White matter microstructure in the executive network associated with aggression in healthy adolescents and young adults

Association between white matter microstructural changes and aggressiveness. A case-control diffusion tensor imaging study

Research has focused on identifying neurobiological risk factors associated with aggressive behavior in order to improve prevention and treatment efforts. This study aimed to characterize microstructural differences in white matter (WM) integrity in individuals prone to aggression. We hypothesized that altered cerebral WM microstructure may underlie normal individual variability in aggression and tested this using a case-control design in healthy individuals. Diffusion tensor imaging (DTI) was used to examine WM changes in martial artists (n = 29) and age-matched controls (n = 31). We performed tract-based spatial statistics (TBSS) to identify differences in axial diffusivity (AD), fractional anisotropy (FA) and mean diffusivity (MD) between the two groups at the whole-brain level. Martial artists were significantly more aggressive than controls, with increased MD in parietal and occipital areas and increased AD in widespread fiber tracts in the frontal, parietal and temporal areas. Positive associations between AD/MD and (physical) appetitive aggression were identified in several clusters, including the corpus callosum, the superior longitudinal fasciculus and the corona radiata. Our study found evidence for WM microstructural changes associated with aggressiveness in a community case-control sample. Longitudinal studies with larger cohorts, taking into account the dimensional nature of aggressiveness, are needed to better understand the underlying neurobiology.

Neuroanatomical correlates of aggressiveness: a case-control voxel- and surface-based morphometric study

Aggression occurs across the population ranging on a symptom continuum. Most previous studies have used magnetic resonance imaging in clinical/forensic samples, which is associated with several confounding factors. The present study examined structural brain characteristics in two healthy samples differing only in their propensity for aggressive behavior. Voxel- and surface-based morphometry (SBM) analyses were performed on 29 male martial artists and 32 age-matched male controls. Martial artists had significantly increased mean gray matter volume in two frontal (left superior frontal gyrus and bilateral anterior cingulate cortex) and one parietal (bilateral posterior cingulate gyrus and precuneus) brain clusters compared to controls (whole brain: p < 0.001, cluster level: family-wise error (FWE)-corrected). SBM analyses revealed a trend for greater gyrification indices in martial artists compared to controls in the left lateral orbital frontal cortex and the left pars orbitalis (whole brain: p < 0.001, cluster level: FWE-corrected). The results indicate brain structural differences between martial artists and controls in frontal and parietal brain areas critical for emotion processing/inhibition of emotions as well as empathic processes. The present study highlights the importance of studying healthy subjects with a propensity for aggressive behavior in future structural MRI research on aggression.

Effects of childhood trauma on aggressive behaviors and hippocampal function: the modulation of COMT haplotypes

Background

Aggression is a commonly hostile behavior linked to the hippocampal activity. Childhood trauma (CT) exposure has been associated with altered sensitization of the hypothalamic-pituitary-adrenal (HPA) axis and hippocampal volume，which could increase violent aggressive behaviors. Additionally, Catechol-O-methyltransferase (COMT), the major dopamine metabolism enzyme, is implicated in stress responsivity, including aggression. Hence, CT exposure may affect aggression through the effect on the hippocampal function, which might also be modulated by the COMT variations.

Objectives

This study examined whether both CT and haplotypes of COMT moderate hippocampal function and thus affect human aggressive behavior.

Methods

We obtained bilateral hippocampal functional connectivity maps using resting state functional magnetic resonance imaging (MRI) data. COMT haplotype estimation was performed using Haploview 4.2 and PHASE 2.1. Then we constructed a moderated mediation model to study the effect of the CTQ × COMT on aggressive behavior.

Results

Three major haplotypes were generated from thirteen single nucleotide polymorphisms (SNPs) within the COMT gene and formed three haplotypes corresponding to high, medium, and low enzymatic activity of COMT. The results showed interactive relationships between the Childhood Trauma Questionnaire (CTQ) and COMT with respect to the functional connectivity (FC) of the bilateral hippocampus (HIP)-orbital frontal cortex (OFC). Specifically, CT experience predicted lower negative HIP-OFC coupling in the APS and HPS haplotypes corresponding to the medium and high enzymatic activity of COMT, but greater FC in the LPS haplotypes corresponding to the low enzymatic activity. We also observed a conditional mediation effect of the right HIP-OFC coupling in the link between COMT and aggressive behavior that was moderated by CT experience.

Conclusions

These results suggest that CT and COMT have a combined effect on aggressive behavior through hippocampal function. This mediation analysis sheds light on the influence of childhood experience on aggressive behavior in different genetic backgrounds.

Abnormalities in electroencephalographic microstates among violent patients with schizophrenia

Schizophrenia is often associated with a remarkably increased risk of violence, which has become a public health concern and brought a great economic burden. Recent studies have reported changes in the electroencephalograms (EEG) of patients with schizophrenia. The evidence for an association between EEG and violence in patients with schizophrenia is not conclusive. This study aimed to investigate EEG microstates in violent patients with schizophrenia. Forty-three violent patients with schizophrenia (the VS group) and 51 non-violent patients with schizophrenia (the NVS group) were included, and their EEG microstates were recorded using 21-Channel EEG recordings. The two groups were compared for differences of four microstate classes (A-D) with regards to three microstate parameters (duration, occurrence, and coverage). Compared with the NVS group, the VS group exhibited increased duration, occurrence, and coverage of microstate class A and decreased occurrence of microstate class B. The VS group also had lower probabilities of transitions from "B to C" and from "C to B", as compared with the NVS group. In addition, the MOAS score was positively correlated with the duration, occurrence, and coverage of microstate A. The present study found an abnormal pattern of EEG microstates in violent patients with schizophrenia, which might help clinicians identify patients with schizophrenia who might engaged in violence as well as develop intervention strategies at an early stage.

Lead exposure and antisocial behavior: A systematic review protocol

BACKGROUND

Lead exposure remains highly prevalent worldwide despite decades of research highlighting its link to numerous adverse health outcomes. In addition to well-documented effects on cognition, there is growing evidence of an association with antisocial behavior, including aggression, conduct problems, and crime. An updated systematic review on this topic, incorporating study evaluation and a developmental perspective on the outcome, can advance the state of the science on lead and inform global policy interventions to reduce exposure.

OBJECTIVES

We aim to evaluate the link between lead exposure and antisocial behavior. This association will be investigated via a systematic review of human epidemiological and experimental nonhuman mammalian studies.

METHODS

The systematic review protocol presented in this publication is informed by recommendations for the conduct of systematic reviews in toxicology and environmental health research (COSTER) and follows the study evaluation approach put forth by the U.S. EPA Integrated Risk Information System (IRIS) program.

DATA SOURCES

We will search the following electronic databases for relevant literature: PubMed, BIOSIS and Web of Science. Search results will be stored in EPA's Health and Environmental Research Online (HERO) database.

STUDY ELIGIBILITY AND CRITERIA

Eligible human epidemiological studies will include those evaluating any population exposed to lead at any lifestage via ingestion or inhalation exposure and considering an outcome of antisocial behavior based on any of the following criteria: psychiatric diagnoses (e.g., oppositional defiant disorder (ODD), conduct disorder (CD), disruptive behavior disorders (DBD)); violation of social norms (e.g., delinquency, criminality); and aggression. Eligible experimental animal studies will include those evaluating nonhuman mammalian studies exposed to lead via ingestion, inhalation, or injection exposure during any lifestage. The following outcomes will be considered relevant: aggression; antisocial behavior; and altered fear, anxiety, and stress response.

STUDY APPRAISAL AND SYNTHESIS METHODS

Screening will be conducted with assistance from an artificial intelligence application. Two independent reviewers for each data stream (human, animal) will screen studies with highest predicted relevance against pre-specified inclusion criteria at the title/abstract and full-text level. Study evaluation will be conducted using methods adapted from the U.S. EPA IRIS program. After data extraction, we will conduct a narrative review and quantitative meta-analysis on the human epidemiological studies as well as a narrative review of the experimental animal studies. We will evaluate the strength of each evidence stream separately and then will develop a summary evidence integration statement based on inference across evidence streams.

Abnormal neurite density and orientation dispersion in frontal lobe link to elevated hyperactive/impulsive behaviours in young adults with traumatic brain injury

Traumatic brain injury is a major public health concern. A significant proportion of individuals experience post-traumatic brain injury behavioural impairments, especially in attention and inhibitory control domains. Traditional diffusion-weighted MRI techniques, such as diffusion tensor imaging, have provided tools to assess white matter structural disruptions reflecting the long-term brain tissue alterations associated with traumatic brain injury. The recently developed neurite orientation dispersion and density imaging is a more advanced diffusion MRI modality, which provides more refined characterization of brain tissue microstructures by assessing the neurite orientation dispersion and neurite density properties. In this study, neurite orientation dispersion and density imaging data from 44 young adults with chronic traumatic brain injury (who had no prior-injury diagnoses of any sub-presentation of attention deficits/hyperactivity disorder or experience of severe inattentive and/or hyperactive behaviours) and 45 group-matched normal controls were investigated, to assess the post-injury morphometrical and microstructural brain alterations and their relationships with the behavioural outcomes. Maps of fractional anisotropy, neurite orientation dispersion index and neurite density index were calculated. Vertex-wise and voxel-wise analyses were conducted for grey matter and white matter, respectively. Post hoc region-of-interest-based analyses were also performed. Compared to the controls, the group of traumatic brain injury showed significantly increased orientation dispersion index and significantly decreased neurite density index in various grey matter regions, as well as significantly decreased orientation dispersion index in several white matter regions. Brain-behavioural association analyses indicated that the reduced neurite density index of the left precentral gyrus and the reduced orientation dispersion index of the left superior longitudinal fasciculus were significantly associated with elevated hyperactive/impulsive symptoms in the patients with traumatic brain injury. These findings suggest that post-injury chronical neurite intracellular volume and angular distribution anomalies in the frontal lobe, practically the precentral area, can significantly contribute to the onset of hyperactive/impulsive behaviours in young adults with traumatic brain injury.

Identification of violent patients with schizophrenia using a hybrid machine learning approach at the individual level

Despite numerous risk factors associated with violence in patients with schizophrenia, predicting and preventing violent behavior is still a challenge. At present, machine learning (ML) has become a promising strategy for guiding individualized assessment. To build an effective model to predict the risk of violence in patients with schizophrenia, we proposed a hybrid ML method to improve the prediction capability in 42 violent offenders with schizophrenia and 33 non-violent patients with schizophrenia. The results revealed that the final model, which combined multimodal data, achieved the highest prediction performance with an accuracy of 90.67%. Specifically, the model, which fused three modalities of neuroimaging data, achieved a better accuracy than other fused models. In addition, the msot discriminative neuroimaging features involved in the prefrontal-temporal cognitive circuit and striatum reward system, indicating that dysfunction in cortical-subcortical circuits might be associated with high risk of violence in patients with schizophrenia. This study provides the first evidence supporting that the combination of specific multimodal neuroimaging and clinical data in ML analysis can effectively identify violent patients with schizophrenia. Furthermore, this work is crucial for the development of neuro-prediction models that could facilitate individualized treatment and interventions for violent behaviors in patients with schizophrenia.

Cingulum White Matter Integrity as a Mediator Between Harm Avoidance and Hostility

As a textbook manifestation of an aggressive attitude, hostility can pose a serious threat to both an individual's life and the security of society at large. Past evidence suggests that some anxiety-related traits may be more prone to giving rise to hostility. However, many aspects of hostility, such as, determining the susceptible temperament for hostility, the neural basis of hostility, and the underlying mechanisms through which having a susceptible temperament generates hostility in a healthy brain, remain unclear. In this study, we sought to delve into these questions by assessing temperament and brain white matter integrity using self-report questionnaires and diffusion tensor imaging in a sizable sample of healthy adults (n = 357). First, we investigated the relationship between hostility and the four temperaments of the Cloninger model. Then, we investigated which white matter tracts were significantly correlated with hostility using a whole-brain analysis. Finally, we used a mediation analysis to explore the tripartite relationship between vulnerability temperament, the fractional anisotropy (FA) value of the white matter, and hostility. Our results suggest that a harm avoidance temperament may be susceptible to hostility and that the cingulum may be a key white matter region responsible for hostility. Based on these results, we developed a temperament-brain-attitude pathway showing how harm avoidance temperament could affect the brain and ultimately lead to hostility.

Childhood conduct problems are associated with reduced white matter fibre density and morphology

Childhood conduct problems are an important public health issue as these children are at-risk of adverse outcomes. Studies using diffusion Magnetic Resonance Imaging (dMRI) have found that conduct problems in adults are characterised by abnormal white-matter microstructure within a range of white matter pathways underpinning socio-emotional processing, while evidence within children and adolescents has been less conclusive based on non-specific diffusion tensor imaging metrics. Fixel-based analysis (FBA) provides measures of fibre density and morphology that are more sensitive to developmental changes in white matter microstructure. The current study used FBA to investigate whether childhood conduct problems were related both cross-sectionally and longitudinally to microstructural alterations within the fornix, inferior fronto-occipital fasciculus (IFOF), inferior longitudinal fasciculus (ILF), superior longitudinal fasciculus (SLF), and the uncinate fasciculus (UF). dMRI data was obtained for 130 children across two time-points in a community sample with high levels of externalising difficulties (age: time-point 1 = 9.47 - 11.86 years, time-point 2 = 10.67 -13.45 years). Conduct problems were indexed at each time-point using the Conduct Problems subscale of the parent-informant Strengths and Difficulties Questionnaire (SDQ). Conduct problems were related to lower fibre density in the fornix at both time-points, and in the ILF at time-point 2. We also observed lower fibre cross-section in the UF at time-point 1. The change in conduct problems did not predict longitudinal changes in white-matter microstructure across time-points. The current study suggests that childhood conduct problems are related to reduced fibre-specific microstructure within white matter fibre pathways implicated in socio-emotional functioning.

History of childhood maltreatment is associated with reduced fractional anisotropy of the accumbofrontal 'reward' tract in healthy adults

The deleterious outcomes associated with exposure to childhood maltreatment (CM) are well known and may be at least partially mediated by self-harm behaviors. It has been suggested that these self-harm behaviors serve as a means of decreasing negative mood states but the effects of CM on health outcomes may be much more sinister. A wealth of data suggest that CM may lead to experience-dependent changes in neural circuits underlying reward processes; processes associated with many harmful behaviors. The present study examined the relationship between a history of CM and the microstructure of a white matter tract that may be central to reward processes. Healthy adults (N = 122) were assessed with a diffusion tensor imaging (DTI) exam and the Childhood Trauma Questionnaire (CTQ). Probabilistic tractography was used to delineate the accumbofrontal "reward" tract, connecting the orbitofrontal cortex and nucleus accumbens, and measures of white matter microstructure were extracted. We then examined whether variation in CTQ scores were associated with variation in the microstructure of this tract as measured by fractional anisotropy (FA). After accounting for the effects of age and sex, the CTQ total score accounted for approximately 6% of the variance of FA in the accumbofrontal tract (F(3, 121) = 5.74; p = .001). Post hoc analyses indicated that the overall severity of CM, rather than a specific type of maltreatment, drove this result. These findings indicate that CM influences white matter microstructure in a fiber tract that is likely central to reward processes and adds to a growing literature implicating CM in long-term health-related outcomes.

Regions of white matter abnormalities in the arcuate fasciculus in veterans with anger and aggression problems

Aggression after military deployment is a common occurrence in veterans. Neurobiological research has shown that aggression is associated with a dysfunction in a network connecting brain regions implicated in threat processing and emotion regulation. However, aggression may also be related to deficits in networks underlying communication and social cognition. The uncinate and arcuate fasciculi are integral to these networks, thus studying potential abnormalities in these white matter connections can further our understanding of anger and aggression problems in military veterans. Here, we use diffusion tensor imaging tractography to investigate white matter microstructural properties of the uncinate fasciculus and the arcuate fasciculus in veterans with and without anger and aggression problems. A control tract, the parahippocampal cingulum was also included in the analyses. More specifically, fractional anisotropy (FA) estimates are derived along the trajectory from all fiber pathways and compared between both groups. No between-group FA differences are observed for the uncinate fasciculus and the cingulum, however parts of the arcuate fasciculus show a significantly lower FA in the group of veterans with aggression and anger problems. Our data suggest that abnormalities in arcuate fasciculus white matter connectivity that are related to self-regulation may play an important role in the etiology of anger and aggression in military veterans.

Neural Networks Mediating High-Level Mentalizing in Patients With Right Cerebral Hemispheric Gliomas

Mentalizing is the ability to understand others' mental state through external cues. It consists of two networks, namely low-level and high-level metalizing. Although it is an essential function in our daily social life, surgical resection of right cerebral hemisphere disturbs mentalizing processing with high possibility. In the past, little was known about the white matter related to high-level mentalizing, and the conservation of high-level mentalizing during surgery has not been a focus of attention. Therefore, the main purpose of this study was to examine the neural networks underlying high-level mentalizing and then, secondarily, investigate the usefulness of awake surgery in preserving the mentalizing network. A total of 20 patients with glioma localized in the right hemisphere who underwent awake surgery participated in this study. All patients were assigned to two groups: with or without intraoperative assessment of high-level mentalizing. Their high-level mentalizing abilities were assessed before surgery and 1 week and 3 months after surgery. At 3 months after surgery, only patients who received the intraoperative high-level mentalizing test showed the same score as normal healthy volunteers. The tract-based lesion symptom analysis was performed to confirm the severity of damage of associated fibers and high-level mentalizing accuracy. This analysis revealed the superior longitudinal fascicles (SLF) III and fronto-striatal tract (FST) to be associated with high-level mentalizing processing. Moreover, the voxel-based lesion symptom analysis demonstrated that resection of orbito-frontal cortex (OFC) causes persistent mentalizing dysfunction. Our study indicates that damage of the OFC and structural connectivity of the SLF and FST causes the disorder of mentalizing after surgery, and assessing high-level mentalizing during surgery may be useful to preserve these pathways.

White matter microstructure within the superior longitudinal fasciculus modulates the degree of response conflict indexed by N2 in healthy adults

Response conflict can be induced by priming multiple responses competing for control of action in trials. The N2 is one functionally-related cognitive control index for response conflict. And yet the underlying whiter matter neural substrates of inter-individual difference in conflict N2 remain unclear. So the aim of present study was to address the white matter microstructure of the N2 responsible for conflict by directly relating the amplitude cost of the event-related potential (ERP) N2 component to diffusion tensor imaging (DTI) indices in healthy subjects. Thirty healthy subjects underwent DTI scanning and electrophysiology recording during a modified Flanker task. N2 was a stimulus-locked negative ERP component. Fractional anisotropy (FA) was calculated based on DTI measures and was assumed to reflect the integrity of myelinate fiber bundles. Therefore, we tested the relationship between N2 amplitude and FA in brain white matter. Results showed that FA, an index for white matter characteristics, in the right superior longitudinal fasciculus (SLF) was significantly positively associated with N2 amplitude cost. The N2 amplitude cost also predicted response time (RT) cost in the Flanker task. Higher FA was associated with larger N2 amplitude cost, suggesting that changes in white matter integrity in the SLF may account for changes in efficient transmission of fronto-parietal modulatory conflict signals.

Functional Activation During a Cognitive Control Task in Healthy Youth Specific to Externalizing or Internalizing Behaviors

BACKGROUND

Externalizing behaviors are negative behaviors expressed outwardly, including rule breaking, aggression, and risk taking; internalizing behaviors are expressed inwardly, including depression, withdrawal, and anxiety. Such behavior can cause problems in early life and predict difficulties across the lifespan. There is evidence for a relationship between executive function and both externalizing and internalizing. However, although these behaviors occur along a spectrum, there is little neuroimaging research on this relationship in typically developing youth.

METHODS

We assessed 41 youth (10-19 years of age) using the Multi-Source Interference Task during functional magnetic resonance imaging and related the findings to self-reported externalizing and internalizing scores as measured by the Youth Self-Report. We performed a general linear model using FSL software; externalizing, internalizing, age, and sex were included in the model.

RESULTS

Compared to the control condition, the more difficult Multi-Source Interference Task interference condition was associated with greater engagement of the frontoparietal cognitive control system and decreased engagement of regions in the default mode network, based on a cluster threshold of Z > 3.1 (p = .01). When we examined regions uniquely associated with either internalizing or externalizing, we found that within the same group of subjects, higher externalizing behavior was associated with hyperactivity in the parietal lobe; in contrast, higher internalizing behavior was associated with increased activation in the medial prefrontal cortex.

CONCLUSIONS

These findings suggest that externalizing and internalizing may be associated with altered, but different, patterns of activation during cognitive control. This has implications for our understanding of the relationship between cognitive control and behavioral problems in youth.

White-matter tract abnormalities and antisocial behavior: A systematic review of diffusion tensor imaging studies across development

Antisocial behavior (AB), including aggression, violence, and theft, is thought be underpinned by abnormal functioning in networks of the brain critical to emotion processing, behavioral control, and reward-related learning. To better understand the abnormal functioning of these networks, research has begun to investigate the structural connections between brain regions implicated in AB using diffusion tensor imaging (DTI), which assesses white-matter tract microstructure. This systematic review integrates findings from 22 studies that examined the relationship between white-matter microstructure and AB across development. In contrast to a prior hypothesis that AB is associated with greater diffusivity specifically in the uncinate fasciculus, findings suggest that adult AB is associated with greater diffusivity across a range of white-matter tracts, including the uncinate fasciculus, inferior fronto-occipital fasciculus, cingulum, corticospinal tract, thalamic radiations, and corpus callosum. The pattern of findings among youth studies was inconclusive with both higher and lower diffusivity found across association, commissural, and projection and thalamic tracts.

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Antisocial behavior (AB) is characterized by impaired emotion and reward processing.

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These behaviors may develop from microstructural abnormalities of white-matter tracts.

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We provide a systematic review of 22 diffusion tensor imaging studies of AB.

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Adult AB was linked to greater diffusivity (“poorer integrity”) across a range of white-matter tracts.

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For youth AB, there were mixed findings.