Dual-tDCS Enhances Online Motor Skill Learning and Long-Term Retention in Chronic Stroke Patients

Post-stroke changes in brain structure and function can both influence acute upper limb function and subsequent recovery

Improving outcomes after stroke depends on understanding both the causes of initial function/impairment and the mechanisms of recovery. Recovery in patients with initially low function/high impairment is variable, suggesting the factors relating to initial function/impairment are different to the factors important for subsequent recovery. Here we aimed to determine the contribution of altered brain structure and function to initial severity and subsequent recovery of the upper limb post-stroke. The Nine-Hole Peg Test was recorded in week 1 and one-month post-stroke and used to divide 36 stroke patients (18 females, age: M = 66.56 years) into those with high/low initial function and high/low subsequent recovery. We determined differences in week 1 brain structure (Magnetic Resonance Imaging) and function (Magnetoencephalography, tactile stimulation) between high/low patients for both initial function and subsequent recovery. Lastly, we examined the relative contribution of changes in brain structure and function to recovery in patients with low levels of initial function. Low initial function and low subsequent recovery are related to lower sensorimotor β power and greater lesion-induced disconnection of contralateral [ipsilesional] white-matter motor projection connections. Moreover, differences in intra-hemispheric connectivity (structural and functional) are unique to initial motor function, while differences in inter-hemispheric connectivity (structural and functional) are unique to subsequent motor recovery. Function-related and recovery-related differences in brain function and structure after stroke are related, yet not identical. Separating out the factors that contribute to each process is key to identifying potential therapeutic targets for improving outcomes.

Is non-invasive neuromodulation a viable technique to improve neuroplasticity in individuals with acquired brain injury? A review

Objective

This study aimed to explore and evaluate the efficacy of non-invasive brain stimulation (NIBS) as a standalone or coupled intervention and understand its mechanisms to produce positive alterations in neuroplasticity and behavioral outcomes after acquired brain injury (ABI).

Data sources

Cochrane Library, Web of Science, PubMed, and Google Scholar databases were searched from January 2013 to January 2024.

Study selection

Using the PICO framework, transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) randomized controlled trials (RCTs), retrospective, pilot, open-label, and observational large group and single-participant case studies were included. Two authors reviewed articles according to pre-established inclusion criteria.

Data extraction

Data related to participant and intervention characteristics, mechanisms of change, methods, and outcomes were extracted by two authors. The two authors performed quality assessments using SORT.

Results

Twenty-two studies involving 657 participants diagnosed with ABIs were included. Two studies reported that NIBS was ineffective in producing positive alterations or behavioral outcomes. Twenty studies reported at least one, or a combination of, positively altered neuroplasticity and improved neuropsychological, neuropsychiatric, motor, or somatic symptoms. Twenty-eight current articles between 2020 and 2024 have been studied to elucidate potential mechanisms of change related to NIBS and other mediating or confounding variables.

Discussion

tDCS and TMS may be efficacious as standalone interventions or coupled with neurorehabilitation therapies to positively alter maladaptive brain physiology and improve behavioral symptomology resulting from ABI. Based on postintervention and follow-up results, evidence suggests NIBS may offer a direct or mediatory contribution to improving behavioral outcomes post-ABI.

Conclusion

More research is needed to better understand the extent of rTMS and tDCS application in affecting changes in symptoms after ABI.

How does combining physical therapy with transcranial direct stimulation improve upper-limb motor functions in patients with stroke? A theory perspective

More than half of stroke survivors suffer from upper-limb dysfunction that persists years after stroke, negatively impacting patients' independence and, therefore, affecting their quality of life. Intense motor rehabilitation is required after a stroke to facilitate motor recovery. More importantly, finding new ways to maximize patients' motor recovery is a core goal of stroke rehabilitation. Thus, researchers have explored the potential benefits of combining the effects of non-invasive brain stimulation with physical therapy rehabilitation. Specifically, combining transcranial direct stimulation (tDCS) with neurorehabilitation interventions can boost the brain's responses to interventions and maximize the effects of rehabilitation to improve upper-limb recovery post-stroke. However, it is still unclear which modes of tDCS are optimal for upper-limb motor recovery in patients with stroke when combined with physical therapy interventions. Here, the authors review the existing literature suggesting combining physical therapy rehabilitation with tDCS can maximize patients' motor recovery using the Interhemispheric Competition Model in Stroke. The authors focus on two main rehabilitation paradigms, which are constraint-induced movement therapy (CIMT) and Mirror therapy with and without tDCS. The authors also discuss potential studies to elucidate further the benefit of using tDCS adjunct with these upper-limb rehabilitation paradigms and its effectiveness in patients with stroke, with the ultimate goal of maximizing patients' motor recovery.

Bimanual coordinated motor skill learning in patients with a chronic cerebellar stroke

Cerebellar strokes induce coordination disorders that can affect activities of daily living. Evidence-based neurorehabilitation programs are founded on motor learning principles. The cerebellum is a key neural structure in motor learning. It is unknown whether and how well chronic cerebellar stroke individuals (CCSIs) can learn to coordinate their upper limbs through bimanual motor skill learning. The aim was to determine whether CCSIs could achieve bimanual skill learning through a serious game with the REAplan® robot and to compare CCSIs with healthy individuals (HIs). Over three consecutive days, sixteen CCSIs and eighteen HIs were trained on an asymmetric bimanual coordination task ("CIRCUIT" game) with the REAplan® robot, allowing quantification of speed, accuracy and coordination. The primary outcomes were the bimanual speed/accuracy trade-off (BiSAT) and bimanual coordination factor (BiCo). They were also evaluated on a bimanual REACHING task on Days 1 and 3. Correlation analyses between the robotic outcomes and clinical scale scores were computed. Throughout the sessions, BiSAT and BiCo improved during the CIRCUIT task in both HIs and CCSIs. On Day 3, HIs and CCSIs showed generalization of BiSAT, BiCo and transferred to the REACHING task. There was no significant between-group difference in progression. Four CCSIs and two HIs were categorized as "poor learners" according to BiSAT and/or BiCo. Increasing age correlated with reduced BiSAT but not BiCo progression. Over three days of training, HIs and CCSIs improved, retained, generalized and transferred a coordinated bimanual skill. There was no between-group difference, suggesting plastic compensation in CCSIs. Clinical trial NCT04642599 approved the 24th of November 2020.

Dual-tDCS combined with sensorimotor training promotes upper limb function in subacute stroke patients: A randomized, double-blinded, sham-controlled study

BACKGROUND

Dual transcranial direct current stimulation (tDCS) over the bilateral primary somatosensory cortex (PSC) has potential benefits in stroke. In addition, compared with traditional rehabilitation training, sensorimotor training can significantly improve the sensorimotor function of patients. However, the efficacy of dual-tDCS combined with sensorimotor training in patients with subacute stroke is unknown.

OBJECTIVE

To assess whether dual-tDCS may enhance the efficacy of sensorimotor training on the upper limb functions in patients with subacute stroke. In addition, this study aims to explore the potential clinical mechanism of this combination therapy.

METHODS

We randomized 52 individuals with first-ever, unilateral subcortical stroke into the experimental group (n = 26) and the control group (n = 26). Patients in the experimental group received 20 min of dual-tDCS over the PSC and 40 min of sensorimotor training each session, while patients in the control group received sham dual-tDCS. The treatment cycle was a 1-h session of therapy each day, 5 days per week for 4 weeks. The Fugl-Meyer Assessment of Upper Extremity (FMA-UE) subscale, Action Research Arm Test (ARAT), Box and Block test (BBT), Erasmus MC revised Nottingham sensory assessment scale (Em-NSA), Neurometer sensory nerve quantitative detector (CPT), the Barthel index (BI), and Hospital Anxiety and Depression Scale (HADS) were used to assess upper limb function, activities of daily living (ADL), and mental health before and after the 4-week treatment period. In addition, functional near-infrared spectroscopy (fNIRS) was used to explore potential clinical brain mechanisms.

RESULTS

Both groups showed significant improvement in all clinical scales (All p < 0.05) after treatment. Compared with sham-tDCS plus sensorimotor training, active dual-tDCS coupled with sensorimotor training can significantly improve the FMA-UE, ARAT, Em-NSA-Stereognosis, and CPT-2K Hz. In addition, dual-tDCS combined with sensorimotor training can significantly activate the left pre-Motor and supplementary motor cortex (PM-SMC) and enhance the functional connection between the left somatosensory association cortex (SAC) and RPM-SMC. Furthermore, the difference of FMA-UE in the experimental group was positively correlated with the functional connectivity of RPM-SMC-LSAC (r = 0.815, p < 0.001).

CONCLUSION

Dual-tDCS over the PSC combined with sensorimotor training can improve upper limb sensory and motor dysfunction, enhance ADL, and alleviate depression and anxiety for subacute stroke patients. Our results indicated that RPM-SMC-LSAC may be potential therapeutic targets for dual-tDCS in upper limb rehabilitation on stroke.

The effect of transcranial direct current stimulation associated with video game training on the postural balance of older women in the community: A blind, randomized, clinical trial

BACKGROUND

Falls are frequent in older adults and can cause trauma, injury, and death. Fall prevention with virtual reality presents good results in improving postural control. Transcranial Direct Current Stimulation (tDCS) has been used with the same aim; however, the combination of the two techniques has still been little studied.

PURPOSE

To assess whether tDCS can enhance the effect of video game training (VGT) on improving the postural balance of healthy older women.

METHOD

A blinded, randomized, controlled clinical trial was conducted with 57 older women who were randomized to three balance training groups: Control Group (VGT), Anodal Group (VGT combined with anodic tDCS-atDCS), and Sham Group (VGT combined with sham tDCS-stDCS). Balance training was performed twice a week for four weeks, totalizing eight 20-min sessions using VGT associated with tDCS. Postural balance was assessed pre-and post-training and 30 days after the end of the eight sessions using the Mini-Balance Evaluation Systems Test.

RESULTS

Compared to pre-intervention the Mini BEST test increased similarly in the three groups in post-intervention (control: pre 23.7 ± 2.8 to post 27.0 ± 2.2; anodal: pre 24.4 ± 1 to post 27.7 ± 0.8 and sham: pre 24.2 ± 1.9 to post 26.5 ± 1.6; p < 0.001) and follow-up (control: pre 23.7 ± 2.8 to follow-up 26.8 ± 2.3; anodal: pre 24.4 ± 1 to follow-up 27.3 ± 1.4 and sham: pre 24.2 ± 1.9 to follow-up 26.8 ± 1.5; p < 0.001).

CONCLUSION

There was an improvement in the postural balance of the three training groups that were independent of tDCS.

DISCUSSION

Some studies have shown the positive tDCS effects associated with other tasks to improve balance. However, these results convey the effects of only anodic-tDCS compared to sham-tDCS. Possibly, the effect of VGT surpassed the tDCS effects, promoting a ceiling effect from the combination of these two therapies. However, studies with other therapies combined with tDCS for older adults deserve to be investigated, as well as in frail older people.

Relationship between skill training and skill transfer through the example of bimanual motor learning

Skill training aims to improve the performance of the task at hand and aims to transfer the acquired skill to related tasks. Both skill training and skill transfer are part of our everyday lives, and essential for survival, and their importance is reflected in years of research. Despite these enormous efforts, however, the complex relationship between skill training and skill transfer is not yet portrayed completely. Building upon two theories, we probed this relationship through the example of bimanual learning with a large cross-sectional design (N = 450) using an online framework. We designed five training tasks which differed in the variance of the training material (schema theory) and three transfer tasks differing in their similarity to the training task (identical elements theory). Theoretically, the five training tasks and the three transfer tasks varied approximately linearly from each other. Empirical data, however, suggested merely the presence of three statistically different training tasks and two significantly different transfer tasks, indicating a nonlinear relationship. Against our expectation, Bayesian statistics suggested that the type of skill training was not related to the type of skill transfer. However, the amount of skill training was positively related to the amount of skill transfer. Together, we showed that motor learning studies can be conducted online. Further, our results shed light on the complex relationship between skill training and skill transfer. Understanding this relationship has wide-ranging practical implications for the general population, particularly for musicians, athletes and patients recovering from injury.

Adaptation and Validation of a Serious Game for Motor Learning Training in Children with Cerebral Palsy

Objective: Children with cerebral palsy (CP) present motor learning disorders and somatosensory dysfunction. Although many protocols use videogames in children with CP, few apply or examine motor learning principles. This study aims at (1) implementing therapist-user-designer collaboration in adapting a videogame to the principles of motor learning and the characteristics of users with CP, and (2) piloting the effectiveness of these adaptations by analyzing the achievement of motor learning parameters (learning rate acquisition, retention, and transfer to motor and somatosensory function). Materials and Methods: Periodical interprofessional meetings conducted to the adaptation of a videogame, requiring the control of a joystick for traveling through a maze, to motor learning principles. In a pilot validation, effects in unilateral upper limb function, gross manual dexterity, and somatosensory thresholds were assessed before and after 10-week training in 13 children with CP. Results: After 10-week training with the adapted serious game, children showed learning rates above 90% and improvement in motor learning parameters along the sessions. Manual dexterity and pronation-supination of the dominant hand improved after training. No significant effects were found on somatosensory thresholds. Conclusion: Serious games are useful as motor learning tools for improving motor function in children with PC. Cooperative work among professionals and users is advisable for designing efficient videogames according to rehabilitation best practices.

Alterations in learning-related cortical activation and functional connectivity by high-definition transcranial direct current stimulation after stroke: an fNIRS study

Introduction

Motor learning is a key component of stroke neurorehabilitation. High-definition transcranial direct current stimulation (HD-tDCS) was recently developed as a tDCS technique that increases the accuracy of current delivery to the brain using arrays of small electrodes. The purpose of this study was to investigate whether HD-tDCS alters learning-related cortical activation and functional connectivity in stroke patients using functional near-infrared spectroscopy (fNIRS).

Methods

Using a sham-controlled crossover study design, 16 chronic stroke patients were randomly assigned to one of two intervention conditions. Both groups performed the sequential finger tapping task (SFTT) on five consecutive days, either with (a) real HD-tDCS or (b) with sham HD-tDCS. HD-tDCS (1 mA for 20 min, 4 × 1) was administered to C3 or C4 (according to lesion side). fNIRS signals were measured during the SFTT with the affected hand before (baseline) and after each intervention using fNIRS measurement system. Cortical activation and functional connectivity of NIRS signals were analyzed using a statistical parametric mapping open-source software package (NIRS-SPM), OptoNet II^®.

Results

In the real HD-tDCS condition, oxyHb concentration increased significantly in the ipsilesional primary motor cortex (M1). Connectivity between the ipsilesional M1 and the premotor cortex (PM) was noticeably strengthened after real HD-tDCS compared with baseline. Motor performance also significantly improved, as shown in response time during the SFTT. In the sham HD-tDCS condition, functional connectivity between contralesional M1 and sensory cortex was enhanced compared with baseline. There was tendency toward improvement in SFTT response time, but without significance.

Discussion

The results of this study indicated that HD-tDCS could modulate learning-related cortical activity and functional connectivity within motor networks to enhance motor learning performance. HD-tDCS can be used as an additional tool for enhancing motor learning during hand rehabilitation for chronic stroke patients.

Modulating motor learning with brain stimulation: Stage-specific perspectives for transcranial and transcutaneous delivery

Brain stimulation has been used in motor learning studies with success in improving aspects of task learning, retention, and consolidation. Using a variety of motor tasks and stimulus parameters, researchers have produced an array of literature supporting the efficacy of brain stimulation to modulate motor task learning. We discuss the use of transcranial direct current stimulation, transcranial alternating current stimulation, and peripheral nerve stimulation to modulate motor learning. In a novel approach, we review literature of motor learning modulation in terms of learning stage, categorizing learning into acquisition, consolidation, and retention. We endeavour to provide a current perspective on the stage-specific mechanism behind modulation of motor task learning, to give insight into how electrical stimulation improves or hinders motor learning, and how mechanisms differ depending on learning stage. Offering a look into the effectiveness of peripheral nerve stimulation for motor learning, we include potential mechanisms and overlapping features with transcranial stimulation. We conclude by exploring how peripheral stimulation may contribute to the results of studies that employed brain stimulation intracranially.

Bilateral Transfer of Performance between Real and Non-Immersive Virtual Environments in Post-Stroke Individuals: A Cross-Sectional Study

(1) Background: Post-stroke presents motor function deficits, and one interesting possibility for practicing skills is the concept of bilateral transfer. Additionally, there is evidence that the use of virtual reality is beneficial in improving upper limb function. We aimed to evaluate the transfer of motor performance of post-stroke and control groups in two different environments (real and virtual), as well as bilateral transfer, by changing the practice between paretic and non-paretic upper limbs. (2) Methods: We used a coincident timing task with a virtual (Kinect) or a real device (touch screen) in post-stroke and control groups; both groups practiced with bilateral transference. (3) Results: Were included 136 participants, 82 post-stroke and 54 controls. The control group presented better performance during most parts of the protocol; however, it was more evident when compared with the post-stroke paretic upper limb. We found bilateral transference mainly in Practice 2, with the paretic upper limb using the real interface method (touch screen), but only after Practice 1 with the virtual interface (Kinect), using the non-paretic upper limb. (4) Conclusions: The task with the greatest motor and cognitive demand (virtual-Kinect) provided transfer into the real interface, and bilateral transfer was observed in individuals post-stroke. However, this is more strongly observed when the virtual task was performed using the non-paretic upper limb first.

Addressing the inconsistent electric fields of tDCS by using patient-tailored configurations in chronic stroke: Implications for treatment

Transcranial direct current stimulation (tDCS) is a promising tool to improve and speed up motor rehabilitation after stroke, but inconsistent clinical effects refrain tDCS from clinical implementation. Therefore, this study aimed to assess the need for individualized tDCS configurations in stroke, considering interindividual variability in brain anatomy and motor function representation. We simulated tDCS in individualized MRI-based finite element head models of 21 chronic stroke subjects and 10 healthy age-matched controls. An anatomy-based stimulation target, i.e. the motor hand knob, was identified with MRI, whereas a motor function-based stimulation target was identified with EEG. For each subject, we simulated conventional anodal tDCS electrode configurations and optimized electrode configurations to maximize stimulation strength within the anatomical and functional target. The normal component of the electric field was extracted and compared between subjects with stroke and healthy, age-matched controls, for both targets, during conventional and optimized tDCS. Electrical field strength was significantly lower, more variable and more frequently in opposite polarity for subjects with stroke compared to healthy age-matched subjects, both for the anatomical and functional target with conventional, i.e. non-individualized, electrode configurations. Optimized, i.e. individualized, electrode configurations increased the electrical field strength in the anatomical and functional target for subjects with stroke but did not reach the same levels as in healthy subjects. Considering individual brain structure and motor function is crucial for applying tDCS in subjects with stroke. Lack of individualized tDCS configurations in subjects with stroke results in lower electric fields in stimulation targets, which may partially explain the inconsistent clinical effects of tDCS in stroke trials.

Bimanual motor skill learning after stroke: Combining robotics and anodal tDCS over the undamaged hemisphere: An exploratory study

Background

Since a stroke can impair bimanual activities, enhancing bimanual cooperation through motor skill learning may improve neurorehabilitation. Therefore, robotics and neuromodulation with transcranial direct current stimulation (tDCS) are promising approaches. To date, tDCS has failed to enhance bimanual motor control after stroke possibly because it was not integrating the hypothesis that the undamaged hemisphere becomes the major poststroke hub for bimanual control.

Objective

We tested the following hypotheses: (I) In patients with chronic hemiparetic stroke training on a robotic device, anodal tDCS applied over the primary motor cortex of the undamaged hemisphere enhances bimanual motor skill learning compared to sham tDCS. (II) The severity of impairment correlates with the effect of tDCS on bimanual motor skill learning. (III) Bimanual motor skill learning is less efficient in patients than in healthy individuals (HI).

Methods

A total of 17 patients with chronic hemiparetic stroke and 7 healthy individuals learned a complex bimanual cooperation skill on the REAplan® neurorehabilitation robot. The bimanual speed/accuracy trade-off (biSAT), bimanual coordination (biCo), and bimanual force (biFOP) scores were computed for each performance. In patients, real/sham tDCS was applied in a crossover, randomized, double-blind approach.

Results

Compared to sham, real tDCS did not enhance bimanual motor skill learning, retention, or generalization in patients, and no correlation with impairment was noted. The healthy individuals performed better than patients on bimanual motor skill learning, but generalization was similar in both groups.

Conclusion

A short motor skill learning session with a robotic device resulted in the retention and generalization of a complex skill involving bimanual cooperation. The tDCS strategy that would best enhance bimanual motor skill learning after stroke remains unknown.

Clinical trial registration

https://clinicaltrials.gov/ct2/show/NCT02308852, identifier: NCT02308852.

Assessing Impairments in Visuomotor Adaptation After Stroke

Background:

Motor impairment in the arms is common after stroke and many individuals participate in therapy to improve function. It is assumed that individuals with stroke can adapt and improve their movements using feedback that arises from movement or is provided by a therapist. Here we investigated visuomotor adaptation in individuals with sub-acute and chronic stroke.

Objective:

We examined the impact of the stroke-affected arm (dominant or non-dominant), time post-stroke, and relationships with clinical measures of motor impairment and functional independence.

Methods:

Participants performed reaching movements with their arm supported in a robotic exoskeleton. We rotated the relationship between the motion of the participant’s hand and a feedback cursor displayed in their workspace. Outcome measures included the amount that participants adapted their arm movements and the number of trials they required to adapt.

Results:

Participants with stroke (n = 36) adapted less and required more trials to adapt than controls (n = 29). Stroke affecting the dominant arm impaired the amount of adaptation more than stroke affecting the non-dominant arm. Overall, 53% of participants with stroke were impaired in one or more measures of visuomotor adaptation. Initial adaptation was weakly correlated with time post-stroke, and the amount of adaptation correlated moderately with clinical measures of motor impairment and functional independence.

Conclusion:

Our findings reveal impairments in visuomotor adaptation that are associated with motor impairment and function after stroke. Longitudinal studies are needed to understand the relationship between adaptation and recovery attained in a therapy setting.

A randomized sham-controlled trial on the effects of dual-tDCS "during" physical therapy on lower limb performance in sub-acute stroke and a comparison to the previous study using a "before" stimulation protocol

Background

Dual-transcranial direct current stimulation (tDCS) has been used to rebalance the cortical excitability of both hemispheres following unilateral-stroke. Our previous study showed a positive effect from a single-session of dual-tDCS applied before physical therapy (PT) on lower limb performance. However, it is still undetermined if other timings of brain stimulation (i.e., during motor practice) induce better effects. The objective of this study was to examine the effect of a single-session of dual-tDCS “during” PT on lower limb performance in sub-acute stroke and then compare the results with our previous data using a “before” stimulation paradigm.

Method

For the current “during” protocol, 19 participants were participated in a randomized sham-controlled crossover trial. Dual-tDCS over the M1 of both cortices (2 mA) was applied during the first 20 min of PT. The Timed Up and Go and Five-Times-Sit-To-Stand tests were assessed at pre- and post-intervention and 1-week follow-up. Then, data from the current study were compared with those of the previous “before” study performed in a different group of 19 subjects. Both studies were compared by the difference of mean changes from the baseline.

Results

Dual-tDCS “during” PT and the sham group did not significantly improve lower limb performance. By comparing with the previous data, performance in the “before” group was significantly greater than in the “during” and sham groups at post-intervention, while at follow-up the “before” group had better improvement than sham, but not greater than the “during” group.

Conclusion

A single-session of dual-tDCS during PT induced no additional advantage on lower limb performance. The “before” group seemed to induce better acute effects; however, the benefits of the after-effects on motor learning for both stimulation protocols were probably not different.

Trial registration Current randomized controlled trials was prospectively registered at the clinicaltrials.gov, registration number: NCT04051671. The date of registration was 09/08/2019.

Efficiency and usability of a modified pegboard incorporating computerized technology for upper limb rehabilitation in patients with stroke

BACKGROUND

Traditionally, a pegboard has been commonly used as a useful training and assessment tool for patients with stroke. However, training using pegboards could be monotonous and may discourage motivation in patients with stroke, as it requires only repetitive movements without feedback.

OBJECTIVES

We aimed to demonstrate the efficiency and usability of a novel rehabilitation instrument (Rapael Smart Pegboard; SP), which integrates computerized technology into a traditional pegboard.

METHODS

This single-center study with a single-group pre-post design included 19 patients with hemiplegic stroke (11 outpatients and 8 inpatients). The patients received 20 SP training sessions (30 minutes per session, 5 days per week, over 4 weeks) according to their ability and status without any therapist intervention. The primary outcome was changes in the Fugl-Meyer assessment of upper extremity (FMA), and the secondary outcomes were changes in the Box and Block test and Jebsen-Taylor Hand Function test (JHFT). Additionally, usability assessment was performed.

RESULTS

All outcome measurements except JHFT-gross score showed significant improvements with SP training. The significant improvements in these outcomes were consistently found in the outpatient group; however, the inpatient group failed to show improvement in the distal part of FMA, total JHFT score, and time. The usability test showed high satisfaction with 4.9 out of 5 points.

CONCLUSIONS

The SP is an effective and feasible instrument for upper limb rehabilitation. Moreover, the SP can be used as a self-training tool without the assistance of a health care practitioner.

Evidence of Motor Skill Learning in Acute Stroke Patients Without Lesions to the Thalamus and Internal Capsule

Background:

It is currently unknown whether motor skill learning (MSkL) with the paretic upper limb is possible during the acute phase after stroke and whether lesion localization impacts MSkL. Here, we investigated MSkL in acute (1–7 days post) stroke patients compared with healthy individuals (HIs) and in relation to voxel-based lesion symptom mapping.

Methods:

Twenty patients with acute stroke and 35 HIs were trained over 3 consecutive days on a neurorehabilitation robot measuring speed, accuracy, and movement smoothness variables. Patients used their paretic upper limb and HI used their nondominant upper limb on an MSkL task involving a speed/accuracy trade-off. Generalization was evaluated on day 3. All patients underwent a 3-dimensional magnetic resonance imaging used for VSLM.

Results:

Most patients achieved MSkL demonstrated by day-to-day retention and generalization of the newly learned skill on day 3. When comparing raw speed/accuracy trade-off values, HI achieved larger MSkL than patients. However, relative speed/accuracy trade-off values showed no significant differences in MSkL between patients and HI on day 3. In patients, MSkL progression correlated with acute motor and cognitive impairments. The voxel-based lesion symptom mapping showed that acute vascular damage to the thalamus or the posterior limb of the internal capsule reduced MSkL.

Conclusions:

Despite worse motor performance for acute stroke patients compared with HI, most patients were able to achieve MSkL with their paretic upper limb. Damage to the thalamus and posterior limb of the internal capsule, however, reduced MSkL. These data show that MSkL could be implemented into neurorehabilitation during the acute phase of stroke, particularly for patients without lesions to the thalamus and posterior limb of the internal capsule.

Registration:

URL: https://www.clinicaltrials.gov ; Unique identifier: NCT01519843.

Bimanual motor skill learning with robotics in chronic stroke: comparison between minimally impaired and moderately impaired patients, and healthy individuals

BACKGROUND

Most activities of daily life (ADL) require cooperative bimanual movements. A unilateral stroke may severely impair bimanual ADL. How patients with stroke (re)learn to coordinate their upper limbs (ULs) is largely unknown. The objectives are to determine whether patients with chronic supratentorial stroke could achieve bimanual motor skill learning (bim-MSkL) and to compare bim-MSkL between patients and healthy individuals (HIs).

METHODS

Twenty-four patients and ten HIs trained over 3 consecutive days on an asymmetrical bimanual coordination task (CIRCUIT) implemented as a serious game in the REAplan® robot. With a common cursor controlled by coordinated movements of the ULs through robotic handles, they performed as many laps as possible (speed constraint) on the CIRCUIT while keeping the cursor within the track (accuracy constraint). The primary outcome was a bimanual speed/accuracy trade-off (biSAT), we used a bimanual coordination factor (biCO) and bimanual forces (biFOP) for the secondary outcomes. Several clinical scales were used to evaluate motor and cognitive functions.

RESULTS

Overall, the patients showed improvements on biSAT and biCO. Based on biSAT progression, the HI achieved a larger bim-MSkL than the patients with mild to moderate impairment (Fugl-Meyer Assessment Upper Extremity (FMA-UE): 28-55, n = 15) but not significantly different from those with minimal motor impairment (FMA-UE: 66, n = 9). There was a significant positive correlation between biSAT evolution and the FMA-UE and Stroke Impact Scale.

CONCLUSIONS

Both HI and patients with chronic stroke training on a robotic device achieved bim-MSkL, although the more impaired patients were less efficient. Bim-MSkL with REAplan® may be interesting for neurorehabilitation after stroke.

TRIAL REGISTRATION

ClinicalTrial.gov identifier: NCT03974750. Registered 05 June 2019. https://clinicaltrials.gov/ct2/show/NCT03974750?cond=NCT03974750&draw=2&rank=1.

The effect of transcranial direct current stimulation on cognitive performance in youth with persistent cognitive symptoms following concussion: a controlled pilot study

OBJECTIVE

Explore the feasibility, tolerability, and early efficacy of transcranial direct current stimulation (tDCS) as a therapeutic intervention for youth with cognitive persistent post-concussion symptoms (PPCS).

HYPOTHESIS

tDCS improves performance on a dual task working memory (WM) paradigm in youth with cognitive PPCS.

PARTICIPANTS

Twelve youth experiencing cognitive PPCS.

DESIGN

A quasi-randomized pilot trial was used to explore the tolerability of, and performance differences on, a dual N-Back WM task paired with active or sham tDCS over 3 sessions.

MEASURES

Accuracy and reaction time on WM task and self-report of tDCS tolerability.

RESULTS

Trends toward increases in accuracy from Day 1 to 3 seen in both groups. Active tDCS group performed better than sham on Day 2 in N-Back level N2 (p = .019), and marginally better than the sham group on Day 3 in level N3 (p = .26). Participants reported tDCS as tolerable; compared to the active tDCS group, the sham group reported more "considerable" (p = .078) and "strong" symptoms (p = .097).

CONCLUSION

tDCS is a promising tool for enhancing WM performance and is a feasible and tolerable adjunct to behavioral interventions in youth with cognitive PPCS. A clinical trial to demonstrate efficacy is warranted.

Targeting Sensory and Motor Integration for Recovery of Movement After CNS Injury

The central nervous system (CNS) integrates sensory and motor information to acquire skilled movements, known as sensory-motor integration (SMI). The reciprocal interaction of the sensory and motor systems is a prerequisite for learning and performing skilled movement. Injury to various nodes of the sensorimotor network causes impairment in movement execution and learning. Stimulation methods have been developed to directly recruit the sensorimotor system and modulate neural networks to restore movement after CNS injury. Part 1 reviews the main processes and anatomical interactions responsible for SMI in health. Part 2 details the effects of injury on sites critical for SMI, including the spinal cord, cerebellum, and cerebral cortex. Finally, Part 3 reviews the application of activity-dependent plasticity in ways that specifically target integration of sensory and motor systems. Understanding of each of these components is needed to advance strategies targeting SMI to improve rehabilitation in humans after injury.

Dual-Hemisphere Transcranial Direct Current Stimulation on Parietal Operculum Does Not Affect the Programming of Intra-limb Anticipatory Postural Adjustments

Evidence shows that the postural and focal components within the voluntary motor command are functionally unique. In 2015, we reported that the supplementary motor area (SMA) processes Anticipatory Postural Adjustments (APAs) separately from the command to focal muscles, so we are still searching for a hierarchically higher area able to process both components. Among these, the parietal operculum (PO) seemed to be a good candidate, as it is a hub integrating both sensory and motor streams. However, in 2019, we reported that transcranial Direct Current Stimulation (tDCS), applied with an active electrode on the PO contralateral to the moving segment vs. a larger reference electrode on the opposite forehead, did not affect intra-limb APAs associated to brisk flexions of the index-finger. Nevertheless, literature reports that two active electrodes of opposite polarities, one on each PO (dual-hemisphere, dh-tDCS), elicit stronger effects than the "active vs. reference" arrangement. Thus, in the present study, the same intra-limb APAs were recorded before, during and after dh-tDCS on PO. Twenty right-handed subjects were tested, 10 for each polarity: anode on the left vs. cathode on the right, and vice versa. Again, dh-tDCS was ineffective on APA amplitude and timing, as well as on prime mover recruitment and index-finger kinematics. These results confirm the conclusion that PO does not take part in intra-limb APA control. Therefore, our search for an area in which the motor command to prime mover and postural muscles are still processed together will have to address other structures.

Effectiveness of a combined transcranial direct current stimulation and virtual reality-based intervention on upper limb function in chronic individuals post-stroke with persistent severe hemiparesis: a randomized controlled trial

BACKGROUND

Functional impairments derived from the non-use of severely affected upper limb after stroke have been proposed to be mitigated by action observation and imagination-based techniques, whose effectiveness is enhanced when combined with transcranial direct current stimulation (tDCS). Preliminary studies in mildly impaired individuals in the acute phase post-stroke show intensified effects when action is facilitated by tDCS and mediated by virtual reality (VR) but the effectiveness in cases of severe impairment and chronic stroke is unknown. This study investigated the effectiveness of a combined tDCS and VR-based intervention in the sensorimotor function of chronic individuals post-stroke with persistent severe hemiparesis compared to conventional physical therapy.

METHODS

Twenty-nine participants were randomized into an experimental group, who received 30 minutes of the combined tDCS and VR-based therapy and 30 minutes of conventional physical therapy, or a control group, who exclusively received conventional physical therapy focusing on passive and active assistive range of motion exercises. The sensorimotor function of all participants was assessed before and after 25 one-hour sessions, administered three to five times a week, using the upper extremity subscale of the Fugl-Meyer Assessment, the time and ability subscales of the Wolf Motor Function Test, and the Nottingham Sensory Assessment.

RESULTS

A clinically meaningful improvement of the upper limb motor function was consistently revealed in all motor measures after the experimental intervention, but not after conventional physical therapy. Similar limited effects were detected in the sensory function in both groups.

CONCLUSION

The combined tDCS and VR-based paradigm provided not only greater but also clinically meaningful improvement in the motor function (and similar sensory effects) in comparison to conventional physical therapy.

Study Paradigms and Principles Investigated in Motor Learning Research After Stroke: A Scoping Review

OBJECTIVES

To (1) characterize study paradigms used to investigate motor learning (ML) poststroke and (2) summarize the effects of different ML principles in promoting skill acquisition and retention. Our secondary objective is to evaluate the clinical utility of ML principles on stroke rehabilitation.

DATA SOURCES

Medline, Excerpta Medica Database, Allied and Complementary Medicine, Cumulative Index to Nursing and Allied Health Literature, and Cochrane Central Register of Controlled Trials were searched from inception on October 24, 2018 and repeated on June 23, 2020. Scopus was searched on January 24, 2019 and July 22, 2020 to identify additional studies.

STUDY SELECTION

Our search included keywords and concepts to represent stroke and "motor learning. An iterative process was used to generate study selection criteria. Three authors independently completed title, abstract, and full-text screening.

DATA EXTRACTION

Three reviewers independently completed data extraction.

DATA SYNTHESIS

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension guidelines for scoping reviews were used to guide our synthesis. Thirty-nine studies were included. Study designs were heterogeneous, including variability in tasks practiced, acquisition parameters, and retention intervals. ML principles investigated included practice complexity, feedback, motor imagery, mental practice, action observation, implicit and explicit information, aerobic exercise, and neurostimulation. An additional 2 patient-related factors that influence ML were included: stroke characteristics and sleep. Practice complexity, feedback, and mental practice/action observation most consistently promoted ML, while provision of explicit information and more severe strokes were detrimental to ML. Other factors (ie, sleep, practice structure, aerobic exercise, neurostimulation) had a less clear influence on learning.

CONCLUSIONS

Improved consistency of reporting in ML studies is needed to improve study comparability and facilitate meta-analyses to better understand the influence of ML principles on learning poststroke. Knowledge of ML principles and patient-related factors that influence ML, with clinical judgment can guide neurologic rehabilitation delivery to improve patient motor outcomes.

Chronic nicotine impairs sparse motor learning via striatal fast-spiking parvalbumin interneurons

Nicotine can diversely affect neural activity and motor learning in animals. However, the impact of chronic nicotine on striatal activity in vivo and motor learning at long-term sparse timescale remains unknown. Here, we demonstrate that chronic nicotine persistently suppresses the activity of striatal fast-spiking parvalbumin interneurons, which mediate nicotine-induced deficit in sparse motor learning. Six weeks of longitudinal in vivo single-unit recording revealed that mice show reduced activity of fast-spiking interneurons in the dorsal striatum during chronic nicotine exposure and withdrawal. The reduced firing of fast-spiking interneurons was accompanied by spike broadening, diminished striatal delta oscillation power, and reduced sample entropy in local field potential. In addition, chronic nicotine withdrawal impaired motor learning with a weekly sparse training regimen but did not affect general locomotion and anxiety-like behavior. Lastly, the excitatory DREADD hM3Dq-mediated activation of striatal fast-spiking parvalbumin interneurons reversed the chronic nicotine withdrawal-induced deficit in sparse motor learning. Taken together, we identified that chronic nicotine withdrawal impairs sparse motor learning via disruption of activity in striatal fast-spiking parvalbumin interneurons. These findings suggest that sparse motor learning paradigm can reveal the subtle effect of nicotine withdrawal on motor function and that striatal fast-spiking parvalbumin interneurons are a neural substrate of nicotine's effect on motor learning.

Evidence-Based Guidelines and Secondary Meta-Analysis for the Use of Transcranial Direct Current Stimulation in Neurological and Psychiatric Disorders

BACKGROUND

Transcranial direct current stimulation has shown promising clinical results, leading to increased demand for an evidence-based review on its clinical effects.

OBJECTIVE

We convened a team of transcranial direct current stimulation experts to conduct a systematic review of clinical trials with more than 1 session of stimulation testing: pain, Parkinson's disease motor function and cognition, stroke motor function and language, epilepsy, major depressive disorder, obsessive compulsive disorder, Tourette syndrome, schizophrenia, and drug addiction.

METHODS

Experts were asked to conduct this systematic review according to the search methodology from PRISMA guidelines. Recommendations on efficacy were categorized into Levels A (definitely effective), B (probably effective), C (possibly effective), or no recommendation. We assessed risk of bias for all included studies to confirm whether results were driven by potentially biased studies.

RESULTS

Although most of the clinical trials have been designed as proof-of-concept trials, some of the indications analyzed in this review can be considered as definitely effective (Level A), such as depression, and probably effective (Level B), such as neuropathic pain, fibromyalgia, migraine, post-operative patient-controlled analgesia and pain, Parkinson's disease (motor and cognition), stroke (motor), epilepsy, schizophrenia, and alcohol addiction. Assessment of bias showed that most of the studies had low risk of biases, and sensitivity analysis for bias did not change these results. Effect sizes vary from 0.01 to 0.70 and were significant in about 8 conditions, with the largest effect size being in postoperative acute pain and smaller in stroke motor recovery (nonsignificant when combined with robotic therapy).

CONCLUSION

All recommendations listed here are based on current published PubMed-indexed data. Despite high levels of evidence in some conditions, it must be underscored that effect sizes and duration of effects are often limited; thus, real clinical impact needs to be further determined with different study designs.

The Effects of 10 Hz and 20 Hz tACS in Network Integration and Segregation in Chronic Stroke: A Graph Theoretical fMRI Study

Transcranial alternating current stimulation (tACS) has emerged as a promising technique to non-invasively modulate the endogenous oscillations in the human brain. Despite its clinical potential to be applied in routine rehabilitation therapies, the underlying modulation mechanism has not been thoroughly understood, especially for patients with neurological disorders, including stroke. In this study, we aimed to investigate the frequency-specific stimulation effect of tACS in chronic stroke. Thirteen chronic stroke patients underwent tACS intervention, while resting-state functional magnetic resonance imaging (fMRI) data were collected under various frequencies (sham, 10 Hz and 20 Hz). The graph theoretical analysis indicated that 20 Hz tACS might facilitate local segregation in motor-related regions and global integration at the whole-brain level. However, 10 Hz was only observed to increase the segregation from whole-brain level. Additionally, it is also observed that, for the network in motor-related regions, the nodal clustering characteristic was decreased after 10 Hz tACS, but increased after 20 Hz tACS. Taken together, our results suggested that tACS in various frequencies might induce heterogeneous modulation effects in lesioned brains. Specifically, 20 Hz tACS might induce more modulation effects, especially in motor-related regions, and they have the potential to be applied in rehabilitation therapies to facilitate neuromodulation. Our findings might shed light on the mechanism of neural responses to tACS and facilitate effectively designing stimulation protocols with tACS in stroke in the future.

From adults to pediatrics: A review noninvasive brain stimulation (NIBS) to facilitate recovery from brain injury

Stroke is a major problem worldwide that impacts over 100 million adults and children annually. Rehabilitation therapy is the current standard of care to restore functional impairments post-stroke, however its effects are limited and many patients suffer persisting functional impairments and life-long disability. Noninvasive Brain Stimulation (NIBS) has emerged as a potential rehabilitation treatment option in both adults and children with brain injury. In the last decade, Transcranial Magnetic Stimulation (TMS), Transcranial Direct Current Stimulation (tDCS) and Transcutaneous Auricular Vagus Nerve Stimulation (taVNS) have been investigated to improve motor recovery in adults post-stroke. These promising adult findings using NIBS, however, have yet to be widely translated to the area of pediatrics. The limited studies exploring NIBS in children have demonstrated safety, feasibility, and utility of stimulation-augmented rehabilitation. This chapter will describe the mechanism of NIBS therapy (cortical excitability, neuroplasticity) that underlies its use in stroke and motor function and how TMS, tDCS, and taVNS are applied in adult stroke treatment paradigms. We will then discuss the current state of NIBS in early pediatric brain injury and will provide insight regarding practical considerations and future applications of NIBS in pediatrics to make this promising treatment option a viable therapy in children.

Robotic Assessment of Upper Limb Function in a Nonhuman Primate Model of Chronic Stroke

Stroke is a leading cause of death and disability worldwide and survivors are frequently left with long-term disabilities that diminish their autonomy and result in the need for chronic care. There is an urgent need for the development of therapies that improve stroke recovery, as well as accurate and quantitative tools to measure function. Nonhuman primates closely resemble humans in neuroanatomy and upper limb function and may be crucial in randomized pre-clinical trials for testing the efficacy of stroke therapies. To test the feasibility of robotic assessment of motor function in a NHP model of stroke, two cynomolgus macaques were trained to perform a visually guided reaching task and were also assessed in a passive stretch task using the Kinarm robot. Strokes were then induced in these animals by transiently occluding the middle cerebral artery, and their motor performance on the same tasks was assessed after recovery. Relative to pre-stroke performance, post-stroke hand movements of the affected limb became slower and less accurate. Regression analyses revealed both recovered and compensatory movements to complete movements in different spatial directions. Lastly, we noted decreased range of motion in the elbow joint of the affected limb post-stroke associated with spasticity during passive stretch. Taken together, these studies highlight that sensorimotor deficits in reaching movements following stroke in cynomolgus macaques resemble those in human patients and validate the use of robotic assessment tools in a nonhuman primate model of stroke for identifying and characterizing such deficits.

Corticospinal and spinal adaptations to motor skill and resistance training: Potential mechanisms and implications for motor rehabilitation and athletic development

Optimal strategies for enhancing strength and improving motor skills are vital in athletic performance and clinical rehabilitation. Initial increases in strength and the acquisition of new motor skills have long been attributed to neurological adaptations. However, early increases in strength may be predominantly due to improvements in inter-muscular coordination rather than the force-generating capacity of the muscle. Despite the plethora of research investigating neurological adaptations from motor skill or resistance training in isolation, little effort has been made in consolidating this research to compare motor skill and resistance training adaptations. The findings of this review demonstrated that motor skill and resistance training adaptations show similar short-term mechanisms of adaptations, particularly at a cortical level. Increases in corticospinal excitability and a release in short-interval cortical inhibition occur as a result of the commencement of both resistance and motor skill training. Spinal changes show evidence of task-specific adaptations from the acquired motor skill, with an increase or decrease in spinal reflex excitability, dependant on the motor task. An increase in synaptic efficacy of the reticulospinal projections is likely to be a prominent mechanism for driving strength adaptations at the subcortical level, though more research is needed. Transcranial electric stimulation has been shown to increase corticospinal excitability and augment motor skill adaptations, but limited evidence exists for further enhancing strength adaptations from resistance training. Despite the logistical challenges, future work should compare the longitudinal adaptations between motor skill and resistance training to further optimise exercise programming.

The Effect of Parietal and Cerebellar Transcranial Direct Current Stimulation on Bimanual Coordinated Adaptive Motor Learning

Abstract. Many daily activities, such as typing, eating, playing the piano, and passing the ball in volleyball, require the proficient coordination of both hands. In this study, the effects of anodal transcranial direct current stimulation (atDCS) on the acquisition, retention, and transfer of bimanual adaptive motor tasks were investigated. To this end, 64 volunteers ( Mage = 24.36 years; SD = 2.51; 16 females) participated in this double-blind study and were categorized randomly into 4 groups. During the pretest, posttest, 24-h and 48-h retention, and transfer tests, two forms of bimanual coordination (BC) of the Vienna test system were performed. Between the pretest and posttest, all participants were trained in a bimanual coordination adaptive task with concurrent brain stimulation (1.5 mA for 15 min) for two consecutive days. The first experimental group (parietal-stim) received atDCS over the right parietal cortex (P4), while the second experimental group (cerebellar-stim) received atDCS over the bilateral cerebellum (2.5 cm bilateral to the inion). The third group (sham) received a sham stimulation. Finally, the control group did not receive any stimulation at all (control). Repeated-measure analysis of variance (ANOVARM) results indicated that parietal tDCS affected motor performance in the posttest, while overall mean duration and overall error mean duration of movement decreased. The results also revealed a significant impact of cerebellar tDCS on the posttest, 24-h and 48-h retention, and transfer tests. The overall mean duration and overall error mean durations of movement in this group were significantly lower than those in the other groups. Accordingly, we found evidence that atDCS over the cerebellum leads to more improvement in motor performance and transfer in a bimanual coordination task than atDCS over the right parietal. Finally, these results point to the possibly beneficial application of atDCS for learning and recovery of bimanual motor skills, especially when subjects are faced with a new challenging situation.

Transcranial direct current stimulation (tDCS) for improving activities of daily living, and physical and cognitive functioning, in people after stroke

BACKGROUND

Stroke is one of the leading causes of disability worldwide. Functional impairment, resulting in poor performance in activities of daily living (ADL) among stroke survivors is common. Current rehabilitation approaches have limited effectiveness in improving ADL performance, function, muscle strength, and cognitive abilities (including spatial neglect) after stroke, with improving cognition being the number one research priority in this field. A possible adjunct to stroke rehabilitation might be non-invasive brain stimulation by transcranial direct current stimulation (tDCS) to modulate cortical excitability, and hence to improve these outcomes in people after stroke.

OBJECTIVES

To assess the effects of tDCS on ADL, arm and leg function, muscle strength and cognitive abilities (including spatial neglect), dropouts and adverse events in people after stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register, CENTRAL, MEDLINE, Embase and seven other databases in January 2019. In an effort to identify further published, unpublished, and ongoing trials, we also searched trials registers and reference lists, handsearched conference proceedings, and contacted authors and equipment manufacturers.

SELECTION CRITERIA

This is the update of an existing review. In the previous version of this review, we focused on the effects of tDCS on ADL and function. In this update, we broadened our inclusion criteria to compare any kind of active tDCS for improving ADL, function, muscle strength and cognitive abilities (including spatial neglect) versus any kind of placebo or control intervention.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and risk of bias, extracted data, and applied GRADE criteria. If necessary, we contacted study authors to ask for additional information. We collected information on dropouts and adverse events from the trial reports.

MAIN RESULTS

We included 67 studies involving a total of 1729 patients after stroke. We also identified 116 ongoing studies. The risk of bias did not differ substantially for different comparisons and outcomes. The majority of participants had ischaemic stroke, with mean age between 43 and 75 years, in the acute, postacute, and chronic phase after stroke, and level of impairment ranged from severe to less severe. Included studies differed in terms of type, location and duration of stimulation, amount of current delivered, electrode size and positioning, as well as type and location of stroke. We found 23 studies with 781 participants examining the effects of tDCS versus sham tDCS (or any other passive intervention) on our primary outcome measure, ADL after stroke. Nineteen studies with 686 participants reported absolute values and showed evidence of effect regarding ADL performance at the end of the intervention period (standardised mean difference (SMD) 0.28, 95% confidence interval (CI) 0.13 to 0.44; random-effects model; moderate-quality evidence). Four studies with 95 participants reported change scores, and showed an effect (SMD 0.48, 95% CI 0.02 to 0.95; moderate-quality evidence). Six studies with 269 participants assessed the effects of tDCS on ADL at the end of follow-up and provided absolute values, and found improved ADL (SMD 0.31, 95% CI 0.01 to 0.62; moderate-quality evidence). One study with 16 participants provided change scores and found no effect (SMD -0.64, 95% CI -1.66 to 0.37; low-quality evidence). However, the results did not persist in a sensitivity analysis that included only trials with proper allocation concealment. Thirty-four trials with a total of 985 participants measured upper extremity function at the end of the intervention period. Twenty-four studies with 792 participants that presented absolute values found no effect in favour of tDCS (SMD 0.17, 95% CI -0.05 to 0.38; moderate-quality evidence). Ten studies with 193 participants that presented change values also found no effect (SMD 0.33, 95% CI -0.12 to 0.79; low-quality evidence). Regarding the effects of tDCS on upper extremity function at the end of follow-up, we identified five studies with a total of 211 participants (absolute values) without an effect (SMD -0.00, 95% CI -0.39 to 0.39; moderate-quality evidence). Three studies with 72 participants presenting change scores found an effect (SMD 1.07; 95% CI 0.04 to 2.11; low-quality evidence). Twelve studies with 258 participants reported outcome data for lower extremity function and 18 studies with 553 participants reported outcome data on muscle strength at the end of the intervention period, but there was no effect (high-quality evidence). Three studies with 156 participants reported outcome data on muscle strength at follow-up, but there was no evidence of an effect (moderate-quality evidence). Two studies with 56 participants found no evidence of effect of tDCS on cognitive abilities (low-quality evidence), but one study with 30 participants found evidence of effect of tDCS for improving spatial neglect (very low-quality evidence). In 47 studies with 1330 participants, the proportions of dropouts and adverse events were comparable between groups (risk ratio (RR) 1.25, 95% CI 0.74 to 2.13; random-effects model; moderate-quality evidence).  AUTHORS' CONCLUSIONS: There is evidence of very low to moderate quality on the effectiveness of tDCS versus control (sham intervention or any other intervention) for improving ADL outcomes after stroke. However, the results did not persist in a sensitivity analyses including only trials with proper allocation concealment. Evidence of low to high quality suggests that there is no effect of tDCS on arm function and leg function, muscle strength, and cognitive abilities in people after stroke. Evidence of very low quality suggests that there is an effect on hemispatial neglect. There was moderate-quality evidence that adverse events and numbers of people discontinuing the treatment are not increased. Future studies should particularly engage with patients who may benefit the most from tDCS after stroke, but also should investigate the effects in routine application. Therefore, further large-scale randomised controlled trials with a parallel-group design and sample size estimation for tDCS are needed.

Breaking the ice to improve motor outcomes in patients with chronic stroke: a retrospective clinical study on neuromodulation plus robotics

BACKGROUND

Stroke is one of the main causes of impairment affecting daily activities and quality of life. There is a growing effort to potentiate the recovery of functional gait and to enable stroke patients to walk independently.

AIM

To estimate the effects of dual-site transcranial direct current stimulation (dstDCS) on gait recovery in chronic stroke patients provided with robot-aided gait training (RAGT).

METHODS

Thirty-seven patients were included in this retrospective clinical study. Nine patients were provided with dstDCS during the first 10 min of RAGT by using Lokomat®Pro (on-RAGT), 15 patients immediately after RAGT (post-RAGT), and 13 patients immediately before RAGT (pre-RAGT).

RESULTS

Each group improved over time concerning disability burden and lower limb strength. on-RAGT and post-RAGT experienced better improvement in balance (p < 0.001) and, moderately, gait endurance (p = 0.04) as compared to pre-RAGT. Furthermore, all treatments decreased the facilitation of the unaffected hemisphere (p < 0.001) and the inhibition of the affected hemisphere (p < 0.001). The duration of such aftereffects was found to be greater for post-RAGT.

DISCUSSION AND CONCLUSION

This is the first trial with dstDCS coupled with RAGT in chronic stroke patients with gait impairment. When timely coupled with RAGT, dstDCS may be considered an effective tool for the recovery of lower limb function in patients with first unilateral stroke in the chronic phase. Moreover, our data suggest the ductility of dstDCS concerning RAGT timing, thus making this intervention suitable in a neurorehabilitation setting and well adaptable to patients' needs.

Effects of exergames training on postural balance in patients who had a chronic stroke: study protocol for a randomised controlled trial

INTRODUCTION

Exergames training, as an additional therapy to standard care, has been widely used for motor recovery after patients who had a stroke, and it is a valuable and positive tool in the rehabilitation of this population. This study describes a single-blind randomised clinical trial that will aim to investigate the effects of exergames training on postural balance in patients with chronic stroke.

METHODS AND ANALYSIS

Forty-two individuals with chronic stroke (>6 months), aged 20-75 years, will be randomised into two groups: the experimental group, which will be subjected to an exergames protocol, and control group, which will undergo a kinesiotherapy protocol. Both protocols are based on postural balance. The intervention will consist of 40-minute sessions two times per week for 10 consecutive weeks. The volunteers will be evaluated before the treatment, at the end of the interventions and 8 weeks thereafter. The primary outcome will be postural balance (Berg Balance Scale, Functional Reach Test, Timed Up and Go test and Centre of Pressure variables) and secondary outcomes will include gait (6 m timed walk and Kinovea Software), cortical activation patterns (electroencephalography Emotiv EPOC), functional independence (Functional Independence Measure), quality of life (Stroke-Specific Quality of Life Scale) and motivation (Intrinsic Motivation Inventory).

ETHICS AND DISSEMINATION

This protocol was approved by the Ethics Committee of the Federal University of Rio Grande do Norte (number 3.434.350). The results of the study will be disseminated to participants through social networks and will be submitted to a peer-reviewed journal and scientific meetings.

TRIAL REGISTRATION NUMBER

Brazilian Registry of Clinical Trials (RBR-78v9hx).

Preserved motor skill learning in acute stroke patients

Recovery is dynamic during acute stroke, but whether new motor skills can be acquired with the paretic upper limb (UL) during this recovery period is unknown. Clarifying this unknown is important, because neurorehabilitation largely relies on motor learning. The aim was to investigate whether, during acute stroke, patients achieved motor skill learning and retention with the paretic UL. Over 3 consecutive days (D1-D3), 14 patients practiced with their paretic UL the CIRCUIT, a motor skill learning task with a speed/accuracy trade-off (SAT). A Learning Index (LI) was used to quantify normalised SAT changes in comparison with baseline. Spontaneous motor recovery was quantified by another task without SAT constraint (EASY), by grip force (GF), and the Box and Blocks test (BBT). In patients, CIRCUIT LI improved 98% ± 66.2 (mean ± SD). This improvement was similar to that of young healthy individuals (n = 30) who trained with a slightly different protocol for 3 consecutive days (83.8% ± 58.8%). Generalisation of SAT gains to an untrained circuit was observed in both groups. From D1 to D3, stroke patients improved their performance on EASY, while changes in GF and BBT were heterogeneous. During acute stroke, patients retained SAT gains for a motor skill learned with the paretic UL in a manner similar to that of healthy individuals. These results demonstrate acute stroke patients achieved motor skill learning and retention that exceeded paretic UL improvements explained by spontaneous recovery.

Transcranial electric stimulation optimizes the balance of visual attention across space

OBJECTIVE

Transcranial direct current stimulation (tDCS) provides a way to modulate spatial attention by enhancing the ratio of neural activity between the left and right hemispheres, with a potential benefit for the rehabilitation of visual neglect.

METHODS

We tested the effect of bilateral tDCS in healthy individuals performing a visual detection task. This protocol consists in the positioning of the anode and cathode on mirror positions over the left and right parietal areas. The stimulation was repeated over three days to maximize the chance to observe a bias to the hemispace controlateral to the anode.

RESULTS

Compared to a sham treatment, left anodal - right cathodal stimulation enhanced attention across the full range of space, since the first day with no build-up effect on the next days, and modified the balance of left-right omissions when stimuli appeared at the same time.

CONCLUSION

Bilateral tDCS improved detection in both visual fields, with no privileged processing of one side, except when concurrent stimuli were presented. The results provide partial support to the hemispheric rivalry hypothesis.

SIGNIFICANCE

The technique has the potential to boost attention in neglect patients but should be used as an adjuvant rather than as an alternative to functional rehabilitation.

Effect of transcranial direct current stimulation and multicomponent training on functional capacity in older adults: protocol for a randomized, controlled, double-blind clinical trial

Introduction

When physical activity contains training of at least three components such as balance, coordination and strength, among others, it is called multicomponent training. This type of training is recommended for improving the functional capacity in elderly individuals but has no lasting effects. The association of transcranial direct current stimulation (tDCS) with other types of therapy has been shown to facilitate the enhancement and prolongation of therapy outcomes.

Aim

The objective of this study is to evaluate the effect of multicomponent training associated with active or sham tDCS on the performance of functional capacity in the elderly before treatment, after treatment and 30 days after the end of treatment. The secondary objective will be to correlate the performance of the primary outcome (functional capacity assessed by the Glittre Daily Life Activity Test) with walking capacity (by 6-min walk test), balance (with the mini-Balance Evaluation Systems Test), functional independence (by the Functional Independence Measure) and quality of life (with the World Health Organization Quality of Life Instrument).

Methods

Twenty-eight elderly people from the community will participate in the study, and will be randomized into two groups: 1) multicomponent training associated with active tDCS; and 2) multicomponent training associated with sham tDCS. The multicomponent training sessions will be held twice a week for 12 weeks, totaling 24 sessions. The tDCS will be administered over the dominant dorsolateral prefrontal cortex at the same time as multicomponent training, with an intensity of 2 mA, for 20 min. The evaluations will be made pretraining, after 24 training sessions and 30 days after the end of the training.

Discussion

We hypothesize that tDCS, when associated with multicomponent training, can potentiate and prolong the effects of this training on the functional capacity of the elderly. If this hypothesis is confirmed, this protocol may contribute to a longer-lasting physical rehabilitation of the elderly, encouraging them to maintain their independent daily activities for longer.

Trial registration

The study was registered in the Brazilian Clinical Trial Registry (RBR-2crd42) and received approval from the Human Research Ethics Committee of University Nove de Julho, São Paulo, Brazil (process number 3.077.953).

The comparative effects of unilateral and bilateral transcranial direct current stimulation on motor learning and motor performance: A systematic review of literature and meta-analysis

Application of unilateral tDCS (Uni-tDCS) vs. bilateral tDCS (Bi-tDCS) is another important factor that can affect the physiological results of tDCS intervention on motor learning and motor performance. According to the evidence, some studies indicated that motor performance or motor learning are facilitated in healthy individuals by application of the Bi-tDCS more than the Uni-tDCS. On the other hand, some studies showed that there was no significant differences between Uni-tDCS and Bi-tDCS; and both techniques were more effective than sham stimulation. In contrast, the other studies have shown more significant effectiveness of Uni-tDCS than Bi-tDCS on motor performance and motor learning. The aim of this study was to systematically review the studies which investigated the effectiveness of Uni-tDCS and Bi-tDCS intervention on the motor learning and motor performance. The search was performed from databases in the Google Scholar, PubMed, Elsevier, Medline, Ovid and Science Direct with the keywords of motor behavior, motor performance, motor learning, Bi-tDCS or bilateral tDCS, dual tDCS, Uni-tDCS or unilateral tDCS, anodal tDCS and cathodal tDCS from 2000 to 2019. The results indicated that the study population was a key factor in determining study's findings. Data meta-analysis showed that Uni-tDCS was more effective than Bi-tDCS in patients with stroke, while, Bi-tDCS was more effective than Uni-tDCS to improve motor learning and motor performance in healthy individuals.

A New Approach to Transcranial Direct Current Stimulation in Improving Cognitive Motor Learning and Hand Function with the Nintendo Switch in Stroke Survivors

BACKGROUND Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation (NIBS) technique designed to improve cognitive and physical function of stroke survivors. There are many studies being conducted in the search for an effective intervention of tDCS. This study focused on cognitive motor learning in relation to hand function of stroke survivors. MATERIAL AND METHODS We enrolled 30 subjects with cognitive and hand function disorders. The participants in each group were inpatients at a hospital in Korea and had undergone neurorehabilitation training (60 min). Groups 1 and 3 had tDCS applied for 20 min, while group 2 received sham tDCS for the same duration. Afterwards, groups 1 and 2 played Nintendo games for 20 min, but group 3 did not. The total intervention period was 40 min/day, 2 days/week, for 8 weeks. The cognitive and hand function of the subjects were assessed using the Trail Making Test (TMT-A, TMT-B), Grip strength, Box and Block Test (BBT), and the Manual Function Test (MFT) before and after intervention. RESULTS The tDCS + Nintendo Switch game group showed significant differences in TMT-A, TMT-B, Grip strength, MFT, and BBT results compared to the other groups between before and after intervention (p<.05). CONCLUSIONS Our results suggest that inclusion of motor tasks with the application of tDCS may be effective in improving cognitive and hand function of stroke survivors.

Differences in high-definition transcranial direct current stimulation over the motor hotspot versus the premotor cortex on motor network excitability

The effectiveness of transcranial direct current stimulation (tDCS) placed over the motor hotspot (thought to represent the primary motor cortex (M1)) to modulate motor network excitability is highly variable. The premotor cortex-particularly the dorsal premotor cortex (PMd)-may be a promising alternative target to reliably modulate motor excitability, as it influences motor control across multiple pathways, one independent of M1 and one with direct connections to M1. This double-blind, placebo-controlled preliminary study aimed to differentially excite motor and premotor regions using high-definition tDCS (HD-tDCS) with concurrent functional magnetic resonance imaging (fMRI). HD-tDCS applied over either the motor hotspot or the premotor cortex demonstrated high inter-individual variability in changes on cortical motor excitability. However, HD-tDCS over the premotor cortex led to a higher number of responders and greater changes in local fMRI-based complexity than HD-tDCS over the motor hotspot. Furthermore, an analysis of individual motor hotspot anatomical locations revealed that, in more than half of the participants, the motor hotspot is not located over anatomical M1 boundaries, despite using a canonical definition of the motor hotspot. This heterogeneity in stimulation site may contribute to the variability of tDCS results. Altogether, these preliminary findings provide new considerations to enhance tDCS reliability.

Transcranial direct current stimulation associated with physical-therapy in acute stroke patients - A randomized, triple blind, sham-controlled study

BACKGROUND

Transcranial Direct Current Stimulation has been increasing in popularity in the last few years. Despite vast amounts of articles on the use of tDCS on stroke patients, very little has been done during the acute phase.

OBJECTIVES

Measure the effects of tDCS on functional and sensory outcomes throughout the first year post onset of stroke.

METHODS

50 acute stroke patients were randomized and placed into either the treatment or sham group. Anodal tDCS was applied (2 mA, 20 min) 5 times a week during the first month post stroke. Patients were evaluated with the Wolf Motor Function Test, the Semmes Weinstein Monofilament Test, the Upper Extremity section (UEFM), the Lower Extremity section (LEFM) and the Somatosensory section of the Fugl Meyer Test, the Tardieu Spasticity Scale, the Stroke Impact Scale (SIS), the Hospital Anxiety and Depression Scale (HADS) and the Barthel Index. Evaluations were held at 48 h post stroke, week 1, 2, 3, 4, 3 months, 6 months and 1 year.

RESULTS

There were statistically and clinically significant improvements after tDCS in all functional motor outcomes, and somatosensory functions. Differences between both groups for the main outcome (WMFT time) were 51% (p = 0.04) at one month, and 57% (p = 0.02) at one year.

CONCLUSION

tDCS seems to be an effective adjuvant to conventional rehabilitation techniques. If applied in the acute stages of stroke, functional recovery is not only accelerated, but improved, and results are maintained up to one-year post stroke.

Timing-dependent interaction effects of tDCS with mirror therapy on upper extremity motor recovery in patients with chronic stroke: A randomized controlled pilot study

This study was a randomized, controlled pilot trial to investigate the timing-dependent interaction effects of dual transcranial direct current stimulation (tDCS) in mirror therapy (MT) for hemiplegic upper extremity in patients with chronic stroke. Thirty patients with chronic stroke were randomly assigned to three groups: tDCS applied before MT (prior-tDCS group), tDCS applied during MT (concurrent-tDCS group), and sham tDCS applied randomly prior to or concurrent with MT (sham-tDCS group). Dual tDCS at 1 mA was applied bilaterally over the ipsilesional M1 (anodal electrode) and the contralesional M1 (cathodal electrode) for 30 min. The intervention was delivered five days per week for two weeks. Upper extremity motor performance was measured using the Fugl-Meyer Assessment-Upper Extremity (FMA-UE), the Action Research Arm Test (ARAT), and the Box and Block Test (BBT). Assessments were administered at baseline, post-intervention, and two weeks follow-up. The results indicated that concurrent-tDCS group showed significant improvements in the ARAT in relation to the prior-tDCS group and sham-tDCS group at post-intervention. Besides, a trend toward greater improvement was also found in the FMA-UE for the concurrent-tDCS group. However, no statistically significant difference in the FMA-UE and BBT was identified among the three groups at either post-intervention or follow-up. The concurrent-tDCS seems to be more advantageous and time-efficient in the context of clinical trials combining with MT. The timing-dependent interaction factor of tDCS to facilitate motor recovery should be considered in future clinical application.

Prospects for transcranial temporal interference stimulation in humans: A computational study

Transcranial alternating current stimulation (tACS) is a noninvasive method used to modulate activity of superficial brain regions. Deeper and more steerable stimulation could potentially be achieved using transcranial temporal interference stimulation (tTIS): two high-frequency alternating fields interact to produce a wave with an envelope frequency in the range thought to modulate neural activity. Promising initial results have been reported for experiments with mice. In this study we aim to better understand the electric fields produced with tTIS and examine its prospects in humans through simulations with murine and human head models. A murine head finite element model was used to simulate previously published experiments of tTIS in mice. With a total current of 0.776 mA, tTIS electric field strengths up to 383 V/m were reached in the modeled mouse brain, affirming experimental results indicating that suprathreshold stimulation is possible in mice. Using a detailed anisotropic human head model, tTIS was simulated with systematically varied electrode configurations and input currents to investigate how these parameters influence the electric fields. An exhaustive search with 88 electrode locations covering the entire head (146M current patterns) was employed to optimize tTIS for target field strength and focality. In all analyses, we investigated maximal effects and effects along the predominant orientation of local neurons. Our results showed that it was possible to steer the peak tTIS field by manipulating the relative strength of the two input fields. Deep brain areas received field strengths similar to conventional tACS, but with less stimulation in superficial areas. Maximum field strengths in the human model were much lower than in the murine model, too low to expect direct stimulation effects. While field strengths from tACS were slightly higher, our results suggest that tTIS is capable of producing more focal fields and allows for better steerability. Finally, we present optimal four-electrode current patterns to maximize tTIS in regions of the pallidum (0.37 V/m), hippocampus (0.24 V/m) and motor cortex (0.57 V/m).

The Two-Arm Coordination Test: Maturation of Bimanual Coordination in Typically Developing Children and Deficits in Children with Unilateral Cerebral Palsy

Background: Tools to assess bimanual coordination are scant. We aimed to: 1) provide normative data of maturation of bimanual coordination in tipically developing (TD) children measured by the Two Arm Coordination Test (TACT), and 2) validate the TACT as an instrument to specifically discriminate impairment of bimanual coordination in children with unilateral cerebral palsy (UCP). Procedure: Cross-sectional observational study. 252 TD children and 26 children with UCP performed 8 trials of TACT (following a star pattern with a pointer steered by coordinated movements of both arms). Number of errors and time were combined in a performance index of motor learning.Results: In TD children, bimanual coordination improved with age (F(7,244)=36.888, p<.001). Children with UCP had a poorer bimanual coordination than TD children (all t>24.25, all p<.01). TACT scores were correlated moderately to manual dexterity and manual ability (all r>-.452, all p<.039), showing the capacity of the TACT to provide information on different aspects of hand function. Conclusion: TACT is a valid instrument to assess bimanual coordination.

Learning a Bimanual Cooperative Skill in Chronic Stroke Under Noninvasive Brain Stimulation: A Randomized Controlled Trial

Background. Transcranial direct current stimulation (tDCS) has been suggested to improve poststroke recovery. However, its effects on bimanual motor learning after stroke have not previously been explored. Objective. We investigated whether dual-tDCS of the primary motor cortex (M1), with cathodal and anodal tDCS applied over undamaged and damaged hemispheres, respectively, improves learning and retention of a new bimanual cooperative motor skill in stroke patients. Method. Twenty-one chronic hemiparetic patients were recruited for a randomized, double-blinded, cross-over, sham-controlled trial. While receiving real or sham dual-tDCS, they trained on a bimanual cooperative task called CIRCUIT. Changes in performance were quantified via bimanual speed/accuracy trade-off (Bi-SAT) and bimanual coordination factor (Bi-Co) before, during, and 0, 30, and 60 minutes after dual-tDCS, as well as one week later to measure retention. A generalization test then followed, where patients were asked to complete a new CIRCUIT layout. Results. The patients were able to learn and retain the bimanual cooperative skill. However, a general linear mixed model did not detect a significant difference in retention between the real and sham dual-tDCS conditions for either Bi-SAT or Bi-Co. Similarly, no difference in generalization was detected for Bi-SAT or Bi-Co. Conclusion. The chronic hemiparetic stroke patients learned and retained the complex bimanual cooperative task and generalized the newly acquired skills to other tasks, indicating that bimanual CIRCUIT training is promising as a neurorehabilitation approach. However, bimanual motor skill learning was not enhanced by dual-tDCS in these patients.

No effects of cerebellar transcranial direct current stimulation on force field and visuomotor reach adaptation in young and healthy subjects

Previous studies have shown that cerebellar transcranial direct current stimulation (tDCS) leads to faster adaptation of arm reaching movements to visuomotor rotation and force field perturbations in healthy subjects. The first aim of the present study was to confirm a stimulation-dependent effect on motor adaptation. Second, we investigated whether tDCS effects differ depending on onset, that is, before or at the beginning of the adaptation phase. A total of 120 healthy and right-handed subjects (60 women, mean age 23.2 ± SD 2.7 yr, range 18-31 yr) were tested. Subjects moved a cursor with a manipulandum to one of eight targets presented on a vertically orientated screen. Three baseline blocks were followed by one adaptation block and three washout blocks. Sixty subjects did a force field adaptation task (FF), and 60 subjects did a visuomotor adaptation task (VM). Equal numbers of subjects received anodal, cathodal, or sham cerebellar tDCS beginning either in the third baseline block or at the start of the adaptation block. In FF and VM, tDCS and the onset of tDCS did not show a significant effect on motor adaptation (all P values >0.05). We were unable to support previous findings of modulatory cerebellar tDCS effects in reaching adaptation tasks in healthy subjects. Prior to possible application in patients with cerebellar disease, future experiments are needed to determine which tDCS and task parameters lead to robust tDCS effects. NEW & NOTEWORTHY Transcranial direct current stimulation (tDCS) is a promising tool to improve motor learning. We investigated whether cerebellar tDCS improves motor learning in force field and visuomotor tasks in healthy subjects and what influence the onset of stimulation has. We did not find stimulation effects of tDCS or an effect of onset of stimulation. A reevaluation of cerebellar tDCS in healthy subjects and at the end of the clinical potential in cerebellar patients is demanded.

Immediate neurophysiological effects of transcranial electrical stimulation

Noninvasive brain stimulation techniques are used in experimental and clinical fields for their potential effects on brain network dynamics and behavior. Transcranial electrical stimulation (TES), including transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS), has gained popularity because of its convenience and potential as a chronic therapy. However, a mechanistic understanding of TES has lagged behind its widespread adoption. Here, we review data and modelling on the immediate neurophysiological effects of TES in vitro as well as in vivo in both humans and other animals. While it remains unclear how typical TES protocols affect neural activity, we propose that validated models of current flow should inform study design and artifacts should be carefully excluded during signal recording and analysis. Potential indirect effects of TES (e.g., peripheral stimulation) should be investigated in more detail and further explored in experimental designs. We also consider how novel technologies may stimulate the next generation of TES experiments and devices, thus enhancing validity, specificity, and reproducibility.

Effect of single-session dual-tDCS before physical therapy on lower-limb performance in sub-acute stroke patients: A randomized sham-controlled crossover study

Anodal stimulation increases cortical excitably, whereas cathodal stimulation decreases cortical excitability. Dual transcranial direct current stimulation (tDCS; anodal over the lesioned hemisphere, cathodal over the non-lesioned hemisphere) was found to enhance motor learning. The corresponding tDCS-induced changes were reported to reduce the inhibition exerted by the unaffected hemisphere on the affected hemisphere and restore the normal balance of the interhemispheric inhibition. Most studies were devoted to the possible modification of upper-limb motor function after tDCS; however, almost no study has demonstrated its effects on lower-limb function and gait, which are also commonly disordered in stroke patients with motor deficits. In this randomized sham-controlled crossover study, we included 19 patients with sub-acute stroke. Participants were randomly allocated to receive real or sham dual-tDCS followed by conventional physical therapy with an intervention interval of at least 1 week. Dual-tDCS was applied over the lower-limb M1 at 2-mA intensity for 20min. Lower-limb performance was assessed by the Timed Up and Go (TUG) and Five-Times-Sit-To-Stand (FTSTS) tests and muscle strength was assessed by peak knee torque of extension. We found a significant increase in time to perform the FTSST for the real group, with improvements significantly greater than for the sham group; the TUG score was significantly increased but not higher than for the sham group. An after-effect on FTSTS was found at approximately 1 week after the real intervention. Muscle strength was unchanged in both limbs for both real and sham groups. Our results suggest that a single session of dual-tDCS before conventional physical therapy could improve sit-to-stand performance, which appeared to be improved over conventional physical therapy alone. However, strength performance was not increased after the combination treatment.

Transcranial Direct Current Stimulation Enhances Motor Skill Learning but Not Generalization in Chronic Stroke

BACKGROUND

Motor training alone or combined with transcranial direct current stimulation (tDCS) positioned over the motor cortex (M1) improves motor function in chronic stroke. Currently, understanding of how tDCS influences the process of motor skill learning after stroke is lacking.

OBJECTIVE

To assess the effects of tDCS on the stages of motor skill learning and on generalization to untrained motor function.

METHODS

In this randomized, sham-controlled, blinded study of 56 mildly impaired chronic stroke patients, tDCS (anode over the ipsilesional M1 and cathode on the contralesional forehead) was applied during 5 days of training on an unfamiliar, challenging fine motor skill task (sequential visual isometric pinch force task). We assessed online and offline learning during the training period and retention over the following 4 months. We additionally assessed the generalization to untrained tasks.

RESULTS

With training alone (sham tDCS group), patients acquired a novel motor skill. This skill improved online, remained stable during the offline periods and was largely retained at follow-up. When tDCS was added to training (real tDCS group), motor skill significantly increased relative to sham, mostly in the online stage. Long-term retention was not affected by tDCS. Training effects generalized to untrained tasks, but those performance gains were not enhanced further by tDCS.

CONCLUSIONS

Training of an unfamiliar skill task represents a strategy to improve fine motor function in chronic stroke. tDCS augments motor skill learning, but its additive effect is restricted to the trained skill.

Combined Transcranial Direct Current Stimulation and Virtual Reality-Based Paradigm for Upper Limb Rehabilitation in Individuals with Restricted Movements. A Feasibility Study with a Chronic Stroke Survivor with Severe Hemiparesis

Impairments of the upper limb function are a major cause of disability and rehabilitation. Most of the available therapeutic options are based on active exercises and on motor and attentional inclusion of the affected arm in task oriented movements. However, active movements may not be possible after severe impairment of the upper limbs. Different techniques, such as mirror therapy, motor imagery, and non-invasive brain stimulation have been shown to elicit cortical activity in absence of movements, which could be used to preserve the available neural circuits and promote motor learning. We present a virtual reality-based paradigm for upper limb rehabilitation that allows for interaction of individuals with restricted movements from active responses triggered when they attempt to perform a movement. The experimental system also provides multisensory stimulation in the visual, auditory, and tactile channels, and transcranial direct current stimulation coherent to the observed movements. A feasibility study with a chronic stroke survivor with severe hemiparesis who seemed to reach a rehabilitation plateau after two years of its inclusion in a physical therapy program showed clinically meaningful improvement of the upper limb function after the experimental intervention and maintenance of gains in both the body function and activity. The experimental intervention also was reported to be usable and motivating. Although very preliminary, these results could highlight the potential of this intervention to promote functional recovery in severe impairments of the upper limb.