drawing in unimpaired participants both with (Experiment 1) and without (Experiment 2) a visual template to guide movement. In both experiments, 15 unimpaired right-handed participants performed self-paced continuous bimanual circle-drawing movements with a mirror/symmetrical coordination pattern. For the mirror condition, vision was directed towards the mirror in order to monitor the reflected limb. In the no mirror condition, the direction of vision was unchanged, but the mirror was replaced with an opaque screen. Movements of both hands were recorded using motion capture apparatus. In both experiments, the most striking feature of movements was that the hand behind the mirror drifted spatially during the course of individual trials. Participants appeared to be largely unaware of this marked positional change of their unseen hand, which was most pronounced when a template to guide movement was visible (Experiment 1). Temporal asynchrony between the limbs was also affected by mirror feedback in both experiments; in the mirror condition, illusory vision of the unseen hand led to a relative phase lead for that limb. Our data highlight the remarkable impact that the introduction of a simple mirror can have on bimanual coordination. Modulation of spatial and temporal features is consistent with the mirror inducing a rapid and powerful visual illusion, the latter appearing to override proprioceptive signals.

Improving motor imagery through a mirror box for BCI users.

The aim of this study was to evaluate mirror visual feedback (MVF) as a training tool for brain-computer interface (BCI) users. This is because approximately 20-30% of subjects require more training to operate a BCI system using motor imagery. Electroencephalograms (EEGs) were recorded from 18 healthy subjects, using event-related desynchronization (ERD) to observe the responses during the movement or movement intention of the hand for the conditions of control, imagination, and the MVF with the mirror box. We constituted two groups: group 1: control, imagination, and MVF; group 2: control, MVF, and imagination. There were significant differences in imagination conditions between groups using MVF before or after imagination (right-hand, P = 0.0403; left-hand, P = 0.00939). The illusion of movement through MVF is not possible in all subjects, but even in those cases, we found an increase in imagination when the subject used the MVF previously. The increase in the r2s of imagination in the right and left hands suggests cross-learning. The increase in motor imagery recorded with EEG after MVF suggests that the mirror box made it easier to imagine movements. Our results provide evidence that the MVF could be used as a training tool to improve motor imagery.NEW & NOTEWORTHY The increase in motor imagery recorded with EEG after MVF (mirror visual feedback) suggests that the mirror box made it easier to imagine movements. Our results demonstrate that MVF could be used as a training tool to improve motor imagery.

The instant effect of embodiment via mirror visual feedback on electroencephalogram-based brain connectivity changes: A pilot study.

The therapeutic efficacy of mirror visual feedback (MVF) is attributed to the perception of embodiment. This study intends to investigate the instantaneous effect of embodiment on brain connectivity. Twelve healthy subjects were required to clench and open their non-dominant hands and keep the dominant hands still during two experimental sessions. In the first session, the dominant hand was covered and no MVF was applied, named the sham-MVF condition. Random vibrotactile stimulations were applied to the non-dominant hand with MVF in the subsequent session. Subjects were asked to pedal while having embodiment perception during motor tasks. As suggested by previous findings, trials of no vibration and continuous vibration were selected for this study, named the condition of MVF and vt-MVF. EEG signals were recorded and the alterations in brain connectivity were analyzed. The average node degrees of sham-MVF, MVF, and vt-MVF conditions were largely different in the alpha band (9.94, 11.19, and 17.37, respectively). Further analyses showed the MVF and vt-MVF had more nodes with a significantly large degree, which mainly occurred in the central and the visual stream involved regions. Results of network metrics showed a significant increment of local and global efficiency, and a reduction of characteristic path length for the vt-MVF condition in the alpha and beta bands compared to sham-MVF, and in the alpha band compared to MVF. Similar trends were found for MVF condition in the beta band compared to sham-MVF. Moreover, significant leftward asymmetry of global efficiency and rightward asymmetry of characteristic path length was reported in the vt-MVF condition in the beta band. These results indicated a positive impact of embodiment on network connectivity and neural communication efficiency, which reflected the potential mechanisms of MVF for new insight into neural modulation.

Effects of Unilateral Neuromuscular Electrical Stimulation with Illusionary Mirror Visual Feedback on the Contralateral Muscle: A Pilot Study.

We aim to examine the cross-education effects of unilateral muscle neuromuscular electrical stimulation (NMES) training combined with illusionary mirror visual feedback (MVF). Fifteen adults (NMES + MVF: 5; NMES: 5, Control: 5) completed this study. The experimental groups completed a 3-week NMES training on their dominant elbow flexor muscle. The NMES + MVF group had a mirror placed in the midsagittal plane between their upper arms, so a visual illusion was created in which their non-dominant arms appeared to be stimulated. Baseline and post-training measurements included both arms' isometric strength, voluntary activation level, and resting twitch. Cross-education effects were not observed from all dependent variables. For the unilateral muscle, both experimental groups showed greater strength increases when compared to the control (isometric strength % changes: NMES + MVF vs. NMES vs. Control = 6.31 ± 4.56% vs. 4.72 ± 8.97% vs. -4.04 ± 3.85%, p < 0.05). Throughout the training, even with the maximally tolerated NMES, the NMES + MVF group had greater perceived exertion and discomfort than the NMES. Additionally, the NMES-evoked force increased throughout the training for both groups. Our data does not support that NMES combined with or without MVF induces cross-education. However, the stimulated muscle becomes more responsive to the NMES and can become stronger following the training.

Cortical sources of electroencephalographic alpha rhythms related to the anticipation and experience of mirror visual feedback-induced illusion of finger movements.

Mirror visual feedback (MVF) technique consists in placing a mirror in a person's body midline to induce the illusion of bilateral synchronous movements of the limbs during actual unilateral movements. A recent electroencephalographical (EEG) study demonstrated that MVF-induced illusion was related to the event-related desynchronization (ERD) of alpha (8-12 Hz) rhythms (cortical activation) at the central and parietal scalp electrodes ipsilateral to the unilateral right finger movements. In the present study, we re-analyzed those data to localize the cortical sources of alpha ERD during the anticipation and experience of the MVF-induced illusion of index finger movements. To this aim, the exact Low-Resolution Brain Electromagnetic Tomography freeware was used for the estimation of the cortical sources of the alpha ERD. Results showed that as compared to the condition without MVF, the MVF condition was characterized by greater (p < .01, uncorrected) alpha ERD sources in right frontopolar areas during the anticipation of the MVF-induced illusion of left movements. The MVF condition was also characterized by greater (p < .05, corrected) alpha ERD sources in right premotor, primary somatomotor, and posterior inferior parietal areas during both the anticipation and experience of that MVF-induced illusion. These findings suggest that the MVF-induced illusory experience of left finger movements may be due to dynamic changes in alpha ERD in associative, premotor, somatomotor, and visuomotor frontal-parietal areas located in the hemisphere contralateral to the mirrored motor acts.

Activation characteristics of motor cortex during mirror visual feedback based on electroencephalography / 中国康复理论与实践

ObjectiveTo explore the activation of motor cortex and brain lateralization of healthy male subjects during mirror visual feedback (MVF) of dominant and non-dominant hands. MethodsFrom March to September, 2021, 17 right-handed male subjects were recruited in Shenyang Sport University. The eegoTMmylab electroencephalography (EEG) system was applied to acquire the EEG and surface electromyography (sEMG) signals of digital extensor muscle during MVF. The subjects were completed unilateral finger stretching exercise, including left/right hand MVF and left/right hand visual feedback (VF). Each paradigm was repeated 80 trials, and the four paradigms were divided into two experiments, with one week between each experiment. The time-domain characteristics of sEMG signals and the time-frequency characteristics of α-band (8 to 13 Hz) and β-band (13 to 20 Hz) EEG signals which were closely related to motion were analyzed. Activation and asymmetry of motor cortex during MVF in dominant and nondominant hands were measured with event-related desynchronization/synchronization (ERD/ERS) and asymmetric index (AI). ResultsWhen the relaxed hand was right hand, the sEMG amplitude of digital extensor muscle were more in MVF and VF than in resting state (P < 0.05). In α bands, the main effect of training state on ERD/ERS was significant (F = 14.125, ηp2 = 0.469, P = 0.002), and it was higher in MVF than in VF. In β band, the main effect of training state on ERD/ERS was significant (F = 9.704, ηp2 = 0.378, P = 0.007), the interaction effect of moving hand and training state was significant on ERD/ERS (F = 8.014, ηp2 = 0.334, P = 0.012); for VF, ERD/ERS was higher in right hand movement than in left hand movement (F = 7.267, ηp2 = 0.312, P = 0.016); for right hand movement, ERD/ERS was higher in MVF than in VF (F = 17.530, ηp2 = 0.523, P = 0.001). At the position of C4 electrode, ERD/ERS was higher in right hand movement than in left hand movement under VF (t = -3.201, P = 0.006, Cohen's d = 0.776), and ERD/ERS was higher in MVF than in VF under right hand movement (t = -4.060, P = 0.001, Cohen's d = 0.985). Main effect of training state was significant on AI at β band (F = 5.796, ηp2 = 0.266, P = 0.028), and it was higher in MVF than in VF. ConclusionMVF may improve the activity of motor cortex neurons on the ipsilateral side of the motor hand through recruitment of frontal and parietal mirror neurons and reduction of interhemispheric and intracortical inhibitory activities, and it is more effective for the dominant hand training.

The slime hand illusion: Nonproprioceptive ownership distortion specific to the skin region.

The "slime hand illusion" is a simple and robust technique that uses mirror-visual feedback to produce a nonproprioceptive ownership distortion. The illusion can be easily evoked by the participant watching the experimenter pinching and pulling a chunk of slime in a mirror while the participant's hand, hidden behind the mirror, is similarly manipulated. This procedure produces a feeling of one of their fingers or the skin of their whole hand being stretched or deformed in a similar way to the visible slime. A public experiment found that more than 90% of participants reported a strong sense of skin or finger stretching. This report details a laboratory experiment performed to characterize the mechanisms behind the illusion more robustly. It reproduced this result and found that participants experienced a drift in their sense of skin location of approximately 30 cm on average, which is beyond the conventionally accepted range of proprioceptive drift.

Mirror visual feedback during unilateral finger movements is related to the desynchronization of cortical electroencephalographic somatomotor alpha rhythms.

Using a mirror adequately oriented, the motion of just one hand induces the illusion of the movement with the other hand. Here, we tested the hypothesis that such a mirror phenomenon may be underpinned by an electroencephalographic (EEG) event-related desynchronization/synchronization (ERD/ERS) of central alpha rhythms (around 10 Hz) as a neurophysiological measure of the interactions among cerebral cortex, basal ganglia, and thalamus during movement preparation and execution. Eighteen healthy right-handed male participants performed standard auditory-triggered unilateral (right) or bilateral finger movements in the No Mirror (M-) conditions. In the Mirror (M+) condition, the unilateral right finger movements were performed in front of a mirror oriented to induce the illusion of simultaneous left finger movements. EEG activity was recorded from 64 scalp electrodes, and the artifact-free event-related EEG epochs were used to compute alpha ERD. In the M- conditions, a bilateral prominent central alpha ERD was observed during the bilateral movements, while left central alpha ERD and right alpha ERS were seen during unilateral right movements. In contrast, the M+ condition showed significant bilateral and widespread alpha ERD during the unilateral right movements. These results suggest that the above illusion of the left movements may be related to alpha ERD measures reflecting excitatory desynchronizing signals in right lateral premotor and primary somatomotor areas possibly in relation to basal ganglia-thalamic loops.

Synergistic Immediate Cortical Activation on Mirror Visual Feedback Combined With a Soft Robotic Bilateral Hand Rehabilitation System: A Functional Near Infrared Spectroscopy Study.

BACKGROUND: Mirror visual feedback (MVF) has been widely used in neurological rehabilitation. Due to the potential gain effect of the MVF combination therapy, the related mechanisms still need be further analyzed. METHODS: Our self-controlled study recruited 20 healthy subjects (age 22.150 ± 2.661 years) were asked to perform four different visual feedback tasks with simultaneous functional near infrared spectroscopy (fNIRS) monitoring. The right hand of the subjects was set as the active hand (performing active movement), and the left hand was set as the observation hand (static or performing passive movement under soft robotic bilateral hand rehabilitation system). The four VF tasks were designed as RVF Task (real visual feedback task), MVF task (mirror visual feedback task), BRM task (bilateral robotic movement task), and MVF + BRM task (Mirror visual feedback combined with bilateral robotic movement task). RESULTS: The beta value of the right pre-motor cortex (PMC) of MVF task was significantly higher than the RVF task (RVF task: -0.015 ± 0.029, MVF task: 0.011 ± 0.033, P = 0.033). The beta value right primary sensorimotor cortex (SM1) in MVF + BRM task was significantly higher than MVF task (MVF task: 0.006 ± 0.040, MVF + BRM task: 0.037 ± 0.036, P = 0.016). CONCLUSION: Our study used the synchronous fNIRS to compare the immediate hemodynamics cortical activation of four visual feedback tasks in healthy subjects. The results showed the synergistic gain effect on cortical activation from MVF combined with a soft robotic bilateral hand rehabilitation system for the first time, which could be used to guide the clinical application and the future studies.

Development and Testing of a Portable Virtual Reality-Based Mirror Visual Feedback System with Behavioral Measures Monitoring.

Virtual Reality (VR) is a technology that has been used to provide the Mirror Visual Feedback (MVF) illusion to patients with promising results. In the present work, the goal is to design, develop and test a portable VR-based MVF system that monitors behavioral information about the performance of a simple motor task. The developed application runs in a stand-alone VR system and allows the researcher to select the real and virtual hands used to perform the motor task. The system was evaluated with a group of twenty healthy volunteers (12 men and 8 women) with ages between 18 and 66 years. Participants had to repetitively perform a motor task in four different experimental conditions: two mirror conditions (performing real movements with the dominant and with the non-dominant hand) and two non-mirror conditions. A significant effect of the experimental condition on embodiment score (p < 0.001), response time (p < 0.001), performance time (p < 0.001), trajectory length (p < 0.004) and trajectory maximum horizontal deviation (p < 0.001) was observed. Furthermore, a significant effect of the experimental moment (initial, middle and final parts of the training) on the performance time was observed (p < 0.001). These results show that the monitored parameters provide relevant information to evaluate the participant's task performance in different experimental conditions.

The Effect of Mirror Visual Feedback on Spatial Neglect for Patients after Stroke: A Preliminary Randomized Controlled Trial.

We investigated the effects of mirror visual feedback (MVF), with reference to using a glass wall or a covered mirror, on the reduction of spatial neglect for patients with stroke. A total of 21 subacute patients with left spatial neglect after right-hemispheric stroke were randomly assigned to 3 groups: MVF, sham 1 (viewing the hemiparetic arm through the transparent glass during bilateral arm movement) and sham 2 (using a covered mirror). The 3-week treatment program for all groups consisted of 12 sessions of movement tasks for the hemiparetic arm graded according to the severity of arm impairments. Blinded assessments were administered at pre/post and a three-week follow-up. The results showed that there was no significant advantage for MVF than sham 1; however, MVF was more beneficial than sham 2, as shown by the line crossing (p = 0.022). Improvement in discriminating the left-gap figures on the left and right side of the page in the Gap Detection Test was greater in MVF than using the covered mirror (p = 0.013; p = 0.010), showing a slight advantage of MVF in alleviating allocentric symptoms. Our study confirms that MVF was superior to using a covered mirror as a method for reducing spatial neglect and in alleviating its allocentric symptoms, but no significant advantage over bilateral arm movement through transparent glass was found. Further research in comparing their therapeutic effects is warranted.

Mirror visual feedback training can improve the upper extremity functioning of children with spastic hemiplegia / 中华物理医学与康复杂志

Objective:To observe the effect of mirror visual feedback training on upper limb function and muscle tension in children with spastic hemiplegia resulting from cerebral palsy (SHCP).Methods:Seventy-six children aged 2-5 with SHCP were randomly divided into a control group of 33 and a treatment group 34. All were given routine occupational therapy, physical therapy, massage and physical agents. Each therapy session lasted 30 minutes daily, 5 times a week over 3 weeks as a course of treatment. There was a one week interval after each of 6 courses, so the total treatment lasted 6 months. The treatment group was additionally trained with mirror visual feedback with the same schedule. Before, as well as after 3 and 6 months of treatment, each patient′s upper limb motor function, fine motor function and muscle tone were evaluated using the Fugl-Meyer motor function assessment scale (FMA), the Peabody fine motor development scales (PDMS-FM), the modified Ashworth scale (MAS) and integrated electromyograms (iEMGs).Results:There were no significant differences between the two groups before treatment. After both 3 and 6 months significant improvement was observed in both groups′ average FMA score, PDMS-FM total score, grip, and visual motor integration. At both points the treatment group′s averages were significantly better than those of the control group. The average MAS and iEMG results, however, were not significantly different at either time point.Conclusions:For children with spastic hemiplegia caused by cerebral palsy, mirror visual feedback training can effectively improve upper limb functioning, but it cannot reduce their muscle tone.

Effects of combining mirror visual feedback with robot-assisted gait training on the lower limb functioning of stroke survivors / 中华物理医学与康复杂志

Objective:To investigate any effect of combining mirror visual feedback (MVF) training with robot-assisted gait training (RGT) in promoting the recovery of lower limb motor function among stroke survivors.Methods:Sixty stroke survivors were randomly divided into a combined treatment group, an RGT group and a control group, each of 20. In addition to traditional rehabilitation, the RGT group received 30min of RGT 5 days a week for 4 weeks, while the combined treatment group underwent 30min of RGT and also 20min of MVF training with the same frequency and duration. Before and after the treatment, the lower extremities motor functioning and walking ability of all of the patients were assessed using the Fugl-Meyer Assessment for the lower extremities (FMA-LE), the Berg Balance Scale (BBS) and Functional Ambulation Categories (FAC).Results:There were no systematic differences in any of the measurements before the treatment. After the 4 weeks, however, the average FMA-LE, BBS and FAC scores of the combined treatment and RGT groups were significantly better than the control group′s averages, and those of the combined treatment group were significantly superior to the RGT group′s. All of the groups had, however, improved significantly compared with before the treatment.Conclusions:Robot-assisted gait training is more effective in enhancing the motor functioning of the lower extremities and walking ability when it is combined with MVF.

Immediate effect of adding mirror visual feedback to lateral weight-shifting training on the standing balance control of the unilateral spatial neglect model.

[Purpose] This study aimed to clarify the immediate effect of adding mirror visual feedback to lateral weight-shifting training on the standing balance control of the left unilateral spatial neglect model. [Participants and Methods] We included 64 healthy participants to create left unilateral spatial neglect models and divided them into four subgroups. Each subgroup received opposite lateral weight-shifting training with or without mirror visual feedback. We then evaluated the static and dynamic standing balance by measuring the center of pressure point alterations in the medial-lateral and anterior-posterior planes. We further evaluated the center of pressure length and bilateral load ratio. [Results] The center of pressure was significantly stable upon performing the eyes-open static standing balance test in the left weight-shifting training subgroup with mirror visual feedback. When participants performed the left dynamic standing balance test, the center of pressure moved significantly rightward and became significantly stable in the right weight-shifting training subgroup with mirror visual feedback. The left load ratio significantly decreased in the right weight-shifting training of subgroups that either did or did not receive mirror visual feedback upon performing the left dynamic standing balance test. [Conclusion] We concluded that adding mirror visual feedback to lateral weight-shifting training affected some measurements of standing balance control of the left unilateral spatial neglect model.

Modulation of Functional Connectivity in Response to Mirror Visual Feedback in Stroke Survivors: An MEG Study.

BACKGROUND: Several brain regions are activated in response to mirror visual feedback (MVF). However, less is known about how these brain areas and their connectivity are modulated in stroke patients. This study aimed to explore the effects of MVF on brain functional connectivity in stroke patients. MATERIALS AND METHODS: We enrolled 15 stroke patients who executed Bilateral-No mirror, Bilateral-Mirror, and Unilateral-Mirror conditions. The coherence values among five brain regions of interest in four different frequency bands were calculated from magnetoencephalographic signals. We examined the differences in functional connectivity of each two brain areas between the Bilateral-No mirror and Bilateral-Mirror conditions and between the Bilateral-Mirror and Unilateral-Mirror conditions. RESULTS: The functional connectivity analyses revealed significantly stronger connectivity between the posterior cingulate cortex and primary motor cortex in the beta band (adjusted p = 0.04) and possibly stronger connectivity between the precuneus and primary visual cortex in the theta band (adjusted p = 0.08) in the Bilateral-Mirror condition than those in the Bilateral-No mirror condition. However, the comparisons between the Bilateral-Mirror and Unilateral-Mirror conditions revealed no significant differences in cortical coherence in all frequency bands. CONCLUSIONS: Providing MVF to stroke patients may modulate the lesioned primary motor cortex through visuospatial and attentional cortical networks.

Mirror Visual Feedback Induces M1 Excitability by Disengaging Functional Connections of Perceptuo-Motor-Attentional Processes during Asynchronous Bimanual Movement: A Magnetoencephalographic Study.

Mirror visual feedback (MVF) has been shown to increase the excitability of the primary motor cortex (M1) during asynchronous bimanual movement. However, the functional networks underlying this process remain unclear. We recruited 16 healthy volunteers to perform asynchronous bimanual movement, that is, their left hand performed partial range of movement while their right hand performed normal full range of movement. Their ongoing brain activities were recorded by whole-head magnetoencephalography during the movement. Participants were required to keep both hands stationary in the control condition. In the other two conditions, participants were required to perform asynchronous bimanual movement with MVF (Asy_M) and without MVF (Asy_w/oM). Greater M1 excitability was found under Asy_M than under Asy_w/oM. More importantly, when receiving MVF, the visual cortex reduced its functional connection to brain regions associated with perceptuo-motor-attentional process (i.e., M1, superior temporal gyrus, and dorsolateral prefrontal cortex). This is the first study to demonstrate a global functional network of MVF during asynchronous bimanual movement, providing a foundation for future research to examine the neural mechanisms of mirror illusion in motor control.

Mirror Visual Feedback Prior to Robot-Assisted Training Facilitates Rehabilitation After Stroke: A Randomized Controlled Study.

Purpose: Robot-assisted training has been widely used in neurorehabilitation, but its effect on facilitating recovery after stroke remains controversial. One possible reason might be lacking consideration of the role of embodiment in robotic systems. Mirror visual feedback is an ideal method to approach embodiment. Thus, we hypothesized that mirror visual feedback priming with subsequent robot-assisted training might provide additional treatment benefits in rehabilitation. Method: This is a prospective, assessor-blinded, randomized, controlled study. Forty subacute stroke patients were randomly assigned into an experimental group (N = 20) or a control group (N = 20). They received either mirror visual feedback or sham-mirror visual feedback prior to robot-assisted training for 1.5 h/day, 5 days/week for 4 weeks. Before and after intervention, the Fugl-Meyer Assessment Upper Limb subscale, the Functional Independence Measure, the modified Barthel Index, and grip strength were measured. Scores of four specified games were recorded pre and post one-time mirror visual feedback priming before intervention in the experimental group. Results: All measurements improved significantly in both groups following interventions. Moreover, the Fugl-Meyer Assessment Upper Limb subscale, self-care subscale of the Functional Independence Measure, and the grip strength were improved significantly in the experimental group after a 4-week intervention, compared with the control group. Significantly higher scores of two games were revealed after one-time priming. Conclusions: Mirror visual feedback prior to robot-assisted training could prompt motor recovery, increase ability of self-care, and potentially enhance grip strength in stroke patients, compared to control treatment. Moreover, mirror visual feedback priming might have the capability to improve the patient's performance and engagement during robot-assisted training, which could prompt the design and development of robotic systems. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: ChiCTR1900023356.

Movement-Related Cortical Potentials in Embodied Virtual Mirror Visual Feedback.

Background: Mirror therapy is thought to drive interhemispheric communication, resulting in a balanced activation. We hypothesized that embodied virtual mirror visual feedback (VR-MVF) presented on a computer screen may produce a similar activation. In this proof-of-concept study, we investigated differences in movement-related cortical potentials (MRCPs) in the electroencephalogram (EEG) from different visual feedback of user movements in 1 stroke patient and 13 age-matched adults. Methods: A 60-year-old right-handed (Edinburgh score >95) male ischemic stroke [left paramedian pontine, National Institutes of Health Stroke Scale (NIHSS) = 6] patient and 13 age-matched right-handed (Edinburgh score >80) healthy adults (58 ± 9 years; six female) participated in the study. We recorded 16-electrode electroencephalogram (EEG), while participants performed planar center-out movements in two embodied visual feedback conditions: (i) direct (movements translated to the avatar's ipsilateral side) and (ii) mirror (movements translated to the avatar's contralateral side) with left (direct left/mirror left) or right (direct right/mirror right) arms. Results: As hypothesized, we observed more balanced MRCP hemispheric negativity in the mirror right compared to the direct right condition [statistically significant at the FC4 electrode; 99.9% CI, (0.81, 13)]. MRCPs in the stroke participant showed reduced lateralized negativity in the direct left (non-paretic) situation compared to healthy participants. Interestingly, the potentials were stronger in the mirror left (non-paretic) compared to direct left case, with significantly more bilateral negativity at FC3 [95% CI (0.758 13.2)] and C2 [95% CI (0.04 9.52)]. Conclusions: Embodied mirror visual feedback is likely to influence bilateral sensorimotor cortical subthreshold activity during movement preparation and execution observed in MRCPs in both healthy participants and a stroke patient.

Parieto-Occipital Alpha and Low-Beta EEG Power Reflect Sense of Agency.

The sense of agency (SoA) is part of psychophysiological modules related to the self. Disturbed SoA is found in several clinical conditions, hence understanding the neural correlates of the SoA is useful for the diagnosis and determining the proper treatment strategies. Although there are several neuroimaging studies on SoA, it is desirable to translate the knowledge to more accessible and inexpensive EEG-based biomarkers for the sake of applicability. However, SoA has not been widely investigated using EEG. To address this issue, we designed an EEG experiment on healthy adults (n = 15) to determine the sensitivity of EEG on the SoA paradigm using hand movement with parametrically delayed visual feedback. We calculated the power spectral density over the traditional EEG frequency bands for ten delay conditions relative to no delay condition. Independent component analysis and equivalent current dipole modeling were applied to address artifact rejection, volume conduction, and source localization to determine the effect of interest. The results revealed that the alpha and low-beta EEG power increased in the parieto-occipital regions in proportion to the reduced SoA reported by the subjects. We conclude that the parieto-occipital alpha and low-beta EEG power reflect the sense of agency.