Transcranial direct current stimulation over somatosensory cortex decreases experimentally induced acute pain perception

OBJECTIVE: Multiple cortical areas including the primary somatosensory cortex are known to be involved in nociception. The aim of this study was to investigate the effect of transcranial direct current stimulation (tDCS) that modulates the cortical excitability painlessly and noninvasively, over somatosensory cortex on acute pain perception induced with a Tm:YAG laser. METHODS: Subjective pain rating scores and amplitude changes of the N1, N2, and P2 components of laser-evoked potentials of 10 healthy participants were analyzed before and after anodal, cathodal, and sham tDCS. RESULTS: Our results demonstrate that cathodal tDCS significantly diminished pain perception and the amplitude of the N2 component when the contralateral hand to the side of tDCS was laser-stimulated, whereas anodal and sham stimulation conditions had no significant effect. DISCUSSION: Our study highlights the antinociceptive effect of this technique and may contribute to the understanding of the mechanisms underlying pain relief. The pharmacologic prolongation of the excitability-diminishing after-effects would render the method applicable to different patient populations with chronic pain.     

Transcranial direct current stimulation for promoting motor function in cerebral palsy: a review

Transcranial direct current stimulation (tDCS) has the potential to improve motor function in a range of neurological conditions, including Cerebral Palsy (CP). Although there have been many studies assessing tDCS in adult stroke, the literature regarding the efficacy of tDCS in CP is more limited. This review therefore focuses on the neurophysiological and clinical findings in children and adolescents with CP. Initial studies applying anodal tDCS to promote lower limb function are promising, with improvements in gait, mobility and balance reported. However, the results of upper limb studies are mixed and more research is needed. Studies investigating neurophysiological changes or predictors of response are also lacking. Large-scale longitudinal studies are needed for the lower limb to ascertain whether the initial pilot results translate into clinically meaningful improvements. Future studies of the upper limb should focus on determining the optimal stimulation parameters and consider tailoring stimulation to the individual based on the (re)organisation of their motor system.     

Time course and spatial distribution of fMRI signal changes during single-pulse transcranial magnetic stimulation to the primary motor cortex

Simultaneous transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) may advance the understanding of neurophysiological mechanisms of TMS. However, it remains unclear if TMS induces fMRI signal changes consistent with the standard hemodynamic response function (HRF) in both local and remote regions. To address this issue, we delivered single-pulse TMS to the left M1 during simultaneous recoding of electromyography and time-resolved fMRI in 36 healthy participants. First, we examined the time-course of fMRI signals during supra- and subthreshold single-pulse TMS in comparison with those during voluntary right hand movement and electrical stimulation to the right median nerve (MNS). All conditions yielded comparable time-courses of fMRI signals, showing that HRF would generally provide reasonable estimates for TMS-evoked activity in the motor areas. However, a clear undershoot following the signal peak was observed only during subthreshold TMS in the left M1, suggesting a small but meaningful difference between the locally and remotely TMS-evoked activities. Second, we compared the spatial distribution of activity across the conditions. Suprathreshold TMS-evoked activity overlapped not only with voluntary movement-related activity but also partially with MNS-induced activity, yielding overlapped areas of activity around the stimulated M1. The present study has provided the first experimental evidence that motor area activity during suprathreshold TMS likely includes activity for processing of muscle afferents. A method should be developed to control the effects of muscle afferents for fair interpretation of TMS-induced motor area activity during suprathreshold TMS to M1.     

Transcranial direct current stimulation: electrode montage in stroke

Neurophysiological and computer modelling studies have shown that electrode montage is a critical parameter to determine the neuromodulatory effects of transcranial direct current stimulation (tDCS). We tested these results clinically by systematically investigating optimal tDCS electrode montage in stroke. Ten patients received in a counterbalanced and randomised order the following conditions of stimulation (i) anodal stimulation of affected M1 (primary motor cortex) and cathodal stimulation of unaffected M1 ('bilateral tDCS'); (ii) anodal stimulation of affected M1 and cathodal stimulation of contralateral supraorbital area ('anodal tDCS'); (iii) cathodal stimulation of unaffected M1 and anodal stimulation of contralateral supraorbital area ('cathodal tDCS'); (iv) anodal stimulation of affected M1 and cathodal stimulation of contralateral deltoid muscle ('extra-cephalic tDCS') and (v) sham stimulation. We used the Jebsen-Taylor Test (JTT) as a widely accepted measure of upper limb function. Bilateral tDCS, anodal tDCS and cathodal tDCS were shown to be associated with significant improvements on the JTT. Placing the reference electrode in an extracephalic position and use of sham stimulation did not induce any significant effects. This small sham controlled cross-over clinical trial is important to provide additional data on the clinical effects of tDCS in stroke and for planning and designing future large tDCS trials in patients with stroke.     

Transcranial direct current stimulation: electrode montage in stroke

Neurophysiological and computer modelling studies have shown that electrode montage is a critical parameter to determine the neuromodulatory effects of transcranial direct current stimulation (tDCS). We tested these results clinically by systematically investigating optimal tDCS electrode montage in stroke. Ten patients received in a counterbalanced and randomised order the following conditions of stimulation (i) anodal stimulation of affected M1 (primary motor cortex) and cathodal stimulation of unaffected M1 (‘bilateral tDCS’); (ii) anodal stimulation of affected M1 and cathodal stimulation of contralateral supraorbital area (‘anodal tDCS’); (iii) cathodal stimulation of unaffected M1 and anodal stimulation of contralateral supraorbital area (‘cathodal tDCS’); (iv) anodal stimulation of affected M1 and cathodal stimulation of contralateral deltoid muscle (‘extra-cephalic tDCS’) and (v) sham stimulation. We used the Jebsen–Taylor Test (JTT) as a widely accepted measure of upper limb function. Bilateral tDCS, anodal tDCS and cathodal tDCS were shown to be associated with significant improvements on the JTT. Placing the reference electrode in an extracephalic position and use of sham stimulation did not induce any significant effects. This small sham controlled cross-over clinical trial is important to provide additional data on the clinical effects of tDCS in stroke and for planning and designing future large tDCS trials in patients with stroke.     

Transcranial direct current stimulation reveals inhibitory deficiency in migraine

The issue of interictal excitability of cortical neurons in migraine patients is controversial: some studies have reported hypo-, others hyperexcitability. The aim of the present study was to observe the dynamics of this basic interictal state by further modulating the excitability level of the visual cortex using transcranial direct current stimulation (tDCS) in migraineurs with and without aura. In healthy subjects anodal tDCS decreases, cathodal stimulation increases transcranial magnetic stimulation (TMS)-elicited phosphene thresholds (PT), which is suggested as a representative value of visual cortex excitability. Compared with healthy controls, migraine patients tended to show lower baseline PT values, but this decrease failed to reach statistical significance. Anodal stimulation decreased phosphene threshold in migraineurs similarly to controls, having a larger effect in migraineurs with aura. Cathodal stimulation had no significant effect in the patient groups. This result strengthens the notion of deficient inhibitory processes in the cortex of migraineurs, which is selectively revealed by activity-modulating cortical input.     

Patient-conducted anodal transcranial direct current stimulation of the motor cortex alleviates pain in trigeminal neuralgia

Background

Transcranial direct current stimulation (tDCS) of the primary motor cortex has been shown to modulate pain and trigeminal nociceptive processing.

Methods

Ten patients with classical trigeminal neuralgia (TN) were stimulated daily for 20 minutes over two weeks using anodal (1 mA) or sham tDCS over the primary motor cortex (M1) in a randomized double-blind cross-over design. Primary outcome variable was pain intensity on a verbal rating scale (VRS 0–10). VRS and attack frequency were assessed for one month before, during and after tDCS. The impact on trigeminal pain processing was assessed with pain-related evoked potentials (PREP) and the nociceptive blink reflex (nBR) following electrical stimulation on both sides of the forehead before and after tDCS.

Results

Anodal tDCS reduced pain intensity significantly after two weeks of treatment. The attack frequency reduction was not significant. PREP showed an increased N2 latency and decreased peak-to-peak amplitude after anodal tDCS. No severe adverse events were reported.

Conclusion

Anodal tDCS over two weeks ameliorates intensity of pain in TN. It may become a valuable treatment option for patients unresponsive to conventional treatment.     

Transcranial direct current stimulation: a computer-based human model study

OBJECTIVES: Interest in transcranial direct current stimulation (tDCS) in clinical practice has been growing, however, the knowledge about its efficacy and mechanisms of action remains limited. This paper presents a realistic magnetic resonance imaging (MRI)-derived finite element model of currents applied to the human brain during tDCS. EXPERIMENTAL DESIGN: Current density distributions were analyzed in a healthy human head model with varied electrode montages. For each configuration, we calculated the cortical current density distributions. Analogous studies were completed for three pathological models of cortical infarcts. PRINCIPAL OBSERVATIONS: The current density magnitude maxima injected in the cortex by 1 mA tDCS ranged from 0.77 to 2.00 mA/cm(2). The pathological models revealed that cortical strokes, relative to the non-pathological solutions, can elevate current density maxima and alter their location. CONCLUSIONS: These results may guide optimized tDCS for application in normal subjects and patients with focal brain lesions.     

Transcranial cortex stimulation and fMRI: electrophysiological correlates of dual-pulse BOLD signal modulation

Are the local hemodynamic changes in BOLD-fMRI correlated to increased or decreased neuronal activity or both? We combined transcranial electrical cortex stimulation (TES) with simultaneous fMRI and electromyographic (EMG) recording to study the influence of inhibitory and excitatory neuronal activity on the concomitant BOLD signal change. Unilateral or bilateral TES was applied with a postero-anterior orientation. This activates pyramidal cells transsynaptically and allows for the induction of cortical inhibition and excitation of the pyramidal cell, respectively. In this project interhemispheric inhibition (IHI) served as an in vivo model to investigate electrophysiologically well defined inhibitory and excitatory effects. METHODOLOGY: Included event-related fMRI, which triggered TES; online recording of the EMG response monitored the inhibitory and excitatory influences on discharging corticospinal neurons. RESULTS: Revealed that a single suprathreshold stimulus induced a positive BOLD response both in the ipsilateral as well as in the contralateral primary motor cortex (M1). The contralateral co-activation of the homotopic M1 should be a functional correlate of transcallosal connections. If a contralateral conditioning stimulus preceded the test stimulus by 10 ms (IHI), the subsequent ipsilateral BOLD signal was significantly reduced. We find that cortical inhibitory processes are accompanied by attenuation of the local neurovascular signal.     

Modulation of mu rhythm desynchronization during motor imagery by transcranial direct current stimulation

Background  

The mu event-related desynchronization (ERD) is supposed to reflect motor preparation and appear during motor imagery. The aim of this study is to examine the modulation of ERD with transcranial direct current stimulation (tDCS).     

经颅直流电刺激治疗卒中后注意障碍的临床研究

目的:研究经颅直流电刺激(tDCS)对脑卒中后注意障碍患者的注意功能影响及可能的机制。方法:选取2021年10月～2022年6月在徐州市中心医院康复科进行治疗的60例卒中后注意障碍患者,随机分为观察组与对照组各30例。2组患者均进行常规认知康复训练,观察组在此基础上予以tDCS刺激,每周5次,每次20min,共4周;对照组参照观察组,但仅在初始和最后30s内施加电流,余同观察组。采用数字广度测试(DST)和字母删除试验分别对患者注意广度和持久度进行评估,采用符号数字模式测试(SDMT)对患者注意转移能力进行评估,采用蒙特利尔认知评估量表(MoCA)及改良Barthel指数(MBI)分别对患者认知功能及日常生活能力进行评估。并评估2组患者事件相关电位P300潜伏期和波幅的改善情况。结果:治疗4周后,2组患者MoCA、MBI、SDMT、DST评分、字母正确删除数、P300和波幅均增加(均P<0.05),P300潜伏期缩短(P<0.05);观察组MoCA、MBI、SDMT、DST评分、字母正确删除数、P300波幅均高于对照组(均P<0.05),P300潜伏期短于对照组(P&...     

Transcranial direct current stimulation in post-stroke aphasia rehabilitation: A systematic review

Background

Transcranial direct current stimulation (tDCS) is a non-invasive tool that induces neuromodulation in the brain. Several studies have shown the effectiveness of tDCS in improving language recovery in post-stroke aphasia. However, this innovative technique is not currently used in routine speech and language therapy (SLT) practice.

Investigation of fMRI neurofeedback of differential primary motor cortex activity using kinesthetic motor imagery

Functional MRI neurofeedback (fMRI NF) is an emerging technique that trains subjects to regulate their brain activity while they manipulate sensory stimulus representations of fMRI signals in "real-time". Here we report an fMRI NF study of brain activity associated with kinesthetic motor imagery (kMI), analyzed using partial least squares (PLS), a multivariate analysis technique. Thirteen healthy young adult subjects performed kMI involving each hand separately, with NF training targeting regions of interest (ROIs) in the left and right primary motor cortex (M1). Throughout, subjects attempted to maximize a laterality index (LI) of brain activity-the difference in activity between the contralateral ROI (relative to the hand involved in kMI) and the ipsilateral M1 ROI-while receiving real-time updates on a visual display. Six of 13 subjects were successful in increasing the LI value, whereas the other 7 were not successful and performed similarly to 5 control subjects who received sham NF training. Ability to suppress activity in the ipsilateral M1 ROI was the primary driver of successful NF performance. Multiple PLS analyses depicted activated networks of brain regions involved with imagery, self-awareness, and feedback processing, and additionally showed that activation of the task positive network was correlated with task performance. These results indicate that fMRI NF of kMI is capable of modulating brain activity in primary motor regions in a subset of the population. In the future, such methods may be useful in the development of NF training methods for enhancing motor rehabilitation following stroke.     

左背外侧前额叶阳极经颅直流电刺激对脑卒中后抑郁症的疗效观察

目的:观察左背外侧前额叶阳极经颅直流电刺激对脑卒中后抑郁症的疗效。方法:将40例脑卒中患者随机分成治疗组与对照组各20例,观察治疗4周。治疗组在常规康复治疗的基础上在第1周及第2周每日增加阳极经颅直流电刺激左背外侧前额叶治疗,对照组只进行常规的康复治疗训练。在经颅直流电刺激介入前及第1周、第2周、第4周后分别应用汉密尔顿抑郁量表(HAMD)、汉密尔顿焦虑量表(HAMA)、改良Barthel指数(MBI)、工具性日常生活能力量表(IADL)评定患者心理及日常生活能力改善效果。结果:治疗组患者经颅直流电刺激(t DCS)治疗1周、2周后的HAMA、HAMD评分均明显低于对照组,而且差异具有显著性意义(P0.05);且在刺激结束2周后的随访对比中明显要优于对照组。结论:阳极经颅直流电刺激左背外侧前额叶对脑卒中后抑郁症可减轻或消除脑卒中患者的抑郁或者焦虑情绪,提高患者的日常生存质量。     

经颅直流电刺激改善维持性血液透析患者注意力和执行力的临床观察

目的：探索经颅直流电刺激（transcranial direct current stimulation,tDCS）改善维持性血液透析（maintenance hemodialysis,MHD）患者注意力和执行力,降低跌倒风险的作用。方法：本研究招募MHD患者36例,采用随机数字表法将患者随机分为对照组（n=18）和治疗组（n=18）。治疗组患者在每次透析期间使用tDCS治疗20min,每周3次,共2周的治疗,对照组进行假刺激。两组患者在治疗前后均采用蒙特利尔认知评估量表（Montreal Cognitive Assessment,MoCA）评估认知功能,使用无线APDM运动监测惯性传感器系统采集步态时空参数（步速、步幅、转弯时间、转弯角度及转弯峰值角速度）观察行为学的变化。结果：治疗前两组患者各项测试得分均无显著差异（P>0.05）。治疗后治疗组患者的MoCA总分显著提高（P<0.05）,其中MoCA量表的视空间与执行力、注意力、定向得分显著升高（P<0.05）。治疗组转弯角度和转弯峰值角速度的差值较对照组显著提高（P<0.05）。多元线性逐步回归分析结果表明...     

Modulating inhibitory control with direct current stimulation of the superior medial frontal cortex

The executive control of voluntary action involves not only choosing from a range of possible actions but also the inhibition of responses as circumstances demand. Recent studies have demonstrated that many clinical populations, such as people with attention-deficit hyperactivity disorder, exhibit difficulties in inhibitory control. One prefrontal area that has been particularly associated with inhibitory control is the pre-supplementary motor area (Pre-SMA). Here we applied non-invasive transcranial direct current stimulation (tDCS) over Pre-SMA to test its role in this behavior. tDCS allows for current to be applied in two directions to selectively excite or suppress the neural activity of Pre-SMA. Our results showed that anodal tDCS improved efficiency of inhibitory control. Conversely, cathodal tDCS showed a tendency towards impaired inhibitory control. To our knowledge, this is the first demonstration of non-invasive intervention tDCS altering subjects' inhibitory control. These results further our understanding of the neural bases of inhibitory control and suggest a possible therapeutic intervention method for clinical populations.     

Transcranial direct current stimulation in the recovery of postural control after stroke: a pilot study

Abstract

Purpose: This pilot study aimed to evaluate the effectiveness of multiple sessions of transcranial Direct Current Stimulation (tDCS) during 4 weeks on balance and gait parameters after stroke. Method: Thirty-one stroke patients were included in this randomised, double-blind, sham-controlled crossover study. The Tinetti test was used to assess functional balance and gait after stroke. Secondary measures, Rivermead Motor Assessment (RMA) and Trunk Impairment Scale (TIS), were registered to asses both motricity and trunk performance. All tests were administered at baseline, after 4 and 8 weeks. Patients were randomly divided into two groups. Both groups received both sixteen 20-min sessions of tDCS and sixteen 20-min sessions of Sham stimulation. Application method between groups was changed after 4 weeks. A general linear repeated measures model was used to analyse the results of our study. Results: Results revealed an effect on the total score of the Tinetti test (p?=?0.049). No significant results were obtained for the RMA (p?=?0.166) and the TIS (p?=?0.479). Conclusions: This pilot study indicates that 16 tDCS-sessions could have a beneficial effect on balance and gait in stroke patients measured with the Tinetti test. However, further research is needed to elucidate these findings.

• Implications for Rehabilitation

• Sixteen sessions of tDCS is beneficial in the recovery of postural control in stroke patients.

• tDCS has to be applied as soon as possible to enhance beneficial effects.