Interindividual differences in motor network connectivity and behavioral response to iTBS in stroke patients

Effect of theta burst stimulation on lower extremity motor function improvement and balance recovery in patients with stroke: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

To investigate the therapeutic benefits of theta burst stimulation on lower-limb motor dysfunction and balance recovery in patients with stroke.

METHODS

A literature search was performed across CNKI, CBM, WanFang, VIP, PubMed, Embase, Cochrane Library, and Web of Science until November 2023. The Methodological quality of included studies was assessed by using the Cochrane risk-of-bias tool and the PEDro scale, and the meta-analysis was performed by using RevMan 5.3 software. Two independent researchers screened the literature and extracted basic information on participants, interventions, comparisons, outcomes, and studies.

RESULTS

Eight studies, including cTBS and iTBS, with 290 participants meeting the inclusion criteria for this systematic review, and 7 studies including only iTBS with 230 participants were included in this meta-analysis. The methodological quality of the studies included ranged from moderate to high. The results showed iTBS had significantly higher scores on the Berg Balance Scale (BBS) than the control group. (MD = 4.57, 95% CI: 1.76 to 7.38, Z = 3.19, P = .001). Subgroup analysis showed CRB-iTBS markedly improved BBS scores (MD = 4.52, 95% CI: 1.78 to 7.27, Z = 3.23, P = .001), whereas LE M1-iTBS did not exhibit a significant enhancement in BBS scores (MD = 6.10, 95% CI: -7.34 to 19.53, Z = 0.89, P = .37); iTBS showed no significant increase in lower-limb motor function (FMA-LE) (MD = 1.80, 95% CI: -1.10 to 4.69, Z = 1.22, P = .22). Subgroup analysis revealed both CRB-iTBS and LE M1-iTBS interventions were not effective in improving FMA-LE (MD = 3.15, 95% CI: -4.70 to 11.00, Z = .79, P = .43; MD = 1.05, 95% CI: -2.20 to 4.30, Z = .63, P = .53); iTBS significantly reduced the MEP latency (P = .004), but did not show a significant improvement in walking performance (10 MWT), mobility (TUG), or activities of daily living [M(BI)] (P > .05).

CONCLUSION

Based the current study, iTBS can increase patients' balance function. The CRB-iTBS protocol is more effective than the LE M1-iTBS protocol. Additionally, iTBS may be a promising therapy tending to enhance lower-limb motor function, walking performance, mobility, and activities of daily living.

Effect of intermittent theta burst stimulation on upper limb function in stroke patients: a systematic review and meta-analysis

Background

Stroke is a serious health issue that affects individuals, families, and society. Particularly, the upper limb dysfunction caused by stroke significantly reduces the quality of life for patients and may lead to psychological issues. Current treatment modalities are not fully effective in helping patients regain upper limb motor function to optimal levels. Therefore, there is an urgent need to explore new rehabilitation methods to address this issue.

Objective

The purpose of this meta-analysis and systematic review is to explore the effects of intermittent theta burst stimulation (iTBS) on upper limb function in stroke patients.

Methods

We searched PubMed, Cochrane Library, Embase, Web of Science, PEDro and China National Knowledge Internet as of April 8, 2024. Retrieved a total of 100 articles. Standardized mean differences (SMDs) and 95% confidence intervals (CI) were calculated.

Results

The study included a total of 9 trials and involved 224 patients. The results demonstrate that compared to the control group, iTBS therapy significantly improved Fugl-Meyer assessment-upper extremity (FMA-UE) scores (SMD = 0.88; 95% CI = 0.11-1.66; P = 0.03, I 2 = 84%), Action Research Arm Test (ARAT) scores (SMD = 0.83; 95% CI = 0.16-1.50; P = 0.02, I 2 = 57%), and Barthel Index (BI) scores (SMD = 0.93; 95% CI = 0.53-1.32; P < 0.0001, I 2 = 0%) in stroke patients.

Conclusions

The comprehensive evidence suggests that iTBS has superior effects in improving upper limb function and activities of daily living in stroke patients.

Theta burst stimulation for enhancing upper extremity motor functions after stroke: a systematic review of clinical and mechanistic evidence

This systematic review aimed to evaluate the effects of different theta burst stimulation (TBS) protocols on improving upper extremity motor functions in patients with stroke, their associated modulators of efficacy, and the underlying neural mechanisms. We conducted a meta-analytic review of 29 controlled trials published from January 1, 2000, to August 29, 2023, which investigated the effects of TBS on upper extremity motor, neurophysiological, and neuroimaging outcomes in poststroke patients. TBS significantly improved upper extremity motor impairment (Hedge's g = 0.646, p = 0.003) and functional activity (Hedge's g = 0.500, p < 0.001) compared to controls. Meta-regression revealed a significant relationship between the percentage of patients with subcortical stroke and the effect sizes of motor impairment (p = 0.015) and functional activity (p = 0.018). Subgroup analysis revealed a significant difference in the improvement of upper extremity motor impairment between studies using 600-pulse and 1200-pulse TBS (p = 0.002). Neurophysiological studies have consistently found that intermittent TBS increases ipsilesional corticomotor excitability. However, evidence to support the regional effects of continuous TBS, as well as the remote and network effects of TBS, is still mixed and relatively insufficient. In conclusion, TBS is effective in enhancing poststroke upper extremity motor function. Patients with preserved cortices may respond better to TBS. Novel TBS protocols with a higher dose may lead to superior efficacy compared with the conventional 600-pulse protocol. The mechanisms of poststroke recovery facilitated by TBS can be primarily attributed to the modulation of corticomotor excitability and is possibly caused by the recruitment of corticomotor networks connected to the ipsilesional motor cortex.

Utilizing fMRI to Guide TMS Targets: the Reliability and Sensitivity of fMRI Metrics at 3 T and 1.5 T

US Food and Drug Administration (FDA) cleared a Transcranial Magnetic Stimulation (TMS) system with functional Magnetic Resonance Imaging-guided (fMRI) individualized treatment protocol for major depressive disorder, which employs resting state-fMRI (RS-fMRI) functional connectivity (FC) to pinpoint the target individually to increase the accuracy and effeteness of the stimulation. Furthermore, task activation-guided TMS, as well as the use of RS-fMRI local metrics for targeted the specific abnormal brain regions, are considered a precise scheme for TMS targeting. Since 1.5 T MRI is more available in hospitals, systematic evaluation of the test-retest reliability and sensitivity of fMRI metrics on 1.5 T and 3 T MRI may provide reference for the application of fMRI-guided individualized-precise TMS stimulation. Twenty participants underwent three RS-fMRI scans and one scan of finger-tapping task fMRI with self-initiated (SI) and visual-guided (VG) conditions at both 3 T and 1.5 T. Then the location reliability derived by FC (with three seed regions) and peak activation were assessed by intra-individual distance. The test-retest reliability and sensitivity of five RS-fMRI local metrics were evaluated using intra-class correlation and effect size, separately. The intra-individual distance of peak activation location between 1.5 T and 3 T was 15.8 mm and 19 mm for two conditions, respectively. The intra-individual distance for the FC derived targets at 1.5 T was 9.6-31.2 mm, compared to that of 3 T (7.6-31.1 mm). The test-retest reliability and sensitivity of RS-fMRI local metrics showed similar trends on 1.5 T and 3 T. These findings hasten the application of fMRI-guided individualized TMS treatment in clinical practice.

Motor network dynamic resting state fMRI connectivity of neurotypical children in regions affected by cerebral palsy

Background

Normative childhood motor network resting-state fMRI effective connectivity is undefined, yet necessary for translatable dynamic resting-state-network-informed evaluation in pediatric cerebral palsy.

Methods

Cross-spectral dynamic causal modeling of resting-state-fMRI was investigated in 50 neurotypically developing 5- to 13-year-old children. Fully connected six-node network models per hemisphere included primary motor cortex, striatum, subthalamic nucleus, globus pallidus internus, thalamus, and contralateral cerebellum. Parametric Empirical Bayes with exhaustive Bayesian model reduction and Bayesian modeling averaging informed the model; Purdue Pegboard Test scores of hand motor behavior were the covariate at the group level to determine the effective-connectivity-functional behavior relationship.

Results

Although both hemispheres exhibited similar effective connectivity of motor cortico-basal ganglia-cerebellar networks, magnitudes were slightly greater on the right, except for left-sided connections of the striatum which were more numerous and of opposite polarity. Inter-nodal motor network effective connectivity remained consistent and robust across subjects. Age had a greater impact on connections to the contralateral cerebellum, bilaterally. Motor behavior, however, affected different connections in each hemisphere, exerting a more prominent effect on the left modulatory connections to the subthalamic nucleus, contralateral cerebellum, primary motor cortex, and thalamus.

Discussion

This study revealed a consistent pattern of directed resting-state effective connectivity in healthy children aged 5-13 years within the motor network, encompassing cortical, subcortical, and cerebellar regions, correlated with motor skill proficiency. Both hemispheres exhibited similar effective connectivity within motor cortico-basal ganglia-cerebellar networks reflecting inter-nodal signal direction predicted by other modalities, mainly differing from task-dependent studies due to network differences at rest. Notably, age-related changes were more pronounced in connections to the contralateral cerebellum. Conversely, motor behavior distinctly impacted connections in each hemisphere, emphasizing its role in modulating left sided connections to the subthalamic nucleus, contralateral cerebellum, primary motor cortex, and thalamus. Motor network effective connectivity was correlated with motor behavior, validating its physiological significance. This study is the first to evaluate a normative effective connectivity model for the pediatric motor network using resting-state functional MRI correlating with behavior and serves as a foundation for identifying abnormal findings and optimizing targeted interventions like deep brain stimulation, potentially influencing future therapeutic approaches for children with movement disorders.

Age- and sex-related changes in motor functions: a comprehensive assessment and component analysis

Age-related motor impairments often cause caregiver dependency or even hospitalization. However, comprehensive investigations of the different motor abilities and the changes thereof across the adult lifespan remain sparse. We, therefore, extensively assessed essential basic and complex motor functions in 444 healthy adults covering a wide age range (range 21 to 88 years). Basic motor functions, here defined as simple isolated single or repetitive movements in one direction, were assessed by means of maximum grip strength (GS) and maximum finger-tapping frequency (FTF). Complex motor functions, comprising composite sequential movements involving both proximal and distal joints/muscle groups, were evaluated with the Action Research Arm Test (ARAT), the Jebsen-Taylor Hand Function Test (JTT), and the Purdue Pegboard Test. Men achieved higher scores than women concerning GS and FTF, whereas women stacked more pins per time than men during the Purdue Pegboard Test. There was no significant sex effect regarding JTT. We observed a significant but task-specific reduction of basic and complex motor performance scores across the adult lifespan. Linear regression analyses significantly predicted the participants' ages based on motor performance scores (R2 = 0.502). Of note, the ratio between the left- and right-hand performance remained stable across ages for all tests. Principal Component Analysis (PCA) revealed three motor components across all tests that represented dexterity, force, and speed. These components were consistently present in young (21-40 years), middle-aged (41-60 years), and older (61-88 years) adults, as well as in women and men. Based on the three motor components, K-means clustering analysis differentiated high- and low-performing participants across the adult life span. The rich motor data set of 444 healthy participants revealed age- and sex-dependent changes in essential basic and complex motor functions. Notably, the comprehensive assessment allowed for generating robust motor components across the adult lifespan. Our data may serve as a reference for future studies of healthy subjects and patients with motor deficits. Moreover, these findings emphasize the importance of comprehensively assessing different motor functions, including dexterity, force, and speed, to characterize human motor abilities and their age-related decline.

Exploring Motor Network Connectivity in State-Dependent Transcranial Magnetic Stimulation: A Proof-of-Concept Study

State-dependent non-invasive brain stimulation (NIBS) informed by electroencephalography (EEG) has contributed to the understanding of NIBS inter-subject and inter-session variability. While these approaches focus on local EEG characteristics, it is acknowledged that the brain exhibits an intrinsic long-range dynamic organization in networks. This proof-of-concept study explores whether EEG connectivity of the primary motor cortex (M1) in the pre-stimulation period aligns with the Motor Network (MN) and how the MN state affects responses to the transcranial magnetic stimulation (TMS) of M1. One thousand suprathreshold TMS pulses were delivered to the left M1 in eight subjects at rest, with simultaneous EEG. Motor-evoked potentials (MEPs) were measured from the right hand. The source space functional connectivity of the left M1 to the whole brain was assessed using the imaginary part of the phase locking value at the frequency of the sensorimotor μ-rhythm in a 1 s window before the pulse. Group-level connectivity revealed functional links between the left M1, left supplementary motor area, and right M1. Also, pulses delivered at high MN connectivity states result in a greater MEP amplitude compared to low connectivity states. At the single-subject level, this relation is more highly expressed in subjects that feature an overall high cortico-spinal excitability. In conclusion, this study paves the way for MN connectivity-based NIBS.

Theta burst stimulation: what role does it play in stroke rehabilitation? A systematic review of the existing evidence

Various post-stroke dysfunctions often result in poor long-term outcomes for stroke survivors, but the effect of conventional treatments is limited. In recent years, lots of studies have confirmed the effect of repetitive transcranial magnetic stimulation (rTMS) in stroke rehabilitation. As a new pattern of rTMS, theta burst stimulation (TBS) was proved recently to yield more pronounced and long-lasting after-effects than the conventional pattern at a shorter stimulation duration. To explore the role of TBS in stroke rehabilitation, this review summarizes the existing evidence from all the randomized controlled trials (RCTs) so far on the efficacy of TBS applied to different post-stroke dysfunctions, including cognitive impairment, visuospatial neglect, aphasia, dysphagia, spasticity, and motor dysfunction. Overall, TBS promotes the progress of stroke rehabilitation and may serve as a preferable alternative to traditional rTMS. However, it's hard to recommend a specific paradigm of TBS due to the limited number of current studies and their heterogeneity. Further high-quality clinical RCTs are needed to determine the optimal technical settings and intervention time in stroke survivors.

Effects of robot-assisted upper limb training combined with intermittent theta burst stimulation (iTBS) on cortical activation in stroke patients: A functional near-infrared spectroscopy study

BACKGROUND

The therapeutic effect and mechanism of robot-assisted upper limb training (RT) combined with intermittent theta burst stimulation (iTBS) for stroke patients are unclear.

OBJECTIVE

The purpose of this study was to evaluate changes in brain activation after combination therapy and RT alone using functional near-infrared spectroscopy (fNIRS).

METHODS

Patients were randomly assigned to two groups (iTBS + RT Group, n = 18, and RT Group, n = 18). Training was conducted five times a week for four weeks. fNIRS was used to measure changes in oxyhemoglobin in both the primary motor cortex (M1) and pre-motor and supplementary motor area (pSMA) during affected limb movement. Fugl-Meyer Assessment-Upper Extremity (FMA-UE) was employed for evaluating the function of upper limbs.

RESULTS

Thirty-two patients with subacute stroke completed the study. The cortex of both hemispheres was extensively activated prior to treatment in the RT group. After training, overactivation decreased. The brain activation of the combined treatment group transferred to the affected side after the treatment. There was a notable enhancement in the FMA-UE scores for both groups, with the combined group's progress significantly surpassing that of the RT group.

CONCLUSION

RT combined with iTBS can improve the motor function of stroke patients and promote the balance between cerebral hemispheres.

Effects of central intermittent theta-burst stimulation combined with repetitive peripheral magnetic stimulation on upper limb function in stroke patients

Background

Intermittent theta-burst stimulation and repetitive peripheral magnetic stimulation can improve motor function in poststroke patients, but the therapeutic effect of this combination remains unclear.

Objective

To determine the effects of central intermittent theta-burst stimulation and repetitive peripheral magnetic stimulation on upper limb function.

Methods

Fifty-six subacute stroke patients were randomly assigned to three groups: the CMS (n = 18), peripheral magnetic stimulation (PMS) (n = 19) and CPS (n = 19) groups. The CMS group received intermittent theta-burst stimulation and peripheral false stimulation, while the PMS group received repetitive peripheral magnetic stimulation and central false stimulation once a day for five days a week over four weeks. The CPS group received intermittent theta-burst stimulation and repetitive peripheral magnetic stimulation simultaneously once daily for four weeks. The Fugl-Meyer Assessment, Action Research Arm Test, Modified Barthel Index and Modified Ashworth Scale evaluated outcomes before and after four weeks of treatment.

Results

The motor function scores of all groups were significantly increased after treatment compared with before treatment, while the Modified Ashworth Scale score showed no significant change. There was a significant difference in the motor function score of the CPS group compared with that of the CMS and PMS groups, but there was no significant improvement in the Modified Ashworth Scale score.

Conclusion

Combining the two treatment methods can improve patients' motor function and daily living abilities but cannot improve muscle tone.

Task-residual effective connectivity of motor network in transient ischemic attack

Transient ischemic attack (TIA) is a temporary episode of neurological dysfunction that results from focal brain ischemia. Although TIA symptoms are quickly resolved, patients with TIA have a high risk of stroke and persistent impairments in multiple domains of cognitive and motor functions. In this study, using spectral dynamic causal modeling, we investigate the changes in task-residual effective connectivity of patients with TIA during fist-closing movements. 28 healthy participants and 15 age-matched patients with TIA undergo functional magnetic resonance imaging at 7T. Here we show that during visually cued motor movement, patients with TIA have significantly higher effective connectivity toward the ipsilateral primary motor cortex and lower connectivity to the supplementary motor area than healthy controls. Our results imply that TIA patients have aberrant connections among motor regions, and these changes may reflect the decreased efficiency of primary motor function and disrupted control of voluntary movement in patients with TIA.

Noninvasive Brain Stimulation for Neurorehabilitation in Post-Stroke Patients

Characterized by high morbidity, mortality, and disability, stroke usually causes symptoms of cerebral hypoxia due to a sudden blockage or rupture of brain vessels, and it seriously threatens human life and health. Rehabilitation is the essential treatment for post-stroke patients suffering from functional impairments, through which hemiparesis, aphasia, dysphagia, unilateral neglect, depression, and cognitive dysfunction can be restored to various degrees. Noninvasive brain stimulation (NIBS) is a popular neuromodulatory technology of rehabilitation focusing on the local cerebral cortex, which can improve clinical functions by regulating the excitability of corresponding neurons. Increasing evidence has been obtained from the clinical application of NIBS, especially repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS). However, without a standardized protocol, existing studies on NIBS show a wide variation in terms of stimulation site, frequency, intensity, dosage, and other parameters. Its application for neurorehabilitation in post-stroke patients is still limited. With advances in neuronavigation technologies, functional near-infrared spectroscopy, and functional MRI, specific brain regions can be precisely located for stimulation. On the basis of our further understanding on neural circuits, neuromodulation in post-stroke rehabilitation has also evolved from single-target stimulation to co-stimulation of two or more targets, even circuits and the network. The present study aims to review the findings of current research, discuss future directions of NIBS application, and finally promote the use of NIBS in post-stroke rehabilitation.

Computation of transcranial magnetic stimulation electric fields using self-supervised deep learning

Electric fields (E-fields) induced by transcranial magnetic stimulation (TMS) can be modeled using partial differential equations (PDEs). Using state-of-the-art finite-element methods (FEM), it often takes tens of seconds to solve the PDEs for computing a high-resolution E-field, hampering the wide application of the E-field modeling in practice and research. To improve the E-field modeling's computational efficiency, we developed a self-supervised deep learning (DL) method to compute precise TMS E-fields. Given a head model and the primary E-field generated by TMS coils, a DL model was built to generate a E-field by minimizing a loss function that measures how well the generated E-field fits the governing PDE. The DL model was trained in a self-supervised manner, which does not require any external supervision. We evaluated the DL model using both a simulated sphere head model and realistic head models of 125 individuals and compared the accuracy and computational speed of the DL model with a state-of-the-art FEM. In realistic head models, the DL model obtained accurate E-fields that were significantly correlated with the FEM solutions. The DL model could obtain precise E-fields within seconds for whole head models at a high spatial resolution, faster than the FEM. The DL model built for the simulated sphere head model also obtained an accurate E-field whose average difference from the analytical E-fields was 0.0054, comparable to the FEM solution. These results demonstrated that the self-supervised DL method could obtain precise E-fields comparable to the FEM solutions with improved computational speed.

Test-retest reliability of peak location in the sensorimotor network of resting state fMRI for potential rTMS targets

Most stroke repetitive transcranial magnetic stimulation (rTMS) studies have used hand motor hotspots as rTMS stimulation targets; in addition, recent studies demonstrated that functional magnetic resonance imaging (fMRI) task activation could be used to determine suitable targets due to its ability to reveal individualized precise and stronger functional connectivity with motor-related brain regions. However, rTMS is unlikely to elicit motor evoked potentials in the affected hemisphere, nor would activity be detected when stroke patients with severe hemiplegia perform an fMRI motor task using the affected limbs. The current study proposed that the peak voxel in the resting-state fMRI (RS-fMRI) motor network determined by independent component analysis (ICA) could be a potential stimulation target. Twenty-one healthy young subjects underwent RS-fMRI at three visits (V1 and V2 on a GE MR750 scanner and V3 on a Siemens Prisma) under eyes-open (EO) and eyes-closed (EC) conditions. Single-subject ICA with different total number of components (20, 30, and 40) were evaluated, and then the locations of peak voxels on the left and right sides of the sensorimotor network (SMN) were identified. While most ICA RS-fMRI studies have been carried out on the group level, that is, Group-ICA, the current study performed individual ICA because only the individual analysis could guide the individual target of rTMS. The intra- (test-retest) and inter-scanner reliabilities of the peak location were calculated. The use of 40 components resulted in the highest test-retest reliability of the peak location in both the left and right SMN compared with that determined when 20 and 30 components were used for both EC and EO conditions. ICA with 40 components might be another way to define a potential target in the SMN for poststroke rTMS treatment.

Rewiring Cortico-Muscular Control in the Healthy and Poststroke Human Brain with Proprioceptive β-Band Neurofeedback

In severely affected stroke survivors, cortico-muscular control is disturbed and volitional upper limb movements often absent. Mental rehearsal of the impaired movement in conjunction with sensory feedback provision are suggested as promising rehabilitation exercises. Knowledge about the underlying neural processes, however, remains vague. In male and female chronic stroke patients with hand paralysis, a brain-computer interface controlled a robotic orthosis and turned sensorimotor β-band desynchronization during motor imagery (MI) of finger extension into contingent hand opening. Healthy control subjects performed the same task and received the same proprioceptive feedback with a robotic orthosis or visual feedback only. Only when proprioceptive feedback was provided, cortico-muscular coherence (CMC) increased with a predominant information flow from the sensorimotor cortex to the finger extensors. This effect (1) was specific to the β frequency band, (2) transferred to a motor task (MT), (3) was proportional to subsequent corticospinal excitability (CSE) and correlated with behavioral changes in the (4) healthy and (5) poststroke condition; notably, MI-related enhancement of β-band CMC in the ipsilesional premotor cortex correlated with motor improvements after the intervention. In the healthy and injured human nervous system, synchronized activation of motor-related cortical and spinal neural pools facilitates, in accordance with the communication-through-coherence hypothesis, cortico-spinal communication and may, thereby, be therapeutically relevant for functional restoration after stroke, when voluntary movements are no longer possible.SIGNIFICANCE STATEMENT This study provides insights into the neural processes that transfer effects of brain-computer interface neurofeedback to subsequent motor behavior. Specifically, volitional control of cortical oscillations and proprioceptive feedback enhances both cortical activity and behaviorally relevant connectivity to the periphery in a topographically circumscribed and frequency-specific way. This enhanced cortico-muscular control can be induced in the healthy and poststroke brain. Thereby, activating the motor cortex with mental rehearsal of the impaired movement and closing the loop by robot-assisted feedback synchronizes ipsilesional premotor cortex and spinal neural pools in the β frequency band. This facilitates, in accordance with the communication-through-coherence hypothesis, cortico-spinal communication and may, thereby, be therapeutically relevant for functional restoration after stroke, when voluntary movements are no longer possible.

Effects of Repetitive Transcranial Magnetic Stimulation on Gait and Postural Control Ability of Patients with Executive Dysfunction after Stroke

Objective: To assess the effects of repetitive transcranial magnetic stimulation (rTMS) on the gait and postural control ability of patients with executive dysfunction (ED) after stroke. Methods: A total of 18 patients with ED after stroke were randomly assigned into two groups, including an experimental group and a sham group. Patients in both groups received routine rehabilitation therapy, and patients in the experimental group underwent rTMS on the left dorsolateral prefrontal cortex (DLPFC) for 2 weeks (5 HZ, 80%MT, 1200 pulses). In the sham group, patients experienced sham stimulation treatment, in which the coil was placed vertically with the head. Before and after treatment, patients in both groups were subjected to Montreal cognitive assessment (MoCA) scoring, Fugl−Meyer assessment of lower extremity (L-FMA), Stroop color-word test (SCWT), gait analysis, foot plantar pressure test, 10-m walking test (10MWT), Berg balance scale (BBS), and timed up and go test (TUGT). In the SCWT, it was attempted to record the time of each card (SCWT-T), the correct number (SCWT-C), Stroop interference effect-time (SIE-T), and SIE correct count (SIE-C). The TUGT was categorized into four stages: getting up (GT), walking straight (WT), turning around (TT), and sitting down (ST), in which the total time of TUGT was calculated. Results: After two weeks of treatment, the evaluation indexes were improved in the two groups, some of which were statistically significant. In the experimental group, SCWT-T, SIE-T, SIE-C, GT, WT, TT, ST, and TUGT were significantly improved after treatment (p < 0.05). SCWT-C, L-FMA score, 10MWT, GT, WT, stride length, step width, foot plantar pressure, pressure center curve, and activities of daily living were not statistically different from those before treatment (p > 0.05). After treatment, SCWT-T, SIE-C, SIE-T, BBS score, TT, and ST in the experimental group were significantly shorter than those before treatment, with statistical differences (p < 0.05). Compared with the sham group, SCWT-C, L-FMA score, 10MWT, GT, WT, TUGT, stride length, step width, foot plantar pressure, pressure center curve, and motor skills were not significantly improved (p > 0.05). Conclusion: It was revealed that post-stroke rTMS treatment of patients with ED could improve executive function, improve postural control function, and reduce the risk of falling. In addition, rTMS of DLPFC could be a therapeutic target for improving postural control ability and reducing the risk of falling.

High-Definition Transcranial Direct Current with Electrical Theta Burst on Post-Stroke Motor Rehabilitation: A Pilot Randomized Controlled Trial

BACKGROUND

High-definition transcranial electrical theta burst superimposing direct current stimulation (HD-tDCS-eTBS) not only incorporates the therapeutic advantages of tDCS and TBS but enhances stimulation focality and practicality. However, the applicability of this innovative neuromodulatory device in post-stroke rehabilitation remains uncertain.

OBJECTIVE

This study aimed to assess the efficacy and safety of the HD-tDCS-eTBS on upper extremity (UE) motor function in patients with chronic stroke.

METHODS

A patient-blinded, randomized controlled study was conducted. Twenty-four participants were randomly assigned into either the active HD-tDCS-eTBS group or sham HD-tDCS-eTBS group. Both groups received 20 minutes of active/sham HD-tDCS-eTBS combined with 30 minutes of conventional UE rehabilitation each time, 3 times a week for 4 weeks. Outcome measures including the Fugl-Meyer Assessment of Upper Extremity, Wolf Motor Function Test, Jebsen-Taylor Hand Function Test, Finger-Nose Test, and Modified Ashworth Scale were assessed before and immediately after the intervention period.

RESULTS

Spasticity of shoulder adductor (P = .05), elbow extensor (P = .04), and thumb flexor (P < .01) were significantly reduced in the active HD-tDCS-eTBS group versus the sham group. Nonsignificant trends in the improvements of most other outcome measures were in favor of the active HD-tDCS-eTBS group with moderate to large effect sizes (P = .06-.26, η_p² = 0.06-0.16). No severe adverse events except for slight skin redness under the stimulus electrode was detected after the HD-tDCS-eTBS.

CONCLUSIONS

Our findings support that HD-tDCS-eTBS is safe and has therapeutic potential for post-stroke UE motor rehabilitation.

TRIAL REGISTRATION

ClinicalTrials.gov (ID: NCT04278105).

Intermittent theta-burst stimulation with physical exercise improves poststroke motor function: A systemic review and meta-analysis

Background

Intermittent theta-burst stimulation (iTBS) is an optimized rTMS modality that could modulate the excitability of neural structures. Several studies have been conducted to investigate the efficacy of iTBS in improving the motor function of stroke patients. However, the specific role of iTBS in motor function recovery after stroke is unclear. Hence, in our study, we performed a meta-analysis to investigate the efficacy of iTBS for the motor function improvement of stroke patients.

Methods

MEDLINE, Embase, and Cochrane Library were searched until May 2022 for randomized controlled trials (RCTs).

Results

Thirteen RCTs with 334 patients were finally included in our study. The primary endpoints were the Fugl-Meyer assessment scale (FMA) and Motor Assessment Scale (MAS) change from baseline. We found that iTBS led to a significant reduction in FMA score (P = 0.002) but not in MAS score (P = 0.24) compared with the sham group. Moreover, standard 600-pulse stimulation showed a better effect on motor function improvement than the sham group (P = 0.004), however, 1200-pulse iTBS showed no effect on motor function improvement after stroke (P = 0.23). The effect of iTBS for improving motor function only exists in chronic stroke patients (P = 0.02) but not in subacute patients (P = 0.27).

Conclusion

This study supports that iTBS has good efficacy for improving motor function in stroke patients. Therefore, standard 600-pulse stimulation iTBS therapy is proper management and treatment for chronic stroke.

The Effectiveness of Intermittent Theta Burst Stimulation for Stroke Patients With Upper Limb Impairments: A Systematic Review and Meta-Analysis

Background

Upper limb impairments are one of the most common health problems of stroke, affecting both motor function and independence in daily life. It has been demonstrated that intermittent theta burst stimulation (iTBS) increases brain excitability and improves upper limb function. Our study sought to determine the role of iTBS in stroke recovery.

Objective

The purpose of this study was to determine the efficacy of iTBS in individuals with upper limb impairments following stroke.

Methods

The databases used included Cumulative Index to PubMed, EMBASE, ESCBOhost, The Cochrane Library, Chinese Biomedical Database, Web of Science, China Biology Medicine (CBM), China National Knowledge Infrastructure (CNKI), Technology Periodical Database (VIP), and WanFang Database. Studies published before November 2021 were included. Each participant received an iTBS-based intervention aimed at improving activity levels or impairment, which was compared to usual care, a sham intervention, or another intervention. The primary outcome measure was a change in upper limb function assessment. Secondary outcomes included impairment, participation, and quality of life measures.

Result

A total of 18 studies (n = 401 participants) that met the inclusion criteria were included in this study. There was a slight change in the upper limb function of the iTBS group compared with the control group, as measured by the Fugl-Meyer Assessment-Upper Extremity (FMA-UE) score (mean difference 2.70, 95% CI −0.02 to 5.42, p = 0.05). Significant improvement in resting motor threshold (RMT) and motor-evoked potential (MEP) was also observed in the meta-analysis of iTBS (MD 3.46, 95% CI 2.63 to 4.28, p < 0.00001); (MD 1.34, 95% CI 1.17 to 1.51, P < 0.00001). In addition, we got similar results when the studies were using the Modified Barthel Index (MBI) assessment (mean difference of 7.34, 95% CI 0.47 to 14.21, p = 0.04).

Conclusion

Our study established the efficacy of iTBS in improving motor cortical plasticity, motor function, and daily functioning in stroke patients. However, the review requires evidence from additional randomized controlled trials and high-quality research.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/

Effects of the Intermittent Theta Burst Stimulation of the Cerebellar Vermis on Balance Recovery After Stroke: A Study Protocol for a Randomized Controlled Trial

Background

The recovery of balance function is a critical segment in the rehabilitation treatment of stroke. The cerebellum is considered as the key structure involved in balance and motor control. The cerebellar vermis plays an important role in integrating vision, proprioception, and sensory skin input and may be a candidate stimulation target for regulating the motor network related with balance. However, evidence that the intermittent theta burst stimulation (iTBS) of cerebellar vermis can promote the recovery of balance function after stroke remains insufficient. Therefore, this study aims to explore the efficacy of the cerebellar vermis iTBS for the treatment of balance function in patients with stroke.

Methods and Analysis

Forty patients with stroke will be recruited in this prospective, randomized, sham-controlled trial. Participants will be randomized in a 1:1 ratio to receive either 15 sessions of cerebellar vermis iTBS (600 pulses) or sham stimulation. Additionally, a routine rehabilitation therapy follows the intervention. The primary outcome is the Berg Balance Scale, and the secondary outcomes are the Fugl–Meyer assessment of the lower extremity and modified Barthel index. The above outcomes will be assessed before intervention and at the end of each week. Pre- and post-iTBS resting-state functional magnetic resonance imaging (rs-fMRI) will be acquired, and the regional homogeneity, fractional amplitude of low-frequency fluctuation and functional connectivity will be calculated and analyzed.

Discussion

This protocol holds promise as a potential method to improve balance function in patients with stroke. If the outcomes of patients improve after the intervention, the study will provide new insights into improving balance function.

Ethics and Dissemination

This study has been approved by the Medical Research Ethics Committee of Wuxi Mental Health Center (Wuxi Tongren Rehabilitation Hospital). Results will be disseminated through (open-access) peer-reviewed publications, networks of scientists, professionals, and the public and presented at conferences.

Clinical Trial Registration Number

www.chictr.org.cn, identifier ChiCTR2100052590.

Effects of transcranial magnetic stimulation in modulating cortical excitability in patients with stroke: a systematic review and meta-analysis

Background

Transcranial magnetic stimulation (TMS) has attracted plenty of attention as it has been proved to be effective in facilitating motor recovery in patients with stroke. The aim of this study was to systematically review the effects of repetitive TMS (rTMS) and theta burst stimulation (TBS) protocols in modulating cortical excitability after stroke.

Methods

A literature search was carried out using PubMed, Medline, EMBASE, CINAHL, and PEDro, to identify studies that investigated the effects of four rTMS protocols—low and high frequency rTMS, intermittent and continuous TBS, on TMS measures of cortical excitability in stroke. A random-effects model was used for all meta-analyses.

Results

Sixty-one studies were included in the current review. Low frequency rTMS was effective in decreasing individuals’ resting motor threshold and increasing the motor-evoked potential of the non-stimulated M1 (affected M1), while opposite effects occurred in the stimulated M1 (unaffected M1). High frequency rTMS enhanced the cortical excitability of the affected M1 alone. Intermittent TBS also showed superior effects in rebalancing bilateral excitability through increasing and decreasing excitability within the affected and unaffected M1, respectively. Due to the limited number of studies found, the effects of continuous TBS remained inconclusive. Motor impairment was significantly correlated with various forms of TMS measures.

Conclusions

Except for continuous TBS, it is evident that these protocols are effective in modulating cortical excitability in stroke. Current evidence does support the effects of inhibitory stimulation in enhancing the cortical excitability of the affected M1.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12984-022-00999-4.

Predicting Individual Treatment Response to rTMS for Motor Recovery After Stroke: A Review and the CanStim Perspective

Background

Rehabilitation is critical for reducing stroke-related disability and improving quality-of-life post-stroke. Repetitive transcranial magnetic stimulation (rTMS), a non-invasive neuromodulation technique used as stand-alone or adjunct treatment to physiotherapy, may be of benefit for motor recovery in subgroups of stroke patients. The Canadian Platform for Trials in Non-Invasive Brain Stimulation (CanStim) seeks to advance the use of these techniques to improve post-stroke recovery through clinical trials and pre-clinical studies using standardized research protocols. Here, we review existing clinical trials for demographic, clinical, and neurobiological factors which may predict treatment response to identify knowledge gaps which need to be addressed before implementing these parameters for patient stratification in clinical trial protocols.

Objective

To provide a review of clinical rTMS trials of stroke recovery identifying factors associated with rTMS response in stroke patients with motor deficits and develop research perspectives for pre-clinical and clinical studies.

Methods

A literature search was performed in PubMed, using the Boolean search terms stroke AND repetitive transcranial magnetic stimulation OR rTMS AND motor for studies investigating the use of rTMS for motor recovery in stroke patients at any recovery phase. A total of 1,676 articles were screened by two blinded raters, with 26 papers identified for inclusion in this review.

Results

Multiple possible factors associated with rTMS response were identified, including stroke location, cortical thickness, brain-derived neurotrophic factor (BDNF) genotype, initial stroke severity, and several imaging and clinical factors associated with a relatively preserved functional motor network of the ipsilesional hemisphere. Age, sex, and time post-stroke were generally not related to rTMS response. Factors associated with greater response were identified in studies of both excitatory ipsilesional and inhibitory contralesional rTMS. Heterogeneous study designs and contradictory data exemplify the need for greater protocol standardization and high-quality controlled trials.

Conclusion

Clinical, brain structural and neurobiological factors have been identified as potential predictors for rTMS response in stroke patients with motor impairment. These factors can inform the design of future clinical trials, before being considered for optimization of individual rehabilitation therapy for stroke patients. Pre-clinical models for stroke recovery, specifically developed in a clinical context, may accelerate this process.

A Novel Method to Assess Motor Cortex Connectivity and Event Related Desynchronization Based on Mass Models

Knowledge of motor cortex connectivity is of great value in cognitive neuroscience, in order to provide a better understanding of motor organization and its alterations in pathological conditions. Traditional methods provide connectivity estimations which may vary depending on the task. This work aims to propose a new method for motor connectivity assessment based on the hypothesis of a task-independent connectivity network, assuming nonlinear behavior. The model considers six cortical regions of interest (ROIs) involved in hand movement. The dynamics of each region is simulated using a neural mass model, which reproduces the oscillatory activity through the interaction among four neural populations. Parameters of the model have been assigned to simulate both power spectral densities and coherences of a patient with left-hemisphere stroke during resting condition, movement of the affected, and movement of the unaffected hand. The presented model can simulate the three conditions using a single set of connectivity parameters, assuming that only inputs to the ROIs change from one condition to the other. The proposed procedure represents an innovative method to assess a brain circuit, which does not rely on a task-dependent connectivity network and allows brain rhythms and desynchronization to be assessed on a quantitative basis.

The effect of intermittent theta burst stimulation on corticomotor excitability of the biceps brachii in nonimpaired individuals

Intermittent theta burst stimulation (iTBS) is a form of repetitive transcranial magnetic stimulation (TMS) that can increase corticomotor excitability in distal upper limb muscles, but the effect on the more proximal biceps is unknown. The study objective was to determine the effect of iTBS on corticomotor excitability of the biceps brachii in non-impaired individuals. Ten individuals completed three sessions, and an additional ten individuals completed one session in a secondary study; each session included sham and active iTBS. Resting and active motor thresholds (RMT, AMT) were determined prior to sham and active iTBS. Motor evoked potentials (MEPs) in response to single pulse TMS served as our measure of corticomotor excitability. In our primary cohort, MEPs were recorded with biphasic stimulation to accurately capture the same neurons affected by biphasic iTBS. MEPs were recorded at an intensity of 120% of RMT, or for instances of high RMTs, 100% of the maximum stimulator output (MSO), at baseline, and 10, 20, and 30 minutes after iTBS. MEPs were normalized by the maximum voluntary isometric muscle activity. In the secondary, MEPs were recorded with monophasic stimulation, which increased our ability to record MEPs at 120% of RMT. Linear mixed effects models were used to determine the effect of iTBS on normalized MEPs (nMEPs), with analyses to evaluate the interaction of the biceps AMT:RMT ratio as a measure of corticomotor conductance. Change in nMEPs from baseline did not differ for the active and sham conditions (p = 0.915 ) when MEPs were assessed with biphasic stimulation. With MEPs assessed by monophasic stimulation, there was an increase in biceps nMEPs after active iTBS, and no change in nMEPs after sham. Our results suggest that when RMTs are expected to be high when measured with biphasic stimulation, monophasic stimulation can better capture changes in MEPs induced by iTBS, and biphasic stimulation appears limited in its ability to capture changes in biceps MEPs in nonimpaired individuals. In both cohorts, increased corticomotor excitability after iTBS occurred when the biceps AMT:RMT ratio was high. Thus, the AMT:RMT ratio may be a predictive measure to evaluate the potential for iTBS to increase biceps corticomotor excitability.

Dynamic Causal Modeling on the Identification of Interacting Networks in the Brain: A Systematic Review

Dynamic causal modeling (DCM) has long been used to characterize effective connectivity within networks of distributed neuronal responses. Previous reviews have highlighted the understanding of the conceptual basis behind DCM and its variants from different aspects. However, no detailed summary or classification research on the task-related effective connectivity of various brain regions has been made formally available so far, and there is also a lack of application analysis of DCM for hemodynamic and electrophysiological measurements. This review aims to analyze the effective connectivity of different brain regions using DCM for different measurement data. We found that, in general, most studies focused on the networks between different cortical regions, and the research on the networks between other deep subcortical nuclei or between them and the cerebral cortex are receiving increasing attention, but far from the same scale. Our analysis also reveals a clear bias towards some task types. Based on these results, we identify and discuss several promising research directions that may help the community to attain a clear understanding of the brain network interactions under different tasks.

Predictive models for response to non-invasive brain stimulation in stroke: A critical review of opportunities and pitfalls

BACKGROUND

Noninvasive brain stimulation has been successfully applied to improve stroke-related impairments in different behavioral domains. Yet, clinical translation is limited by heterogenous outcomes within and across studies. It has been proposed to develop and apply noninvasive brain stimulation in a patient-tailored, precision medicine-guided fashion to maximize response rates and effect magnitude. An important prerequisite for this task is the ability to accurately predict the expected response of the individual patient.

OBJECTIVE

This review aims to discuss current approaches studying noninvasive brain stimulation in stroke and challenges associated with the development of predictive models of responsiveness to noninvasive brain stimulation.

METHODS

Narrative review.

RESULTS

Currently, the field largely relies on in-sample associational studies to assess the impact of different influencing factors. However, the associational approach is not valid for making claims of prediction, which generalize out-of-sample. We will discuss crucial requirements for valid predictive modeling in particular the presence of sufficiently large sample sizes.

CONCLUSION

Modern predictive models are powerful tools that must be wielded with great care. Open science, including data sharing across research units to obtain sufficiently large and unbiased samples, could provide a solid framework for addressing the task of building robust predictive models for noninvasive brain stimulation responsiveness.

Early motor network connectivity after stroke: An interplay of general reorganization and state-specific compensation

Motor recovery after stroke relies on functional reorganization of the motor network, which is commonly assessed via functional magnetic resonance imaging (fMRI)-based resting-state functional connectivity (rsFC) or task-related effective connectivity (trEC). Measures of either connectivity mode have been shown to successfully explain motor impairment post-stroke, posing the question whether motor impairment is more closely reflected by rsFC or trEC. Moreover, highly similar changes in ipsilesional and interhemispheric motor network connectivity have been reported for both rsFC and trEC after stroke, suggesting that altered rsFC and trEC may capture similar aspects of information integration in the motor network reflecting principle, state-independent mechanisms of network reorganization rather than state-specific compensation strategies. To address this question, we conducted the first direct comparison of rsFC and trEC in a sample of early subacute stroke patients (n = 26, included on average 7.3 days post-stroke). We found that both rsFC and trEC explained motor impairment across patients, stressing the clinical potential of fMRI-based connectivity. Importantly, intrahemispheric connectivity between ipsilesional M1 and premotor areas depended on the activation state, whereas interhemispheric connectivity between homologs was state-independent. From a mechanistic perspective, our results may thus arise from two distinct aspects of motor network plasticity: task-specific compensation within the ipsilesional hemisphere and a more fundamental form of reorganization between hemispheres.

Repetitive transcranial magnetic stimulation as a potential treatment approach for cannabis use disorder

The expanding legalization of cannabis across the United States is associated with increases in cannabis use, and accordingly, an increase in the number and severity of individuals with cannabis use disorder (CUD). The lack of FDA-approved pharmacotherapies and modest efficacy of psychotherapeutic interventions means that many of those who seek treatment for CUD relapse within the first few months. Consequently, there is a pressing need for innovative, evidence-based treatment development for CUD. Preliminary evidence suggests that repetitive transcranial magnetic stimulation (rTMS) may be a novel, non-invasive therapeutic neuromodulation tool for the treatment of a variety of substance use disorders (SUDs), including recently receiving FDA clearance (August 2020) for use as a smoking cessation aid in tobacco cigarette smokers. However, the potential of rTMS for CUD has not yet been reviewed. This paper provides a primer on therapeutic neuromodulation techniques for SUDs, with a particular focus on reviewing the current status of rTMS research in people who use cannabis. Lastly, future directions are proposed for rTMS treatment development in CUD, with suggestions for study design parameters and clinical endpoints based on current gold-standard practices for therapeutic neuromodulation research.

Transcranial electrostimulation with special waveforms enhances upper-limb motor function in patients with chronic stroke: a pilot randomized controlled trial

Background

Transcranial direct current stimulation (tDCS) and intermittent theta burst stimulation (iTBS) were both demonstrated to have therapeutic potentials to rapidly induce neuroplastic effects in various rehabilitation training regimens. Recently, we developed a novel transcranial electrostimulation device that can flexibly output an electrical current with combined tDCS and iTBS waveforms. However, limited studies have determined the therapeutic effects of this special waveform combination on clinical rehabilitation. Herein, we investigated brain stimulation effects of tDCS-iTBS on upper-limb motor function in chronic stroke patients.

Methods

Twenty-four subjects with a chronic stroke were randomly assigned to a real non-invasive brain stimulation (NIBS; who received the real tDCS + iTBS output) group or a sham NIBS (who received sham tDCS + iTBS output) group. All subjects underwent 18 treatment sessions of 1 h of a conventional rehabilitation program (3 days a week for 6 weeks), where a 20-min NIBS intervention was simultaneously applied during conventional rehabilitation. Outcome measures were assessed before and immediately after the intervention period: Fugl-Meyer Assessment-Upper Extremity (FMA-UE), Jebsen-Taylor Hand Function Test (JTT), and Finger-to-Nose Test (FNT).

Results

Both groups showed improvements in FMA-UE, JTT, and FNT scores after the 6-week rehabilitation program. Notably, the real NIBS group had greater improvements in the JTT (p = 0. 016) and FNT (p = 0. 037) scores than the sham NIBS group, as determined by the Mann–Whitney rank-sum test.

Conclusions

Patients who underwent the combined ipsilesional tDCS-iTBS stimulation with conventional rehabilitation exhibited greater impacts than did patients who underwent sham stimulation-conventional rehabilitation in statistically significant clinical responses of the total JTT time and FNT after the stroke. Preliminary results of upper-limb functional recovery suggest that tDCS-iTBS combined with a conventional rehabilitation intervention may be a promising strategy to enhance therapeutic benefits in future clinical settings.

Trial registration: ClinicalTrials.gov Identifier: NCT04369235. Registered on 30 April 2020.

Mini-review: The Role of the Cerebellum in Visuomotor Adaptation

The incredible capability of the brain to quickly alter performance in response to ever-changing environment is rooted in the process of adaptation. The core aspect of adaptation is to fit an existing motor program to altered conditions. Adaptation to a visuomotor rotation or an external force has been well established as tools to study the mechanisms underlying sensorimotor adaptation. In this mini-review, we summarize recent findings from the field of visuomotor adaptation. We focus on the idea that the cerebellum plays a central role in the process of visuomotor adaptation and that interactions with cortical structures, in particular, the premotor cortex and the parietal cortex, may be crucial for this process. To this end, we cover a range of methodologies used in the literature that link cerebellar functions and visuomotor adaptation; behavioral studies in cerebellar lesion patients, neuroimaging and non-invasive stimulation approaches. The mini-review is organized as follows: first, we provide evidence that sensory prediction errors (SPE) in visuomotor adaptation rely on the cerebellum based on behavioral studies in cerebellar patients. Second, we summarize structural and functional imaging studies that provide insight into spatial localization as well as visuomotor adaptation dynamics in the cerebellum. Third, we discuss premotor — cerebellar interactions and how these may underlie visuomotor adaptation. And finally, we provide evidence from transcranial direct current and magnetic stimulation studies that link cerebellar activity, beyond correlational relationships, to visuomotor adaptation .

Augmented efficacy of intermittent theta burst stimulation on the virtual reality-based cycling training for upper limb function in patients with stroke: a double-blinded, randomized controlled trial

Background

Virtual reality and arm cycling have been reported as effective treatments for improving upper limb motor recovery in patients with stroke. Intermittent theta burst stimulation (iTBS) can increase ipsilesional cortical excitability, and has been increasingly used in patients with stroke. However, few studies examined the augmented effect of iTBS on neurorehabilitation program. In this study, we investigated the augmented effect of iTBS on virtual reality-based cycling training (VCT) for upper limb function in patients with stroke.

Methods

In this randomized controlled trial, 23 patients with stroke were recruited. Each patient received either 15 sessions of iTBS or sham stimulation in addition to VCT on the same day. Outcome measures were assessed before and after the intervention. Primary outcome measures for the improvement of upper limb motor function and spasticity were Fugl-Meyer Assessment-Upper Extremity (FMA-UE) and Modified Ashworth Scale Upper-Extremity (MAS-UE). Secondary outcome measures for activity and participation were Action Research Arm Test (ARAT), Nine Hole Peg Test (NHPT), Box and Block Test (BBT) and Motor Activity Log (MAL), and Stroke Impact Scale (SIS). Wilcoxon signed-rank tests were performed to evaluate the effectiveness after the intervention and Mann–Whitney U tests were conducted to compare the therapeutic effects between two groups.

Results

At post-treatment, both groups showed significant improvement in FMA-UE and ARAT, while only the iTBS + VCT group demonstrated significant improvement in MAS-UE, BBT, NHPT, MAL and SIS. The Mann–Whitney U tests revealed that the iTBS + VCT group has presented greater improvement than the sham group significantly in MAS-UE, MAL-AOU and SIS. However, there were no significant differences in the changes of the FMA-UE, ARAT, BBT, NHPT and MAL-QOM between groups.

Conclusions

Intermittent TBS showed augmented efficacy on VCT for reducing spasticity, increasing actual use of the affected upper limb, and improving participation in daily life in stroke patients. This study provided an integrated innovative intervention, which may be a promising therapy to improve upper limb function recovery in stroke rehabilitation. However, this study has a small sample size, and thus a further larger-scale study is warranted to confirm the treatment efficacy.

Trial registration This trial was registered under ClinicalTrials.gov ID No. NCT03350087, retrospectively registered, on November 22, 2017

Effects of coupling inhibitory and facilitatory repetitive transcranial magnetic stimulation on motor recovery in patients following acute cerebral infarction

BACKGROUND

The treatment for patients suffering from motor dysfunction following stroke using continuous repetitive transcranial magnetic stimulation (rTMS) has the potential to be beneficial for recovery. However, the impact of explicit results on the coupling of various rTMS protocols on motor treatment in patients following acute cerebral infarction remain unexplored.

OBJECTIVE

The current study aims to design a sham-controlled randomized report to explore the capability of consecutive suppressive-facilitatory rTMS method to increase the motor results following acute stroke.

METHODS

A hundred ischemic stroke patients suffering from motor disorder were randomly assigned to obtain 4 week sessions of (1)10 Hz over the ipsilesional primary motor cortex (M1) and next 1 Hz over the contralesional M1; (2) contralesional sham stimulation and next ipsilesional real 10 Hz; (3) contralesional real 1 Hz rTMS and next ipsilesional sham stimulation; or (4) bilateral sham-control procedures. At 24 hours before and after the intervention, we obtained cortical excitability data from study subjects. At baseline, after treatment and 3 months follow up, we additionally evaluated patients with the clinical assessments.

RESULTS

At post-intervention, group A showed greater motor improvements in FMA, FMA-UL, NIHSS, ADL and mRS values than group B, group C and group D, that were continued for at least 3 months after the completion of the treatment time. Specifically, it is shown in the cortical excitability study that the motor-evoked potential (MEP) amplitude and resting motor threshold (rMT) more significantly improved in group A than other groups. The improvement in motor function and change in motor cortex excitability exhibit a significant correlation in the affected hemisphere. The combined 1 Hz and 10 Hz stimulation treatment showed a synergistic effect.

CONCLUSIONS

Facilitatory rTMS and coupling inhibitory produced extra satisfactory results in facilitating the motor's recovery in the subacute and acute phase following stroke compared to that acquired from alone single-course modulation.

Efficacy of coupling intermittent theta-burst stimulation and 1 Hz repetitive transcranial magnetic stimulation to enhance upper limb motor recovery in subacute stroke patients: A randomized controlled trial

BACKGROUND

Both 1 Hz repetitive transcranial magnetic stimulation (rTMS) and intermittent theta-burst stimulation (iTBS) are reported to benefit upper limb motor function rehabilitation in patients with stroke. However, the efficacy of combining 1 Hz rTMS and iTBS has not been adequately explored.

OBJECTIVE

We aimed to compare the effects of 1 Hz rTMS and the combination of 1 Hz rTMS and iTBS on the upper limb motor function in the subacute phase post-stroke.

METHODS

Twenty-eight participants were randomly assigned to three groups: Group A (1 Hz rTMS over the contralesional primary motor cortex (M1) and iTBS over the ipsilesional M1), Group B (contralesional 1 Hz rTMS and ipsilesional sham iTBS), and Group C (contralesional sham 1 Hz rTMS and ipsilesional sham iTBS). The participants received the same conventional rehabilitation accompanied by sessions of transcranial magnetic stimulation for two weeks (5 days one week). Motor-evoked potential (MEP), upper extremity Fugl-Meyer Assessment (UE-FMA), and Barthel Index (BI) were performed before and after the sessions.

RESULTS

Group A showed greater UE-FMA, BI, and MEP amplitude improvement and more significant decrement in MEP latency compared to Group B and Group C in testable patients. Correlation analyses in Group A revealed a close relation between ipsilesional MEP amplitude increment and UE-FMA gain.

CONCLUSIONS

The combining of 1 Hz rTMS and iTBS protocol in the present study is tolerable and more beneficial for motor improvement than the single use of 1 Hz rTMS in patients with subacute stroke.

Human Theta Burst Stimulation Combined with Subsequent Electroacupuncture Increases Corticospinal Excitability

Objective

Intermittent theta burst stimulation (iTBS) is a widely used noninvasive brain stimulation for the facilitation of corticospinal excitability (CSE). Previous studies have shown that acupuncture applied to acupoints associated with motor function in healthy people can reduce the amplitude of the motor-evoked potentials (MEPs), which reflects the inhibition of CSE. In our work, we wanted to test whether the combination of iTBS and electroacupuncture (EA) would have different effects on CSE in humans.

Methods

A single-blind sham-controlled crossover design study was conducted on 20 healthy subjects. Subjects received 20 minutes' sham or real EA stimulation immediately after sham or real iTBS. MEPs, short-interval intracortical inhibition (SICI), intracortical facilitation (ICF), cortical silent period (CSP), and central motor conduction time (CMCT) were recorded before each trial, and immediately, 20 minutes, and 40 minutes after the end of stimulation.

Results

In the sham iTBS group, EA produced a reduction in MEPs amplitude, lasting approximately 40 minutes, while in the real iTBS group, EA significantly increased MEPs amplitude beyond 40 minutes after the end of stimulation. In sham EA group, the recorded MEPs amplitude showed no significant trend over time compared to baseline. Among all experiments, there were no significant changes in SICI, ICF, CSP, CMCT, etc.

Conclusion

These data indicate that immediate application of EA after iTBS significantly increased corticospinal excitability. This trial was registered in the Chinese Clinical Trial Registry (registration no. ChiCTR1900025348).

Does anodal tDCS improve basketball performance? A randomized controlled trial

Shooting precision as well as dribbling and agility are crucial components of performance in basketball. We examined the effects of anodal tDCS over the dominant primary motor cortex in supporting these basketball specific abilities. Fifty-two sports students were enrolled in a double-blind, randomized, placebo-controlled, crossover trial with two interventions. Twenty minutes of anodal 1 mA tDCS/sham tDCS were applied over the primary motor cortex of the dominant hemisphere. Basketball shooting precision (basketball shooting accuracy test) and basketball specific dribbling and agility (Illinois ball-dribbling test) were tested prior and after each intervention. Basketball shooting precision and basketball specific dribbling and agility improved after real tDCS but not after sham tDCS. ANOVAs show significant intervention*time effects on both the shooting accuracy test (F_1,51= 5.6; P = 0.022) and on the Illinois ball-dribbling test (F_1,51 = 4.5; P = 0.038). Anodal 1 mA tDCS over the dominant primary motor cortex is effective in supporting short-term performance in basketball. However, the available data is insufficient for application of this novel method within the framework of conventional sports training.

Funktionserholung nach Schlaganfall und die therapeutische Rolle der nicht-invasiven Hirnstimulation

Im Bereich der non-invasiven Hirnstimulation stellen die transkranielle Magnetstimulation (engl. transcranial magnetic stimulation, TMS) sowie die transkranielle Gleichstromstimulation (engl. transcranial direct current stimulation, tDCS) bis heute die wichtigsten Techniken zur Modulation kortikaler Erregbarkeit dar. Beide Verfahren induzieren Nacheffekte, welche die Zeit der reinen Stimulation überdauern, und ebnen damit den Weg für ihren therapeutischen Einsatz beim Schlaganfall. In diesem Übersichtsartikel diskutieren wir die aktuelle Datenlage TMS- und tDCS-vermittelter Therapien für die häufigsten schlaganfallbedingten Defizite wie Hemiparese, Aphasie und Neglect. Darüber hinaus adressieren wir mögliche Einschränkungen der gegenwärtigen Ansätze und zeigen Ansatzpunkte auf, um Neuromodulation nach Schlaganfall effektiver zu gestalten und damit das Outcome der Patienten zu verbessern.

Connectivity-Related Roles of Contralesional Brain Regions for Motor Performance Early after Stroke

Hemiparesis after stroke is associated with increased neural activity not only in the lesioned but also in the contralesional hemisphere. While most studies have focused on the role of contralesional primary motor cortex (M1) activity for motor performance, data on other areas within the unaffected hemisphere are scarce, especially early after stroke. We here combined functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) to elucidate the contribution of contralesional M1, dorsal premotor cortex (dPMC), and anterior intraparietal sulcus (aIPS) for the stroke-affected hand within the first 10 days after stroke. We used “online” TMS to interfere with neural activity at subject-specific fMRI coordinates while recording 3D movement kinematics. Interfering with aIPS activity improved tapping performance in patients, but not healthy controls, suggesting a maladaptive role of this region early poststroke. Analyzing effective connectivity parameters using a Lasso prediction model revealed that behavioral TMS effects were predicted by the coupling of the stimulated aIPS with dPMC and ipsilesional M1. In conclusion, we found a strong link between patterns of frontoparietal connectivity and TMS effects, indicating a detrimental influence of the contralesional aIPS on motor performance early after stroke.

Recovery from stroke: current concepts and future perspectives

Stroke is a leading cause of acquired, permanent disability worldwide. Although the treatment of acute stroke has been improved considerably, the majority of patients to date are left disabled with a considerable impact on functional independence and quality of life. As the absolute number of stroke survivors is likely to further increase due to the demographic changes in our aging societies, new strategies are needed in order to improve neurorehabilitation. The most critical driver of functional recovery post-stroke is neural reorganization. For developing novel, neurobiologically informed strategies to promote recovery of function, an improved understanding of the mechanisms enabling plasticity and recovery is mandatory. This review provides a comprehensive survey of recent developments in the field of stroke recovery using neuroimaging and non-invasive brain stimulation. We discuss current concepts of how the brain reorganizes its functional architecture to overcome stroke-induced deficits, and also present evidence for maladaptive effects interfering with recovery. We demonstrate that the combination of neuroimaging and neurostimulation techniques allows a better understanding of how brain plasticity can be modulated to promote the reorganization of neural networks. Finally, neurotechnology-based treatment strategies allowing patient-tailored interventions to achieve enhanced treatment responses are discussed. The review also highlights important limitations of current models, and finally closes with possible solutions and future directions.

Effective connectivity differences in motor network during passive movement of paretic and non-paretic ankles in subacute stroke patients

Background

A better understanding of the neural changes associated with paresis in stroke patients could have important implications for therapeutic approaches. Dynamic Causal Modeling (DCM) for functional magnetic resonance imaging (fMRI) is commonly used for analyzing effective connectivity patterns of brain networks due to its significant property of modeling neural states behind fMRI signals. We applied this technique to analyze the differences between motor networks (MNW) activated by continuous passive movement (CPM) of paretic and non-paretic ankles in subacute stroke patients. This study aimed to identify CPM induced connectivity characteristics of the primary sensory area (S1) and the differences in extrinsic directed connections of the MNW and to explain the hemodynamic differences of brain regions of MNW.

Methods

For the network analysis, we used ten stroke patients’ task fMRI data collected under CPMs of both ankles. Regions for the MNW, the primary motor cortex (M1), the premotor cortex (PM), the supplementary motor area (SMA) and the S1 were defined in a data-driven way, by independent component analysis. For the network analysis of both CPMs, we compared twelve models organized into two model-families, depending on the S1 connections and input stimulus modeling. Using DCM, we evaluated the extrinsic connectivity strengths and hemodynamic parameters of both stimulations of all patients.

Results

After a statistical comparison of the extrinsic connections and their modulations of the “best model”, we concluded that three contralateral self-inhibitions (cM1, cS1 and cSMA), one contralateral inter-regional connection (cSMA→cM1), and one interhemispheric connection (cM1→iM1) were significantly different. Our research shows that hemodynamic parameters can be estimated with the Balloon model using DCM but the parameters do not change with stroke.

Conclusions

Our results confirm that the DCM-based connectivity analyses combined with Bayesian model selection may be a useful technique for quantifying the alteration or differences in the characteristics of the motor network in subacute stage stroke patients and in determining the degree of MNW changes.

Neurotechnology-aided interventions for upper limb motor rehabilitation in severe chronic stroke

Upper limb motor deficits in severe stroke survivors often remain unresolved over extended time periods. Novel neurotechnologies have the potential to significantly support upper limb motor restoration in severely impaired stroke individuals. Here, we review recent controlled clinical studies and reviews focusing on the mechanisms of action and effectiveness of single and combined technology-aided interventions for upper limb motor rehabilitation after stroke, including robotics, muscular electrical stimulation, brain stimulation and brain computer/machine interfaces. We aim at identifying possible guidance for the optimal use of these new technologies to enhance upper limb motor recovery especially in severe chronic stroke patients. We found that the current literature does not provide enough evidence to support strict guidelines, because of the variability of the procedures for each intervention and of the heterogeneity of the stroke population. The present results confirm that neurotechnology-aided upper limb rehabilitation is promising for severe chronic stroke patients, but the combination of interventions often lacks understanding of single intervention mechanisms of action, which may not reflect the summation of single intervention’s effectiveness. Stroke rehabilitation is a long and complex process, and one single intervention administrated in a short time interval cannot have a large impact for motor recovery, especially in severely impaired patients. To design personalized interventions combining or proposing different interventions in sequence, it is necessary to have an excellent understanding of the mechanisms determining the effectiveness of a single treatment in this heterogeneous population of stroke patients. We encourage the identification of objective biomarkers for stroke recovery for patients’ stratification and to tailor treatments. Furthermore, the advantage of longitudinal personalized trial designs compared to classical double-blind placebo-controlled clinical trials as the basis for precise personalized stroke rehabilitation medicine is discussed. Finally, we also promote the necessary conceptual change from ‘one-suits-all’ treatments within in-patient clinical rehabilitation set-ups towards personalized home-based treatment strategies, by adopting novel technologies merging rehabilitation and motor assistance, including implantable ones.

Single session of repetitive transcranial magnetic stimulation to left dorsolateral prefrontal cortex increased dual-task gait speed in chronic stroke: A pilot study

BACKGROUND

Individuals with stroke often experience difficulty in dual-task walking and are prone to falling when walking and talking. Previous studies in other populations have suggested that non-invasive brain stimulation could enhance dual-task gait performance by stimulating dorsolateral prefrontal cortex (DLPFC) or supplementary motor area (SMA). It was unclear if the benefits of brain stimulation would be observed in individuals with stroke.

RESEARCH QUESTION

Would single-session 5 Hz rTMS applied to DLPFC or SMA improve dual-task gait performance in individuals with stroke?

METHODS

This single group repeated measure study included fifteen individuals with left chronic stroke (mean age = 58 years). Participants received 5 Hz rTMS to either DLPFC, SMA, or M1 of the left lesioned hemisphere across three different sessions. Single- and dual-task gait speed was assessed before and after rTMS with the dualtask gait being walking and counting backward by 3 s.

RESULTS

We observed that rTMS to left DLPFC resulted in a greater increase in dual-task gait speed, but not single-task gait speed, compared to the other two stimulation sites (M1 and SMA) but the difference was not statistically significant (p = 0.06). Five out of fifteen participants demonstrated a clinically significant improvement in dual-task gait speed (> 0.1 m/s) after rTMS to DLPFC.

SIGNIFICANCES

The results suggest that DLPFC could be a potential treatment target to improve dual-task gait performance in persons with chronic stroke.

Concurrent human TMS-EEG-fMRI enables monitoring of oscillatory brain state-dependent gating of cortico-subcortical network activity

Despite growing interest, the causal mechanisms underlying human neural network dynamics remain elusive. Transcranial Magnetic Stimulation (TMS) allows to noninvasively probe neural excitability, while concurrent fMRI can log the induced activity propagation through connected network nodes. However, this approach ignores ongoing oscillatory fluctuations which strongly affect network excitability and concomitant behavior. Here, we show that concurrent TMS-EEG-fMRI enables precise and direct monitoring of causal dependencies between oscillatory states and signal propagation throughout cortico-subcortical networks. To demonstrate the utility of this multimodal triad, we assessed how pre-TMS EEG power fluctuations influenced motor network activations induced by subthreshold TMS to right dorsal premotor cortex. In participants with adequate motor network reactivity, strong pre-TMS alpha power reduced TMS-evoked hemodynamic activations throughout the bilateral cortico-subcortical motor system (including striatum and thalamus), suggesting shunted network connectivity. Concurrent TMS-EEG-fMRI opens an exciting noninvasive avenue of subject-tailored network research into dynamic cognitive circuits and their dysfunction.

Evidence-based guidelines on the therapeutic use of repetitive transcranial magnetic stimulation (rTMS): An update (2014-2018)

A group of European experts reappraised the guidelines on the therapeutic efficacy of repetitive transcranial magnetic stimulation (rTMS) previously published in 2014 [Lefaucheur et al., Clin Neurophysiol 2014;125:2150-206]. These updated recommendations take into account all rTMS publications, including data prior to 2014, as well as currently reviewed literature until the end of 2018. Level A evidence (definite efficacy) was reached for: high-frequency (HF) rTMS of the primary motor cortex (M1) contralateral to the painful side for neuropathic pain; HF-rTMS of the left dorsolateral prefrontal cortex (DLPFC) using a figure-of-8 or a H1-coil for depression; low-frequency (LF) rTMS of contralesional M1 for hand motor recovery in the post-acute stage of stroke. Level B evidence (probable efficacy) was reached for: HF-rTMS of the left M1 or DLPFC for improving quality of life or pain, respectively, in fibromyalgia; HF-rTMS of bilateral M1 regions or the left DLPFC for improving motor impairment or depression, respectively, in Parkinson's disease; HF-rTMS of ipsilesional M1 for promoting motor recovery at the post-acute stage of stroke; intermittent theta burst stimulation targeted to the leg motor cortex for lower limb spasticity in multiple sclerosis; HF-rTMS of the right DLPFC in posttraumatic stress disorder; LF-rTMS of the right inferior frontal gyrus in chronic post-stroke non-fluent aphasia; LF-rTMS of the right DLPFC in depression; and bihemispheric stimulation of the DLPFC combining right-sided LF-rTMS (or continuous theta burst stimulation) and left-sided HF-rTMS (or intermittent theta burst stimulation) in depression. Level A/B evidence is not reached concerning efficacy of rTMS in any other condition. The current recommendations are based on the differences reached in therapeutic efficacy of real vs. sham rTMS protocols, replicated in a sufficient number of independent studies. This does not mean that the benefit produced by rTMS inevitably reaches a level of clinical relevance.

Intermittent theta burst stimulation applied during early rehabilitation after stroke: study protocol for a randomised controlled trial

INTRODUCTION

Intermittent theta burst stimulation (iTBS) applied to primary motor cortex (M1) has been shown to modulate both the excitability and connectivity of the motor system. A recent proof-of-principle study, based on a small group of hospitalised patients with acute ischemic stroke, suggested that iTBS applied to the ipsilesional M1 combined with physical therapy early after stroke can amplify motor recovery with lasting after effects. A randomised controlled clinical trial using a double-blind design is warranted to justify the implementation of iTBS-assisted motor rehabilitation in neurorehabilitation from an acute ischaemic stroke.

METHODS/DESIGN

We investigate the effects of daily iTBS on early motor rehabilitation after stroke in an investigator-initiated, longitudinal randomised controlled trial. Patients (n=150) with hemiparesis receive either iTBS (600 pulses) applied to the ipsilesional motor cortex (M1) or a control stimulation (ie, coil placement over the parieto-occipital vertex in parallel to the interhemispheric fissure and with a tilt of 45°). On 8 consecutive workdays, a 45 min arm-centred motor training follows the intervention . The relative grip strength, defined as the grip force ratios of the affected and unaffected hands, serves as the primary outcome parameter. Secondary outcome parameters are measures of arm function (Action Research Arm Test, Fugl-Meyer Motor Scale), stroke severity (National Institutes of Health Stroke Scale), stroke-induced disability (modified Rankin Scale, Barthel Index), duration of inpatient rehabilitation, quality of life (EuroQol 5D), motor evoked potentials and the resting motor threshold of the ipsilesional M1.

ETHICS AND DISSEMINATION

The study was approved by the Ethics Commission of the Medical Faculty, University of Cologne, Germany (reference number 15-343). Data will be disseminated through peer-reviewed publications and presentations at conferences. Study title: Theta-Burst Stimulation in Early Rehabilitation after Stroke (acronym: TheSiReS). Study registration at German Registry for Clinical Trials (DRKS00008963) and at ClinicalTrials.gov (NCT02910024).

Finger Tapping Task Activation vs. TMS Hotspot: Different Locations and Networks

Both functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) have been used to non-invasively localize the human motor functional area. These locations can be clinically used as stimulation target of TMS treatment. However, it has been reported that the finger tapping fMRI activation and TMS hotspot were not well-overlapped. The aim of the current study was to measure the distance between the finger tapping fMRI activation and the TMS hotspot, and more importantly, to compare the network difference by using resting-state fMRI. Thirty healthy participants underwent resting-state fMRI, task fMRI, and then TMS hotspot localization. We found significant difference of locations between finger tapping fMRI activation and TMS hotspot. Specifically, the finger tapping fMRI activation was more lateral than the TMS hotspot in the premotor area. The fMRI activation peak and TMS hotspot were taken as seeds for resting-state functional connectivity analyses. Compared with TMS hotspot, finger tapping fMRI activation peak showed more intensive functional connectivity with, e.g., the bilateral premotor, insula, putamen, and right globus pallidus. The findings more intensive networks of finger tapping activation than TMS hotspot suggest that TMS treatment targeting on the fMRI activation area might result in more remote effects and would be more helpful for TMS treatment on movement disorders.

Single Sessions of High-Definition Transcranial Direct Current Stimulation Do Not Alter Lower Extremity Biomechanical or Corticomotor Response Variables Post-stroke

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique used to modulate cortical activity. However, measured effects on clinically relevant assessments have been inconsistent, possibly due to the non-focal dispersion of current from traditional two electrode configurations. High-definition (HD)-tDCS uses a small array of electrodes (N = 5) to improve targeted current delivery. The purpose of this study was to determine the effects of a single session of anodal and cathodal HD-tDCS on gait kinematics and kinetics and the corticomotor response to transcranial magnetic stimulation (TMS) in individuals post-stroke. We hypothesized that ipsilesional anodal stimulation would increase the corticomotor response to TMS leading to beneficial changes in gait. Eighteen participants post-stroke (average age: 64.8 years, SD: 12.5; average months post-stroke: 54, SD: 42; average lower extremity Fugl-Meyer score: 26, SD: 6) underwent biomechanical and corticomotor response testing on three separate occasions prior to and after HD-tDCS stimulation. In a randomized order, anodal, cathodal, and sham HD-tDCS were applied to the ipsilesional motor cortex for 20 min while participants pedaled on a recumbent cycle ergometer. Gait kinetic and kinematic data were collected while walking on an instrumented split-belt treadmill with motion capture. The corticomotor response of the paretic and non-paretic tibialis anterior (TA) muscles were measured using neuronavigated TMS. Repeated measures ANOVAs using within-subject factors of time point (pre, post) and stimulation type (sham, anodal, cathodal) were used to compare effects of HD-tDCS stimulation on measured variables. HD-tDCS had no effect on over ground walking speed (P > 0.41), or kinematic variables (P > 0.54). The corticomotor responses of the TA muscles were also unaffected by HD-tDCS (resting motor threshold, P = 0.15; motor evoked potential (MEP) amplitude, P = 0.25; MEP normalized latency, P = 0.66). A single session of anodal or cathodal HD-tDCS delivered to a standardized ipsilesional area of the motor cortex does not appear to alter gait kinematics or corticomotor response post-stroke. Repeated sessions and individualized delivery of HD-tDCS may be required to induce beneficial plastic effects. Contralesional stimulation should also be investigated due to the altered interactions between the cerebral hemispheres post-stroke.

Different Brain Connectivity between Responders and Nonresponders to Dual-Mode Noninvasive Brain Stimulation over Bilateral Primary Motor Cortices in Stroke Patients

Noninvasive brain stimulation (NBS), such as repetitive transcranial magnetic stimulation (rTMS) or transcranial direct current stimulation (tDCS), has been used in stroke patients with motor impairment. NBS can help recovery from brain damage by modulating cortical excitability. However, the efficacy of NBS varies among individuals. To obtain insights of responsiveness to the efficacy of NBS, we investigated characteristic changes of the motor network in responders and nonresponders of NBS over the primary motor cortex (M1). A total of 21 patients with subacute stroke (13 males, mean age 59.6 ± 11.5 years) received NBS in the same manner: 1 Hz rTMS on the contralesional M1 and anodal tDCS on the ipsilesional M1. Participants were classified into responders and nonresponders based on the functional improvement of the affected upper extremity after applying NBS. Twelve age-matched healthy controls (8 males, mean age 56.1 ± 14.3 years) were also recruited. Motor networks were constructed using resting-state functional magnetic resonance imaging. M1 intrahemispheric connectivity, interhemispheric connectivity, and network efficiency were measured to investigate differences in network characteristics between groups. The motor network characteristics were found to differ between both groups. Specifically, M1 intrahemispheric connectivity in responders showed a noticeable imbalance between affected and unaffected hemispheres, which was markedly restored after NBS. The responders also showed greater interhemispheric connectivity and higher efficiency of the motor network than the nonresponders. These results may provide insight on patient-specific NBS treatment based on the brain network characteristics in neurorehabilitation of patients with stroke. This trial is registered with trial registration number NCT03390192.

Modulation of task-related cortical connectivity in the acute and subacute phase after stroke

The functional relevance of cortical reorganization post-stroke is still not well understood. In this study, we investigated task-specific modulation of cortical connectivity between neural oscillations in key motor regions during the early phase after stroke. EEG and EMG recordings were examined from 15 patients and 18 controls during a precision grip task using the affected hand. Each patient attended two sessions in the acute and subacute phase (median of 3 and 34 days) post-stroke. Dynamic causal modelling (DCM) for induced responses was used to investigate task-specific modulations of oscillatory couplings in a bilateral network comprising supplementary motor area (SMA), dorsal premotor cortex (PMd) and primary motor cortex (M1). Fourteen models were constructed for each subject, and the input induced by the experimental manipulation (task) was set to inferior parietal lobule (IPL). Bayesian model selection favoured a fully connected model. A reduced coupling from SMA and intact M1 in the γ-band (31-48 Hz) to lesioned M1 in the β-band (15-30 Hz) was observed in patients in the acute phase compared to controls. Behavioural performance improved significantly in the subacute phase, while an increased positive coupling from intact PMd to lesioned M1 and a less negative modulation from lesioned M1 to intact M1 were observed for patients compared to controls both from the γ-band to the β-band. We infer that the observed differences in cross-frequency cortical interactions are important for functional recovery.

Network dynamics engaged in the modulation of motor behavior in stroke patients

Stroke patients with motor deficits typically feature enhanced neural activity in several cortical areas when moving their affected hand. However, also healthy subjects may show higher levels of neural activity in tasks with higher motor demands. Therefore, the question arises to what extent stroke-related overactivity reflects performance-level-associated recruitment of neural resources rather than stroke-induced neural reorganization. We here investigated which areas in the lesioned brain enable the flexible adaption to varying motor demands compared to healthy subjects. Accordingly, eleven well-recovered left-hemispheric chronic stroke patients were scanned using functional magnetic resonance imaging. Motor system activity was assessed for fist closures at increasing movement frequencies performed with the affected/right or unaffected/left hand. In patients, an increasing movement rate of the affected hand was associated with stronger neural activity in ipsilesional/left primary motor cortex (M1) but unlike in healthy controls also in contralesional/right dorsolateral premotor cortex (PMd) and contralesional/right superior parietal lobule (SPL). Connectivity analyses using dynamic causal modeling revealed stronger coupling of right SPL onto affected/left M1 in patients but not in controls when moving the affected/right hand independent of the movement speed. Furthermore, coupling of right SPL was positively coupled with the "active" ipsilesional/left M1 when stroke patients moved their affected/right hand with increasing movement frequency. In summary, these findings are compatible with a supportive role of right SPL with respect to motor function of the paretic hand in the reorganized brain.