Application Of Cathodal tDCS Research Articles

Uncertainty Modulates the Effect of Transcranial Stimulation Over the Right Dorsolateral Prefrontal Cortex on Decision-Making Under Threat.

Threat is a strategy that can be used to impact decision-making processes in bargaining. Abundant evidence suggests that credible threat and incredible threat both influence the obeisance of others. However, it is not clear whether the decision-making processes under credible threat and incredible threat during bargaining involve differential neurocognitive mechanisms. Here, we employed cathodal transcranial direct current stimulation (tDCS) to deactivate the right dorsolateral prefrontal cortex (rDLPFC) to address this question while subjects allocated and reported the subjective probability of future rejection under incredible threat and credible threat. We found that application of cathodal tDCS over the rDLPFC decreased the proposer’s subjective inference of probability of rejection and the offer to the responder under incredible threat. Conversely, the same stimulation did not lead to a significant difference compared to the sham group in subjective probability and offer under credible threat. These results suggested that decision-making processes under the two types of threat during bargaining were associated with different neurocognitive substrates, because the punishment for non-compliance was uncertain under incredible threat, whereas it was certain under credible threat. We decreased activity in the rDLPFC, which is involved in decision-making processes related to bargaining under incredible threats, and observed significantly impacted behavior. The differential neurocognitive bases of subjective probability of rejection under incredible threat and credible threat resulted in different tDCS effects.

Unilateral Application of Cathodal tDCS Improves Visual Acuity in Amblyopia

Unilateral Application of Cathodal tDCS Improves Visual Acuity in Amblyopia

Uncertainty Modulates the Effect of Transcranial Stimulation over the Right Dorsolateral Prefrontal Cortex on Decision-making Under Threat

Threat is a strategy that can be used to impact decision-making processes in bargaining. Abundant evidence suggests that credible threat and incredible threat both influence the obeisance of others. However, it is not clear whether the decision-making processes under credible threat and incredible threat during bargaining involve differential neurocognitive mechanisms. Here, we employed cathodal transcranial direct current stimulation (tDCS) to deactivate the right dorsolateral prefrontal cortex (rDLPFC) to address this question while subjects allocated and reported the subjective probability of future rejection under incredible threat and credible threat. We found that application of cathodal tDCS over the rDLPFC decreased the proposer’s subjective inference of probability of rejection and the offer to the responder under incredible threat. Conversely, the same stimulation did not lead to a significant difference compared to the sham group in subjective probability and offer under credible threat. These results suggested that decision-making processes under the two types of threat during bargaining were associated with different neurocognitive substrates because the punishment for noncompliance was uncertain under incredible threat, whereas it was certain under credible threat. We decreased activity in the rDLPFC, which is involved in decision-making processes related to bargaining under incredible threats, and observed significantly impacted behavior. The differential neurocognitive bases of subjective probability of rejection under incredible threat and credible threat resulted in different tDCS effects.

Unilateral application of cathodal tDCS reduces transcallosal inhibition and improves visual acuity in amblyopic patients

Amblyopia is a neurodevelopmental disorder characterized by visual acuity and contrast sensitivity loss, refractory to pharmacological and optical treatments in adulthood. We studied the response of the visual cortex to transcranial Direct Current Stimulation (tDCS) applied over the primary visual area (V1) contralateral to the “lazy eye”. Visual acuity (logMAR) was assessed before (T0), immediately after (T1) and 60′ following the application of cathodal tDCS (2.0 mA, 20′). At each time point, Visual Evoked Potentials (VEPs) triggered by grating stimuli of different contrasts (K90%, K20%) were recorded in both hemispheres and compared to those obtained in healthy volunteers. Cathodal tDCS improved visual acuity (Holm–Sidak, p

Cathodal tDCS improves task performance in participants high in Coldheartedness.

It is investigated whether personality-related inter-individual differences modulate tDCS effects on response inhibition. Psychopathic personality traits have been associated with a reduced ability to inhibit prepotent responses and as such it is likely that these traits may modulate the effect tDCS has on response inhibition. This study represents the first investigation into the effect of psychopathic traits on tDCS effects in the context of response inhibition, and based on previous research, the psychopathic traits Blame Externalization and Coldheartedness were elected as potential candidates for modulating tDCS effects to right dorsolateral prefrontal cortex. Eighteen healthy participants underwent tDCS stimulation (sham, anodal, cathodal) before completing a response inhibition task, the parametric Go/No-go task. This task measures response inhibition under conditions of low and high cognitive load. TDCS stimulation was applied to F4 (international 10-20 system), corresponding to right dorsolateral prefrontal cortex, for 20min with an intensity of 1.5mA. Analysis of covariance was performed to assess how changes in response inhibition performance across difficulty level and stimulation condition were related to individual differences in psychopathy scores as measured via the Psychopathic Personality Inventory-Revised questionnaire. A positive relationship was found between greater scores on the Psychopathic Personality Inventory-Revised subscale of Coldheartedness and improvement in Go/No-go task performance after application of cathodal tDCS. This effect specifically related to the high load condition of the Go/No-go task. The psychopathic personality trait Coldheartedness may represent an imbalance of excitatory and inhibitory inputs to dlPFC. Improvement in functioning on inhibitory tasks after cathodal tDCS may be a result of a shift of excitatory glutamate levels to a more optimal level. The current results demonstrate the utility of tDCS as a tool to assess how differences in cortical responsivity are associated with specific personality traits. Additionally, this study represents the first investigation into the influence of psychopathic traits on tDCS effects on dlPFC, and we observed beneficial changes in response inhibition as a result of, especially, cathodal stimulation in participants scoring high on Coldheartedness.

Transcranial Direct Current Stimulation over the Medial Prefrontal Cortex and Left Primary Motor Cortex (mPFC-lPMC) Affects Subjective Beauty but Not Ugliness.

Neuroaesthetics has been searching for the neural bases of the subjective experience of beauty. It has been demonstrated that neural activities in the medial prefrontal cortex (mPFC) and the left primary motor cortex (lPMC) correlate with the subjective experience of beauty. Although beauty and ugliness seem to be semantically and conceptually opposite, it is still unknown whether these two evaluations represent extreme opposites in unitary or bivariate dimensions. In this study, we applied transcranial direct current stimulation (tDCS) to examine whether non-invasive brain stimulation modulates two types of esthetic evaluation; evaluating beauty and ugliness. Participants rated the subjective beauty and ugliness of abstract paintings before and after the application of tDCS. Application of cathodal tDCS over the mPFC with anode electrode over the lPMC, which induced temporal inhibition of neural excitability of the mPFC, led to a decrease in beauty ratings but not ugliness ratings. There were no changes in ratings of both beauty and ugliness when applying anodal tDCS or sham stimulation over the mPFC. Results from our experiment indicate that the mPFC and the lPMC have a causal role in generating the subjective experience of beauty, with beauty and ugliness evaluations constituting two distinct dimensions.

A critical role of temporoparietal junction in the integration of top‐down and bottom‐up attentional control

Information processing can be biased toward behaviorally relevant and salient stimuli by top-down (goal-directed) and bottom-up (stimulus-driven) attentional control processes respectively. However, the neural basis underlying the integration of these processes is not well understood. We employed functional magnetic resonance imaging (fMRI) and transcranial direct-current stimulation (tDCS) in humans to examine the brain mechanisms underlying the interaction between these two processes. We manipulated the cognitive load involved in top-down processing and stimulus surprise involved in bottom-up processing in a factorial design by combining a majority function task and an oddball paradigm. We found that high cognitive load and high surprise level were associated with prolonged reaction time compared to low cognitive load and low surprise level, with a synergistic interaction effect, which was accompanied by a greater deactivation of bilateral temporoparietal junction (TPJ). In addition, the TPJ displayed negative functional connectivity with right middle occipital gyrus, which is involved in bottom-up processing (modulated by the interaction effect), and the right frontal eye field (FEF), which is involved in top-down control. The enhanced negative functional connectivity between the TPJ and right FEF was accompanied by a larger behavioral interaction effect across subjects. Application of cathodal tDCS over the right TPJ eliminated the interaction effect. These results suggest that the TPJ plays a critical role in processing bottom-up information for top-down control of attention.

Medial prefrontal cortex reacts to unfairness if this damages the self: a tDCS study.

Neural correlates of unfairness perception depend on who is the target of the unfair treatment. These previous findings suggest that the activation of medial prefrontal cortex (MPFC) is related to unfairness perception only when the subject of the measurement is also the person affected by the unfair treatment. We aim at demonstrating the specificity of MPFC involvement using transcranial direct current stimulation (tDCS), a technique that induces cortical excitability changes in the targeted region. We use a modified version of the Ultimatum Game, in which responders play both for themselves (myself-MS condition) and on behalf of an unknown third-party (TP condition), where they respond to unfairness without being the target of it. We find that the application of cathodal tDCS over MPFC decreases the probability of rejecting unfair offers in MS, but not in TP; conversely, the same stimulation increases the probability of rejecting fair offers in TP, but not in MS. We confirm the hypothesis that MPFC is specifically related to processing unfairness when the self is involved, and discuss possible explanations for the opposite effect of the stimulation in TP.

P 71. The effects of cathodal transcranial direct current stimulation of the supplementary motor area on the function of anticipatory postural adjustments

Introduction Although the supplementary motor area (SMA) is thought to contribute to the generation of anticipatory postural adjustments (APAs), which act to stabilize supporting body segments prior to movement, its precise role remains unclear ( Jacobs et al., 2009 ). Non-invasive brain stimulation, such as transcranial direct current stimulation (tDCS), over the primary motor cortex (M1) has been shown to modulate cortical excitability, thereby influencing motor behaviour and learning. However, only a few studies have reported that application of tDCS over the SMA changes the excitability of the M1 ( Kirimoto et al., 2011 ) and motor learning process ( Vollmann et al., 2012 ). Objectives This study was performed to elucidate whether cathodal tDCS applied over the SMA modifies the function of APAs. Materials and Methods Cathodal tDCS and sham tDCS (2 mA) were applied over the SMA or left of the leg area of the M1 of 11 healthy subjects for 15 min. Subjects performed the task of self-paced rapid shoulder flexion before, immediately after, and 15 min after tDCS. Electromyographic (EMG) activity was recorded from the deltoid anterior (DEL_A), as the prime mover muscle, and biceps femoris (BF), as the postural muscle during tasks. Latency differences (ΔEMG onset) with the two types of stimuli were calculated by subtracting the EMG burst onset of the BF from that of the DEL_A. Results Fig. 1 shows the EMG waveforms obtained from a representative subject before, immediately after, and 15 min after cathodal tDCS over the SMA. Following cathodal tDCS over the SMA, the ΔEMG onset was significantly shortened compared to after sham tDCS, while tDCS over the M1 did not produce any significant effect. Conclusion These results suggest that the SMA may play a critical role in the generation of voluntary movement accompanied by APAs. As the application of cathodal tDCS over the SMA could modulate EMG activity, anodal tDCS over the SMA could have beneficial effects in patients with Parkinson’s disease who have deficient APAs [Latash et al., 1995] . Acknowledgement of funding sources This work was supported in part by a Grant-in-Aid for Scientific Research (C) No. 08042773 from the Japan Society for the Promotion of Science and a research grant from Niigata University of Health and Welfare.

P1-12. The effects of cathodal transcranial direct current stimulation of the supplementary motor area on the function of anticipatory postural adjustments

Objective: Although the supplementary motor area (SMA) is thought to contribute to the generation of anticipatory postural adjustments (APAs), which act to stabilize supporting body segments prior to movement, its precise role remains unclear. This study was performed to elucidate whether cathodal transcranial direct current stimulation (tDCS) applied over the SMA modifies the function of APAs. Method: Cathodal tDCS and sham tDCS were applied over the SMA or left of the leg area of the M1 of 11 healthy subjects for 15 min. Subjects performed the task of self-paced rapid shoulder flexion before, immediately after, and 15 min after tDCS. Electromyographic (EMG) activity was recorded from the deltoid anterior (DEL_A), as the prime mover muscle, and biceps femoris (BF), as the postural muscle during tasks. Results: Following cathodal tDCS over the SMA, the ΔEMG onset between DEL_A and BF was significantly shortened compared to after sham tDCS, while tDCS over the M1 did not produce any significant effect. Conclusions: These results suggest that the SMA may play a critical role in the generation of voluntary movement accompanied by APAs. Application of cathodal tDCS over the SMA could modulate the function and timing of these APAs.