Cerebellar Transcranial Direct Current Stimulation Research Articles

Cerebellar Transcranial Direct Current Stimulation in the Cerebellar Cognitive Affective Syndrome: A Randomized, Double-Blind, Sham-Controlled Trial.

The cerebellar cognitive affective syndrome (CCAS) encompasses cognitive and affective symptoms in patients with cerebellar disorders, for which no proven treatment is available. Our primary objective was to study the effect of cerebellar anodal transcranial direct current stimulation (tDCS) on cognitive performance in CCAS patients. Secondary effects on ataxia severity, mood, and quality of life were explored. We performed a randomized, double-blind, sham-controlled trial. Thirty-five patients with CCAS were included and received 10 sessions of 20 minutes sham (n = 17) or real (n = 18) tDCS, with a current of 2 mA. Cognitive performance was assessed using executive function subtests of the computerized Test of Attentional Performance (TAP), with the composite as primary endpoint. Secondary outcomes were ataxia severity, mood, and quality of life. Outcomes were evaluated 1, 3, 6, and 12 months post-intervention. Cerebellar tDCS was well tolerated and no serious adverse events related to the intervention occurred. No significant tDCS effect was found on cognitive performance. Improvement on the TAP was observed in the sham group 1 month post-treatment (estimate = -0.248, 95% CI, -0.49 to -0.01), but not clinically relevant. A positive tDCS effect was observed for ataxia severity 1 month post-treatment (estimate = -0.985, 95% CI, -1.94 to -0.03). Ten sessions of 20 minutes cerebellar anodal tDCS did not prove efficacious for CCAS-related cognitive impairment, but a significant positive effect of tDCS was found for ataxia severity, aligning with previous findings indicative of tDCS as a therapeutic neuromodulation tool in cerebellar disorders. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

The Impact of Bilateral Cerebellar Transcranial Direct Current Stimulation on Balance Control in Healthy Young Adults.

Cerebellar transcranial direct current stimulation (tDCS) has been shown to influence movement functions, but little is known about the specific effects of stimulation polarity on balance control. This study investigated the impact of bilateral cerebellar tDCS on balance functions as a function of stimulation polarity. In this randomized, controlled trial, thirty-nine healthy young adults were assigned to one of three groups: right anodal/left cathodal cerebellar stimulation (AC group), right cathodal/left anodal cerebellar stimulation (CA group), and a control sham group. Each participant underwent a daily 30-minute session of tDCS at 2mA for one week. Balance function was assessed pre- and post-intervention and the data were analyzed using generalized estimating equations. The CA group exhibited a significant reduction in sway area when standing on the left leg and on both stable and unstable surfaces with eyes open, compared to both the AC and sham groups. However, there were no significant differences among the groups in terms of sway length, anteroposterior velocity, or mediolateral velocity. Our results indicate the polarity-dependent effects of bilateral cerebellar tDCS on balance functions, with enhanced stability observed only following cathodal tDCS over the right cerebellum paired with anodal tDCS over the left cerebellum. This polarity-specific modulation may have implications for developing cerebellar neuromodulation interventions for movement disorders.

Differential Effects of Cerebellar Transcranial Direct Current Stimulation with Gait Training on Functional Mobility, Balance, and Ataxia Symptoms.

Cerebellar transcranial direct current stimulation (ctDCS) has emerged as a promising, non-invasive, and safe neuromodulatory intervention capable of reducing ataxia symptoms and restoring cerebellum-motor connectivity. However, previous studies have only applied ctDCS in isolation, without association with specific training. This study aimed to assess the effect of ctDCS combined with gait training on functional mobility, balance, and symptoms and severity of ataxia. A randomized, triple-blind, sham-controlled, bi-center clinical trial was conducted with forty-four adults with cerebellar ataxia. Volunteers were randomized to receive five daily sessions of either real ctDCS (n = 11; 2mA for 25min) or sham ctDCS (n = 11) during gait training. Functional mobility, balance, and symptoms and severity of ataxia were assessed using the Time Up and Go test, the MiniBESTest, and the Scale for the Assessment and Rating of Ataxia (SARA), respectively, before and after the interventions. Both groups showed improvement in functional mobility, but there was no significant difference between the ctDCS and sham groups. However, the ctDCS group demonstrated significant improvements in cerebellar ataxia severity as reflected by SARA scores, particularly in tests of stance, sitting, speech disturbance, nose-finger test, and heel-shin slide test. Notably, no improvements were observed in balance. This study indicates that while ctDCS combined with gait training may improve specific symptoms of cerebellar ataxia, it does not significantly enhance overall functional mobility compared to sham treatment.

Effect of cerebellar transcranial direct current stimulation on postural control and associated neuroplastic alternations in chronic ankle instability

Effect of cerebellar transcranial direct current stimulation on postural control and associated neuroplastic alternations in chronic ankle instability

Integration Analysis of miRNA Circulating Expression Following Cerebellar Transcranial Direct Current Stimulation in Patients with Ischemic Stroke

Integration Analysis of miRNA Circulating Expression Following Cerebellar Transcranial Direct Current Stimulation in Patients with Ischemic Stroke

Effects of cerebellar transcranial direct current stimulation on the excitability of spinal motor neurons and vestibulospinal tract in healthy individuals.

Cerebellar transcranial direct current stimulation (ctDCS) modulates cerebellar cortical excitability in a polarity-dependent manner and affects inhibitory pathways from the cerebellum. The cerebellum modulates spinal reflex excitability via the vestibulospinal tract and other pathways projecting to the spinal motor neurons; however, the effects of ctDCS on the excitability of spinal motor neurons and vestibulospinal tract remain unclear. The experiment involved 13 healthy individuals. ctDCS (sham-ctDCS, anodal-ctDCS, and cathodal-ctDCS) was applied to the cerebellar vermis at 2mA with an interval of at least 3 days between each condition. We measured the maximal M-wave (Mmax) and maximal H-reflex (Hmax) in the right soleus muscle to assess the excitability of spinal motor neurons. We applied galvanic vestibular stimulation (GVS) for 200 ms at 100 ms before tibial nerve stimulation to measure Hmax conditioned by GVS (GVS-Hmax) and calculated the change rate of Hmax by GVS as the excitability of vestibulospinal tract. We measured the Mmax, Hmax, and GVS-Hmax before, during, and after ctDCS in the sitting posture. No main effects of tDCS condition, main effects of time, or interaction effects were observed in Hmax/Mmax or the change rate of Hmax by GVS. It has been suggested that ctDCS does not affect the excitability of spinal motor neurons and vestibulospinal tract, as measured by neurophysiological methods, such as the H-reflex, in healthy individuals in a sitting posture. Effect of ctDCS on other descending pathways to spinal motor neurons, the neurological mechanism of tDCS and the cerebellar activity during the experiment may have contributed to these results. Therefore, we need to investigate the involvement of the cerebellum in Hmax/Mmax and the change rate of Hmax by GVS under different neuromodulation techniques and postural conditions.

Single-Session Cerebellar Transcranial Direct Current Stimulation Improves Postural Stability and Reduces Ataxia Symptoms in Spinocerebellar Ataxia.

Spinocerebellar ataxia (SCA) results in balance and coordination impairment, and current treatments have limited efficacy. Recent evidence suggests that combining postural training with cerebellar transcranial direct current stimulation (ctDCS) can improve these symptoms. However, the combined effects of ctDCS and postural training on individuals with spinocerebellar ataxia remain underexplored. Ten volunteers with (SCA type 3) participated in a triple-blind, randomized, crossover study to receive a single session of ctDCS (2mA for 20min) and a sham ctDCS session separated by at least one week. The Biodex Balance System was used to assess balance at each session, measuring overall stability index, anteroposterior stability index, and medial-lateral stability index. As secondary outcomes, cerebellar ataxia symptoms were evaluated using the 8-item Scale for Assessment and Rating of Ataxia. The assessments were conducted before and after each session. The results indicated that ctDCS enhanced the overall stability index when compared to sham ctDCS (Z = -2.10, p = 0.03), although it did not significantly affect the anteroposterior or medial-lateral stability indices. Compared to the baseline, a single session of ctDCS reduced appendicular symptoms related to cerebellar ataxia, as evidenced by improvements in the nose-finger test (Z = -2.07, p = 0.04), fast alternating hand movements (Z = -2.15, p = 0.03), and heel-to-shin slide (Z = -1.91, p = 0.05). In conclusion, our study suggests that a single session of ctDCS, in combination with postural training, can enhance balance and alleviate ataxia symptoms in individuals with cerebellar ataxia. This study was approved by the local research ethics committee (No. 2.877.813) and registered on clinicaltrials.org (NCT04039048 - https://www.clinicaltrials.gov/study/NCT04039048 ) on 2019-07-28.

The impact of cerebellar transcranial direct current stimulation on isometric bench press performance in trained athletes

Athletic development centers on optimizing performance, including technical skills and fundamental motor abilities such as strength and speed. Parameters such as maximum contraction force and rate of force development, influence athletic success, although performance gains become harder to achieve as athletic abilities increase. Non-invasive transcranial direct current stimulation of the cerebellum (CB-tDCS) has been used successfully to increase force production in novices, although the potential effects in athletes remain unexplored. The present study examined the effects of CB-tDCS on maximum isometric voluntary contraction force (MVCiso) and isometric rate of force development (RFDiso) during a bench press task in well-trained athletes. 21 healthy, male, strength-trained athletes participated in a randomized, sham-controlled, double-blinded crossover design. Each participant completed the isometric bench press (iBP) task on two separate days, with at least 5 days between sessions, while receiving either CB-tDCS or sham stimulation. Electromyography (EMG) recordings of three muscles involved in iBP were acquired bilaterally to uncover differences in neuromuscular activation and agonist-antagonist co-contraction between conditions. Contrary to our hypothesis, no significant differences in MVCiso and RFDiso were observed between CB-tDCS and sham conditions. Furthermore, no tDCS-induced differences in neuromuscular activation or agonist-antagonist co-contraction were revealed. Here, we argue that the effects of CB-tDCS on force production appear to depend on the individual's training status. Future research should study individual differences in tDCS responses between athletes and novices, as well as the potential of high-definition tDCS for precise brain region targeting to potentially enhance motor performance in athletic populations.

Cerebellar tDCS enhances functional communication skills in chronic Aphasia

ABSTRACT Background Transcranial direct current stimulation (tDCS) has emerged as a possible neuromodulatory tool to augment language therapy in post-stroke aphasia. However, there is limited information on whether tDCS may help to improve everyday functional communication. Aims To investigate whether cerebellar tDCS combined with computerized aphasia treatment improves functional communication skills in individuals with chronic aphasia. Methods and Procedures In a randomized, double-blind, sham-controlled, within-subject crossover study, participants received 15 sessions of anodal (n = 14) or cathodal (n = 14) cerebellar tDCS plus computerized aphasia treatment then sham plus computerized aphasia treatment, or the opposite order. Linear mixed-effects regression models were performed to evaluate (1) the effect of tDCS treatment on change in functional communication skills on the two dimensions of the American Speech-Language-Hearing Association Functional Assessment of Communication Skills for Adults (ASHA-FACS): Communication Independence (CI) scale and Qualitative Dimension of Communication (QDC) scale, and (2) the relationship between functional communication skills and trained and untrained naming abilities. Outcomes and Results The results showed significant tDCS-induced gains for the overall QDC mean score, but not for the overall CI mean score. Cerebellar stimulation was more effective than sham for the overall QDC mean score immediately post-treatment, 2-weeks post-treatment and 2-months post-treatment. Follow up analysis separated by group showed that the change in the overall QDC mean score (combining both phases) were similar in participants receiving anodal or cathodal stimulation. We also found a significant linear association between the ASHA-FACS overall CI mean change scores and trained and untrained naming change scores for the tDCS condition but not sham. Conclusions Our study provides preliminary evidence that cerebellar tDCS coupled with computerized aphasia treatment has the potential to improve the overall qualitative dimensions of functional communication skills in individuals with chronic aphasia. Clinical Trial Registration Cerebellar Transcranial Direct Current Stimulation and Aphasia Treatment [NCT02901574]

Excitatory cerebellar transcranial direct current stimulation boosts the leverage of prior knowledge for predicting actions.

The cerebellum causally supports social processing by generating internal models of social events based on statistical learning of behavioral regularities. However, whether the cerebellum is only involved in forming or also in using internal models for the prediction of forthcoming actions is still unclear. We used cerebellar transcranial Direct Current Stimulation (ctDCS) to modulate the performance of healthy adults in using previously learned expectations in an action prediction task. In a first learning phase of this task, participants were exposed to different levels of associations between specific actions and contextual elements, to induce the formation of either strongly or moderately informative expectations. In a following testing phase, which assessed the use of these expectations for predicting ambiguous (i.e. temporally occluded) actions, we delivered ctDCS. Results showed that anodic, compared to sham, ctDCS boosted the prediction of actions embedded in moderately, but not strongly, informative contexts. Since ctDCS was delivered during the testing phase, that is after expectations were established, our findings suggest that the cerebellum is causally involved in using internal models (and not just in generating them). This encourages the exploration of the clinical effects of ctDCS to compensate poor use of predictive internal models for social perception.

Cerebellar Asymmetry of Motivational Direction: Anger-Dependent Effects of Cerebellar Transcranial Direct Current Stimulation on Aggression in Healthy Volunteers.

It has recently been theorized that the frontal asymmetry of approach- and avoidance-related motivation is mirrored in the posterolateral cerebellum. Accordingly, left-to-right dominant cerebellar activity is associated with avoidance-related motivation, whereas right-to-left dominant cerebellar activity is associated with approach-related motivation. The aim of this study was to examine the cerebellar asymmetry of motivational direction in approach-related behavior in the context of aggression. In this randomized double-blind sham-controlled crossover study, thirty healthy right-handed adult volunteers received 2mA active or sham left cathodal-right anodal transcranial direct current stimulation (tDCS) to the cerebellum on two separate occasions while engaging in the Point Subtraction Aggression Paradigm (PSAP) task to measure aggressive behavior. Self-reported state anger was assessed before, halfway and immediately after the task, and heart rate and heart rate variability (HRV) were measured during the task. No main effects of tDCS on aggressive behavior, heart rate and HRV were found. Higher state anger before and during the PSAP task was associated with increased aggressive behavior in the active compared to sham tDCS condition. Aggressive behavior was positively correlated with heart rate during active tDCS, while an inverse association was observed during sham tDCS. Results provide support for the cerebellar asymmetry of motivational direction in approach-related behavior and illustrate the importance of affective state-dependency in tDCS-related effects.

Anodal cerebellar t-DCS impacts skill learning and transfer on a robotic surgery training task

The cerebellum has demonstrated a critical role during adaptation in motor learning. However, the extent to which it can contribute to the skill acquisition of complex real-world tasks remains unclear. One particularly challenging application in terms of motor activities is robotic surgery, which requires surgeons to complete complex multidimensional visuomotor tasks through a remotely operated robot. Given the need for high skill proficiency and the lack of haptic feedback, there is a pressing need for understanding and improving skill development. We investigated the effect of cerebellar transcranial direct current stimulation applied during the execution of a robotic surgery training task. Study participants received either real or sham stimulation while performing a needle driving task in a virtual (simulated) and a real-world (actual surgical robot) setting. We found that cerebellar stimulation significantly improved performance compared to sham stimulation at fast (more demanding) execution speeds in both virtual and real-world training settings. Furthermore, participants that received cerebellar stimulation more effectively transferred the skills they acquired during virtual training to the real world. Our findings underline the potential of non-invasive brain stimulation to enhance skill learning and transfer in real-world relevant tasks and, more broadly, its potential for improving complex motor learning.

Neuronal loss and angiogenesis are suppressed with cerebellar transcranial direct current stimulation in pentyelenetetrazol kindled brain

Neuronal loss and angiogenesis are suppressed with cerebellar transcranial direct current stimulation in pentyelenetetrazol kindled brain

Changes in vestibular-related responses to combined noisy galvanic vestibular stimulation and cerebellar transcranial direct current stimulation.

Vestibular nuclei and cerebellar function comprise vestibular neural networks that control vestibular-related responses. However, the vestibular-related responses to simultaneous stimulation of these regions are unclear. This study aimed to examine whether the combination of noisy galvanic vestibular stimulation (nGVS) and cerebellar transcranial direct current stimulation (ctDCS) using a complex transcranial electrical stimulation device alters vestibular-dominant standing stability and vestibulo-ocular reflex (VOR) function. The center of foot pressure (COP) sway and VOR of participants (28 healthy, young adults) were assessed under four conditions of transcranial electrical stimulation using nGVS and ctDCS. The COP was calculated with the participant standing on a soft-foam surface with eyes closed using a force plate to evaluate body sway. VOR measurements were collected via passive head movements and fixation on a target projected onto the front wall using a video head impulse test (vHIT). VOR gain was calculated in six directions using a semicircular canal structure based on the ratio of eye movement to head movement. The nGVS + ctDCS and nGVS + sham ctDCS conditions decreased COP sway compared to the sham nGVS + ctDCS and sham nGVS + sham ctDCS conditions. No significant differences were observed in the main effect of stimulation or the interaction of stimulation and direction on the vHIT parameters. The results of this study suggest that postural stability may be independently affected by nGVS. Our findings contribute to the basic neurological foundation for the clinical application of neurorehabilitation using transcranial electrical stimulation of the vestibular system.

Changes in cerebellar output abnormally modulate cortical myoclonus sensorimotor hyperexcitability.

Cortical myoclonus is produced by abnormal neuronal discharges within the sensorimotor cortex, as demonstrated by electrophysiology. Our hypothesis is that the loss of cerebellar inhibitory control over the motor cortex, via cerebello-thalamo-cortical connections, could induce the increased sensorimotor cortical excitability that eventually causes cortical myoclonus. To explore this hypothesis, in the present study we applied anodal transcranial direct current stimulation over the cerebellum of patients affected by cortical myoclonus and healthy controls and assessed its effect on sensorimotor cortex excitability. We expected that anodal cerebellar transcranial direct current stimulation would increase the inhibitory cerebellar drive to the motor cortex and therefore reduce the sensorimotor cortex hyperexcitability observed in cortical myoclonus. Ten patients affected by cortical myoclonus of various aetiology and 10 aged-matched healthy control subjects were included in the study. All participants underwent somatosensory evoked potentials, long-latency reflexes and short-interval intracortical inhibition recording at baseline and immediately after 20 min session of cerebellar anodal transcranial direct current stimulation. In patients, myoclonus was recorded by the means of surface EMG before and after the cerebellar stimulation. Anodal cerebellar transcranial direct current stimulation did not change the above variables in healthy controls, while it significantly increased the amplitude of somatosensory evoked potential cortical components, long-latency reflexes and decreased short-interval intracortical inhibition in patients; alongside, a trend towards worsening of the myoclonus after the cerebellar stimulation was observed. Interestingly, when dividing patients in those with and without giant somatosensory evoked potentials, the increment of the somatosensory evoked potential cortical components was observed mainly in those with giant potentials. Our data showed that anodal cerebellar transcranial direct current stimulation facilitates-and does not inhibit-sensorimotor cortex excitability in cortical myoclonus syndromes. This paradoxical response might be due to an abnormal homeostatic plasticity within the sensorimotor cortex, driven by dysfunctional cerebello-thalamo-cortical input to the motor cortex. We suggest that the cerebellum is implicated in the pathophysiology of cortical myoclonus and that these results could open the way to new forms of treatment or treatment targets.

Cerebellar Transcranial Direct Current Stimulation Applied over Multiple Days Does Not Enhance Motor Learning of a Complex Overhand Throwing Task in Young Adults.

Cerebellar transcranial direct current stimulation (tDCS) enhances motor skill and learning in relatively simple motor tasks, but it is unclear if c-tDCS can improve motor performance in complex motor tasks. The purpose of this study was to determine the influence of c-tDCS applied over multiple days on motor learning in a complex overhand throwing task. In a double-blind, randomized, between-subjects, SHAM-controlled, experimental design, 30 young adults were assigned to either a c-tDCS or a SHAM group. Participants completed three identical experiments on consecutive days that involved overhand throwing in a pre-test block, five practice blocks with concurrent c-tDCS, and a post-test block. Overhand throwing endpoint accuracy was quantified as the endpoint error. The first dorsal interosseous muscle motor evoked potential (MEP) amplitude elicited by transcranial magnetic stimulation was used to quantify primary motor cortex (M1) excitability modulations via c-tDCS. Endpoint error significantly decreased over the 3 days of practice, but the magnitude of decrease was not significantly different between the c-tDCS and SHAM group. Similarly, MEP amplitude slightly increased from the pre-tests to the post-tests, but these increases did not differ between groups. These results indicate that multi-day c-tDCS does not improve motor learning in an overhand throwing task or increase M1 excitability.

A Single Application of Cerebellar Transcranial Direct Current Stimulation Fails to Enhance Motor Skill Acquisition in Parkinson's Disease: A Pilot Study.

Parkinson's disease (PD) is a progressive neurodegenerative disorder that leads to numerous impairments in motor function that compromise the ability to perform activities of daily living. Practical and effective adjunct therapies are needed to complement current treatment approaches in PD. Transcranial direct current stimulation applied to the cerebellum (c-tDCS) can increase motor skill in young and older adults. Because the cerebellum is involved in PD pathology, c-tDCS application during motor practice could potentially enhance motor skill in PD. The primary purpose was to examine the influence of c-tDCS on motor skill acquisition in a complex, visuomotor isometric precision grip task (PGT) in PD in the OFF-medication state. The secondary purpose was to determine the influence of c-tDCS on transfer of motor skill in PD. The study utilized a double-blind, SHAM-controlled, within-subjects design. A total of 16 participants completed a c-tDCS condition and a SHAM condition in two experimental sessions separated by a 7-day washout period. Each session involved practice of the PGT concurrent with either c-tDCS or SHAM. Additionally, motor transfer tasks were quantified before and after the practice and stimulation period. The force error in the PGT was not significantly different between the c-tDCS and SHAM conditions. Similarly, transfer task performance was not significantly different between the c-tDCS and SHAM conditions. These findings indicate that a single session of c-tDCS does not elicit acute improvements in motor skill acquisition or transfer in hand and arm tasks in PD while participants are off medications.

Comparison of Two Therapeutic Approaches of Cerebellar Transcranial Direct Current Stimulation in a Sardinian Family Affected by Spinocerebellar Ataxia 38: a Clinical and Computerized 3D Gait Analysis Study.

Spinocerebellar ataxia 38 (SCA 38) is a very rare autosomal dominant inherited disorder caused by a mutation in ELOV5 gene, specifically expressed in cerebellar Purkinje cells, encoding an enzyme involved in the synthesis of fatty acids. Seven symptomatic SCA 38 patients of a Sardinian family were administered 15 sessions of cerebellar anodal transcranial direct current stimulation (tDCS) in a cross-over study, employing deltoid cerebellar-only (C-tDCS) and cerebello-spinal (CS-tDCS) cathodal montage. Clinical evaluation was performed at baseline (T0), after 15 sessions of tDCS (T1) and after 1 month of follow-up (T2). Modified International Cooperative Ataxia Rating Scale (MICARS) and the Robertson dysarthria profile were used to rate ataxic and dysarthric symptoms, respectively. Alertness and split attention tests from Zimmermann test battery for attentional performance were employed to rate attentive functions. Moreover, 3D computerized gait analysis was employed to obtain a quantitative measure of efficacy of tDCS on motor symptoms. While clinical data showed that both CS and C-tDCS improved motor, dysarthric, and cognitive scores, the quantitative analysis of gait revealed significant improvement in spatio-temporal parameters only for C-tDCS treatment. Present findings, yet preliminary and limited by the small size of the tested sample, confirm the therapeutic potential of cerebellar tDCS in improving motor and cognitive symptoms in spinocerebellar ataxias and underline the need to obtain quantitative and objective measures to monitor the efficacy of a therapeutic treatment and to design tailored rehabilitative interventions. ClinicalTrials.gov identifier: NCT05951010.

Acute Effect of Single-Session Cerebellar Anodal Transcranial Direct Current Stimulation on Static and Dynamic Balance in Healthy Volunteers.

Several studies have shown the positive effect of cerebellar transcranial direct current stimulation (ctDCS) on balance in patients and older adults. However, in healthy volunteers, the results are conflicting. We aimed to investigate the immediate effect of anodal ctDCS on the dynamic-static balance in healthy, non-athletic young adults due to the possible benefits for sports performance. Twenty-one healthy volunteers participated in two consecutive 20 min sessions of ctDCS (2 mA current intensity), with 1-week intervals (anodal ctDCS-sham ctDCS). Flamingo and Y-Balance tests were used to evaluate the static and dynamic balances before and after the ctDCS. A Continuous Performance Test (CPT) was used to evaluate the changes in sustained attention, impulsivity, and vigilance. A repeated measure analysis of variance (ANOVA) was used to compare the changes in balance scores, reaction time, omission, and commission numbers. There were no statistically significant differences in dynamic and static balance scores and in CPT parameters between conditions. In conclusion, there was no immediate neuromodulation effect of anodal ctDCS to improve balance performance in healthy, young individuals. Furthermore, no evidence was found to support the use of cerebellar tDCS to improve sports performance.

Interindividual differences in posterior fossa morphometry affect cerebellar tDCS-induced electric field strength

ObjectiveClinical, behavioural, and neurophysiological effects of cerebellar transcranial direct current stimulation (tDCS) are highly variable and difficult to predict. We aimed to examine associations between cerebellar tDCS-induced electric field strength, morphometric posterior fossa parameters, and skin-cerebellum distance. As a secondary objective, field characteristics were compared between cephalic and extracephalic electrode configurations. MethodsElectric field simulations of midline cerebellar tDCS (7 × 5 cm electrodes, current intensities of 2 mA) were performed on MRI-based head models from 37 healthy adults using buccinator, frontopolar, and lower neck reference electrodes. Average field strengths were determined in eight regions of interest (ROIs) covering the anterior and posterior vermis and cerebellar hemispheres. Besides skin-cerebellum distance, various angles were measured between posterior fossa structures. Multivariable linear regression models were used to identify predictors of field strength in different ROIs. ResultsSkin-cerebellum distance and “pons angle” were independently associated with field strength in the anterior and posterior vermis. “Cerebellar angle” and skin-cerebellum distance affected field strength in anterior and posterior regions of the right cerebellar hemisphere. Field strengths in all examined cerebellar areas were highest in the frontopolar and lowest in the lower neck montage, while the opposite was found for field focality. The lower neck montage induced considerably less spreading toward anterior cerebellar regions compared with the buccinator and frontopolar montages, which resulted in a more evenly distributed field within the cerebellum. ConclusionIn addition to skin-cerebellum distance, interindividual differences in posterior fossa morphometry, specifically pons and cerebellar angle, explain part of the variability in cerebellar tDCS-induced electric field strength. Furthermore, when targeting the midline cerebellum with tDCS, an extracephalic reference electrode is associated with lower field strengths and higher field focality than cephalic montages. SignificanceThis study identifies two novel subject-specific anatomical factors that partly determine cerebellar tDCS-induced electric field strength and reveals differences in field characteristics between electrode montages.