Fractionating impulsivity: neuropsychiatric implications

Stage-dependent Neural Mechanisms in Human Methamphetamine Abstinence: Insights from the Digital Twin Brain Model

BACKGROUND

The reward circuits are crucial in treating human methamphetamine (MA) addiction, while the underlying action mechanisms may vary throughout the intervention process. This gap limits the identification of specific modulation targets and results in a "one-size-fits-all" approach. Demonstrating these specific neural signatures can inform tailored therapy and enhance precision medicine for MA addiction.

METHODS

A total of 62 MA addicts (21 females) and 57 healthy controls (16 females) were recruited. Longitudinal data were collected at the early and later stages of MA abstinence. We used probabilistic metastable substates to investigate macro-scale functional changes and established the digital twin brain model to determine key regions in abstinence from a causal, quantitative perspective. Molecular imaging, gene set, and cell-type enrichment analyses were conducted to provide a multi-scale neurobiological explanation. Computational drug repurposing analysis was performed to identify drug candidates with the potential to treat MA addiction.

RESULTS

We observed that brain regions within the reward circuits were crucial throughout the entire abstinence process. Molecular imaging, transcriptomic data, and cell-type analysis independently revealed that metabolic activities may play a more prominent role in early abstinence, while neuroplasticity is essential in both early and later abstinence. Identified putative drugs included approved medications for psychiatric symptoms, AIDS, and cancer.

CONCLUSIONS

Our work provides an integrative perspective on understanding the neural underpinnings of human MA abstinence and may inform future tailored therapies. Particularly, these findings support the stage-dependent nature of in-vivo human MA abstinence.

Edible cannabinoids impact meal structure and food impulsivity in female rats

Cannabinoid receptor agonists increase eating in a dose-dependent manner. However, the behavioral mechanisms by which cannabinoids modulate food intake control aren't clear, particularly in females. We utilized a rodent model of cannabinoid administration modeling a common route of cannabinoid consumption in humans: edibles. Herein, we administered the dual cannabinoid receptor agonist CP55940 in edible form to female rats and observed acute increases in standard chow intake due to an increase in meal size with no change in meal number. We further observed that the hyperphagic dose of edible CP55940 increases impulsive responding for sucrose, but this did not coincide with changes in motivation for sucrose. Finally, cannabinoids can affect anxiety-like behavior, but the acutely hyperphagic dose used in our studies had no effect on anxiety-like behavior. We conclude that edible cannabinoid administration delays satiation and increases impulsive eating behavior without impacting food motivation, potentially by reducing inhibitory control.

Exploratory structural neuroimaging examination of impulsivity in severe alcohol use disorder: Persistent implication of the ventral striatum

BACKGROUND

While Alcohol Use Disorder (AUD) is frequently associated with impulsivity, its structural brain substrates are still poorly defined. The triadic model of addiction postulates that impulsive behavior is regulated by an amygdalo-striatal impulsive subcomponent, a prefrontal and cerebellar reflective subcomponent, and an insular regulatory subcomponent. The objective of this study was thus to examine the relationships between self-evaluated impulsivity and structural brain abnormalities in patients with severe AUD (sAUD) using the triadic model as a theoretical framework.

METHODS

Twenty-two inpatients with sAUD and 17 Healthy Controls (HC) completed two impulsivity scales: the Barratt Impulsiveness Scale-11 (BIS-11), and the Urgency, Premeditation, Perseverance, Sensation Seeking, Positive Urgency Impulsive Behavior Scale (UPPS). They also underwent an anatomical MRI. The brain volumes of the regions described as involved in the three subcomponents of the triadic model were extracted.

RESULTS

The two groups did not significantly differ on self-reported impulsivity measures. However, the volumes of the caudate nuclei, executive cerebellum and insula were smaller in sAUD than in HC. In the sAUD group there were significant positive correlations between certain impulsivity measures and gray matter volume of the nucleus accumbens.

CONCLUSIONS

In sAUD, self-evaluated impulsivity specifically relates to the integrity of the ventral striatum that belongs to the impulsive subcomponent of the triadic neurocognitive model of addiction. It is not related to the integrity or deterioration of the brain regions that underlie the reflexive or regulatory sub-component. Although these results have methodological limitations, they are consistent with the impulsive/compulsive model of addiction and confirms the persistence of the relationship between impulsivity and ventral striatum in sAUD.

Effective connectivity analysis of response inhibition functional network

Introduction

Inhibition mechanisms are essential in daily life, helping individuals adapt to environmental demands. However, the causal interactions between large-scale functional networks involved in response inhibition remain poorly understood.

Methods

In this study, we examined the effective connectivity (EC) underlying inhibitory processes in the brain using dynamic causal modeling (DCM) and independent component analysis (ICA). We conducted a Go-NoGo fMRI task with 19 healthy participants to investigate these networks.

Results

Our results identified four functional networks activated during correct motor response inhibition: the salience network (SN), the right and left executive control networks (ECNs), and the ventral default mode network (vDMN). We observed a significant causal inhibitory influence from the vDMN to the left ECN (lECN). Under conditions of unsuccessful response inhibition, the SN, bilateral ECNs, and somatomotor network (SMN) were found to be prominently activated. Furthermore, we identified a significant correlation between the inhibitory influence from the SMN to the SN and the commission error rate. Finally, correlation analyses between self-reported impulsivity levels and causal network interactions revealed that highly impulsive individuals require greater interhemispheric integration between the right and left ECNs for effective inhibition, as well as a causal excitatory modulation from the right executive control network (rECN) to the vDMN.

Discussion

In summary, our study reveals complex hierarchical dynamics among functional networks during response inhibition. These findings offer valuable insight into the neural mechanisms supporting inhibition and provide avenues for future research on the neural underpinnings of this critical cognitive function across the lifespan.

A roadmap for transformative translational research on gambling disorder in the UK

The UK has one of the highest rates of recreational gambling in the world. Some vulnerable individuals progressively lose control over gambling and develop at-risk gambling or gambling disorder (GD), characterised by the compulsive pursuit of gambling. GD destroys lives and incurs massive costs to societies, yet only a few treatments are available. Failure to develop a wider range of interventions is in part due to a lack of funding that has slowed progress in the translational research necessary to understand the individual vulnerability to switch from controlled to compulsive gambling. Current preclinical models of GD do not operationalise the key clinical features of the human condition. The so-called "gambling tasks" for non-human mammals almost exclusively assess probabilistic decision-making, which is not real-world gambling. While they have provided insights into the psychological and neural mechanisms involved in the processing of gains and losses, these tasks have failed to capture those underlying real-world gambling and its compulsive manifestation in humans. Here, we highlight the strengths and weaknesses of current gambling-like behaviour tasks and suggest how their translational validity may be improved. We then propose a theoretical framework, the incentive habit theory of GD, which may prove useful for the operationalisation of the biobehavioural mechanisms of GD in preclinical models. We conclude with a list of recommendations for the development of next-generation preclinical models of GD and discuss how modern techniques in animal behavioural experimentation can be deployed in the context of GD preclinical research to bolster the translational pipeline.

SYSTEM XC- AS A MOLECULAR MECHANISM FOR EVOLUTIONARY NEW FORMS OF ADVANCED COGNITION

Human cognitive abilities are deeply rooted in evolutionary building blocks that maximize computation while maintaining efficiency. These abilities are not without evolutionary signatures; conserved processes like vision have undergone continual phylogenetic adjustments to better serve ecological niches. Conversely, more sophisticated forms of cognition may have required evolutionary innovations to transform existing neuronal processing to expand computational abilities. One such innovation is system xc- (Sxc), a cystine-glutamate antiporter predominantly localized to astrocytes that emerged in deuterostomes (e.g., vertebrates) after their divergence from protostomes over 550 million years ago. Previous evidence suggests that genetically modified rats that lack functional Sxc (MSxc) exhibit enhanced cocaine-seeking behavior. In this study, we deconstructed drug-seeking into its component behaviors, categorizing them as reliant on evolutionary conserved or newly evolved cognitive processes. Our results reveal that Sxc function is dispensable for conserved processes like visual, emotional, and hedonic processing, but critical for advanced, evolutionary new cognitive functions, particularly impulse control and decision making. Notably, we demonstrate a temporally specific reliance on Sxc during the learning phase of optimal decision-making, but not in maintaining established strategies. This is an important addition to our current understanding of astrocytes in non-homeostatic functions, indicating their critical role in computationally demanding phases of learning and memory. Unraveling evolutionary innovations like Sxc not only deepens our understanding of cognitive evolution but also paves the way for revolutionary, precision- targeted therapies in neuropsychiatric disorders, potentially transforming treatment paradigms and patient outcomes.

Fractionating impulsivity and reward-related phenotypes in adolescent mice

Adolescence is a developmental period characterized by changes in the brain and behavior, including heightened reward seeking, increased impulsivity, and elevated risk-taking behavior. It is also a sensitive period for the development of a number of behavioral and psychiatric disorders associated with pathological phenotypes of reward processing and impulsivity. Landmark human studies are charting the development of impulsivity and other reward-related phenotypes to identify the facets and timecourse of the adolescent phenotype. Collecting similar data from mice is important to enable molecular, cellular, and circuit-level interrogation of adolescent maturation of reward, motivation, and impulsive behavior. These complex phenotypes have traditionally been difficult to assay in adolescent mice. Here, using a combination of approaches including homecage testing, we tested a number of facets of reward seeking, impulsivity, motivation, and incentive salience attribution during adolescent development. We found that adolescent mice show increased reward seeking, impulsive action, and motivation. Interestingly, we found no effect of adolescence on impulsive choice, sign-tracking, reward-learning, or conditioned reinforcement. Overall, our studies set the stage for approaches to study multi-faceted phenotypes related to impulsivity and other reward-related behaviors in adolescent mice to examine the developmental trajectories of brain and behavior.

Serotonergic dysfunction in patients with impulse control disorders in Parkinson's disease

Impulse control disorders (ICDs) are frequent and particularly distressing neuropsychiatric symptoms in patients with Parkinson's disease (PD) which are related to impaired behavioural inhibition. Multiple PET imaging studies indicate that striatal dopaminergic abnormalities contribute to hyperdopaminergic functioning in PD patients with ICD (PDICD+) and to the dysregulation of the limbic fronto-striatal networks which are critical for reward-related decision impulsivity. However, the serotonergic system is central to response inhibition and plays a critical role in neuropsychiatric symptoms in PD, but its role remains undetermined in PDICD. We hypothesized that PDICD+ patients exhibit serotonergic dysfunction within the cortico-striato-pallido-thalamic circuits involved in the inhibitory control of behaviour and decided to investigate the pre- and post-synaptic serotonergic innervation using two highly-specific PET tracers for the serotonin transporter (SERT) using [11C]DASB and the 5-HT2A receptor using [18F]altanserin. In this prospective, case-control, double-tracer PET study, we recruited 15 PDICD+ patients, 15 PDICD- patients and 15 healthy controls, matched for age and sex, and compared the availability of [11C]DASB and [18F]altanserin using permutation-based analysis. PDICD+ patients had one (n=9) or multiple ICDs (n=6), consisting in hypersexuality (n=8), compulsive eating (n=6), compulsive shopping (n=5) and pathological gambling (n=4) and were characterized by greater choice impulsivity (impaired delay discounting for monetary rewards) and greater urgency with more severe depressive and anxious symptoms. We demonstrate that PDICD+ patients had greater [11C]DASB binding in the posterior putamen and pallidum in comparison to PDICD- patients, corresponding to relatively preserved presynaptic SERT availability within the subcortical sensorimotor network involved in response inhibition. In addition, cortical [18F]altanserin binding was greater in PDICD+ patients in the bilateral supplementary motor area, precentral gyrus and right dorsolateral prefrontal cortex, involving the sensorimotor and associative networks which regulate behavioural inhibition. Furthermore, we show that pre- and post-synaptic serotonergic dysfunction subserving action versus decision impulsivity in PD patients specifically followed the distinctive functional organization of the sensorimotor and associative fronto-striatal networks. Altogether, we demonstrate that serotonergic dysfunction related to ICDs in PD specifically involve the sensorimotor and associative cortico-striato-pallido-thalamic circuits involved in inhibitory control. Thus, serotonergic dysfunction contributes to the mechanisms related to the vulnerability and development of ICDs in PD patients, beyond the known dopaminergic abnormalities in the limbic fronto-striatal circuit.

Amphetamine in Adolescence Induces a Sex-Specific Mesolimbic Dopamine Phenotype in the Adult Prefrontal Cortex

Drugs of abuse in adolescence impact brain maturation and increase psychiatric risk, with differences in sensitivity between males and females. Amphetamine in adolescent male, but not female mice, causes dopamine axons intended to innervate the nucleus accumbens and to grow ectopically to the prefrontal cortex (PFC). This is mediated by drug-induced downregulation of the Netrin-1 receptor DCC. How off-target dopamine axons function in the adult PFC remains to be determined. Here we report that males and females show place preference for amphetamine in adolescence. However, only in males, amphetamine increases PFC dopamine transporter expression in adulthood: leading to aberrant baseline dopamine transients, faster dopamine release, and exaggerated responses to acute methylphenidate. Upregulation of DCC in adolescence, using CRISPRa, prevents all these changes. Mesolimbic dopamine axons rerouted to the PFC in adolescence retain anatomical and functional phenotypes of their intended target, rendering males enduringly vulnerable to the harmful effects of drugs of abuse.

The three clap test: a window into cognitive and frontal lobe dysfunction

The three clap test (TCT) is a simple bedside test that can elicit the so-called applause sign (AS), manifesting with more than three claps after the examiner's instruction to clap three times. Although the AS was originally described as a useful sign differentiating patients with progressive supranuclear palsy (PSP) from patients with Parkinson's disease (PD) and frontotemporal dementia (FTD), it is also known to be present in PD, Alzheimer's disease and several other diseases. It reflects the so-called stopping impulsivity and cognitive and frontal lobe dysfunction. In addition to the AS, the TCT can also elicit the non-applause sign, linked with the apathy subtype of behavioural variant of FTD and the jumping the gun sign, a sign of waiting impulsivity, also seen in PSP. This review summarizes the up-to-date clinical aspects and pathophysiology of all these signs and discuss the benefit of using the TCT in the routine clinical praxis.

Cocaine Self-Administration Increases Impulsive Decision-Making in Low-Impulsive Rats Associated with Impaired Functional Connectivity in the Mesocorticolimbic System

Impulsivity is often considered a risk factor for drug addiction; however, not all evidence supports this view. In the present study, we used a food reward delay-discounting task (DDT) to categorize rats as low-, middle-, and high-impulsive but failed to find any difference among these groups in the acquisition and maintenance of cocaine self-administration (SA), regardless of electrical footshock punishment. Additionally, there were no group differences in locomotor responses to acute cocaine in rats with or without a history of cocaine SA. Unexpectedly, chronic cocaine SA selectively increased impulsive choice in low-impulsive rats. Resting-state fMRI analysis revealed a positive correlation between impulsivity and cerebral blood volume in the midbrain, thalamus, and auditory cortex. Using these three regions as seeds, we observed a negative correlation between impulsivity and functional connectivity between the midbrain and frontal cortex, as well as between the thalamus and frontal cortex (including the orbitofrontal, primary, and parietal cortices) in low-impulsive rats. These correlations were attenuated following chronic cocaine SA. RNAscope in situ hybridization assays revealed a significant reduction in dopamine (DA) D1, D2, and D3 receptor mRNA expression in the corticostriatal regions of low-impulsive rats after cocaine SA. Our findings challenge the widely held view that impulsivity is a vulnerability factor for cocaine use disorder. Instead, chronic cocaine use appears to selectively increase impulsive choice decision-making in normally low-impulsive rats, associated with reduced functional connectivity and DA receptor expression in the mesocorticolimbic DA network.

Factor Structure and Psychometric Properties of the Learning, Executive, and Attention Functioning (LEAF) Scale in Young Adults

The Learning, Executive, and Attention Functioning (LEAF) scale is a resource-friendly means of assessing executive functions (EFs) and related constructs (e.g., academic abilities) in children and adolescents that has been adapted for use with adults. However, no study in any population has investigated the factor structure of all LEAF EF items to determine whether items factor in a manner consistent with the originally proposed scale structure. Therefore, we examined LEAF scale responses of 546 young adults (Mage = 20.05, SD = 2.17). Upon removing academic items following a preliminary factor analysis, we performed principal axis factoring on the remaining 39 EF items. The final model accounted for 61.75% of the total variance in LEAF EF items and suggested that these items assess six moderately correlated EF constructs in young adults. We constructed six updated subscales to help researchers measure these EFs in young adults using the LEAF scale, each of which uniquely and differentially predicted measures of self-reported impulsivity, academic difficulties, and learning-related disorder history. Overall, the LEAF promises to be an accessible means of assessing a range of EF constructs in young adults, particularly when updated subscale structures based on factor analysis are used.

Mechanisms of Proactive Adaptation in a Rewarded Response Inhibition Task: Executive, Motor, or Attentional Effects?

A growing number of studies have demonstrated the effects of reward motivation on inhibitory control performance. However, the exact neurocognitive mechanisms supporting these effects are not fully elucidated. In this preregistered study, we test the hypothesis that changes in speed-accuracy trade-off across contexts that alternatively incentivize fast responses versus accurate inhibition rely on a modulation of proactive inhibitory control, a mechanism intended to lock movement initiation in anticipation of stimulus presentation. Thirty healthy participants performed a modified Go/NoGo task in which the motivation to prioritize Go vs. NoGo successes was manipulated using monetary rewards of different magnitudes. High-density EEG was recorded throughout the task. Source-space analyses were performed to track brain oscillatory activities consistent with proactive inhibitory control. We observed that participants adapted their behavior to the motivational context but found no evidence that this adaptation relied on a modulation of proactive inhibitory control, hence failing to provide support for our pre-registered hypothesis. Unplanned analyses of brain-behavior relationships suggested an association between faster reaction times and enhanced top-down attention to the stimuli associated with larger rewards, as well as between increased commission error rates and stronger motor activations when Go stimuli were associated with larger rewards. The latter was related to inter-individual differences in trait reward responsiveness. These results highlight the need to carefully parse the different contributing mechanisms when studying the influence of reward motivation on inhibitory performance in impulsivity disorders. Exploratory results suggest alternative mechanisms that may be directly tested in further studies.

Monoamine alterations in Alzheimer's disease and their implications in comorbid neuropsychiatric symptoms

Alzheimer's disease (AD) is a devastating neurodegenerative disorder characterized by relentless cognitive decline and the emergence of profoundly disruptive neuropsychiatric symptoms. As the disease progresses, it unveils a formidable array of neuropsychiatric manifestations, including debilitating depression, anxiety, agitation, and distressing episodes of psychosis. The intricate web of the monoaminergic system, governed by serotonin, dopamine, and norepinephrine, significantly influences our mood, cognition, and behavior. Emerging evidence suggests that dysregulation and degeneration of this system occur early in AD, leading to notable alterations in these critical neurotransmitters' levels, metabolism, and receptor function. However, how the degeneration of monoaminergic neurons and subsequent compensatory changes contribute to the presentation of neuropsychiatric symptoms observed in Alzheimer's disease remains elusive. This review synthesizes current findings on monoamine alterations in AD and explores how these changes contribute to the neuropsychiatric symptomatology of the disease. By elucidating the biological underpinnings of AD-related psychiatric symptoms, we aim to underscore the complexity and inform innovative approaches for treating neuropsychiatric symptoms in AD.

Phase synchrony between prefrontal noradrenergic and cholinergic signals indexes inhibitory control

Inhibitory control is a critical executive function that allows animals to suppress their impulsive behavior in order to achieve certain goals or avoid punishment. We investigated norepinephrine (NE) and acetylcholine (ACh) dynamics and population neuronal activity in the prefrontal cortex (PFC) during inhibitory control. Using fluorescent sensors to measure extracellular levels of NE and ACh, we simultaneously recorded prefrontal NE and ACh dynamics in mice performing inhibitory control tasks. The prefrontal NE and ACh signals exhibited strong coherence at 0.4-0.8 Hz. Although inhibition of locus coeruleus (LC) neurons projecting to the PFC impaired inhibitory control, inhibiting LC neurons projecting to the basal forebrain (BF) caused a more profound impairment, despite an approximately 30% overlap between LC neurons projecting to the PFC and BF, as revealed by our tracing studies. The inhibition of LC neurons projecting to the BF did not diminish the difference in prefrontal NE/ACh signals between successful and failed trials; instead, it abolished the difference in NE-ACh phase synchrony between successful and failed trials, indicating that NE-ACh phase synchrony is a task-relevant neuromodulatory feature. Chemogenetic inhibition of cholinergic neurons that project to the LC region did not impair inhibitory control, nor did it abolish the difference in NE-ACh phase synchrony between successful or failed trials, further confirming the relevance of NE-ACh phase synchrony to inhibitory control. To understand the possible effect of NE-ACh synchrony on prefrontal population activity, we employed Neuropixels to record from the PFC during inhibitory control. The inhibition of LC neurons projecting to the BF not only reduced the number of prefrontal neurons encoding inhibitory control, but also disrupted population firing patterns representing inhibitory control, as revealed by a demixed principal component (dPCA) analysis. Taken together, these findings suggest that the LC modulates inhibitory control through its collective effect with cholinergic systems on population activity in the prefrontal cortex. Our results further indicate that NE-ACh phase synchrony is a critical neuromodulatory feature with important implications for cognitive control.

Maximising translational value of the Iowa gambling task in preclinical studies through the use of the rodent touchscreen

The Iowa gambling task is widely employed to assess the evaluation of risk versus reward contingencies, and how the evaluations are implemented to gain advantageous returns. The cognitive processes involved can be compromised in psychiatric conditions, leading to the development of analogous tasks with translational value for use in rodents. The rodent touchscreen apparatus maximises the degree of similarity with the human task, and in this review we provide an outline of the use of rodent touchscreen gambling tasks in preclinical studies of psychiatric conditions. In particular, we describe how the basic task has been adapted to probe the relative contributions of different neurotransmitter systems, and specific aspects of cognition. We then offer a perspective on how the task might be employed most beneficially in future studies.

Emotion dysregulation and impulsivity as overlapping symptoms in adult Attention-Deficit/Hyperactivity Disorder and Borderline Personality Disorder: severity profiles and associations with childhood traumatization and personality functioning

BACKGROUND

Increased levels of emotion dysregulation and impulsive behavior are overlapping symptoms in adult Attention-Deficit/Hyperactivity Disorder (aADHD) and Borderline Personality Disorder (BPD), both symptom domains reflecting on inhibitory control, although from different angles. Our aims were to describe their differences in the above conditions, investigate their associations with childhood traumatization, and to explore the potential mediation of emotion dysregulation and impulsivity between childhood traumas and personality functioning.

METHODS

Young adults between 18 and 36 years diagnosed with aADHD (n = 100) and BPD (n = 63) were investigated with structured clinical interviews, while age-matched healthy controls (n = 100) were screened for psychiatric disorders. Patients with aADHD-BPD comorbidity were excluded from further analyses. The Difficulties in Emotion Regulation Scale, the Barratt Impulsiveness Scale, the Level of Personality Functioning Scale, and the Childhood Trauma Questionnaire-Short Form were administered to investigate trait measures and childhood traumatization, respectively. Behavioral impulsivity and delay aversion were assessed using selected tests of the Cambridge Neuropsychological Test Automated Battery, and a computerized decision-making paradigm based on the Rogers decision-making task, respectively.

RESULTS

Significantly higher levels of emotion dysregulation and impulsivity were present both in the aADHD and BPD groups, however with different profiles. Waiting and stopping impulsivity was selectively higher among aADHD patients compared to healthy controls. The BPD group reported higher levels of emotion dysregulation in all domains, and demonstrated increased delay aversion among uncertain conditions in decision-making. Higher levels of childhood trauma were associated with emotion dysregulation, trait impulsivity, and delay aversion across groups. Emotion regulatory capacity played a significant mediating role between childhood traumatization and the level of personality functioning.

CONCLUSIONS

Inhibitory control profiles of the aADHD and BPD groups were divergent. Childhood traumatization was associated with lower levels of personality functioning in adulthood, independently of diagnosis, an effect mediated more by emotion dysregulation, rather than impulsivity. These findings have various clinical implications for the treatment of aADHD and BPD, including psychoeducation, pharmacological interventions, and psychotherapy targeting specific symptom domains.

Hierarchical Neurocognitive Model of Externalizing and Internalizing Comorbidity

Mounting evidence suggests hierarchical psychopathology factors underlying psychiatric comorbidity. However, the exact neurobiological characterizations of these multilevel factors remain elusive. In this study, leveraging the brain-behavior predictive framework with a 10-year longitudinal imaging-genetic cohort (IMAGEN, ages 14, 19 and 23, N = 1,750), we constructed two neural factors underlying externalizing and internalizing symptoms, which were reproducible across six clinical and population-based datasets (ABCD, STRATIFY/ESTRA, ABIDE II, ADHD-200 and XiNan, from age 10 to age 36, N = 3,765). These two neural factors exhibit distinct neural configurations: hyperconnectivity in impulsivity-related circuits for the externalizing symptoms and hypoconnectivity in goal-directed circuits for the internalizing symptoms. Both factors also differ in their cognitive-behavior relevance, genetic substrates and developmental profiles. Together with previous studies, these findings propose a hierarchical neurocognitive spectral model of comorbid mental illnesses from preadolescence to adulthood: a general neuropsychopathological (NP) factor (manifested as inefficient executive control) and two stratified factors for externalizing (deficient inhibition control) and internalizing (impaired goal-directed function) symptoms, respectively. These holistic insights are crucial for the development of stratified therapeutic interventions for mental disorders.

The Mechanisms Underlying the Intergenerational Transmission of Substance Use and Misuse: An Integrated Research Approach

Substance use and substance use disorders run in families. While it has long been recognized that the etiology of substance use behaviors and disorders involves a combination of genetic and environmental factors, two key questions remain largely unanswered: (1) the intergenerational transmission through which these genetic predispositions are passed from parents to children, and (2) the molecular mechanisms linking genetic variants to substance use behaviors and disorders. This article aims to provide a comprehensive conceptual framework and methodological approach for investigating the intergenerational transmission of substance use behaviors and disorders, by integrating genetic nurture analysis, gene expression imputation, and weighted gene co-expression network analysis. We also additionally describe two longitudinal cohorts - the Brisbane Longitudinal Twin Study in Australia and the Lifelines Cohort Study in the Netherlands. By applying the methodological framework to these two unique datasets, our future research will explore the complex interplay between genetic factors, gene expression, and environmental influences on substance use behaviors and disorders across different life stages and populations.

Deep Brain Stimulation of the Nucleus Accumbens for Severe Self-Injurious Behavior in Children: A Phase I Pilot Trial

BACKGROUND

Self-injurious behavior (SIB) consists of repetitive, nonaccidental movements that result in physical damage inflicted upon oneself, without suicidal intent. SIB is prevalent among children with autism spectrum disorder and can lead to permanent disability or death. Neuromodulation at a locus of neural circuitry implicated in SIB, the nucleus accumbens (NAc), may directly influence these behaviors.

METHODS

We completed a phase I, open-label clinical trial of deep brain stimulation (DBS) of the NAc in children with severe, treatment-refractory SIB (ClinicalTrials.gov identifier NCT03982888). Participants were monitored for 12 months following NAc-DBS to assess the primary outcomes of safety and feasibility. Secondary outcomes included serial assessments of SIB and SIB-associated behaviors, ambulatory actigraphy, and changes in brain glucose metabolism induced by DBS.

RESULTS

Six children (ages 7-14 years) underwent NAc-DBS without serious adverse events. One child was found to have a delayed asymptomatic intracranial hemorrhage adjacent to a DBS electrode that did not require intervention, and 3 children experienced transient worsening in irritability or SIB with titration of stimulation parameters. NAc-DBS resulted in significant reductions in SIB and SIB-associated behaviors across multiple standardized scales, concurrent with clinically meaningful improvements in quality of life. Ambulatory actigraphy showed reductions in high-amplitude limb movements and positron emission tomography revealed treatment-induced reductions in metabolic activity within the thalamus, striatum, and temporoinsular cortex.

CONCLUSIONS

This first-in-children phase 1 clinical trial demonstrates the safety and feasibility of NAc-DBS in children with severe, refractory SIB at high risk of physical injury and death and supports further investigations.

The point of no return in the Emotional Stop-Signal Task: A matter of affect or method?

An affective variant of the Stop-Signal task was used to study the interaction between emotion and response inhibition (RI) in healthy young participants. The task involved the covert presentation of emotional faces as go stimuli, as well as a manipulation of motivation and affect by inducing a negative mood through the assignment of unfair punishment. In the literature on emotion and RI, there are contrasting findings reflecting the variability in the method used to calculate the RI latency, namely the Stop-Signal Reaction Time (SSRT). In fact, previous studies found both facilitatory and detrimental effects of affective manipulations over RI. However, they did not use the most robust SSRT estimation approach, namely the integration, casting some doubts on the reliability of the inferences. For these reasons, the present research draws attention on how the effect of the emotional manipulation may be due to a biased SSRT estimation. Specifically, the focus of our study was on how the effect of emotion on the SSRT may vary according to different estimation procedures, the mean and two variants of the integration method. We predicted that the effect of the emotional manipulation in the SST would depend on the SSRT estimation method employed. Indeed, a significant effect of emotion was only found when SSRT was estimated with the mean method. We conclude that the mean method should be avoided in the study of emotion and RI because it overestimates SSRT. Rather, the integration approach should be used for future research in this field, while also factoring in information about the participants' strategy in emotional contexts that require greater effortful control and offer a challenge to self-regulation both in health and disease.

Choice and motor impulsivity in Veterans with mild traumatic brain injury with and without history of suicide attempt

Traumatic brain injury is associated with increased risk for suicide, but the underlying mechanisms remain poorly understood. One candidate mechanism is impulsivity, which includes both choice impulsivity (e.g., preference for smaller, immediate rewards) and motor impulsivity (inability to inhibit prepotent motor responding). We evaluated these facets of impulsivity in Veterans classified according to their history of mild TBI (mTBI) and/or prior suicide attempt. 99 Veterans were classified as having no mTBI or suicide attempt (control, n = 35), mTBI but no suicide attempt (mTBI, n = 42), or mTBI and prior attempt (mTBI+SA, n = 22). A computerized temporal discounting task (Monetary Choice Questionnaire) assessed choice impulsivity and a Go/No-go task assessed motor impulsivity. On temporal discounting, the control group showed less choice impulsivity than the mTBI group. Temporal discounting was not associated with suicide attempt history. However, among the mTBI+SA group, those with high-lethality suicide attempts showed less choice impulsivity than those with low-lethality attempts. No group differences emerged on the Go/No-go task. The findings are consistent with choice impulsivity as a potential pathway by which mTBI affects risk for suicide. The finding that high-lethality attempts were associated with greater willingness to wait for reward supports the emerging view of heterogeneous underlying pathways to suicide risk, with distinct phenotypes that implicate different therapeutic options.

Basal forebrain-lateral habenula inputs and control of impulsive behavior

Deficits in impulse control are observed in several neurocognitive disorders, including attention deficit hyperactivity (ADHD), substance use disorders (SUDs), and those following traumatic brain injury (TBI). Understanding brain circuits and mechanisms contributing to impulsive behavior may aid in identifying therapeutic interventions. We previously reported that intact lateral habenula (LHb) function is necessary to limit impulsivity defined by impaired response inhibition in rats. Here, we examine the involvement of a synaptic input to the LHb on response inhibition using cellular, circuit, and behavioral approaches. Retrograde fluorogold tracing identified basal forebrain (BF) inputs to LHb, primarily arising from ventral pallidum and nucleus accumbens shell (VP/NAcs). Glutamic acid decarboxylase and cannabinoid CB1 receptor (CB1R) mRNAs colocalized with fluorogold, suggesting a cannabinoid modulated GABAergic pathway. Optogenetic activation of these axons strongly inhibited LHb neuron action potentials and GABA release was tonically suppressed by an endogenous cannabinoid in vitro. Behavioral experiments showed that response inhibition during signaled reward omission was impaired when VP/NAcs inputs to LHb were optogenetically stimulated, whereas inhibition of this pathway did not alter LHb control of impulsivity. Systemic injection with the psychotropic phytocannabinoid, Δ9-tetrahydrocannabinol (Δ9-THC), also increased impulsivity in male, and not female rats, and this was blocked by LHb CB1R antagonism. However, as optogenetic VP/NAcs pathway inhibition did not alter impulse control, we conclude that the pro-impulsive effects of Δ9-THC likely do not occur via inhibition of this afferent. These results identify an inhibitory LHb afferent that is controlled by CB1Rs that can regulate impulsive behavior.

Neurolipidomics in schizophrenia: A not so well-oiled machine

Most patients with schizophrenia (SCZ) do not exhibit violent behaviors and are more likely to be victims rather than perpetrators of violent acts. However, a subgroup of forensic detainees with SCZ exhibit tendencies to engage in criminal violations. Although numerous models have been proposed, ranging from substance use, serotonin transporter gene, and cognitive dysfunction, the molecular underpinnings of violence in SCZ patients remains elusive. Lithium and clozapine have established anti-aggression properties and recent studies have linked low cholesterol levels and ultraviolet (UV) radiation with human aggression, while vitamin D3 reduces violent behaviors. A recent study found that vitamin D3, omega-3 fatty acids, magnesium, and zinc lower aggression in forensic population. In this review article, we take a closer look at aryl hydrocarbon receptor (AhR) and the dysfunctional lipidome in neuronal membranes, with emphasis on cholesterol and vitamin D3 depletion, as sources of aggressive behavior. We also discuss modalities to increase the fluidity of neuronal double layer via membrane lipid replacement (MLR) and natural or synthetic compounds. This article is part of the Special Issue on "Personality Disorders".

White matter correlates of impulsive behavior in healthy individuals: A diffusion magnetic resonance imaging study

Aim

To explore white matter (WM) tracts linked to impulsivity using the diffusion magnetic resonance imaging (DMRI) connectometry method.

Methods

We analyzed 218 healthy participants from the Leipzig Study for Mind-Body-Emotion Interactions database. Impulsivity correlations with DMRI-derived WM changes were assessed using Urgency-Premeditation-Perseverance-Sensation (UPPS) Impulsive Behavior Scale subscales: lack of perseverance (PE), lack of premeditation (PM), sensation seeking (SS), and negative urgency. DMRI data were processed using connectometry, adjusting for sex and age, to examine WM tract integrity via quantitative anisotropy (QA). Also, two additional interaction analyses were conducted to separately examine the interaction effect between WM QA, and sex and age in predicting impulsive behavior scores. The significance level in our statistical analyses was set at a false discovery rate (FDR) below 0.05.

Results

QA in the bilateral cerebellum and middle cerebellar peduncle showed a negative association with PE and PM severity (FDR = 0.0004). QA in the middle cerebellar peduncle, corpus callosum body, and forceps major demonstrated a positive association with SS (FDR = 0.0001). Conversely, QA in forceps minor had a positive association with PM (FDR = 0.004), and QA in forceps minor and bilateral cingulum showed a positive association with SS (FDR = 0.0005). Age and sex had no significant effects on the association between WM QA and UPPS subscale scores.

Conclusion

Impulsivity is linked to distinct WM integrity changes in various tracts, including the corpus callosum, cerebellum, and cingulum, offering insights into the pathophysiology of impulsivity and guiding future research.

Variable Presence of an Evolutionarily New Brain Structure Is Related to Trait Impulsivity

BACKGROUND

Impulsivity is a multidimensional construct reflecting poor constraint over one's behaviors. Clinical psychology research has identified separable impulsivity dimensions that are each unique transdiagnostic indicators for psychopathology. However, despite this apparent clinical importance, the shared and unique neuroanatomical correlates of these factors remain largely unknown. Concomitantly, neuroimaging research has identified variably present human brain structures implicated in cognition and disorder: the folds (sulci) of the cerebral cortex located in the latest-developing and most evolutionarily expanded hominoid-specific association cortices.

METHODS

We tethered these 2 fields to test whether variability in one such structure in the anterior cingulate cortex (ACC)-the paracingulate sulcus (PCGS)-was related to individual differences in trait impulsivity. A total of 120 adult participants with internalizing or externalizing psychopathology completed a magnetic resonance imaging scan and the Three-Factor Impulsivity Index. Using precision imaging techniques, we manually identified the PCGS, when present, and acquired quantitative folding metrics (PCGS length and ACC local gyrification index).

RESULTS

Neuroanatomical-behavioral analyses revealed that participants with leftward or symmetrical PCGS patterns had greater severity of Lack of Follow Through (LFT)-which captures inattention and lack of perseverance-than those with rightward asymmetry. Neuroanatomical-functional analyses identified that the PCGS colocalized with a focal locus found in a neuroimaging meta-analysis on a feature underlying LFT. Neither quantitative folding metric related to any impulsivity dimension.

CONCLUSIONS

This study advances understanding of the neuroanatomical correlates of impulsivity and establishes the notion that the topographical organization of distinct, hominoid-specific cortical expanses underlies separable impulsivity dimensions with robust, transdiagnostic implications for psychopathology.

Impulsivity in ADHD and Borderline Personality Disorder: A Systematic Review of Gray and White Matter Variations

Introduction: Impulsivity is one of the overlapping symptoms common to borderline personality disorder (BPD) and attention deficit hyperactivity disorder (ADHD), but the neurobiological basis of these disorders remains uncertain. This systematic review aims to identify abnormalities in the gray and white matter associated with impulsivity in BPD and ADHD. Methods: We conducted a systematic search of the PubMed, Embase, and SCOPUS databases, adhering to PRISMA guidelines. Studies that investigated gray and white matter alterations in BPD or ADHD populations and their relationship with impulsivity were included. We reviewed information from 23 studies involving 992 participants, which included findings from structural MRI and DTI. Results: The review identified various nonhomogeneous changes associated with impulsivity in BPD and ADHD. BPD was mainly associated with abnormalities in the prefrontal cortex (PFC) and limbic areas, which correlated negatively with impulsivity. In contrast, impulsivity associated with ADHD was associated with structural changes in the caudate nucleus and frontal-striatal pathways. Despite the overlapping symptoms of impulsivity, the neurobiological mechanisms appeared to differ between the two disorders. Conclusions: These findings emphasize the distinct neurostructural correlates of impulsivity in BPD and ADHD. While both disorders show impulsivity as one of their main symptoms, the fundamental brain structures associated with this trait are different. BPD is primarily associated with abnormalities in the prefrontal cortex and limbic system, whereas the alterations seen in ADHD tend to focus on the caudate nucleus and frontostriatal pathways. Further research is needed to clarify these differences and their implications for treatment.

Subthalamic control of impulsive actions: insights from deep brain stimulation in Parkinson's disease

Control of actions allows adaptive, goal-directed behaviour. The basal ganglia, including the subthalamic nucleus, are thought to play a central role in dynamically controlling actions through recurrent negative feedback loops with the cerebral cortex. Here, we summarize recent translational studies that used deep brain stimulation to record neural activity from and apply electrical stimulation to the subthalamic nucleus in people with Parkinson's disease. These studies have elucidated spatial, spectral and temporal features of the neural mechanisms underlying the controlled delay of actions in cortico-subthalamic networks and demonstrated their causal effects on behaviour in distinct processing windows. While these mechanisms have been conceptualized as control signals for suppressing impulsive response tendencies in conflict tasks and as decision threshold adjustments in value-based and perceptual decisions, we propose a common framework linking decision-making, cognition and movement. Within this framework, subthalamic deep brain stimulation can lead to suboptimal choices by reducing the time that patients take for deliberation before committing to an action. However, clinical studies have consistently shown that the occurrence of impulse control disorders is reduced, not increased, after subthalamic deep brain stimulation surgery. This apparent contradiction can be reconciled when recognizing the multifaceted nature of impulsivity, its underlying mechanisms and modulation by treatment. While subthalamic deep brain stimulation renders patients susceptible to making decisions without proper forethought, this can be disentangled from effects related to dopamine comprising sensitivity to benefits versus costs, reward delay aversion and learning from outcomes. Alterations in these dopamine-mediated mechanisms are thought to underlie the development of impulse control disorders and can be relatively spared with reduced dopaminergic medication after subthalamic deep brain stimulation. Together, results from studies using deep brain stimulation as an experimental tool have improved our understanding of action control in the human brain and have important implications for treatment of patients with neurological disorders.

Associations between intraindividual reaction time variability, baseline respiratory sinus arrhythmia, and trait impulsivity in males with substance use disorders

Trait impulsivity, characterized by the tendency to act without adequate consideration of potential consequences in pursuit of immediate rewards, is a recognized vulnerability marker for substance use disorders (SUDs). Cognitive control deficits are implicated in the manifestation of high trait impulsivity, and intraindividual reaction time variability (IIRTV), an indicator of cognitive control, may influence trait impulsivity. Baseline respiratory sinus arrhythmia (RSA) reflects vagal tone, serves as an index of physiological self-regulation, which has been demonstrated to be related to trait impulsivity. However, it is unclear whether IIRTV is associated with trait impulsivity and whether it interacts with baseline RSA to influence trait impulsivity. A total of 113 males with SUDs participated (Mage = 46.04 years, SD = 11.53) in this study. Trait impulsivity was assessed using a self-report questionnaire, IIRTV was measured through a two-choice oddball task, and baseline RSA was obtained through the collection of electrocardiogram (ECG) data. The results indicated that IIRTV interacted with baseline RSA to influence trait impulsivity. These findings suggested that cognitive control indexed by IIRTV, might represent a central nervous correlate of trait impulsivity, and that it interacted with vagal tone indexed by baseline RSA, to influence trait impulsivity.

Associative memory in alcohol-related contexts: An fMRI study with young binge drinkers

BACKGROUND

Alcohol-related cues are known to influence craving levels, a hallmark of alcohol misuse. Binge drinking (BD), a pattern of heavy alcohol use, has been associated with cognitive and neurofunctional alterations, including alcohol attentional bias, memory impairments, as well as disrupted activity in prefrontal- and reward-related regions. However, literature is yet to explore how memories associated with alcohol-related cues are processed by BDs, and how the recall of this information may influence their reward processing.

AIMS

The present functional magnetic resonance imaging (fMRI) study aimed to investigate the neurofunctional signatures of BD during an associative memory task.

METHOD

In all, 36 university students, 20 BDs and 16 alcohol abstainers, were asked to memorize neutral objects paired with either alcohol or non-alcohol-related contexts. Subsequently, neutral stimuli were presented, and participants were asked to classify them as being previously paired with alcohol- or non-alcohol-related contexts.

RESULTS

While behavioral performance was similar in both groups, during the recall of alcohol-related cues, BDs showed increased brain activation in two clusters including the thalamus, globus pallidus and dorsal striatum, and cerebellum and occipital fusiform gyrus, respectively.

CONCLUSION

These findings suggest that BDs display augmented brain activity in areas responsible for mental imagery and reward processing when trying to recall alcohol-related cues, which might ultimately contribute to alcohol craving, even without being directly exposed to an alcohol-related context. These results highlight the importance of considering how alcohol-related contexts may influence alcohol-seeking behavior and, consequently, the maintenance or increase in alcohol use.

Neurophysiological activity following gains and losses among young adults with non-suicidal self-injury: An ERP study

OBJECTIVE

Non-suicidal self-injury (NSSI) is an increasingly concerning issue that is linked to a range of mental health problems. However, little is known about the potential neurophysiological mechanisms underlying risk decision-making in Major depressive disorder (MDD) patients with NSSI-the present study aimed to fill this important literature gap.

METHODS

A total of 81 MDD patients (with NSSI: n = 40, without NSSI: n = 41) and 44 matched healthy controls (HC) underwent a modified version of the Iowa Gambling Task (IGT) while an electroencephalogram was recorded. Feedback-related negativity (FRN) and P300 were examined during the feedback stage of the risky decision-making process.

RESULTS

Behavioural findings revealed that individuals diagnosed with MDD displayed a greater tendency to make risky decisions compared to the control group. Furthermore, MDD patients with NSSI demonstrated a significantly more negative ΔFN (i.e., the difference in neural response to losses compared to gains) than those without NSSI. Further, NSSI patients showed a larger difference ΔFN (loss minus gain), which was associated with enhanced impulsivity.

CONCLUSIONS

Collectively, the findings suggest that there is an altered processing of risky decision-making in the electrophysiology of patients with MDD who engage in NSSI. The ΔFN may serve as a psychophysiological marker indicating risk for NSSI.

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.

Clinical management model for impulse control disorders in Parkinson's disease

Over the last decade, we have gained a better understanding of impulse control disorder in Parkinson's disease (PD-ICD), a medication complication in PD. Researchers were aware of its complexity and took efforts to learn more about its diagnostic and treatment possibilities. Nevertheless, clinical management for it is currently neglected. We conducted a narrative overview of literature published from 2012 to October 2023 on various aspects of clinical management for PD-ICD. A potential "susceptibility-catalytic-stress" model in the development of PD-ICD was proposed and a profile encoding predictors for PD-ICD was created. Based on these predictors, some methods for prediction were recently developed for better prediction, such as the polymorphic dopamine genetic risk score and the clinic-genetic ICD-risk score. A variety of treatment options, including dose reduction of dopamine receptor agonists (DAs), DAs removal, DAs switch, and add-on therapy, are investigated with inconsistent reports. Based on current findings, we developed a clinical management model prototype centered on prevention, consisting of prediction, prevention, follow-up and monitoring, therapy, and recurrence prevention, for clinical reference, and further proposed 4 key clinical management principles, including standardization, prediction centered, persistence, and whole course.

Variable Presence of an Evolutionarily New Brain Structure is Related to Trait Impulsivity

Background

Impulsivity is a multidimensional construct reflecting poor constraint over one's behaviors. Clinical psychology research identifies separable impulsivity dimensions that are each unique transdiagnostic indicators for psychopathology. Yet, despite this apparent clinical importance, the shared and unique neuroanatomical correlates of these factors remain largely unknown. Concomitantly, neuroimaging research identifies variably present human brain structures implicated in cognition and disorder: the folds (sulci) of the cerebral cortex located in the latest developing and most evolutionarily expanded hominoid-specific association cortices.

Methods

We tethered these two fields to test whether variability in one such structure in anterior cingulate cortex (ACC)-the paracingulate sulcus (PCGS)-was related to individual differences in trait impulsivity. 120 adult participants with internalizing or externalizing psychopathology completed a magnetic resonance imaging scan and the Three-Factor Impulsivity Index. Using precision imaging techniques, we manually identified the PCGS, when present, and acquired quantitative folding metrics (PCGS length and ACC local gyrification index).

Results

Neuroanatomical-behavioral analyses revealed that participants with leftward or symmetrical PCGS patterns had greater severity of Lack of Follow Through (LFT)-which captures inattention and lack of perseverance-than those with rightward asymmetry. Neuroanatomical-functional analyses identified that the PCGS co-localized with a focal locus found in a neuroimaging meta-analysis on a feature underlying LFT. Both quantitative folding metrics did not relate to any impulsivity dimension.

Conclusions

This study advances understanding of the neuroanatomical correlates of impulsivity and establishes the notion that the topographical organization of distinct, hominoid-specific cortical expanses underlie separable impulsivity dimensions with robust, transdiagnostic implications for psychopathology.

Functional Brain Network of Trait Impulsivity: Whole-Brain Functional Connectivity Predicts Self-Reported Impulsivity

Given impulsivity's multidimensional nature and its implications across various aspects of human behavior, a comprehensive understanding of functional brain circuits associated with this trait is warranted. In the current study, we utilized whole-brain resting-state functional connectivity data of healthy males (n = 156) to identify a network of connections predictive of an individual's impulsivity, as assessed by the Barratt Impulsiveness Scale (BIS)-11. Our participants were selected, in part, based on their self-reported BIS-11 impulsivity scores. Specifically, individuals who reported high or low trait impulsivity scores during screening were selected first, followed by those with intermediate impulsivity levels. This enabled us to include participants with rare, extreme scores and to cover the entire BIS-11 impulsivity spectrum. We employed repeated K-fold cross-validation for feature-selection and used stratified 10-fold cross-validation to train and test our models. Our findings revealed a widespread neural network associated with trait impulsivity and a notable correlation between predicted and observed scores. Feature importance and node degree were assessed to highlight specific nodes and edges within the impulsivity network, revealing previously overlooked key brain regions, such as the cerebellum, brainstem, and temporal lobe, while supporting previous findings on the basal ganglia-thalamo-prefrontal network and the prefrontal-motor strip network in relation to impulsiveness. This deepened understanding establishes a foundation for identifying alterations in functional brain networks associated with dysfunctional impulsivity.

RNA m6A methyltransferase activator affects anxiety-related behaviours, monoamines and striatal gene expression in the rat

Modification of mRNA by methylation is involved in post-transcriptional regulation of gene expression by affecting the splicing, transport, stability and translation of mRNA. Methylation of adenosine at N6 (m6A) is one of the most common and important cellular modification occurring in the mRNA of eukaryotes. Evidence that m6A mRNA methylation is involved in regulation of stress response and that its dysregulation may contribute to the pathogenesis of neuropsychiatric disorders is accumulating. We have examined the acute and subchronic (up to 18 days once per day intraperitoneally) effect of the first METTL3/METTL14 activator compound CHMA1004 (methyl-piperazine-2-carboxylate) at two doses (1 and 5 mg/kg) in male and female rats. CHMA1004 had a locomotor activating and anxiolytic-like profile in open field and elevated zero-maze tests. In female rats sucrose consumption and swimming in Porsolt's test were increased. Nevertheless, CHMA1004 did not exhibit strong psychostimulant-like properties: CHMA1004 had no effect on 50-kHz ultrasonic vocalizations except that it reduced the baseline difference between male and female animals, and acute drug treatment had no effect on extracellular dopamine levels in striatum. Subchronic CHMA1004 altered ex vivo catecholamine levels in several brain regions. RNA sequencing of female rat striata after subchronic CHMA1004 treatment revealed changes in the expression of a number of genes linked to dopamine neuron viability, neurodegeneration, depression, anxiety and stress response. Conclusively, the first-in-class METTL3/METTL14 activator compound CHMA1004 increased locomotor activity and elicited anxiolytic-like effects after systemic administration, demonstrating that pharmacological activation of RNA m6A methylation has potential for neuropsychiatric drug development.

Involvement of dopamine D3 receptor in impulsive choice decision-making in male rats

Impulsive decision-making has been linked to impulse control disorders and substance use disorders. However, the neural mechanisms underlying impulsive choice are not fully understood. While previous PET imaging and autoradiography studies have shown involvement of dopamine and D2/3 receptors in impulsive behavior, the roles of distinct D1, D2, and D3 receptors in impulsive decision-making remain unclear. In this study, we used a food reward delay-discounting task (DDT) to identify low- and high-impulsive rats, in which low-impulsive rats exhibited preference for large delayed reward over small immediate rewards, while high-impulsive rats showed the opposite preference. We then examined D1, D2, and D3 receptor gene expression using RNAscope in situ hybridization assays. We found that high-impulsive male rats exhibited lower levels of D2 and D3, and particularly D3, receptor expression in the nucleus accumbens (NAc), with no significant changes in the insular, prelimbic, and infralimbic cortices. Based on these findings, we further explored the role of the D3 receptor in impulsive decision-making. Systemic administration of a selective D3 receptor agonist (FOB02-04) significantly reduced impulsive choices in high-impulsive rats but had no effects in low-impulsive rats. Conversely, a selective D3 receptor antagonist (VK4-116) produced increased both impulsive and omission choices in both groups of rats. These findings suggest that impulsive decision-making is associated with a reduction in D3 receptor expression in the NAc. Selective D3 receptor agonists, but not antagonists, may hold therapeutic potentials for mitigating impulsivity in high-impulsive subjects.

Validation of the German long and short versions of the UPPS-P Impulsive Behavior Scale

OBJECTIVE

The UPPS-P Impulsive Behavior Scale is a widely used self-report measure of impulsivity, but there is currently no validated German version that includes the Positive Urgency scale.

METHODS

We combined existing German translations of UPPS scales and included the Positive Urgency dimension to validate the UPPS-P in a sample of 399 participants. In addition, we developed a revised short version of the UPPS-P (SUPPS-P) with 20 items and conducted a confirmatory factor analysis (CFA) to verify the structure in an independent validation sample with 349 participants. To determine evidence of convergent and discriminant validity, we used measures of impulsivity, depression, anxiety, stress, problematic alcohol and substance use.

RESULTS

CFA of the five factorial structure of the UPPS-P demonstrated acceptable fits and evidence of validity and reliability for the subscales. Psychometric characteristics of the SUPPS-P using the original item configuration were not satisfactory. As a result, we developed a revised German version of the SUPPS-P and confirmed the five-factor structure using a CFA in the validation sample. For the revised version, model fits and evidence of validity and internal consistencies were good. Associations with other constructs were as expected. For example, whereas Sensation Seeking was associated moderately with problematic alcohol use, lacking associations of Lack of Premeditation to internalizing symptoms showed evidence of discriminant validity.

DISCUSSION

The German translations of both UPPS-P and SUPPS-P are valid tools for measuring impulsive behaviors. They are well-suited for exploring the associations between different facets of impulsivity and psychopathological phenomena.

Trait reward sensitivity modulates connectivity with the temporoparietal junction and Anterior Insula during strategic decision making

Many decisions happen in social contexts such as negotiations, yet little is understood about how people balance fairness versus selfishness. Past investigations found that activation in brain areas involved in executive function and reward processing was associated with people offering less with no threat of rejection from their partner, compared to offering more when there was a threat of rejection. However, it remains unclear how trait reward sensitivity may modulate activation and connectivity patterns in these situations. To address this gap, we used task-based fMRI to examine the relation between reward sensitivity and the neural correlates of bargaining choices. Participants (N = 54) completed the Sensitivity to Punishment (SP)/Sensitivity to Reward (SR) Questionnaire and the Behavioral Inhibition System/Behavioral Activation System scales. Participants performed the Ultimatum and Dictator Games as proposers and exhibited strategic decisions by being fair when there was a threat of rejection, but being selfish when there was not a threat of rejection. We found that strategic decisions evoked activation in the Inferior Frontal Gyrus (IFG) and the Anterior Insula (AI). Next, we found elevated IFG connectivity with the Temporoparietal junction (TPJ) during strategic decisions. Finally, we explored whether trait reward sensitivity modulated brain responses while making strategic decisions. We found that people who scored lower in reward sensitivity made less strategic choices when they exhibited higher AI-Angular Gyrus connectivity. Taken together, our results demonstrate how trait reward sensitivity modulates neural responses to strategic decisions, potentially underscoring the importance of this factor within social and decision neuroscience.

Apathy and Impulsivity Co-Occur in Huntington's Disease

BACKGROUND

Apathy is a debilitating behavioral change in Huntington's disease (HD), but impulsivity in HD has not been well documented, and the co-occurrence of these behaviors in HD has not been investigated.

OBJECTIVE

Our objective was to determine whether apathy and impulsivity co-occur in people with HD and their associations with quality of life.

METHODS

Carriers of Huntington's gene expansion (premanifest to mild motor manifest disease; n = 42) along with healthy controls (n = 20) completed measures of apathy (Apathy Evaluation Scale and Apathy Motivation Index) and impulsivity (Barratt Impulsiveness Scale-11 and UPPS-P impulsivity scale), along with mood, cognition, clinical, and quality of life measures. Apathy and impulsivity measures were each reduced to a single metric per patient using principal component analysis. Correlations and multiple linear regression models determined associations between apathy and impulsivity and the potential influence of other covariates.

RESULTS

Apathy and impulsivity were significantly correlated (r = 0.6, p < 0.001, 95% CI [0.36, 0.76]) in HD, with this association remaining after controlling for depressive symptoms, motor disease severity, and cognitive function. Furthermore, apathy and depressive symptoms were associated with poorer quality of life.

CONCLUSIONS

Apathy and impulsivity co-occur in individuals with premanifest to mild manifest HD and have a significant impact on wellbeing. We add to a growing evidence body that apathy and impulsivity may be intrinsically linked.

HPA activity mediates the link between trait impulsivity and boredom

Boredom, a complex emotional state with implications for mental health and well-being, has garnered attention across disciplines, yet remains relatively understudied in psychiatric research. Here, we explored the intricate relationship between trait-impulsivity, stress, and boredom across two studies. Participants completed self-report measures of trait-impulsivity and boredom and boredom-inducing tasks. Study 1, involving 80 participants (42 women and 38 men, aged 20-63), replicates previous findings, by demonstrating that impulsive individuals report greater boredom following a boring task. Study 2 then extends this, using 20 participants (9 women and 12 men, aged 18-24), to show that hypothalamic-pituitary-adrenal (HPA) axis activity, specifically heightened salivary cortisol responses, mediate the link between impulsivity and boredom following a boring task. Collectively, these results demonstrate that HPA axis activity may underline the relationship between trait-impulsivity and boredom by extending previous work and offering a novel insight into potential mechanisms. These findings offer promise for personalised interventions, designed for high impulsivity individuals, to alleviate the negative impacts of boredom and potentially break the identified feedback loop.

Dissociable Roles of the mPFC-to-VTA Pathway in the Control of Impulsive Action and Risk-Related Decision-Making in Roman High- and Low-Avoidance Rats

BACKGROUND

Impulsive action and risk-related decision-making (RDM) are associated with various psychiatric disorders, including drug abuse. Both behavioral traits have also been linked to reduced frontocortical activity and alterations in dopamine function in the ventral tegmental area (VTA). However, despite direct projections from the medial prefrontal cortex (mPFC) to the VTA, the specific role of the mPFC-to-VTA pathway in controlling impulsive action and RDM remains unexplored.

METHODS

We used positron emission tomography with [18F]-fluorodeoxyglucose to evaluate brain metabolic activity in Roman high- (RHA) and low-avoidance (RLA) rats, which exhibit innate differences in impulsive action and RDM. Notably, we used a viral-based double dissociation chemogenetic strategy to isolate, for the first time to our knowledge, the role of the mPFC-to-VTA pathway in controlling these behaviors. We selectively activated the mPFC-to-VTA pathway in RHA rats and inhibited it in RLA rats, assessing the effects on impulsive action and RDM in the rat gambling task.

RESULTS

Our results showed that RHA rats displayed higher impulsive action, less optimal decision-making, and lower cortical activity than RLA rats at baseline. Chemogenetic activation of the mPFC-to-VTA pathway reduced impulsive action in RHA rats, whereas chemogenetic inhibition had the opposite effect in RLA rats. However, these manipulations did not affect RDM. Thus, by specifically targeting the mPFC-to-VTA pathway in a phenotype-dependent way, we reverted innate patterns of impulsive action but not RDM.

CONCLUSION

Our findings suggest a dissociable role of the mPFC-to-VTA pathway in impulsive action and RDM, highlighting its potential as a target for investigating impulsivity-related disorders.

Value Modulation of Self-Defeating Impulsivity

BACKGROUND

Impulse control is a critical aspect of cognitive functioning. Intuitively, whether an action is executed prematurely depends on its associated reward, yet the link between value and impulsivity remains poorly understood. Three frameworks for impulsivity offer contrasting views: impulsive behavior may be valuable because it is associated with hidden internal reward (e.g., reduction of mental effort). Alternatively, it can emerge from exploration, which is disadvantageous in the short term but can yield long-term benefits. Finally, impulsivity may reflect Pavlovian bias, an inherent tendency that occurs even when its outcome is negative.

METHODS

To test these hypotheses, we trained 17 male mice to withhold licking while anticipating variable rewards. We then measured and optogenetically manipulated dopamine release in the ventral striatum.

RESULTS

We found that higher reward magnitudes correlated with increased impulsivity. This behavior was well explained by a Pavlovian bias model. Furthermore, we observed negative dopamine signals during premature licking, suggesting that in this task, impulsivity is not merely an unsuccessful attempt at obtaining a reward. Rather, it is a failure to overcome the urge to act prematurely despite knowledge of the negative consequences of such impulsive actions.

CONCLUSIONS

Our findings underscore the integral role value plays in regulating impulsivity and suggest that the dopaminergic system influences impulsivity through the mediation of value learning.

On the effects of impulsivity and compulsivity on neural correlates of model-based performance

Impaired goal-directed behavior is associated with a range of mental disorders, implicating underlying transdiagnostic factors. While compulsivity has been linked to reduced model-based (MB) control, impulsivity has rarely been studied in the context of reinforcement learning despite its links to reward processing and cognitive control. This study investigated the neural mechanisms underlying MB control and the influence of impulsivity and compulsivity, using EEG data from 238 individuals during a two-step decision making task. Single-trial analyses revealed a modulation of the feedback-related negativity (FRN), where amplitudes were higher after common transitions and positive reward prediction error (RPE), indicating a valence effect. Meanwhile, enhanced P3 amplitudes after rare transitions and both positive and negative RPE possibly reflect surprise. In a second step, we regressed the mean b values of the effect of RPE on the EEG signals onto self-reported impulsivity and compulsivity and behavioral MB control (w). The effect of RPE on FRN-related activity was mainly associated with higher w scores, linking the FRN to MB control. Crucially, the modulation of the P3 by RPE was negatively associated with compulsivity, pointing to a deficient mental model in highly compulsive individuals.

Differential phase-amplitude coupling in nucleus accumbens and orbitofrontal cortex reflects decision-making during a delay discounting task

BACKGROUND

The impulsive choice is characterized by the preference for a small immediate reward over a bigger delayed one. The mechanisms underlying impulsive choices are linked to the activity in the Nucleus Accumbens (NAc), the orbitofrontal cortex (OFC), and the dorsolateral striatum (DLS). While the study of functional connectivity between brain areas has been key to understanding a variety of cognitive processes, it remains unclear whether functional connectivity differentiates impulsive-control decisions.

METHODS

To study the functional connectivity both between and within NAc, OFC, and DLS during a delay discounting task, we concurrently recorded local field potential in NAc, OFC, and DLS in rats. We then quantified the degree of phase-amplitude coupling (PAC), coherence, and Granger Causality between oscillatory activities in animals exhibiting either a high (HI) or low (LI) tendency for impulsive choices.

RESULTS

Our results showed a differential pattern of PAC during decision-making in OFC and NAc, but not in DLS. While theta-gamma PAC in OFC was associated with self-control decisions, a higher delta-gamma PAC in both OFC and NAc biased decisions toward impulsive choices in both HI and LI groups. Furthermore, during the reward event, Granger Causality analysis indicated a stronger NAc➔OFC gamma contribution in the HI group, while the LI group showed a higher OFC➔NAc gamma contribution.

CONCLUSIONS

The overactivity in NAc during reward in the HI group suggests that exacerbated contribution of NAcCore can lead to an overvaluation of reward that biases the behavior toward the impulsive choice.

Neurocognitive function and medical care utilization in Veterans treated for substance use disorder

BACKGROUND

Veterans with substance use disorder (SUD) are at high risk for cognitive problems due to neurotoxic effects of chronic drug and alcohol use coupled in many cases with histories of traumatic brain injury (TBI). These problems may in turn result in proneness to SUD relapse and reduced adherence to medical self-care regimens and therefore reliance on health care systems. However, the direct relationship between cognitive function and utilization of Veterans Health Administration (VHA) SUD and other VHA health care services has not been evaluated. We sought initial evidence as to whether neurocognitive performance relates to repeated health care engagement in Veterans as indexed by estimated VHA care costs.

METHODS

Neurocognitive performance in 76 Veterans being treated for SUD was assessed using CNS-Vital Signs, a commercial computerized cognitive testing battery, and related to histories of outpatient and inpatient/residential care costs as estimated by the VHA Health Economics Resource Center.

RESULTS

After controlling for age, an aggregate metric of overall neurocognitive performance (Neurocognition Index) correlated negatively with total VHA health care costs, particularly with SUD-related outpatient care costs but also with non-mental health-related care costs. Barratt Impulsiveness Scale scores also correlated positively with total VHA care costs.

CONCLUSIONS

In Veterans receiving SUD care, higher impulsivity and lower cognitive performance were associated with greater health care utilization within the VHA system. This suggests that veterans with SUD who show lower neurocognitive performance are at greater risk for continued health problems that require healthcare engagement. Cognitive rehabilitation programs developed for brain injury and other neurological conditions could be tried in Veterans with SUD to improve their health outcomes.

Trait Reward Sensitivity Modulates Connectivity with the Temporoparietal Junction and Anterior Insula during Strategic Decision Making

Many decisions happen in social contexts such as negotiations, yet little is understood about how people balance fairness versus selfishness. Past investigations found that activation in brain areas involved in executive function and reward processing was associated with people offering less with no threat of rejection from their partner, compared to offering more when there was a threat of rejection. However, it remains unclear how trait reward sensitivity may modulate activation and connectivity patterns in these situations. To address this gap, we used task-based fMRI to examine the relation between reward sensitivity and the neural correlates of bargaining choices. Participants (N = 54) completed the Sensitivity to Punishment (SP)/Sensitivity to Reward (SR) Questionnaire and the Behavioral Inhibition System/Behavioral Activation System scales. Participants performed the Ultimatum and Dictator Games as proposers and exhibited strategic decisions by being fair when there was a threat of rejection, but being selfish when there was not a threat of rejection. We found that strategic decisions evoked activation in the Inferior Frontal Gyrus (IFG) and the Anterior Insula (AI). Next, we found elevated IFG connectivity with the Temporoparietal junction (TPJ) during strategic decisions. Finally, we explored whether trait reward sensitivity modulated brain responses while making strategic decisions. We found that people who scored lower in reward sensitivity made less strategic choices when they exhibited higher AI-Angular Gyrus connectivity. Taken together, our results demonstrate how trait reward sensitivity modulates neural responses to strategic decisions, potentially underscoring the importance of this factor within social and decision neuroscience.

The association of impulsivity with depression and anxiety symptoms: A transdiagnostic network analysis and replication

BACKGROUND

Impulsivity increases the risk for depression and anxiety. However, the granular pathways among them remain unknown. A network approach that moves from disorder-level analysis to symptom-level analysis can provide further understanding of psychopathological mechanisms. In this study, we examined the network structure of impulsivity and separate and comorbid symptoms of depression and anxiety.

METHODS

Regularized partial-correlation networks were estimated using cross-sectional data from 1047 Chinese participants aged 18-26 years (main dataset, mean age = 21.45 ± 2.01 years) and 325 Chinese participants aged 18-36 years (an independent replication dataset, mean age = 21.49 ± 3.73 years), including impulsivity-depression, impulsivity-anxiety, and impulsivity-depression-anxiety networks. The datasets were collected from 1 June 2023 to 4 August 2023 and from 27 April 2022 to 16 May 2022, respectively. Impulsivity, depression, and anxiety were assessed using Barratt Impulsiveness Scale Version 11, Patient Health Questionnaire-9, and Generalized Anxiety Disorder-7, respectively. Bridge centrality was analyzed, and a network comparison test (NCT) was conducted to investigate the differences between the main dataset and replication dataset.

RESULTS

The motor impulsivity dimension was revealed to be closely connected with individual symptoms of depression and anxiety regardless of whether they were in separate disorder forms or comorbid forms. In all the networks, motor impulsivity was the most important bridge node. The NCT showed comparable network connectivity and network structure between the main and replication datasets.

LIMITATIONS

The use of cross-sectional data limited the inferences about the direction of causality between variables.

CONCLUSIONS

These findings elucidate the psychopathological mechanisms underlying how impulsivity functions within depression, anxiety, and comorbidity and support that motor impulsivity is an important risk factor across different mental disorders and is responsible for comorbidity. The implications of these findings are discussed.

Reward value and internal state differentially drive impulsivity and motivation

Goal-directed behavior is influenced by both reward value as well as internal state. A large body of research has focused on how reward value and internal drives such as hunger influence motivation in rodent models, however less work has focused on how these factors may differentially affect impulsivity. In these studies, we tested the effect of internal drive versus reward value on different facets of reward-related behavior including impulsive action, impulsive choice and, motivation. We varied reward value by changing the concentration of sucrose in the reward outcome, and varied internal drive by manipulating thirst through water restriction. Consistent with the literature we found that both internal state and reward value influenced motivation. However, we found that in high effort paradigms, only internal state influenced motivation with minimal effects of reward value. Interestingly, we found that internal state and reward value differentially influence different subtypes of impulsivity. Internal state, and to a lesser extent, reward value, influenced impulsive action as measured by premature responding. On the other hand, there were minimal effects of either reward value or homeostatic state on impulsive choice as measured by delay discounting. Overall, these studies begin to address how internal state and reward value differentially drive impulsive behavior. Understanding how these factors influence impulsivity is important for developing behavioral interventions and treatment targets for patients with dysregulated motivated or impulsive behavior.