Bilateral Transcranial Direct Stimulation Over the Primary Motor Cortex Alters Motor Modularity of Multiple Muscles

Abstract

Transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) has been demonstrated to modulate the motor performance of both healthy individuals and patients with neuromuscular disorders. However, the effect of tDCS on motor control of multiple muscles, which is a prerequisite to change in motor performance, is currently unknown. Using dimensionality reduction analysis, we investigated whether bilateral tDCS over M1 modulates the coordinated activity of 12 muscles. Fifteen healthy men participated in this randomized, double-blind crossover study. Each participant received a 20-min sham and 2-mA stimulation bilaterally over M1 (anode on the right M1 and cathode on the left M1), with a minimum washout period of 4?days. Muscle activation and end-point kinematics were evaluated during a task where participants reached out to a marked target with non-dominant hand as fast as possible, before and immediately after tDCS application. We found decreased similarity in motor modularity and significant changes in muscle activation in a specific motor module, particularly when reaching out to a target placed within arm’s length and improved smoothness index of movement only following 2-mA stimulation. These findings indicate that clinicians and researchers need to consider the simultaneous effect of bilateral tDCS over M1 on multiple muscles when they establish tDCS protocol to change in motor performance of patients with neuromuscular deficits.     

Lower Extremity Kinetics for Balance Control in Children With Cerebral Palsy

The authors examined and compared the effect of support-surface perturbations of various magnitudes on lower extremity kinetics of 7 children with cerebral palsy (CP) and 8 typically developing (TD) children. Results showed that the highest velocity tolerated without stepping was slower in children with CP than in either age-matched TD or younger TD children. Multimodal torque profiles were more frequent in children with CP than in TD controls. TD groups temporally and spatially organized torque activation, whereas children with CP activated all joints simultaneously and showed altered torque contribution patterns among joints. Those results suggest that impairments in reactive postural control in children with CP result not only from developmental delay but also from pathology. Evidence for pathology included increased numbers of torque bursts required to regain stability and less efficient temporal and spatial organization of torque activation patterns.     

Coping Strategies and Resolution in Mothers of Children With Cerebral Palsy

“Parental resolution” represents parents coming to terms with their child’s health condition. Differences in the use of coping strategies between mothers who were resolved versus unresolved to their child’s diagnosis was investigated, and a possible moderating effect of these strategies was explored. A strategy aimed at mobilizing the family to acquire and accept help (institutional, formal support) was shown to be a significant moderating variable, in a way that its more frequent use allowed mothers of children with better functional status (but not mothers of children with poorer functional status) to reach resolution.     

Enhancing Creativity With Combined Transcranial Direct Current and Random Noise Stimulation of the Left Dorsolateral Prefrontal Cortex and Inferior Frontal Gyrus

Creativity is a fundamental human accomplishment from scientific advances to composing music. The left dorsolateral prefrontal cortex (DLPFC) and inferior frontal gyrus (IFG) are important metacontrol hubs in flexibility and persistence brain states, respectively. Those hubs are related to divergent thinking, insight problem-solving, and convergent thinking. In this double-blind, between-subjects study, 81 healthy participants were randomly assigned to one of three groups (n = 27) that received a combined transcranial direct current stimulation–transcranial random noise stimulation (tDCS-tRNS) protocol with the anode over the left DLPFC and cathode over the left IFG (+DLPFC−IFG), the opposite montage (−DLPFC+IFG), and a sham group (+DLPFC−IFG). Both active tDCS-tRNS groups received 20 min of 1 mA tDCS with 1 mA (100–500 Hz) tRNS. Creativity was assessed before (baseline) and during stimulation with the Unusual Uses, Picture Completion (PC), Remote Association test (RAT), Matchstick Arithmetic (MA), and Nine-dot (ND) problems. Only the +DLPFC−IFG group had significantly higher scores compared with sham in the RAT (p = .009), PC fluency (p = .018), PC originality (p = .007), ND (p = .007), and MA (p = .032). Overall, −DLPFC+IFG had greater scores in all creativity tests compared with sham. Implications from the metacontrol theory are discussed.     

Effects of Visual Manipulation in Sit-to-Stand Movement in Children With Cerebral Palsy

The authors sought to verify the effects of vision on sit-to-stand (STS) movement performance by means of postural sway in children with cerebral palsy (CP) and typical children (TC). Participants were 42 TC and 21 children with CP. STS movement was assessed with eyes open and with eyes closed. Area and velocity of center of pressure sway were analyzed in each of the 3 STS phases. We observed greater postural sway during STS movement with eyes closed. Children with CP presented greater postural sway than TC did. Both groups exhibited greater postural instability with absence of vision expressing the role of vision to keep postural stability. Moreover, the greater postural instability was observed in children with CP.     

Motor Improvement Using Motion Sensing Game Devices for Cerebral Palsy Rehabilitation

The authors aimed to investigate the effects of an intervention based on interactive game set with the movement sensor Kinect on children with cerebral palsy (CP). Twenty-eight participants were recruited. Their age was between 3 and 12 years old, and rated as level I, II, or III on the Gross Motor Function Classification System. They played two games from the Xbox 360 Kinect system and were evaluated using the Gross Motor Function Measure (GMFM) after a period of 8 weeks. The intervention led to significant motor function improvement as increase of the global scores on the GMFM (p < .001). Rehabilitation interventions using the Xbox 360 Kinect interactive games may represent useful tools for children with CP.     

Hands Support and Postural Oscillation During Sit-to-Stand Movement in Children With Cerebral Palsy and Typical Children

The authors aimed to compare the weight bearing on hands during sit-to-stand (STS) movement in children with cerebral palsy (CP) and typical children (TC), verify its effect on postural oscillation, and analyze the relationship between weight bearing on hands and postural oscillation. Twenty children with CP (Gross Motor Function Classification System levels I and II) and 35 TC performed STS with and without anterior hands support. Mann-Whitney test compared weight bearing between groups. Wilcoxon test investigated differences in postural oscillation between the conditions with and without anterior hand support for both groups. The Spearman correlation tested the relationship between weight-bearing and postural oscillation during the hand support condition. Children with CP bore more weight on hands than TC to perform STS. The hand support reduced postural oscillation during the second phase of STS in both groups. In the CP group, greater weight bearing was related with lower postural oscillation in the beginning of STS. Although children with CP were able to perform STS without support, they bore more weight on their hands to perform the task than TC. Moreover, children with CP and TC use mechanical and somatosensory information to modulate their postural control during STS in different ways.     

Stress and Coping: A Comparison of Self-Report Measures of Functioning in Families of Young Children with Cerebral Palsy or No Medical Diagnosis

We analyzed data from 87 mothers of children ages 15 to 44 months with cerebral palsy (CP) or no diagnosis, who completed the Dyadic Adjustment Scale, Parenting Stress Index, Support Functions Scale, and Inventory of Social Support. Principal components analysis of the 15 subscales from the 5 measures revealed few cross-measure loadings. Mothers of children with CP (severe or mild) reported higher levels of parenting stress than did mothers of controls. However, cluster analysis of self-report measures yielded a 5-cluster solution, with no diagnostic group differences across clusters. That is, there were no overall differences in self-reported family functioning according to presence or severity of the child's disability. The results are discussed in terms of the organization of family systems and their relationship to child diagnosis. Clinical implications for assessing and working with families are noted.     

Noninvasive Brain Stimulation over the M1 Enhances Bimanual Force Control Ability: A Randomized Double-Blind Sham-Controlled Study

Well-coordinated bimanual force control is common in daily life. We investigated the effects of anodal transcranial direct current stimulation (tDCS) over the primary motor cortex on bimanual force control. Under a cross-over study, young adults (n = 19; female = 6, male = 13) completed three bimanual force control tasks at 5%, 25%, and 50% of bimanual maximum voluntary force (BMVF) before and after real or sham tDCS. Real tDCS enhanced accuracy at all BMVF, reduced variability at 5% BMVF, and increased coordination at 5% BMVF. Real tDCS improved force control at 5% and 25% BMVF, and especially increased bimanual coordination at 5% BMVF. These findings might have implications for establishing interventions for patients with hand force control deficits.     

Self-Optimization of Walking in Nondisabled Children and Children With Spastic Hemiplegic Cerebral Palsy

Children voluntarily adopt a frequency and movement pattern for walking. The force-driven harmonic oscillator (FDHO) model was used in this study for accurate prediction of the preferred walking frequency of nondisabled children and children with spastic hemiplegic cerebral palsy. Four potential optimality criteria with which the preferred walking pattern was forced to comply were examined: minimization of physiological costs, maximization of mechanical energy conservation, minimization of asymmetry in lower limb movements and minimization of variability of interlimb and intralimb coordination. Age and gender-matched nondisabled children (n = 6) and children with spastic hemiplegic cerebral palsy (n = 6) were tested under six frequency conditions of walking at a constant speed on a treadmill. For the nondisabled children, the results indicated that their preferred walking frequency could be accurately predicted by the FDHO model. They freely adopted a walking pattern that minimized physiological costs, asymmetry, and variability of inter- and intralimb coordination. For the children with spastic hemiplegic cerebral palsy, the prediction of preferred overground walking frequency required that the FDHO model be modified to account for muscle mass and leg length discrepancies between limbs and increased stiffness. Most of the children achieved the same optimality goals as the nondisabled when walking at the preferred frequency. However, the children were found to use different mechanisms to attain these goals: for example, a steeper increase observed in physiological cost at higher frequencies; a lowered center of gravity of the body, which allowed for angular symmetry; and greater variability of between-joint coordination in the nonaffected limb and less variability in the affected limb.     

Influence of Motor Cortex Stimulation During Motor Training on Neuroplasticity as a Potential Therapeutic Intervention

Rehabilitation options to promote neuroplasticity may be enhanced when patients are engaged in motor practice during repetitive transcranial magnetic stimulation (rTMS). Twelve participants completed 3 separate sessions: motor practice, motor practice with rTMS, and rTMS only: motor practice consisted of 30 isometric contractions and subthreshold rTMS was 30, 3-s trains at 10 Hz. Assessments included the Box and Block Test (BBT), force steadiness (10% of the maximum voluntary contraction), and TMS (cortical excitability, intracortical inhibition, and intracortical facilitation). Participants significantly increased BBT scores following the combined condition. Force steadiness improved after all 3 conditions (p < .05). TMS outcomes depended on intervention condition with significant increases in facilitation following the motor practice plus rTMS condition. All interventions influenced motor control, yet are likely modulated differently when combining motor practice plus rTMS. These results help guide the clinical utility of rTMS as an intervention to influence motor control.     

Working memory improvement with non-invasive brain stimulation of the dorsolateral prefrontal cortex: A systematic review and meta-analysis

Recent studies have used non-invasive brain stimulation (NIBS) techniques, such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS), to increase dorsolateral prefrontal cortex (DLPFC) activity and, consequently, working memory (WM) performance. However, such experiments have yielded mixed results, possibly due to small sample sizes and heterogeneity of outcomes. Therefore, our aim was to perform a systematic review and meta-analyses on NIBS studies assessing the n-back task, which is a reliable index for WM. From the first data available to February 2013, we looked for sham-controlled, randomized studies that used NIBS over the DLPFC using the n-back task in PubMed/MEDLINE and other databases. Twelve studies (describing 33 experiments) matched our eligibility criteria. Active vs. sham NIBS was significantly associated with faster response times (RTs), higher percentage of correct responses and lower percentage of error responses. However, meta-regressions showed that tDCS (vs. rTMS) presented only an improvement in RT, and not in accuracy. This could have occurred in part because almost all tDCS studies employed a crossover design, possibly due to the reliable tDCS blinding. Study design was also associated with no improvement in correct responses in the active vs. sham groups. To conclude, rTMS of the DLPFC significantly improved all measures of WM performance whereas tDCS significantly improved RT, but not the percentage of correct and error responses. Mechanistic insights on the role of DLPFC in WM are further discussed, as well as how NIBS techniques could be used in neuropsychiatric samples presenting WM deficits, such as major depression, dementia and schizophrenia.     

经颅直流电刺激在注意缺陷多动障碍治疗中的应用

经颅直流电刺激(tDCS)治疗注意缺陷多动障碍(ADHD)主要是选取患者的背外侧前额叶(DLPFC)作为刺激区域, 通过调节其皮层兴奋性, 从而缓解其ADHD的症状和改善其受损的认知功能。针对tDCS在ADHD治疗研究中的问题, 未来可从有效性、确定最佳刺激参数、个体差异、不同亚型及与其他疗法联合使用等五个方面来进一步研究。     

腹内侧前额叶在内隐认知重评中的因果作用

情绪调节对维持个体心理健康、适应社会生活十分重要, 然而以往研究主要关注外显情绪调节, 目前我们对内隐情绪调节的认知神经机制的了解还非常有限。为揭示内隐情绪调节的核心脑区, 本研究使用句子整理任务启动内隐认知重评, 并采用经颅直流电刺激(transcranial direct current stimulation, tDCS)激活内侧前额叶特别是腹内侧前额叶(ventromedial prefrontal cortex, vmPFC), 考察该脑区在内隐情绪调节中的因果作用。结果表明, vmPFC被激活的被试组(实验组, n = 40)在内隐认知重评启动条件下比tDCS伪刺激组(对照组, n = 40), 在观看负性图片时报告了更少的负性情绪, 同时负性图片诱发的晚正成分(late positive potential, LPP)波幅更低(LPP是情绪体验强度的客观指标)。同时, 实验组比对照组在观看负性图片时表现出更低的枕区P1波幅(P1为早期视觉注意程度的客观指标)。以上结果说明, 激活以vmPFC为代表的内侧前额叶不但能增强内隐情绪调节的效果, 还能减少被试对负性刺激的早期注意分配。本研究是采用tDCS技术考察启动引起的内隐情绪调节的首次尝试, 研究结果不但表明了以vmPFC为代表的内侧前额叶在内隐认知重评中的关键作用, 还为临床应用研究指出了增强内隐情绪调节能力的神经调控潜在靶点。     

Predictors of Reading Comprehension in Children with Cerebral Palsy and Typically Developing Children

Predictors of reading comprehension were evaluated in 41 children with cerebral palsy and 74 typically developing children between the ages of 6 and 12 years. Regression analyses were conducted to determine the relative contributions of measures of phonemic awareness, receptive vocabulary, and general reasoning to variance in reading comprehension. All three independent variables were statistically significant predictors of reading comprehension in both groups of participants. The impact of phonemic awareness on reading comprehension was moderated by age, but only in the typically developing group. Within the group with cerebral palsy, there was an indirect effect of functional expressive ability on reading comprehension, mediated by phonemic awareness. It is concluded that largely the same variables predict reading comprehension in children with cerebral palsy as in typically developing children, but that children with cerebral palsy continue to rely on phonological processing for a more protracted period of time.     

Age-related Changes in Postural Sway During Sit-to-stand in Typical Children and Children with Cerebral Palsy

Objective: To assess age-related changes in postural sway during sit-to-stand (STS) in typical children (TC) and children with mild cerebral palsy (CP). Methods: Thirty-five TC and 23 children with mild CP were allocated in four different age groups: 5–6, 7–9, 10–12, and 13–15 years; they all performed STS movements over a force plate. Anterior-posterior and medial-lateral amplitude of center of pressure (CoP) displacement, area and velocity of CoP sway were analyzed and compared between the age groups for TC and children with CP. Results: TC at 5 to 6 years of age showed higher values of anterior-posterior CoP displacement and Area of CoP sway than at 10–12 years, during the stabilization phase. There were no age-related changes for CP. Conclusion: TC change their postural sway during the last STS phase over the years, reducing their body sway. Children with CP did not show age-related changes in sway during STS, reflecting a distinct rhythm of postural control development in this population.     

经颅直流电刺激在抑郁症治疗中的应用

已有的神经影像学研究成果揭示, 抑郁症发作的重要原因之一是大脑前额叶皮层结构和功能受损。经颅直流电刺激(tDCS)作为一种无创脑刺激, 选取前额叶皮层作为刺激区域, 通过调节皮层兴奋性来治疗抑郁症, 能够有效缓解抑郁症状和改善受损的认知功能, 疗效明显且持久稳定。针对tDCS在抑郁症治疗研究中的问题, 未来可从有效性、个体差异以及预防干预等六个方面进一步研究, 以期tDCS作为一种具有潜力的治疗手段, 在临床上有更为广泛地应用。     

右腹外侧前额叶对高抑郁水平成年人社会情绪调节的作用：一项tDCS研究

已有的经颅直流电刺激(transcranial direct current stimulation, tDCS)研究证明, 右腹外侧前额叶(right ventrolateral prefrontal cortex, RVLPFC)是社会情绪调节的重要脑区, 激活RVLPFC可显著降低人们对社会性负性情绪体验的强度。社会功能受损是抑郁症患者或抑郁倾向人群的重要特征之一。该群体对社会排斥的敏感性高, 且对负性社会情绪体验的情绪调节能力降低。在本研究中, 我们采用外显的情绪调节任务, 研究了高、低抑郁水平的两组成年人被试在RVLPFC接受阳性tDCS后其情绪调节能力的改变。结果表明, 虽然采用tDCS激活RVLPFC可帮助被试通过情绪调节(认知重评)减弱负性情绪体验, 但高抑郁水平被试的负性情绪强度下降程度明显小于低抑郁水平被试。另外本文还发现, 与源于个人的负性情绪相比, tDCS效应对源于社会的负性情绪(即社会排斥)更强。本研究是采用电或磁刺激提高抑郁人群社会情绪调节能力的首次尝试。实验结果表明, 高抑郁水平成年人的RVLPFC仅通过单次、短时间(34 min)的tDCS激活, 其情绪调节能力并未得到显著提升。这提示对抑郁倾向群体或抑郁症患者的干预或治疗需要多次施加tDCS。     

经颅直流电刺激技术在物质依赖治疗中的应用

物质依赖是一种慢性、复发性脑部疾病, 给个体及社会带来极大损害。研究发现, 经颅直流电刺激(transcranial direct current stimulation, tDCS)可以通过调节背外侧前额叶(dorsolateral prefrontal cortex, DLPFC)脑区的兴奋性降低物质依赖者的渴求, 并改善受损的认知功能。tDCS具有副作用小、操作简便、费用低廉等优点, 因此在物质依赖治疗领域应用前景广泛。未来应考虑确定最佳的刺激参数及刺激位置, 同时考虑物质依赖者的种类及个体差异, 与其他疗法结合使用, 并进一步深入探索tDCS治疗物质依赖的神经机制。     

Effect of Transcranial Direct Current Stimulation Combined With Virtual Reality Training on Balance in Children With Cerebral Palsy: A Randomized,Controlled, Double-Blind,Clinical Trial

The authors' aim was to investigate the effects of continuous transcranial direct current stimulation (tDCS) combined with virtual reality training on static and functional balance in children with cerebral palsy (CP). Twenty children with CP (6 girls and 14 boys; M age = 7 years 6 months ± 2 years) were randomly allocated to two groups. The experimental group received active tDCS and the control group received sham stimulation during the 10 sessions of virtual reality mobility training protocols. The children were evaluated on 3 occasions (preintervention, postintervention, and 1-month follow-up). Static balance was evaluated using a force plate under 4 conditions: feet on force plate with (a) eyes open and (b) with eyes closed, and feet on foam mat with (c) eyes open and (d) with eyes closed. Functional balance was evaluated using the Pediatric Balance Scale and the Timed Up and Go Test. The analyses demonstrated statistically significant postintervention and follow-up effects favoring the experimental group over the control group with regard to the Pediatric Balance Scale, Timed Up and Go Test, and area of oscillation of the center of pressure when standing on the force plate with eyes open. The present findings suggest that tDCS can potentiate the effects of virtual reality training on static and functional balance among children with CP.