Do mirror glasses have the same effect on brain activity as a mirror box? Evidence from a functional magnetic resonance imaging study with healthy subjects

Effect of Graded Motor Imagery Combined With Repetitive Transcranial Magnetic Stimulation on Upper Extremity Motor Function in Stroke Patients: A Randomized Controlled Trial

OBJECTIVE

To investigate the efficacy of graded motor imagery therapy (GMI) and repetitive transcranial magnetic stimulation (rTMS) on upper extremity function alone and in combination in patients with stroke.

DESIGN

This was a prospective randomized controlled trial.

SETTING

A rehabilitation hospital.

PARTICIPANTS

Participants (N=56) were randomized into GMI (n=19), rTMS (n=18), or combined groups (n=19).

INTERVENTIONS

There were 2 interventions: (1) 20 minutes of 1 Hz rTMS. (2) 30 minutes of GMI. In addition to this, all participants receive conventional rehabilitation including 120 minutes of physical therapy and occupational therapy daily. All treatments were administered once a day, 5 days a week, for 4 weeks. The Fugl-Meyer assessment of upper extremity (FMA-UE), Action Research Arm Test (ARAT), modified Barthel Index (MBI), motor activity log (MAL), and motor evoked potential (MEP) were assessed in a blinded manner at baseline and 4 weeks after treatment, respectively.

MAIN OUTCOME MEASURES

The primary endpoint was the improvement from baseline in FMA-UE for stroke patients at 4 weeks.

RESULTS

After 4 weeks of treatment, the FMA-UE scores in the GMI, rTMS, and combined groups were higher than those at baseline assessment, with statistically significant differences among the 3 groups (P=.009). The efficacy of the combined group was significantly better than that of the GMI and rTMS groups (P=.015, P=.043, respectively). In the motor activity log-amount of use (MAL-AOU) score, the efficacy of the combined group was better than that of the rTMS group (P=.035).

CONCLUSIONS

Both GMI and rTMS were effective in improving upper extremity function in patients with stroke, but the combination of the 2 techniques was more effective. However, GMI was better than rTMS in improving the interest of stroke patients in active training.

Effect of Mirror Therapy on Upper Limb Function in Children and Adolescents with Hemiplegic Cerebral Palsy: A Systematic Review and Meta-Analysis

BACKGROUND

This review aimed to explore the effect of mirror therapy (MT) on upper limb function in children and adolescents with hemiplegic cerebral palsy (HCP).

METHODS

MEDLINE, CENTRAL, Scopus, PEDro, and Web of Science were systematically searched. PEDro scale  was used for the quality assessment of included trials. Risk of Bias assessment was done using Cochrane Risk-of-bias tool version 2. Meta-analysis was performed on four of the seven studies included.

RESULTS & CONCLUSION

The majority of the trials included in this review found MT efficacious in improving motor function in HCP. Quantitative analysis of the included trials using QUEST scores for evaluation of quality of upper extremity function revealed positive but non-significant difference between the groups (MD = -0.12; 95% CI = -2.57,2.33; Z = 0.09, p = .92). Pooled analysis of the included trials using BBT, however, favored control (MD = 4.98; 95% CI = 2.32,7.63; Z = 3.67, p = .0002).

Evidence of mirror therapy for recruitment of ipsilateral motor pathways in stroke recovery: A resting fMRI study

Mirror therapy (MT) has been proposed to promote motor recovery post-stroke through activation of mirror neuron system, recruitment of ipsilateral motor pathways, or/and increasing attention toward the affected limb. However, neuroimaging evidence for these mechanisms is still lacking. To uncover the underlying mechanisms, we designed a randomized controlled study and used a voxel-based whole-brain analysis of resting-state fMRI to explore the brain reorganizations induced by MT. Thirty-five stroke patients were randomized to an MT group (n ​= ​16) and a conventional therapy (CT) group (n ​= ​19) for a 4-week intervention. Before and after the intervention, the Fugl-Meyer Assessment Upper Limb subscale (FMA-UL) and resting-state fMRI were collected. A healthy cohort (n ​= ​16) was established for fMRI comparison. The changes in fractional amplitude of low-frequency fluctuation (fALFF) and seed-based functional connectivity were analyzed to investigate the impact of intervention. Results showed that greater FMA-UL improvement in the MT group was associated with the compensatory increase of fALFF in the contralesional precentral gyrus (M1) region and the re-establishment of functional connectivity between the bilateral M1 regions, which facilitate motor signals transmission via the ipsilateral motor pathways from the ipsilesional M1, contralesional M1, to the affected limb. A step-wise linear regression model revealed these two brain reorganization patterns collaboratively contributed to FMA-UL improvement. In conclusion, MT achieved motor rehabilitation primarily by recruitment of the ipsilateral motor pathways. Trial Registration Information: http://www.chictr.org.cn. Unique Identifier. ChiCTR-INR-17013644, submitted on December 2, 2017.

Effectiveness of mirror therapy on upper limb function, activities of daily living, and depression in post-stroke depression patients

Objectives

This study aims to investigate the effects of mirror therapy (MT) on upper limb function, activities of daily living (ADLs), and depression in post-stroke depression patients.

Patients and methods

Between November 2018 and December 2019, a total of 60 post-stroke patients (33 males, 27 females; mean age: 58.45±11.13 years; range, 35 to 88 years) were included. The patients were randomly divided into either the cosntrol group (n=30) or the MT group (n=30). Regular occupational therapy was provided for the control group (two times per day for 30 min per session, five times per week over four weeks). Occupational therapy and MT were used to treat patients in the mirror group (one 30 min session once per day, five times per week over four weeks). Motor function (Fugl-Meyer Assessment of the Upper Extremity, FMA-UE), ADL (Modified Barthel Index, MBI) and depression (17-item Hamilton Depression Scale, HAMD-17) were used to evaluate the treatment outcomes.

Results

Before treatment, the mean HAMD-17, FMA-UE, and MBI scores showed no significant difference between the two groups (p>0.05). After treatment, the mirror group exhibited more significant improvements than the control group in terms of the mean HAMD-17, FM-UE, and MBI (p<0.05). After four weeks, the mean FMA-UE and MBI scores revealed more significant improvements than the baseline scores in the control group (p<0.01). The mean HAMD-17, FMA-UE, and MBI scores showed more significant improvements than the baseline scores in the MT group (p<0.001).

Conclusion

Based on these results, MT can effectively improve motor function, ADLs, and depression in post-stroke depression patients. The curative effectiveness of MT seems to be more prominent than the regular occupational therapy.

Sequential neural activity in sensorimotor area and mirror neural system for graded mirror therapy with imagined hand movements

BACKGROUND

Graded motor imagery (GMI) therapy is a neural rehabilitative physiotherapy that has been shown to alleviate the severity of complex regional pain syndrome, phantom limb pain and disability.

OBJECTIVE

To identify neural networks associated with the use of graded mirror therapy (MT) while imagining hand movements.

METHODS

We made a block-design functional magnetic resonance imaging study of MT included three experiments: (1) immobile unimanual MT (IU-MT), in which the right hand flexed and made a fist, which then remained immobile; (2) mobilization unimanual MT (MU-MT), in which the right hand performed a flexion-extension movement; and (3) mobilization bimanual MT (MB-MT), in which both hands performed a flexion-extension movement. When subjects started their hand movements, they gazed at the mirror and imagined the same movement behind the mirror.

RESULTS

We discovered that the sensorimotor area of the left brain, superior temporal gyrus/middle temporal gyrus (STG/MTG) of the right brain and visual areas were activated by IU-MT. In MU-MT, only the STG/MTG was activated. Furthermore, MB-UT mostly activated the sensorimotor area and STG of the right brain. However, there were no brain areas activated by MU-MT compared with IU-MT or MB-MT; but, MB-MT activated more motor areas than IU-MT. Importantly, we determined that the level of mirror imagery was negatively correlated with signals in the mirror neuron system (MNS) and positively related with the signals in the sensorimotor areas.

CONCLUSIONS

We suggest that graded MT might be a sequential therapeutic program that can enhance the sensorimotor cortex. The MNS might have an initiating role in graded MT. Thus, there is the possibility that graded MT is a helpful treatment strategy for the rehabilitation of dysfunctional patients.

Neural Processes Underlying Mirror-Induced Visual Illusion: An Activation Likelihood Estimation Meta-Analysis

Introduction: Neuroimaging studies on neural processes associated with mirror-induced visual illusion (MVI) are growing in number. Previous systematic reviews on these studies used qualitative approaches.

Objective: The present study conducted activation likelihood estimation (ALE) meta-analysis to locate the brain areas for unfolding the neural processes associated with the MVI.

Method: We searched the CINAHL, MEDLINE, Scopus, and PubMed databases and identified eight studies (with 14 experiments) that met the inclusion criteria.

Results: Contrasting with a rest condition, strong convergence in the bilateral primary and premotor areas and the inferior parietal lobule suggested top-down motor planning and execution. In addition, convergence was identified in the ipsilateral precuneus, cerebellum, superior frontal gyrus, and superior parietal lobule, clusters corresponding to the static hidden hand indicating self-processing operations, somatosensory processing, and motor control. When contrasting with an active movement condition, additional substantial convergence was revealed in visual-related areas, such as the ipsilateral cuneus, fusiform gyrus, middle occipital gyrus (visual area V2) and lingual gyrus, which mediate basic visual processing.

Conclusions: To the best of our knowledge, the current meta-analysis is the first to reveal the visualization, mental rehearsal and motor-related processes underpinning the MVI and offers theoretical support on using MVI as a clinical intervention for post-stroke patients.

Role of kinaesthetic motor imagery in mirror-induced visual illusion as intervention in post-stroke rehabilitation

Mirror-induced visual illusion obtained through mirror therapy is widely used to facilitate motor recovery after stroke. Activation of primary motor cortex (M1) ipsilateral to the moving limb has been reported during mirror-induced visual illusion. However, the mechanism through which the mirror illusion elicits motor execution processes without movements observed in the mirrored limb remains unclear. This study aims to review evidence based on brain imaging studies for testing the hypothesis that neural processes associated with kinaesthetic motor imagery are attributed to ipsilateral M1 activation. Four electronic databases were searched. Studies on functional brain imaging, investigating the instant effects of mirror-induced visual illusion among stroke survivors and healthy participants were included. Thirty-five studies engaging 78 stroke survivors and 396 healthy participants were reviewed. Results of functional brain scans (n = 20) indicated that half of the studies (n = 10, 50%) reported significant changes in the activation of ipsilateral M1, which mediates motor preparation and execution. Other common neural substrates included primary somatosensory cortex (45%, kinaesthesia), precuneus (40%, image generation and self-processing operations) and cerebellum (20%, motor control). Similar patterns of ipsilateral M1 activations were observed in the two groups. These neural substrates mediated the generation, maintenance, and manipulation of motor-related images, which were the key processes in kinaesthetic motor imagery. Relationships in terms of shared neural substrates and mental processes between mirror-induced visual illusion and kinaesthetic motor imagery generate new evidence on the role of the latter in mirror therapy. Future studies should investigate the imagery processes in illusion training for post-stroke patients.

Exploring Hemodynamic Responses Using Mirror Visual Feedback With Electromyogram-Triggered Stimulation and Functional Near-Infrared Spectroscopy

In recent years, mirror visual feedback (MVF) therapy combined with electrical stimulation (ES) have been proposed for patients with hemiparesis. However, the neurophysiological effect remains unknown. We investigated the effects of MVF by itself and along with electromyogram-triggered ES (ETES) on hemodynamic responses using functional near-infrared spectroscopy (NIRS). Eighteen healthy subjects participated in this study. We measured changes in brain oxygenation using 48 NIRS channels. We investigated the effects of three main factors of visual feedback (observation of a mark, right hand, and hand movements via mirror) with or without ES on bilateral precentral gyrus (PrG), postcentral gyrus (PoG), supplementary motor area (SMA), supramarginal gyrus area (SMG), and angular gyrus (AG) to determine the contribution of each factor. The results showed that the left PoG was significantly more activated when performing mirrored tasks (MT) than when performing circle or Right-hand Tasks (RTs). In addition, the right PoG and right SMA in MT were significantly more activated than in MT + ES cases. Our findings suggested that observation of movements through the mirror caused activation of the postcentral gyrus rather than the PrG, and MVF along with ETES decreased cortical activation.

The Stochastic Entanglement and Phantom Motor Execution Hypotheses: A Theoretical Framework for the Origin and Treatment of Phantom Limb Pain

Phantom limb pain (PLP) is a debilitating condition common after amputation that can considerably hinder patients' quality of life. Several treatments have reported promising results in alleviating PLP. However, clinical evaluations are usually performed in small cohorts and rigorous clinical trials are scarce. In addition, the underlying mechanisms by which novel interventions alleviate PLP are often unclear, potentially because the condition itself is poorly understood. This article presents a theoretical framework of PLP that can be used as groundwork for hypotheses of novel treatments. Current hypotheses on the origins of PLP are discussed in relation to available clinical findings. Stochastic entanglement of the pain neurosignature, or connectome, with impaired sensorimotor circuitry is proposed as an alternative hypothesis for the genesis of PLP, and the implications and predictions this hypothesis entails are examined. In addition, I present a hypothesis for the working mechanism of Phantom Motor Execution (PME) as a treatment of PLP, along with its relation to the aforementioned stochastic entanglement hypothesis, which deals with PLP's incipience. PME aims to reactivate the original central and peripheral circuitry involved in motor control of the missing limb, along with increasing dexterity of stump muscles. The PME hypothesis entails that training of phantom movements induces gradual neural changes similar to those of perfecting a motor skill, and these purposefully induced neural changes disentangle pain processing circuitry by competitive plasticity. This is a testable hypothesis that can be examined by brain imaging and behavioral studies on subjects undergoing PME treatment. The proposed stochastic entanglement hypothesis of PLP can be generalized to neuropathic pain due to sensorimotor impairment, and can be used to design suitable therapeutic treatments.

Camera-Based Mirror Visual Feedback: Potential to Improve Motor Preparation in Stroke Patients

Mirror visual feedback (MVF) is used widely for motor recovery after stroke, but an optimal training setup and systematic procedure are lacking. New optimization strategies have been proposed, one of which is a camera technique. We investigated the effects of a camera-based MVF setup on motor function and motor processes upstream for upper-limb rehabilitation. Seventy-nine stroke patients were assigned randomly to the MVF group (MG; ${N} = {38}$ ) or conventional group (CG; ${N} = {41}$ ), which, respectively, received camera-based MVF and dosage-equivalent physiotherapy or/and occupational therapy for 1 h/day and five days/week for four weeks. Two clinical scales were used to quantify the effect of the intervention methods: the Fugl-Meyer assessment-upper limb (FMA-UL) subscale and Barthel index. The hand laterality task was used to evaluate the ability of mental rotation, including the reaction time and accuracy. All measurements were improved significantly for both groups following intervention. FMA-UL was improved significantly in the MG compared with that in the CG. In lateralization tasks, the RT of the MG was significantly shorter than that of the CG at the endpoint. For all patients, judgments for the affected side were significantly slower and less accurate than for the less-affected side. Subgroup analyses suggested greater benefits of motor function, the activities of daily life, and mental rotation were achieved in subacute patients after MVF. A trend toward greater improvements in motor function for patients with severe-moderate motor impairment and patients with right-hemisphere damage were also revealed. Camera-based MVF has improved the motor function and ability of mental rotation for stroke patients, especially for patients in the subacute stage, which indicates the potential to improve motor preparation. Further studies might combine mental rotation with electroencephalography to investigate the neuro-mechanism of MVF.