Dual-hemisphere transcranial direct current stimulation improves performance in a tactile spatial discrimination task

ObjectiveThe aim of this study was to test the hypothesis that dual-hemisphere transcranial direct current stimulation (tDCS) over the primary somatosensory cortex (S1) could improve performance in a tactile spatial discriminative task, compared with uni-hemisphere or sham tDCS.MethodsNine healthy adults participated in this double-blind, sham-controlled, and cross-over design study. The performance in a grating orientation task (GOT) in the right index finger was evaluated before, during, immediately after and 30 min after the dual-hemisphere, uni-hemisphere (1 mA, 20 min), or sham tDCS (1 mA, 30 s) over S1. In the dual-hemisphere and sham conditions, anodal tDCS was applied over the left S1, and cathodal tDCS was applied over the right S1. In the uni-hemisphere condition, anodal tDCS was applied over the left S1, and cathodal tDCS was applied over the contralateral supraorbital front.ResultsThe percentage of correct responses on the GOT during dual-hemisphere tDCS was significantly higher than that in the uni-hemisphere or sham tDCS conditions when the grating width was set to 0.75 mm (all p < 0.05).ConclusionsDual-hemisphere tDCS over S1 improved performance in a tactile spatial discrimination task in healthy volunteers.SignificanceDual-hemisphere tDCS may be a useful strategy to improve sensory function in patients with sensory dysfunctions.     

Anodal transcranial direct current stimulation (tDCS) over supplementary motor area (SMA) but not pre-SMA promotes short-term visuomotor learning

BackgroundNon-invasive brain stimulation such as transcranial direct current stimulation (tDCS) has been shown to modulate cortical excitability and thereby influencing motor behaviour and learning.HypothesisWhile there is increasing knowledge about the importance of the primary motor cortex (M1) in short- and long-term motor skill learning, little is known about the role of secondary motor areas such as the supplementary and pre-supplementary motor area (SMA/pre-SMA) especially in short-term motor performance. Since SMA but not pre-SMA is directly connected to M1, we hypothesize that anodal tDCS over SMA but not pre-SMA will facilitate visuomotor learning.MethodsWe applied anodal tDCS (tDCS_anodal) over left SMA, pre-SMA or M1 (n = 12 in each group) while subjects performed a visuomotor pinch force task (VPFT) with their right hand and compared VPFT performance relative to sham (tDCS_sham).ResultsFor the first time, we could show that apart from tDCS_anodal over left M1 also SMA but not pre-SMA stimulation promotes short-term improvements in visuomotor learning relative to tDCS_sham.ConclusionsOur findings provide novel evidence about the role of SMA in short-term visuomotor performance. This knowledge might be beneficial in developing hypothesis-driven clinical studies in neurorehabilitation.     

Interactions between transcranial direct current stimulation (tDCS) and pharmacological interventions in the Major Depressive Episode: Findings from a naturalistic study

BackgroundTranscranial direct current stimulation (tDCS) is a non-invasive, neuromodulatory technique with an emerging role for treating major depression.ObjectiveTo investigate the interactions between tDCS and drug therapy in unipolar and bipolar depressed patients who were refractory for at least one pharmacological treatment.MethodsThis was a naturalistic study using data from 54 female and 28 male patients (mean age of 54 years) that consecutively visited our psychiatric unit. They received active tDCS (five consecutive days, 2 mA, anodal stimulation over the left and cathodal over the right dorsolateral prefrontal cortex, twice a day, 20 minutes). The outcome variable (mood) was evaluated using the Beck Depression Inventory (BDI) and the Hamilton Depression Rating Scale (HDRS). Predictor variables were age, gender, disorder and pharmacological treatment (seven dummy variables). We performed univariate and multivariate analyses as to identify predictors associated to the outcome.ResultsAfter 5 days of treatment, BDI and HDRS scores decreased significantly (29% ± 36%, 18% ± 9%, respectively, P < 0.01 for both). Benzodiazepine use was independently associated with a worse outcome in both univariate (β = 4.92, P < 0.01) and multivariate (β = 5.8, P < 0.01) analyses; whereas use of dual-reuptake inhibitors positively changed tDCS effects in the multivariate model (β = –4.7, P = 0.02). A similar trend was observed for tricyclics (β = –4, P = 0.06) but not for antipsychotics, non-benzodiazepine anticonvulsants and other drugs.ConclusiontDCS over the DLPFC acutely improved depressive symptoms. Besides the inherent limitations of our naturalistic design, our results suggest that tDCS effects might vary according to prior pharmacological treatment, notably benzodiazepines and some antidepressant classes. This issue should be further explored in controlled studies.     

Modulating oscillatory brain activity correlates of behavioral inhibition using transcranial direct current stimulation

ObjectiveStudies have mainly documented behavioral changes induced by transcranial direct current stimulation (tDCS), but recently cortical modulations of tDCS have also been investigated. Our previous work revealed behavioral inhibition modulation by anodal tDCS over the right inferior frontal gyrus (rIFG); however, the electrophysiological correlates underlying this stimulation montage have yet to be established. The current work aimed to evaluate the distribution of neuronal oscillations changes following anodal tDCS over rIFG coupled with cathodal tDCS over left orbitofrontal cortex (lOFC) using spectral power analysis.MethodsHealthy subjects underwent sham and real tDCS (15 min, 1.5 mA, anodal rIFG; cathodal lOFC) stimulation conditions in a single-blind, placebo-controlled cross-over trial. Following tDCS session, resting EEG recordings were collected during 15 min.ResultsAnalysis showed a significant and selective diminution of the power of theta band. The theta diminution was observed in the rIFG area (represented the anode electrode), and was not found in the lOFC area (represented the cathode electrode). A significant effect was observed only in the theta but not in other bands.ConclusionsThese results are the first demonstration of modulating oscillatory activity as measured by EEG with tDCS over rIFG in general, and documenting theta band reduction with this montage in particular.SignificanceOur results may explain the improvement in behavioral inhibition reported in our previous work, and although this study was conducted with healthy subjects, the findings suggest that tDCS may also modulate electrophysiological changes among ADHD patients, where decreasing theta activity is the target of neuro-feedback methods aimed to improve cognitive control.     

Transcranial direct current stimulation (tDCS) in the treatment of depression: Systematic review and meta-analysis of efficacy and tolerability

BackgroundTranscranial direct current stimulation (tDCS) is a potential alternative treatment option for major depressive episodes (MDE).ObjectivesWe address the efficacy and safety of tDCS in MDE.MethodsThe outcome measures were Hedges’ g for continuous depression ratings, and categorical response and remission rates.ResultsA random effects model indicated that tDCS was superior to sham tDCS (k = 11, N = 393, g = 0.30, 95% CI = [0.04, 0.57], p = 0.027). Adjunctive antidepressant medication and cognitive control training negatively impacted on the treatment effect. The pooled log odds ratios (LOR) for response and remission were positive, but statistically non-significant (response: k = 9, LOR = 0.36, 95% CI[−0.16, 0.88], p = 0.176, remission: k = 9, LOR = 0.25, 95% CI [−0.42, 0.91], p = 0.468). We estimated that for a study to detect the pooled continuous effect (g = 0.30) at 80% power (alpha = 0.05), a total N of at least 346 would be required (with the total N required to detect the upper and lower bound being 49 and 12,693, respectively).ConclusionstDCS may be efficacious for treatment of MDE. The data do not support the use of tDCS in treatment-resistant depression, or as an add-on augmentation treatment. Larger studies over longer treatment periods are needed.     

The effect of transcranial direct current stimulation on motor sequence learning and upper limb function after stroke

Objective

To assess the impact of electrode arrangement on the efficacy of tDCS in stroke survivors and determine whether changes in transcallosal inhibition (TCI) underlie improvements.

Comparison of blinding effectiveness between sham tDCS and placebo sertraline in a 6-week major depression randomized clinical trial

ObjectiveTo compare blinding integrity and associated factors for transcranial direct current stimulation (tDCS) vs. placebo-pill, the gold standard blinding method.MethodsParallel trial. Depressed participants were randomized to verum/placebo sertraline and active/sham tDCS (2 mA, 30-min 10-daily sessions and two additional, fortnight sessions) over 6 weeks. Blinding was assessed in completers (n = 102) and in a random subgroup (n = 35) of raters and participants, in which we also inquired to qualitatively describe their strongest guessing reason.ResultsParticipants and raters presented similar performance for predicting treatment assignment at endpoint, correctly guessing tDCS and sertraline beyond chance. Nevertheless, clinical response was associated with correct prediction and tDCS non-responders failed to predict the allocation group. For tDCS, “trouble concentrating” was inversely associated with correct prediction. “Skin redness” was more reported for active-tDCS, but did not predict the allocation group. The qualitative reasons for raters’ guessing were not associated with correct prediction, whereas for participants clinical response and adverse effects were directly and inversely associated with correct prediction, respectively.ConclusionBlinding integrity of tDCS and sertraline were comparable and mainly associated with efficacy rather than blinding failure.SignificanceTDCS blinding can be improved by adopting parallel designs and avoiding subjects’ awareness of skin redness.     

Relationships between sleep disturbances and gastroesophageal reflux disease in Asian sleep clinic referrals

ObjectiveStudies on the association between gastroesophageal reflux disease (GERD) and sleep apnea syndrome (SAS) have reported conflicting results, and attention has not been paid to the relationship between GERD and other sleep disorders. The aim of the study was to evaluate the relationship between GERD and various aspects of sleep disturbances.MethodsA total of 564 subjects who were referred to a sleep laboratory were enrolled in the study. They underwent nocturnal polysomnography (NPSG), and they were asked to complete a GERD questionnaire. The questionnaire consisted of 14 items, and included questions on seven reflux symptoms, namely, heartburn, acid regurgitation, chest pain, hoarseness, globus sensation, coughing and epigastric soreness. Subjects reporting heartburn or acid regurgitation at least once a week were classified as having GERD.ResultsAmong 564 participants, 51 subjects (9.0%) were diagnosed as having GERD. GERD patients had higher scores in Beck depression inventory (p < .01), Epworth sleepiness scale (p = .03), Pittsburg sleep quality index (p < .01), more spontaneous arousals in NPSG, and more alcohol consumption than non-GERD patients. There was no association between presence of GERD, SAS-related variables, and body mass index (BMI). GERD was significantly associated with poor sleep quality (adjusted OR, 3.5; 95% CI, 1.3–9.3) and depressed mood (adjusted OR, 2.8; 95% CI, 1.5–5.3).ConclusionPoor subjective sleep and depressive symptoms are associated with the presence of GERD with no association between SAS, BMI and GERD. In managing patients with GERD, psychiatric and sleep symptoms need to be evaluated and appropriately treated.     

Modulation of spinal neuronal excitability by spinal direct currents and locomotion after spinal cord injury

ObjectiveSpinal neuronal function is impaired after a severe spinal cord injury (SCI) and can be assessed by the analysis of spinal reflex (SR) behavior. We applied transcutaneous spinal direct current stimulation (tsDCS) and locomotor activity, to determine whether the excitability of spinal neuronal circuitries underlying locomotion can be modulated after motor complete SCI.MethodSRs were evoked by non-noxious electrical stimulation of the tibial nerve. SR behavior was assessed before, immediately after, and 20 min after four different interventions (anodal, cathodal, sham tsDCS, or locomotion) in subjects with motor complete SCI and healthy subjects.ResultsSR amplitudes in SCI subjects were increased after anodal tsDCS by 84% (p < 0.05). Cathodal, sham tsDCS and locomotion had no influence on SR amplitudes. In addition, reflex threshold was lower after anodal tsDCS and locomotion in SCI subjects (p < 0.05).ConclusionAnodal tsDCS is able to modulate spinal neuronal circuitries after SCI.SignificanceThis novel, noninvasive approach might be used as a tool to excite spinal neuronal circuitries. If applied repetitively within a training approach, anodal tsDCS might prevent adverse alterations in spinal reflex function in severely affected SCI subjects, i.e., a manifestation of a spinal neuronal dysfunction taking part below the level of a spinal lesion.     

The Adjunct of Electric Neurostimulation to Rehabilitation Approaches in Upper Limb Stroke Rehabilitation: A Systematic Review With Network Meta-Analysis of Randomized Controlled Trials

ObjectiveThis review analyzed the current evidence and the potential for the application of electric neurostimulation such as transcranial direct current stimulation (tDCS) and vagus nerve stimulation (VNS) in upper limb stroke rehabilitation.Materials and MethodsWe performed a systematic review of randomized controlled trials (RCTs) using network meta-analysis (NMA), searching the following data bases: PubMed, Web of Science, Cochrane, and Google Scholar, using specific keywords, from January 2010 to April 2021, and assessing the effects of “tDCS” or “VNS” combined with other therapies on upper limb motor function and activities of daily living (ADL) after stroke.ResultsWe included 38 RCTs with 1261 participants. Pairwise NMA showed transcutaneous VNS (tVNS) and anodal tDCS were effective in improving upper limb motor function (tVNS: mean difference [MD]: 5.50; 95% CI [0.67–11.67]; p < 0.05; anodal tDCS: MD: 5.23; 95% CI [2.45–8.01]; p < 0.05). tVNS and tDCS (anodal and cathodal) were also effective in improving ADL performance after stroke (tVNS: standard MD [SMD]: 0.96; 95% CI [0.15–2.06]; p < 0.05; anodal tDCS: SMD: 3.78; 95% CI [0.0–7.56]; p < 0.05; cathodal tDCS: SMD: 5.38; 95% CI [0.22–10.54]; p < 0.05). Surface under the cumulative ranking curve analysis revealed that tVNS is the best ranked treatment in improving upper limb motor function and performance in ADL after stroke. There was no difference in safety between VNS and its control interventions, measured by reported adverse events (VNS: risk ratio = 1.02 [95% CI = 0.48–2.17; I² = 0; p = 0.96]).ConclusionModerate- to high-quality evidence suggests that tVNS and anodal tDCS were effective in improving upper limb motor function in both acute/subacute and chronic stroke. In addition to tVNS and anodal tDCS, cathodal tDCS is also effective in improving ADL performance after stroke.     

Effect of a 10-day trigeminal nerve stimulation (TNS) protocol for treating major depressive disorder: A phase II,sham-controlled,randomized clinical trial

BackgroundConsidering both the burden determined by major depressive disorder (MDD) itself and the high refractoriness and recurrence index, alternative strategies, such as trigeminal nerve stimulation (TNS), are the cutting edge instruments to optimize clinical response and to avoid treatment discontinuation and relapse of symptoms. Trigeminal nerve stimulation is an incipient simple, low-cost interventional strategy based on the application of an electric current over a branch of the trigeminal nerve with further propagation of the stimuli towards brain areas related to mood symptoms.MethodThe study was a phase II, randomized, sham-controlled trial with 40 patients with MDD. Patients with moderate or severe depressive symptoms as assessed by adequate clinical scales underwent a 10-day intervention protocol. Regarding main clinical outcome, analysis of variance (ANOVA) was performed to evaluate mean change scores in depressive symptoms as assessed by the HDRS-17 between baseline (t1), after intervention protocol (t2), and during one-month follow-up (t3).ResultsThere was a significant interaction between the mean percentage changes in depressive symptoms according to the HDRS in the two groups across the three assessments (F = 6.38, df = 2, p = 0.0033). Post hoc analyses (Bonferroni method) demonstrated a statistically significant difference between depressive symptoms at baseline and t1 (p = 0.01) and between depressive symptoms at baseline and t2 (p = 0.009). No severe adverse effects were reported.DiscussionOur results in the present controlled trial highlight the possibility of more practical treatment protocols for clinical research, which are similar to those for different neuromodulation strategies such as transcranial direct current stimulation (tDCS). The in-office administration of TNS in our protocol is similar to the schedule for repetitive transcranial magnetic stimulation (rTMS), though over fewer treatment sessions.ConclusionFurther controlled studies will contribute to the establishment of the clinical relevance of this new treatment strategy for MDD.     

Safety limits of cathodal transcranial direct current stimulation in rats

ObjectiveThe aim of this rat study was to investigate the safety limits of extended transcranial direct current stimulation (tDCS). tDCS may be of therapeutic value in several neuro-psychiatric disorders. For its clinical applicability, however, more stable effects are required, which may be induced by intensified stimulations.MethodsFifty-eight rats received single cathodal stimulations at 1–1000 μA for up to 270 min through an epicranial electrode (3.5 mm²). Histological evaluation (H&E) was performed 48 h later. A threshold estimate was calculated from volumes of DC-induced lesions.ResultsBrain lesions occurred at a current density of 142.9 A/m² for durations greater than 10 min. For current densities between 142.9 and 285.7 A/m², lesion size increased linearly with charge density; with a calculated zero lesion size intercept of 52400 C/m². Brains stimulated below either this current density or charge density threshold, including stimulations over 5 consecutive days, were morphologically intact.ConclusionThe experimentally determined threshold estimate is two orders of magnitude higher than the charge density currently applied in humans (171–480 C/m²). In relation to transcranial DC stimulation in humans the rat epicranial electrode montage may provide for an additional safety margin.SignificanceAlthough these results cannot be directly transferred to humans, they encourage the development intensified tDCS protocols. Further animal studies are required, before such protocols can be applied in humans.     

Methods for extra-low voltage transcranial direct current stimulation: Current and time dependent impedance decreases

ObjectiveThough tDCS is well tolerated, it is desirable to further limit the voltage applied for additional safety factors and optimized device design. We investigated the minimum voltage required for tDCS using 1.5 and 2.5 mA.MethodsImpedance data has been collected prior to, during and after 18 tDCS sessions, using 1.5 mA and 2.5 mA tDCS currents and three different test current magnitudes. Data was pooled and tested for differences using t-tests, corrected for multiple comparisons. Average impedance data was fitted into a RLC circuit model with additional double integrator.ResultsWe report that the impedance drop during tDCS initiation significantly reduces the voltage compliance required to achieve the target current (14.5 V for 1.5 mA, 18.5 V for 2.5 mA). Data was well approximated by a 4th order linear impedance model.ConclusionIn addition to indicating the feasibility of reduced voltage tDCS, we propose an extra-low voltage “Limited Total Energy” approach where stimulation is continued at voltage compliance allowing time for impedance to decrease and target current to be reached.SignificanceReduced-voltage and Limited Total Energy tDCS are viable approaches towards more protective and robust tDCS protocols.     

Influence of transcutaneous spinal stimulation on human LTP-like pain amplification. A randomized,double-blind study in volunteers

ObjectiveTranscutaneous spinal direct current stimulation (tsDCS) has been proven to affect nociceptive signal processing. We designed a randomized, double-blind, cross-over study to investigate whether tsDCS applied before or after inducing long-term potentiation-(LTP)-like hyperalgesia may decrease nociceptive sensitivity.MethodsIn healthy volunteers, tsDCS (2.5 mA, 15 min) was applied to the thoracic spine prior (n = 14) or immediately following (n = 12) electrical high-frequency stimulation (HFS) to the thigh, inducing hyperalgesia. Mechanical and electrical perception were assessed before HFS stimulation and at three time points following HFS stimulation (all within 90 min of HFS). Subjects took part in three separate sessions to test effects of anodal, cathodal, or sham tsDCS.ResultsWithin 60 min HFS led to unilateral changes on the conditioned side: mechanical pain thresholds tended to decrease and electrical detection thresholds significantly decreased (p < 0.001); pain ratings measured using the numerical rating scale (NRS) increased for electrical stimuli (p < 0.01) and two categories of mechanical stimuli (“Light(8–64 mN)”: p = ns; “Heavy(128–512 mN)”: p < 0.01). Irrespective of stimulation order or polarity, tsDCS could not influence nociceptive sensitivity.ConclusionHyperalgesia was adequately induced, but tsDCS had no effect on HFS-induced sensitization.SignificanceWhile tsDCS has been shown to affect pain measures, our results suggest irrespective of time of stimulation or polarity that tsDCS may be less effective in modulating pain in a sensitized state in healthy subjects.     

Adjunctive high-frequency right prefrontal repetitive transcranial magnetic stimulation (rTMS) was not effective in obsessive–compulsive disorder but improved secondary depression

BackgroundThere is preliminary evidence that repetitive transcranial magnetic stimulation (rTMS) may be useful in obsessive–compulsive disorder (OCD) patients.MethodsOur objective was to examine efficacy of adjunctive right prefrontal high-frequency (rapid) rTMS treatment in OCD patients. 42 patients with OCD were randomly assigned to 10 sessions of add-on high-frequency right prefrontal active rTMS (10 Hz, 110% of motor threshold, 4 s per train, 20 trains per session) or sham stimulation. They were rated on Yale Brown Obsessive Compulsive Scale (YBOCS), Hamilton Rating Scale for Depression (HAM-D), Hamilton Rating Scale for Anxiety (HAM-A) and Clinical Global Impression-Severity of Illness (CGI-S) at baseline, day 14 and day 28. The dose of antiobsessive drug was kept constant throughout the period of assessment.ResultsFor YBOCS scores, repeated measures ANOVA showed significant main effect of treatment, but no effect of treatment over time (Pillai's Trace F = 1.39, p = .262). However, significant effect of treatment over time as shown by interaction effect for both HAM-D (Pillai's Trace F = 3.67, p = .035, η² = .158) and HAM-A scores (Pillai's Trace F = 5.22, p = .01, η² = .211) were seen.ConclusionAdjunctive high-frequency right prefrontal rTMS does not have any significant effect in the treatment of OCD. However, it is modestly effective in the treatment of comorbid depressive symptoms in patients with OCD.     

Blink reflex in patients with postparalytic facial syndrome and blepharospasm: Trigeminal and auditory stimulation

ObjectiveThe enhancement of blink reflex (BR) excitability was shown in patients with postparalytic facial syndrome (PFS) and essential blepharospasm (EB). We prospectively investigated patients with PFS and EB whether BR alterations demonstrated by trigeminal stimulation will similarly be observed upon auditory stimulation.MethodsFifteen patients with PFS, 15 patients with EB, and 30 healthy volunteers were involved. Electrically stimulated trigeminal BR and auditory BR were studied bilaterally.ResultsThe mean R2 amplitude and duration values were highest in EB patients, being significantly higher than PFS patients (p < 0.05) and control group (p < 0.01). The mean R2 duration in PFS patients were also significantly longer in compared to control group (p = 0.025). EB patients showed a higher mean R (auditory) amplitude and duration than PFS patients (p < 0.05) and controls (p < 0.04). The mean R (auditory) duration was longer on symptomatic side of PFS patients in compared to controls (p = 0.05).ConclusionsWe observed that there is an enhanced excitability of BR circuit in postparalytic facial syndrome and essential blepharospasm, which could be evoked by auditory stimulation in addition to trigeminal stimulation.SignificanceThe enhanced excitability in patients with EB and PFS probably originates from the final common pathway of BR circuit, namely facial motor or premotor neurons.     

Revisiting interhemispheric imbalance in chronic stroke: A tDCS study

Objective

Chronic stroke patients with moderate-severe motor impairment may have an increased reliance on contralesional vs ipsilesional motor areas to control the paretic arm. We hypothesised that increasing contralesional excitability with anodal transcranial direct current stimulation (a-tDCS) would benefit motor performance in patients with moderate-severe impairment.

Does anodal transcranial direct current stimulation modulate sensory perception and pain? A meta-analysis study

ObjectiveThe primary aim of this systematic review was to evaluate the effects of anodal transcranial direct current stimulation (a-tDCS) on sensory (STh) and pain thresholds (PTh) in healthy individuals and pain levels (PL) in patients with chronic pain.MethodsElectronic databases were searched for a-tDCS studies. Methodological quality was examined using the PEDro and Downs and Black (D&B) assessment tools.Resultsa-tDCS of the primary motor cortex (M1) increases both STh (P < 0.005, with the effect size of 22.19%) and PTh (P < 0.001, effect size of 19.28%). In addition, STh was increased by a-tDCS of the primary sensory cortex (S1) (P < 0.05 with an effect size of 4.34). Likewise, PL decreased significantly in the patient group following application of a-tDCS to both the M1 and dorsolateral prefrontal cortex (DLPFC). The average decrease in visual analogue score was 14.9% and 19.3% after applying a-tDCS on the M1 and DLPFC. Moreover, meta-analysis showed that in all subgroups (except a-tDCS of S1) active a-tDCS and sham stimulation produced significant differences.ConclusionsThis review provides evidence for the effectiveness of a-tDCS in increasing STh/PTh in healthy group and decreasing PL in patients. However, due to small sample sizes in the included studies, our results should be interpreted cautiously. Given the level of blinding did not considered in inclusion criteria, the result of current study should be interpreted with caution.SignificanceSite of stimulation should have a differential effect over pain relief.     

Daily training with realistic visual feedback improves reproducibility of event-related desynchronisation following hand motor imagery

ObjectiveFew brain–computer interface (BCI) studies have addressed learning mechanisms by exposure to visual feedback that elicits scalp electroencephalogram. We examined the effect of realistic visual feedback of hand movement associated with sensorimotor rhythm.MethodsThirty-two healthy participants performed in five daily training in which they were shown motor imagery of their dominant hand. Participants were randomly assigned to 1 of 4 experimental groups receiving different types of visual feedback on event-related desynchronisation (ERD) derived over the contralateral sensorimotor cortex: no feedback as a control, bar feedback with changing bar length, anatomically incongruent feedback in which the hand open/grasp picture on screen was animated at eye level, and anatomically congruent feedback in which the same hand open/grasp picture was animated on the screen overlaying the participant’s hand.ResultsDaily training with all types of visual feedback induced more robust ERD than the no feedback condition (p < 0.05). The anatomically congruent feedback produced the highest reproducibility of ERD with the smallest inter-trial variance (p < 0.05).ConclusionRealistic feedback training is a suitable method to acquire the skill to control a BCI system.SignificanceThis finding highlights the possibility of improvement of reproducibility of ERD and can help to use BCI techniques.     

Functional repetitive transcranial magnetic stimulation increases motor cortex excitability in survivors of stroke

ObjectiveTo determine if repetitive transcranial magnetic stimulation (rTMS) applied to the motor cortex with simultaneous voluntary muscle activation, termed functional-rTMS, will promote greater neuronal excitability changes and neural plasticity than passive-rTMS in survivors of stroke.MethodsEighteen stroke survivors were randomized into functional-rTMS (EMG-triggered rTMS) or passive-rTMS (rTMS only; control) conditions. Measures of short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF), force steadiness (coefficient of variation, CV) at 10% of maximum voluntary contraction, and pinch task muscle activity were assessed before and after rTMS. Functional-rTMS required subjects to exceed a muscle activation threshold to trigger each rTMS train; the passive-rTMS group received rTMS while relaxed.ResultsSignificant interactions (time × condition) were observed in abductor pollicis brevis (APB) SICI, APB ICF, CV of force, and APB muscle activity. Functional-rTMS decreased APB SICI (p < 0.05) and increased ICF (p < 0.05) after stimulation, whereas passive-rTMS decreased APB muscle activity (p < 0.01) and decreased CV of force (p < 0.05). No changes were observed in FDI measures (EMG, ICF, SICI).Conclusion(s)Functional-rTMS increased motor cortex excitability, i.e., less SICI and more ICF for the APB muscle. Passive stimulation significantly reduced APB muscle activity and improved steadiness.SignificanceFunctional-rTMS promoted greater excitability changes and selectively modulated agonist muscle activity.