tDCS Montages Research Articles

Novel tDCS montage favors lower limb motor imagery detection.

This work studies a novel transcranial direct current stimulation (tDCS) montage to improve a brain-machine interface (BMI) lower limb motor imagery detection. The tDCS montage is composed by two anodes and one cathode. One anode is located over the motor cortex and the other one over the cerebellum. Ten healthy subjects participated in this experiment. They were randomly separated into two groups: sham, which received a fake stimulation, and active tDCS, which received a real stimulation. Each subject was experimented on five consecutive days. Results pointed out that there was a significant difference $(p < 0 .05)$ in the classification accuracy between the sham and the active tDCS group. On each of the five days of the experiment the active tDCS group achieved better accuracy results than the sham group: 4%, 10%, 10%, 9% and 7% higher respectively.

Frontoparietal tDCS Benefits Visual Working Memory in Older Adults With Low Working Memory Capacity.

Working memory (WM) permits maintenance of information over brief delays and is an essential executive function. Unfortunately, WM is subject to age-related decline. Some evidence supports the use of transcranial direct current stimulation (tDCS) to improve visual WM. A gap in knowledge is an understanding of the mechanism characterizing these tDCS linked effects. To address this gap, we compared the effects of two tDCS montages designed on visual working memory (VWM) performance. The bifrontal montage was designed to stimulate the heightened bilateral frontal activity observed in aging adults. The unilateral frontoparietal montage was designed to stimulate activation patterns observed in young adults. Participants completed three sessions (bilateral frontal, right frontoparietal, sham) of anodal tDCS (20 min, 2 mA). During stimulation, participants performed a visual long-term memory (LTM) control task and a visual WM task. There was no effect of tDCS on the LTM task. Participants receiving right unilateral tDCS showed a WM benefit. This pattern was most robust in older adults with low WM capacity. To address the concern that the key difference between the two tDCS montages could be tDCS over the posterior parietal cortex (PPC), we included new analyses from a previous study applying tDCS targeting the PPC paired with a recognition VWM task. No significant main effects were found. A subsequent experiment in young adults found no significant effect of either tDCS montage on either task. These data indicate that tDCS montage, age and WM capacity should be considered when designing tDCS protocols. We interpret these findings as suggestive that protocols designed to restore more youthful patterns of brain activity are superior to those that compensate for age-related changes.

Evidence of transcranial direct current stimulation-generated electric fields at subthalamic level in human brain in vivo

BackgroundTranscranial direct current stimulation (tDCS) is a promising brain modulation technique for several disease conditions. With this technique, some portion of the current penetrates through the scalp to the cortex and modulates cortical excitability, but a recent human cadaver study questions the amount. This insufficient intracerebral penetration of currents may partially explain the inconsistent and mixed results in tDCS studies to date. Experimental validation of a transcranial alternating current stimulation-generated electric field (EF) in vivo has been performed on the cortical (using electrocorticography, ECoG, electrodes), subcortical (using stereo electroencephalography, SEEG, electrodes) and deeper thalamic/subthalamic levels (using DBS electrodes). However, tDCS-generated EF measurements have never been attempted. ObjectiveWe aimed to demonstrate that tDCS generates biologically relevant EF as deep as the subthalamic level in vivo. MethodsPatients with movement disorders who have implanted deep brain stimulation (DBS) electrodes serve as a natural experimental model for thalamic/subthalamic recordings of tDCS-generated EF. We measured voltage changes from DBS electrodes and body resistance from tDCS electrodes in three subjects while applying direct current to the scalp at 2 mA and 4 mA over two tDCS montages. ResultsVoltage changes at the level of deep nuclei changed proportionally with the level of applied current and varied with different tDCS montages. ConclusionsOur findings suggest that scalp-applied tDCS generates biologically relevant EF. Incorporation of these experimental results may improve finite element analysis (FEA)-based models.

Modelling the effect of electrode displacement on transcranial direct current stimulation (tDCS)

Objective. Transcranial direct current stimulation (tDCS) is a neuromodulatory technique that delivers a low-intensity, direct current to cortical areas with the purpose of modulating underlying brain activity. Recent studies have reported inconsistencies in tDCS outcomes. The underlying assumption of many tDCS studies has been that replication of electrode montage equates to replicating stimulation conditions. It is possible however that anatomical difference between subjects, as well as inherent inaccuracies in montage placement, could affect current flow to targeted areas. The hypothesis that stimulation of a defined brain region will be stable under small displacements was tested. Approach. Initially, we compared the total simulated current flowing through ten specific brain areas for four commonly used tDCS montages: F3-Fp2, C3-Fp2, Fp1-F4, and P3-P4 using the software tool COMETS. The effect of a slight (~1 cm in each of four directions) anode displacement on the simulated regional current density for each of the four tDCS montages was then determined. Current flow was calculated and compared through ten segmented brain areas to determine the effect of montage type and displacement. The regional currents, as well as the localised current densities, were compared with the original electrode location, for each of these new positions. Main results. Recommendations for montages that maximise stimulation current for the ten brain regions are considered. We noted that the extent to which stimulation is affected by electrode displacement varies depending on both area and montage type. The F3-Fp2 montage was found to be the least stable with up to 38% change in average current density in the left frontal lobe while the Fp1-F4 montage was found to the most stable exhibiting only 1% change when electrodes were displaced. Significance. These results indicate that even relatively small changes in stimulation electrode placement appear to result in surprisingly large changes in current densities and distribution.

Incomplete evidence that increasing current intensity of tDCS boosts outcomes

BackgroundTranscranial direct current stimulation (tDCS) is investigated to modulate neuronal function by applying a fixed low-intensity direct current to scalp. ObjectivesWe critically discuss evidence for a monotonic response in effect size with increasing current intensity, with a specific focus on a question if increasing applied current enhance the efficacy of tDCS. MethodsWe analyzed tDCS intensity does-response from different perspectives including biophysical modeling, animal modeling, human neurophysiology, neuroimaging and behavioral/clinical measures. Further, we discuss approaches to design dose-response trials. ResultsPhysical models predict electric field in the brain increases with applied tDCS intensity. Data from animal studies are lacking since a range of relevant low-intensities is rarely tested. Results from imaging studies are ambiguous while human neurophysiology, including using transcranial magnetic stimulation (TMS) as a probe, suggests a complex state-dependent non-monotonic dose response. The diffusivity of brain current flow produced by conventional tDCS montages complicates this analysis, with relatively few studies on focal High Definition (HD)-tDCS. In behavioral and clinical trials, only a limited range of intensities (1-2 mA), and typically just one intensity, are conventionally tested; moreover, outcomes are subject brain-state dependent. Measurements and models of current flow show that for the same applied current, substantial differences in brain current occur across individuals. Trials are thus subject to inter-individual differences that complicate consideration of population-level dose response. ConclusionThe presence or absence of simple dose response does not impact how efficacious a given tDCS dose is for a given indication. Understanding dose-response in human applications of tDCS is needed for protocol optimization including individualized dose to reduce outcome variability, which requires intelligent design of dose-response studies.

Effect of transcranial direct current stimulation combined with cognitive training on cognitive functioning in older adults with HIV: A pilot study

ABSTRACTThe objective of this study was to examine combination speed of processing (SOP) cognitive remediation therapy (CRT) and transcranial direct stimulation (tDCS) as neurorehabilitation in older HIV+ adults. Thirty-three HIV+ adults aged 50+ completed neurocognitive testing and were randomized to either active (n = 17) or sham (n = 16) tDCS. Both conditions received 10 1-hour sessions of SOP CRT, with either active or sham tDCS for the first 20 minutes. Participants then completed a posttest assessment. Repeated measures analysis of variance examining Time X Condition showed small-to-medium effects in the expected direction for an executive (d = 0.36), and SOP measure (d = 0.49), while medium-to-large effects were observed for an executive/attention (d = 0.60) and oral reading measure (d = 0.75). The only statistically significant interaction was the oral reading measure. Small-to-medium and medium-to-large effects (ds = 0.32, 0.58) were found for two SOP measures in the opposite direction (sham group showing greater improvements). Further trials of CRT and tDCS in this population are needed, including larger samples and a nonactive control and tDCS only condition, as is determination of which parameters of each technique (e.g., tDCS montage, timing of tDCS, domain targeted in CRT, number of sessions) are most effective in improving cognitive outcomes, durability of training gains, and translation to everyday functioning.

The differential effects of unihemispheric and bihemispheric tDCS over the inferior frontal gyrus on proactive control

This study examined the effects of bihemispheric and unihemispheric transcranial Direct Current Stimulation (tDCS) over the inferior frontal gyrus (IFG) on proactive control.Sixteen participants were randomized to receive (i) bihemispheric tDCS, with a 35cm2 anodal electrode of the right IFG and a 35cm2 cathode electrode of left IFG or (ii) unihemispheric tDCS, with a 35cm2 anodal electrode of the right IFG and a 100cm2 electrode of the left IFG or (iii) sham tDCS, while performing a prepotent inhibition task. There were significant speed-accuracy tradeoff effects in terms of switch costs: unihemispheric tDCS significantly decreased the accuracy when compared to bihemispheric, and sham tDCS, while increased response time when comparing to bihemispheric and sham tDCS. The computational model showed a symmetrical field intensity for the bihemispheric tDCS montage, and an asymmetrical for the unihemispheric tDCS montage. This study confirms that unihemispheric tDCS over the rIFG has a significant impact on response inhibition. The lack of results of bihemispheric tDCS brings two important findings for this study: (i) left IFG seems to be also critically associated with inhibitory response control, and (ii) these results highlight the importance of considering the dual effects of tDCS when choosing the electrode montage.

Low Intensity Focused tDCS Over the Motor Cortex Shows Inefficacy to Improve Motor Imagery Performance.

Transcranial direct current stimulation (tDCS) is a brain stimulation technique that can enhance motor activity by stimulating the motor path. Thus, tDCS has the potential of improving the performance of brain-computer interfaces during motor neurorehabilitation. tDCS effects depend on several aspects, including the current density, which usually varies between 0.02 and 0.08 mA/cm2, and the location of the stimulation electrodes. Hence, testing tDCS montages at several current levels would allow the selection of current parameters for improving stimulation outcomes and the comparison of montages. In a previous study, we found that cortico-cerebellar tDCS shows potential of enhancing right-hand motor imagery. In this paper, we aim to evaluate the effects of the focal stimulation of the motor cortex over motor imagery. In particular, the effect of supplying tDCS with a 4 × 1 ring montage, which consists in placing an anode on the motor cortex and four cathodes around it, over motor imagery was assessed with different current densities. Electroencephalographic (EEG) classification into rest or right-hand/feet motor imagery was evaluated on five healthy subjects for two stimulation schemes: applying tDCS for 10 min on the (1) right-hand or (2) feet motor cortex before EEG recording. Accuracy differences related to the tDCS intensity, as well as μ and β band power changes, were tested for each subject and tDCS modality. In addition, a simulation of the electric field induced by the montage was used to describe its effect on the brain. Results show no improvement trends on classification for the evaluated currents, which is in accordance with the observation of variable EEG band power results despite the focused stimulation. The lack of effects is probably related to the underestimation of the current intensity required to apply a particular current density for small electrodes and the relatively short inter-electrode distance. Hence, higher current intensities should be evaluated in the future for this montage.

The critical role of cognitive-based trait differences in transcranial direct current stimulation (tDCS) suppression of food craving and eating in frank obesity

Obesity remains a major public health concern and novel treatments are needed. Transcranial direct current stimulation (tDCS) is a neuromodulation technique shown to reduce food craving and consumption, especially when targeting the dorsolateral prefrontal cortex (DLPFC) with a right anode/left cathode electrode montage. Despite the implications to treat frank (non-bingeeating) obesity, no study has tested the right anode/left cathode montage in this population. Additionally, most tDCS appetite studies have not controlled for differences in traits under DLPFC control that may influence how well one responds to tDCS. Hence, N = 18 (10F/8M) adults with frank obesity completed the Dutch Eating Behavior Questionnaire-Restraint and Barratt Impulsiveness Scale, and received 20 min of 2 mA active tDCS and control tDCS session. Craving and eating was assessed at both sessions with a food photo “wanting” test and in-lab measures of total, preferred, and less-preferred kilocalories consumed of three highly palatable snack foods. While main effects of tDCS vs. control were not found, significant differences emerged when trait scores were controlled. tDCS reduced food craving in females with lower attention-type impulsiveness (p = 0.047), reduced preferred-food consumption in males with lower intent to restrict calories (p = 0.024), and reduced total food consumption in males with higher non-planning-type impulsiveness (p = 0.009) compared to control tDCS. This is the first study to find significant reductions in food craving and consumption in a sample with frank obesity using the most popular tDCS montage in appetite studies. The results also highlight the cognitive-based heterogeneity of individuals with obesity and the importance of considering these differences when evaluating the efficacy of DLPFC-targeted tDCS in future studies aimed at treating obesity.

Transcranial direct current stimulation (tDCS) reveals a dissociation between SNARC and MARC effects: Implication for the polarity correspondence account

The concept of stimulus response compatibility (SRC) refers to the existence of a privileged association between a specific stimulus feature and a specific response feature. Two examples of SRC are the Spatial Numerical Association of Response Codes (SNARC) and the Markedness Association of Response Codes (MARC) effects. According to the polarity correspondence principle, these two SRC effects occur because of a match between the most salient dimensions of stimulus and response. Specifically, the SNARC effect would be caused by a match between right-sided responses and large numbers, while a match between right-sided responses and even numbers would give rise to the MARC effect. The aim of the present study was to test the validity of the polarity correspondence principle in explaining these two SRC effects. To this end, we applied transcranial direct current stimulation (tDCS) over left and right posterior parietal cortex (PPC), which is thought to be the neural basis of salience processing, during a parity judgement task. Results showed that cathodal tDCS over the PPC significantly reduced the MARC effect but did not affect the SNARC effect, suggesting a dissociation between the two effects. That is, the MARC would rely on a salience processing mechanism, whereas the SNARC would not. Despite this interpretation is in need of further experimental confirmations (i.e., testing different tasks or using different tDCS montages), our results suggest that the polarity correspondence principle can be a plausible explanation only for the MARC effect but not for the SNARC effect.

Effect of tDCS stimulation of motor cortex and cerebellum on EEG classification of motor imagery and sensorimotor band power

BackgroundTranscranial direct current stimulation (tDCS) is a technique for brain modulation that has potential to be used in motor neurorehabilitation. Considering that the cerebellum and motor cortex exert influence on the motor network, their stimulation could enhance motor functions, such as motor imagery, and be utilized for brain-computer interfaces (BCIs) during motor neurorehabilitation.MethodsA new tDCS montage that influences cerebellum and either right-hand or feet motor area is proposed and validated with a simulation of electric field. The effect of current density (0, 0.02, 0.04 or 0.06 mA/cm2) on electroencephalographic (EEG) classification into rest or right-hand/feet motor imagery was evaluated on 5 healthy volunteers for different stimulation modalities: 1) 10-minutes anodal tDCS before EEG acquisition over right-hand or 2) feet motor cortical area, and 3) 4-seconds anodal tDCS during EEG acquisition either on right-hand or feet cortical areas before each time right-hand or feet motor imagery is performed. For each subject and tDCS modality, analysis of variance and Tukey-Kramer multiple comparisons tests (p <0.001) are used to detect significant differences between classification accuracies that are obtained with different current densities. For tDCS modalities that improved accuracy, t-tests (p <0.05) are used to compare μ and β band power when a specific current density is provided against the case of supplying no stimulation.ResultsThe proposed montage improved the classification of right-hand motor imagery for 4 out of 5 subjects when the highest current was applied for 10 minutes over the right-hand motor area. Although EEG band power changes could not be related directly to classification improvement, tDCS appears to affect variably different motor areas on μ and/or β band.ConclusionsThe proposed montage seems capable of enhancing right-hand motor imagery detection when the right-hand motor area is stimulated. Future research should be focused on applying higher currents over the feet motor cortex, which is deeper in the brain compared to the hand motor cortex, since it may allow observation of effects due to tDCS. Also, strategies for improving analysis of EEG respect to accuracy changes should be implemented.

The Critical Role of Individual Trait Differences in Transcranial Direct Current Stimulation Outcomes: Effects in a Sample with Non Binge‐Eating Obesity

BackgroundObesity is a major public health concern and effective treatments for the disease are lacking. Transcranial direct current stimulation (tDCS) is a non‐invasive, neuromodulation technique that reduces food craving and consumption, especially when using a right‐anode/left‐cathode (RA/LC) montage targeting the dorsolateral prefrontal cortex (DLPFC). Despite the implications of these findings to treat frank (non‐binge‐eating) obesity, no study has tested RA/LC tDCS on this population. Moreover, most tDCS studies on appetite have not considered the potential influence of sex or of individual differences in psychological traits that are under the control of the DLPFC when evaluating the efficacy of tDCS on appetite variables.ObjectiveThis study tested the hypothesis that tDCS reduces food consumption and craving in frank obesity and that sex and individual trait differences influence these effects.MethodsN=18 (10F/8M) adults with frank obesity (BMI ≥ 30 with no binge‐eating) completed the Dutch Eating Behavior Questionnaire‐Restraint and Barratt Impulsiveness Scale. Both have subscales related to cognitive inhibition, a putative functional mechanism underlying tDCS effects on appetite. Participants received 20 minutes of 2mA tDCS and a sham session. Total and preferred‐food consumption was assessed with an in‐lab eating test and craving was assessed with a food photo “wanting” test.ResultsThe effect of tDCS on food consumption or craving did not differ from sham. However, significant differences emerged when sex and psychological trait scores were controlled. tDCS vs. sham reduced food craving in individuals with lower attention‐type impulsiveness (p=0.043), total kilocalories consumed in males with lower non‐planning‐type impulsiveness (p=0.009), and preferred‐food kilocalories consumed in males with lower intent to restrict calories (p=0.024).ConclusionThis is the first study to find significant changes in food craving and consumption in a population with frank obesity with the most popular tDCS montage used in appetite studies. The findings also highlight the psychological heterogeneity of individuals with obesity and the importance of identifying these and sex differences in future tDCS studies aimed at treating obesity.Support or Funding InformationNIH‐T32Pre‐Doctoral training grant to MKR made possible by UAB's Nutrition Obesity Research Center.

Effects of prefrontal bipolar and high-definition transcranial direct current stimulation on cortical reactivity and working memory in healthy adults

Transcranial direct current stimulation (tDCS) is a well-recognised neuromodulatory technology which has been shown to induce short-lasting changes in motor-cortical excitability. The recent and rapid expansion of tDCS into the cognitive domain, however, necessitates deeper mechanistic understanding of its neurophysiological effects over non-motor brain regions. The present study utilised transcranial magnetic stimulation combined with electroencephalography (TMS-EEG) to probe the immediate and longer-term effects of both a bipolar (BP-tDCS) and more focal 4×1 High-Definition tDCS (HD-tDCS) montage applied over the left DLPFC on TMS-evoked potentials (TEPs) and oscillations in 19 healthy adult participants. 2-back working memory (WM) performance was also assessed as a marker of cognitive function. Region of interest (ROI) analyses taken from the F1 electrode directly adjacent to the stimulation site revealed increased P60 TEP amplitudes at this location 5min following BP-tDCS and 30min following HD-tDCS. Further global cluster based analyses of all scalp electrodes revealed widespread neuromodulatory changes following HD-tDCS, but not BP-tDCS, both five and 30min after stimulation, with reductions also detected in both beta and gamma oscillatory power over parieto-occipital channels 30min after stimulation. No significant changes in WM performance were observed following either HD-tDCS or BP-tDCS. This study highlights the capacity for single-session prefrontal anodal tDCS montages to modulate neurophysiological processes, as assessed with TMS-EEG.

P102 Multiple-electrode tDCS montage modulates shifting and risk taking behaviors

Introduction Risk taking and set-shifting are two domain aspects of executive functions which play a fundamental part in our everyday life. Although the involvement of the pre-frontal cortex in executive functions is well established, there is a debate regarding the lateralization of the prefrontal cognitive control network (Goel and Vartanian, 2005; Witt and Stevens, 2013). Different stimulation studies demonstrated inconsistent results regarding to which montage resulted in enhanced set- shifting and decreased risk taking behaviors (Fecteau et al., 2007; Leite et al., 2013). The inconsistencies might partially result from bilateral involvement of the dorsal lateral prefrontal cortex (DLPFC), because previous stimulation studies could activate by anodal stimulation only the left or right DLPFC, but not both. Objectives Here we aimed to explore this debate by applying a novel three-electrodes transcranial direct current stimulation (tDCS) montage over the left and right dorsal lateral prefrontal cortex (DLPFC) to modulate cognitive control tasks. Materials & method In a between subjects design, 34 healthy participants were randomly assigned to either active tDCS or sham group. After the stimulation, the participants performed cognitive control tasks (Wisconsin Card Sorting Test (WCST) and the Balloon Analogue Risk Task (BART). Results A one-way MANCOVA revealed a significant multivariate main effect for stimulation group F(2, 27) = 4.53, p Download : Download high-res image (287KB) Download : Download full-size image Conclusions We demonstrated enhancement of both shifting and risk taking via reduction of the observed reaction time. The current study points out to new possibilities for tDCS montage, which enable anodal stimulation of two different brain regions simultaneously and thus contributes to a better understanding of the neural networks and hemispheric connectivity.

P183 Transcranial direct current stimulation improves sleep quality

Introduction Sleep disturbance has been recognized as a common and significant complication linked to decreased quality of life in patients with neuropsychiatric disease. Currently, pharmacological therapy is the most common treatment for sleep disturbance, although benefits tend to be limited. Objective We assessed whether transcranial direct current stimulation (tDCS) improves sleep quality in patients with neurological and psychiatric diseases. Materials & methods 26 neuropsychiatric patients (age 19–86, n = 2 stroke, n = 4 dysphagia, n = 3 pain, n = 8 hereditary spastic paraparesis, n = 4 Parkinson’s disease, n = 2 aphasia, n = 3 depression) underwent tDCS treatment. tDCS montage was different for each pathology. The intensity of stimulation was set at 2 mA and delivered for 20 min for 5 consecutive days. The Pittsburgh Sleep Quality Index (PSQI) ( Buysse, 1989 ) was used to assess sleep quality at baseline (T0) and after the tDCS treatment (T1). Results One way ANOVA analysis showed that anodal tDCS improved PSQI total score by 13% [(mean ± SD) T0: 6.3 ± 4 vs T1: 5 ± 3.6; p = 0.004] and PSQI sub-item scores subjective quality of sleep by 22% (T0: 1.1 ± 0.7 vs T1: 0.92 ± 0.68; p = 0.016) and habitual sleep efficiency by 17% (T0: 0.31 ± 0.67 vs T1: 0.04 ± 0.19 p = 0.031). No differences were found between pathology. Conclusion Despite the small sample size and different tDCS montages, data from our observational study showed that anodal tDCS for five days improved sleep quality and efficiency. tDCS could be a non-invasive and valuable new tool for managing sleep disorders.

Abstract TP145: Anodal 2mA Transcranial Direct Current Stimulation Over Affected Parietal-Insular-vestibular Cortex Shows No Effect on Lateropulsion Following Strokei

Objective: To assess the effects of 2mA transcranial Direct Current Stimulation (tDCS) over the affected Parietal-Insular-Vestibular Cortex (PIVC) on seated posture of patients with lateropulsion following stroke. We hypothesized that bilateral electrode placement over PIVC (vs active control) would produce a change in seated posture. Background: Lateropulsion following stroke (Pusher Syndrome) is characterized by lateral displacement of subjective postural vertical toward the weak side. It is caused by lesions affecting vestibular projections to the Ventral Lateral Thalamus (VLT) or projections from the VLT to the Parietal-Insular-Vestibular Cortex (PIVC). Methods: Seventeen subjects with Burke Lateropulsion Scale scores ≥ 2 within 30 days of an ischemic stroke signed an IRB-approved consent. They received 2mA tDCS delivered using 25cm 2 saline soaked sponge electrodes via one of two montages: Test (anode over the affected PIVC and cathode opposite PIVC) versus Active Control (anode over the affected PIVC and cathode over the opposite supra-orbital region). PIVC was defined using EEG 10/20 coordinates. Seated medial-lateral center of pressure (COP-X) was measured using a custom-designed chair mounted on an AMTI™ analog-to-digital forceplate. An inclinometer strapped to the chest and aligned with the sternum measured lateral trunk tilt. Data were collected prior to, then at 5, 10, and 15 minutes during tDCS and 5 min following tDCS. Results: Repeated Measures Analysis of Variance rejected the hypothesis of an interaction between Montage and Time for: mean COP-X displacement (in) (Wilks’ λ F = 0.647 df =(4, 13), P = 0.639); mean speed of COP-X (in/s) (Wilks’ λ F = 0.740 df =(4, 13), P =0.581); mean inclinometer tilt (degrees) (Wilks’ λ F = 0.740 df =(4, 13), P =0.581). Conclusion: Neither tDCS montage showed improvement in COP-X displacement, COP-X movement velocity or inclinometer readings. These negative results are important to encourage the development of alternative tDCS stimulation parameters or identification of alternative cortical or vestibular tDCS targets for the treatment of Lateropulsion Following Stroke.

TDCS potentiation provides no evidence for a link between right dorsal–lateral prefrontal cortical activity and empathic responding

ABSTRACTPrevious studies suggest the dorsolateral prefrontal cortex (DLPFC) is involved in processing of empathic concern. This has not been experimentally tested to date. We tested the hypotheses that electrical potentiation in the right DLPFC would be associated with increased empathic concern and prosocial behavior. Participants were randomly allocated to one of three transcranial Direct Current Stimulation (tDCS) conditions: (a) relative right potentiation, (b) relative left potentiation, and (c) sham. Participants viewed images of African children in distressing circumstances, and completed measures of empathic concern pre- and post-tDCS manipulation. Contrary to our prediction, neither effects, nor interactions of heightened empathic concern were observed. These results conflict with previous studies using this bilateral tDCS montage. Explanations could be that stimulation used in this study had been simply too weak (1.5 mA). Alternatively, the area of the DLPFC involved in emotion regulation is closer to the cortex than the area involved in empathic concern, and more easily potentiated by tDCS. Therefore, the DLPFC potentiation in the present study may have linked empathic concern with adaptive emotion regulation strategies. Future research could examine this possibility using measures of emotion regulation and higher fidelity neurostimulation (e.g., repetitive Transcranial Magnetic Stimulation [rTMS]).

Brainkit: A Platform for Small-Scale Rational Design of tDCS Montages

A major obstacle to using tDCS for therapy and cognitive enhancement is the problem of selecting parameters like electrode position which are likely to achieve particular goals for an individual person. tDCS parameters which create significant effects at a group level are often unreliable at an individual level, and in many cases there is little a priori evidence for which regions should be targeted to achieve an effect (especially in the case of complex cognitive functions). A potential way to address these issues is combining tDCS with individual-level neurophysiological data. BrainKit is an open-source tDCS stimulator integrated with tools for automatically predicting effective tDCS parameters based on brain dynamics measurement. Covariance of physiological and behavioral variables is exploited to identify brain variables which predict behavioral variables of interest, and a tDCS model is applied to generate predicted parameters for driving these variables in a desired direction. BrainKit uses a novel current regulator, which allows scalp capacitance measurement (recently developed as a low-resolution neuroimaging technique) to be integrated and used as a source of neurophysiological data. Preliminary data suggest that capacitive measurements reflect natural and tDCS-induced brain activity changes, and are valuable for generating tDCS “targets”. BrainKit therefore offers a simple, integrated platform for rational design and optimization of tDCS montages and delivery of stimulation which may improve the effectiveness and applicability of tDCS in clinical and cognitive-enhancement settings.

Evaluation of different procedure involved in the Transcranial Direct Current Stimulation (tDCS) technique experimental application

Introduction: The transcranial direct current stimulation (tDCS) is a non-invasive technique, which induces neuroplastic changes in the central nervous system of animals and humans. Furthermore, tDCS has been suggested as a therapeutic tool for pain management. The aim of this study was to standardize a non-invasive tDCS technique indexed by the nociceptive response of rats submitted to different conditions necessary to the tDCS application. Method: 60-day-old male Wistar rats (n=65), divided into 6 groups: control(C); non-active sham (NAS); active-sham (AS); active-sham restrained (ASR); non-active sham restrained (NASR); active tDCS treatment. Animals received treatment during 30 seconds (sham-active) or 20 minutes (restraint and tDCS)/8 days. Nociceptive threshold was assessed by Hot Plate test at baseline, immediately and 24h after the first session, immediately and 24h after the last session. Variance analysis of repeated measurements followed by Bonferroni was performed for intra-group comparison. Results: Physical restraint and 30 seconds stimulation (sham-tDCS) increased pain sensitivity (P≤0.05), and tDCS treatment was able to prevent the thermal hyperalgesia. Our original tDCS montage is similar to that used in the procedure with humans, because it is not an invasive technique. The electrodes are positioned on the head, and the animals are immobilized during the 20-minute treatment. As this procedure could involve behavior and neurochemical alterations due to stress induced by restriction (thus, it creates a research bias), we hypothesized that a 30-second electrical stimulus application (sham-tDCS) and the physical restriction used during tDCS treatment might alter nociceptive response in rats. Conclusion: There are methodological limitations in the present tDCS-technique. Although active-tDCS treatment is able to prevent these harmful effects, interference of these factors has to be considered during the results’ analysis. Future adaptations of the tDCS-technique in rats are required to evaluate its therapeutic effects. Keywords: tDCS; animal model; nociception; thermal hyperalgesia; stress restraint

Neural correlates of trait resiliency: Evidence from electrical stimulation of the dorsolateral prefrontal cortex (dLPFC) and orbitofrontal cortex (OFC)

The topic of trait resiliency has recently been studied in many fields including personality psychology, clinical psychology and health sciences. Neuroimaging studies show some regions in the prefrontal cortex that are involved in resilience and coping behaviour. This study was primarily aimed to examine the effectiveness of transcranial direct current stimulation (tDCS) on level of trait resiliency of participants. Eighty students were randomly assigned into four groups. Each group completed the Conner-Davidson Resilience Scale (CD-RISC) once before brain stimulation and once 5min after receiving electrical brain stimulation for 15min with 1mA current intensity. Each group underwent a specific tDCS montage and results showed that anodal tDCS over the left dLPFC concurrently with cathode tDCS over the right dLPFC (Experiment 1) as well as anodal stimulation of the left dLPFC and cathodal stimulation of the right OFC (Experiment 2) led to an increase in the level of trait resiliency of participants. Results also showed a larger effect size for experiment 2. The findings of the present study implicate the involvement of the PFC regions in trait resiliency, especially in term of interaction of the dLPFC and the OFC regions in trait resiliency suggesting neural correlates underlying trait resiliency.