The relationship of approach/avoidance motivation and asymmetric frontal cortical activity: A review of studies manipulating frontal asymmetry

Frontal alpha asymmetry dynamics: A window into active self-regulatory processes

Frontal Alpha Asymmetry (FAA) has been studied since the late 1970s as a neural correlate of emotion regulation and motivational processes. FAA is often viewed through a dispositional lens reflecting individual differences in positive or negative emotionality and biases toward approach or avoidance motivational processes. However, FAA also shifts in response to context-specific conditions that elicit approach or avoidance responses, indicating FAA reflects active, ongoing self-regulatory processes. Moreover, FAA changes over time, and how it changes over time is affected by context, experience, and development. We propose FAA evolves over four different time scales including the (1) second-to-second, (2) laboratory task, (3) intervention or intensive learning experience, and (4) developmental time scales. We present evidence showing FAA evolves over each of these time scales and highlight influences of individual differences and the developmental context on how FAA changes over time. We emphasize the insights gained by studying change in FAA over each time scale. We concluded with recommendations about future directions and speculate about the nested, bidirectional nature of the four timescales.

Greater weekly physical activity linked to left resting frontal alpha asymmetry in women: A study on gender differences in highly active young adults

Physical activity, beneficial for physical and psychological health, may facilitate affective mechanisms of positive emotion and approach-motivation. Greater resting frontal alpha asymmetry (FAA), an index of greater relative left than right frontal cortical activity, is a neural correlate of affective mechanisms possibly associated with active lifestyles. This study sought to amplify limited literature on the relationship between physical (in)activity, FAA, and gender differences. College students (n = 70) self-reported physical activity (Total PA) and sedentary activity (Total Sitting) via the International Physical Activity Questionnaire-Short Form (IPAQ-SF), followed by a resting electroencephalography session to record FAA. A Total PA × gender interaction (β = 0.462, t = 3.163, p = 0.002) identified a positive relationship between Total PA and FAA in women (β = 0.434, t = 2.221, p = 0.030) and a negative relationship for men (β = -0.338, t = -2.300, p = 0.025). Total Sitting was positively linked to FAA (β = 0.288, t = 2.228, p = 0.029; no gender effect). Results suggest affective mechanisms reflected by FAA (e.g., positive emotion, approach-motivation) are associated with physical activity for women, indicating a possible mechanism of the psychological benefits linked with physically active lifestyles. A positive relationship between sedentary behavior and greater left FAA may also reflect motivated mechanisms of behavior that aid in minimizing energy expenditure, particularly within the context of our highly active sample.

Mindfulness and mechanisms of attention in a neutral and palatable food context

Introduction

Mindfulness has been associated with benefits on cognitive processes, including attention. However, the exact relationship between mindfulness, components of attention, and the role of reward context has not yet been fully elucidated, which is relevant, especially in the context of addiction. In the current study, we specifically evaluated the relationship between dispositional mindfulness and the balance between voluntary (top-down), and stimulus-driven (bottom-up) attention. In addition, we explored whether the relationship was mediated by asymmetry of frontal brain activity, an index of approach tendencies, and varies as a function of reward context.

Methods

In total, 95 participants (30 male, 65 female) with a mean age of 25.87 (SD = 7.38) participated. Resting-state electrophysiological activity was recorded using EEG, and participants were assessed on dispositional mindfulness, and performed the visuospatial cueing (VSC) task, which indexed voluntary- and stimulus-driven attention in a neutral and palatable food (reward) context. In the endogenous VSC task, a central cue signals the likely location of a subsequent target. The validity effect represents the benefit of valid cueing relative to the costs of invalid cueing in terms of response time.

Results and discussion

Dispositional mindfulness was associated with a reduced validity effect, plausibly reflecting a combination of reduced voluntary attention and increased stimulus-driven attention, irrespective of condition. The relationship between dispositional mindfulness and visuospatial attention could not be explained by asymmetry of frontal brain activity.

Cerebellar Asymmetry of Motivational Direction: Anger-Dependent Effects of Cerebellar Transcranial Direct Current Stimulation on Aggression in Healthy Volunteers

It has recently been theorized that the frontal asymmetry of approach- and avoidance-related motivation is mirrored in the posterolateral cerebellum. Accordingly, left-to-right dominant cerebellar activity is associated with avoidance-related motivation, whereas right-to-left dominant cerebellar activity is associated with approach-related motivation. The aim of this study was to examine the cerebellar asymmetry of motivational direction in approach-related behavior in the context of aggression. In this randomized double-blind sham-controlled crossover study, thirty healthy right-handed adult volunteers received 2 mA active or sham left cathodal-right anodal transcranial direct current stimulation (tDCS) to the cerebellum on two separate occasions while engaging in the Point Subtraction Aggression Paradigm (PSAP) task to measure aggressive behavior. Self-reported state anger was assessed before, halfway and immediately after the task, and heart rate and heart rate variability (HRV) were measured during the task. No main effects of tDCS on aggressive behavior, heart rate and HRV were found. Higher state anger before and during the PSAP task was associated with increased aggressive behavior in the active compared to sham tDCS condition. Aggressive behavior was positively correlated with heart rate during active tDCS, while an inverse association was observed during sham tDCS. Results provide support for the cerebellar asymmetry of motivational direction in approach-related behavior and illustrate the importance of affective state-dependency in tDCS-related effects.

The relationship between frontal alpha asymmetry and behavioral and brain activity indices of reactive inhibitory control

Reactive inhibitory control plays an important role in phenotype of different diseases/different phases of a disease. One candidate electrophysiological marker of inhibitory control is frontal alpha asymmetry (FAA). FAA reflects the relative difference in contralateral frontal brain activity. However, the relationship between FAA and potential behavioral/brain activity indices of reactive inhibitory control is not yet clear. We assessed the relationship between resting-state FAA and indicators of reactive inhibitory control. Additionally, we investigated the effect of modulation of FAA via transcranial direct current stimulation (tDCS). We implemented a randomized sham-controlled design with 65 healthy humans (Mage = 23.93, SDage = 6.08; 46 female). Before and after 2-mA anodal tDCS of the right frontal site (with the cathode at the contralateral site) for 20 min, we collected EEG data and reactive inhibitory performance in neutral and food-reward conditions, using the stop signal task (SST). There was no support for the effect of tDCS on FAA or any indices of reactive inhibitory control. Our correlation analysis revealed an association between inhibitory brain activity in the food-reward condition and (pre-tDCS) asymmetry. Higher right relative to left frontal brain activity was correlated with reduced early-onset inhibitory activity and, in contrast, linked with higher late-onset inhibitory control in the food-reward condition. Similarly, event-related potential analyses showed reduced early-onset and enhanced late-onset inhibitory brain activity over time, particularly in the food-reward condition. These results suggest that there can be a dissociation regarding the lateralization of frontal brain activity and early- and late-onset inhibitory brain activity.NEW & NOTEWORTHY This research reveals dissociation between baseline frontal alpha asymmetry and the timing of reactive inhibitory brain activities in food-reward contexts. Whereas inhibitory control performance decreases over time in a stop signal task, electrophysiological indices show reduced early- and heightened late-onset inhibitory brain activity, especially in the reward condition. Additionally, greater right frontal activity correlates with reduced early-onset and increased late-onset inhibitory brain activity.

Contrasting frontal cortical responses to food versus money rewards across BMI groups

Previous research has linked obesity with an altered perception of rewards. This study aimed to contrast frontal cortical activities across body mass index (BMI) groups, in responding to differential rewards (monetary versus food). A total of 60 male participants (27.43 ± 6.07 years of age; 21 normal weight [BMI: 18.5-24.9 kg·m-2]; 20 overweight [BMI: 25.0-29.9 kg·m-2]; and 19 individuals with obesity [BMI ≥ 30 kg·m-2]) were tested for their response bias towards food and money rewards using the Probabilistic Reward Task (PRT), while their frontal cortical responses were recorded using electroencephalography (EEG). The feedback-related negativity (FRN), a reliable measure of reward valuation and learning, was calculated for food (FRN(Food)) and money (FRN(Money)). Results indicate a left-lateralised frontal cortical activity associated with the food reward condition, in the group of overweight and obesity. In contrast, a right-lateralisation was observed in the money reward condition only in the group with obesity. More specifically, FRN(Food) was shown to significantly differ between left and right frontal cortical areas among individuals with obesity (p = 0.035) and overweight (p = 0.012), but not in normal-weight individuals (p = 0.153). Additionally, results revealed that FRN(Food) and FRN(Money) were significantly different for individuals with obesity (p = 0.019), but such a significant difference was not evident in the overweight and normal-weight individuals (p ≥ 0.05). These findings offer intriguing new insights into neuropsychological differentiation across BMI groups, adding to the understanding of obesity-related behaviour.

Cognitive enhancing effect of rTMS combined with tDCS in patients with major depressive disorder: a double-blind, randomized, sham-controlled study

BACKGROUND

Cognitive dysfunction is one of the common symptoms in patients with major depressive disorder (MDD). Repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) have been studied separately in the treatment of cognitive dysfunction in MDD patients. We aimed to investigate the effectiveness and safety of rTMS combined with tDCS as a new therapy to improve neurocognitive impairment in MDD patients.

METHODS

In this brief 2-week, double-blind, randomized, and sham-controlled trial, a total of 550 patients were screened, and 240 MDD inpatients were randomized into four groups (active rTMS + active tDCS, active rTMS + sham tDCS, sham rTMS + active tDCS, sham rTMS + sham tDCS). Finally, 203 patients completed the study and received 10 treatment sessions over a 2-week period. The Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) was performed to assess patients' cognitive function at baseline and week 2. Also, we applied the 24-item Hamilton Depression Rating Scale (HDRS-24) to assess patients' depressive symptoms at baseline and week 2.

RESULTS

After 10 sessions of treatment, the rTMS combined with the tDCS group showed more significant improvements in the RBANS total score, immediate memory, and visuospatial/constructional index score (all p < 0.05). Moreover, post hoc tests revealed a significant increase in the RBANS total score and Visuospatial/Constructional in the combined treatment group compared to the other three groups but in the immediate memory, the combined treatment group only showed a better improvement than the sham group. The results also showed the RBANS total score increased significantly higher in the active rTMS group compared with the sham group. However, rTMS or tDCS alone was not superior to the sham group in terms of other cognitive performance. In addition, the rTMS combined with the tDCS group showed a greater reduction in HDRS-24 total score and a better depression response rate than the other three groups.

CONCLUSIONS

rTMS combined with tDCS treatment is more effective than any single intervention in treating cognitive dysfunction and depressive symptoms in MDD patients.

TRIAL REGISTRATION

Chinese Clinical Trial Registry (ChiCTR2100052122).

Frontal alpha asymmetry is associated with chronic stress and depression, but not with somatoform disorders

Cardinal characteristics of somatoform disorders (SFDs) are worry of illness, and impaired affective processing. We used relative frontal alpha asymmetry (FAA), a method to measure functional lateralization of affective processing, to investigate psychobiological correlates of SFDs. With alpha activity being inversely related to cortical network activity, relative FAA refers to alpha activity on the right frontal lobe minus alpha activity on the left frontal lobe. Less relative left frontal activity, reflected by negative FAA scores, is associated with lower positive and greater negative affectivity, such as observed in depression. Due to its negative affective component (illness anxiety), we expected to find less relative left frontal activity pattern in SFDs, and positive associations with self-reported chronic stress and depression symptoms. We recorded resting-state EEG activity with 64 electrodes, placed in a 10-10 system in 26 patients with a primary SFD, 23 patients with a major depressive disorder and 25 healthy control participants. The groups did not differ in FAA. Nevertheless, across all participants, less relative left frontal activity was associated with chronic stress and depression symptoms. We concluded that FAA may not serve as an indicator of SFDs. As the relationship of FAA and depressive symptoms was fully mediated by chronic stress, future studies have to clarify whether the association between FAA and chronic stress may represent a shared underlying factor for the manifestation of mental health complaints, such as depression.

Cross-hemispheric communication: Insights on lateralized brain functions

On the surface, the two hemispheres of vertebrate brains look almost perfectly symmetrical, but several motor, sensory, and cognitive systems show a deeply lateralized organization. Importantly, the two hemispheres are connected by various commissures, white matter tracts that cross the brain's midline and enable cross-hemispheric communication. Cross-hemispheric communication has been suggested to play an important role in the emergence of lateralized brain functions. Here, we review current advances in understanding cross-hemispheric communication that have been made using modern neuroscientific tools in rodents and other model species, such as genetic labeling, large-scale recordings of neuronal activity, spatiotemporally precise perturbation, and quantitative behavior analyses. These findings suggest that the emergence of lateralized brain functions cannot be fully explained by largely static factors such as genetic variation and differences in structural brain asymmetries. In addition, learning-dependent asymmetric interactions between the left and right hemispheres shape lateralized brain functions.

The association of maternal-infant interactive behavior, dyadic frontal alpha asymmetry, and maternal anxiety in a smartphone-adapted still face paradigm

Mother-infant interactions form a strong basis for emotion regulation development in infants. These interactions can be affected by various factors, including maternal postnatal anxiety. Electroencephalography (EEG) hyperscanning allows for simultaneous assessment of mother-infant brain-to-behavior association during stressful events, such as the still-face paradigm (SFP). This study aimed at investigating dyadic interactive behavior and brain-to-behavior association across SFP and identifying neural correlates of mother-infant interactions in the context of maternal postnatal anxiety. We measured frontal alpha asymmetry (FAA), a physiological correlate of emotion regulation and a potential marker of risk for psychopathology. To emulate real-life interactions, EEG and behavioral data were collected from 38 mother-infant dyads during a smartphone-adapted dual-SFP. Although the behavioral data showed a clear still-face effect for the smartphone-adapted SFP, this was not reflected in the infant or maternal FAA. Brain-to-behavior data showed higher infant negative affect being associated with more infant leftward FAA during the still-face episodes. Finally, mothers with higher postnatal anxiety showed more right FAA during the first still-face episode, suggesting negative affectivity and a need to withdraw from the situation. Our results form a baseline for further research assessing the effects of maternal postnatal anxiety on infants' FAA and dyadic interactive behavior.

COVID-19 pandemic impacts on the elderly: the relationship between PPPD and prefrontal alpha rhythm

BACKGROUND

In the COVID-19 epidemic more patients presented with persistent postural-perceptual dizziness (PPPD), but it has received little attention by the doctors in China and many patients reject psychological measurements or scales. Therefore, there is an urgent need for an objective method to diagnose and evaluate PPPD.

OBJECTIVE

To investigate the effect of the COVID-19 epidemic on elderly PPPD patients and define the relationship between prefrontal alpha rhythm asymmetry (FAA) by Electroencephalography (EEG) and PPPD.

METHODS

This case-control study was conducted to discuss the differences of elderly outpatients (>60 years) with PPPD during the peak period of COVID-19 in 2020 and the corresponding period in 2019, and collect the prefrontal FAA value in PPPD during COVID-19 outbreak, which were compared to its FAA in healthy control.

RESULTS

Compared with the same period in 2019, the number of elderly PPPD patients during the epidemic period in 2020 increased significantly (16.4%, p = 0.000, x2 =31.802) . The left alpha wave signal power (F3) was significantly higher than the right alpha wave signal power (F4) (Z= -3.073, p = 0.002). In PPPD patients FAA were significantly lower in patients compared to control group (Z = -11.535, p = 0.000). There was a negative correlation between FAA and HAMA scores (R2 =0.906, p < 0.05) and a negative correlation between FAA and HAMD scores (R2 =0.859, p < 0.05), too.

CONCLUSIONS

The increase in cases of elderly PPPD patients is most likely attributed to the mental health in older adults during the COVID-19 pandemic. Less left frontal brain activity in EEG may be related to elderly PPPD.

The Effect of Induced Regulatory Focus on Frontal Cortical Activity

The motivation-direction model has served as the primary framework for understanding frontal cortical activity. However, research on the link between approach/avoidance motivation and left/right frontal cortical activity has produced inconsistent findings. Recent studies suggest that regulatory systems may offer a more accurate explanation than the motivational direction model. Despite being regulatory systems, the relationship between regulatory focus and frontal cortical activity has received limited attention. Only one experimental study has explored this connection through correlational analysis, yet it lacks causal evidence. The present study aimed to address this gap by manipulating regulatory focus and measuring frontal cortical activity in 36 college students. Our results revealed that induced promotion focus led to increased left frontal cortical activity, whereas induced prevention focus led to increased right frontal cortical activity. These findings enhance our physiological understanding of regulatory focus and offer a deeper explanation of how regulatory focus influences alterations in psychology and behavior.

Frontal P300 asymmetry and congruence judgment: Retroactive switching is impaired during school day mornings in female adolescents

Investigating frontal EEG asymmetry as a possible biomarker of cognitive control abilities is especially important in ecological contexts such as school and work. We used a novel approach combining judgment performance and hemispheric frontal event-related potential (ERP) P300 asymmetry (fP3As) to evaluate aspects of cognitive control (i.e., repetition and switching) in adolescent females over a two-week ordinary school period. While undergoing electroencephalographic recording, students performed a word-colour "Stroop-like" congruence judgment task during morning and afternoon sessions, on Mondays and Wednesdays. Proportion of incongruence and congruence trials was 75% and 25%, respectively. ERP analysis revealed larger "novelty" right hemispheric fP3As amplitude for infrequent congruence but equivalent or significantly smaller than left hemispheric fP3As amplitude for frequent incongruence. RTs increased with extent of right fP3As shift. Behaviorally, repeat trial pairs (i.e., congruent followed by congruent, incongruent followed by incongruent) generally did not differ by time or day and were associated with near-ceiling accuracy. In contrast, switch trial pairs (i.e., congruent followed by incongruent, incongruent followed by congruent) in the afternoon were slower and associated with lower accuracy at the expected 75% criterion rate (i.e., judging incongruence by default), dropping significantly below 75% in the mornings. Crucially, compared to afternoon, morning fP3As patterns did not change adaptively with switch trial pairs. Although retroactive switching during congruence judgment was affected at all testing times, we conclude it was most impaired in the mornings of both early and mid school weeks, supporting misalignment between adolescent circadian cycle and school start time. We discuss some implications for optimal learning of adolescents at school.

Learning to be inventive in the face of statistics: A positive reappraisal intervention for statistics anxiety

BACKGROUND AND OBJECTIVES

The burden of statistics anxiety on students calls for effective interventions. This study investigated whether a cognitive reappraisal training designed to stimulate the generation of positive re-interpretations may yield behavioral changes in anxiety measures and changes in cerebral activation patterns reflecting the activation of approach/avoidance motivational tendencies (frontal EEG alpha asymmetry response).

METHODS

Three groups of female psychology students (n = 45) with statistics anxiety were tested. Two groups received a guided, two-week reappraisal training with either statistics-anxiety or general anxiety situations; the control group received no intervention.

RESULTS

Both training groups significantly increased their amount of positive re-interpretations from pre-to post-test compared to the control group. Increased habitual use of reappraisal in statistics situations and significant EEG changes reflecting more approach-oriented coping with anxiety occurred in the statistics-anxiety training group only. No changes in statistics anxiety and statistics attitudes were observed, suggesting that the training effects, though corroborated through neurophysiological changes, did not sufficiently translate to improving students' deep-rooted anxiety.

LIMITATIONS

Effects, though robust and following the same pattern, were observed in a small sample.

CONCLUSIONS

Our findings delineate a promising expandable approach for helping students' cope with statistics anxiety in a healthier way.

Investigation of different ML approaches in classification of emotions induced by acute stress

Background

Machine learning is becoming a common tool in monitoring emotion. However, methodological studies of the processing pipeline are scarce, especially ones using subjective appraisals as ground truth.

New method

A novel protocol was used to induce cognitive load and physical discomfort, and emotional dimensions (arousal, valence, and dominance) were reported after each task. The performance of five common ML models with a versatile set of features (physiological features, task performance data, and personality trait) was compared in binary classification of subjectively assessed emotions.

Results

The psychophysiological responses proved the protocol was successful in changing the mental state from baseline, also the cognitive and physical tasks were different. The optimization and performance of ML models used for emotion detection were evaluated. Additionally, methods to account for imbalanced classes were applied and shown to improve the classification performance.

Comparison with existing methods

Classification of human emotional states often assumes the states are determined by the stimuli. However, individual appraisals vary. None of the past studies have classified subjective emotional dimensions with a set of features including biosignals, personality and behavior.

Conclusion

Our data represent a typical setup in affective computing utilizing psychophysiological monitoring: N is low compared to number of features, inter-individual variability is high, and class imbalance cannot be avoided. Our observations are a) if possible, include features representing physiology, behavior and personality, b) use simple models and limited number of features to improve interpretability, c) address the possible imbalance, d) if the data size allows, use nested cross-validation.

Electroencephalography findings in menstrually-related mood disorders: A critical review

The female reproductive years are characterized by fluctuations in ovarian hormones across the menstrual cycle, which have the potential to modulate neurophysiological and behavioral dynamics. Menstrually-related mood disorders (MRMDs) comprise cognitive-affective or somatic symptoms that are thought to be triggered by the rapid fluctuations in ovarian hormones in the luteal phase of the menstrual cycle. MRMDs include premenstrual syndrome (PMS), premenstrual dysphoric disorder (PMDD), and premenstrual exacerbation (PME) of other psychiatric disorders. Electroencephalography (EEG) non-invasively records in vivo synchronous activity from populations of neurons with high temporal resolution. The present overview sought to systematically review the current state of task-related and resting-state EEG investigations on MRMDs. Preliminary evidence indicates lower alpha asymmetry at rest being associated with MRMDs, while one study points to the effect being luteal-phase specific. Moreover, higher luteal spontaneous frontal brain activity (slow/fast wave ratio as measured by the delta/beta power ratio) has been observed in persons with MRMDs, while sleep architecture results point to potential circadian rhythm disturbances. In this review, we discuss the quality of study designs as well as future perspectives and challenges of supplementing the diagnostic and scientific toolbox for MRMDs with EEG.

Neural Correlates of Positive Outcome Expectancy for Aggression: Evidence from Voxel-Based Morphometry and Resting-State Functional Connectivity Analysis

Positive outcome expectancy is a crucial cognitive factor influencing aggression, yet its neural basis remains unclear. Therefore, the present study combined voxel-based morphometry (VBM) with a resting-state functional connectivity (RSFC) analysis to investigate the brain correlates of positive outcome expectancy in aggression in young people. In the VBM analysis, multiple linear regression was conducted to explore the relationship between individual differences in aggressive positive outcome expectancy and regional gray matter volume (GMV) among 325 undergraduate students. For the RSFC analysis, seed regions were selected based on the results of the VBM analysis. Subsequently, multiple linear regression was employed to examine whether a significant correlation existed between individual differences in aggressive positive outcome expectancy and the RSFC of seed regions with other brain regions in 304 undergraduate students. The findings indicated that aggressive positive outcome expectancy was positively correlated with GMV in the posterior cingulate cortex (PCC), right temporoparietal junction (TPJ), and medial prefrontal cortex (MPFC). Moreover, it was also positively associated with RSFC between the PCC and the left dorsolateral prefrontal cortex (DLPFC). The prediction analysis indicated robust relationships between aggressive positive outcome expectancy and the GMV in the PCC, right TPJ, as well as the RSFC between the PCC and the left DLPFC. Our research provides the initial evidence for the neural basis of positive outcome expectancy in aggression, suggesting the potential role of the PCC as a hub in its neural network.

Effect of transcranial photobiomodulation on electrophysiological activity of brain in healthy individuals: A scoping review

BACKGROUND OBJECTIVE

Transcranial photobiomodulation (tPBM) is a safe and non-invasive treatment that has recently emerged as an effective technique to apply near-infrared or red light to activate neural tissues. The objective is to review the literature on the effect of tPBM on electrophysiological activity in healthy individuals.

METHODS

Literature was searched through PubMed, Scopus, Web of Science, Cumulated Index to Nursing and Allied Health Literature (CINAHL), Embase, and Ovid for transcranial photobiomodulation therapy in healthy individuals age group 18-80 years of either gender having electroencephalography as an outcome. Critical appraisal of included Randomized Controlled Trials and non-randomized experimental studies was done using Joanna Briggs Institute (JBI) critical appraisal tool.

RESULTS

A database search yielded a total of 4156 results. After eliminating 2626 duplicates, 1530 records were left. 32 articles were considered for full-text screening after 1498 records were excluded through title and abstract screening. 10 articles were included in this review. tPBM has been found to increase the higher electrophysiological oscillations and there is inconclusive evidence targeting the lower oscillatory electrophysiological frequencies.

CONCLUSION

Transcranial photobiomodulation can have promising effects on the electrophysiological activity of the brain in healthy individuals.

Individual differences in the effects of salience and reward on impulse control and action selection

Impulse control and adequate decision making are vital functions when it comes to detection and adherence to personal goals and societal rules. In the current study we tested the hypothesis that increasing the salience of environmental cues would be most effective in improving impulse control, as assessed by a stop-signal task, in subjects with low environmental susceptibility as indexed by low pre-stimulus EEG alpha power. In addition, we anticipated that an external-reward manipulation improves performance during a Go/No go task, especially in individuals with low task-induced motivation as indexed by low theta/beta power ratios. High salience of stop signals enhanced stopping performance but there was no difference in responsivity to the salience manipulation between participants with high and low EEG alpha power. Individuals with low theta/beta power ratios responded more accurately when rewards were involved. Together these results suggest that increasing the salience of external cues may help impulse control in general, whereas the effectiveness of external-reward manipulations is higher in individuals with low task-induced motivation.

No evidence from a negative mood induction fMRI task for frontal functional asymmetry as a suitable neurofeedback target

Frontal functional asymmetry (FA) has been proposed as a potential target for neurofeedback (NFB) training for mental disorders but most FA NFB studies used electroencephalography while the investigations of FA NFB in functional magnetic resonance imaging (fMRI) are rather limited. In this study, we aimed at identifying functional asymmetry effects in fMRI and exploring its potential as a target for fMRI NFB studies by re-analyzing an existing data set containing a resting state measurement and a sad mood induction task of n = 30 participants with remitted major depressive disorder and n = 30 matched healthy controls. We applied low-frequency fluctuations (ALFF), fractional ALFF, and regional homogeneity and estimated functional asymmetry in both a voxel-wise and regional manner. We assessed functional asymmetry during rest and negative mood induction as well as functional asymmetry changes between the phases, and associated the induced mood change with the change in functional asymmetry. Analyses were conducted within as well as between groups. Despite extensive analyses, we identified only very limited effects. While some tests showed nominal significance, our results did not contain any clear identifiable patterns of effects that would be expected if a true underlying effect would be present. In conclusion, we do not find evidence for FA effects related to negative mood in fMRI, which questions the usefulness of FA measures for real-time fMRI neurofeedback as a treatment approach for affective disorders.

Can we manipulate brain connectivity? A systematic review of cortico-cortical paired associative stimulation effects

OBJECTIVE

Cortico-cortical paired associative stimulation (ccPAS) is a form of dual-site transcranial magnetic stimulation (TMS) entailing a series of single-TMS pulses paired at specific interstimulus intervals (ISI) delivered to distant cortical areas. The goal of this article is to systematically review its efficacy in inducing plasticity in humans focusing on stimulation parameters and hypotheses of underlying neurophysiology.

METHODS

A systematic review of the literature from 2009-2023 was undertaken to identify all articles utilizing ccPAS to study brain plasticity and connectivity. Six electronic databases were searched and included.

RESULTS

32 studies were identified. The studies targeted connections within the same hemisphere or between hemispheres. 28 ccPAS studies were in healthy participants, 1 study in schizophrenia, and 1 in Alzheimer's disease (AD) patients. 2 additional studies used cortico-cortical repetitive paired associative stimulation (cc-rPAS) in generalized anxiety disorder (GAD) patients. Outcome measures include electromyography (EMG), behavioral measures, electroencephalography (EEG), and functional magnetic resonance imaging (fMRI). ccPAS seems to be able to modulate brain connectivity depending on the ISI.

CONCLUSIONS

ccPAS can be used to modulate corticospinal excitability, brain activity, and behavior. Although the stimulation parameters used across studies reviewed in this paper are varied, ccPAS is a promising approach for basic research and potential clinical applications.

SIGNIFICANCE

Recent advances in neuroscience have caused a shift of interest from the study of single areas to a more complex approach focusing on networks of areas that orchestrate brain activity. Consequently, the TMS community is also witnessing a change, with a growing interest in targeting multiple brain areas rather than a single locus, as evidenced by an increasing number of papers using ccPAS. In light of this new enthusiasm for brain connectivity, this review summarizes existing literature and stimulation parameters that have proven effective in changing electrophysiological, behavioral, or neuroimaging-derived measures.

Frontal Alpha Asymmetry in Posttraumatic Stress Disorder: Group Differences Among Individuals With and Without PTSD During an Inhibitory Control Task

The current study examined frontal alpha asymmetry (FAA) as a marker of approach- and avoidance-related prefrontal activity in participants with and without trauma exposure and posttraumatic stress disorder (PTSD). We investigated FAA in an inhibitory control paradigm (threatening vs nonthreatening cues) under 2 levels of cognitive demand (baseline: images constant within a block of trials; vs filtering: images varied randomly within a block) in 3 groups of participants: individuals with PTSD (n = 16), exposed to trauma but without PTSD (n = 14), and a control group without PTSD or trauma exposure (n = 15). Under low demand (baseline), both PTSD and trauma-exposed participants exhibited significantly greater relative left than right frontal brain activity (approach) to threatening than to nonthreatening images. Under high demand (filtering), no FAA differences were found between threatening and nonthreatening images, but PTSD participants revealed more relative left than right FAA, whereas trauma-exposed participants showed reduced left relative right FAA. In all conditions, healthy controls exhibited reduced left relative to right FAA and no differences between threatening and nonthreatening images. Study findings suggest dysfunctional prefrontal mechanisms of emotion regulation in PTSD, but adaptive prefrontal regulation in trauma-exposed individuals without PTSD.

What a difference timing makes: Cortisol effects on neural underpinnings of emotion regulation

The ability of emotion regulation under stress is of crucial importance to psychosocial health. Yet, the dynamic function of stress hormones for the cognitive control of emotions over time via non-genomic and genomic cortisol effects remains to be elucidated. In this randomized, double-blind, placebo-controlled neuroimaging experiment, 105 participants (54 men, 51 women) received 20 mg hydrocortisone (cortisol) or a placebo either 30min (rapid, non-genomic cortisol effects) or 90min (slow, genomic cortisol effects) prior to a cognitive reappraisal task including different regulatory goals (i.e., downregulate vs. upregulate negative emotions). On the behavioral level, cortisol rapidly reduced and slowly enhanced emotional responsivity to negative pictures. However, only slow cortisol effects improved downregulation of negative emotions. On the neural level, cortisol rapidly enhanced, but slowly reduced amygdala and dorsolateral prefrontal activation as well as functional connectivity between both structures in the down- minus upregulate contrast. This interaction speaks for an effortful but ineffective regulation of negative emotions during rapid cortisol effects and improved emotion regulation capacities during slow cortisol effects. Taken together, these results indicate a functional shift of cortisol effects on emotion regulation processes over time which may foster successful adaptation to and recovery from stressful life events.

Cerebellar Grey Matter Volumes in Reactive Aggression and Impulsivity in Healthy Volunteers

Several lines of evidence point towards the involvement of the cerebellum in reactive aggression. In addition to the posterior cerebellar hemisphere, the vermis has been suggested to play a prominent role in impulse regulation. In the present study, we set out to further examine the relationships between cerebellar grey matter volumes, aggression, and impulsivity in 201 healthy volunteers. 3 T structural magnetic resonance imaging scans were acquired to investigate grey matter volumes of the cerebellar vermis and the anterior and posterior lobules. Aggression was assessed with the Buss-Perry Aggression Questionnaire and impulsivity was measured with the Barratt Impulsiveness Scale-11. Results showed that impulsivity was positively associated with grey matter volumes of the cerebellar vermis and inversely correlated with grey matter volumes of the right posterior lobule. In addition, smaller volumes of the right posterior lobules were associated with higher physical aggression. Exploratory analyses indicated that for the right hemisphere, this association was driven by grey matter volumes of lobules VIIb and VIIIa. Our findings provide correlational evidence in healthy volunteers for the involvement of the cerebellar vermis and posterior lobules in a cortico-limbic-cerebellar circuit of aggression.

The Impacts of Anxiety and Motivation on Spatial Performance: Implications for Gender Differences in Mental Rotation and Navigation

Despite extensive research on gender differences in spatial cognition, the potential roles of affective and situational factors in accounting for these differences remain relatively understudied. Here, we discuss the impacts of spatial anxiety and motivation in mental rotation and navigation tasks, particularly their roles in explaining the gender performance gaps. We highlight the distinction between approach and avoidance motivation, as well as interactions between anxiety and motivation. Attention, working memory, and response strategy are discussed as mechanisms by which anxiety and motivation may affect performance on spatial tasks. Implications for a broader approach that also considers other psychological variables, such as confidence, are discussed.

Probing fMRI brain connectivity and activity changes during emotion regulation by EEG neurofeedback

Despite the existence of several emotion regulation studies using neurofeedback, interactions among a small number of regions were evaluated, and therefore, further investigation is needed to understand the interactions of the brain regions involved in emotion regulation. We implemented electroencephalography (EEG) neurofeedback with simultaneous functional magnetic resonance imaging (fMRI) using a modified happiness-inducing task through autobiographical memories to upregulate positive emotion. Then, an explorative analysis of whole brain regions was done to understand the effect of neurofeedback on brain activity and the interaction of whole brain regions involved in emotion regulation. The participants in the control and experimental groups were asked to do emotion regulation while viewing positive images of autobiographical memories and getting sham or real (based on alpha asymmetry) EEG neurofeedback, respectively. The proposed multimodal approach quantified the effects of EEG neurofeedback in changing EEG alpha power, fMRI blood oxygenation level-dependent (BOLD) activity of prefrontal, occipital, parietal, and limbic regions (up to 1.9% increase), and functional connectivity in/between prefrontal, parietal, limbic system, and insula in the experimental group. New connectivity links were identified by comparing the brain functional connectivity between experimental conditions (Upregulation and View blocks) and also by comparing the brain connectivity of the experimental and control groups. Psychometric assessments confirmed significant changes in positive and negative mood states in the experimental group by neurofeedback. Based on the exploratory analysis of activity and connectivity among all brain regions involved in emotion regions, we found significant BOLD and functional connectivity increases due to EEG neurofeedback in the experimental group, but no learning effect was observed in the control group. The results reveal several new connections among brain regions as a result of EEG neurofeedback which can be justified according to emotion regulation models and the role of those regions in emotion regulation and recalling positive autobiographical memories.

Scarcity Enhances Outcome Evaluation in the Present: Electroencephalography Evidence

Scarcity goods have generally been perceived as high in value in real-world and empirical studies. However, few studies have investigated this value over time, such as performance in intertemporal decision making. This study’s chief objective was to determine how scarcity evaluation changes temporally. We used the electroencephalogram technique and an outcome evaluation task with the valuation of scarcity and ordinary rewards delivered at different times to explore the effect of scarcity on delay discounting. The feedback-related negativity (FRN) results show that ordinary goods were associated with a more negative amplitude than scarcity goods, and that rewards delivered in the future evoked more negative deflection compared to those delivered immediately. The prominent FRN effect was derived mainly from ordinary trials rather than scarcity trials in the immediate condition and in the future rather than only in the immediate condition. The Frontal Asymmetry Index (FAI) results show that the scarcity condition was associated with greater relative left frontal cortical activity than the ordinary condition when delivered immediately. The frontal asymmetry indicated greater approach motivation. Our electrophysiology data indicate that scarcity goods have a perceived high value, particularly when delivered immediately.

The effects of prefrontal vs. parietal cortex transcranial direct current stimulation on craving, inhibition, and measures of self-esteem

While prefrontal cortex dysfunction has been implicated in high food cravings, other cortical regions, like the parietal cortex, are potentially also involved in regulating craving. This study explored the effects of stimulating the inferior parietal lobule (IPL) and dorsolateral prefrontal cortex (DLPFC) on food craving state and trait. Transcranial direct current stimulation (tDCS) was administered at 1.5 mA for 5 consecutive days. Participants received 20 min of IPL, DLPFC, or sham stimulation (SHAM) each day which consisted of two rounds of 10-min stimulation, divided by a 10-min mindfulness task break. In addition, we studied inhibition and subjective psychological aspects like body image and self-esteem state and trait. To decompose immediate and cumulative effects, we measured the following on days 1 and 5: inhibition through the Go/No-go task; and food craving, self-esteem, and body appreciation through a battery of questionnaires. We found that false alarm errors decreased in the participants receiving active stimulation in the DLPFC (DLPFC-group). In contrast, false alarm errors increased in participants receiving active stimulation in the IPL (IPL-group). At the same time, no change was found in the participants receiving SHAM (SHAM-group). There was a trending reduction in craving trait in all groups. Momentary craving was decreased in the DLPFC-group and increased in IPL-group, yet a statistical difference was not reached. According to time and baseline, self-esteem and body perception improved in the IPL-group. Furthermore, self-esteem trait significantly improved over time in the DLPFC-group and IPL-group. These preliminary results indicate that tDCS modulates inhibition in frontoparietal areas with opposite effects, enhancing it in DLPFC and impairing it in IPL. Moreover, craving is moderately linked to inhibition, self-esteem, and body appreciation which seem not to be affected by neuromodulation but may rely instead on broader regions as more complex constructs. Finally, the fractionated protocol can effectively influence inhibition with milder effects on other constructs.

Neuroanatomical correlates of social approach in Williams Syndrome and down syndrome

Individuals with Williams Syndrome (WS) or Downs Syndrome (DS) are often described as hypersociable, friendly and overly trusting of others. This hypersociability is a major concern for parents/caregivers due to the associated increased risk of exploitation and victimisation. Two brain regions - the amygdala and the orbitofrontal cortex (OFC) - have been implicated in driving this hypersociability in WS, and in the general population and have associations with emotional evaluation, threat detection and social motivation. However, there has been little neuroimaging research on this topic, especially in DS, to date. The aim of the present study was to investigate the potential neuroanatomical and neuropsychological correlates of hypersociability in WS and DS. Twelve individuals with WS (M = 22 years of age) and eleven individuals with DS (M = 26 years of age) completed a neuropsychological battery of executive functioning and social measures, including informant ratings on an ecologically measure of social approach. Clinical groups and twelve typically developing controls (M = 23 years) underwent a magnetic resonance imaging scan to investigate volumetric differences in the OFC and the amygdala. As expected, WS individuals displayed the highest overall social approach, especially in relation to need to approach strangers and drive to interact with strangers, as well as inappropriate/overfriendly behaviours. Both groups rated similarly in terms of social trust and unconditional positive regard. Emotion recognition abilities were similar across groups, with the DS group displaying some difficulties with negative emotions (especially anger). Inhibition and flexibility were similarly impaired across WS and DS. Compared to neurotypical controls, the DS group showed increased amygdala volumes bilaterally, while the WS group showed an enlarged right medial OFC. Approach ratings were significantly correlated with left amygdala and medial and left lateral OFC volumes in WS, and with these same regions bilaterally in DS. Results provide potential biological explanations for the hypersociability seen in WS and DS. Future research should focus on other potential neural correlates, as well as potential genetic and hormonal contributions to approach.

Dynamic functional connectivity estimation for neurofeedback emotion regulation paradigm with simultaneous EEG-fMRI analysis

Joint Analysis of EEG and fMRI datasets can bring new insight into brain mechanisms. In this paper, we employed the recently introduced Correlated Coupled Tensor Matrix Factorization (CCMTF) method for analysis of the emotion regulation paradigm based on EEG frontal asymmetry neurofeedback in the alpha frequency band with simultaneous fMRI. CCMTF method assumes that the co-variations of the common dimension (temporal dimension) between EEG and fMRI are correlated and not necessarily identical. The results of the CCMTF method suggested that EEG and fMRI had similar covariations during the transition of brain activities from resting states to task (view and upregulation) states and these covariations followed an increasing trend. The fMRI shared spatial component showed activations in the limbic system, DLPFC, OFC, and VLPC regions, which were consistent with the previous studies and were linked to EEG frequency patterns in the range of 1-15 Hz with a correlation value close to 0.75. The estimated regions from the CCMTF method were then used as the candidate nodes for dynamic functional connectivity (dFC) analysis, in which the changes in connectivity from view to upregulation states were examined. The results of the dFC analysis were compared with a Normalized Mutual information (NMI) based approach in two different frequency ranges (1-15 and 15-40 Hz) as the NMI method was applied to the vectors of dFC nodes of EEG and fMRI data. The results of the two methods illustrated that the relation between EEG and fMRI datasets was mostly in the frequency range of 1-15 Hz. These relations were both in the brain activations and the dFCs between the two modalities. This paper suggests that the CCMTF method is a capable approach for extracting the shared information between EEG and fMRI data and can reveal new information about brain functions and their connectivity without solving the EEG inverse problem or analyzing different frequency bands.

Frontal Alpha Asymmetry in Children with Trauma Exposure

The purpose of the current study was to investigate differences in frontal alpha asymmetry (FAA) between children (5-17 years) with or without histories of trauma exposure. EEG data were obtained from 165 children who participated in the Healthy Brain Network Initiative during rest with eyes open and closed. FAA during resting-state electroencephalography was significantly more negative in the trauma-exposed group, suggesting greater left lateralized FAA and avoidance-oriented motivation. Moreover, alpha suppression (difference in alpha amplitude between eyes open and eyes closed conditions) was marginally greater in the trauma-exposed group. The results suggest that early exposure to trauma may be associated with trait-level avoidance of environmental stimuli, which ultimately may be predictive of psychopathology, including posttraumatic stress disorder (PTSD). Study findings thus provide preliminary evidence of brain-based mechanisms that may confer risk for PTSD in the wake of early trauma exposure.

Frontal alpha asymmetry interaction with an experimental story EEG brain-computer interface

Although interest in brain-computer interfaces (BCIs) from researchers and consumers continues to increase, many BCIs lack the complexity and imaginative properties thought to guide users toward successful brain activity modulation. We investigate the possibility of using a complex BCI by developing an experimental story environment with which users interact through cognitive thought strategies. In our system, the user's frontal alpha asymmetry (FAA) measured with electroencephalography (EEG) is linearly mapped to the color saturation of the main character in the story. We implemented a user-friendly experimental design using a comfortable EEG device and short neurofeedback (NF) training protocol. In our system, seven out of 19 participants successfully increased FAA during the course of the study, for a total of ten successful blocks out of 152. We detail our results concerning left and right prefrontal cortical activity contributions to FAA in both successful and unsuccessful story blocks. Additionally, we examine inter-subject correlations of EEG data, and self-reported questionnaire data to understand the user experience of BCI interaction. Results suggest the potential of imaginative story BCI environments for engaging users and allowing for FAA modulation. Our data suggests new research directions for BCIs investigating emotion and motivation through FAA.

Evidence for lateralized functional connectivity patterns at rest related to the tendency of externalizing or internalizing anger

Previous electroencephalographic and brain stimulation studies have shown that anger responses may be differently lateralized in the prefrontal cortex, with outward-oriented responses (externalized anger) linked to left prefrontal activity, and inward-oriented responses (internalized anger) linked to right prefrontal activity. However, the specific neural structures involved in this asymmetry, and how they interact to produce individual differences, remain unexplored. Furthermore, it is unclear whether such asymmetry may be explained by general behavioral tendencies, known as Behavioral Activation and Behavioral Inhibition Systems (BIS/BAS). Therefore, we analyzed the tendency of externalizing and internalizing anger, respectively measured by the Anger-Out and Anger-In subscales of the State-Trait Anger Expression Inventory, with the patterns of functional connectivity at rest of 71 participants. A left, prefrontal, resting-state, functional connectivity pattern was found for externalizing anger (Anger-Out), including the left inferior frontal gyrus and the left frontal eye fields. By contrast, a right, prefrontal, resting-state, functional connectivity pattern was found for internalizing anger (Anger-In), including the rostral and lateral prefrontal cortex, the orbitofrontal cortex, the frontal pole, the superior, middle and inferior frontal gyri, and the anterior cingulate. Notably, these patterns were not associated with the BIS/BAS scores. In this study, for the first time, we provide evidence using fMRI functional connectivity for two specific lateralized circuits contributing to individual differences in externalizing and internalizing anger. These results confirm and extend the asymmetry hypothesis for anger and have notable implications in the treatment of anger-related problems.

The neurophysiology of the intervention strategies of Awareness Training Program on emotion regulation

Emotion regulation is essential for healthy living. Previous studies have found that mental training such as compassion meditation could help with emotion regulation. However, the underlying neural mechanism and possible intervention strategies of group-based Mahayana Buddhist intervention involved in emotion regulation are still unclear. This event-related potential (ERP) study investigated how compassion and wisdom meditations, two key components of the Awareness Training Program (ATP), may regulate emotion during different mental processing stages, namely attention deployment, cognitive change, and response modification. Eighty-five middle-aged working adults with moderate stress were voluntarily recruited for this study, using a 128-channel electroencephalogram system. After 7 weeks of training, participants (ATP attendance, n = 42; waitlist control, n = 43) were instructed to view negative pictures while practicing compassion or wisdom meditation, with corresponding priming words. Another normal priming condition and a neutral picture condition were set as control conditions. ERP results in the ATP group showed that negative pictures induced greater prefrontal activity (N400 component) in both compassion and wisdom meditation conditions compared with the normal condition, while the control group showed little difference between the conditions. Significantly higher heart rate variability was found in the compassion but not wisdom meditation when compared with the neutral priming condition. Correspondent changes in behavioural data were also found. Converging evidence showed that compassion meditation training could modulate negative emotion processing in stages of attention deployment, cognitive change, and behavioural responses. The prefrontal lobe could play an important role in the process of emotion regulation by compassion meditation, possibly due to the emphasis of the ATP on contemplative practices.

Frontal Alpha Asymmetry in Response to Stressor Moderates the Relation Between Parenting Hassles and Child Externalizing Problems

Inequitable urban environments are associated with toxic stress and altered neural social stress processing that threatens the development of self-regulation. Some children in these environments struggle with early onset externalizing problems that are associated with a variety of negative long-term outcomes. While previous research has linked parenting daily hassles to child externalizing problems, the role of frontal alpha asymmetry (FAA) as a potential modifier of this relationship has scarcely been explored. The present study examined mother-child dyads, most of whom were living in low socioeconomic status households in an urban environment and self-identified as members of racial minority groups. Analyses focused on frustration task electroencephalography (EEG) data from 67 children (mean age = 59.0 months, SD = 2.6). Mothers reported the frequency of their daily parenting hassles and their child's externalizing problems. Frustration task FAA moderated the relationship between parenting daily hassles and child externalizing problems, but resting FAA did not. More specifically, children with left frontal asymmetry had more externalizing problems as their mothers perceived more hassles in their parenting role, but parenting hassles and externalizing problems were not associated among children with right frontal asymmetry. These findings lend support to the motivational direction hypothesis and capability model of FAA. More generally, this study reveals how individual differences in lateralization of cortical activity in response to a stressor may confer differential susceptibility to child behavioral problems with approach motivation (i.e., left frontal asymmetry) predicting externalizing problems under conditions of parental stress.

The neural bases of expressive suppression: A systematic review of functional neuroimaging studies

Expressive suppression refers to the inhibition of emotion-expressive behavior (e.g., facial expressions of emotion). Although it is a commonly used emotion regulation strategy with well-documented consequences for well-being, little is known about its underlying mechanisms. In this systematic review, we for the first time synthesize functional neuroimaging studies on the neural bases of expressive suppression in non-clinical populations. The 12 studies included in this review contrasted the use of expressive suppression to simply watching emotional stimuli. Results showed that expressive suppression consistently increased activation of frontoparietal regions, especially the dorsolateral and ventrolateral prefrontal cortices and inferior parietal cortex, but decreased activation in temporo-occipital areas. Results regarding the involvement of the insula and amygdala were inconsistent with studies showing increased, decreased, or no changes in activation. These mixed findings underscore the importance of distinguishing expressive suppression from other forms of suppression and highlight the need to pay more attention to experimental design and neuroimaging data analysis procedures. We discuss these conceptual and methodological issues and provide suggestions for future research.

Effect of Indoor Forest Bathing on Reducing Feelings of Fatigue Using Cerebral Activity as an Indicator

We created an indoor forest bathing environment in a sunlight-type environmentally controlled chamber and both physiological and psychological measurements were conducted for the evaluation of mental fatigue reduction. At first, a working memory load experiment was performed among 10 participants in a space without plants to identify an indicator correlating with feelings of fatigue, using the cerebral activity of the prefrontal cortex. Then, the indicator was used to evaluate whether a 20-min exposure to an indoor forest bathing environment reduced the level of the feeling of fatigue. The working memory load experiment demonstrated that, when mental fatigue increased, the amount of oxygenated hemoglobin (oxy-Hb) in the right prefrontal cortex and the right-left difference in oxy-Hb (ΔRL oxy-Hb) in the prefrontal cortex increased. These were proposed as indicators of mental fatigue. In the indoor forest bathing experiment, staying in an indoor green space showed that the subjective values of feeling of fatigue decreased and ΔRL oxy-Hb decreased. Since these results demonstrated an opposite effect to the increase in ΔRL oxy-Hb related to the feeling of fatigue, it was inferred that the decrease in ΔRL oxy-Hb reflected the fatigue reduction in the indoor forest bathing environment.

Electrophysiological Correlates of Romantic Love: A Review of EEG and ERP Studies with Beloved-Related Stimuli

Science is starting to unravel the neural basis of romantic love. The goal of this literature review was to identify and interpret the electrophysiological correlates of romantic love. Electroencephalography (EEG) and event-related potential (ERP) studies with a design that elicits romantic love feelings were included. The methods of previous EEG studies are too heterogeneous to draw conclusions. Multiple ERP studies, however, have shown that beloved stimuli elicit an enhanced late positive potential (LPP/P3/P300), which is not due to familiarity, positive valence, or objective beauty. This effect occurs in Western and Eastern cultures and for pictorial and verbal information, and results from bottom-up rather than top-down factors. Studies have also shown that beloved stimuli elicit an early posterior negativity (EPN), which also does not seem to be due to familiarity or positive valence. Data on earlier ERP components (P1, N1, P2, N170/VPP, N2) is scarce and mixed. Of course, the enhanced LPP and EPN are not specific to romantic love. Instead, they suggest that the beloved captures early attention, within 200–300 ms after stimulus onset that is relatively resource-independent, and subsequently receives sustained motivated attention. Future research would benefit from employing cognitive tasks and testing participants who are in love regardless of relationship status.

Frontal Asymmetry as a Neural Correlate of Motivational Conflict

Motivational systems of approach, avoidance, and inhibition are fundamental to human behavior. While past research has linked approach motivation with greater relative left frontal asymmetry, many attempts to link avoidance motivation with greater relative right frontal asymmetry have been mixed. These mixed effects could be due to coactivation of the avoidance and behavioral inhibition system (BIS). Much recent evidence indicates that the behavioral inhibition system may be associated with greater relative right frontal activation. The current review examines evidence linking traits associated with the behavioral inhibition system with resting right frontal asymmetry. Other research links individual differences associated with the behavioral inhibition system with state changes in relative right frontal asymmetry. Moreover, activation of the behavioral inhibition system, but not activation of withdrawal motivation, increases greater relative right frontal asymmetry. Together, this work highlights the role of relative frontal asymmetry as a neural correlate in motivational conflict and helps to disentangle behavioral inhibition from avoidance motivation.

Gamma Oscillations in the Temporal Pole Reflect the Contribution of Approach and Avoidance Motivational Systems to the Processing of Fear and Anger Words

Prior reports suggest that affective effects in visual word processing cannot be fully explained by a dimensional perspective of emotions based on valence and arousal. In the current study, we focused on the contribution of approach and avoidance motivational systems that are related to different action components to the processing of emotional words. To this aim, we compared frontal alpha asymmetries and brain oscillations elicited by anger words associated with approach (fighting) motivational tendencies, and fear words that may trigger either avoidance (escaping), approach (fighting) or no (freezing) action tendencies. The participants’ task was to make decisions about approaching or distancing from the concepts represented by words. The results of cluster-based and beamforming analyses revealed increased gamma power band synchronization for fear words relative to anger words between 725 and 750 ms, with an estimated neural origin in the temporal pole. These findings were interpreted to reflect a conflict between different action tendencies underlying the representation of fear words in semantic and emotional memories, when trying to achieve task requirements. These results are in line with the predictions made by the fear-hinders-action hypothesis. Additionally, current data highlights the contribution of motivational features to the representation and processing of emotional words.

Predictions of tDCS treatment response in PTSD patients using EEG based classification

Transcranial direct current stimulation (tDCS) is an emerging therapeutic tool for treating posttraumatic stress disorder (PTSD). Prior studies have shown that tDCS responses are highly individualized, thus necessitating the individualized optimization of treatment configurations. To date, an effective tool for predicting tDCS treatment outcomes in patients with PTSD has not yet been proposed. Therefore, we aimed to build and validate a tool for predicting tDCS treatment outcomes in patients with PTSD. Forty-eight patients with PTSD received 20 min of 2 mA tDCS stimulation in position of the anode over the F3 and cathode over the F4 region. Non-responders were defined as those with less than 50% improvement after reviewing clinical symptoms based on the Clinician-Administered DSM-5 PTSD Scale (before and after stimulation). Resting-state electroencephalograms were recorded for 3 min before and after stimulation. We extracted power spectral densities (PSDs) for five frequency bands. A support vector machine (SVM) model was used to predict responders and non-responders using PSDs obtained before stimulation. We investigated statistical differences in PSDs before and after stimulation and found statistically significant differences in the F8 channel in the theta band (p = 0.01). The SVM model had an area under the ROC curve (AUC) of 0.93 for predicting responders and non-responders using PSDs. To our knowledge, this study provides the first empirical evidence that PSDs can be useful biomarkers for predicting the tDCS treatment response, and that a machine learning model can provide robust prediction performance. Machine learning models based on PSDs can be useful for informing treatment decisions in tDCS treatment for patients with PTSD.

The Role of the Dorsal-Lateral Prefrontal Cortex in Reward Sensitivity During Approach-Avoidance Conflict

Approach-Avoidance conflict (AAC) arises from decisions with embedded positive and negative outcomes, such that approaching leads to reward and punishment and avoiding to neither. Despite its importance, the field lacks a mechanistic understanding of which regions are driving avoidance behavior during conflict. In the current task, we utilized transcranial magnetic stimulation (TMS) and drift-diffusion modeling to investigate the role of one of the most prominent regions relevant to AAC-the dorsolateral prefrontal cortex (dlPFC). The first experiment uses in-task disruption to examine the right dlPFC's (r-dlPFC) causal role in avoidance behavior. The second uses single TMS pulses to probe the excitability of the r-dlPFC, and downstream cortical activations, during avoidance behavior. Disrupting r-dlPFC during conflict decision-making reduced reward sensitivity. Further, r-dlPFC was engaged with a network of regions within the lateral and medial prefrontal, cingulate, and temporal cortices that associate with behavior during conflict. Together, these studies use TMS to demonstrate a role for the dlPFC in reward sensitivity during conflict and elucidate the r-dlPFC's network of cortical regions associated with avoidance behavior. By identifying r-dlPFC's mechanistic role in AAC behavior, contextualized within its conflict-specific downstream neural connectivity, we advance dlPFC as a potential neural target for psychiatric therapeutics.

High-Definition Transcranial Direct Current Stimulation Over the Right Lateral Prefrontal Cortex Increases Maximization Tendencies

People seek the best in every aspect of life. However, little is known about the neurobiological mechanisms supporting this process of maximization. In this study, maximization tendencies were increased by using high-definition transcranial direct current stimulation (HD-tDCS) over the right dorsolateral prefrontal cortex (DLPFC). Participants (n = 64) received 2 mA anodal 4 × 1 HD-tDCS or sham stimulation over the right DLPFC in two sessions and subsequently completed an N-back working memory task and a maximization scale (MS). We observed that maximization tendency scores increased during anodal stimulation. Furthermore, the results indicate that this increase in maximization tendency was driven by motivational changes. On the MS, alternative search subscale scores were significantly increased, demonstrating an increase in motivation to evaluate more alternatives; however, the results did not indicate that the increase in maximization tendencies was due to working memory improvement. These results demonstrated that maximization tendencies can be strengthened through noninvasive interventions and that the right DLPFC has a causal relationship with maximization tendencies.

Motivation-Achievement Cycles in Learning: a Literature Review and Research Agenda

The question of how learners’ motivation influences their academic achievement and vice versa has been the subject of intensive research due to its theoretical relevance and important implications for the field of education. Here, we present our understanding of how influential theories of academic motivation have conceptualized reciprocal interactions between motivation and achievement and the kinds of evidence that support this reciprocity. While the reciprocal nature of the relationship between motivation and academic achievement has been established in the literature, further insights into several features of this relationship are still lacking. We therefore present a research agenda where we identify theoretical and methodological challenges that could inspire further understanding of the reciprocal relationship between motivation and achievement as well as inform future interventions. Specifically, the research agenda includes the recommendation that future research considers (1) multiple motivation constructs, (2) behavioral mediators, (3) a network approach, (4) alignment of intervals of measurement and the short vs. long time scales of motivation constructs, (5) designs that meet the criteria for making causal, reciprocal inferences, (6) appropriate statistical models, (7) alternatives to self-reports, (8) different ways of measuring achievement, and (9) generalizability of the reciprocal relations to various developmental, ethnic, and sociocultural groups.

Modulating Frontal Networks' Timing-Dependent-Like Plasticity With Paired Associative Stimulation Protocols: Recent Advances and Future Perspectives

Starting from the early 2000s, paired associative stimulation (PAS) protocols have been used in humans to study brain connectivity in motor and sensory networks by exploiting the intrinsic properties of timing-dependent cortical plasticity. In the last 10 years, PAS have also been developed to investigate the plastic properties of complex cerebral systems, such as the frontal ones, with promising results. In the present work, we review the most recent advances of this technique, focusing on protocols targeting frontal cortices to investigate connectivity and its plastic properties, subtending high-order cognitive functions like memory, decision-making, attentional, or emotional processing. Overall, current evidence reveals that PAS can be effectively used to assess, enhance or depress physiological connectivity within frontal networks in a timing-dependent way, in turn modulating cognitive processing in healthy and pathological conditions.

Individual differences in motivation and impulsivity link resting frontal alpha asymmetry and motor beta activation

Previous research has linked neural correlates with motivational traits and measures of impulsivity. However, few previous studies have investigated whether individual differences in motivation and impulsivity moderate the relationship between these disparate neural activity patterns. In a sample of 118 young adults, we used Electroencephalography (EEG) to examine whether behavioral activation and inhibition systems (BIS/BAS) and impulsivity facets (negative urgency, lack of perseverance), moderate the relationship between beta power and resting frontal alpha asymmetry. Regression analyses revealed a novel relationship between lesser beta power and greater left frontal alpha asymmetry (LFA). Moderation analyses suggest this relationship may strengthen as BIS/BAS levels increase, and trait impulsivity levels decrease from the mean. These results are among the first revealing a relationship between two widely investigated neural activity patterns of motivation and provide some indication individual differences moderate this relationship. The limitations of these findings and need for future research are discussed.