Sham a-tDCS Research Articles

Investigating the effects of aerobic exercise primed anodal transcranial direct current stimulation on γ‐aminobutyric acid concentrations in mild vascular cognitive impairment

AbstractBackgroundMild vascular cognitive impairment (mVCI) is characterized by minor deficits in cognition and memory due to underlying vascular pathology. Anodal transcranial direct current stimulation (atDCS), a non‐invasive neuromodulation technique, has been demonstrated to improve cognition. The effects of atDCS have been suggested to be mediated by γ‐aminobutyric acid (GABA)–a major inhibitory neurotransmitter associated with cerebral perfusion and oxygenation, and cognition and memory. However, previous studies have reported mixed results regarding changes in GABA concentrations following atDCS. Physical activity has been reported to increase cortical GABA levels, and in particular, aerobic exercise (AE) is associated with improved cognition in older adults. Preliminary data from an ongoing trial (EXPRESS‐V) was used to evaluate whether GABA concentration in the motor cortex was altered following AE and/or atDCS and whether this was associated with changes in global cognition in mVCI.MethodIn this double‐blind, randomized clinical trial, participants received one of four interventions for two weeks: AE and atDCS, AE and sham atDCS, exercise education and atDCS, or exercise education and sham atDCS. mVCI was determined based on a modified Gorelick criteria. At baseline and endpoint, GABA concentration in the motor cortex was measured using magnetic resonance spectroscopy and quantified with the Mescher‐Garwood point resolved spectroscopy pulse sequence, and global cognition was assessed using the Montreal Cognitive Assessment. Wilcoxon signed rank test was used to determine changes in GABA concentrations (ΔGABA). Spearman correlation was used to determine the association between ΔGABA and changes in global cognition (ΔMoCA).ResultTen participants have enrolled so far, with nine participants having completed the study (22.2% female, age = 66.4(9.8), years of education = 8.8(3.4), 55.6% White, baseline MoCA score = 22.8(3.1)). To date, ΔGABA was insignificant between baseline and endpoint (Z = 23.0, p = 0.953). However, a positive trend between ΔGABA and ΔMoCA was observed (ρ = 0.650, p = 0.058).ConclusionPreliminary results from nine participants showed a positive trend between ΔGABA and ΔMoCA. Since the trial is ongoing, with the target of recruiting 80 participants by 2024, analyses on unblinded data upon study completion will determine whether AE and atDCS leads to greater ΔGABA, and whether this is accompanied by greater ΔMoCA in mVCI.

Transcranial direct current stimulation over left dorsolateral prefrontal cortex facilitates auditory-motor integration for vocal pitch regulation.

A growing body of literature has implicated the left dorsolateral prefrontal cortex (DLPFC) in the online monitoring of vocal production through auditory feedback. Specifically, disruption of or damage to the left DLPFC leads to exaggerated compensatory vocal responses to altered auditory feedback. It is conceivable that enhancing the cortical excitability of the left DLPFC may produce inhibitory influences on vocal feedback control by reducing vocal compensations. We used anodal transcranial direct current stimulation (a-tDCS) to modulate cortical excitability of the left DLPFC and examined its effects on auditory-motor integration for vocal pitch regulation. Seventeen healthy young adults vocalized vowel sounds while hearing their voice pseudo-randomly pitch-shifted by ±50 or ±200 cents, either during (online) or after (offline) receiving active or sham a-tDCS over the left DLPFC. Active a-tDCS over the left DLPFC led to significantly smaller peak magnitudes and shorter peak times of vocal compensations for pitch perturbations than sham stimulation. In addition, this effect was consistent regardless of the timing of a-tDCS (online or offline stimulation) and the size and direction of the pitch perturbation. These findings provide the first causal evidence that a-tDCS over the left DLPFC can facilitate auditory-motor integration for compensatory adjustment to errors in vocal output. Reduced and accelerated vocal compensations caused by a-tDCS over left DLPFC support the hypothesis of a top-down neural mechanism that exerts inhibitory control over vocal motor behavior through auditory feedback.

A Short-Term Intervention of High-Intensity Exercise and Anodal-tDCS on Motor Learning in Middle-Aged Adults: An RCT.

High-intensity exercise has enhanced motor learning in healthy young adults. Anodal-transcranial direct current stimulation (a-tDCS) may optimize these effects. This study aimed to determine the effects of a short-term high-intensity interval exercise intervention either with or without a-tDCS on the learning and retention of a novel motor task in middle-aged adults. Forty-two healthy middle-aged adults (age = 44.6 ± 6.3, female = 76%) were randomized into three groups: exercise and active a-tDCS, exercise and sham a-tDCS, and a non-exercise and sham a-tDCS control. Participants completed a baseline testing session, followed by three intervention sessions 48-h apart. The exercise groups completed 20-min of high-intensity exercise followed by a novel sequential visual isometric pinch task (SVIPT) while receiving 20-min of 1.5 mA a-tDCS, or sham tDCS. The control group completed 20-min of reading before receiving sham a-tDCS during the SVIPT. Learning was assessed by skill change within and between intervention sessions. Participants returned 5–7 days after the final intervention session and performed the SVIPT task to assess retention. All three groups showed evidence of learning on the SVIPT task. Neither group displayed enhanced overall learning or retention when compared to the control group. High-intensity exercise with or without a-tDCS did not improve learning or retention of a novel motor task in middle-aged adults. The methodological framework provides direction for future research to investigate the potential of differing exercise intensity effects on learning and retention.

Visual cortex cTBS increases mixed percept duration while a-tDCS has no effect on binocular rivalry.

Neuromodulation of the primary visual cortex using anodal transcranial direct current stimulation (a-tDCS) can alter visual perception and enhance neuroplasticity. However, the mechanisms that underpin these effects are currently unknown. When applied to the motor cortex, a-tDCS reduces the concentration of the inhibitory neurotransmitter gamma aminobutyric acid (GABA), an effect that has been linked to increased neuroplasticity. The aim of this study was to assess whether a-tDCS also reduces GABA-mediated inhibition when applied to the human visual cortex. Changes in visual cortex inhibition were measured using the mixed percept duration in binocular rivalry. Binocular rivalry mixed percept duration has recently been advocated as a direct and sensitive measure of visual cortex inhibition whereby GABA agonists decrease mixed percept durations and agonists of the excitatory neurotransmitter acetylcholine (ACH) increase them. Our hypothesis was that visual cortex a-tDCS would increase mixed percept duration by reducing GABA-mediated inhibition and increasing cortical excitation. In addition, we measured the effect of continuous theta-burst transcranial magnetic stimulation (cTBS) of the visual cortex on binocular rivalry dynamics. When applied to the motor or visual cortex, cTBS increases GABA concentration and we therefore hypothesized that visual cortex cTBS would decrease the mixed percept duration. Binocular rivalry dynamics were recorded before and after active and sham a-tDCS (N = 15) or cTBS (N = 15). Contrary to our hypotheses, a-tDCS had no effect, whereas cTBS increased mixed percepts during rivalry. These results suggest that the neurochemical mechanisms of a-tDCS may differ between the motor and visual cortices.

Comparing the effects of multi-session anodal trans-cranial direct current stimulation of primary motor and dorsolateral prefrontal cortices on fatigue and quality of life in patients with multiple sclerosis: a double-blind, randomized, sham-controlled trial

Objective: To compare the effects of anodal trans-cranial direct current stimulation (a-tDCS) over primary motor and dorsolateral prefrontal cortices on Fatigue Severity Scale and its lasting effect on fatigue reduction and improvement in quality of life in patients with multiple sclerosis. Design: A randomized, double-blinded, sham-controlled parallel clinical trial study. Setting: Neurological physiotherapy clinics. Subjects: Thirty-nine participants were randomly assigned to three groups: dorsolateral prefrontal cortex a-tDCS, primary motor a-tDCS (experimental groups) and sham a-tDCS. Finally, 36 participants completed the whole study (n = 12 in each group). Interventions: Participants in the experimental groups received six-session a-tDCS (1.5 mA, 20 minutes) during two weeks (three sessions per week). The sham group received six sessions of 20-minute sham stimulation. Main measures: The Fatigue Severity Scale and quality of life were assessed before, immediately and four weeks after the intervention. Results: Findings indicated a significant reduction in the Fatigue Severity Scale and a significant increase in the quality of life in both experimental groups, immediately after the intervention (P < 0.001), while Fatigue Severity Scale and quality of life changes were not significant in the sham a-tDCS group (P > 0.05). In addition, improvement of the variables remained four weeks after the intervention in dorsolateral prefrontal cortex a-tDCS (mean differences (95% confidence interval): 0.03 (−0.63 to 0.68) as compared to primary motor (−0.62 (−0.11 to −1.14) and sham a-tDCS groups (−0.47 (−1.37 to 0.43)). Conclusion: Both primary motor and dorsolateral prefrontal cortex a-tDCS as compared to sham intervention can immediately improve fatigue and quality of life. However, the effects last up to four weeks only by the dorsolateral prefrontal cortex a-tDCS.

The effects of consecutive sessions of anodal transcranial direct current stimulation over the primary motor cortex on hand function in healthy older adults

BackgroundWith advancing age, changes in the central nervous system may lead to motor functional deficits. Non-invasive brain stimulation techniques are suggested to help modifying brain function. ObjectivesThe aim of the current study was to investigate the effect of using multi session anodal transcranial Direct Current Stimulation (a-tDCS) over the primary motor cortex (M1) on the hand function in healthy older adults. MethodIn this randomized, double-blinded, sham-controlled study 32 participants received active or sham a-tDCS (1 mA, 20 min, for five consecutive days) and performed the Purdue Pegboard Test (PPT) on the first day before tDCS application, immediately (T1), 30 min (T2), and one week after the last session (5th day) (T3) of the stimulation. ResultsThere was a significant improvement for PPT (p < 0.05) in a-tDCS group at all post-test values except for PPT for left hand (PPTL) at T1. Compared to the sham group, the results indicated significant improvement in all PPT subtests (P < 0.05), except for PPTL at T1, PPT for both hands at T2 and PPT assembly at T3 in a-tDCS group. ConclusionThe current findings suggest a-tDCS can be considered as a promising stand-alone technique in the intervention of the age-related decline of manual dexterity for improving hand function.

Does M1 anodal transcranial direct current stimulation affects online and offline motor learning in patients with multiple sclerosis?

Multiple Sclerosis (MS) is one of the most common neurological diseases in the world. Due to structural and functional changes in central nerves system, the patients with MS may affected by sensory-motor learning deficits. The aims of the current study was to assess the effect of primary motor cortex (M1) anodal transcranial direct current stimulation (a-tDCS) on online and offline motor learning in patients with MS. Thirty-nine patients with MS were randomly assigned in three groups: concurrent M1 a-tDCS and serial response time test (SRTT) (n=13), concurrent sham a-tDCS and SRTT (n=13) and SRTT-only control (n=13). The participants in all groups were asked to concurrently perform 20 minutes of SRTT. M1 a-tDCS group received 20-minute M1 a-tDCS (2 mA) concurrent with SRTT, while the a-tDCS was turned off after 30 seconds in the sham a-tDCS group. Response time (RT) and error rate (ER) during SRTT were assessed prior, during and 48 hours after the intervention. Online learning happened in all groups (P < 0.05), with more significant learning in M1 a-tDCS group as compared to the other groups (P < 0.05). However, offline learning was occurred only in M1 a-tDCS group (P < 0.05). The findings indicate offline motor learning impairment in patients with MS. M1 a-tDCS may be used for enhancement of motor learning especially offline learning in patients with MS.

Concurrent postural training and M1 anodal transcranial direct current stimulation improve postural impairment in patients with chronic low back pain

Changes in different regions of the brain due to postural disturbances were found in patients with chronic low back pain (LBP). The aims of the current study were to investigate the short- and long-term enhancing effects of concurrent postural training and primary motor cortex (M1) anodal transcranial direct current stimulation (a-tDCS) on balance, postural stability and pain in chronic LBP patients with postural impairment. In this clinical trial study, thirty eight patients with chronic LBP were randomly assigned to a-tDCS and training, sham a-tDCS and training,and training only groups. All groups received identical postural training for 20 min, three sessions per week for two weeks. The length of stimulation, which used concurrent with postural training in the active a-tDCS group was also 20 min. Before, immediately and one-month after the interventions, postural stability, balance and pain were assessed using Biodex Balance System, Berg Balance Scale (BBS) and Visual Analog Scale (VAS), respectively. The postural stability indices, BBS and VAS scores significantly improved immediately and one-month after the intervention in the a-tDCS and training group (P < 0.001), while there were significant differences between active a-tDCS and other two groups (P < 0.001). Postural stability indices, the BBS and VAS scores were not significantly different between the sham and training only groups after the interventions (P > 0.05). M1 a-tDCS significantly improves the effects of postural training on postural stability, balance and pain in patients with chronic LBP. Two-week postural training alone cannot improve postural impairment in patients with chronic LBP.

Concurrent exergaming and transcranial direct current stimulation to improve balance in people with Parkinson\u2019s disease: study protocol for a randomised controlled trial

BackgroundPeople with Parkinson’s disease (PD) commonly experience postural instability, resulting in poor balance and an increased risk of falls. Exercise-based video gaming (exergaming) is a form of physical training that is delivered through virtual reality technology to facilitate motor learning and is efficacious in improving balance in aged populations. In addition, studies have shown that anodal transcranial direct current stimulation (a-tDCS), when applied to the primary motor cortex, can augment motor learning when combined with physical training. However, no studies have investigated the combined effects of exergaming and tDCS on balance in people with PD.Methods/designTwenty-four people with mild to moderate PD (Hoehn and Yahr scale score 2–4) will be randomly allocated to receive one of three interventions: (1) exergaming + a-tDCS, (2) exergaming + sham a-tDCS or (3) usual care. Participants in each exergaming group will perform two training sessions per week for 12 weeks. Each exergaming session will consist of a series of static and dynamic balance exercises using a rehabilitation-specific software programme (Jintronix) and 20 minutes of either sham or real a-tDCS (2 mA) delivered concurrently. Participants allocated to usual care will be asked to maintain their normal daily physical activities. All outcome measures will be assessed at baseline and at 6 weeks (mid-intervention), 12 weeks (post-intervention) and 24 weeks (3-month follow-up) after baseline. The primary outcome measure will be the Limits of Stability Test. Secondary outcomes will include measures of static balance, leg strength, functional capacity, cognitive task-related cortical activation, corticospinal excitability and inhibition, and cognitive inhibition.DiscussionThis will be the first trial to target balance in people with PD with combined exergaming and a-tDCS. We hypothesise that improvements in balance, functional and neurophysiological outcome measures, and neurocognitive outcome measures will be greater and longer-lasting following concurrent exergaming and a-tDCS than in those receiving sham tDCS or usual care.Trial registrationAustralian New Zealand Clinical Trials Registry, ACTRN12616000594426). Registered on 9 May 2016.

Multi-session anodal tDCS enhances the effects of postural training on balance and postural stability in older adults with high fall risk: Primary motor cortex versus cerebellar stimulation

BackgroundPostural control impairment is a key target for rehabilitation of older adults with high fall risk. ObjectiveTo investigate whether anodal transcranial direct current stimulation (a-tDCS) over primary motor cortex (M1) or cerebellum can enhance the positive effects of postural training on balance and postural stability in older adults with high fall risk. MethodIn this randomised, double-blinded sham-controlled study, 65 participants were randomly assigned into five groups; M1 a-tDCS with postural training, bilateral cerebellar a-tDCS with postural training, sham a-tDCS with postural training, postural training alone and cerebellar a-tDCS alone. Participants in the first two a-tDCS groups received 2 mA stimulation for 20 min concurrently with postural training. Postural training was conducted for three sessions of 20 min per week for two weeks. The Berg Balance Score (BBS) and the stability indices at both static and dynamic levels of the Biodex Balance System were evaluated before and after intervention. A general linear model repeated measure ANOVA was used to assess the effects of variables among groups. ResultSimultaneous postural training with M1 or bilateral cerebellar a-tDCS significantly improved postural stability indices (p < 0.05) and BBS scores (p < 0.05). Besides, the effects of bilateral cerebellar a-tDCS were significantly higher than that of M1 stimulation on these indices (p < 0.05). Moreover, two weeks postural training alone or cerebellar a-tDCS alone is not an adequate intervention to improve the postural stability indices (p > 0.05). ConclusionPostural training with M1 or bilateral cerebellar a-tDCS, especially bilateral cerebellar a-tDCS, can significantly improve postural control or balance in older adults with high fall risk, while two weeks of postural training alone or two weeks cerebellar a-tDCS alone is not a sufficient intervention.

Anodal Transcranial Direct-Current Stimulation to Enhance Rehabilitation in Individuals With Rotator Cuff Tendinopathy: A Triple-Blind Randomized Controlled Trial.

Background Anodal transcranial direct-current stimulation (a-tDCS) has been shown to enhance the effects of sensorimotor training in neurological populations. Sensorimotor training leads to reduced pain and increased function in the treatment of rotator cuff tendinopathy. The addition of a-tDCS during a rehabilitation program centered on sensorimotor training may improve treatment outcomes in individuals with rotator cuff tendinopathy. Objective To compare 2 groups of individuals with rotator cuff tendinopathy, one receiving a rehabilitation program centered on sensorimotor training with a-tDCS and the other receiving the same rehabilitation program with sham a-tDCS. Methods In this triple-blind, parallel-group randomized controlled trial, 40 adults with rotator cuff tendinopathy participated in a 6-week rehabilitation program (8 treatments with home exercises and including sensorimotor training, patient education, and strengthening). They were randomly assigned to 1 of 2 groups to receive either real a-tDCS (stimulation, 1.5 mA for 30 minutes) or sham a-tDCS during the first 5 treatments. Symptoms and functional limitations (Disabilities of the Arm, Shoulder and Hand questionnaire, Western Ontario Rotator Cuff index) of all participants were evaluated at baseline and at 3, 6, and 12 weeks. Acromiohumeral distances (ultrasonographic measurement at 0°, 45°, and 60° of arm elevation) were assessed at baseline and 6 weeks. Two-way or 3-way repeated-measures analyses of variance were used for statistical analyses. Results Both groups showed statistically significant improvement in Disabilities of the Arm, Shoulder and Hand questionnaire and Western Ontario Rotator Cuff index scores at 3, 6, and 12 weeks, and in acromiohumeral distance at 45° and 60° at 6 weeks (P<.05). No significant group-by-time interaction was observed for all outcomes (P>.43). Conclusion Results do not demonstrate any improved treatment outcomes from the addition of a-tDCS during a rehabilitation program for individuals with rotator cuff tendinopathy. Level of Evidence Therapy, level 1b. J Orthop Sports Phys Ther 2018;48(7):541-551. Epub 10 May 2018. doi:10.2519/jospt.2018.7871.

Ipsilateral M1 transcranial direct current stimulation increases excitability of the contralateral M1 during an active motor task: Implications for stroke rehabilitation

Anodal transcranial direct current stimulation (a-tDCS) of the primary motor cortex (M1) elicits an increase in cortical excitability that outlasts the period of stimulation. However, little is known about effects of a-tDCS on the contralateral M1 during and after ipsilateral M1 stimulation. Therefore, we investigated the changes in corticospinal excitability and inhibition of the left M1 during and after 20 min of a-tDCS to the right M1. Eight healthy participants received real (2 mA) and SHAM a-tDCS to the right M1 randomized across 2 testing sessions. Single- and paired-pulse transcranial magnetic stimulation (TMS) was applied to the left M1 to measure changes motor-evoked potential (MEP) amplitude from the right extensor carpi radialis (ECR) at 130% of resting and active motor threshold, cortical silent period (CSP) and short-interval cortical inhibition (SICI). Active motor threshold was measured during a wrist extension contraction that was less than 5% of maximal electromyographic activation of the ECR. TMS measurements were recorded at baseline, every 5 min for 20 min during and 10 min after a-tDCS. The results showed a significant ( P < 0.05) increase in left M1 MEP amplitude and reduction in CSP duration during (10 and 15 min) and after (immediately and 10 min post) a-tDCS to the right M1, only during the active motor task. A significant reduction ( P < 0.05) in SICI during the active task was also found immediately and 10 min post a-tDCS. No significant changes in MEP amplitude, CSP and SICI were observed in the resting or active task during SHAM tDCS. The increase in left M1 MEP amplitude and reduction in CSP and SICI during and after 20 min of right M1 a-tDCS is most likely to be attributed to a reduction in interhemispheric inhibition that is modulated by a-tDCS during the performance of an active task. Our findings may have significant implications for stroke rehabilitation whereby the application of a-tDCS on the contralesional M1 during neurorehabilitation of the paretic limb may be beneficial for inducing neuroplasticity of the ipsilesional M1 to improve motor function.

How does anodal transcranial direct current stimulation of the pain neuromatrix affect brain excitability and pain perception? A randomised, double-blind, sham-control study.

BackgroundIntegration of information between multiple cortical regions of the pain neuromatrix is thought to underpin pain modulation. Although altered processing in the primary motor (M1) and sensory (S1) cortices is implicated in separate studies, the simultaneous changes in and the relationship between these regions are unknown yet. The primary aim was to assess the effects of anodal transcranial direct current stimulation (a-tDCS) over superficial regions of the pain neuromatrix on M1 and S1 excitability. The secondary aim was to investigate how M1 and S1 excitability changes affect sensory (STh) and pain thresholds (PTh).MethodsTwelve healthy participants received 20 min a-tDCS under five different conditions including a-tDCS of M1, a-tDCS of S1, a-tDCS of DLPFC, sham a-tDCS, and no-tDCS. Excitability of dominant M1 and S1 were measured before, immediately, and 30 minutes after intervention respectively. Moreover, STh and PTh to peripheral electrical and mechanical stimulation were evaluated. All outcome measures were assessed at three time-points of measurement by a blind rater.ResultsA-tDCS of M1 and dorsolateral prefrontal cortex (DLPFC) significantly increased brain excitability in M1 (p < 0.05) for at least 30 min. Following application of a-tDCS over the S1, the amplitude of the N20-P25 component of SEPs increased immediately after the stimulation (p < 0.05), whilst M1 stimulation decreased it. Compared to baseline values, significant STh and PTh increase was observed after a-tDCS of all three stimulated areas. Except in M1 stimulation, there was significant PTh difference between a-tDCS and sham tDCS.Conclusiona-tDCS of M1 is the best spots to enhance brain excitability than a-tDCS of S1 and DLPFC. Surprisingly, a-tDCS of M1 and S1 has diverse effects on S1 and M1 excitability. A-tDCS of M1, S1, and DLPFC increased STh and PTh levels. Given the placebo effects of a-tDCS of M1 in pain perception, our results should be interpreted with caution, particularly with respect to the behavioural aspects of pain modulation.Trial RegistrationAustralian New Zealand Clinical Trials, ACTRN12614000817640, http://www.anzctr.org.au/.