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.

Moving toward reality: Electrocortical reactivity to naturalistic multimodal emotional videos

While previous research has investigated the effects of emotional videos on peripheral physiological measures and conscious experience, this study extends the research to include electrocortical measures, specifically the steady-state visual-evoked potential (ssVEP). A carefully curated set of 45 videos, designed to represent a wide range of emotional and neutral content, were presented with a flickering border. The videos featured a continuous single-shot perspective, natural soundtrack, and excluded elements associated with professional films, to enhance realism. The results demonstrate a consistent reduction in ssVEP amplitude during emotional videos which strongly correlates with the rated emotional intensity of the clips. This suggests that narrative audiovisual stimuli have the potential to track dynamic emotional processing in the cortex, providing new avenues for research in affective neuroscience. The findings highlight the potential of using realistic video stimuli to investigate how the human brain processes emotional events in a paradigm that increases ecological validity. Future studies can further develop this paradigm by expanding the video set, targeting specific cortical networks, and manipulating narrative predictability. Overall, this study establishes a foundation for investigating emotional perception using realistic video stimuli and has the potential to expand our understanding of real-world emotional processing in the human brain.

Optimizing electrode placement for transcranial direct current stimulation in nonsuperficial cortical regions: a computational modeling study

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique for modulating neuronal excitability by sending a weak current through electrodes attached to the scalp. For decades, the conventional tDCS electrode for stimulating the superficial cortex has been widely reported. However, the investigation of the optimal electrode to effectively stimulate the nonsuperficial cortex is still lacking. In the current study, the optimal tDCS electrode montage that can deliver the maximum electric field to nonsuperficial cortical regions is investigated. Two finite element head models were used for computational simulation to determine the optimal montage for four different nonsuperficial regions: the left foot motor cortex, the left dorsomedial prefrontal cortex (dmPFC), the left medial orbitofrontal cortex (mOFC), and the primary visual cortex (V1). Our findings showed a good consistency in the optimal montage between two models, which led to the anode and cathode being attached to C4-C3 for the foot motor, F4-F3 for the dmPFC, Fp2-F7 for the mOFC, and Oz-Cz for V1. Our suggested montages are expected to enhance the overall effectiveness of stimulation of nonsuperficial cortical areas.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13534-023-00335-2.

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.

The role of prefrontal cortex and temporoparietal junction in interpersonal comfort and emotional approach

Our perception of physical distance to individuals and stimuli is influenced by our mental distance and relatedness. The present study aimed to investigate the role of the dorsolateral prefrontal cortex (dlPFC), ventromedial prefrontal cortex (vmPFC), and right temporoparietal junction (rTPJ) in interpersonal comfortable distance and approach behaviors towards emotional stimuli. Twenty healthy volunteers received brain stimulation in four separate sessions with a one-week interval, including anodal left dlPFC, anodal right vmPFC, anodal rTPJ, and sham condition, with an extracranial return electrode. Our results revealed an increase in interpersonal distance during anodal rTPJ stimulation and a decrease in distance to positive pictures during anodal vmPFC stimulation. These findings suggest that the rTPJ plays a role in the perceptual component of self-other distancing, while the vmPFC is involved in approaching positive emotions.

Emotional processing and positive affect after acute exercise in healthy older adults

The well-elucidated improvement of mood immediately after exercise in older adults presumably involves adaptations in emotion-processing brain networks. However, little is known about effects of acute exercise on appetitive and aversive emotion-related network recruitment in older adults. The purpose of this study was to determine the effect of acute exercise, compared to a seated rest control condition, on pleasant and unpleasant emotion-related regional activation in healthy older adults. Functional MRI data were acquired from 32 active older adults during blocked presentations of pleasant, neutral and unpleasant images from the International Affective Pictures System. fMRI data were collected after participants completed 30 min of moderate to vigorous intensity cycling or seated rest, performed in a counterbalanced order across separate days in a within-subject design. The findings suggest three ways that emotional processing in the brain may be different immediately after exercise (relative to immediately after rest): First, reduced demands on emotional regulation during pleasant emotional processing as indicated by lower precuneus activation for pleasant stimuli; second, reduced processing of negative emotional stimuli in visual association areas as indicated by lower activation for unpleasant stimuli in the bilateral fusiform and ITG; third, an increased recruitment in activation associated with regulating/inhibiting unpleasant emotional processing in the bilateral medial superior frontal gyrus (dorsomedial prefrontal cortex), angular gyri, supramarginal gyri, left cerebellar crus I/II and a portion of right dorsolateral prefrontal cortex. Overall, these findings support that acute exercise in active older adults alters activation in key emotional processing and regulating brain regions.

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.

Noninvasive Brain Stimulation Techniques for Treatment-Resistant Depression: Transcranial Magnetic Stimulation and Transcranial Direct Current Stimulation

Transcranial magnetic stimulation is a safe, effective, and well-tolerated intervention for depression; it is currently approved for treatment-resistant depression. This article summarizes the mechanism of action, evidence of clinical efficacy, and the clinical aspects of this intervention, including patient evaluation, stimulation parameters selection, and safety considerations. Transcranial direct current stimulation is another neuromodulation treatment for depression; although promising, the technique is not currently approved for clinical use in the United States. The final section outlines the open challenges and future directions of the field.

The update of self-identity: Importance of assessing autobiographical memory in major depressive disorder

Major depressive disorder is a leading global cause of disability. There is a growing interest for memory in mood disorders since it might constitute an original tool for prevention, diagnosis, and treatment. MDD is associated with impaired autobiographical memory characterized by a tendency to overgeneral memory, rather than vivid episodic self-defining memory, which is mandatory for problem-solving and projection in the future. This memory bias is maintained by three mechanisms: ruminations, avoidance, and impaired executive control. If we adopt a broader and comprehensive perspective, we can hypothesize that all those alterations have the potential to impair self-identity updating. We posit that this update requires a double referencing process: (1) to internalized self-representation and (2) to an externalized framework dealing with the representation of the consequence of actions. Diagnostic and therapeutic implications are discussed in the light of this model and the importance of assessing autobiographical memory in MDD is highlighted. This article is categorized under: Psychology > Memory Psychology > Brain Function and Dysfunction Neuroscience > Clinical.

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.

A 5-min paradigm to evoke robust emotional reactivity in neuroimaging studies

The advent of the Research Domain Criteria (RDoC) approach to funding translational neuroscience has highlighted a need for research that includes measures across multiple task types. However, the duration of any given experiment is quite limited, particularly in neuroimaging contexts, and therefore robust estimates of multiple behavioral domains are often difficult to achieve. Here we offer a "turn-key" emotion-evoking paradigm suitable for neuroimaging experiments that demonstrates strong effect sizes across widespread cortical and subcortical structures. This short series could be easily added to existing fMRI protocols, and yield a reliable estimate of emotional reactivity to complement research in other behavioral domains. This experimental adjunct could be used to enable an initial comparison of emotional modulation with the primary behavioral focus of an investigator's work, and potentially identify new relationships between domains of behavior that have not previously been recognized.

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 effects of a single aerobic exercise session on mood and neural emotional reactivity in depressed and healthy young adults: A late positive potential study

Depression has been characterized by lowered mood and unfavorable changes in neural emotional reactivity (altered brain responses to emotional stimuli). Physical exercise is a well-established strategy to improve the mood of healthy and depressed individuals. Increasing evidence suggests that exercise might also improve emotional reactivity in healthy adults by increasing or decreasing brain responses to positive or negative stimuli, respectively. It is unknown, however, if exercise could also benefit emotional reactivity in depressed individuals. We investigated the effects of a single aerobic exercise session on mood and emotional reactivity in 24 depressed and 24 matched healthy young adults. Self-reported mood and neural reactivity to emotional pictures (indexed by the EEG late positive potential, LPP) were assessed before and after two experimental protocols: exercise (36 min of moderate-intensity exercise at 75% of maximal heart rate) and seated rest condition (36 min). In the healthy control group, exercise improved self-reported mood and neural emotional reactivity (increasing LPP to positive pictures). In the depressed group, exercise improved self-reported mood; however, it did not affect neural emotional reactivity. Additional analyses performed on both groups revealed that exercise-induced changes in emotional reactivity are associated with the severity of depressive symptoms: the effectiveness of exercise in improving emotional reactivity decreases with the severity of depressive symptoms. Overall, the study further strengthens the claim of a beneficial role of exercise on mood and emotional reactivity. It also suggests that a single aerobic exercise session might have a limited influence on neural emotional reactivity in depressed individuals.

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.

Feasibility of Combining Transcranial Direct Current Stimulation and Active Fully Embodied Virtual Reality for Visual Height Intolerance: A Double-Blind Randomized Controlled Study

BACKGROUND

Transcranial Direct Current Stimulation (tDCS) and Virtual Reality Exposure Therapy (VRET) are individually increasingly used in psychiatric research.

OBJECTIVE/HYPOTHESIS

Our study aimed to investigate the feasibility of combining tDCS and wireless 360° full immersive active and embodied VRET to reduce height-induced anxiety.

METHODS

We carried out a pilot randomized, double-blind, controlled study associating VRET (two 20 min sessions with a 48 h interval, during which, participants had to cross a plank at rising heights in a building in construction) with online tDCS (targeting the ventromedial prefrontal cortex) in 28 participants. The primary outcomes were the sense of presence level and the tolerability. The secondary outcomes were the anxiety level (Subjective Unit of Discomfort) and the salivary cortisol concentration.

RESULTS

We confirmed the feasibility of the association between tDCS and fully embodied VRET associated with a good sense of presence without noticeable adverse effects. In both groups, a significant reduction in the fear of height was observed after two sessions, with only a small effect size of add-on tDCS (0.1) according to the SUD. The variations of cortisol concentration differed in the tDCS and sham groups.

CONCLUSION

Our study confirmed the feasibility of the association between wireless online tDCS and active, fully embodied VRET. The optimal tDCS paradigm remains to be determined in this context to increase effect size and then adequately power future clinical studies assessing synergies between both techniques.

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.

Trauma-related dysfunction in the fronto-striatal reward circuit

INTRODUCTION

Reduced reactivity to pleasurable stimulation is a defining symptom of post-traumatic stress disorder (PTSD), but trauma exposure also increases the severity of many anxiety and mood disorders, including depression, social anxiety, and panic disorder, suggesting that reward system dysfunction might be pervasive in the internalizing disorders. The ventromedial prefrontal cortex (vmPFC) and ventral striatum are core components of the reward circuit and the current study assesses functional activity and connectivity in this circuit during emotional picture viewing in anxiety and mood disorder patients.

METHOD

Functional brain activity (fMRI) and functional connectivity in the fronto-striatal circuit were measured in a large sample of patients diagnosed with anxiety and mood disorders (n=155) during affective scene viewing as it varied with trauma exposure and temperament.

RESULTS

In women, but not men, blunted fronto-striatal connectivity was associated with increased posttraumatic anhedonic symptoms, whereas the amplitude of functional activity was not related to trauma exposure. In both men and women, reduced fronto-striatal connectivity was associated with decreases in temperamental positive affect. When predicting fronto-striatal connectivity, temperament and posttraumatic symptomology accounted for independent proportions of variance.

LIMITATIONS

In this civilian sample of anxiety disorder patients, men reported very little trauma-related symptomology.

CONCLUSIONS

Because dysfunctional reward processing due to trauma and temperament is pervasive across the internalizing disorder spectrum, assessing the integrity of the fronto-striatal reward circuit could provide important information in diagnostic and treatment protocols.

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.

Low-intensity pulsed ultrasound ameliorates depression-like behaviors in a rat model of chronic unpredictable stress

Introduction

There is an unmet need for better nonpharmaceutical treatments for depression. Low‐intensity pulsed ultrasound (LIPUS) is a novel type of neuromodulation that could be helpful for depressed patients.

Objective

The goal of this study was to investigate the feasibility and potential mechanisms of LIPUS in the treatment of depression.

Methods

Chronic unpredictable stress (CUS) was used to generate rats with depression‐like features that were treated with four weeks of LIPUS stimulation of the ventromedial prefrontal cortex. Depression‐like behaviors were assessed with the sucrose preference, forced swim, and open field tests. BDNF/mTORC1 signaling was examined by Western blot to investigate this potential molecular mechanism. The safety of LIPUS was evaluated using hematoxylin‐eosin and Nissl staining.

Results

Four weeks of LIPUS stimulation significantly increased sucrose preference and reduced forced swim immobility time in CUS rats. LIPUS also partially reversed the molecular effects of CUS that included decreased levels of BDNF, phosphorylated tyrosine receptor kinase B (TrkB), extracellular signal‐regulated kinase (ERK), mammalian target of rapamycin complex 1 (mTORC1), and S6 kinase (S6K). Moreover, histological staining revealed no gross tissue damage.

Conclusions

Chronic LIPUS stimulation can effectively and safely improve depression‐like behaviors in CUS rats. The underlying mechanisms may be related to enhancement of BDNF/ERK/mTORC1 signaling pathways in the prefrontal cortex (PFC). LIPUS is a promising noninvasive neuromodulation tool that merits further study as a potential treatment for depression.

Alexithymia and the Evaluation of Emotionally Valenced Scenes

Alexithymia is a personality trait characterized by difficulties identifying and describing feelings (DIF and DDF) and an externally oriented thinking (EOT) style. The primary aim of the present study was to investigate links between alexithymia and the evaluation of emotional scenes. We also investigated whether viewers' evaluations of emotional scenes were better predicted by specific alexithymic traits or by individual differences in sensory processing sensitivity (SPS). Participants (N = 106) completed measures of alexithymia and SPS along with a task requiring speeded judgments of the pleasantness of 120 moderately arousing scenes. We did not replicate laterality effects previously described with the scene perception task. Compared to those with weak alexithymic traits, individuals with moderate-to-strong alexithymic traits were less likely to classify positively valenced scenes as pleasant and were less likely to classify scenes with (vs. without) implied motion (IM) in a way that was consistent with normative scene valence ratings. In addition, regression analyses confirmed that reporting strong EOT and a tendency to be easily overwhelmed by busy sensory environments negatively predicted classification accuracy for positive scenes, and that both DDF and EOT negatively predicted classification accuracy for scenes depicting IM. These findings highlight the importance of accounting for stimulus characteristics and individual differences in specific traits associated with alexithymia and SPS when investigating the processing of emotional stimuli. Learning more about the links between these individual difference variables may have significant clinical implications, given that alexithymia is an important, transdiagnostic risk factor for a wide range of psychopathologies.

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.

Efficacy of an Integrative Treatment for Tinnitus Combining Music and Cognitive-Behavioral Therapy-Assessed With Behavioral and EEG Data

Chronic tinnitus is a prevalent condition that could cause severe negative impact on an individual's life. However, there has not been an established treatment due to a limited understanding of the pathophysiology of this multifarious disorder. In this study, we tested the efficacy of an integrative treatment, combining music therapy with cognitive-behavioral therapy (CBT). We collected three groups of patients receiving three different treatments: Music-CBT, music therapy and CBT. We used both subjective (i.e., questionnaires) and objective (i.e., resting-state EEG data) measurements to assess the behavioral and neural changes brought upon by the treatments. Analyses of the subjective measurements found a significant improvement of scale scores in Music-CBT and CBT, but not in the Music group. Analysis of the EEG data further showed increased powers in alpha and theta band after the Music-CBT treatment, and increased gamma power after CBT, whereas no significant difference was found for the music therapy. Further source localization analysis of alpha and theta changes in the Music-CBT group found that primary sources of the changes were located at auditory processing regions such as superior temporal gyrus, and higher emotional and cognitive processing regions such as ventromedial prefrontal cortex (vMPFC), lateral prefrontal cortex and parahippocampus. These results indicated that Music-CBT was effective in improving tinnitus symptoms on both a behavioral and neural level, which is more robust than the music therapy or CBT alone.

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.

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.

Deactivation of the prefrontal cortex during exposure to pleasantly-charged emotional challenge

Our laboratory reported that facial skin blood flow may serve as a sensitive tool to assess an emotional status and that both prefrontal oxygenation (as index of regional cerebral blood flow) and facial skin blood flow decrease during positively-charged emotional stimulation, without changing hand skin blood flow and arterial pressure. However, the focal location of the prefrontal responses in concentration of oxygenated haemoglobin (Oxy-Hb) that correlate with peripheral autonomic reaction remained unknown. This study was undertaken using 22-channel near-infrared spectroscopy to reveal spatial distribution of the responses in Oxy-Hb within the prefrontal cortex (PFC) during emotionally-charged audiovisual stimulation. Pleasantly-charged (comedy) stimulation caused a substantial decrease of Oxy-Hb in all regions of the PFC in 18 subjects, especially in the rostroventral frontopolar PFC, whereas negatively-charged (horror) or neutral stimulation (landscape) exhibited a weaker decrease or insignificant change in the prefrontal Oxy-Hb. In the rostral parts of the dorsolateral and ventral frontopolar PFC, the oxygenation response during comedy stimulation exhibited the most significant positive correlation with the decrease in facial skin blood flow. Thus the rostral regions of the PFC play a role in recognition and regulation of positive emotion and may be linked with neurally-mediated vasoconstriction of facial skin blood vessels.

Prefrontal oxygenation correlates to the responses in facial skin blood flows during exposure to pleasantly charged movie

Our laboratory reported that facial skin blood flow may serve as a sensitive tool to assess an emotional status. Cerebral neural correlates during emotional interventions should be sought in relation to the changes in facial skin blood flow. To test the hypothesis that prefrontal activity has positive relation to the changes in facial skin blood flow during emotionally charged stimulation, we examined the dynamic changes in prefrontal oxygenation (with near‐infrared spectroscopy) and facial skin blood flows (with two‐dimensional laser speckle and Doppler flowmetry) during emotionally charged audiovisual challenges for 2 min (by viewing comedy, landscape, and horror movie) in 14 subjects. Hand skin blood flow and systemic hemodynamics were simultaneously measured. The extents of pleasantness and consciousness for each emotional stimulus were estimated by subjective rating from −5 (the most unpleasant; the most unconscious) to +5 (the most pleasant; the most conscious). Positively charged emotional stimulation (comedy) simultaneously decreased (P < 0.05) prefrontal oxygenation and facial skin blood flow, whereas negatively charged (horror) or neutral (landscape) emotional stimulation did not alter or slightly decreased them. Any of hand skin blood flow and systemic cardiovascular variables did not change significantly during positively charged emotional stimulation. The changes in prefrontal oxygenation had a highly positive correlation with the changes in facial skin blood flow without altering perfusion pressure, and they were inversely correlated with the subjective rating of pleasantness. The reduction in prefrontal oxygenation during positively charged emotional stimulation suggests a decrease in prefrontal neural activity, which may in turn elicit neurally mediated vasoconstriction of facial skin blood vessels.

Neuropsychopharmacological aesthetics: A theoretical consideration of pharmacological approaches to causative brain study in aesthetics and art

Recent developments in neuroaesthetics have heightened the need for causative approaches to more deeply understand the mechanism underlying perception, emotion, and aesthetic experiences. This has recently been the topic for empirical work, employing several causative methods for changing brain activity, as well as comparative assessments of individuals with brain damage or disease. However, one area of study with high potential, and indeed a long history of often nonscientific use in the area of aesthetics and art, employing psychopharmacological chemicals as means of changing brain function, has not been systematically utilized. This chapter reviews the literature on this topic, analyzing neuroendocrinological (neurochemical) approaches and mechanisms that might be used to causatively study the aesthetic brain. We focus on four relevant neuromodulatory systems potentially related to aesthetic experience: the dopaminergic, serotonergic, cannabinoid, and the opioidergic system. We build a bridge to psychopharmacological methods and review drug-induced behavioral and neurobiological consequences. We conclude with a discussion of hypotheses and suggestions for future research.

Modulating Emotional Experience Using Electrical Stimulation of the Medial-Prefrontal Cortex: A Preliminary tDCS-fMRI Study

OBJECTIVES

Implicit regulation of emotions involves medial-prefrontal cortex (mPFC) regions exerting regulatory control over limbic structures. Diminished regulation relates to aberrant mPFC functionality and psychopathology. Establishing means of modulating mPFC functionality could benefit research on emotion and its dysregulation. Here, we tested the capacity of transcranial direct current stimulation (tDCS) targeting mPFC to modulate subjective emotional states by facilitating implicit emotion regulation.

MATERIALS AND METHODS

Stimulation was applied concurrently with functional magnetic resonance imaging to validate its neurobehavioral effect. Sixteen participants were each scanned twice, counterbalancing active and sham tDCS application, while undergoing negative mood induction (clips featuring negative vs. neutral contents). Effects of stimulation on emotional experience were assessed using subjective and neural measures.

RESULTS

Subjectively, active stimulation led to significant reduction in reported intensity of experienced emotions to negatively valenced (p = 0.005) clips but not to neutral clips (p > 0.99). Active stimulation further mitigated a rise in stress levels from pre- to post-induction (sham: p = 0.004; active: p = 0.15). Neurally, stimulation increased activation in mPFC regions associated with implicit emotion regulation (ventromedial-prefrontal cortex; subgenual anterior-cingulate cortex, sgACC), and in ventral striatum, a core limbic structure (all ps < 0.05). Stimulation also altered functional connectivity (assessed using whole-brain psycho-physiological interaction) between these regions, and with additional limbic regions. Stimulation-induced sgACC activation correlated with reported emotion intensity and depressive symptoms (rs > 0.64, ps < 0.018), suggesting individual differences in stimulation responsivity.

CONCLUSIONS

Results of this study indicate the potential capacity of tDCS to facilitate brain activation in mPFC regions underlying implicit regulation of emotion and accordingly modulate subjective emotional experiences.

Noninvasive stimulation of the ventromedial prefrontal cortex modulates emotional face processing

The ventromedial prefrontal cortex (vmPFC) is associated with emotional states that can be characterized as positive affect. Moreover, a variety of psychiatric disorders that are associated with disturbed reactions toward reward- or safety-signaling stimuli reveal functional or structural anomalies within this area. Thus, neuromodulation of this region via transcranial direct current stimulation (tDCS) offers an attractive opportunity to noninvasively influence pleasant emotional and reward processing. Recent experiments revealed hemodynamic and electrophysiological evidence for valence specific modulations of emotional scene processing after excitatory and inhibitory tDCS of the vmPFC. Here, we identified that tDCS modulation of vmPFC during emotional face processing results in effects convergent with scene processing, in that excitatory tDCS increased neural reactivity during happy compared to fearful face perception, whereas inhibitory stimulation led to a converse effect. In addition, behavioral data (affect identification of ambiguous expressive faces) revealed a bias toward preferential processing of happy compared to fearful faces after excitatory compared to after inhibitory stimulation. These results further support the vmPFC as an appropriate target for noninvasive neuromodulation of an appetitive processing network in patients suffering from disturbed cognition of reward- and safety-signaling stimuli. It should however be noted that electrophysiological pre-tDCS differences at earlier time intervals of emotional face and scene processing appeared amplified by tDCS, which remains to be investigated.

Modulating Emotion Perception: Opposing Effects of Inhibitory and Excitatory Prefrontal Cortex Stimulation

BACKGROUND

Excitatory repetitive transcranial magnetic stimulation (rTMS) of the left dorsolateral prefrontal cortex (dlPFC) is approved by the U.S. Food and Drug Administration for the treatment of adult patients with treatment-resistant major depressive disorder (MDD). This stimulation is supposed to restore excitability of prefrontal cortex regions that exhibit diminished regulation of emotion-generative systems in MDD. Based on the valence lateralization hypothesis, inhibitory rTMS of the right dlPFC has also been applied in MDD. This approach has proved to be effective, although meta-analyses of emotional perception and affective regulation in healthy control subjects and patients with depression do not support functional asymmetries within dlPFC regions.

METHODS

To shed more light on this discrepancy, the effects of excitatory and inhibitory rTMS of the right dlPFC on visual emotional perception were compared in two groups of 41 healthy participants overall. Before and after rTMS stimulation, participants viewed fearful and neutral faces while whole-head magnetoencephalography was recorded and supplemented by behavioral tests.

RESULTS

Visual sensory processing of fearful facial expressions, relative to neutral facial expressions, was reduced after excitatory stimulation and was increased after inhibitory stimulation within right occipital and right temporal regions. Correspondingly, after excitatory rTMS compared with inhibitory rTMS, participants displayed relatively reduced reaction times in an emotion discrimination task and showed reduced emotional arousal.

CONCLUSIONS

These results support the hypothesis that excitatory rTMS compared with inhibitory rTMS of the right dlPFC strengthens top-down control of aversive stimuli in healthy control subjects, which should encourage more research on mechanisms of excitatory/inhibitory dlPFC-rTMS protocols in general and on neuromodulatory treatment of MDD.

Recent Advances in Non-invasive Brain Stimulation for Major Depressive Disorder

Non-invasive brain stimulation (NBS) is a promising treatment for major depressive disorder (MDD), which is an affective processing disorder involving abnormal emotional processing. Many studies have shown that repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) over the prefrontal cortex can play a regulatory role in affective processing. Although the clinical efficacy of NBS in MDD has been demonstrated clinically, the precise mechanism of action remains unclear. Therefore, this review article summarizes the current status of NBS methods, including rTMS and tDCS, in the treatment of MDD. The article explores possible correlations between depressive symptoms and affective processing, highlighting the relevant affective processing mechanisms. Our review provides a reference for the safety and efficacy of NBS methods in the clinical treatment of MDD.