Anodal tDCS Research Articles

Visual long-term memory is not made more precise with medial-frontal direct-current stimulation

ABSTRACT Previous research suggests that applying anodal transcranial direct-current stimulation (tDCS) to the medial-frontal cortex can improve how quickly subjects learn to make simple discriminations (i.e., red from blue). Here, we tested the idea that this enhanced task learning is attributable to superior encoding of relevant information into visual long-term memory. Thirty subjects completed an anodal stimulation session and a sham session, with order counterbalanced across subjects, before performing recognition-memory tasks using pictures of real-world objects and visually presented words or nonwords. These tasks allowed us to detect potential memory differences across types of memoranda. Contrary to the hypothesis that the medial-frontal cortex helps control encoding fidelity, we found that anodal tDCS delivered over this brain region did not significantly improve subjects’ memory for visual stimuli, regardless of stimulus type. Our findings show no evidence that targeting medial-frontal cortex with tDCS changes the fidelity of our visual long-term memories.

The Impact of Stimulation Parameters on Cardiovascular Outcomes in Chronic Stroke Patients Following Transcranial Direct Current Stimulation-A Pilot Controlled, Randomized, Double-Blind Crossover Trial.

Stroke survivors often experience autonomic nervous system (ANS) dysfunction. While Transcranial Direct Current Stimulation (tDCS) has been shown to modulate the ANS when applied to the left hemisphere, its effects on the right hemisphere remain unexplored. We aimed to compare the effects of tDCS applied to both the injured and the contralateral hemispheres on heart rate variability (HRV) and functional capacity in individuals post-stroke. Twenty individuals with cerebral hemisphere lesions (ten with right-hemisphere lesions and ten with left-hemisphere lesions) were randomized into four groups: anodal and sham tDCS on the left temporal cortex (T3) and anodal and sham tDCS on the right temporal cortex (T4). HRV was assessed before the intervention, after the six-minute walk test (6MWT), and following tDCS. HRV data were categorized into frequency ranges: low frequency (LF), high frequency (HF), and sympathovagal balance. The 6MWT (meters) was conducted both pre- and post-tDCS. In individuals with right-hemisphere lesions, a higher global LF value was observed (right side: 71.4 ± 16.8 nu vs. left side: 65.7 ± 17.3 nu; p = 0.008), as well as lower values of the HF component (right side: 29.5 ± 18.9 nu vs. left side: 34.0 ± 17.4 nu; p = 0.047), consequently exhibiting higher global values of the low/high-frequency ratio (right side: 3.9 ± 2.8 vs. left side: 2.9 ± 2.4). Regarding the stimulation site, tDCS over T3 led to a lower overall value of the low/high-frequency ratio (left hemisphere: 3.0 ± 2.2 vs. right hemisphere: 3.7 ± 2.9; p = 0.040) regardless of the lesion location. A significant increase in the distance covered in the 6MWT was observed for individuals with lesions in both hemispheres after tDCS at T3. Participants with right-hemisphere lesions exhibited superior global sympathetic autonomic nervous system activity. When the tDCS was applied on the left hemisphere, it maintained lower sympathovagal balance values and improved functional capacity regardless of the hemisphere affected by the stroke.

Impact of Electric Field Magnitude in the Left Dorsolateral Prefrontal Cortex on Changes in Intrinsic Functional Connectivity Using Transcranial Direct Current Stimulation: A Randomized Crossover Study.

This study investigated whether the electric field magnitude (E-field) delivered to the left dorsolateral prefrontal cortex (L-DLPFC) changes resting-state brain activity and the L-DLPFC resting-state functional connectivity (rsFC), given the variability in tDCS response and lack of understanding of how rsFC changes. Twenty-one healthy participants received either 2 mA anodal or sham tDCS targeting the L-DLPFC for 10 min. Brain imaging was conducted before and after stimulation. The fractional amplitude of low-frequency fluctuation (fALFF), reflecting resting brain activity, and the L-DLPFC rsFC were analyzed to investigate the main effect of tDCS, main effect of time, and interaction effects. The E-field was estimated by modeling tDCS-induced individual electric fields and correlated with fALFF and L-DLPFC rsFC. Anodal tDCS increased fALFF in the left rostral middle frontal area and decreased fALFF in the midline frontal area (FWE p < 0.050), whereas sham induced no changes. Overall rsFC decreased after sham (positive and negative connectivity, p = 0.001 and 0.020, respectively), with modest and nonsignificant changes after anodal tDCS (p = 0.063 and 0.069, respectively). No significant differences in local rsFC were observed among the conditions. Correlations were observed between the E-field and rsFC changes in the L-DLPFC (r = 0.385, p = 0.115), left inferior parietal area (r = 0.495, p = 0.037), and right lateral visual area (r = 0.683, p = 0.002). Single-session tDCS induced resting brain activity changes and may help maintain overall rsFC. The E-field in the L-DLPFC is associated with rsFC changes in both proximal and distally connected brain regions to the L-DLPFC.

The interaction of oxytocin and nicotine addiction on psychosocial stress: an fMRI study

The anxiolytic effect of oxytocin (OXT) on psychosocial stress has been well documented, but the effectiveness under the interference of other factors still requires in-depth research. Previous studies have shown that nicotine addiction interacts with OXT on psychosocial stress on the behavioral level. However, the underlying neural mechanism of interaction between OXT and nicotine addiction on psychosocial stress has not been examined, and we conducted two experiments to reveal it. Firstly, after intranasal administration of randomized OXT or placebo (saline), a group of healthy participants (n = 27) and a group of smokers (n = 26) completed the Montreal Imaging Stress Task (MIST) in an MRI scanner. Secondly, a group of smokers (n = 22) was recruited to complete a transcranial direct current stimulation (tDCS) experiment, in which anodal tDCS was applied on subjects’ anterior right superior temporal gyrus (rSTG). In both experiment, subjective stress ratings, salivary cortisol samples and the amount of daily cigarette consumption were obtained from each participant. Analysis of variance were applied on both behavioral and neural data to examine the effects of OXT and nicotine addiction, and correlation analysis were used to examine relationships between neural and behavioral data. In first fMRI experiment, analysis of variance (ANOVA) revealed an interaction of OXT and nicotine addiction on subjective stress. In smokers, OXT failed to suppress the elevation of subjective stress and craving ratings after psychosocial stress. A voxel-wise ANOVA of fMRI data identified an interaction between OXT and nicotine addiction in anterior rSTG, and its functional connectivity with right middle frontal gyrus. Correlations between this functional connectivity and subjective psychosocial stress were also found abnormal in smokers. In second tDCS experiment, we found that under tDCS, OXT successfully suppressed the elevation of subjective stress and craving ratings after stress. In summary, we found that nicotine addiction blocked OXT’s anxiolytic on psychosocial stress, which was related to abnormalities in anterior rSTG. By applying anodal tDCS on anterior rSTG, OXT’s anxiolytic effect was restored in smokers. These findings will support further development on oxytocin’s intervention of psychosocial stress in nicotine addiction, and provides essential information for indicating OXT’s effectiveness.

Anodal tDCS improves the effect of neuromuscular training on the feedforward activity of lower extremity muscles in female taekwondo athletes with dynamic knee valgus

Transcranial direct current stimulation (tDCS) can increase cortical excitability of a targeted brain area. This study aimed to investigate the effect of adding anodal-tDCS (a-tDCS) to neuromuscular training (NMT) on the dynamic knee valgus (DKV) and feedforward activity (FFA) of knee muscles. Thirty-four Taekwondo athletes with DKV, were randomly assigned to either NMT + a-tDCS (N = 17) or NMT + sham tDCS (N = 17). DKV and the knee muscles' FFA at the moment of single and double-leg landing and lateral hopping tasks were evaluated before and after the interventions. DKV and FFA of the knee muscles was improved in all tasks (P < 0.05), however, between-group differences were not significant (P > 0.05). The FFA of the semitendinosus, vastus medialis, gluteus medius, and gastrocnemius muscles in the single-leg landing (P < 0.05), the gluteus medius, gluteus maximus, semitendinosus, biceps femoris, and gastrocnemius muscles in the double-leg landing (P < 0.05), and the gluteus medius, gluteus maximus, and gastrocnemius muscles in the lateral hopping (P < 0.05) tasks were significantly different between the groups. A-tDCS achieved significantly larger improvements in the feedforward activity of lower extremity muscles compared with sham-tDCS. However, between-group comparisons did not show a significant difference in DKV.

Transcranial Direct Current Stimulation in Children With Anisometropic Amblyopia.

Amblyopia is defined clinically as a difference in best-corrected visual acuity of two or more lines of acuity (0.2 logMAR) between the eyes. Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that can transiently alter the excitability of targeted brain areas in a polarity-specific manner. To detect the effect of tDCS on anisometropic amblyopia. This is a randomized controlled trial conducted on 78 patients with anisometropic amblyopia from 4.5 to 12 years of age. All patients presented with monocular amblyopia. They were divided into three groups; each group received five sessions of tDCS (anodal tDCS, cathodal tDCS, and sham tDCS). The active electrode was placed over occipital midline and the reference over central midline. Pattern visual-evoked potentials and contrast sensitivity tests were conducted before, immediately after, and 1 week after tDCS. The amplitude of P100 was significantly decreased immediately after and 1 week after cathodal tDCS. The latency of P100 immediately after and 1 week after anodal tDCS was significantly decreased and increased significantly after cathodal tDCS. The amplitude of P100 and maximum and minimum contrast sensitivities were significantly increased immediately after and 1 week after anodal tDCS, and maximum contrast sensitivity was significantly decreased immediately after cathodal tDCS. Anodal tDCS is a promising noninvasive modality for improvement of anisometropic amblyopia.

Eight sessions of transcranial electrical stimulation for postural response in people with Parkinson’s disease: A randomized trial

BackgroundImpairments in postural responses to perturbation are common in people with Parkinson’s disease (PwPD) and lack effective treatment. We recently showed that a single session of transcranial direct current stimulation (tDCS) promotes acute improvement of postural response to perturbation in PwPD. However, the effects of multiple tDCS sessions remain unclear. Research questionWhat is the efficacy of eight sessions of anodal tDCS on postural responses to external perturbation in PwPD? MethodsTwenty-two PwPD participated in this randomized, double-blind, parallel-arm, and sham-controlled study. Participants were randomly distributed into active (a-tDCS; n=11) or sham stimulation (s-tDCS; n=11). Eight tDCS sessions were applied over the primary motor cortex (M1), with the a-tDCS group receiving 2 mA for 20 minutes. Postural responses to external perturbations were assessed before, 48 hours after, and one month after (follow-up) the completion of tDCS sessions. Primary outcome measures included the onset latency of medial gastrocnemius (MG) muscle and range of center of pressure. Secondary outcomes included electromyography and CoP parameters, and prefrontal cortex (PFC) activity. ResultsANOVA revealed a trend for Group*Moment interaction for MG onset latency (p=0.058). a-tDCS tended to have shorter MG onset latency at post-test (p=0.040; SRM = −0.63) compared to pre-test. For the secondary outcomes, only a-tDCS decreased the time taken to recover balance after the perturbation at post-test and follow-up compared to pre-test (both p<0.001; SRM=-1.42 and −1.53, respectively). Also, only a-tDCS demonstrated lower PFC activity at post-test compared to pre-test (p=0.017; SRM = −0.82) and follow-up (p=0.001). SignificanceEight sessions of tDCS over M1 improved postural response to perturbation in PwPD. Some benefits lasted for at least a month. Neuromuscular and behavioral changes observed after the intervention were accompanied by decreased PFC activity (executive-attentional control), suggesting that tDCS applied over M1 can improve movement automaticity.

Feasibility of Simultaneous Anodal Transcranial Direct Current Stimulation During Gait Training in Chronic Stroke Patients: A Randomized Double-Blind Pilot Clinical Trial.

Transcranial direct current stimulation (tDCS) is a therapeutic tool for improving post-stroke gait disturbances, with ongoing research focusing on specific protocols for its application. We evaluated the feasibility of a rehabilitation protocol that combines tDCS with conventional gait training. This was a randomized, double-blind, single-center pilot clinical trial. Patients with unilateral hemiplegia due to ischemic stroke were randomly assigned to either the tDCS with gait training group or the sham stimulation group. The anodal tDCS electrode was placed on the tibialis anterior area of the precentral gyrus while gait training proceeded. Interventions were administered 3 times weekly for 4 weeks. Outcome assessments, using the 10-meter walk test, Timed Up and Go test, Berg Balance Scale, Functional Ambulatory Scale, Modified Barthel Index, and European Quality of Life 5 Dimensions 3 Level Version, were conducted before and after the intervention and again at the 8-week mark following its completion. Repeated-measures analysis of variance (ANOVA) was used for comparisons between and within groups. Twenty-six patients were assessed for eligibility, and 20 were enrolled and randomized. No significant differences were observed between the tDCS with gait training group and the sham stimulation group in gait speed after the intervention. However, the tDCS with gait training group showed significant improvement in balance performance in both within-group and between-group comparisons. In the subgroup analysis of patients with elicited motor-evoked potentials, comfortable pace gait speed improved in the tDCS with gait training group. No serious adverse events occurred throughout the study. Simultaneous anodal tDCS during gait training is a feasible rehabilitation protocol for chronic stroke patients with gait disturbances. URL: https://cris.nih.go.kr; Registration number: KCT0007601; Date of registration: 11 July 2022.

Reduced plasma interleukin-6 concentration after transcranial direct current stimulation to the prefrontal cortex

ObjectivesTranscranial direct stimulation (tDCS) targeted to the dorsolateral prefrontal cortex (DLPFC) reduces food intake and hunger, but its effects on circulating factors are unclear. We assessed the effect of repeated administration of tDCS to the left DLPFC (L-DLPFC) on concentrations of pro/anti-inflammatory and appetitive hormone concentrations. Materials and methodsTwenty-nine healthy adults with obesity (12 M; 42±11 y; BMI=39±8 kg/m2) received 3 consecutive inpatient sessions of either anodal or sham tDCS targeted to the L-DLPFC during a period of ad libitum food intake. Fasting plasma concentrations of IL-6, orexin, cortisol, TNF-α, IL-1β, ghrelin, PYY, and GLP-1 were measured before the initial and after the final tDCS sessions. ResultsIL-6 (β=-0.92 pg/ml p=0.03) decreased in the anodal group compared with sham, even after adjusting for kcal intake; there were no changes in other hormones. Mean kcal intake was associated with higher IL-1β and ghrelin concentrations after the ad libitum period (β=0.00018 pg/ml/kcal, p=0.03; β=0.00011 pg/ml/kcal, p=0.02; respectively), but not differ by intervention groups. ConclusionsIL-6 concentrations were reduced following anodal tDCS to the L-DLPFC independent of ad libitum intake. IL-6 concentrations reflect the inflammatory state of adiposity and may affect eating behavior and weight gain. These findings provide evidence of therapeutic benefit of tDCS.

The acute effects of motor cortex transcranial direct current stimulation on athletic performance in healthy adults: A systematic review and meta-analysis.

This systematic review and meta-analysis assesses independently the acute effects of anodal and cathodal motor cortex transcranial direct current stimulation (tDCS) on athletic performance in healthy adults. Besides, it evaluates the unique and conjoint effects of potential moderators (i.e., stimulation parameters, exercise type, subjects' training status and risk of bias). Online database search was performed from inception until March 18th 2024 (PROSPERO: CRD42023355461). Forty-three controlled trials were included in the systematic review, 40 in the anodal tDCS meta-analysis (68 effects), and 9 (11 effects) in the cathodal tDCS meta-analysis. Performance enhancement between pre- and post-stimulation was the main outcome measure considered. The anodal tDCS effects on physical performance were small to moderate (g= .29, 95%CI [.18, .40], PI = -.64 to 1.23, I2= 64.0%). Exercise type, training status and use of commercial tDCS were significant moderators of the results. The cathodal tDCS effects were null (g = .04, 95%CI [-.05, .12], PI = -.14 to .23, I2= 0%), with a small to moderate heterogeneity entirely due to sampling error, thus impairing further moderator analysis. These findings hold significant implications for the field of brain stimulation and physical performance, as they not only demonstrate a small to moderate effect of acute tDCS but also identify specific categories of individuals, devices and activities that are more susceptible to improvements. By addressing the multidimensional factors influencing the mechanisms of tDCS, we also provide suggestions for future research.

Early Boost of Linguistic Skills? Individualized Non-Invasive Brain Stimulation in Early Postacute Aphasia.

Non-invasive brain stimulation, such as transcranial direct current stimulation (tDCS), has been shown to increase the outcome of speech and language therapy (SLT) in chronic aphasia. Only a few studies have investigated the effect of add-on tDCS on SLT in the early stage of aphasia; this may be due to methodological reasons, in particular the influence of spontaneous remission and the difficulty of establishing stimulation protocols in clinical routines. Thirty-seven participants with subacute aphasia (PwA) after stroke (23 men, 14 women; mean age 62 ± 12 years; mean duration 49 ± 28 days) were included in two consecutive periods of treatment lasting two weeks each. During the first period (P1) the participants received 10 sessions of SLT, during the second period (P2) the aphasia therapy was supplemented by anodal left hemispheric 2 mA tDCS over the left hemisphere. Severity-specific language tests (Aachen Aphasia Test (AAT), n = 27 and Bielefeld Aphasia Screening-Reha (BIAS-R), n = 10) were administered before P1, between P1 and P2, and after P2. Where information was available, the results were corrected for spontaneous remission (AAT sample), and the therapy outcomes of P1 and P2 were compared. Participants' overall language abilities improved significantly during P1 and P2. However, improvement-as measured by the AAT profile level or the BIAS-R mean percentage value-during P2 (with tDCS) was significantly higher than during P1 (p < 0.001; AAT sample and p = 0.005; BIAS-R sample). Thus, tDCS protocols can be implemented in early aphasia rehabilitation. Despite the limitations of the research design, which are also discussed from an implementation science perspective, this is preliminary evidence that an individually tailored anodal tDCS can have a significant add-on effect on the outcome of behavioral aphasia therapy in subacute aphasia.

Single session and repeated anodal transcranial direct current stimulation over the right dorsolateral prefrontal cortex increases reflective thinking but not working memory updating performance

BackgroundAnodal transcranial direct current stimulation (tDCS) over the right dorsolateral prefrontal cortex (DLPFC) has shown to have effects on different domains of cognition yet there is a gap in the literature regarding effects on reflective thinking performance. ObjectiveThe current study investigated if single session and repeated anodal tDCS over the right DLPFC induces effects on judgment and decision-making performance and whether these are linked to working memory (updating) performance or cognitive inhibition. MethodsParticipants received anodal tDCS over the right DLPFC once (plus sham tDCS in a second session) or twice (24 h apart). In the third group participants received a single session of sham stimulation only. Cognitive characteristic measures were administered pre-stimulation (thinking disposition, impulsivity, cognitive ability). Experimental tasks included two versions of the Cognitive Reflection Test (numeric vs verbal-CRT), a set of incongruent base-rate vignettes, and two working memory tests (Sternberg task and n-back task). Forty-eight participants (mean age = 26.08 ± 0.54 years; 27 females) were recruited. ResultsSingle sessions of tDCS were associated with an increase in reflective thinking performance compared to the sham conditions, with stimulation improving scores on incongruent base rate tasks as well as marginally improving numeric CRT scores (compared to sham), but not thinking tasks without a numeric component (verbal-CRT). Repeated anodal stimulation only improved numeric CRT scores. tDCS did not increase working memory (updating) performance. These findings could not be explained by a practice effect or a priori differences in cognitive characteristics or impulsivity across the experimental groups. ConclusionThe current results demonstrate the involvement of the right DLPFC in reflective thinking performance which cannot be explained by working memory (updating) performance or general cognitive characteristics of participants.

Transcranial Direct Current Stimulation as Adjuvant to Gamified Rehabilitation for Upper Limb Function in Paediatric Brain Damage (CHILDBOOST Project): A Study Protocol for a Triple-Blind Randomised Controlled Trial

(1) Background and objectives: Paediatric brain injuries can lead to motor and cognitive deficits. Effective rehabilitation is critical for enhancing independence. While virtual reality (VR) and transcranial direct current stimulation (tDCS) have independently demonstrated beneficial effects on motor and cognitive functions, their combined efficacy and its cognitive effects remain to be explored in this population. We aim to investigate the effects of integrating tDCS with VR training on upper limb (UL) functionality and cognitive outcomes through a triple-blind randomised trial. (2) Methods: Twenty-eight children with hemiparesis secondary to non-progressive brain damage will be randomly allocated into two groups: active anodal tDCS (2 mA) plus UL VR training, and sham tDCS with identical VR training. The tDCS will target M1 of the affected or most affected hemisphere for 20 min, simultaneous to VR training. The following four assessments will be carried out: pre-intervention, post-intervention, and three- and six-months follow-up. (3) Results: This study will explore motor and cognitive outcomes of a motor-based intervention in paediatric brain damage. We hypothesise that the experimental group will show significant improvements in UL function and cognition, enhancing their functional recovery. (4) Conclusions: We propose a multidisciplinary therapeutic approach combining neuromodulation and VR to potentiate functional recovery through enhancing motor and cognitive performance in paediatric brain damage.

Effects of Anodal tDCS Applied Over the Cerebellum Combined with Physical Therapy on Center of Gravity Sway in a Patient with Cerebellar Ataxia: A Single-Case Study.

Damage to the cerebellum results in dysfunctional standing postural control. Patients with cerebellar ataxia have a larger sway in the center of gravity (COG) while standing. Transcranial direct current stimulation (tDCS) has been applied in the rehabilitation of patients with central nervous system disorders; however, its effect on COG sway in patients with cerebellar ataxia remains unknown. We aimed to confirm the effects of anodal cerebellar tDCS (ctDCS) combined with physical therapy on COG sway in a patient with cerebellar ataxia using a retrospective ABA single-case study design. This study involved a patient with left cerebellar hemorrhage. Walking and postural balance rehabilitation were conducted in phase A. Anodal ctDCS was combined with the walking and postural balance rehabilitation in phase B. We measured COG sway in the open- and closed-eyes standing conditions daily throughout all the phases. In the open-eyes standing condition, there was no significant change in COG sway in phase B. Conversely, in the closed-eyes standing condition, the circumferential area, total sway path length, and anteroposterior sway path length decreased in phase B. No change was observed in the mediolateral sway path length. The combination of anodal ctDCS and physical therapy may decrease COG sway in patients with cerebellar ataxia in the closed-eyes standing condition, and its effect may be greater in the anteroposterior direction.

The neural structures of theory of mind are valence-sensitive: evidence from three tDCS studies.

Several cortical structures are involved in theory of mind (ToM), including the dorsolateral prefrontal cortex (dlPFC), the ventromedial prefrontal cortex (vmPFC), and the right temporo- parietal junction (rTPJ). We investigated the role of these regions in mind reading with respect to the valence of mental states. Sixty-five healthy adult participants were recruited and received transcranial direct current stimulation (tDCS) (1.5mA, 20min) with one week interval in three separate studies. The stimulation conditions were anodal tDCS over the dlPFC coupled with cathodal tDCS over the vmPFC, reversed stimulation conditions, and sham in the first study, and anodal tDCS over the vmPFC, or dlPFC, and sham stimulation, with an extracranial return electrode in the second and third study. During stimulation, participants underwent the reading mind from eyes/voice tests (RMET or RMVT) in each stimulation condition. Anodal left dlPFC/cathodal right vmPFC stimulation increased the accuracy of negative mental state attributions, anodal rTPJ decreased the accuracy of negative and neutral mental state attributions, and decreased the reaction time of positive mental state attributions. Our results imply that the neural correlates of ToM are valence-sensitive.

The impact of transcranial direct current stimulation combined with interim testing on spatial route learning in patients with schizophrenia

BackgroundCognitive deficits in patients with schizophrenia have drawn widespread attention. Transcranial direct current stimulation (tDCS) can modulate cognitive processes by altering neuronal excitability. Previous studies have found that interim testing can enhance spatial route learning and memory in patients with schizophrenia. However, there has been limited research on the combined effects of these two methods on spatial route learning in these patients. ObjectiveTo investigate whether the combination of tDCS and interim testing can effectively contribute to the maintenance of spatial route memory in patients with schizophrenia. The study involved conducting route learning using interim testing after anodal tDCS treatment on the left dorsolateral prefrontal cortex (L-DLPFC). MethodsNinety-two patients with schizophrenia were recruited and divided into groups receiving anodal, sham, or no stimulation. The anodal group received L-DLPFC tDCS treatment 10 times over 5 days (twice daily for 20 min). After treatment, spatial route learning was assessed in interim testing. Correct recall rates of landmark positions and proactive interference from prior learning were compared among the groups. ResultsRegardless of stimulation type, the interim testing group outperformed the relearning group. Additionally, recall scores were higher following anodal stimulation, indicating the efficacy of tDCS. ConclusionsBoth tDCS and interim testing independently enhance the ability to learn new information in spatial route learning for patients with schizophrenia, indicating that tDCS of the left DLPFC significantly improves memory in these patients.

Independent effects of transcranial direct current stimulation and social influence on pain.

Transcranial direct current stimulation (tDCS) is a noninvasive neuromodulatory technique with the potential to provide pain relief. However, tDCS effects on pain are variable across existing studies, possibly related to differences in stimulation protocols and expectancy effects. We investigated the independent and joint effects of contralateral motor cortex tDCS (anodal vs cathodal) and socially induced expectations (analgesia vs hyperalgesia) about tDCS on thermal pain. We employed a double-blind, randomized 2 × 2 factorial cross-over design, with 5 sessions per participant on separate days. After calibration in Session 1, Sessions 2 to 5 crossed anodal or cathodal tDCS (20 minutes 2 mA) with socially induced analgesic or hyperalgesic expectations, with 6 to 7 days between the sessions. The social manipulation involved videos of previous "participants" (confederates) describing tDCS as inducing a low-pain state ("analgesic expectancy") or hypersensitivity to sensation ("hyperalgesic expectancy"). Anodal tDCS reduced pain compared with cathodal stimulation (F(1,19.9) = 19.53, P < 0.001, Cohen d = 0.86) and analgesic expectancy reduced pain compared with hyperalgesic expectancy (F(1,19.8) = 5.62, P = 0.027, Cohen d = 0.56). There was no significant interaction between tDCS and social expectations. Effects of social suggestions were related to expectations, whereas tDCS effects were unrelated to expectancies. The observed additive effects provide novel evidence that tDCS and socially induced expectations operate through independent processes. They extend clinical tDCS studies by showing tDCS effects on controlled nociceptive pain independent of expectancy effects. In addition, they show that social suggestions about neurostimulation effects can elicit potent placebo effects.

Non-Dominant Hemisphere Excitability Is Unaffected during and after Transcranial Direct Current Stimulation of the Dominant Hemisphere.

Transcranial direct current stimulation (tDCS) increases primary motor cortex (M1) excitability and improves motor performance when applied unilaterally to the dominant hemisphere. However, the influence of tDCS on contralateral M1 excitability both during and after application has not been quantified. The purpose was to determine the influence of tDCS applied to the dominant M1 on the excitability of the contralateral non-dominant M1. This study employed a double-blind, randomized, SHAM-controlled, within-subject crossover experimental design. Eighteen young adults performed two experimental sessions (tDCS, SHAM) in counterbalanced order separated by a one-week washout. Transcranial magnetic stimulation (TMS) was used to quantify the excitability of the contralateral M1 to which anodal tDCS was applied for 20 min with a current strength of 1 mA. Motor evoked potential (MEP) amplitudes were assessed in 5 TMS test blocks (Pre, D5, D10, D15, and Post). The Pre and Post TMS test blocks were performed immediately before and after tDCS application, whereas the TMS test blocks performed during tDCS were completed at the 5, 10, and 15 min stimulation timepoints. MEPs were analyzed with a 2 condition (tDCS, SHAM) × 5 test (Pre, D5, D10, D15, Post) within-subject ANOVA. The main effect for condition (p = 0.213), the main effect for test (p = 0.502), and the condition × test interaction (p = 0.860) were all not statistically significant. These results indicate that tDCS does not modulate contralateral M1 excitability during or immediately after application, at least under the current set of common tDCS parameters of stimulation.

Addressing the sources of inter-subject variability in E-field parameters in anodal tDCS stimulation over motor cortical network

Objetive: . Although transcranial direct current stimulation constitutes a non-invasive neuromodulation technique with promising results in a great variety of applications, its clinical implementation is compromised by the high inter-subject variability reported. This study aims to analyze the inter-subject variability in electric fields (E-fields) over regions of the cortical motor network under two electrode montages: the classical C3Fp2 and an alternative P3F3, which confines more the E-field over this region. Approach. Computational models of the head of 98 healthy subjects were developed to simulate the E-field under both montages. E-field parameters such as magnitude, focality and orientation were calculated over three regions of interest (ROI): M1S1, supplementary motor area (SMA) and preSMA. The role of anatomical characteristics as a source of inter-subject variability on E-field parameters and individualized stimulation intensity were addressed using linear mixed-effect models.Main results. P3F3 showed a more confined E-field distribution over M1S1 than C3Fp2; the latter elicited higher E-fields over supplementary motor areas. Both montages showed high inter-subject variability, especially for the normal component over C3Fp2. Skin, bone and CSF ROI volumes showed a negative association with E-field magnitude irrespective of montage. Grey matter volume and montage were the main sources of variability for focality. The curvature of gyri was found to be significantly associated with the variability of normal E-fields.Significance. Computational modeling proves useful in the assessment of E-field variability. Our simulations predict significant differences in E-field magnitude and focality for C3Fp2 and P3F3. However, anatomical characteristics were also found to be significant sources of E-field variability irrespective of electrode montage. The normal E-field component better captured the individual variability and low rate of responder subjects observed in experimental studies.

The effects of combining sensorimotor training with transcranial direct current stimulation on the anticipatory and compensatory postural adjustments in patients with chronic low back pain

Purpose To investigate the effects of concurrent sensorimotor training (SMT) and transcranial direct current stimulation (tDCS) on the anticipatory and compensatory postural adjustments (APAs and CPAs) in patients with chronic low back pain (CLBP). Method The interventions included (1) SMT plus tDCS and (2) SMT plus sham tDCS. Outcome measures were the normalized integrals of electromyography activity (NIEMG) during the phases of anticipatory and compensatory, and muscle onset latency. The investigated muscles were ipsilateral and contralateral multifidus (MF), transversus abdominus/internal oblique (TrA/IO), and gluteus medius (GM). Results Between-group comparisons demonstrated that ipsilateral TrA/IO NIEMG during CPA1 (p = 0.010) and ipsilateral GM NIEMG during CPA1 (p = 0.002) and CPA2 (p = 0.025) were significantly lower in the SMT combined with tDCS than in the control group. Furthermore, this group had greater NIEMG for contralateral GM during APA1 than the control group (p = 0.032). Moreover, the onset latency of contralateral TrA/IO was significantly earlier after SMT combined with tDCS (p = 0.011). Conclusions Both groups that received SMT showed positive effects, but anodal tDCS had an added value over sham stimulation for improving postural control strategies in patients with CLBP. Indeed, SMT combined with tDCS leads to stronger APA and less demand for CPA. RCT registration number IRCT20220228054149N1 Registration date 2022-04-04