Anodal-tDCS over the human right occipital cortex enhances the perception and memory of both faces and objects

Accurate face processing skills are pivotal for typical social cognition, and impairments in this ability characterise various clinical conditions (e.g., prosopagnosia). No study to date has investigated whether transcranial direct current stimulation (tDCS) can causally enhance face processing. In addition, the category- and the process- specificity of tDCS effects, as well as the role of the timing of neuromodulation with respect to the execution of cognitive tasks are still unknown. In this single-blind, sham-controlled study, we examined whether the administration of anodal-tDCS (a-tDCS) over the right occipital cortex of healthy volunteers (N = 64) enhances performance on perceptual and memory tasks involving both face and object stimuli. Neuromodulation was delivered in two conditions: online (a-tDCS during task execution) and offline (a-tDCS before task execution). The results demonstrate that offline atDCS enhances the perception and memory performance of both faces and objects. There was no effect of online a-tDCS on behaviour. Furthermore, the offline effect was site-specific since a-tDCS over the sensory-motor cortex did not lead to behavioural changes. Our results add relevant information about the breadth of cognitive processes and visual stimuli that can be modulated by tDCS, and about the design of effective neuromodulation protocols, which have implications for advancing theories in cognitive neuroscience and clinical applications

Modulation of internal model formation during force field-induced motor learning by anodal transcranial direct current stimulation of primary motor cortex

Human subjects can quickly adapt and maintain performance of arm reaching when experiencing novel physical environments such as robot-induced velocity-dependent forcefields.Using anodal transcranial direct current stimulation (tDCS) this study showed that the primary motor cortex may play a role in motor adaptation of this sort. Subjects performed arm reaching movement trials in three phases: in a null force field (baseline), in a velocity-dependent force field (adaptation; 25 N sm−1) and once again in a null force field (de-adaptation). Active or sham tDCS was directed to the motor cortex representation of biceps brachii muscle during the adaptation phase of the motor learning protocol. During the adaptation phase, the global error in arm reaching (summed error from an ideal trajectory) was similar in both tDCS conditions. However, active tDCS induced a significantly greater global reaching (overshoot) error during the early stage of de-adaptation compared to the sham tDCS condition. The overshoot error may be representative of the development of a greater predictivemovement to overcome the expected imposed force. An estimate of the predictive, initial movement trajectory (signed error in the first 150 ms of movement) was significantly augmented during the adaptation phase with active tDCS compared to sham tDCS. Furthermore, this increase was linearly related to the change of the overshoot summed error in the de-adaptation process. Together the results suggest that anodal tDCS augments the development of an internal model of the novel adapted movement and suggests that the primary motor cortex is involved in adaptation of reaching movements of healthy human subjects

Studying the Neurobiology of Social Interaction with Transcranial Direct Current Stimulation—The Example of Punishing Unfairness

Studying social behavior often requires the simultaneous interaction of many subjects. As yet, however, no painless, noninvasive brain stimulation tool existed that allowed the simultaneous affection of brain processes in many interacting subjects. Here we show that transcranial direct current stimulation (tDCS) can overcome these limits. We apply right prefrontal cathodal tDCS and show that subjects' propensity to punish unfair behavior is reduced significantl

Multiple Sessions of Transcranial Direct Current Stimulation (tDCS) Reduced Craving and Relapses for Alcohol Use: A Randomized Placebo-Controlled Trial in Alcohol Use Disorder

Background: Transcranial direct current stimulation (tDCS), a non-invasive brain stimulation technique, has been studied as an adjunctive therapeutic agent for alcohol dependence. In a previous study, we showed that five consecutive sessions of tDCS applied bilaterally over the dorsolateral prefrontal cortex (dlPFC) reduced relapse to the use of alcohol in alcohol use disorder (AUD) outpatients. However, no changes on craving scores were observed. In the present study, we investigated if an extended number of sessions of the same intervention would reduce craving and relapses for alcohol use in AUD inpatients.Methods: Thus, a randomized, double-blind, sham-controlled, clinical trial with parallel arms was conducted (https://clinicaltrials.gov/ct2/show/NCT02091284). AUD patients from two private and one public clinics for treatment of drug dependence were randomly allocated to two groups: real tDCS (5 × 7 cm2, 2 mA, for 20 min, cathodal over the left dlPFC, and anodal over the right dlPFC) and sham-tDCS. Real or sham-tDCS was applied once a day, every other day, in a total of 10 sessions. Craving was monitored by a 5-item obsessive compulsive drinking scale once a week (one time before, three times during and once after brain stimulation) over about 5 weeks.Results: Craving scores progressively decreased over five measurements in both groups but were significantly reduced only in the real tDCS group after treatment. Corrected Hedges' within-group (initial and final) effect sizes of craving scores were of 0.3 for the sham-tDCS and of 1.1 for the real tDCS group. Effect size was 3-fold larger in the real tDCS group. In addition, the between-group analysis on craving score difference was nearly significant, and the effect size was 0.58, in favor for a larger effect in the real tDCS group when compared to sham-tDCS. Furthermore, in a 3-months follow-up after intervention, 72.2% of sham-tDCS group relapsed to the alcohol use whereas 72.7% of tDCS group were abstinent.Conclusions: Multiple sessions of bilateral prefrontal tDCS were well tolerated with no significant adverse events. Thus, extended repetitive bilateral tDCS over the dlPFC is a promising adjunctive clinical tool that could be used to reduce alcohol craving and relapses and facilitate alcoholism cessation

Direct-current-dependent shift of theta-burst-induced plasticity in the human motor cortex

Animal studies using polarising currents have shown that induction of synaptic long-term potentiation (LTP) and long-term depression (LTD) by bursts of patterned stimulation is affected by the membrane potential of the postsynaptic neurone. The aim of the present experiments was to test whether it is possible to observe similar phenomena in humans with the aim of improving present protocols of inducing synaptic plasticity for therapeutic purposes. We tested whether the LTP/LTD-like after effects of transcranial theta-burst stimulation (TBS) of human motor cortex, an analogue of patterned electrical stimulation in animals, were affected by simultaneous transcranial direct-current stimulation (tDCS), a non-invasive method of polarising cortical neurones in humans. Nine healthy volunteers were investigated in a single-blind, balanced cross-over study; continuous TBS (cTBS) was used to introduce LTD-like after effects, whereas intermittent TBS (iTBS) produced LTP-like effects. Each pattern was coupled with concurrent application of tDCS (<200 s, anodal, cathodal, sham). Cathodal tDCS increased the response to iTBS and abolished the effects of cTBS. Anodal tDCS changed the effects of cTBS towards facilitation, but had no impact on iTBS. Cortical motor thresholds and intracortical inhibitory/facilitatory networks were not altered by any of the stimulation protocols. We conclude that the after effects of TBS can be modulated by concurrent tDCS. We hypothesise that tDCS changes the membrane potential of the apical dendrites of cortical pyramidal neurones and that this changes the response to patterned synaptic input evoked by TBS. The data show that it may be possible to enhance LTP-like plasticity after TBS in the human cortex

Effects of bilateral anodal transcranial direct current stimulation over the tongue primary motor cortex on cortical excitability of the tongue and tongue motor functions.

n/

Studying and modifying brain function with non-invasive brain stimulation

In the past three decades, our understanding of brain–behavior relationships has been significantly shaped by research using non-invasive brain stimulation (NIBS) techniques. These methods allow non-invasive and safe modulation of neural processes in the healthy brain, enabling researchers to directly study how experimentally altered neural activity causally affects behavior. This unique property of NIBS methods has, on the one hand, led to groundbreaking findings on the brain basis of various aspects of behavior and has raised interest in possible clinical and practical applications of these methods. On the other hand, it has also triggered increasingly critical debates about the properties and possible limitations of these methods. In this review, we discuss these issues, clarify the challenges associated with the use of currently available NIBS techniques for basic research and practical applications, and provide recommendations for studies using NIBS techniques to establish brain–behavior relationships

Indignation for moral violations suppresses the tongue motor cortex: preliminary TMS evidence

Abstract We commonly label moral violations in terms of 'disgust', yet it remains unclear whether metaphorical expressions linking disgust and morality are genuinely shared at the cognitive/neural level. Using transcranial magnetic stimulation (TMS), we provide new insights into this debate by measuring motor-evoked potentials (MEPs) from the tongue generated by TMS over the tongue primary motor area (tM1) in a small group of healthy participants presented with vignettes of moral transgressions and non-moral vignettes. We tested whether moral indignation, felt while evaluating moral vignettes, affected tM1 excitability. Vignettes exerted a variable influence on MEPs with no net effect of the moral category. However, in accordance with our recent study documenting reduced tM1 excitability during exposure to pictures of disgusting foods or facial expressions of distaste, we found that vignettes of highly disapproved moral violations reduced tM1 excitability. Moreover, tM1 excitability and moral indignation were linearly correlated: the higher the moral indignation, the lower the tM1 excitability. Respective changes in MEPs were not observed in a non-oral control muscle, suggesting a selective decrease of tM1 excitability. These preliminary findings provide neurophysiological evidence supporting the hypothesis that morality might have originated from the more primitive experience of oral distaste

Structural and physical properties of layered oxy-arsenides LnRuAsO (Ln = La, Nd, Sm, Gd)

Polycrystalline samples of LaRuAsO, NdRuAsO, SmRuAsO, and GdRuAsO have been synthesized and studied using powder x-ray diffraction, electrical transport, magnetization, and heat capacity measurements. Variations in structural properties across the series reveal a trend toward more ideal tetrahedral coordination around Ru as the size of the rare earth element is reduced. The lattice parameters of these Ru compounds show a more anisotropic response to variation in Ln than their Fe analogues, and significant anisotropy in thermal expansion is also observed. Transport measurements show metallic behavior, and carrier concentrations near 10^21 - 10^22 electrons per cm^3 are inferred from simple analysis of Hall effect measurements. Anomalies in resistivity, magnetization, and heat capacity indicate antiferromagnetic ordering of rare earth moments at 5 K for GdRuAsO, 4.5 K for SmRuAsO, and <2 K for NdRuAsO. Magnetization measurements on LaRuAsO show no evidence of a magnetic moment on Ru. Observed behaviors are compared to those reported for similar Fe and Ru compounds