Neurocognitive mechanisms behind emotional attention: Inverse effects of anodal tDCS over the left and right DLPFC on gaze disengagement from emotional faces

Transcranial Direct Current Stimulation (tDCS) over the left dorsolateral prefrontal cortex reduced attentional bias toward natural emotional sounds

Previous research has indicated that the left dorsolateral prefrontal cortex (DLPFC) exerts an influence on attentional bias toward visual emotional information. However, it remains unclear whether the left DLPFC also play an important role in attentional bias toward natural emotional sounds. The current research employed the emotional spatial cueing paradigm, incorporating natural emotional sounds of considerable ecological validity as auditory cues. Additionally, high-definition transcranial direct current stimulation (HD-tDCS) was utilized to examine the impact of left dorsolateral prefrontal cortex (DLPFC) on attentional bias and its subcomponents, namely attentional engagement and attentional disengagement. The results showed that (1) compared to sham condition, anodal HD-tDCS over the left DLPFC reduced the attentional bias toward positive and negative sounds; (2) anodal HD-tDCS over the left DLPFC reduced the attentional engagement toward positive and negative sounds, whereas it did not affect attentional disengagement away from natural emotional sounds. Taken together, the present study has shown that left DLPFC, which was closely related with the top-down attention regulatory function, plays an important role in auditory emotional attentional bias.

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) (1.5 mA, 20 min) 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.

Targeting the left DLPFC and right VLPFC in unmarried romantic relationship breakup (love trauma syndrome) with intensified electrical stimulation: A randomized, single-blind, parallel-group, sham-controlled study

BACKGROUND

Ending a romantic relationship is one of the most painful losses an adult experience. Neuroimaging studies suggest that there is a neuropsychological link between breakup experiences and bereaved individuals, and that specific prefrontal regions are involved. The aim of this study was to determine whether enhancement of left DLPFC and right VLPFC activity with a novel intensified anodal transcranial direct current stimulation protocol reduces core symptoms of love trauma syndrome (LTS) and improves treatment-related variables.

METHODS

In this randomized, sham-controlled, single-blind parallel trial, we assessed the efficacy of an intensified anodal stimulation protocol (20 min, twice-daily sessions with 20 min intervals, 5 consecutive days) with two montages (left DLPFC vs right VLPFC) to reduce love trauma symptoms. 36 participants with love trauma syndrome were randomized in three tDCS condition (left DLPFC, right VLPFC, sham stimulation). LTS symptoms, treatment-related outcome variables (depressive state, anxiety, emotion regulation, positive and negative affect), and cognitive functions were assessed before, right after, and one month after intervention.

RESULTS

Both DLPFC and VLPFC protocols significantly reduced LTS symptoms, and improved depressive state and anxiety after the intervention, as compared to the sham group. The improving effect of the DLPFC protocol on love trauma syndrome was significantly larger than that of the VLPFC protocol. For emotion regulation and positive and negative affect, improved regulation of emotions and positive affect and reduced negative affect were revealed after intervention in the two real stimulation conditions compared to the sham. For cognitive functions, no significant difference was observed between the groups, but again a positive effect of intervention within groups in the real stimulation conditions (DLPFC and VLPFC) was found for most components of the cognitive tasks.

CONCLUSIONS

Enhancement of left DLPFC and right VLPFC activity with intensified stimulation improves LTS symptoms and treatment-related variables. For LTS symptoms, DLPFC stimulation was more efficient than VLPFC stimulation., For the other variables, no significant difference was observed between these two stimulation groups. These promising results require replication in larger trials.

The impact of transcranial direct current stimulation on attention bias modification in children with ADHD

Individuals with attention deficit-hyperactivity disorder (ADHD) struggle with the interaction of attention and emotion. The ventromedial prefrontal cortex (vmPFC) and dorsolateral prefrontal cortex (dlPFC) are assumed to be involved in this interaction. In the present study, we aimed to explore the effect of stimulation applied over the dlPFC and vmPFC on attention bias in individuals with ADHD. Twenty-three children with ADHD performed the emotional Stroop and dot probe tasks during transcranial direct current stimulation (tDCS) in 3 conditions: anodal dlPFC (F3)/cathodal vmPFC (Fp2), anodal vmPFC (Fp2)/cathodal dlPFC (F3), and sham stimulation. Findings suggest reduction of attention bias in both real conditions based on emotional Stroop task and not dot probe task. These results were independent of emotional states. The dlPFC and vmPFC are involved in attention bias in ADHD. tDCS can be used for attention bias modification in children with ADHD.

Immediate and Differential Response to Emotional Stimuli Associated With Transcranial Direct Current Stimulation for Depression: A Visual-Search Task Pilot Study

OBJECTIVES

When administered in repeated daily doses, transcranial direct current stimulation (tDCS) directed to the prefrontal cortex has cumulative efficacy for the treatment of depression. Depression can be marked by altered processing of emotionally salient information. An acute marker of response to tDCS may be measured as an immediate change in emotional information processing. Using an easily administered web-based task, we tested immediate changes in emotional information processing in acute response to tDCS in participants with and without depression.

MATERIALS AND METHODS

We enrolled n = 21 women with mild-to-moderate depression and n = 20 controls without depression to complete a web-based visual search task before and after 30 minutes of tDCS directed to the prefrontal cortex. The timed task required participants to identify a target face among arrays showing sad, neutral, or mixed (distractor) expressions.

RESULTS

At baseline, as predicted, the participants with depression differed from those without in emotional processing speed (mean z score difference -0.66 ± 0.27, p = 0.022) and accuracy in identifying sad stimuli (error rate: 4.4% vs 1.8%, p = 0.039). In response to tDCS, the participants with depression became significantly faster on the distractor condition (pre- vs post-tDCS z scores: -0.45 ± 0.65 vs -0.85 ± 0.65, p = 0.009), suggesting a specific reduction in bias toward negative emotional information. In response to tDCS, the depressed group also had significant improvements in self-reported mood (increased happy, decreased sad and anxious mood).

CONCLUSIONS

Participants with depression vs those without were differentiated by their performance of the visual search task at baseline and in response to tDCS. Given that measurable effects on depression scales may require weeks of tDCS treatments, acute change in emotional information processing can serve as an easily obtainable marker of depression and its response to tDCS.

CLINICAL TRIAL REGISTRATION

The Clinicaltrials.gov registration number for the study is NCT05188248.

Transcranial random noise stimulation (tRNS) improves hot and cold executive functions in children with attention deficit-hyperactivity disorder (ADHD)

Children with attention deficit-hyperactivity disorder (ADHD) have impaired hot and cold executive functions, which is thought to be related to impaired ventromedial and dorsolateral prefrontal cortex (vmPFC and dlPFC) functions. The present study aimed to assess the impact concurrent stimulation of dlPFC and vmPFC through transcranial random noise stimulation (tRNS), a non-invasive brain stimulation tool which enhances cortical excitability via application of alternating sinusoidal currents with random frequencies and amplitudes over the respective target regions on hot and cold executive functions. Eighteen children with ADHD received real and sham tRNS over the left dlPFC and the right vmPFC in two sessions with one week interval. The participants performed Circle Tracing, Go/No-Go, Wisconsin Card Sorting, and Balloon Analogue Risk Tasks during stimulation in each session. The results showed improved ongoing inhibition, prepotent inhibition, working memory, and decision making, but not set-shifting performance, during real, as compared to sham stimulation. This indicates that simultaneous stimulation of the dlPFC and the vmPFC improves hot and cold executive functions in children with ADHD.

Shared Minds, Shared Feedback: tracing the influence of parental feedback on shared neural patterns

Parental feedback affects children in multiple ways. However, little is known about how children, family, and feedback types affect parental feedback neural mechanisms. The current study used functional near-infrared spectroscopy-based hyperscanning to observe 47 mother-daughter pairs's (mean age of mothers: 35.95 ± 3.99 yr old; mean age of daughters: 6.97 ± 0.75 yr old) brain synchronization in a jigsaw game under various conditions. Between parental negative feedback and praise conditions, mother-daughter brain in supramarginal gyrus, left dorsolateral prefrontal cortex, right inferior frontal gyrus, and right primary somatic (S1) differed. When criticized, conformity family-communication-patterned families had much worse brain synchronization in S1, left dorsolateral prefrontal cortex, and right Wernicke's region than conversational families. Resilient children had better mother-child supramarginal gyrus synchronicity under negative feedback. This study supports the importance of studying children's neurological development in nurturing environments to assess their psychological development.

Trait-related neural basis of attentional bias to emotions: a tDCS study

Negative emotional stimuli can strongly bias attention, particularly in individuals with high levels of dispositional negative affect (NA). The current study investigated whether the prefrontal cortex (PFC), a brain region involved in the top-down regulation of emotional processing, plays a different role in controlling attention to emotions, depending on the individual NA. Sham and anodal transcranial direct current stimulation (tDCS) was delivered over the right or left PFC while assessing attentional bias (AB) to emotions (happy, angry, sad faces) in individuals with higher and lower trait NA. When tDCS was inactive (sham), individuals with higher trait NA showed AB toward angry and away from sad faces, while individuals with lower trait NA presented with no AB. Right anodal-tDCS abolished the AB toward angry faces and induced an AB toward sad faces in individuals with higher trait NA, while no effect was found in individuals with lower trait NA. Left anodal-tDCS abolished any AB in individuals with higher trait NA and induced an AB away from happy faces in individuals with lower trait NA. These findings confirm a critical role of trait NA in AB to emotions and demonstrate a different involvement of PFC in emotional processing based on dispositional affect.

The effects of left prefrontal stimulation on selective attention and emotional reactivity for positive and negative information

Transcranial direct current stimulation targeting lateral prefrontal areas may attenuate attentional vigilance for negative content and reduce emotional reactivity. However, little research to date has examined how such stimulation may affect attention towards and emotional reactivity to positive emotional content. The aim of this study was to examine whether anodal tDCS targeting the left dorsolateral prefrontal cortex would affect attentional bias towards either or both negative and positive content, and similarly, how it would impact emotional reactivity to negative and positive emotional content among healthy individuals. Unselected participants (N = 101) were recruited (Mage = 22.57, SD = 5.60; 66.33% female) and allocated to either an active or sham tDCS condition. Attentional bias was measured using an eye-tracking task involving negative-neutral and positive-neutral image pairs, followed by an emotional reactivity assessment task involving negative and positive video content (self-report and heart rate variability). Results showed no evidence that tDCS influenced attentional patterns towards either positive or negative information, nor was there evidence that tDCS influenced self-reported anxious mood or physiological arousal. However, participants in the active tDCS condition reported higher positive mood in response to both the positive and negative videos compared to those in the sham condition and also higher arousal in response to positive content and lower arousal in response to negative content, with those in the sham tDCS condition showing the reverse pattern of effects. As such, tDCS effects on emotional reactivity to positive and negative content were restricted to self-report measures.

The contextual goal dependent attentional flexibility (CoGoDAF) framework: A new approach to attention bias in depression

Successful adaptation to the environment requires attentional prioritization of emotional information relevant to the current situational demands. Accordingly, the presence of an attention bias (AB) for both positive and negative information may allow preferential processing of stimuli in line with the current situational goals. However, AB for negative information sometimes becomes maladaptive, being antithetical to the current adaptive needs and goals of an individual, such as in the case of affective disorders such as depression. Although difficulties in flexible shifting between emotional stimuli in depression have increasingly become a topic of discussion in the field, an integrative approach towards biased versus flexible emotional attentional processes remains absent. In the present paper, we advance a novel and integrative view of conceptualizing potentially aberrant affective attention patterns in depression as a function of the current contextual features. We propose that flexible emotional attention takes place as a result of attention prioritization towards goal-relevant emotional stimuli depending upon the current context of the individual. Specifically, the roles of context, distal and proximal goals, and approach and avoidance motivation processes are considered in a unified manner. The empirical, clinical, and interventional implications of this integrative framework provide a roadmap for future psychological and neurobiological experimental and translational research.

The Analgesic Effect of Transcranial Direct Current Stimulation in Fibromyalgia: A Systematic Review, Meta-Analysis, and Meta-Regression of Potential Influencers of Clinical Effect

BACKGROUND

There is tentative evidence to support the analgesic effect of transcranial direct current stimulation (tDCS) in fibromyalgia (FM), with large variability in the effect size (ES) encountered in different clinical trials. Understanding the source of the variability and exploring how it relates to the clinical results could characterize effective neuromodulation protocols and ultimately guide care in FM pain. The primary objective of this study was to determine the effect of tDCS in FM pain as compared with sham tDCS. The secondary objective was to explore the relationship of methodology, population, and intervention factors and the analgesic effect of tDCS in FM.

MATERIALS AND METHODS

For the primary objective, a systematic review was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Randomized clinical trials (RCTs) investigating tDCS as an intervention for FM pain were searched in MEDLINE, Embase, and the Web Of Science. Studies were excluded if they used cross-over designs or if they did not use tDCS as an intervention for pain or did not measure clinical pain. Analysis for the main outcome was performed using a random-effects model. Risk of bias and evidence certainty were assessed for all studies using Cochrane Risk of Bias and Grading of Recommendations Assessment, Development, and Evaluation tools. For the secondary objective, a meta-regression was conducted to explore methodology, population, and intervention factors potentially related to the ES.

RESULTS

Sixteen RCTs were included. Six studies presented a high risk of bias. Significant reduction in pain scores were found for FM (standardized mean difference = 1.22, 95% CI = 0.80-1.65, p < 0.001). Subgroup analysis considering tDCS as a neural target revealed no differences between common neural sites. Meta-regression revealed that the duration of the tDCS protocol in weeks was the only factor associated with the ES, in which protocols that lasted four weeks or longer reported larger ES than shorter protocols.

CONCLUSIONS

Results suggest an analgesic effect of tDCS in FM. tDCS protocols that last four weeks or more may be associated with larger ESs. Definite conclusions are inadequate given the large heterogeneity and limited quality of evidence of the included studies.

How processing emotion affects language control in bilinguals

Research has shown that several variables affect language control among bilingual speakers but the effect of affective processing remains unexplored. Chinese-English bilinguals participated in a novel prime-target language switching experiment in which they first judged the affective valence (i.e., positive or negative) of auditorily presented words and then named pictures with neutral emotional valence in either the same (non-switch trial) or different language (switch trial). Brain activity was monitored using functional magnetic resonance imaging (fMRI). The behavioral performance showed that the typical switch cost (i.e., the calculated difference between switch and non-switch trials) emerged after processing positive words but not after negative words. Brain imaging demonstrated that processing negative words immediately before non-switch picturing naming trials (but not for switch trials) increased activation in brain areas associated with domain-general cognitive control. The opposite patterns were found after processing positive words. These findings suggest that an (emotional) negative priming effect is induced by spontaneous exposure to negative words and that these priming effects may be triggered by reactive emotional processing and that they may interact with higher level cognitive functions.

Gray matter reduction is associated with cognitive dysfunction in depressed patients comorbid with subclinical hypothyroidism

Introduction

To explore the association between regional gray matter volume (GMV) and cognitive impairments and ascertain whether the regional brain alterations related to cognitive impairments occur in major depressive disorder (MDD) patients with comorbid subclinical hypothyroidism (SHypo).

Methods

We enrolled 32 MDD patients, 32 MDD patients with comorbid SHypo, and 32 normal controls and subjected them to thyroid function tests, neurocognitive tests, and magnetic resonance imaging (MRI). Using voxel-based morphometry (VBM) analysis, we examined the pattern of gray matter (GM) in these participants. We also used ANOVA to detect group differences and partial correlation to explore the potential association between GMV alterations and cognitive tests in comorbid patients.

Results

The comorbid patients exhibited significantly smaller GMV in the right middle frontal gyrus (MFG) than the non-comorbid group. Furthermore, the partial correlation analysis showed that GMV of the right MFG was associated with poor executive function (EF) performance in comorbid patients.

Conclusion

These findings provide valuable insight into the relationship between the alteration of GMV and cognitive dysfunction of MDD patients with comorbid SHypo.

Cortical activation predicts posttraumatic improvement in youth treated with TF-CBT or CCT

BACKGROUND

Identifying neural activation patterns that predict youths' treatment response may aid in the development of imaging-based assessment of emotion dysregulation following trauma and foster tailored intervention. Changes in cortical hemodynamic activity measured with functional near-infrared spectroscopy (fNIRS) may provide a time and cost-effective option for such work. We examined youths' PTSD symptom change following treatment and tested if previously identified activation patterns would predict treatment response.

METHODS

Youth (N = 73, mean age = 12.97, SD = 3.09 years) were randomly assigned to trauma-focused cognitive behavioral therapy (TF-CBT), cue-centered therapy (CCT), or treatment as usual (TAU). Parents and youth reported on youth's PTSD symptoms at pre-intervention, post-intervention, and follow-up. Neuroimaging data (N = 31) assessed at pre-intervention were obtained while youth engaged in an emotion expression task. Treatment response slopes were calculated for youth's PTSD symptoms.

RESULTS

Overall, PTSD symptoms decreased from pre-intervention through follow-up across conditions, with some evidence of relative benefit of TF-CBT and CCT over TAU but significant individual variation in treatment response. Cortical activation patterns were correlated with PTSD symptom improvement slopes (r = 0.53). In particular, cortical responses to fearful and neutral facial stimuli in six fNIRS channels in the bilateral dlPFC were important predictors of PTSD symptom improvement.

CONCLUSIONS

The use of fNIRS provides a method of monitoring and assessing cortical activation patterns in a relatively inexpensive and portable manner. Associations between functional activation and youths' PTSD symptoms improvement may be a promising avenue for understanding emotion dysregulation in clinical populations.

A systematic review of transcranial direct current stimulation on eye movements and associated psychological function

The last decades have seen a rise in the use of transcranial direct current stimulation (tDCS) approaches to modulate brain activity and associated behavior. Concurrently, eye tracking (ET) technology has improved to allow more precise quantitative measurement of gaze behavior, offering a window into the mechanisms of vision and cognition. When combined, tDCS and ET provide a powerful system to probe brain function and measure the impact on visual function, leading to an increasing number of studies that utilize these techniques together. The current pre-registered, systematic review seeks to describe the literature that integrates these approaches with the goal of changing brain activity with tDCS and measuring associated changes in eye movements with ET. The literature search identified 26 articles that combined ET and tDCS in a probe-and-measure model and are systematically reviewed here. All studies implemented controlled interventional designs to address topics related to oculomotor control, cognitive processing, emotion regulation, or cravings in healthy volunteers and patient populations. Across these studies, active stimulation typically led to changes in the number, duration, and timing of fixations compared to control stimulation. Notably, half the studies addressed emotion regulation, each showing hypothesized effects of tDCS on ET metrics, while tDCS targeting the frontal cortex was widely used and also generally produced expected modulation of ET. This review reveals promising evidence of the impact of tDCS on eye movements and associated psychological function, offering a framework for effective designs with recommendations for future studies.

Functional connectivity associated with improvement in emotion management after cognitive enhancement therapy in early-course schizophrenia

BACKGROUND

The ability to manage emotions is an important social-cognitive domain impaired in schizophrenia and linked to functional outcome. The goal of our study was to examine the impact of cognitive enhancement therapy (CET) on the ability to manage emotions and brain functional connectivity in early-course schizophrenia.

METHODS

Participants were randomly assigned to CET (n = 55) or an enriched supportive therapy (EST) control group (n = 45). The resting-state functional magnetic resonance imaging scans and measures of emotion management performances were collected at baseline, 9, and 18 months follow-up. The final sample consisted of 37 CET and 25 EST participants, including 19 CET and 12 EST participants with imaging data. Linear mixed-effects models investigated the impact of treatment on emotion management and functional connectivity from the amygdala to ventrolateral and dorsolateral prefrontal cortex (dlPFC).

RESULTS

The CET group showed significant improvement over time in emotion management compared to EST. Neither functional connectivity changes nor main group differences were observed following treatment. However, a significant between-group interaction showed that improved emotion management ability was associated with increased functional connectivity between the left amygdala and the left dlPFC in the CET group exclusively.

CONCLUSION

Our results replicate the previous work demonstrating that CET is effective at improving some aspects of social cognition in schizophrenia. We found evidence that improvement in emotion management may be associated with a change in amygdala-dlPFC connectivity. This fronto-limbic circuit may provide a mechanistic link between the biology of emotion management processes that can be enhanced in individuals with schizophrenia.

Transcranial direct current stimulation does not improve clinical and neurophysiological outcomes in panic disorder: A randomized sham-controlled trial

AIM

Emerging evidence suggests that transcranial direct current stimulation (tDCS) has anxiolytic effects and may enhance emotional processing of threat and reduce threat-related attentional bias. Panic disorder (PD) is considered to be a fear network disorder along with prefrontal activity alterations. We aim to assess the effect of tDCS on clinical and physiological parameters in PD for the first time.

METHODS

In this triple-blind randomized sham-controlled pilot study, 30 individuals with PD were allocated into active and sham groups to receive 10 sessions of tDCS targeting the dorsolateral prefrontal cortex bilaterally at 2 mA for 20-min duration over 2 weeks. The clinical severity, threat-related attentional bias, interoceptive accuracy, and emotional recognition were assessed before, immediately after, and 1 month after tDCS.

RESULTS

Active tDCS, in comparison to sham, did not elicit more favorable clinical and neuropsychological/physiological outcomes in PD.

CONCLUSION

The present study provides the first clinical and neurobehavioral results of prefrontal tDCS in PD and indicates that prefrontal tDCS was not superior to sham in PD.

Transcranial Direct Current Stimulation Over the Left Dorsolateral Prefrontal Cortex Reduced Attention Bias Toward Negative Facial Expression: A Pilot Study in Healthy Subjects

Research in the cognitive neuroscience field has shown that individuals with a stronger attention bias for negative information had higher depression risk, which may be the underlying pathogenesis of depression. This dysfunction of affect-biased attention also represents a decline in emotion regulation ability. Clinical studies have suggested that transcranial direct current stimulation (tDCS) treatment can improve the symptoms of depression, yet the neural mechanism behind this improvement is still veiled. This study aims to investigate the effects of tDCS on affect-biased attention. A sample of healthy participants received 20 min active (n = 22) or sham tDCS (n = 19) over the left dorsolateral prefrontal cortex (DLPFC) for 7 consecutive days. Electroencephalographic (EEG) signals were recorded while performing the rest task and emotional oddball task. The oddball task required response to pictures of the target (positive or negative) emotional facial stimuli and neglecting distracter (negative or positive) or standard (neutral) stimuli. Welch power spectrum estimation algorithm was applied to calculate frontal alpha asymmetry (FAA) in the rest task, and the overlapping averaging method was used to extract event-related potentials (ERP) components in the oddball task. Compared to sham tDCS, active tDCS caused an obvious increment in FAA in connection with emotion regulation (p < 0.05). Also, participants in the active tDCS group show greater P3 amplitudes following positive targets (p < 0.05) and greater N2 amplitudes following negative distracters (p < 0.05), reflecting emotion-related attention biases. These results offer valuable insights into the relationship between affect-biased attention and the effects of tDCS, which may be of assistance in exploring the neuropathological mechanism of depression and anxiety and new treatment strategies for tDCS.

The role of the dorsolateral and ventromedial prefrontal cortex in emotion regulation in females with major depressive disorder (MDD): A tDCS study

BACKGROUND

Individuals with major depressive disorder (MDD) have deficits in emotion regulation, which plays a putative role in psychopathology. The ventromedial prefrontal cortex (vmPFC) and dorsolateral prefrontal cortex (dlPFC) are assumed to be involved in respective processes. In the present study, we aimed to explore the effect of stimulation over the dlPFC and vmPFC on emotion regulation in female with MDD.

MATERIAL AND METHODS

Twenty women with MDD performed the Emotional Stroop, Emotional Go/No-Go, and Emotional 1-Back tasks during transcranial direct current stimulation (tDCS) in three separate sessions with the following electrode montages: anodal dlPFC (F3)/cathodal vmPFC (Fp2), anodal vmPFC (Fp2)/cathodal dlPFC (F3), and sham stimulation.

RESULTS

Independent of the valence of the respective stimuli, accuracy and speed of interference control, accuracy of pre-potent inhibition, and accuracy, but not speed, of working memory performance improved during anodal left dlPFC/cathodal right vmPFC stimulation. Independent of stimulation conditions, interference control was reduced for sad faces, as compared to happy and neutral faces, and working memory performance was faster for happy than for neutral and sad faces. For the impact of stimulation on specific emotional qualities, anodal left dlPFC/cathodal right vmPFC, compared to sham stimulation, led to improved interference control of sad and neutral faces in the emotional Stroop task, as shown by faster reaction times. Furthermore, in that task accuracy with respect to neutral and happy face conditions was higher during both real stimulation conditions, as compared to sham stimulation.

CONCLUSION

The dlPFC is involved in emotion regulation in MDD. Emotional valence is moreover relevant for the effect of stimulation over this area on interference control in MDD.

In vivo imaging of dopamine D1 receptor and activated microglia in attention-deficit/hyperactivity disorder: a positron emission tomography study

Alterations in the cortical dopamine system and microglial activation have been implicated in the pathophysiology of attention-deficit/hyperactivity disorder (ADHD), one of neurodevelopmental disorders that can be conventionally treated with a dopamine enhancer (methylphenidate) albeit unsatisfactorily. Here, we investigated the contributions of the dopamine D1 receptor (D1R) and activated microglia and their interactions to the clinical severities in ADHD individuals using positron emission tomography (PET). Twenty-four psychotropic-naïve ADHD individuals and 24 age- and sex-matched typically developing (TD) subjects underwent PET measurements with [¹¹C]SCH23390 for the D1R and [¹¹C](R)PK11195 for activated microglia as well as assessments of clinical symptoms and cognitive functions. The ADHD individuals showed decreased D1R in the anterior cingulate cortex (ACC) and increased activated microglia in the dorsolateral prefrontal cortex (DLPFC) and orbitofrontal cortex (OFC) compared with the TD subjects. The decreased D1R in the ACC was associated with severe hyperactivity in the participants with ADHD. Microglial activation in the DLPFC were associated with deficits in processing speed and attentional ability, and that in the OFC was correlated with lower processing speed in the ADHD individuals. Furthermore, positive correlations between the D1R and activated microglia in both the DLPFC and the OFC were found to be significantly specific to the ADHD group and not to the TD group. The current findings suggest that microglial activation and the D1R reduction as well as their aberrant interactions underpin the neurophysiological mechanism of ADHD and indicate these biomolecular changes as a novel therapeutic target.

Prefrontal tDCS Attenuates Self-Referential Attentional Deployment: A Mechanism Underlying Adaptive Emotional Reactivity to Social-Evaluative Threat

Social-evaluative threat (SET) - a situation in which one could be negatively evaluated by others - elicits profound (psycho)physiological reactivity which, if chronically present and not adaptively regulated, has deleterious effects on mental and physical health. Decreased self-awareness and increased other-awareness are understood to be an adaptive response to SET. Attentional deployment - the process of selectively attending to certain aspects of emotional stimuli to modulate emotional reactivity - is supported by fronto-parietal and fronto-limbic networks, with the dorsolateral prefrontal cortex being a central hub. The primary aim of the current study was to investigate the effects of active (versus sham) prefrontal transcranial direct current stimulation (tDCS) on self and other-attentional deployment during the exposure to a SET context. Seventy-four female participants received active or sham tDCS and were subsequently exposed to a rigged social feedback paradigm. In this paradigm a series of social evaluations were presented together with a photograph of the supposed evaluator and a self- photograph of the participant, while gaze behavior (time to first fixation, total fixation time) and skin conductance responses (SCRs; a marker of emotional reactivity) were measured. For half of the evaluations, participants could anticipate the valence (negative or positive) of the evaluation a priori. Analyses showed that participants receiving active tDCS were (a) slower to fixate on their self-photograph, (b) spent less time fixating on their self-photograph, and (c) spent more time fixating on the evaluator photograph. During unanticipated evaluations, active tDCS was associated with less time spent fixating on the evaluation. Furthermore, among those receiving active tDCS, SCRs were attenuated as a function of slower times to fixate on the self-photograph. Taken together, these results suggest that in a context of SET, prefrontal tDCS decreases self-attention while increasing other-attention, and that attenuated self-referential attention specifically may be a neurocognitive mechanism through which tDCS reduces emotional reactivity. Moreover, the results suggest that tDCS reduces vigilance toward stimuli that possibly convey threatening information, corroborating past research in this area.

Pre-SMA activation and the perception of contagiousness and authenticity in laughter sounds

Functional near-infrared spectroscopy and behavioural methods were used to examine the neural basis of the behavioural contagion and authenticity of laughter. We demonstrate that the processing of laughter sounds recruits networks previously shown to be related to empathy and auditory-motor mirror networks. Additionally, we found that the differences in the levels of activation in response to volitional and spontaneous laughter could predict an individual's perception of how contagious they found the laughter to be.

Combined effects of tDCS over the left DLPFC and gaze-contingent training on attention mechanisms of emotion regulation in low-resilient individuals

Low resilience is characterized by impairments in attention and emotion regulation mechanisms that depend on prefrontal cortical activity. The aim of this study was to test whether transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex (DLPFC) can augment the effectiveness of a new computerized mouse-based (gaze)contingent training (MCAT) to improve attention and emotion regulation processes (improved reappraisal, reduced rumination) in individuals reporting low resilience levels. The study used a full-factorial between-subject design combining active and sham MCAT and tDCS interventions. One hundred participants reporting low resilience levels were randomly assigned to receive either a single session of: tDCS with sham MCAT treatment (tDCS group), MCAT with sham tDCS (MCAT group), a combination of tDCS and MCAT (combined group), or sham tDCS and sham MCAT (control group). Transfer to attention regulation, reappraisal success, and state rumination was evaluated using an eye-tracking disengagement task and an emotion regulation paradigm, respectively. MCAT, either alone or combined with tDCS, resulted in improved attention regulation. Furthermore, the group receiving combined MCAT and tDCS also showed some evidence of increased reappraisal ability and reduced rumination. MCAT in combination with left DLPFC neuromodulation has potential to maximize transfer to emotion regulation capacities and to promote resilience.

Prefrontal tDCS attenuates counterfactual thinking in female individuals prone to self-critical rumination

The tendency to ruminate (i.e., repetitive negative self-referential thoughts that perpetuate depressive mood) is associated with (a) an elevated propensity to maladaptively experience counterfactual thinking (CFT) and regret, and (b) hypo-activity of the left dorsolateral prefrontal cortex (DLPFC). The goal of this study was to investigate whether anodal transcranial direct current stimulation (tDCS) over the left DLPFC, in function of self-critical rumination tendencies, momentarily reduces counterfactual thinking and regret (assessed via self-report and psychophysiological indices). Eighty healthy participants with different levels of self-critical rumination received either anodal or sham tDCS while performing a decision making task in which they were repeatedly confronted with optimal, suboptimal, and non-optimal choice outcomes. The results showed that among rumination-prone individuals, anodal (versus sham) tDCS was associated with decreased CFT and attenuated psychophysiological reactivity to the differential choice outcomes. Conversely, among low rumination-prone individuals, anodal (versus sham) tDCS was associated with increased CFT and regret, but in absence of any effects on psychophysiological reactivity. Potential working mechanisms for these differential tDCS effects are discussed. Taken together, these results provide initial converging evidence for the adaptive effects of left prefrontal tDCS on CFT and regret to personal choice outcomes among individuals prone to engage in self-critical rumination.

Challenging control over emotions in borderline personality disorder - a tDCS study

BACKGROUND

Deficient cognitive control (CC) over emotional distraction is a central characteristic of borderline personality disorder (BPD). Reduced activation of the left dorsolateral prefrontal cortex (dlPFC) has been linked to this deficit. This study investigates whether it is possible to ameliorate CC deficits via anodal tDCS over the left dlPFC in BPD. Furthermore, we investigate whether the extent of CC impairment influences how well one responds to tDCS.

METHODS

The effect of a single-session tDCS (1 mA for 20 min, reference electrode on the contralateral mastoid bone) to the left dlPFC (F3) on the CC of patients with BPD (N = 20) and healthy control participants (HCs, N = 20) was examined in a double-blinded, balanced randomized, sham-controlled crossover trial. A delayed response working memory task with negative, neutral and positive pictures presented during the delay period was conducted to assess CC. Stimulation was applied simultaneously with the task.

RESULTS

Negative pictures caused prolonged response times as compared to a control condition in patients with BPD and HCs. Anodal tDCS to the left dlPFC did not significantly reduce this interference effect in the overall sample. Further analyses showed, however, that participants with impaired CC profited the most from anodal tDCS. In the subgroup of participants who actually showed an interference effect we found the expected significant amelioration of CC under tDCS.

CONCLUSIONS

The present study demonstrates that anodal tDCS applied to the left dlPFC improves deficient CC. Thereby, base-level performance moderates tDCS effects. Hence, tDCS might be suitable to support behavioral trainings to enhance CC specifically in people whose impairments in CC are comparably high.

fMRI evidence reveals emotional biases in bilingual decision making

Research indicates that the foreign language effect on decision making can be partially explained by a reduction in emotional response in the second language. In this fMRI study, we aimed at elucidating the neural mechanisms underpinning the interaction between language and emotion in decision making. Across multiple trials, Chinese-English bilinguals were asked to decide whether to gamble in a Gambling task, and received feedbacks either in L1 (Chinese) or in L2 (English). If they gambled, feedbacks were either positively or negatively valenced words; if they did not gamble, feedback was the word 'safe'. We assessed how emotionally valenced words were processed in the two languages, and how this processing influenced subsequent decision making. Overall, we found evidence that in L2 context, but not in L1 context, loss aversion was mediated by the dorsolateral prefrontal cortex (dlPFC) which also showed strong functional connectivity with the visual cortex, suggesting an avoidance mechanism for negative stimuli in L2. However, we also found an enhanced response to positive feedbacks in L2 compared to L1, as evidenced by greater activation of the hippocampus for win feedbacks compared to safe feedbacks in L2, eventually resulting in a greater tendency to gamble. Thus, foreign language influenced decision making by both regulating emotional response to negative stimuli and enhancing emotional response to positive stimuli. This study helps unveiling the neural bases of the interaction between language and emotion in the foreign language context.

Association between tDCS computational modeling and clinical outcomes in depression: data from the ELECT-TDCS trial

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation intervention investigated for the treatment of depression. Clinical results have been heterogeneous, partly due to the variability of electric field (EF) strength in the brain owing to interindividual differences in head anatomy. Therefore, we investigated whether EF strength was correlated with behavioral changes in 16 depressed patients using simulated electric fields in real patient data from a controlled clinical trial. We hypothesized that EF strength in the dorsolateral prefrontal cortex (DLPFC) and anterior cingulate cortex (ACC), brain regions implicated in depression pathophysiology, would be associated with changes in depression, mood and anxiety scores. SimNIBS were used to simulate individual electric fields based on the MRI structural T1-weighted brain scans of depressed subjects. Linear regression models showed, at the end of the acute treatment phase, that simulated EF strength was inversely associated with negative affect in the bilateral ACC (left: β = - 160.463, CI [- 291.541, - 29.385], p = 0.021; right: β = - 189.194, CI [- 289.479, - 88.910], p = 0.001) and DLPFC (left: β = - 93.210, CI [- 154.960, - 31.461], p = 0.006; right: β = - 82.564, CI [- 142.867, - 22.262], p = 0.011) and with depression scores in the left ACC (β = - 156.91, CI [- 298.51, - 15.30], p = 0.033). No association between positive affect or anxiety scores, and simulated EF strength in the investigated brain regions was found. To conclude, our findings show preliminary evidence that EF strength simulations might be associated with further behavioral changes in depressed patients, unveiling a potential mechanism of action for tDCS. Further studies should investigate whether individualization of EF strength in key brain regions impact clinical response.

The role of dorsolateral and ventromedial prefrontal cortex in the processing of emotional dimensions

The ventromedial and dorsolateral prefrontal cortex are two major prefrontal regions that usually interact in serving different cognitive functions. On the other hand, these regions are also involved in cognitive processing of emotions but their contribution to emotional processing is not well-studied. In the present study, we investigated the role of these regions in three dimensions (valence, arousal and dominance) of emotional processing of stimuli via ratings of visual stimuli performed by the study participants on these dimensions. Twenty- two healthy adult participants (mean age 25.21 ± 3.84 years) were recruited and received anodal and sham transcranial direct current stimulation (tDCS) (1.5 mA, 15 min) over the dorsolateral prefrontal cortex (dlPFC) and and ventromedial prefrontal cortex (vmPFC) in three separate sessions with an at least 72-h interval. During stimulation, participants underwent an emotional task in each stimulation condition. The task included 100 visual stimuli and participants were asked to rate them with respect to valence, arousal, and dominance. Results show a significant effect of stimulation condition on different aspects of emotional processing. Specifically, anodal tDCS over the dlPFC significantly reduced valence attribution for positive pictures. In contrast, anodal tDCS over the vmPFC significantly reduced arousal ratings. Dominance ratings were not affected by the intervention. Our results suggest that the dlPFC is involved in control and regulation of valence of emotional experiences, while the vmPFC might be involved in the extinction of arousal caused by emotional stimuli. Our findings implicate dimension-specific processing of emotions by different prefrontal areas which has implications for disorders characterized by emotional disturbances such as anxiety or mood disorders.

Eye Movements and White Matter are Associated with Emotional Control in Children Treated for Brain Tumors

OBJECTIVE

Children treated for brain tumors often experience social and emotional difficulties, including challenges with emotion regulation; our goal was to investigate the attention-related component processes of emotion regulation, using a novel eye-tracking measure, and to evaluate its relations with emotional functioning and white matter (WM) organization.

METHOD

Fifty-four children participated in this study; 36 children treated for posterior fossa tumors, and 18 typically developing children. Participants completed two versions of an emotion regulation eye-tracking task, designed to differentiate between implicit (i.e., automatic) and explicit (i.e., voluntary) subprocesses. The Emotional Control scale from the Behavior Rating Inventory of Executive Function was used to evaluate emotional control in daily life, and WM organization was assessed with diffusion tensor imaging.

RESULTS

We found that emotional faces captured attention across all groups (F(1,51) = 32.18, p < .001, η2p = .39). However, unlike typically developing children, patients were unable to override the attentional capture of emotional faces when instructed to (emotional face-by-group interaction: F(2,51) = 5.58, p = .006, η2p = .18). Across all children, our eye-tracking measure of emotion regulation was modestly associated with the parent-report emotional control score (r = .29, p = .045), and in patients it was associated with WM microstructure in the body and splenium of the corpus callosum (all t > 3.03, all p < .05).

CONCLUSIONS

Our findings suggest that an attention-related component process of emotion regulation is disrupted in children treated for brain tumors, and that it may relate to their emotional difficulties and WM organization. This work provides a foundation for future theoretical and mechanistic investigations of emotional difficulties in brain tumor survivors.

The effects of left DLPFC tDCS on emotion regulation, biased attention, and emotional reactivity to negative content

The potentiation of neural activity in lateral prefrontal regions via transcranial direct current stimulation (tDCS) can reduce patterns of biased attention for threat and may facilitate intentional emotion regulation. The current study sought to determine whether left dorsolateral prefrontal cortex tDCS, in combination with intentional down-regulation of emotional responses would reduce negative appraisals of aversive content during emotional regulation (assessed during online tDCS), reduce patterns of biased attention and attention bias variability (assessed offline), and attenuate spontaneous (uninstructed) emotional reactivity to negative content (assessed offline) above tDCS or intentional down-regulation of emotions in isolation. Healthy participants (n = 116) were allocated to one of four experimental conditions involving either active or sham tDCS, combined with an either a down-regulate or maintain emotion regulation task. Attention bias/bias variability was assessed with an attentional probe task, and emotional reactivity was assessed in a negative video viewing task. tDCS did not affect the appraisals of negative stimuli during emotion regulation, and there were no effects on attention bias/bias variability. However, tDCS did attenuate emotional reactivity. Those receiving active stimulation showed smaller elevations in negative mood in response to viewing aversive video content compared with sham. The present findings are consistent with the potential of left frontal tDCS to attenuate negative emotional reactions to aversive content but provide no support for tDCS enhancement of emotion regulation, nor its impact on attention bias or attention bias variability.

Asymmetric Contributions of the Fronto-Parietal Network to Emotional Conflict in the Word–Face Interference Task

The fronto-parietal network is involved in top-down and bottom-up processes necessary to achieve cognitive control. We investigated the role of asymmetric enhancement of the left dorsolateral prefrontal cortex (lDLPFC) and right posterior parietal cortex (rPPC) in cognitive control under conditions of emotional conflict arising from emotional distractors. The effects of anodal tDCS over the lDLPFC/cathodal over the rPPC and the effects of anodal tDCS over the rPPC/cathodal over the lDLPFC were compared to sham tDCS in a double-blind design. The findings showed that anodal stimulation over the lDLPFC reduced interference from emotional distractors, but only when participants had already gained experience with the task. In contrast, having already performed the task only eliminated facilitation effects for positive stimuli. Importantly, anodal stimulation of the rPPC did not affect distractors’ interference. Therefore, the present findings indicate that the lDLPFC plays a crucial role in implementing top-down control to resolve emotional conflict, but that experience with the task is necessary to reveal this role.

Unskilled shooters improve both accuracy and grouping shot having as reference skilled shooters cortical area: An EEG and tDCS study

Transcranial direct current stimulation (tDCS) has been used as a non-invasive method for enhanced motor and cognitive abilities. However, no previous study has investigated if the tDCS application in unskilled shooters on cortical sites, selected based on the cortical activity of skilled shooters, improves the accuracy and shot grouping. Sixty participants were selected, which included 10 skilled shooters and 50 unskilled shooters. After we identified the right dorsolateral prefrontal cortex (DLPFC) as the area with the highest activity in skilled shooters, we applied anodal tDCS over the right DLPFC in the unskilled shooters under two conditions: sham-tDCS (placebo) and real-tDCS (anodal tDCS). We also analyzed electroencephalography. Our results indicated that anodal tDCS application enhanced the shot accuracy (p = 0.001). Furthermore, the beta power in the EEG recording was higher in the left DLPFC, left and right parietal cortex (p = 0,001) after applying anodal tDCS, while the low-gamma power was higher in the right DLPFC in sham-tDCS (p = 0.001) and right parietal cortex after anodal-tDCS (p = 0.001). Our findings indicate that anodal tDCS can improve accuracy and shot grouping when applied over the unskilled shooters' right DLPFC. Furthermore, beta and low-gamma bands are influenced by anodal tDCS over the right DLPFC, which may be predictive of skill improvement.

Arousal-Biased Competition Explains Reduced Distraction by Reward Cues under Threat

Anxiety is an adaptive neural state that promotes rapid responses under heightened vigilance when survival is threatened. Anxiety has consistently been found to potentiate the attentional processing of physically salient stimuli. However, a recent study demonstrated that a threat manipulation reduces attentional capture by reward-associated stimuli, suggesting a more complex relationship between anxiety and the control of attention. The mechanisms by which threat can reduce the distracting quality of stimuli are unknown. In this study, using functional magnetic resonance imaging (fMRI) on human subjects, we examined the neural correlates of attention to previously reward-associated stimuli with and without the threat of unpredictable electric shock. We replicate enhanced distractor-evoked activity throughout the value-driven attention network (VDAN) in addition to enhanced stimulus-evoked activity generally under threat. Importantly, these two factors interacted such that the representation of previously reward-associated distractors was particularly pronounced under threat. Our results from neuroimaging fit well with the principle of arousal-biased competition (ABC), although such effects are typically associated with behavioral measures of increased attention to stimuli that already possess elevated attentional priority. The findings of our study suggest that ABC can be leveraged to support more efficient ignoring of reward cues, revealing new insights into the functional significance of ABC as a mechanism of attentional control, and provide a mechanistic explanation of how threat reduces attention to irrelevant reward information.

tDCS increases anxiety reactivity to intentional worry

While considerable experimental research has examined the impact of transcranial direct current stimulation (tDCS) on a range of cognitive processes associated with emotional pathology, the impact of tDCS on worry has been comparatively neglected. Given that anxiety pathology is characterised by motivated engagement in worry, and that frontal tDCS has the capacity to enhance goal-oriented cognition, it is important to examine whether tDCS would increase or ameliorate the cognitive and emotional effects of worry. In the current study we examined how tDCS influenced the anxiety response to worry, and the frequency of negative intrusive thoughts. We additionally examined whether stimulation delivered in isolation, or in combination with a mindful-focus task would augment the effects of tDCS. Ninety-seven (75 female) healthy participants received either active or sham anodal tDCS to the left dorsolateral prefrontal cortex, delivered either in isolation or concurrently with a mindful task (four conditions). The frequency of negative thought intrusions was assessed before and after a period of instructed worry, and state anxiety was assessed across the study. Active tDCS was associated with significantly greater elevation in anxiety in response to the worry induction. No effects were observed on the frequency of negative thought intrusions, and the combined delivery of tDCS with the concurrent mindful task did not alter the pattern of observed effects. While inviting replication in a high anxious sample, the present results highlight the possibility that tDCS may interact with motivated engagement in negative patterns of cognition, such as worry, to produce greater emotional reactivity.

Searching for the optimal tDCS target for motor rehabilitation

BACKGROUND

Transcranial direct current stimulation (tDCS) has been investigated over the years due to its short and also long-term effects on cortical excitability and neuroplasticity. Although its mechanisms to improve motor function are not fully understood, this technique has been suggested as an alternative therapeutic method for motor rehabilitation, especially those with motor function deficits. When applied to the primary motor cortex, tDCS has shown to improve motor function in healthy individuals, as well as in patients with neurological disorders. Based on its potential effects on motor recovery, identifying optimal targets for tDCS stimulation is essential to improve knowledge regarding neuromodulation as well as to advance the use of tDCS in clinical motor rehabilitation.

METHODS AND RESULTS

Therefore, this review discusses the existing evidence on the application of four different tDCS montages to promote and enhance motor rehabilitation: (1) anodal ipsilesional and cathodal contralesional primary motor cortex tDCS, (2) combination of central tDCS and peripheral electrical stimulation, (3) prefrontal tDCS montage and (4) cerebellar tDCS stimulation. Although there is a significant amount of data testing primary motor cortex tDCS for motor recovery, other targets and strategies have not been sufficiently tested. This review then presents the potential mechanisms and available evidence of these other tDCS strategies to promote motor recovery.

CONCLUSIONS

In spite of the large amount of data showing that tDCS is a promising adjuvant tool for motor rehabilitation, the diversity of parameters, associated with different characteristics of the clinical populations, has generated studies with heterogeneous methodologies and controversial results. The ideal montage for motor rehabilitation should be based on a patient-tailored approach that takes into account aspects related to the safety of the technique and the quality of the available evidence.

Inverse effects of tDCS over the left versus right DLPC on emotional processing: A pupillometry study

Background and objectives

The Dorsolateral prefrontal cortex (DLPFC) is implicated in cognitive and emotional responses. Yet, research that investigates the causal role of the left versus right DLPFC during the processes of emotion appraisal is lacking. In the current study, transcranial direct current stimulation (tDCS) was used to disentangle the functional lateralization of the DLPFC on emotional processing in response to the anticipation of, and subsequent confrontation with emotional stimuli in healthy volunteers.

Methods

Forty-eight subjects received both active and sham (on separate days) anodal tDCS over either the left (N = 24) or right (N = 24) DLPFC. Subjects’ pupil dilation (PD, a physiological marker of cognitive resource allocation) was recorded while performing an appraisal task in which negative and positive emotion eliciting images were presented, each preceded by an informative cue indicating the valence of the upcoming stimulus.

Results

As compared to sham stimulation, left DLPFC anodal tDCS resulted in increased PD when confronted with negative emotional images, whereas right DLPFC anodal tDCS resulted in decreased PD when confronted with emotional images, irrespective of valence.

Limitations

The interpretation of pupil dilation in response to emotional stimuli is limited.

Conclusion

These findings suggest inverse lateralized DLPFC effects on cognitive resource allocation (as measured by pupillary responses) when confronted with emotional stimuli. The current findings may shed some light on mechanisms that explain the antidepressant effects of non-invasive brain stimulation of the left DLPFC.

Efficiency of Repetitive Transcranial Direct Current Stimulation of the Dorsolateral Prefrontal Cortex in Disorders of Consciousness: A Randomized Sham-Controlled Study

Conventional transcranial direct current stimulation (tDCS) targeting the left dorsolateral prefrontal cortex (DLPFC) could improve arousal in disorders of consciousness (DOC). However, the comparative effectiveness of anodal stimulation of the left DLPFC and the electrophysiological effect of tDCS are yet to be determined. In this randomized sham-controlled design, patients were separated into three groups (left/right anodal tDCS, sham). Data on the clinical assessments and EEG were collected at baseline and after 2 weeks of tDCS. The outcome at 3-month follow-up was evaluated using the Glasgow Outcome Scale-Extended. Results showed that sessions of the left tDCS facilitated the excitability of the prefrontal cortex, whereas only one patient had a positive outcome. Targeting the right DLPFC was less effective, merely leading to activation of the stimulation site, with no effect on the state of arousal. Moreover, sham stimulation had minimal or no effect on any of the outcomes. These results provide evidence for a hemispheric asymmetry of tDCS effects in patients with DOC. Left anodal tDCS might be more effective for modulating cortical excitability compared to tDCS on the right DLPFC. However, future studies with large sample sizes are needed to confirm these findings. This trial is registered with NCT03809936.

Does Change in Attention Control Mediate the Impact of tDCS on Attentional Bias for Threat? Limited Evidence from a Double-blind Sham-controlled Experiment in an Unselected Sample

Neurocognitive models of attentional bias for threat posit that attentional bias may result from a decreased activation of the left prefrontal cortex, and especially of its dorsolateral part (dlPFC), resulting in an impaired attention control. Consequently, a transient increase of neural activity within the left dlPFC via non-invasive brain stimulation reduces attentional bias among both anxious and nonanxious participants. Yet, it is still unclear whether the impact of dlPFC activation on attentional bias is mediated by improvement in attention control. In this experiment, we sought to test this hypothesis in an unselected sample (n = 20). Accordingly, we adopted a double-blind within-subject protocol in which we delivered a single-session of anodal versus sham transcranial Direct Current Stimulation (tDCS) over the left dlPFC during the completion of a task assessing attention control. We also assessed its subsequent impact on attentional bias. Neither attention control nor attentional bias did significantly improve following anodal tDCS. Although our results do not support our main hypothesis, we believe the present null results to be particularly useful for future meta-research in the field. We also formulated a series of methodological recommendations for future research aiming at testing the tDCS-induced modification of attentional bias.

Transcranial Direct Current Stimulation in Obsessive-Compulsive Disorder, Posttraumatic Stress Disorder, and Anxiety Disorders

Obsessive-compulsive disorder (OCD), posttraumatic stress disorder (PTSD), and anxiety disorders share the basic clinical feature of anxiety, which probably explains their common response to similar pharmacological and psychological interventions. Transcranial direct current stimulation (tDCS) is a neuromodulation technique that has proved effective in reducing the symptoms of a number of neuropsychiatric disorders. It was also used in healthy subjects to modulate neuropsychological processes that are involved in the pathophysiology of anxiety. We review the published studies in which tDCS was administered to patients with OCD, PTSD, or anxiety disorders. Our systematic search in the major electronic databases resulted in 14 articles for OCD, 1 for an OCD-related disorder (ie, hoarding disorder), 2 for PTSD, and 2 for anxiety disorders. In the studies involving OCD patients, tDCS was targeted to either the dorsolateral prefrontal cortex or the orbitofrontal cortex or the pre-supplementary motor area and induced a clear reduction of obsessive-compulsive symptoms. However, the lack of sham control groups and the great diversity in sample selection and tDCS protocols among studies prevent us from generalizing these results. In the studies involving PTSD and anxiety disorders patients, tDCS was applied over the dorsolateral prefrontal cortex and reduced symptoms, but the number of treated patients is too little to draw any conclusion on efficacy. However, these reports highlighted the importance of combining tDCS with different procedures, including computerized tasks and behavioral paradigms. In conclusion, even in its infancy, the use of tDCS for the treatment of OCD, PTSD, and anxiety disorders does show promise and deserves extensive research effort.