Mirror symmetric bimanual movement priming can increase corticomotor excitability and enhance motor learning

Changes in corticomotor excitability and intracortical inhibition of the primary motor cortex forearm area induced by anodal tDCS

OBJECTIVE

Previous studies have investigated how tDCS over the primary motor cortex modulates excitability in the intrinsic hand muscles. Here, we tested if tDCS changes corticomotor excitability and/or cortical inhibition when measured in the extensor carpi radialis (ECR) and if these aftereffects can be successfully assessed during controlled muscle contraction.

METHODS

We implemented a double blind cross-over design in which participants (n = 16) completed two sessions where the aftereffects of 20 min of 1 mA (0.04 mA/cm2) anodal vs sham tDCS were tested in a resting muscle, and two more sessions where the aftereffects of anodal vs sham tDCS were tested in an active muscle.

RESULTS

Anodal tDCS increased corticomotor excitability in ECR when aftereffects were measured with a low-level controlled muscle contraction. Furthermore, anodal tDCS decreased short interval intracortical inhibition but only when measured at rest and after non-responders (n = 2) were removed. We found no changes in the cortical silent period.

CONCLUSION

These findings suggest that targeting more proximal muscles in the upper limb with anodal tDCS is achievable and corticomotor excitability can be assessed in the presence of a low-level controlled contraction of the target muscle.

Energy analysis reveals the negative effect of delays in passive movement mirror therapy

Wavelet transform energy analyses of the mean and standard error of the electromyogram (EMG) and electroencephalogram (EEG) of eight subjects were investigated in passive movement mirror therapies with no delay (in-phase) and with delay (out-of-phase) situations in two frequency bands of 7.81-15.62 and 15.62-31.25 Hz. It was found that the energy levels of EEG at electrode C4 in the in-phase situation were lower than those in out-of-phase situations, while the energy levels of flexor and extensor forearm muscle groups were larger. With two exceptions, this pattern could be seen in all other subjects. The difference between the in-phase (D0) and out-of-phase situations (D025 and D05) for the frequency range of 15.62-31.25 Hz was found to be significant at a significance level of 0.05 (paired t-test analysis). The respective elevation and decline of EEG and EGM with regard to the increase of the delay may indicate the necessity for synchronization of passive movement and mirror therapy.

Bilateral priming before wii-based movement therapy enhances upper limb rehabilitation and its retention after stroke: a case-controlled study

BACKGROUND

Motor deficits after a stroke are thought to be compounded by the development of asymmetric interhemispheric inhibition. Bilateral priming was developed to rebalance this asymmetry and thus improve therapy efficacy.

OBJECTIVE

This study investigated the effect of bilateral priming before Wii-based Movement Therapy to improve rehabilitation after stroke.

METHODS

Ten patients who had suffered a stroke (age, 23-77 years; 3-123 months after stroke) underwent a 14-day program of Wii-based Movement Therapy for upper limb rehabilitation. Formal Wii-based Movement Therapy sessions were immediately preceded by 15 minutes of bilateral priming, whereby active flexion-extension of the less affected wrist drove mirror-symmetric passive movements of the more affected wrist through a custom device. Functional movement was assessed at weeks 0 (before therapy), 3 (after therapy), and 28 (follow-up) using the Wolf Motor Function Test (WMFT), upper limb Fugl-Meyer Assessment (FMA), upper limb range of motion, and Motor Activity Log (MAL). Case-matched controls were patients who had suffered a stroke who received Wii-based Movement Therapy but not bilateral priming.

RESULTS

Upper limb functional ability improved for both groups on all measures tested. Posttherapy improvement on the FMA for primed patients was twice that of the unprimed patients (37.3% vs 14.6%, respectively) and was significantly better maintained at 28 weeks (P = .02). Improvements on the WMFT and MAL were similar for both groups, but the pattern of change in range of motion was strikingly different.

CONCLUSIONS

Bilateral priming before Wii-based Movement Therapy led to a greater magnitude and retention of improvement compared to control, especially measured with the FMA. These data suggest that bilateral priming can enhance the efficacy of Wii-based Movement Therapy, particularly for patients with low motor function after a stroke.

Bilateral Priming Accelerates Recovery of Upper Limb Function After Stroke

Background and Purpose—

The ability to live independently after stroke depends on the recovery of upper limb function. We hypothesized that bilateral priming with active–passive movements before upper limb physiotherapy would promote rebalancing of corticomotor excitability and would accelerate upper limb recovery at the subacute stage.

Methods—

A single-center randomized controlled trial of bilateral priming was conducted with 57 patients randomized at the subacute stage after first-ever ischemic stroke. The PRIMED group made device-assisted mirror symmetrical bimanual movements before upper limb physiotherapy, every weekday for 4 weeks. The CONTROL group was given intermittent cutaneous electric stimulation of the paretic forearm before physiotherapy. Assessments were made at baseline, 6, 12, and 26 weeks. The primary end point was the proportion of patients who reached their plateau for upper limb function at 12 weeks, measured with the Action Research Arm Test.

Results—

Odds ratios indicated that PRIMED participants were 3× more likely than controls to reach their recovery plateau by 12 weeks. Intention-to-treat and per-protocol analyses showed a greater proportion of PRIMED participants achieved their plateau by 12 weeks (intention to treat, χ 2 =4.25; P =0.039 and per protocol, χ 2 =3.99; P =0.046). ANOVA of per-protocol data showed PRIMED participants had greater rebalancing of corticomotor excitability than controls at 12 and 26 weeks and interhemispheric inhibition at 26 weeks (all P <0.05).

Conclusions—

Bilateral priming accelerated recovery of upper limb function in the initial weeks after stroke.

Clinical Trial Registration—

URL: http://www.anzctr.org.au . Unique identifier: ANZCTR1260900046822.

Effect of task-based mirror therapy on motor recovery of the upper extremity in chronic stroke patients: a pilot study

BACKGROUND AND AIMS

Mirror therapy (MT) is an alternative therapeutic intervention that uses the interaction of visuomotor-proprioception inputs to enhance movement performance of the impaired limb. Despite strong evidence for task-specific training in stroke, MT has been investigated using nontask movements. The aim of this pilot study was to assess the effectiveness of task-based MT on motor recovery of the upper extremity in chronic stroke patients.

METHOD

In a pretest-posttest single-group design, a convenience sample of 13 chronic stroke patients at an occupational therapy department of a rehabilitation institute was assessed on a task-based MT intervention. Participants received a task-based MT program, performing various tasks by the less affected upper extremity and observing in the mirror box along with conventional management, 4 days per week for 4 weeks. Fugl-Meyer Assessment (FMA), which includes subsection upper extremity (FMA-UE) and subpart upper arm (FMA-UA) and hand (FMA-WH), was used as an outcome measure.

RESULTS

Participants showed no significant improvement for FMA-UE and FMA-UA at postassessment. FMA-UE changed from 43% to 51%. Post FMA-UA score showed only 2% improvement. However, there was statistically significant improvement on mean scores of FMA-WH at postassessment (16.21 ± 3.06) as compared with the prescores (12.29 ± 3.1; P < .05). FMA-WH improved from 41% to 54%.

CONCLUSIONS

The preliminary findings suggest that task-based MT is effective in improving wrist and hand motor recovery in chronic stroke patients. Further studies in the form of randomized trials are needed to validate its effectiveness.

Mirror versus parallel bimanual reaching

Background

In spite of their importance to everyday function, tasks that require both hands to work together such as lifting and carrying large objects have not been well studied and the full potential of how new technology might facilitate recovery remains unknown.

Methods

To help identify the best modes for self-teleoperated bimanual training, we used an advanced haptic/graphic environment to compare several modes of practice. In a 2-by-2 study, we compared mirror vs. parallel reaching movements, and also compared veridical display to one that transforms the right hand’s cursor to the opposite side, reducing the area that the visual system has to monitor. Twenty healthy, right-handed subjects (5 in each group) practiced 200 movements. We hypothesized that parallel reaching movements would be the best performing, and attending to one visual area would reduce the task difficulty.

Results

The two-way comparison revealed that mirror movement times took an average 1.24 s longer to complete than parallel. Surprisingly, subjects’ movement times moving to one target (attending to one visual area) also took an average of 1.66 s longer than subjects moving to two targets. For both hands, there was also a significant interaction effect, revealing the lowest errors for parallel movements moving to two targets (p < 0.001). This was the only group that began and maintained low errors throughout training.

Conclusion

Combined with other evidence, these results suggest that the most intuitive reaching performance can be observed with parallel movements with a veridical display (moving to two separate targets). These results point to the expected levels of challenge for these bimanual training modes, which could be used to advise therapy choices in self-neurorehabilitation.

Effectiveness of motor imagery or mental practice in functional recovery after stroke: a systematic review

INTRODUCTION

In recent decades, many stroke rehabilitation methods have been developed. Mental practice (MP) is a dynamic state in which the subject evokes an imaginary representation of a motor action or skill in order to learn or perfect that action. Although functional imaging has shown that MP produces similar cortical activation patterns to those of movement, the clinical effectiveness of such methods in rehabilitation and functional recovery has yet to be demonstrated.

DEVELOPMENT

Systematic search of all clinical studies published in the main scientific databases between December 2011 and October 2012 concerning mental practice in stroke rehabilitation. We selected 23 clinical trials testing different MP protocols in patients with hemiparesis.

CONCLUSIONS

MP is effective when used in conjunction with conventional physical therapy for functional rehabilitation of both upper and lower limbs, as well as for the recovery of daily activities and skills. Owing to the heterogeneity of the studies with regard to the intervention protocol, specific imagery technique, time spent practicing, patient characteristics, etc., more studies are needed in order to determine the optimal treatment protocol and patient profile.

Transfer of ballistic motor skill between bilateral and unilateral contexts in young and older adults: neural adaptations and behavioral implications

Bilateral movement rehabilitation is gaining popularity as an approach to improve the recovery not only of bimanual function but also of unilateral motor tasks. While the neural mechanisms mediating the transfer of bilateral training gains into unimanual contexts are not fully understood, converging evidence from behavioral, neurophysiological, and imaging studies suggests that bimanual movements are not simply the superposition of unimanual tasks undertaken with both (upper) limbs. Here we investigated the neural responses in both hemispheres to bilateral ballistic motor training and the extent to which performance improvements transferred to a unimanual task. Since aging influences interhemispheric interactions during movement production, both young (n = 9; mean age 19.4 yr; 6 women, 3 men) and older (n = 9; 66.3 yr; 7 women, 2 men) adults practiced a bilateral motor task requiring simultaneous "fast-as-possible" abductions of their left and right index fingers. Changes in bilateral and unilateral performance, and in corticospinal excitability and intracortical inhibition, were assessed. Strong transfer was observed between bimanual and unimanual contexts for both age groups. However, in contrast to previous reports of substantial bilateral cortical adaptations following unilateral training, increases in corticospinal excitability following bilateral training were not statistically reliable, and a release of intracortical inhibition was only observed for older adults. The results indicate that the neural mechanisms of motor learning for bilateral ballistic tasks differ from those that underlie unimanual ballistic performance improvement but that aging results in a greater overlap of the neural mechanisms mediating bilateral and unilateral ballistic motor performance.