Effects of Transcranial Direct Current Stimulation of Primary Motor Cortex on Reaction Time and Tapping Performance: A Comparison Between Athletes and Non-athletes

Anodal M1 tDCS enhances online learning of rhythmic timing videogame skill

Transcranial direct current stimulation (tDCS) has been shown to modify excitability of the primary motor cortex (M1) and influence online motor learning. However, research on the effects of tDCS on motor learning has focused predominantly on simplified motor tasks. The purpose of the present study was to investigate whether anodal stimulation of M1 over a single session of practice influences online learning of a relatively complex rhythmic timing video game. Fifty-eight healthy young adults were randomized to either a-tDCS or SHAM conditions and performed 2 familiarization blocks, a 20-minute 5 block practice period while receiving their assigned stimulation, and a post-test block with their non-dominant hand. To assess performance, a performance index was calculated that incorporated timing accuracy elements and incorrect key inputs. The results showed that M1 a-tDCS enhanced the learning of the video game based skill more than SHAM stimulation during practice, as well as overall learning at the post-test. These results provide evidence that M1 a-tDCS can enhance acquisition of skills where quality or success of performance depends on optimized timing between component motions of the skill, which could have implications for the application of tDCS in many real-world contexts.

Effect of a Neuromodulation Protocol Associated With Sports Training on the Precision Sports Performance of a Wheelchair Basketball Para-Athlete: A Case Study

OBJECTIVE

To investigate whether transcranial direct-current stimulation (tDCS) optimizes the performance of a wheelchair basketball player on precision tasks.

METHODS

A right-handed wheelchair basketball player (1.5 points functional class) with myelomeningocele (low lumbar level) participated in this case study. The tDCS neuromodulation protocol was applied throughout 10 interventions of 20 minutes with a current intensity of 2 mA, simultaneously with sport-specific training, 3 times a week for 4 weeks. Anodic stimulation was performed on the right cerebellar hemisphere (CB2) and cathodic stimulation in the left dorsolateral prefrontal cortex. A control participant was submitted to a sham-tDCS stimulation protocol for the same period. Functional performance was assessed before the intervention and after the 5th and 10th interventions using "pass accuracy," "free-throw shooting," and "spot shot" tests. Outcome measures were compared using percentage differences between preintervention, intermediate intervention, and postintervention values.

RESULTS

There was a gradual increase in the athlete's total and average scores in all tests performed, with an overall improvement of 78% between the baseline and final assessments, while the control participant had an overall improvement of 6.5%.

CONCLUSION

The tDCS protocol was effective in improving performance in precision activities in a wheelchair basketball player.

Anodal transcranial direct current stimulation enhances response inhibition and attention allocation in fencers

Background

The aim of this study is to investigate the acute effects of anodal transcranial direct current stimulation (tDCS) on reaction time, response inhibition and attention in fencers.

Methods

Sixteen professional female fencers were recruited, and subjected to anodal tDCS and sham stimulation in the primary motor area (M1) one week apart in a randomized, crossover, single-blind design. A two-factor analysis of variance with repeated measures was used to analyze the effects of stimulation conditions (anodal stimulation, sham stimulation) and time (pre-stimulation, post-stimulation) on reaction time, response inhibition, and attention in fencers.

Results

The study found a significant improvement in response inhibition and attention allocation from pre-stimulation to post-stimulation following anodal tDCS but not after sham stimulation. There was no statistically significant improvement in reaction time and selective attention.

Conclusions

A single session of anodal tDCS could improve response inhibition, attention allocation in female fencers. This shows that tDCS has potential to improve aspects of an athlete's cognitive performance, although we do not know if such improvements would transfer to improved performance in competition. However, more studies involving all genders, large samples, and different sports groups are needed in the future to further validate the effect of tDCS in improving the cognitive performance of athletes.

Complex sequential learning is not facilitated by transcranial direct current stimulation over DLPFC or M1

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique which was found to have a positive modulatory effect on online sequence acquisition or offline motor consolidation, depending on the relative role of the associated brain region. Primary motor regions (M1) and dorsolateral prefrontal cortices (DLPFC) have both been related to sequential learning. However, research so far did not systematically disentangle their differential roles in online and offline learning especially in more complex sequential paradigms. In this study, the influence of anodal M1 leg area-tDCS and anodal DLPFC-tDCS applied during complex sequential learning (online and offline) was investigated using a complex whole body serial reaction time task (CWB-SRTT) in 42 healthy volunteers. TDCS groups did not differ from sham tDCS group regarding their response and reaction time (online) and also not in terms of overnight consolidation (offline). Sequence specific learning and the number of recalled items also did not differ between groups. Results may be related to unspecific parameters such as timing of the stimulation or current intensity but can also be attributed to the relative role of M1 and DLPFC during early complex learning. Taken together, the current study provides preliminary evidence that M1 leg area or DLPFC modulation by means of tDCS does not improve complex sequential skill learning. SIGNIFICANCE STATEMENT: Understanding motor learning is helpful to deepen our knowledge about the human ability to acquire new skills. Complex sequential learning tasks have only been studied, sparsely, but are particularly mimicking challenges of daily living. The present study studied early motor learning in a complex serial reaction time task while transcranial direct current stimulation (tDCS) was either applied to leg primary motor cortex or bilateral dorsolateral prefrontal cortex. TDCS did not affect sequential learning, neither directly during performance nor in terms of sequence consolidation. Results provide preliminary information that M1 or bilateral DLPFC modulation does not improve early complex motor learning.

Impact of Transcranial Direct Current Stimulation in Pain, Fatigue, and Health Quality of Life of Patients with Idiopathic Inflammatory Myopathies: A Randomized, Double-Blind, Sham-Controlled Crossover Clinical Trial

Objectives

To assess the effectiveness of transcranial direct current stimulation (tDCS) for pain, fatigue, physical function, and health-related quality of life in patients with idiopathic inflammatory myopathy (IIM).

Methods

This randomized, double-blind, sham-controlled, crossover clinical trial enrolled IIM patients with fatigue and pain who received tDCS (20 min, 2 mA) or sham stimulation for 10 daily sessions. Electrodes were placed according to the 10/20 EEG system. Both the groups underwent aerobic exercise training during the intervention period. The patients were evaluated for disease perception, pain, and fatigue using uni-multidimensional questionnaires and physical tests in the periods before and after the first and second interventions and after 12 weeks of follow-up.

Results

After the tDCS intervention, a reduction in the general score of multidimensional pain of 32.0 (1.5-38.0) vs. 0.0 (0.0-13.4) with effect size (ES) of -0.78 was noted, and after sham intervention, a reduction of 26.0 (0.0-37.0) vs. 5.0 (0.0-19.2) with ES of -0.54 (P = 0.047) was also noted. Similar results were evidenced with fatigue (22.5 (15.4-33.2) vs. 5.5 (0.0-14.6) with ES of -0.82) and sham intervention (21.0 (15.8-29.5) vs. 4.0 (4.0-17.5) with ES of -0.80 (P = 0.012)). There were no differences in the domains of the fatigue and pain questionnaires. Adherence was observed in 88.8% of the patients without adverse events.

Conclusion

The association of tDCS with aerobic training promoted additional effects in relation to the group subjected to placebo stimulation on general pain and fatigue scores, as well as on pain intensity, without changes in the subdomains of the pain and fatigue questionnaire. This trial is registered with NCT04678635.

The influence of selected anthropometric parameters on psychomotor abilities among professional Rugby Union players

BACKGROUND

One of the most popular varieties of rugby is Rugby Union, in which a team consists of 15 players. Rugby Union is a full-contact sport, and players must demonstrate strength, endurance, speed and agility. During the match, players participate in multiple physical collisions and tackles, short-duration and high-intensity sprinting efforts. In addition, one of the elements affecting the effectiveness of the player's game can be the reaction time of the rugby player to the visual stimulus and the ability to read the game and react to the situations on the pitch. The level of psychomotor abilities of a person or a player practising sports can be influenced by various factors, including age, body height, body weight, type of sport practised or level of training. The study aimed to analyse the psychomotor abilities of professional rugby union players, investigate the relationship between the selected anthropometric characteristics and psychomotor abilities, and compare obtained results with the control group.

METHODS

The study covered 22 players of the Polish National Team (age: 29.3 ± 5.4) and 27 students in the control group (age: 24.3 ± 3.9). The tests were carried out using the Test2Drive computer system of tests. For psychomotor abilities analysis, four tests were used: Simple Reaction Test, Choice Reaction Time Test, Hand-Eye Coordination Test and Spatial Orientation Test. The statistical analysis compares groups using basic statistical measures, and statistically significant differences between groups were checked. In addition, multiple linear regression was used.

RESULTS

The analysis showed statistically significant differences between the groups in the simple reaction time test and the movement time for the test assessing reaction time with choice and eye-hand coordination. Multiple regression analysis conducted for both groups showed a statistically significant influence of some anthropometric parameters on the examined psychomotor abilities. The calculated multiple regression models had a high fit.

CONCLUSIONS

The analysis showed that professional Rugby Union players have shorter movement time than the control group. For reaction time, statistically significant differences were observed only for simple reaction time. Moreover, linear regression analysis showed that body height and weight affect the selected psychomotor abilities.

Motor Evoked Potential Amplitude in Motor Behavior-based Transcranial Direct Current Stimulation Studies: A Systematic Review

Motor evoked potential amplitude (MEP_amp) is frequently measured in transcranial direct current stimulation (tDCS) studies that target the primary motor cortex (M1), and a subset of these studies involve motor behavior. This systematic review explored the role of MEP_amp as an indicator of neural change in M1-targeted tDCS studies involving motor behavior (i.e., motor practice and/or evaluation of motor performance) in healthy individuals, and examined the association between changes in motor performance and MEP_amp. We executed our search strategy across four bibliographic databases. Twenty-two manuscripts met eligibility criteria. While anodal tDCS combined with motor practice frequently increased MEP_amp, MEP_amp outcomes did not necessarily align with changes in motor performance. Thus, MEP_amp may not be the most appropriate indicator of neural change in tDCS studies that aim to improve motor performance.

A dual-mode neurostimulation approach to enhance athletic performance outcome in experienced taekwondo practitioners

Transcranial Direct Current Stimulation (tDCS) is a growing empirical approach to improve athletic performance. Some recent studies have investigated the effects of transcutaneous spinal direct current stimulation (tsDCS) on the motor performance such as reaction time. TDCS and tsDCS can lead to alteration of the spontaneous neural activity, and the membrane potentials of motor neurons in cerebral cortex and spinal interneurons, respectively. Given the paucity of experimental studies on the non-invasive brain stimulation in the field of sports neuroscience, especially martial sports, the present study aimed at investigating the effects of neurostimulation in potentiating the motor and cognitive functions in experienced taekwondo practitioners. The study sample included 15 experienced male taekwondo players who received real or sham direct current stimulation on the primary motor cortex (M1) and the lumbar spinal segment (T12-L2) over two sessions, 72 h apart. Next, the performance of the participants was evaluated through a simulation of taekwondo exercise directly after the sham and real sessions. Moreover, a cognitive platform (CBS: Cambridge Brain Science) was used to investigate the participants' cognitive profile in each instance. Unlike sham stimulation, real tDCS was associated with improved selective attention and reaction time in both in the simulated task performance and cognitive examination. The concurrent cortical and trans-spinal tDCS was found to improve selective attention (31% performance improvement) (P < 0.0001) [EFFECT SIZE; 1.84]. and reduce reaction time (4.7% performance improvement) (P < 0.0001) [EFFECT SIZE; 0.02]. Meanwhile, the intervention failed to leave a significant change in cognitive functions evaluated through CBS (P > 0.05). As informed by our results, the present dual-mode neurostimulation could improve motor functions potentially through the effect of tsDCS over the spinal interneurons and tDCS over the primary motor cortex. Likewise, our findings suggested an improved performance in simulated taekwondo task after real- but not sham-stimulation. This study paves the way for designing neurostimulation protocols to improve the performance of professional athletes, namely martial art practitioners, including their accuracy and velocity of reactions. Such positive effects of neuostimulation in athletic performance as demonstrated in this research and similar reports are expected to enhance the athletes' success in professional competitions.

From thinking fast to moving fast: motor control of fast limb movements in healthy individuals

The ability to produce high movement speeds is a crucial factor in human motor performance, from the skilled athlete to someone avoiding a fall. Despite this relevance, there remains a lack of both an integrative brain-to-behavior analysis of these movements and applied studies linking the known dependence on open-loop, central control mechanisms of these movements to their real-world implications, whether in the sports, performance arts, or occupational setting. In this review, we cover factors associated with the planning and performance of fast limb movements, from the generation of the motor command in the brain to the observed motor output. At each level (supraspinal, peripheral, and motor output), the influencing factors are presented and the changes brought by training and fatigue are discussed. The existing evidence of more applied studies relevant to practical aspects of human performance is also discussed. Inconsistencies in the existing literature both in the definitions and findings are highlighted, along with suggestions for further studies on the topic of fast limb movement control. The current heterogeneity in what is considered a fast movement and in experimental protocols makes it difficult to compare findings in the existing literature. We identified the role of the cerebellum in movement prediction and of surround inhibition in motor slowing, as well as the effects of fatigue and training on central motor control, as possible avenues for further research, especially in performance-driven populations.

Functional whole-brain mechanisms underlying effects of tDCS on athletic performance of male rowing athletes revealed by resting-state fMRI

Introduction

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that applied to modulate brain activity and enhance motor recovery. However, the neurobiological substrates underlying the effects of tDCS on brain function remain poorly understood. This study aimed to investigate the central mechanisms of tDCS on improving the athletic performance of male rowing athletes.

Methods

Twelve right-handed male professional rowing athletes received tDCS over the left primary motor cortex while undergoing regular training. The resting-state functional magnetic resonance imaging (rs-fMRI) data were acquired before and after tDCS. Measures of amplitude of low-frequency fluctuation (ALFF) and regional homogeneity (ReHo) were calculated and compared between baseline and follow-up, as well as topological measures including global and local efficiency of functional brain networks constructed by graph theoretical analysis.

Results

Male rowing athletes showed increased isokinetic muscle strength of the left knee and left shoulder after tDCS. Increased ALFF values were found in the right precentral gyrus of male rowing athletes after tDCS when compared with those before tDCS. In addition, male rowing athletes showed increased ReHo values in the left paracentral lobule following tDCS. Moreover, increased nodal global efficiency was identified in the left inferior frontal gyrus (opercular part) of male rowing athletes after tDCS.

Conclusion

The findings suggested that simultaneous tDCS-induced excitation over the primary motor cortex might potentially improve the overall athletic performance in male rowing athletes through the right precentral gyrus and left paracentral lobule, as well as left inferior frontal gyrus.

The Relationship Between Reaction Time, Eye-Hand Coordination with Visual Field in Elite Tennis Tennis Players

: The current study investigates the relationship between simple reaction time, choice reaction time, and eye-hand coordination with peripheral vision in elite female table tennis players. Ten female table tennis players of the Iranian national team with a mean age of 19.7 ± 5.964, in the 18th Asian Games of 2018, Jakarta, participated via convenience sampling. The visual field was evaluated with the Humphrey automated perimetry. Choice and simple reaction time were assessed using Deary-Liewald reaction time tester software. In order to measure eye-hand coordination, the manual test of alternate-hand wall toss was used. Data were analyzed in statistical package for the social sciences using Pearson’s correlation. The results show that there was no significant relationship between simple and choice reaction time with peripheral vision in the left and right eyes. Also, results show that there was no significant relationship between eye-hand coordination with peripheral vision in the left and right eyes (P ≤ 0.05). The findings of this study show that experts in an activity visually searched their environment and located essential information more effectively and efficiently than novices. Therefore, we know that this visual feature is more a function of expertise than visual acuity.

Transcranial Direct Current Stimulation of Motor Cortex Enhances Spike Performances of Professional Female Volleyball Players

The purpose of this study was to investigate effects of brain excitability by transcranial direct current stimulation (tDCS) on spike performances of professional female volleyball players. Thirteen professional female volleyball players were recruited for participation. We performed a randomized single-blind, SHAM-stimulus controlled, and counter-balanced crossover design with two interventions in this study. An anodal tDCS current was applied over the primary motor cortex (M1) for 20 min at 2 mA. In the SHAM intervention, the current was first applied for 30 s, after which it was terminated. Exercise performance assessment which comprised spike performance (spike ball speed, spiking consistency), two vertical jumps (jump and reach: JaR, countermovement jump: CMJ), bench-press and back-squat one-repetition maximum (1RM) were tested pre- and post-intervention. Results indicated that spike ball speed and spiking consistency following tDCS were significantly higher than those after SHAM intervention (both p < 0.05). However, JaR and CMJ did not show any significant differences between tDCS and SHAM intervention groups (both p > 0.05). There was no significant difference in bench-press and back-squat 1RM between two groups either (both p > 0.05). These findings suggest that tDCS could be effective in enhancing motor coordination performances of professional female volleyball athletes.

Effect of transcranial direct current stimulation in addition to visuomotor training on choice reaction time and cognition function in amateur soccer players (FAST trial): A randomized control trial

OBJECTIVES

This study aimed to evaluate the effect of anodal transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex (DLPFC) in addition to visuomotor training (VMT) on choice reaction time (CRT) and cognitive function in amateur soccer players.

DESIGN

Single-center, randomized, placebo-controlled, double-blind, parallel-group study.

SETTING

Neuroscience and Motor Control Laboratory.

PARTICIPANTS

Thirty Brazilian male amateur soccer players, aged 18-30 years.

MAIN OUTCOME MEASURES

Participants were allocated to the intervention or control groups. Both groups performed VMT, but the intervention group additionally underwent anodal tDCS over the left dorsolateral prefrontal cortex (DLPFC; F3). The cathodal electrode was positioned in the right supraorbital region (Fp2). The tDCS was applied at 2 mA for 20 min for five consecutive sessions (24 h intervals). The VMT protocol was delivered during the application of tDCS and was composed of kicking a ball for 10 min (between the fifth and fifteenth minutes of the 20 min of tDCS application). The primary outcome was assessed based on changes in CRT during reaching (non-trained limb) and kicking (trained limb) tasks. Secondary outcomes were overall cognitive function measured by the Trail Making Test part A (TMT-A) and part B (TMT-B), and Digit Span Test forward (DSF) and backward (DSB) scores. All outcomes were evaluated before and after the intervention.

RESULTS

In the primary outcomes, compared with the control group, the anodal tDCS combined with VMT group had greater reduction in CRT for the rectus femoris (p = 0.007) adjusted for age and baseline performance (F (1,26) = 22,23; p < 0,001) and for the triceps (p = 0.039) adjusted for training frequency (days/week) and baseline performance (F (1,26) = 5,70; p = 0,016). No differences were observed in the CRT of other muscles (anterior deltoid [p = 0.181], brachial biceps [p = 0.130], and vastus medialis [p = 0.074]). And, there were no differences between the groups in terms of cognitive function (TMT-A [p = 0.062]; TMT-B [p = 0.320]; DSF [p = 0.102]; DSB [p = 0.345]).

CONCLUSION

Anodal tDCS over the left DLPFC in addition to visuomotor training of a functional task can be an efficient tool for athletes to decrease the CRT of the rectus femoris (trained limb) and triceps (non-trained limb); however, there were no differences between the groups in the others muscles (anterior deltoid, brachial biceps, and vastus medialis), and in terms of cognitive function.

Computer-Delivered Cognitive Training and Transcranial Direct Current Stimulation in Patients With HIV-Associated Neurocognitive Disorder: A Randomized Trial

Objective: HIV infection is associated with impaired cognition, and as individuals grow older, they may also experience age-related changes in mental abilities. Previous studies have shown that computer-based cognitive training (CCT) and transcranial direct current stimulation (tDCS) may be useful in improving cognition in older persons. This study evaluated the acceptability of CCT and tDCS to older adults with HIV-associated neurocognitive disorder, and assessed their impact on reaction time, attention, and psychomotor speed. Methods: In a single-blind randomized study, 46 individuals with HIV-associated mild neurocognitive disorder completed neuropsychological assessments and six 20-min training sessions to which they had been randomly assigned to one of the following conditions: (1) CCT with active tDCS; (2) CCT with sham tDCS, or (3) watching educational videos with sham tDCS. Immediately after training and again 1 month later, participants completed follow-up assessments. Outcomes were evaluated via repeated measures mixed effects models. Results: Participant ratings of the intervention were positive. Effects on reaction time were not significant, but measures of attention and psychomotor speed suggested positive effects of the intervention. Conclusion: Both CCT and tDCS were highly acceptable to older persons with HIV infection. CCT and tDCS may improve cognitive in affected individuals. Clinical Trial Registration: [www.ClinicalTrials.gov], identifier [NCT03440840].

Modulation of neural activity in frontopolar cortex drives reward-based motor learning

The frontopolar cortex (FPC) contributes to tracking the reward of alternative choices during decision making, as well as their reliability. Whether this FPC function extends to reward gradients associated with continuous movements during motor learning remains unknown. We used anodal transcranial direct current stimulation (tDCS) over the right FPC to investigate its role in reward-based motor learning. Nineteen healthy human participants practiced novel sequences of finger movements on a digital piano with corresponding auditory feedback. Their aim was to use trialwise reward feedback to discover a hidden performance goal along a continuous dimension: timing. We additionally modulated the contralateral motor cortex (left M1) activity, and included a control sham stimulation. Right FPC-tDCS led to faster learning compared to lM1-tDCS and sham through regulation of motor variability. Bayesian computational modelling revealed that in all stimulation protocols, an increase in the trialwise expectation of reward was followed by greater exploitation, as shown previously. Yet, this association was weaker in lM1-tDCS suggesting a less efficient learning strategy. The effects of frontopolar stimulation were dissociated from those induced by lM1-tDCS and sham, as motor exploration was more sensitive to inferred changes in the reward tendency (volatility). The findings suggest that rFPC-tDCS increases the sensitivity of motor exploration to updates in reward volatility, accelerating reward-based motor learning.

Non-Invasive Brain Stimulation: Augmenting the Training and Performance Potential in Esports Players

During the last two decades, esports, a highly competitive sporting activity, has gained increasing popularity. Both performance and competition in esports require players to have fine motor skills and physical and cognitive abilities in controlling and manipulating digital activities in a virtual environment. While strategies for building and improving skills and abilities are crucial for successful gaming performance, few effective training approaches exist in the fast-growing area of competitive esports. In this paper, we describe a non-invasive brain stimulation (NIBS) approach and highlight the relevance and potential areas for research while being cognizant of various technical, safety, and ethical issues related to NIBS when applied to esports.

Anodal Transcranial Direct Current Stimulation Enhances Retention of Visuomotor Stepping Skills in Healthy Adults

Transcranial direct current stimulation (tDCS) paired with exercise training can enhance learning and retention of hand tasks; however, there have been few investigations of the effects of tDCS on leg skill improvements. The purpose of this study was to investigate whether tDCS paired with visuomotor step training can promote skill learning and retention. We hypothesized that pairing step training with anodal tDCS would improve skill learning and retention, evidenced by decreased step reaction times (RTs), both immediately (online skill gains) and 30 min after training (offline skill gains). Twenty healthy adults were randomly assigned to one of two groups, in which 20-min anodal or sham tDCS was applied to the lower limb motor cortex and paired with visuomotor step training. Step RTs were determined across three time points: (1) before brain stimulation (baseline); (2) immediately after brain stimulation (P0); and (3) 30 min after brain stimulation (P3). A continuous decline in RT was observed in the anodal tDCS group at both P0 and P3, with a significant decrease in RT at P3; whereas there were no improvements in RT at P0 and P3 in the sham group. These findings do not support our hypothesis that anodal tDCS enhances online learning, as RT was not decreased significantly immediately after stimulation. Nevertheless, the results indicate that anodal tDCS enhances offline learning, as RT was significantly decreased 30 min after stimulation, likely because of tDCS-induced neural modulation of cortical and subcortical excitability, synaptic efficacy, and spinal neuronal activity.

Effect of transcranial direct current stimulation on sports performance for two profiles of athletes (power and endurance) (COMPETE): a protocol for a randomised, crossover, double blind, controlled exploratory trial

BACKGROUND

Transcranial direct current stimulation (tDCS) is promising for improving motor and cognitive performance. Nevertheless, its mechanisms of action are unclear and need to be better characterised according to the stimulated brain area and the type of exercise performed.

METHODS/DESIGN

This is a double-blind crossover study, organised into two parts: the first is to assess the effects of tDCS on explosive performance (jump task) and the second is to assess the effects on endurance performance (cycling time trial task). Participants, who are recreationally active or athletes (parkour practitioners, cyclists), will receive two active tDCS sessions (over the left dorsolateral prefrontal cortex and right motor cortex) and one sham tDCS session (part A), or two sequences (one active and one sham) of two daily tDCS sessions over 5 days (part B). Motor and cognitive performance will be compared before and after tDCS sessions (part A), and before and after the first session, after the last session and at day 12 and day 30 of each tDCS sequence (part B).

DISCUSSION

This study investigates the acute and repeated effects of tDCS on the motor and cognitive performance of healthy subjects. It will try to evaluate if tDCS could be considered as a neuroenhancement technology according to the physical task investigated (endurance versus explosive).

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03937115. Registered on 3 May 2019; retrospectively registered.

Anodal transcranial direct current stimulation reduces motor slowing in athletes and non-athletes

Background

Motor fatigability describes a phenomenon that occurs when exhaustive exercise or physically demanding tasks are executed over an extended period of time. Concerning fast repetitive movements, it is noticeable by a reduction in movement speed (motor slowing, MoSlo) and occurs due to both central and peripheral factors. The aim of the present study was to examine the presence of MoSlo during hand- (HTT) and foot-tapping tasks (FTT) comparing trained football (FB) and handball players (HB) and non-athletes (NA). Furthermore, we were interested in how far anodal transcranial direct current stimulation (tDCS) might be capable of modulating MoSlo as compared to sham.

Methods

A total number of 46 participants were enrolled in a sham-controlled, double-blinded, cross-over study. HTT and FTT were performed before, during, after as well as 30 min after 20 min of tDCS over the leg area of the primary motor cortex (M1).

Results

We could demonstrate that MoSlo during HTT and FTT is a general phenomenon that is observed independent of the type of sports and/or training status. Furthermore, we were able to show a tDCS-induced reduction in MoSlo specifically during FTT in both trained athletes and NA. No such effects could be observed for HTT, indicating local specificity of tDCS-induced effects on a behavioral level.

Conclusion

We could demonstrate that tDCS is capable of reducing motor fatigability during fast repetitive movements. These findings are of pivotal interest for many sports where fatigability resistance is a limiting factor in maintaining repetitive movement patterns.

Offline effects of transcranial direct current stimulation on reaction times of lower extremity movements in people after stroke: a pilot cross-over study

BACKGROUND

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that has shown promise for rehabilitation after stroke. Ipsilesional anodal tDCS (a-tDCS) over the motor cortex increases corticospinal excitability, while contralesional cathodal tDCS (c-tDCS) restores interhemispheric balance, both resulting in offline improved reaction times of delayed voluntary upper-extremity movements. We aimed to investigate whether tDCS would also have a beneficial effect on delayed leg motor responses after stroke. In addition, we identified whether variability in tDCS effects was associated with the level of leg motor function.

METHODS

In a cross-over design, 13 people with chronic stroke completed three 15-min sessions of anodal, cathodal and sham stimulation over the primary motor cortex on separate days in an order balanced across participants. Directly after stimulation, participants performed a comprehensive set of lower-extremity tasks involving the paretic tibialis anterior (TA): voluntary ankle-dorsiflexion, gait initiation, and backward balance perturbation. For all tasks, TA onset latencies were determined. In addition, leg motor function was determined by the Fugl-Meyer Assessment - leg score (FMA-L). Repeated measures ANOVA was used to reveal tDCS effects on reaction times. Pearson correlation coefficients were used to establish the relation between tDCS effects and leg motor function.

RESULTS

For all tasks, TA reaction times did not differ across tDCS sessions. For gait initiation and backward balance perturbation, differences between sham and active stimulation (a-tDCS or c-tDCS) did not correlate with leg motor function. Yet, for ankle dorsiflexion, individual reaction time differences between c-tDCS and sham were strongly associated with FMA-L, with more severely impaired patients exhibiting slower paretic reaction times following c-tDCS.

CONCLUSION

We found no evidence for offline tDCS-induced benefits. Interestingly, we found that c-tDCS may have unfavorable effects on voluntary control of the paretic leg in severely impaired patients with chronic stroke. This finding points at potential vicarious control from the unaffected hemisphere to the paretic leg. The absence of tDCS-induced effects on gait and balance, two functionally relevant tasks, shows that such motor behavior is inadequately stimulated by currently used tDCS applications.

TRIAL REGISTRATION

The study is registered in the Netherlands Trial Register (NL5684; April 13th, 2016).

Anodal Transcranial Direct Current Stimulation over the Vertex Enhances Leg Motor Cortex Excitability Bilaterally

In many studies, anodal transcranial Direct Current Stimulation (tDCS) is applied near the vertex to simultaneously facilitate leg motor cortex (M1) of both hemispheres and enhance recovery of gait and balance in neurological disorders. However, its effect on the excitability of leg M1 in either hemisphere is not well known. In this double-blind sham-controlled study, corticospinal excitability changes induced in leg M1 of both hemispheres by anodal (2 mA for 20 minutes) or sham tDCS (for 20 min) over the vertex were evaluated. Peak amplitudes of Transcranial Magnetic Stimulation (TMS) induced motor evoked potentials (MEPs) were measured over the contralateral Tibialis Anterior (TA) muscle before and up to 40 min after tDCS in 11 normal participants. Analysis of data from all participants found significant overall increase in the excitability of leg M1 after tDCS. However, in individual subjects there was variability in observed effects. In 4 participants, 20 min of tDCS increased mean MEPs of TAs on both sides; in 4 participants there was increased mean MEP only on one side and in 3 subjects there was no change. It’s not known if the benefits of tDCS in improving gait and balance are dependent on excitability changes induced in one or both leg M1; such information may be useful to predict treatment outcomes.