Noninvasive stimulation of the ventromedial prefrontal cortex modulates emotional face processing

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.

Effects of tDCS on emotion recognition and brain oscillations

INTRODUCTION

Emotion recognition, the ability to interpret the emotional state of individuals by looking at their facial expressions, is essential for healthy social interactions and communication. There is limited research on the effects of tDCS on emotion recognition in the literature. This study aimed to investigate the effects of anodal stimulation of the ventromedial prefrontal cortex (vmPFC), a key region for emotion recognition from facial expressions, on emotion recognition and brain oscillations.

METHOD

A single-blind randomized-controlled study was conducted with 54 healthy participants. Before and after brain stimulation emotion recognition tasks were administered and resting-state EEG were recorded. The changes in task performances and brain oscillations were analyzed using repeated-measures two-way ANOVA analysis.

RESULTS

There was no significant difference in the emotion recognition tasks between groups in pre-post measurements. The changes in delta, theta, alpha, beta and gamma frequency bands in the frontal, temporal, and posterio-occipital regions, which were determined as regions of interest in resting state EEG data before and after tDCS, were compared between groups. The results showed that there was a significant difference between groups only in delta frequency before and after tDCS in the frontal and temporal regions. While an increase in delta activity was observed in the experimental group in the frontal and temporal regions, a decrease was observed in the control group.

CONCLUSIONS

The tDCS may not have improved emotion recognition because it may not have had the desired effect on the vmPFC, which is in the lower part of the prefrontal lobe. The changes in EEG frequencies observed section tDCS may be similar to those seen in some pathological processes, which could explain the lack of improvement in emotion recognition. Future studies to be carried out for better understand this effect are important.

Higher-order comparative reward processing is affected by noninvasive stimulation of the ventromedial prefrontal cortex

A crucial skill, especially in rapidly changing environments, is to be able to learn efficiently from prior rewards or losses and apply this acquired knowledge in upcoming situations. Often, we must weigh the risks of different options and decide whether an option is worth the risk or whether we should choose a safer option. The ventromedial prefrontal cortex (vmPFC) is suggested as a major hub for basic but also higher-order reward processing. Dysfunction in this region has been linked to cognitive risk factors for depression and behavioral addictions, including reduced optimism and feedback learning. Here, we test whether modulations of vmPFC excitability via noninvasive transcranial direct current stimulation (tDCS) can alter reward anticipation and reward processing. In a financial gambling task, participants chose between a higher and a lower monetary risk option and eventually received feedback whether they won or lost. Simultaneously feedback on the unchosen option was presented as well. Behavioral and magnetoencephalographic correlates of reward processing were evaluated in direct succession of either excitatory or inhibitory tDCS of the vmPFC. We were able to show modulated reward approach behavior (expectancy of greater reward magnitudes) as well as altered reevaluation of received feedback by vmPFC tDCS as indicated by modified choice behavior following the feedback. Thereby, tDCS not only influenced early, rather basic reward processing, but it also modulated higher-order comparative feedback evaluation of gains and losses relative to alternative outcomes. The neural results underline this idea, as stimulation-driven modulations of the basic reward-related effect occurred at rather early time intervals and were followed by stimulation effects related to comparative reward processing. Importantly, behavioral ratings were correlated with neural activity in left frontal areas. Our results imply a dual function of the vmPFC consisting of approaching reward (as indicated by more risky choices) and elaborately evaluating outcomes. In addition, our data suggest that vmPFC activity is associated with adaptive decision-making in the future via modulated behavioral adaptation or reinforcement learning.

Inhibition of the dorsolateral cortex reveals specific mechanisms behind emotional control

Reappraisal is a complex emotional control strategy based on cognitive change. To complete the reappraisal task, one is required to deeply elaborate on the affective stimulus to create its new interpretation. The involvement of the prefrontal cortex in this process was examined in the study, where inhibition of the left or right dorsolateral area was carried out using transcranial magnetic stimulation. In a between-subject design, we used an alternative control condition for the reappraisal task. It was intended to better account for overall task activity compared to typical passive conditions. Late positive potential was affected after inhibition of the prefrontal area, suggesting hindered emotional control. This effect was specific to the reappraisal task, which possibly reflects the disturbance of attention allocation to emotional stimuli. We could also observe an increased transfer of information from the visual area during the control task that was based on the elaboration of emotional stimuli but did not involve cognitive change. Our results support the additive impact of several factors on the overall efficiency of emotional control.

Tinnitus-on the interplay between emotion and cognition

Subjective tinnitus (hereafter tinnitus) is often considered and studied as a perceptual phenomenon. Accordingly, various abnormalities in the area of cognitive processing have been reported in patients with tinnitus. At the same time, the disorder is characterized by considerable emotional distress, which is associated with a high comorbidity of affective disorders. Here, we aim to outline the close link between cognition and emotion, and how current research from the field of cognitive neuroscience examines the processing and acquisition of emotional stimuli. The emotional valence of stimuli can be acquired after brief exposure to learning, leading from neutral to appetitive or aversive evaluation. In contrast to neutral stimuli, emotional stimuli attract attention very early (about 100 ms) during processing, leading to deeper processing and corresponding memory effects. The involved subcortical and cortical network encompasses limbic and sensory areas. In particular, prefrontal regions are involved in the acquisition and evaluation of emotional stimuli as also shown in studies of patients with affect disorders. The interplay of cognitive and emotional processes seems to be central to the development, maintenance, and treatment of tinnitus.

Excitatory stimulation of the ventromedial prefrontal cortex reduces cognitive gambling biases via improved feedback learning

Humans are subject to a variety of cognitive biases, such as the framing-effect or the gambler's fallacy, that lead to decisions unfitting of a purely rational agent. Previous studies have shown that the ventromedial prefrontal cortex (vmPFC) plays a key role in making rational decisions and that stronger vmPFC activity is associated with attenuated cognitive biases. Accordingly, dysfunctions of the vmPFC are associated with impulsive decisions and pathological gambling. By applying a gambling paradigm in a between-subjects design with 33 healthy adults, we demonstrate that vmPFC excitation via transcranial direct current stimulation (tDCS) reduces the framing-effect and the gambler's fallacy compared to sham stimulation. Corresponding magnetoencephalographic data suggest improved inhibition of maladaptive options after excitatory vmPFC-tDCS. Our analyses suggest that the underlying mechanism might be improved reinforcement learning, as effects only emerge over time. These findings encourage further investigations of whether excitatory vmPFC-tDCS has clinical utility in treating pathological gambling or other behavioral addictions.

[Tinnitus-on the interplay between emotion and cognition. German version]

Subjective tinnitus (hereafter tinnitus) is often considered and studied as a perceptual phenomenon. Accordingly, various abnormalities in the area of cognitive processing have been reported in patients with tinnitus. At the same time, the disorder is characterized by considerable emotional distress, which is associated with a high comorbidity of affective disorders. Here, we aim to outline the close link between cognition and emotion, and how current research from the field of cognitive neuroscience examines the processing and acquisition of emotional stimuli. The emotional valence of stimuli can be acquired after brief exposure to learning, leading from neutral to appetitive or aversive evaluation. In contrast to neutral stimuli, emotional stimuli attract attention very early (about 100 ms) during processing, leading to deeper processing and corresponding memory effects. The involved subcortical and cortical network encompasses limbic and sensory areas. In particular, prefrontal regions are involved in the acquisition and evaluation of emotional stimuli as also shown in studies of patients with affect disorders. The interplay of cognitive and emotional processes seems to be central to the development, maintenance, and treatment of tinnitus.

Non-invasive stimulation reveals ventromedial prefrontal cortex function in reward prediction and reward processing

Introduction

Studies suggest an involvement of the ventromedial prefrontal cortex (vmPFC) in reward prediction and processing, with reward-based learning relying on neural activity in response to unpredicted rewards or non-rewards (reward prediction error, RPE). Here, we investigated the causal role of the vmPFC in reward prediction, processing, and RPE signaling by transiently modulating vmPFC excitability using transcranial Direct Current Stimulation (tDCS).

Methods

Participants received excitatory or inhibitory tDCS of the vmPFC before completing a gambling task, in which cues signaled varying reward probabilities and symbols provided feedback on monetary gain or loss. We collected self-reported and evaluative data on reward prediction and processing. In addition, cue-locked and feedback-locked neural activity via magnetoencephalography (MEG) and pupil diameter using eye-tracking were recorded.

Results

Regarding reward prediction (cue-locked analysis), vmPFC excitation (versus inhibition) resulted in increased prefrontal activation preceding loss predictions, increased pupil dilations, and tentatively more optimistic reward predictions. Regarding reward processing (feedback-locked analysis), vmPFC excitation (versus inhibition) resulted in increased pleasantness, increased vmPFC activation, especially for unpredicted gains (i.e., gain RPEs), decreased perseveration in choice behavior after negative feedback, and increased pupil dilations.

Discussion

Our results support the pivotal role of the vmPFC in reward prediction and processing. Furthermore, they suggest that transient vmPFC excitation via tDCS induces a positive bias into the reward system that leads to enhanced anticipation and appraisal of positive outcomes and improves reward-based learning, as indicated by greater behavioral flexibility after losses and unpredicted outcomes, which can be seen as an improved reaction to the received feedback.

Neural correlates of conscious processing of emotional faces: Evidence from event-related potentials

There is a theoretical debate between the early and late neural correlates of consciousness (NCCs). Previous studies using neutral face stimuli supported an early NCC and suggested that visual awareness negativity (VAN) is associated with consciousness, while late positivity (LP) reflects post-perceptual activity. However, emotional faces may help to examine the relationship between LP and consciousness due to the differences in late processing between emotional and neutral faces. To explore the effects of facial emotional information on NCCs, the present study manipulated consciousness with the inattentional blindness paradigm and used happy, fearful, and neutral faces as visual stimuli. The results showed that the conscious processing of emotional faces was correlated with VAN and LP, while the conscious processing of neutral faces was associated with VAN. First, the results suggest that VAN is an NCC, and the relationship between LP and consciousness is affected by facial emotional information. Second, VAN reflects the early perceptual experience of emotional faces, whereas LP may reflect the late conscious processing of emotional faces. Furthermore, source localization analysis showed that the LPs of emotional faces were mainly located in the frontal and parietal lobes, whereas those of neutral faces showed no significant activation. This suggests that facial emotional information may affect the brain regions associated with conscious processing. Time-frequency analysis showed that conscious processing is related to the enhancement of alpha and theta oscillation, indicating that conscious processing may be associated with the suppression of irrelevant stimuli. Overall, the present study suggests that the integration of the theories that support early and late NCCs helps explain the conscious processing of emotional faces.

Bioelectromagnetism in Human Brain Research: New Applications, New Questions

Bioelectromagnetism has contributed some of the most commonly used techniques to human neuroscience such as magnetoencephalography (MEG), electroencephalography (EEG), transcranial magnetic stimulation (TMS), and transcranial electric stimulation (TES). The considerable differences in their technical design and practical use give rise to the impression that these are quite different techniques altogether. Here, we review, discuss and illustrate the fundamental principle of Helmholtz reciprocity that provides a common ground for all four techniques. We show that, more than 150 years after its discovery by Helmholtz in 1853, reciprocity is important to appreciate the strengths and limitations of these four classical tools in neuroscience. We build this case by explaining the concept of Helmholtz reciprocity, presenting a methodological account of this principle for all four methods and, finally, by illustrating its application in practical clinical studies.

Noninvasive stimulation of the ventromedial prefrontal cortex modulates rationality of human decision-making

The framing-effect is a bias that affects decision-making depending on whether the available options are presented with positive or negative connotations. Even when the outcome of two choices is equivalent, people have a strong tendency to avoid the negatively framed option. The ventromedial prefrontal cortex (vmPFC) is crucial for rational decision-making, and dysfunctions in this region have been linked to cognitive biases, impulsive behavior and gambling addiction. Using a financial decision-making task in combination with magnetoencephalographic neuroimaging, we show that excitatory compared to inhibitory non-invasive transcranial direct current stimulation (tDCS) of the vmPFC reduces framing-effects while improving the assessment of loss-probabilities, ultimately leading to increased overall gains. Behavioral and neural data consistently suggest that this improvement in rational decision-making is predominately due to an attenuation of biases towards negative affect (loss-aversion and risk-aversion). These findings recommend further research towards clinical applications of vmPFC-tDCS as in addictive disorders.

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.

Transcranial Direct Current Stimulation of the Ventromedial Prefrontal Cortex Modulates Perceptual and Neural Patterns of Fear Generalization

BACKGROUND

Overgeneralization of fear is a pathogenic marker of anxiety and stress-related disorders and has been linked with perceptual discrimination deficits, reduced fear inhibition, and prefrontal hyporeactivity to safety-signaling stimuli. We aimed to examine whether behavioral and neural patterns of fear generalization are influenced by the fear-inhibiting ventromedial prefrontal cortex (vmPFC).

METHODS

Three groups of healthy participants received excitatory (n = 27), inhibitory (n = 26), or sham (n = 26) transcranial direct current stimulation of the vmPFC after a fear conditioning phase and before a fear generalization phase. We obtained, as dependent variables, fear ratings and unconditioned stimulus-expectancy ratings, perceptual aspects of fear generalization (perceptual discrimination), pupil dilations, and source estimations of event-related fields elicited by conditioned and generalization stimuli.

RESULTS

After inhibitory (compared with excitatory and sham) vmPFC stimulation, we observed reduced performance in perceptual discrimination and less negative inhibitory gradients in frontal structures at midlatency and late time intervals. Fear and unconditioned stimulus-expectancy ratings as well as pupil dilation remained unaffected by stimulation.

CONCLUSIONS

These findings reveal a causal contribution of vmPFC reactivity to generalization patterns and suggest that vmPFC hyporeactivity consequent on inhibitory vmPFC stimulation may serve as a model for pathological processes of fear generalization (reduced discrimination, impaired fear inhibition via frontal brain structures). This encourages further basic and clinical research on the potential of targeted brain stimulation to modulate fear generalization and overgeneralization.

Ventromedial Prefrontal Cortex Drives the Prioritization of Self-Associated Stimuli in Working Memory

Humans show a pervasive bias for processing self- over other-related information, including in working memory (WM), where people prioritize the maintenance of self- (over other-) associated cues. To elucidate the neural mechanisms underlying this self-bias, we paired a self- versus other-associated spatial WM task with fMRI and transcranial direct current stimulation (tDCS) of human participants of both sexes. Maintaining self- (over other-) associated cues resulted in enhanced activity in classic WM regions (frontoparietal cortex), and in superior multivoxel pattern decoding of the cue locations from visual cortex. Moreover, ventromedial PFC (VMPFC) displayed enhanced functional connectivity with WM regions during maintenance of self-associated cues, which predicted individuals' behavioral self-prioritization effects. In a follow-up tDCS experiment, we targeted VMPFC with excitatory (anodal), inhibitory (cathodal), or sham tDCS. Cathodal tDCS eliminated the self-prioritization effect. These findings provide strong converging evidence for a causal role of VMPFC in driving self-prioritization effects in WM and provide a unique window into the interaction between social, self-referential processing and high-level cognitive control processes.SIGNIFICANCE STATEMENT People have a strong tendency to attend to self-related stimuli, such as their names. This self-bias extends to the automatic prioritization of arbitrarily self-associated stimuli held in working memory. Since working memory is central to high-level cognition, this bias could influence how we make decisions. It is therefore important to understand the underlying brain mechanisms. Here, we used neuroimaging and noninvasive neurostimulation techniques to show that the source of self-bias in working memory is the ventromedial PFC, which modulates activity in frontoparietal brain regions to produce prioritized representations of self-associated stimuli in sensory cortex. This work thus reveals a brain circuit underlying the socially motivated (self-referential) biasing of high-level cognitive processing.

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.

Effects of Transcranial Direct Current Stimulation on Information Processing Speed, Working Memory, Attention, and Social Cognition in Multiple Sclerosis

Multiple Sclerosis (MS) is a chronic inflammatory disease of the central nervous system. Cognitive impairment occurs in 40-65% of patients and could drastically affect their quality of life. Deficits could involve general cognition (e.g., attention and working memory) as well as social cognition. Transcranial direct current stimulation (tDCS), is a novel brain stimulation technique that has been assessed in the context of several neuropsychiatric symptoms, including those described in the context of MS. However, very rare trials have assessed tDCS effects on general cognition in MS, and none has tackled social cognition. The aim of this work was to assess tDCS effects on general and social cognition in MS. Eleven right-handed patients with MS received two blocks (bifrontal tDCS and sham, 2 mA, 20 min, anode/cathode over left/right prefrontal cortex) of 5 daily stimulations separated by a 3-week washout interval. Working memory and attention were, respectively, measured using N-Back Test (0-Back, 1-Back, and 2-Back) and Symbol Digit Modalities Test (SDMT) at the first and fifth day of each block and 1 week later. Social cognition was evaluated using Faux Pas Test and Eyes Test at baseline and 1 week after each block. Interestingly, accuracy of 1-Back test improved following sham but not active bifrontal tDCS. Therefore, active bifrontal tDCS could have impaired working memory via cathodal stimulation of the right prefrontal cortex. No significant tDCS effects were observed on social cognitive measures and SDMT. Admitting the small sample size and the learning (practice) effect that might arise from the repetitive administration of each task, the current results should be considered as preliminary and further investigations in larger patient samples are needed to gain a closer understanding of tDCS effects on cognition in MS.

Acute aerobic exercise enhances pleasant compared to unpleasant visual scene processing

Although acute aerobic exercise benefits different aspects of emotional functioning, it is unclear how exercise influences the processing of emotional stimuli and which brain mechanisms support this relationship. We assessed the influence of acute aerobic exercise on valence biases (preferential processing of negative/positive pictures) by performing source reconstructions of participants' brain activity after they viewed emotional scenes. Twenty-four healthy participants (12 women) were tested in a randomized and counterbalanced design that consisted of three experimental protocols, each lasting 30 min: low-intensity exercise (Low-Int); moderate-intensity exercise (Mod-Int); and a seated rest condition (REST). After each of the protocols, participants viewed negative and positive pictures, during which event-related magnetic fields were recorded. Analyses revealed that exercise strongly impacted the valence processing of emotional scenes within a widely distributed left hemispheric spatio-temporal cluster between 190 and 310 ms after picture onset. Brain activity in this cluster showed that a negativity bias at REST (negative > positive picture processing) diminished after the Low-Int condition (positive = negative) and even reversed to a positivity bias after the Mod-Int condition (positive > negative). Thus, acute aerobic exercise of low and moderate intensities induces a positivity bias which is reflected in early, automatic processes.

Repeated noninvasive stimulation of the ventromedial prefrontal cortex reveals cumulative amplification of pleasant compared to unpleasant scene processing: A single subject pilot study

The ventromedial prefrontal cortex (vmPFC) is a major hub of the reward system and has been shown to activate specifically in response to pleasant / rewarding stimuli. Previous studies demonstrate enhanced pleasant cue reactivity after single applications of transcranial direct current stimulation (tDCS) to the vmPFC. Here we present a pilot case study in which we assess the cumulative impact of multiple consecutive vmPFC-tDCS sessions on the processing of visual emotional stimuli in an event-related MEG recording design. The results point to stable modulation of increased positivity biases (pleasant > unpleasant stimulus signal strength) after excitatory vmPFC stimulation and a reversed pattern (pleasant < unpleasant) after inhibitory stimulation across five consecutive tDCS sessions. Moreover, cumulative effects of these emotional bias modulations were observable for several source-localized spatio-temporal clusters, suggesting an increase in modulatory efficiency by repeated tDCS sessions. This pilot study provides evidence for improvements in the effectiveness and utility of a novel tDCS paradigm in the context of emotional processing.

Transcranial direct current stimulation (tDCS) over vmPFC modulates interactions between reward and emotion in delay discounting

Delay discounting requires computing trade-offs between immediate-small rewards and later-larger rewards. Negative and positive emotions shift decisions towards more or less impulsive responses, respectively. Models have conceptualized this trade-off by describing an interplay between “emotional” and “rational” processes, with the former involved during immediate choices and relying on the ventromedial prefrontal cortex (vmPFC), and the latter involved in long-term choices and relying on the dorsolateral prefrontal cortex (dlPFC). Whether stimulation of the vmPFC modulates emotion-induced delay discounting remains unclear. We applied tDCS over the vmPFC in 20 healthy individuals during a delay discounting task following an emotional (positive, negative) or neutral induction. Our results showed that cathodal tDCS increased impulsivity after positive emotions in high impulsivity trials. For low impulsivity trials, anodal tDCS decreased impulsivity following neutral induction compared with emotional induction. Our findings demonstrate that the vmPFC integrates reward and emotion most prominently in situations of increased impulsivity, whereas when higher cognitive control is required the vmPFC appears to be less engaged, possibly due to recruitment of the dlPFC. Understanding how stimulation and emotion influence decision-making at the behavioural and neural levels holds promise to develop interventions to reduce impulsivity.

Noninvasive Stimulation of the Ventromedial Prefrontal Cortex Indicates Valence Ambiguity in Sad Compared to Happy and Fearful Face Processing

The ventromedial prefrontal cortex (vmPFC) is known to be specifically involved in the processing of stimuli with pleasant, rewarding meaning to the observer. By the use of non-invasive transcranial direct current stimulation (tDCS), it was previously possible to show evidence for this valence specificity and to modulate the impact of the vmPFC on emotional network processing. Prior results showed increased neural activation during pleasant relative to unpleasant stimulus processing after excitatory compared to inhibitory vmPFC-tDCS. As dysfunctional vmPFC activation patterns are associated with major depressive disorder (MDD), tDCS of this region could render an attractive application in future therapy. Here, we investigated vmPFC-tDCS effects on sad compared to happy face processing, as sad faces are often used in the study of mood disorders. After counterbalanced inhibitory or excitatory tDCS, respectively, healthy participants viewed happy and sad faces during magnetoencephalography (MEG) recording. In addition, tDCS effects on an interpretational bias of ambiguous happy-sad face morphs and an attentional bias of a dot-probe task with happy and sad faces as emotional primes were investigated. Finally, in conjoint analyses with data from a previous sibling study (happy and fearful faces) we examined whether excitatory vmPFC-tDCS would reveal a general increase in processing of pleasant stimuli independent of the type of unpleasant stimuli applied (sad vs. fearful faces). MEG and behavioral results showed that happy faces promoted a relative positivity bias after excitatory compared to inhibitory tDCS, visible in left orbitofrontal cortex and in the emotion-primed dot-probe task. A converse pattern in the MEG data during sad face processing suggests the possible involvement of an empathy network and thus significantly differed from neuronal processing of fearful face processing. Implications for the bearing of vmPFC modulation on emotional face processing and the impact of specific unpleasant face expressions are discussed.

Type 1 diabetes and working memory processing of emotional faces

Several executive functions decline with the development of type-1 diabetes (T1D), particularly working memory (WM). In adults, WM ensures efficient cognitive processing by focusing on task-relevant information while suppressing distractors. It has been well documented that WM can be influenced by emotional stimuli, which may facilitate the retention of information, interfere with uptake, or even affect its capacity. We evaluated the effect of T1D on visual WM processing using emotional faces as stimuli, in young patients with satisfactory clinical evolution, and matched controls without T1D. All subjects performed a 2-back task detecting facial identity using neutral, happy or fearful faces in a block design for fMRI. Behavioral performance was similar with the exception that patients responded significantly slower. Most importantly, between-group differences were found in patterns of brain activation. In comparison, more widespread brain activation -predominantly prefrontal- was found in the participants with T1D when processing neutral faces, while a decrease was observed when processing happy and fearful ones. Statistical contrasts demonstrated significantly-different activation patterns between groups when processing emotional faces, as controls exhibited greater activation in the cuneus, posterior cortex and parahippocampal gyrus, while the patients showed greater activation in the prefrontal structures. Results may reflect compensatory efforts made to minimize the deleterious effects of disease development on attention allocation processes and the operational efficiency of WM. The results suggest that emotional parameters should be periodically assessed in individuals with T1D in order to anticipate the emergence of attention and WM impairment.