Out of control: evidence for anterior insula involvement in motor impulsivity and reactive aggression

Effects of chronic stress on cognitive function - From neurobiology to intervention

Exposure to chronic stress contributes considerably to the development of cognitive impairments in psychiatric disorders such as depression, generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD), post-traumatic stress disorder (PTSD), and addictive behavior. Unfortunately, unlike mood-related symptoms, cognitive impairments are not effectively treated by available therapies, a situation in part resulting from a still incomplete knowledge of the neurobiological substrates that underly cognitive domains and the difficulty in generating interventions that are both efficacious and safe. In this review, we will present an overview of the cognitive domains affected by stress with a specific focus on cognitive flexibility, behavioral inhibition, and working memory. We will then consider the effects of stress on neuronal correlates of cognitive function and the factors which may modulate the interaction of stress and cognition. Finally, we will discuss intervention strategies for treatment of stress-related disorders and gaps in knowledge with emerging new treatments under development. Understanding how cognitive impairment occurs during exposure to chronic stress is crucial to make progress towards the development of new and effective therapeutic approaches.

Motor impulsivity and spicy food craving: A mediation analysis of insula-based resting state functional connectivity

In China, the rate of spicy food consumption is rising, and chili pepper is among the most popular spicy foods consumed nationwide. However, little effort has been made to understand the mechanism behind spicy food craving. This exploratory study aimed to investigate differences in insula-based resting state functional connectivity (rsFC) between spicy food cravers and non-cravers, and the association between rsFC, impulsivity and spicy food craving. A group of extreme cravers (n = 49) and a group of age- and sex-matched non-cravers (n = 46) completed a resting-state fMRI scan, during which participants were instructed to keep their eyes closed, to not think of anything in particular, and to remain awake. Participants completed the Spicy Food Craving Questionnaire, Barratt Impulsiveness Scale, Sensation Seeking Scale and Positive and Negative Affect Schedule, and rated the frequency of spicy food intake. Results revealed increased insula-occipital lobe resting-state functional connectivity in individuals with spicy food cravings, and the positive correlations between insula-middle occipital gyrus rsFC, impulsivity and spicy food craving. Specifically, the insula-middle occipital gyrus rsFC strength mediated the relationship between the motor impulsivity and spicy food craving. It is hoped that our exploratory findings may shed new insights into the neural mechanisms of spicy food craving and motivate further exploration of spicy food craving in diverse contexts and cultures.

Resting-State Functional Connectivity Profile of Insular Subregions

The insula is often considered the fifth lobe of the brain and is increasingly recognized as one of the most connected regions in the brain, with widespread connections to cortical and subcortical structures. As a follow-up to our previous tractography work, we investigated the resting-state functional connectivity (rsFC) profiles of insular subregions and assessed their concordance with structural connectivity. We used the CONN toolbox to analyze the rsFC of the same 19 insular regions of interest (ROIs) we used in our prior tractography work and regrouped them into six subregions based on their connectivity pattern similarity. Our analysis of 50 healthy participants confirms the known broad connectivity of the insula and shows novel and specific whole-brain and intra-connectivity patterns of insular subregions. By examining such subregions, our findings provide a more detailed pattern of connectivity than prior studies that may prove useful for comparison between patients.

Trait Aggression is Reflected by a Lower Temporal Stability of EEG Resting Networks

Trait aggression can lead to catastrophic consequences for individuals and society. However, it remains unclear how aggressive people differ from others regarding basic, task-independent brain characteristics. We used EEG microstate analysis to investigate how the temporal organization of neural resting networks might help explain inter-individual differences in aggression. Microstates represent whole-brain networks, which are stable for short timeframes (40-120 ms) before quickly transitioning into other microstate types. Recent research demonstrates that the general temporal stability of microstates across types predicts higher levels of self-control and inhibitory control, and lower levels of risk-taking preferences. Given that these outcomes are inversely related to aggression, we investigated whether microstate stability at rest would predict lower levels of trait aggression. As males show higher levels of aggression than females, and males and females express aggression differently, we also tested for possible gender-differences. As hypothesized, people with higher levels of trait aggression showed lower microstate stability. This effect was moderated by gender, with men showing stronger associations compared to women. These findings support the notion that temporal dynamics of sub-second resting networks predict complex human traits. Furthermore, they provide initial indications of gender-differences in the functional significance of EEG microstates.

Neurofeedback and meditation technology in outpatient offender treatment: a feasibility and usability pilot study

Introduction

Although Cognitive Behavioral Therapy (CBT) is the most often used intervention in forensic treatment, its effectivity is not consistently supported. Interventions incorporating knowledge from neuroscience could provide for more successful intervention methods.

Methods

The current pilot study set out to assess the feasibility and usability of the study protocol of a 4-week neuromeditation training in adult forensic outpatients with impulse control problems. The neuromeditation training, which prompts awareness and control over brain states of restlessness with EEG neurofeedback, was offered in addition to treatment as usual (predominantly CBT).

Results

Eight patients completed the neuromeditation training under guidance of their therapists. Despite some emerging obstacles, overall, the training was rated sufficiently usable and feasible by patients and their therapists.

Discussion

The provided suggestions for improvement can be used to implement the intervention in treatment and set up future trials to study the effectiveness of neuromeditation in offender treatment.

Neural Correlates of Trait Impulsivity among Adult Healthy Individuals

Objective

: Impulsivity can be observed in individuals with or without mental illness. The discovery of neural correlates responsible for trait impulsivity can therefore help to understand the severity of psychiatric symptoms, personality characteristics and social adjustment. In this study, we aimed to identify the gray matter substrates of trait impulsivity in healthy individuals.

Methods

: Seventy-five healthy individuals were enrolled. At baseline, trait impulsivity was assessed using the Barratt Impulsiveness Scale (BIS) and all participants underwent T1-weighted magnetic resonance imaging scan. Beck Anxiety Inventory (BAI), World Health Organization Quality of Life (WHOQOL-BREF) and Connor-Davidson Resilience Scale (CD-RISC) were also assessed. Mean cortical thickness (CT) and the local gyrification index (LGI) were calculated to perform whole-brain vertex-wise correlation analysis, which were performed to investigate the relationship between BIS scores and CT or LGI in each brain region. We also revealed the relationship between brain regions and psychological measurements.

Results

: Total BIS scores were significantly and negatively correlated with mean CT values in the left lateral occipital cortex (OC) and LGIs in the inferior frontal gyrus (IFG). Correlation analyses revealed that the lateral OC's mean CT values were negatively correlated with BAI scores and positively correlated with WHOQOL-BREF scores, while LGI in the IFG was positively correlated with CD-RISC scores.

Conclusion

: Our study showed that trait impulsivity might be associated with the lateral OC and IFG in healthy individuals. Understanding the neural correlates of trait impulsivity could provide ways to expect high impulsivity, anxiety, and poor resilience in healthy adults.

The behavioral component of sexual inhibition and its relation with testosterone levels: An fMRI study in transgender and cisgender individuals

Many transgender individuals report having difficulties with initiating and seeking sexual contacts. Relatively to cisgender individuals, transgender individuals are more likely to avoid sexual activity, indicating that the groups might differ in the neural underpinnings of the behavioral component of sexual inhibition. In this fMRI study, transgender (n = 33) and cisgender (n = 34) participants performed an Approach Avoidance Task (AAT) assessing sexual inhibition. We found that over the entire sample, the task elicited brain activation commonly associated with general and sexual inhibition, for instance in the bilateral insula, right inferior parietal lobule, and right inferior and middle frontal gyri. Upon investigating group differences between transgender and cisgender participants, we mainly found similarities in neural activation during the task. However, there were group differences in regions involved in decision making processes (left middle temporal gyrus) and sexual response inhibition (right anterior cingulate cortex and left inferior parietal lobule). In order to investigate whether these group differences were modulated by testosterone levels, we performed ROI-analyses assessing the relationship between testosterone and neural activation during the AAT (controlling for sex assigned at birth), but no correlations were found. On the whole brain level, however, we found that testosterone correlated positively with cerebral activation in the right claustrum (a region associated with sexual arousal) during the approach of sexual stimuli in the transgender group. Overall, these findings indicate that transgender and cisgender individuals mostly show similarities in their neural response to a sexual Approach-Avoidance task, and that testosterone levels are unlikely to play an important role.

The neurofunctional basis of human aggression varies by levels of femininity

Aggression can be categorized into reactive aggression (RA) and proactive aggression (PA) based on their underlying motivations. However, previous research has rarely identified the relationship between femininity and RA/PA, and there is a lack of understanding regarding the femininity-related neurofunctional basis of these aggressive behaviors. Thus, this study first examined the relationships between femininity and aggression, then explored the aggression-by-femininity interactions on the fractional amplitude of low-frequency fluctuations using resting-state fMRI among 705 university participants (mean age = 19.14 ± 0.99). The behavioral data indicated that femininity was more negatively associated with RA and PA when masculinity was controlled for. Additionally, the neural data revealed that femininity-specific relationships of RA in the left middle occipital gyrus (i.e. individuals with low femininity had positive relationships between RA and the left middle occipital gyrus, whereas those with high femininity had negative relationships) as well as of PA in the left middle frontal gyrus (i.e. individuals with high femininity showed significant negative relationships, whereas those with low femininity did not exhibit significant relationships). These findings reflect that individuals with varying levels of femininity exhibit distinct neural bases when expressing different subtypes of aggression, which are associated with societal expectations of gender.

The Neural Correlates of Individual Differences in Reinforcement Learning during Pain Avoidance and Reward Seeking

Organisms learn to gain reward and avoid punishment through action-outcome associations. Reinforcement learning (RL) offers a critical framework to understand individual differences in this associative learning by assessing learning rate, action bias, pavlovian factor (i.e., the extent to which action values are influenced by stimulus values), and subjective impact of outcomes (i.e., motivation to seek reward and avoid punishment). Nevertheless, how these individual-level metrics are represented in the brain remains unclear. The current study leveraged fMRI in healthy humans and a probabilistic learning go/no-go task to characterize the neural correlates involved in learning to seek reward and avoid pain. Behaviorally, participants showed a higher learning rate during pain avoidance relative to reward seeking. Additionally, the subjective impact of outcomes was greater for reward trials and associated with lower response randomness. Our imaging findings showed that individual differences in learning rate and performance accuracy during avoidance learning were positively associated with activities of the dorsal anterior cingulate cortex, midcingulate cortex, and postcentral gyrus. In contrast, the pavlovian factor was represented in the precentral gyrus and superior frontal gyrus (SFG) during pain avoidance and reward seeking, respectively. Individual variation of the subjective impact of outcomes was positively predicted by activation of the left posterior cingulate cortex. Finally, action bias was represented by the supplementary motor area (SMA) and pre-SMA whereas the SFG played a role in restraining this action tendency. Together, these findings highlight for the first time the neural substrates of individual differences in the computational processes during RL.

A chemical signal in human female tears lowers aggression in males

Rodent tears contain social chemosignals with diverse effects, including blocking male aggression. Human tears also contain a chemosignal that lowers male testosterone, but its behavioral significance was unclear. Because reduced testosterone is associated with reduced aggression, we tested the hypothesis that human tears act like rodent tears to block male aggression. Using a standard behavioral paradigm, we found that sniffing emotional tears with no odor percept reduced human male aggression by 43.7%. To probe the peripheral brain substrates of this effect, we applied tears to 62 human olfactory receptors in vitro. We identified 4 receptors that responded in a dose-dependent manner to this stimulus. Finally, to probe the central brain substrates of this effect, we repeated the experiment concurrent with functional brain imaging. We found that sniffing tears increased functional connectivity between the neural substrates of olfaction and aggression, reducing overall levels of neural activity in the latter. Taken together, our results imply that like in rodents, a human tear-bound chemosignal lowers male aggression, a mechanism that likely relies on the structural and functional overlap in the brain substrates of olfaction and aggression. We suggest that tears are a mammalian-wide mechanism that provides a chemical blanket protecting against aggression.

Development of social feedback processing and responses in childhood: an fMRI test-replication design in two age cohorts

This study investigated behavioral and neural correlates underlying social feedback processing and subsequent aggressive behaviors in childhood in two age cohorts (test sample: n = 509/n = 385 and replication sample: n = 354/n = 195, 7-9 years old). Using a previously validated Social Network Aggression Task, we showed that negative social feedback resulted in most behavioral aggression, followed by less aggression after neutral and least aggression after positive feedback. Receiving positive and negative social feedback was associated with increased activity in the insula, medial prefrontal cortex and ventrolateral prefrontal cortex. Responding to feedback was associated with additional activation in the dorsolateral prefrontal cortex (DLPFC) following positive feedback. This DLPFC activation correlated negatively with aggression. Furthermore, age analyses showed that older children showed larger reductions in aggression following positive feedback and more neural activation in the DLPFC when responding to positive feedback compared to younger children. To assess the robustness of our results, we examined these processes in two independent behavioral/functional magnetic resonance imaging samples using equivalence testing, thereby contributing to replicable reports. Together, these findings demonstrate an important role of social saliency and regulatory processes where regulation of aggression rapidly develops between the ages of 7 and 9 years.

Modeling Suicidality with Multimodal Impulsivity Characterization in Participants with Mental Health Disorder

Introduction

Suicide is one of the leading causes of death across different age groups. The persistence of suicidal ideation and the progression of suicidal ideations to action could be related to impulsivity, the tendency to act on urges with low temporal latency, and little forethought. Quantifying impulsivity could thus help suicidality estimation and risk assessments in ideation-to-action suicidality frameworks.

Methods

To model suicidality with impulsivity quantification, we obtained questionnaires, behavioral tests, heart rate variability (HRV), and resting state functional magnetic resonance imaging measurements from 34 participants with mood disorders. The participants were categorized into three suicidality groups based on their Mini-International Neuropsychiatric Interview: none, low, and moderate to severe.

Results

Questionnaire and HRV-based impulsivity measures were significantly different between the suicidality groups with higher subscales of impulsivity associated with higher suicidality. A multimodal system to characterize impulsivity objectively resulted in a classification accuracy of 96.77% in the three-class suicidality group prediction task.

Conclusions

This study elucidates the relative sensitivity of various impulsivity measures in differentiating participants with suicidality and demonstrates suicidality prediction with high accuracy using a multimodal objective impulsivity characterization in participants with mood disorders.

Effect of transcranial direct current stimulation over the left dorsolateral prefrontal cortex on the aggressive behavior in methamphetamine addicts

Aggressive behavior of drug addicts threatens human security and social stability, and Methamphetamine (MA) addicts show especially aggressive behavior. Researches showed that the decreased activity of dorsolateral prefrontal cortex (DLPFC) is closely related to violence and aggression, and continuous transcranial direct current stimulation (tDCS) on DLPFC can increase the activity of this position. So, the purpose of this study was to investigate the effect of tDCS on DLPFC for the aggressive behavior of MA addicts. Ninety MA addicts were recruited and randomly divided into anodal tDCS group, cathode tDCS group and sham tDCS group (current intensity was set as 2 mA, 2 mA and 0 mA, respectively). The tDCS intervention was conducted twice a day for five consecutive days. Taylor Aggression Paradigm (TAP) was used to measure the proactive aggressiveness and reactive aggressiveness of MA addicts at different time points (Pretest, Day 1, and Day 5). At the same time, we also recruited 30 healthy adult males as healthy controls, and measured their aggressiveness through TAP for comparative analysis. The results showed that the aggressiveness of MA addicts was significantly higher than that of healthy controls. The aggressiveness of MA addicts was effectively reduced by the anode intervention of tDCS on the left DLPFC, especially when they were subjected to high-intensity provocation, the 2-way interaction between time and tDCS group was statistically significant (F_4,164 = 2.939, P = 0.022, η_p² = 0.067). This study can provide a reference for how to correct the aggressive behavior of MA addicts.

Mapping frontoinsular cortex from diffusion microstructure

We developed a novel method for mapping the location, surface area, thickness, and volume of frontoinsular cortex (FI) using structural and diffusion magnetic resonance imaging. FI lies in the ventral part of anterior insular cortex and is characterized by its distinctive population von Economo neurons (VENs). Functional neuroimaging studies have revealed its involvement in affective processing, and histopathology has implicated VEN loss in behavioral-variant frontotemporal dementia and chronic alcoholism; however, structural neuroimaging of FI has been relatively limited. We delineated FI by jointly modeling cortical surface geometry and its coincident diffusion microstructure parameters. We found that neurite orientation dispersion in cortical gray matter can be used to map FI in specific individuals, and the derived measures reflect a range of behavioral factors in young adults from the Human Connectome Project (N=1052). FI volume was larger in the left hemisphere than the right (31%), and the percentage volume of FI was larger in women than men (15.3%). FI volume was associated with measures of decision-making (delay discounting, substance abuse), emotion (negative intrusive thinking and perception of hostility), and social behavior (theory of mind and working memory for faces). The common denominator is that larger FI size is related to greater self-control and social awareness.

How distinct functional insular subdivisions mediate interacting neurocognitive systems

Recent neurocognitive models propose that the insula serves as a hub of interoceptive awareness system, modulating 2 interplaying neurocognitive systems: The posterior insula (PI) receives and integrates various interoceptive signals; these signals are then transmitted to the anterior insula for processing higher-order representations into awareness, where the dorsal anterior insula (dAI) modulates the prefrontal self-control system and the ventral anterior insula (vAI) modulates the amygdala (AMG)-striatal reward-seeking circuit. We sought to test this view using a multimodal approach. We first used a resting-state functional magnetic resonance imaging (fMRI) approach with a sample of 120 undergraduate students. Then, we unpacked the neuro-cognitive association between insular connectivity and cognitive performance during an Iowa gambling fMRI task. Lastly, an independent Open Southwest University Longitudinal Imaging Multimodal dataset was used to validate the results. Findings suggested that the dAI was predominantly connected to the prefrontal regions; the vAI was primarily connected to the AMG-ventral-striatum system; and the PI was mainly connected to the visceral-sensorimotor system. Moreover, cognitive scores were positively correlated with FC between dAI and the self-control process of ventrolateral prefrontal cortex and were negatively correlated with FC between vAI and the reward-seeking process of orbitofrontal cortex and subgenual anterior cingulate cortex. The findings highlight the roles of our theorized subinsular functionality in the overall operation of the neural cognitive systems.

Neural correlates of impulse control behaviors in Parkinson's disease: Analysis of multimodal imaging data

BACKGROUND

Impulse control behaviors (ICB) are frequently observed in patients with Parkinson's disease (PD) and are characterized by compulsive and repetitive behavior resulting from the inability to resist internal drives.

OBJECTIVES

In this study, we aimed to provide a better understanding of structural and functional brain alterations and clinical parameters related to ICB in PD patients.

METHODS

We utilized a dataset from the Parkinson's Progression Markers Initiative including 36 patients with ICB (PDICB+) compared to 76 without ICB (PDICB-) and 61 healthy controls (HC). Using multimodal MRI data we assessed gray matter brain volume, white matter integrity, and graph topological properties at rest.

RESULTS

Compared with HC, PDICB+ showed reduced gray matter volume in the bilateral superior and middle temporal gyrus and in the right middle occipital gyrus. Compared with PDICB-, PDICB+ showed volume reduction in the left anterior insula. Depression and anxiety were more prevalent in PDICB+ than in PDICB- and HC. In PDICB+, lower gray matter volume in the precentral gyrus and medial frontal cortex, and higher axial diffusivity in the superior corona radiata were related to higher depression score. Both PD groups showed disrupted functional topological network pattern within the cingulate cortex compared with HC. PDICB+ vs PDICB- displayed reduced topological network pattern in the anterior cingulate cortex, insula, and nucleus accumbens.

CONCLUSIONS

Our results suggest that structural alterations in the insula and abnormal topological connectivity pattern in the salience network and the nucleus accumbens may lead to impaired decision making and hypersensitivity towards reward in PDICB+. Moreover, PDICB+ are more prone to suffer from depression and anxiety.

Musical Experience Relates to Insula-Based Functional Connectivity in Older Adults

Engaging in musical activities throughout the lifespan may protect against age-related cognitive decline and modify structural and functional connectivity in the brain. Prior research suggests that musical experience modulates brain regions that integrate different modalities of sensory information, such as the insula. Most of this research has been performed in individuals classified as professional musicians; however, general musical experiences across the lifespan may also confer beneficial effects on brain health in older adults. The current study investigated whether general musical experience, characterized using the Goldsmith Music Sophistication Index (Gold-MSI), was associated with functional connectivity in older adults (age = 65.7 ± 4.4, n = 69). We tested whether Gold-MSI was associated with individual differences in the functional connectivity of three a priori hypothesis-defined seed regions in the insula (i.e., dorsal anterior, ventral anterior, and posterior insula). We found that older adults with more musical experience showed greater functional connectivity between the dorsal anterior insula and the precentral and postcentral gyrus, and between the ventral anterior insula and diverse brain regions, including the insula and prefrontal cortex, and decreased functional connectivity between the ventral anterior insula and thalamus (voxel p < 0.01, cluster FWE p < 0.05). Follow-up correlation analyses showed that the singing ability subscale score was key in driving the association between functional connectivity differences and musical experience. Overall, our findings suggest that musical experience, even among non-professional musicians, is related to functional brain reorganization in older adults.

The brain correlates of hostile attribution bias and their relation to the displaced aggression

BACKGROUND

Hostile attribution bias (HAB) has been considered as a risk factor of various types of psychosocial adjustment problem, and contributes to displaced aggression (DA). The neural basis of HAB and the underlying mechanisms of how HAB predicts DA remain unclear.

METHODS

The current study used degree centrality (DC) and resting-sate functional connectivity (RSFC) to investigate the functional connection pattern related to HAB in 503 undergraduate students. Furthermore, the "Decoding" was used to investigate which psychological components the maps of the RSFC-behavior may be related to. Finally, to investigate whether and how the RSFC pattern, HAB predicts DA, we performed mediation analyses.

RESULTS

We found that HAB was negatively associated with DC in bilateral temporal poles (TP) and positively correlated with DC in the putamen and thalamus; Moreover, HAB was negatively associated with the strength of functional connectivity between TP and brain regions in the theory of mind network (ToM), and positively related to the strength of functional connectivity between the thalamus and regions in the ToM network. The "Decoding" showed the maps of the RSFC-behavior may involve the theory mind, autobiographic, language, comprehension and working memory. Mediation analysis further showed that HAB mediated the relationship between some neural correlates of the HAB and DA.

LIMITATIONS

The current results need to be further tested by experimental methods or longitudinal design in further studies.

CONCLUSIONS

These findings shed light on the neural underpinnings of HAB and provide a possible mediation model regarding the relationships among RSFC pattern, HAB, and displaced aggression.

Coping in Anger Episodes: Developmental Differences and Self-Efficacy Beliefs

Anger has been recognized as a natural emotion; however, its poor management in adolescence is associated with some adverse developmental outcomes. The aims of this study were to compare the antecedents and coping strategies of anger episodes between adolescents and adults and the role of perceived self-efficacy on the coping strategies. A total of 88 adolescents (44 female, M_age = 16.81 years, SD = 1.21) and 94 adults (49 female, M_age = 28.11 years, SD = 5.82) reported an anger episode and the coping strategy adopted. Participants also filled in the Regulatory Emotional Self-Efficacy Scale (RESE). The results show that there are no specific antecedents among only adolescents or adults, although there are differences between the two age groups. Furthermore, the results indicate a different use of coping strategies between adolescents and adults. Specifically, a greater propensity of adolescents to use more often maladaptive strategies such as avoidance and denial emerged, but in addiction inaction, considered an adaptive strategy, can also be found. However, although adults use less maladaptive coping strategies they report a high frequency of feeling of powerlessness. The adaptive differences in coping also are explained by the different levels of self-efficacy beliefs of the participants. These findings are discussed in the light of the adaptive role of the coping strategies.

Interactive Effects of HIV Infection and Cannabis Use on Insula Subregion Functional Connectivity

Chronic inflammation in the central nervous system is one mechanism through which human immunodeficiency virus (HIV) may lead to progressive cognitive decline. Given cannabis's (CB's) anti-inflammatory properties, use prevalence among people living with HIV (PLWH), and evidence implicating the insula in both, we examined independent and interactive effects of HIV and CB on insular circuitry, cognition, and immune function. We assessed resting-state functional connectivity (rsFC) of three insula subregions among 106 participants across four groups (co-occurring: HIV+/CB+; HIV-only: HIV+/CB-; CB-only: HIV-/CB+; controls: HIV-/CB-). Participants completed a neurocognitive battery assessing functioning across multiple domains and self-reported somatic complaints. Blood samples quantified immune function (T-cell counts) and inflammation (tumor necrosis factor alpha [TNF-α]). We observed interactive HIV × CB effects on rsFC strength between two anterior insula (aI) subregions and sensorimotor cortices such that, CB appeared to normalize altered rsFC among non-using PLWH. Specifically, compared to controls, HIV-only and CB-only groups displayed decreased dorsal anterior insula (DI) - postcentral gyrus rsFC and increased ventral anterior insula (VI) - supplementary motor area rsFC, whereas the co-occurring group displayed DI and VI rsFC more akin to that of controls. Altered DI - postcentral rsFC correlated with decreased processing speed and somatic complaints, but did not significantly correlate with inflammation (TNF-α). These outcomes implicate insula - sensorimotor neurocircuitries in HIV and CB and are consistent with prior work suggesting that CB use may normalize insula functioning among PLWH.

Reactive vs proactive aggression: A differential psychobiological profile? Conclusions derived from a systematic review

INTRODUCTION

Scholars have established subcategories of aggressive behavior in order to better understand this construct. Specifically, a classification based on motivational underpinnings makes it possible to differentiate between reactive and proactive aggression. Whereas reactive aggression is characterized by emotional lability, which means it is prone to impulsive reactions after provocation, proactive aggression is driven by low emotionality and high levels of instrumentality to obtain benefits. Some authors have conceived these two types as having a dichotomous nature, but others argue against this conceptualization, considering a complementary model more suitable. Hence, neuroscientific research might help to clarify discussions about their nature because biological markers do not present the same biases as psychological instruments.

AIM

The main objective of this study was to carry out a systematic review of studies that assess underlying biological markers (e.g., genes, brain, psychophysiological, and hormonal) of reactive and proactive aggression.

METHODS

To carry out this review, we followed PRISMA quality criteria for reviews, using five digital databases complemented by hand-searching.

RESULTS

The reading of 3993 abstracts led to the final inclusion of 157 papers that met all the inclusion criteria. The studies included allow us to conclude that heritability accounted for approximately 45% of the explained variance in both types of aggression, with 60% shared by both, especially, for overt and physical expression forms, and 10% specific to each type. Regarding allelic risk factors, whereas low functioning variants affecting serotonin transport and monoaminoxidase increased the risk of reactive aggression, high functioning variants were associated with proactive aggression. Furthermore, brain analysis revealed an overlap between the two types of aggression and alterations in the volume of the amygdala and temporal cortex. Moreover, high activation of the medial prefrontal cortex (PFC) facilitated proneness to both types of aggression equally. Whereas stimulation of the right ventrolateral (VLPFC) and dorsolateral (DLPFC) reduced proneness to aggression, inhibition of the left DLPFC increased it. Finally, psychophysiological and hormonal correlates in general did not clearly differentiate between the two types because they were equally related to each type (e.g., low basal cortisol and vagal variability in response to acute stress) CONCLUSIONS: This study reinforces the complementary model of both types of aggression instead of a dichotomous model. Additionally, this review also offers background about several treatments (i.e., pharmacological, non-invasive brain techniques…) to reduce aggression proneness.

Sustained attention alterations in major depressive disorder: A review of fMRI studies employing Go/No-Go and CPT tasks

BACKGROUND

Major depressive disorder (MDD) is a severe psychiatric condition characterized by selective cognitive dysfunctions. In this regard, functional Magnetic Resonance Imaging (fMRI) studies showed, both at resting state and during tasks, alterations in the brain functional networks involved in cognitive processes in MDD patients compared to controls. Among those, it seems that the attention network may have a role in the disease pathophysiology. Therefore, in this review we aim at summarizing the current fMRI evidence investigating sustained attention in MDD patients.

METHODS

We conducted a search on PubMed on case-control studies on MDD employing fMRI acquisitions during Go/No-Go and continuous performance tasks. A total of 12 studies have been included in the review.

RESULTS

Overall, the majority of fMRI studies reported quantitative alterations in the response to attentive tasks in selective brain regions, including the prefrontal cortex, the cingulate cortex, the temporal and parietal lobes, the insula and the precuneus, which are key nodes of the attention, the executive, and the default mode networks.

LIMITATIONS

The heterogeneity in the study designs, fMRI acquisition techniques and processing methods have limited the generalizability of the results.

CONCLUSIONS

The results from the included studies showed the presence of alterations in the activation patterns of regions involved in sustained attention in MDD, which are in line with current evidence and seemed to explain some of the key symptoms of depression. However, given the paucity and heterogeneity of studies available, it may be worthwhile to continue investigating the attentional domain in MDD with ad-hoc study designs to retrieve more robust evidence.

Structural and functional biomarkers of the insula subregions predict sex differences in aggression subscales

Aggression is a common and complex social behavior that is associated with violence and mental diseases. Although sex differences were observed in aggression, the neural mechanism for the effect of sex on aggression behaviors remains unclear, especially in specific subscales of aggression. In this study, we investigated the effects of sex on aggression subscales, gray matter volume (GMV), and functional connectivity (FC) of each insula subregion as well as the correlation of aggression subscales with GMV and FC. This study found that sex significantly influenced (a) physical aggression, anger, and hostility; (b) the GMV of all insula subregions; and (c) the FC of the dorsal agranular insula (dIa), dorsal dysgranular insula (dId), and ventral dysgranular and granular insula (vId_vIg). Additionally, mediation analysis revealed that the GMV of bilateral dIa mediates the association between sex and physical aggression, and left dId–left medial orbital superior frontal gyrus FC mediates the relationship between sex and anger. These findings revealed the neural mechanism underlying the sex differences in aggression subscales and the important role of the insula in aggression differences between males and females. This finding could potentially explain sexual dimorphism in neuropsychiatric disorders and improve dysregulated aggressive behavior.

Threat Detection in Nearby Space Mobilizes Human Ventral Premotor Cortex, Intraparietal Sulcus, and Amygdala

In the monkey brain, the precentral gyrus and ventral intraparietal area are two interconnected brain regions that form a system for detecting and responding to events in nearby “peripersonal” space (PPS), with threat detection as one of its major functions. Behavioral studies point toward a similar defensive function of PPS in humans. Here, our aim was to find support for this hypothesis by investigating if homolog regions in the human brain respond more strongly to approaching threatening stimuli. During fMRI scanning, naturalistic social stimuli were presented in a 3D virtual environment. Our results showed that the ventral premotor cortex and intraparietal sulcus responded more strongly to threatening stimuli entering PPS. Moreover, we found evidence for the involvement of the amygdala and anterior insula in processing threats. We propose that the defensive function of PPS may be supported by a subcortical circuit that sends information about the relevance of the stimulus to the premotor cortex and intraparietal sulcus, where action preparation is facilitated when necessary.

Aggression in borderline personality disorder: A systematic review of neuroimaging studies

Aggressive behaviors are prevalent among patients with Borderline Personality Disorder (BPD). Neuroimaging studies have linked aggression in BPD patients to neurochemical, structural, functional, and metabolic alterations in various brain regions, especially in frontal-limbic areas. This systematic review summarizes current neuroimaging results on aggression among BPD patients and provides an overview of relevant brain mechanisms. A systematic search of PubMed and Web of Science databases, in addition to manual check of references, identified thirty-two eligible articles, including two magnetic resonance spectrum (MRS), thirteen structural magnetic resonance imaging (sMRI), six functional magnetic resonance imaging (fMRI), and eleven positron emission tomography (PET) studies. The reviewed studies have highlighted the abnormalities in prefrontal cortices and limbic structures including amygdala and hippocampus. Less studies have zoomed in the roles of parietal and temporal regions or taken a network perspective. Connectivity studies have shed light on the importance of the frontal-limbic interactions in regulating aggression. Conflicted findings might be attributed to disparity in controlling gender, anatomical subdivisions, and comorbidities, which shall be considered in future studies.

Alcohol use and interoception - A narrative review

Interoception, defined as the ability to perceive and interpret body signals, may play an important role in alcohol use disorder (AUD). Earlier studies suggested an association between interoception impairment and known risk factors for AUD (e.g., alexithymia, emotion dysregulation, impulsivity, pain). Neurobiological studies show that the neurotoxicity of alcohol affects various elements of the interoceptive system (especially the insula) at structural and functional levels, with differential short/long term impacts. Conversely, primary interoceptive impairments may promote alcohol consumption and foster the evolution towards addiction. Despite convincing evidence demonstrating that interoception impairment may be an important contributor to the development and course of AUD, only a few studies directly evaluated interoceptive abilities in AUD. The research shows that interoceptive accuracy, the objective component of interoception, is lower in AUD individuals, and is correlated with craving and emotion dysregulation. Interoceptive sensibility is in turn higher in AUD individuals compared to healthy controls. Moreover, there is evidence that therapy focused on improving the ability to sense signals from the body in addiction treatment is effective. However, important methodological limitations in interoceptive measures persist, and it is therefore necessary to further investigate the associations between interoception and AUD.

Structural covariance of amygdala subregions is associated with trait aggression and endogenous testosterone in healthy individuals

Many studies point toward volume reductions in the amygdala as a potential neurostructural marker for trait aggression. However, most of these findings stem from clinical samples, rendering unclear whether the findings generalize to non-clinical populations. Furthermore, the notion of neural networks suggests that interregional correlations in gray matter volume (i.e., structural covariance) can explain individual differences in aggressive behavior beyond local univariate associations. Here, we tested whether structural covariance between amygdala subregions and the rest of the brain is associated with self-reported aggression in a large sample of healthy young students (n = 263; 49% women). Salivary testosterone concentrations were measured for a subset of n = 40 male and n = 36 female subjects, allowing us to investigate the influence of endogenous testosterone on structural covariance. Aggressive individuals showed enhanced covariance between left superficial amygdala (SFA) and left dorsal anterior insula (dAI), but lower covariance between right laterobasal amygdala (LBA) and right dorsolateral prefrontal cortex (dlPFC). These structural patterns overlap with functional networks involved in the genesis and regulation of aggressive behavior, respectively. With increasing endogenous testosterone, we observed stronger structural covariance between right centromedial amygdala (CMA) and right medial prefrontal cortex in men and between left CMA and bilateral orbitofrontal cortex in women. These results speak for structural covariance of amygdala subregions as a robust correlate of trait aggression in healthy individuals. Moreover, regions that showed structural covariance with the amygdala modulated by either testosterone or aggression did not overlap, suggesting a complex role of testosterone in human social behavior beyond facilitating aggressiveness.

A meta-analysis on shared and distinct neural correlates of the decision-making underlying altruistic and retaliatory punishment

Individuals who violate social norms will most likely face social punishment sanctions. Those sanctions are based on different motivation aspects, depending on the context. Altruistic punishment occurs if punishment aims to re‐establish the social norms even at cost for the punisher. Retaliatory punishment is driven by anger or spite and aims to harm the other. While neuroimaging research highlighted the neural networks supporting decision‐making in both types of punishment in isolation, it remains unclear whether they rely on the same or distinct neural systems. We ran an activation likelihood estimation meta‐analysis on functional magnetic resonance imaging data on 24 altruistic and 19 retaliatory punishment studies to investigate the neural correlates of decision‐making underlying social punishment and whether altruistic and retaliatory punishments share similar brain networks. Social punishment reliably activated the bilateral insula, inferior frontal gyrus, midcingulate cortex (MCC), and superior and medial frontal gyri. This network largely overlapped with activation clusters found for altruistic punishment. However, retaliatory punishment revealed only one cluster in a posterior part of the MCC, which was not recruited in altruistic punishment. Our results support previous models on social punishment and highlight differential involvement of the MCC in altruistic and retaliatory punishments, reflecting the underlying different motivations.

Assessing Impulsivity in Humans and Rodents: Taking the Translational Road

Impulsivity is a multidimensional construct encompassing domains of behavioral inhibition as well as of decision making. It is often adaptive and associated with fast responses, being in that sense physiological. However, abnormal manifestations of impulsive behavior can be observed in contexts of drug abuse and attention-deficit/hyperactivity disorder (ADHD), among others. A number of tools have therefore been devised to assess the different facets of impulsivity in both normal and pathological contexts. In this narrative review, we systematize behavioral and self-reported measures of impulsivity and critically discuss their constructs and limitations, establishing a parallel between assessments in humans and rodents. The first rely on paradigms that are typically designed to assess a specific dimension of impulsivity, within either impulsive action (inability to suppress a prepotent action) or impulsive choice, which implies a decision that weighs the costs and benefits of the options. On the other hand, self-reported measures are performed through questionnaires, allowing assessment of impulsivity dimensions that would be difficult to mimic in an experimental setting (e.g., positive/negative urgency and lack of premeditation) and which are therefore difficult (if not impossible) to measure in rodents.

The neurobiology of human aggressive behavior: Neuroimaging, genetic, and neurochemical aspects

In modern societies, there is a strive to improve the quality of life related to risk of crimes which inevitably requires a better understanding of brain determinants and mediators of aggression. Neurobiology provides powerful tools to achieve this end. Pre-clinical and clinical studies show that changes in regional volumes, metabolism-function and connectivity within specific neural networks are related to aggression. Subregions of prefrontal cortex, insula, amygdala, basal ganglia and hippocampus play a major role within these circuits and have been consistently implicated in biology of aggression. Genetic variations in proteins regulating the synthesis, degradation, and transport of serotonin and dopamine as well as their signal transduction have been found to mediate behavioral variability observed in aggression. Gene-gene and gene-environment interactions represent additional important risk factors for aggressiveness. Considering the social burden of pathological forms of aggression, more basic and translational studies should be conducted to accelerate applications to clinical practice, justice courts, and policy making.

Do anger perception and the experience of anger share common neural mechanisms? Coordinate-based meta-analytic evidence of similar and different mechanisms from functional neuroimaging studies

The neural bases of anger are still a matter of debate. In particular we do not know whether anger perception and anger experience rely on similar or different neural mechanisms. To study this topic, we performed activation-likelihood-estimation meta-analyses of human neuroimaging studies on 61 previous studies on anger perception and experience. Anger perception analysis resulted in significant activation in the amygdala, the right superior temporal gyrus, the right fusiform gyrus and the right IFG, thus revealing the role of perceptual temporal areas for perceiving angry stimuli. Anger experience analysis resulted in the bilateral activations of the insula and the ventrolateral prefrontal cortex, thus revealing a role for these areas in the subjective experience of anger and, possibly, in a subsequent evaluation of the situation. Conjunction analyses revealed a common area localized in the right inferior frontal gyrus, probably involved in the conceptualization of anger for both perception and experience. Altogether these results provide new insights on the functional architecture underlying the neural processing of anger that involves separate and joint mechanisms. According to our tentative model, angry stimuli are processed by temporal areas, such as the superior temporal gyrus, the fusiform gyrus and the amygdala; on the other hand, the subjective experience of anger mainly relies on the anterior insula; finally, this pattern of activations converges in the right IFG. This region seems to play a key role in the elaboration of a general meaning of this emotion, when anger is perceived or experienced.

Abnormal dynamics of functional connectivity in first-episode and treatment-naive patients with obsessive-compulsive disorder

AIM

The aim of this study was to assess the whole-brain dynamic functional connectivity of first-episode and treatment-naive patients with obsessive-compulsive disorder (OCD) and to investigate the clinical correlations of abnormal changes in dynamic functional connectivity.

METHODS

Twenty-nine patients in our hospital diagnosed with first-episode OCD and 29 healthy controls matched for age, sex, and education were included in our study. Resting-state functional magnetic resonance imaging scans were performed on a 3.0-Tesla magnetic resonance scanner in our hospital. Three temporal metrics of connectivity state expression were calculated: (i) fraction of time; (ii) mean dwell time; and (iii) number of transitions. The Yale-Brown Obsessive-Compulsive Scale was used to assess the severity of OCD symptoms.

RESULTS

In the comparison of dynamic functional connectivity indicators, we found that there were significant differences in the number of transitions among the four functional connectivity states but no significant differences in the fraction of time or the mean dwell time. The total Yale-Brown Obsessive-Compulsive Scale score was positively correlated with the number of transitions. In the validation analysis, when the size of the sliding window changed, there was still a significant difference in the number of transitions between OCD patients and healthy controls.

CONCLUSION

The functional networks of OCD patients have lost the correct dynamic rhythm, which may be considered as a potential marker for OCD and for new directions for its intervention.

Functional topography of anger and aggression in the human cerebellum

New insights into the functional neuroanatomic correlates of emotions point toward the involvement of the cerebellum in anger and aggression. To identify cerebellar regions commonly activated in tasks examining the experience of anger and threat as well as exerting an aggressive response, two coordinate-based activation likelihood estimation meta-analyses reporting a total of 57 cerebellar activation foci from 819 participants were performed. For anger processing (18 studies), results showed significant clusters in the bilateral posterior cerebellum, overlapping with results from previous meta-analyses on emotion processing, and implying functional connectivity to cognitive, limbic, and social canonic networks in the cerebral cortex. By contrast, active aggression expression (10 studies) was associated with significant clusters in more anterior regions of the cerebellum, overlapping with cerebellar somatosensory and motor regions and displaying functional connectivity with the somatomotor and default mode network. This study not only strengthens the notion that the cerebellum is involved in emotion processing, but also provides the first quantitative evidence for distinct cerebellar functional activation patterns related to anger and aggression.

Meta-analytic evidence for a joint neural mechanism underlying response inhibition and state anger

Although anger may weaken response inhibition (RI) by allowing outbursts to bypass deliberate processing, it is equally likely that RI deficits precipitate a state of anger (SA). In adolescents, for instance, anger occurs more frequently and often leads to escalating aggressive behaviors. Even though RI is considered a key component in explaining individual differences in SA expression, the neural overlap between SA and RI remains elusive. Here, we aimed to meta-analytically revisit and update the neural correlates of motor RI, to determine a consistent neural architecture of SA, and to identify their joint neural network. Considering that inhibitory abilities follow a protracted maturation until early adulthood, we additionally computed RI meta-analyses in youths and adults. Using activation likelihood estimation, we calculated twelve meta-analyses across 157 RI and 39 SA experiments on healthy individuals. Consistent with previous findings, RI was associated with a broad frontoparietal network including the anterior insula/inferior frontal gyrus (aI/IFG), premotor and midcingulate cortices, extending into right temporoparietal areas. Youths showed convergent activity in right midcingulate and medial prefrontal areas, left aI/IFG, and the temporal poles. SA, on the other hand, reliably recruited the right aI/IFG and anterior cingulate cortex. Conjunction analyses between RI and SA yielded a single convergence cluster in the right aI/IFG. While frontoparietal networks and bilateral aI are ubiquitously recruited during RI, the right aI/IFG cluster likely represents a node in a dynamically-adjusting monitoring network that integrates salient information thereby facilitating the execution of goal-directed behaviors under highly unpredictable scenarios.

Specific cortical and subcortical alterations for reactive and proactive aggression in children and adolescents with disruptive behavior

Maladaptive aggression, as present in conduct disorder (CD) and, to a lesser extent, oppositional defiant disorder (ODD), has been associated with structural alterations in various brain regions, such as ventromedial prefrontal cortex (vmPFC), anterior cingulate cortex (ACC), amygdala, insula and ventral striatum. Although aggression can be subdivided into reactive and proactive subtypes, no neuroimaging studies have yet investigated if any structural brain alterations are associated with either of the subtypes specifically. Here we investigated associations between aggression subtypes, CU traits and ADHD symptoms in predefined regions of interest.

T1-weighted magnetic resonance images were acquired from 158 children and adolescents with disruptive behavior (ODD/CD) and 96 controls in a multi-center study (aged 8–18). Aggression subtypes were assessed by questionnaires filled in by participants and their parents. Cortical volume and subcortical volumes and shape were determined using Freesurfer and the FMRIB integrated registration and segmentation tool. Associations between volumes and continuous measures of aggression were established using multilevel linear mixed effects models.

Proactive aggression was negatively associated with amygdala volume (b = -10.7, p = 0.02), while reactive aggression was negatively associated with insula volume (b = -21.7, p = 0.01). No associations were found with CU traits or ADHD symptomatology. Classical group comparison showed that children and adolescents with disruptive behavior had smaller volumes than controls in (bilateral) vmPFC (p = 0.003) with modest effect size and a reduced shape in the anterior part of the left ventral striatum (p = 0.005).

Our study showed negative associations between reactive aggression and volumes in a region involved in threat responsivity and between proactive aggression and a region linked to empathy. This provides evidence for aggression subtype-specific alterations in brain structure which may provide useful insights for clinical practice.

Gray Matter Deficits and Dysfunction in the Insula Among Individuals With Intermittent Explosive Disorder

Although numerous neuroimaging studies have evaluated the characteristics of intermittent explosive disorder (IED), studies on the structural alterations and focal dysfunction in the brain in this condition are limited. This study aimed to identify gray matter deficits and functional alterations in individuals with IED using voxel-based morphometry (VBM) and functional magnetic resonance imaging (fMRI) analyses. Fifteen men with IED and 15 age- and sex-matched healthy controls participated in this study. Gray matter volume and brain activation while viewing the anger-inducing films were measured using 7T MRI. VBM results indicated that individuals with IED had significantly reduced gray matter volume in the insula, amygdala, and orbitofrontal area, relative to controls. Gray matter volume in the left insula was negatively correlated with composite aggression scores. fMRI results demonstrated that relative to healthy controls, individuals with IED showed greater activation in the insula, putamen, anterior cingulate cortex, and amygdala during anger processing. Left insular activity was positively correlated with composite aggression scores. Collectively, these findings suggest that structural and functional alterations in the left insula are linked to IED; this provides insight into the neural mechanisms underlying IED.

Multidimensional measure of aggression in adolescents: Croatian validation of the Peer Conflict Scale

Background

In order to adequately assess aggression in adolescence, the Peer Conflict Scale (PCS) was developed. It evaluates both forms and functions of aggression (i.e. proactive overt, proactive relational, reactive overt and reactive relational aggression). The goal of this study was to examine the validity and reliability of the Croatian version of the Peer Conflict Scale.

Participants and procedure

The total sample consisted of 656 high school students from the City of Zagreb (age range 16-17, 55.33% boys). Independent exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were conducted to determine the factor structure, and the best fitting model of the PCS on a Croatian sample.

Results

Both results of EFA and CFA support a proposed four-factor model of the instrument. Reliabilities of the instrument’s scales were acceptable. The measurement invariance across gender was established. In order to analyse the construct validity of the PCS, relations between aggression subtypes and the theoretically meaningful variable, i.e. anxiety, were assessed. Reactive rela-tional aggression had the highest correlation with anxiety, while proactive overt aggression did not correlate significantly with anxiety. Furthermore, gender differences in aggression subtypes were assessed, and were in accordance with past research.

Conclusions

Our study verifies the reliability, factor structure and construct validity of PCS in a sample of Croatian adolescents. However, the results of this study suggest that the response format should be changed. Furthermore, some items did not match well with corresponding factors and the best fitting model was the one in which those items were excluded. Therefore, we suggest that two items should be replaced with new ones.

The effect of insular cortex lesion on hyperacusis-like behavior in rats

Background and objectives: Hyperacusis is hypersensitivity and extreme response to the intensity of sound that is tolerable in normal subjects. The mechanisms underlying hyperacusis has not been well understood, specially the role of insular cortex. The aim of this study is to investigate the role of insular cortex in hyperacusis like behavior. Material and methods: The number of 33 male wistar rats weighting 170-250 gr were allocated randomly in three groups; control, sham, and insular lesion. Auditory startle responses (ASR) to different intensities of stimuli (70, 80, 90, 100, and110 dB without background noise as well as 110 dB in the presence of 70, 80 dB background noise) were measured before and up to four weeks after intervention. Results: Data analyses showed an increase in ASR to 100 dB stimulus without background noise one week after insular lesion, and increased responses to other intensities two weeks after lesion. Furthermore, there was a decrease in ASR to 110 dB stimulus with 80 dB background noise two weeks after insular lesion. However, no significant difference was observed in 70 dB background noise. The changes in ASR lasts at least four weeks.Conclusion: The findings indicated that there was an increase in ASR in the absence of background noise following cortical excititoxic lesion limited to insular cortex, while there was a decrease in responses in the presence of background noise which suggests possible increased sensitivity to sound loudness as a hyperacusis-like phenomenon. The study showed a significant relationship between insular cortex lesion and ASR in rats.

Neural correlates of intertemporal choice in aggressive behavior

People often have to make decisions between immediate rewards and more long-term goals. Such intertemporal judgments are often investigated in the context of monetary choice or drug use, yet not in regard to aggressive behavior. We combined a novel intertemporal aggression paradigm with functional neuroimaging to examine the role of temporal delay in aggressive behavior and the neural correlates thereof. Sixty-one participants (aged 18-22 years; 37 females) exhibited substantial variability in the extent to which they selected immediate acts of lesser aggression versus delayed acts of greater aggression against a same-sex opponent. Choosing delayed-yet-more-severe aggression was increased by provocation and associated with greater self-control. Preferences for delayed aggression were associated with greater activity in the ventromedial prefrontal cortex (VMPFC) during such choices, and reduced functional connectivity between the VMPFC and brain regions implicated in motor impulsivity. Preferences for immediate aggression were associated with reduced functional connectivity between the VMPFC and the frontoparietal control network. Dispositionally aggressive participants exhibited reduced VMPFC activity, which partially explained and suppressed their preferences for delayed aggression. Blunted VMPFC activity may thus be a neural mechanism that promotes reactive aggression towards provocateurs among dispositionally aggressive individuals. These findings demonstrate the utility of an intertemporal framework for investigating aggression and provide further evidence for the similar underlying neurobiology between aggression and other rewarding behaviors.

Brain structures and functional connectivity associated with individual differences in trait proactive aggression

Although considerable efforts have been made to understand the neural underpinnings of (state) reactive aggression, which is triggered by provocation or perceived threat, little is known about the neural correlates of proactive aggression, which is driven by instrumental motivations to obtain personal gains through aggressive means and which varies dramatically across individuals in terms of tendency of appealing to such means. Here, by combining structural (grey matter density, GMD) and functional (resting-state functional connection, RSFC) fMRI, we investigated brain structures and functional networks related to trait proactive aggression. We found that individual differences in trait proactive aggression were positively associated with GMD in bilateral dorsolateral prefrontal cortex (DLPFC) and negatively correlated with GMD in posterior cingulate cortex (PCC); they were also negatively correlated with the strength of functional connectivity between left PCC and other brain regions, including right DLPFC, right IPL, right MPFC/ACC, and bilateral precuneus. These findings shed light on the differential brain bases of proactive and reactive aggressions and suggested the neural underpinnings of proactive aggression.

ERP study on the associations of peripheral oxytocin and prolactin with inhibitory processes involving emotional distraction

BACKGROUND

Child maltreatment is a major health and social welfare problem, with serious and longstanding consequences. Impulse control ability plays an important role in reducing the risk of child maltreatment. The aim of this study was to investigate the associations of oxytocin (OXT) and prolactin (PRL) with behavior inhibition using children's facial expressions (angry or neutral) as emotional distractions. This may clarify a part of the neuroendocrinological mechanism that modulates impulse control ability in the context of child caregiving.

METHODS

Participants were 16 females who had never been pregnant. Following venous blood sampling for OXT and PRL levels, participants performed an emotional Go/Nogo task during their follicular and luteal phases to test inhibitory control ability. Behavioral performance and event-related potentials (ERPs) during the task were measured.

RESULTS

The results showed that there were significant fixed effects of OXT on behavioral performance, as measured by sensitivity (d-prime). This suggests that high peripheral OXT levels may be associated with better performance on the emotional Go/Nogo task, regardless of emotional distractors. PRL was associated with inhibitory processes as reflected by the Nogo-N2 and Nogo-P3. Particularly, high PRL levels were associated with the Nogo-N2 latency extension with the emotional distractors.

CONCLUSIONS

Our findings suggest that OXT might be associated with improving behavioral performance regardless of emotional processes. It is suggested that processes related to PRL are related to premotor activities of behavioral inhibitions and emotions.

A Biobehavioral Validation of the Taylor Aggression Paradigm in Female Adolescents

This research assessed the behavioral, emotional, endocrinological and autonomic reactivity to the laboratory Taylor Aggression Paradigm (TAP) in a sample of healthy female adolescents. Twenty participants were induced with the TAP to behave aggressively (aggression group) and 20 age-matched participants were not induced to behave aggressively (control group). Regression analysis revealed that the aggression group displayed significant higher levels of aggressive behavior compared to the control group (χ² (2) = 255.50, p < 0.0001). Aggressive behavior was not related to self-reported measures of trait aggression, impulsiveness or psychopathy features. Regarding the biological responses, regression analysis on cortisol, missed the set level of significance (χ² (1) = 3.73, p = 0.054), but showed significant effects on heart rate as a function of aggression induction (χ² (1) = 5.81, p = 0.016). While aggression induction was associated with increased autonomic arousal (heart rate), the interpretation of the effects on cortisol warrant caution, given existing differences between groups at baseline and overly elevated cortisol attributable to the general experimental procedures and not the TAP per se. No differences were found with respect to testosterone. In summary, the present study lends preliminary support for the validity of the TAP and its use in female adolescents on a behavioral and autonomic level.

Effects of age, sex, and puberty on neural efficiency of cognitive and motor control in adolescents

Critical changes in adolescence involve brain cognitive maturation of inhibitory control processes that are essential for a myriad of adult functions. Cognitive control advances into adulthood as there is more flexible integration of component processes, including inhibitory control of conflicting information, overwriting inappropriate response tendencies, and amplifying relevant responses for accurate execution. Using a modified Stroop task with fMRI, we investigated the effects of age, sex, and puberty on brain functional correlates of cognitive and motor control in 87 boys and 91 girls across the adolescent age range. Results revealed dissociable brain systems for cognitive and motor control processes, whereby adolescents flexibly adapted neural responses to control demands. Specifically, when response repetitions facilitated planning-based action selection, frontoparietal-insular regions associated with cognitive control operations were less activated, whereas cortical-pallidal-cerebellar motor regions associated with motor skill acquisition, were more activated. Attenuated middle cingulate cortex activation occurred with older adolescent age for both motor control and cognitive control with automaticity from repetition learning. Sexual dimorphism for control operations occurred in extrastriate cortices involved in visuo-attentional selection: While boys enhanced extrastriate selection processes for motor control, girls activated these regions more for cognitive control. These sex differences were attenuated with more advanced pubertal stage. Together, our findings show that brain cognitive and motor control processes are segregated, demand-specific, more efficient in older adolescents, and differ between sexes relative to pubertal development. Our findings advance our understanding of how distributed brain activity and the neurodevelopment of automaticity enhances cognitive and motor control ability in adolescence.

The neural correlates of alcohol-related aggression

Alcohol intoxication is implicated in approximately half of all violent crimes. Over the past several decades, numerous theories have been proposed to account for the influence of alcohol on aggression. Nearly all of these theories imply that altered functioning in the prefrontal cortex is a proximal cause. In the present functional magnetic resonance imaging (fMRI) experiment, 50 healthy young men consumed either a low dose of alcohol or a placebo and completed an aggression paradigm against provocative and nonprovocative opponents. Provocation did not affect neural responses. However, relative to sober participants, during acts of aggression, intoxicated participants showed decreased activity in the prefrontal cortex, caudate, and ventral striatum, but heightened activation in the hippocampus. Among intoxicated participants, but not among sober participants, aggressive behavior was positively correlated with activation in the medial and dorsolateral prefrontal cortex. These results support theories that posit a role for prefrontal cortical dysfunction as an important factor in intoxicated aggression.

Putting out the blaze: The neural mechanisms underlying sexual inhibition

The successful inhibition of sexual thoughts, desires, and behaviors represents an essential ability for adequate functioning in our daily life. Evidence derived from lesion studies indicates a link between sexual inhibition and the general ability for behavioral and cognitive control. This is further supported by the high comorbidity of sexual compulsivity with other inhibition-related disorders. Here, we aimed at investigating whether sexual and general inhibition recruit overlapping or distinct neural correlates in the brain. Furthermore, we investigated the specificity of two different kinds of sexual inhibition: inhibition of sexually driven motor responses and inhibition of sexual incoming information. To this end, 22 healthy participants underwent functional Magnetic Resonance Imaging (fMRI) while performing a task requiring general response inhibition (Go/No-go), as well as cognitive and motivational sexual inhibition (Negative Affective Priming and Approach-Avoidance task). Our within-subject within-session design enabled the direct statistical comparison between general and sexual inhibitory mechanisms. The general inhibition task recruited mainly prefrontal and insular regions, replicating previous findings. In contrast, the two types of sexual inhibition activated both common and distinct neural networks. Whereas cognitive sexual inhibition engaged the inferior frontal gyrus, the orbitofrontal cortex and the fusiform gyrus, motivational sexual inhibition was characterized by a hypoactivation in the anterolateral prefrontal cortex. Both types of sexual inhibition recruited the inferior frontal gyrus and the inferotemporal cortex. However, the activity of the inferior frontal gyrus did not correlate with behavioral inhibitory scores. These results support the hypothesis of inhibitory processing being an emergent property of a functional network.

Neural mechanisms of the rejection-aggression link

Social rejection is a painful event that often increases aggression. However, the neural mechanisms of this rejection–aggression link remain unclear. A potential clue may be that rejected people often recruit the ventrolateral prefrontal cortex’s (VLPFC) self-regulatory processes to manage the pain of rejection. Using functional MRI, we replicated previous links between rejection and activity in the brain’s mentalizing network, social pain network and VLPFC. VLPFC recruitment during rejection was associated with greater activity in the brain’s reward network (i.e. the ventral striatum) when individuals were given an opportunity to retaliate. This retaliation-related striatal response was associated with greater levels of retaliatory aggression. Dispositionally aggressive individuals exhibited less functional connectivity between the ventral striatum and the right VLPFC during aggression. This connectivity exerted a suppressing effect on dispositionally aggressive individuals’ greater aggressive responses to rejection. These results help explain how the pain of rejection and reward of revenge motivate rejected people to behave aggressively.

Alexithymia and reactive aggression: The role of the amygdala

Past research suggests an association between reactive aggression and alexithymia, but neural mechanisms underlying this association remain unknown. Furthermore, the relationship between proactive aggression and alexithymia remains untested. This study aimed to: (1) test whether alexithymia is more related to reactive than proactive aggression; and (2) determine whether amygdala, insula, and/or anterior cingulate cortical (ACC) volume could be neurobiological mechanisms for this association. One hundred and fifty-six community males completed the Reactive-Proactive Aggression Questionnaire and the Toronto Alexithymia Scale. Amygdala, insula, and ACC volumes were assessed using MRI. Alexithymia was positively associated with reactive but not proactive aggression. Alexithymia was positively and bilaterally associated with amygdala and anterior cingulate volumes. Reactive aggression was positively associated with right amygdala volume. Controlling for right amygdala volume rendered the alexithymia-reactive aggression relationship non-significant. Results suggest that increased right amygdala volume is a common neurobiological denominator for both alexithymia and reactive aggression. Findings suggest that greater right hemisphere activation may reflect a vulnerability to negative affect, which in turn predisposes to experiencing negative emotions leading to increased aggression. Findings are among the first to explicate the nature of the alexithymia-aggression relationship, with potential clinical implications.

Neural networks of aggression: ALE meta-analyses on trait and elicited aggression

There is considerable evidence that emotion dysregulation and self-control impairments lead to escalated aggression in populations with psychiatric disorders. However, convergent quantitative evidence on the neural network explaining how aggression arises is still lacking. To address this gap, peak activations extracted from extant functional magnetic resonance imaging (fMRI) studies were synthesized through coordinate-based meta-analyses. A systematic search in the PubMed database was conducted and 26 fMRI studies met the inclusion criteria. Three separate activation likelihood estimation (ALE) meta-analyses were performed on (1) individual differences in trait aggression (TA) studies, (2) individual differences in TA studies examining executive functioning, and (3) elicited aggression (EA) studies across fMRI behavioral paradigms. Ensuing clusters from ALE meta-analyses were further treated as seeds for follow-up investigations on consensus connectivity networks (CCN) delineated from meta-analytic connectivity modeling (MACM) and resting-state functional connectivity (RSFC) to further characterize their physiological functions. Finally, we obtained a data-driven functional characterization of the ensuing clusters and their networks. This approach offers a boarder view of the ensuing clusters using a boarder network perspective. In TA, aberrant brain activations were found only in the right precuneus. Follow-up analyses revealed that the precuneus seed was within the frontal-parietal network (FPN) associated with action inhibition, visuospatial processing and higher-level cognition. With further restricting to only experiments examining executive functioning, convergent evidence was found in the right rolandic operculum (RO), midcingulate cortex (MCC), precentral gyrus (PrG) and precuneus. Follow-up analyses suggested that RO, MCC and PrG may belong to a common cognitive control network, while the MCC seems to be the hub of this network. In EA, we only revealed a convergent region in the left postcentral gyrus. Follow-up CCN analyses and functional characterizations suggested that this region may also belong to the same cognitive control network found in the TA sub-analysis. Our results suggested that escalated aggression arises from abnormal precuneus activities within the FPN, disrupting the recruitment of other large-scale networks such as adaptive cognitive control network. Consequently, failure to recruit such a network results in an inability to generate adaptive responses, increasing the likelihood of acting aggressively.