Children with ADHD symptoms show decreased activity in ventral striatum during the anticipation of reward, irrespective of ADHD diagnosis

Extraction of brain function pattern with visual-capture-task fMRI using dynamic time-window method in ADHD children

Attention deficit/Hyperactivity disorder (ADHD) has a great impact on children's development. This paper uses a novel adaptive brain state extraction algorithm to construct a dynamic time-window brain network, which captures the brain function pattern characteristics of ADHD children with higher temporal resolution. The test data were acquired by functional magnetic resonance imaging (fMRI) obtained from 23 children with ADHD during the visual-capture-task [age: (8.27 ± 2.77)]. A spatial standard deviation method is used after the initial data processing, to extract the brain activity pattern state; An improved clustering algorithm is constructed to verify the changes made to the dynamic time-window brain network model. There can be seen clear differences between each state within 0.05 s after the test. The results show that our improved new framework can effectively obtain the characteristics of dynamic brain functional connection strength changes during the task. In addition, the new algorithm is able to capture the dynamic changes of the brain network, with an 80 % improvement compared to traditional methods for the average modularity value Q. This work demonstrates a novel approach to find out the pattern changes between dynamic brain function connections, which can be of great significance for the adjuvant treatment of children with ADHD.

In Context: A Developmental Model of Reward Processing, With Implications for Autism and Sensitive Periods

OBJECTIVE

Differences in reward processing have been associated with numerous psychiatric disorders, including autism and attention-deficit/hyperactivity disorder (ADHD). Many attempts to understand reward processing characterize differences in clinical populations after disorder onset; however, divergence may begin much earlier. In fact, the typical developmental progression of reward processing in infancy and early childhood is poorly understood. We re-conceptualize classic infant developmental constructs such as preferential looking into a Six-Component Developmental Model of Reward Processing: an infant- and young child-focused framework to guide research and assessment of reward processing across development.

METHOD

The extant developmental literature including recent textbooks, systematic reviews, and meta-analyses was reviewed to build a conceptual framework. We describe experimental paradigms to assess each developmental component of reward processing longitudinally from infancy. A timeline of each component's emergence was estimated.

RESULTS

Six components of reward processing were identified-association, discrimination, preference/valuation, effort, anticipation, and response. Selected evidence suggests emergence between birth and 6 months. Application of this model to autism led to a reinterpretation of existing disparate results, and illuminated a path to study the developmental processes underlying a popular hypothesis of autism, the motivation hypothesis. Current evidence further suggests that a sensitive period may exist for the emergence of reward processing.

CONCLUSION

The proposed framework offers a useful reconceptualization of the extant literature. Future longitudinal work using the suggested experimental paradigms with high-risk populations could elucidate the developmental trajectory of the components and timing of potential sensitive period(s) for each component.

Processing of social and monetary rewards in autism spectrum disorders

BACKGROUND

Reward processing has been proposed to underpin the atypical social feature of autism spectrum disorder (ASD). However, previous neuroimaging studies have yielded inconsistent results regarding the specificity of atypicalities for social reward processing in ASD.

AIMS

Utilising a large sample, we aimed to assess reward processing in response to reward type (social, monetary) and reward phase (anticipation, delivery) in ASD.

METHOD

Functional magnetic resonance imaging during social and monetary reward anticipation and delivery was performed in 212 individuals with ASD (7.6-30.6 years of age) and 181 typically developing participants (7.6-30.8 years of age).

RESULTS

Across social and monetary reward anticipation, whole-brain analyses showed hypoactivation of the right ventral striatum in participants with ASD compared with typically developing participants. Further, region of interest analysis across both reward types yielded ASD-related hypoactivation in both the left and right ventral striatum. Across delivery of social and monetary reward, hyperactivation of the ventral striatum in individuals with ASD did not survive correction for multiple comparisons. Dimensional analyses of autism and attention-deficit hyperactivity disorder (ADHD) scores were not significant. In categorical analyses, post hoc comparisons showed that ASD effects were most pronounced in participants with ASD without co-occurring ADHD.

CONCLUSIONS

Our results do not support current theories linking atypical social interaction in ASD to specific alterations in social reward processing. Instead, they point towards a generalised hypoactivity of ventral striatum in ASD during anticipation of both social and monetary rewards. We suggest this indicates attenuated reward seeking in ASD independent of social content and that elevated ADHD symptoms may attenuate altered reward seeking in ASD.

Prenatal exposure to air pollution and childhood internalizing problems: roles of shyness and anterior cingulate cortex activity

BACKGROUND

Prenatal exposure to air pollution increases the risk for psychiatric disorders characterized by internalizing problems. In this study, we examined the roles of shyness and anterior cingulate cortex (ACC) activity in the association between prenatal exposure to polycyclic aromatic hydrocarbons (PAH) and children's internalizing problems at 7-9 years old.

METHODS

Participants include 53 children (31 girls, 22 boys). Personal air monitoring was conducted over 48 continuous hours during the third trimester of pregnancy to measure 8 PAHs. Mothers reported children's shyness (Emotionality Activity Sociability Temperament Survey) at age 5 and internalizing problems (Child Behavior Checklist) at ages 7-9. ACC activity was measured by fMRI during the Simon Spatial Incompatibility task at ages 7-9.

RESULTS

Shyness mediated the association between prenatal PAH exposure and internalizing problems. Higher prenatal PAH exposure predicted increased shyness, which in turn predicted greater internalizing problems. Moreover, left ACC activity during the Simon task moderated the association between prenatal PAH exposure and internalizing problems. Prenatal PAH exposure predicted increased risk for internalizing problems only when children showed heightened left ACC activity during the resolution of cognitive conflict.

CONCLUSIONS

Our study innovatively synthesizes the fields of developmental psychology and environmental health science to offer new insights into the risk factors for anxiety disorders. Facilitating the development of healthy reactive and regulatory processes may improve the developmental outcomes for children highly exposed to air pollution.

Shared and Distinct Patterns of Functional Connectivity to Emotional Faces in Autism Spectrum Disorder and Attention-Deficit/Hyperactivity Disorder Children

Impairments in emotional face processing are demonstrated by individuals with neurodevelopmental disorders (NDDs), including autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD), which is associated with altered emotion processing networks. Despite accumulating evidence of high rates of diagnostic overlap and shared symptoms between ASD and ADHD, functional connectivity underpinning emotion processing across these two neurodevelopmental disorders, compared to typical developing peers, has rarely been examined. The current study used magnetoencephalography to investigate whole-brain functional connectivity during the presentation of happy and angry faces in 258 children (5–19 years), including ASD, ADHD and typically developing (TD) groups to determine possible differences in emotion processing. Data-driven clustering was also applied to determine whether the patterns of connectivity differed among diagnostic groups. We found reduced functional connectivity in the beta band in ASD compared to TD, and a further reduction in the ADHD group compared to the ASD and the TD groups, across emotions. A group-by-emotion interaction in the gamma frequency band was also observed. Greater connectivity to happy compared to angry faces was found in the ADHD and TD groups, while the opposite pattern was seen in ASD. Data-driven subgrouping identified two distinct subgroups: NDD-dominant and TD-dominant; these subgroups demonstrated emotion- and frequency-specific differences in connectivity. Atypicalities in specific brain networks were strongly correlated with the severity of diagnosis-specific symptoms. Functional connectivity strength in the beta network was negatively correlated with difficulties in attention; in the gamma network, functional connectivity strength to happy faces was positively correlated with adaptive behavioural functioning, but in contrast, negatively correlated to angry faces. Our findings establish atypical frequency- and emotion-specific patterns of functional connectivity between NDD and TD children. Data-driven clustering further highlights a high degree of comorbidity and symptom overlap between the ASD and ADHD children.

Effects of family history of substance use disorder on reward processing in adolescents with and without attention-deficit/hyperactivity disorder

Patients with attention‐deficit/hyperactivity disorder (ADHD) often develop early onset substance use disorder (SUD) and show poor treatment outcomes. Both disorders show similar reward‐processing alterations, but it is unclear whether these are associated with familial vulnerability to SUD. Our aim was to investigate effects of family history of SUD (FH) on reward processing in individuals with and without ADHD, without substance misuse. Behavioural and functional magnetic resonance imaging (fMRI) data from a modified monetary incentive delay task were compared between participants with and without FH (FH positive [FH+]: n = 76 and FH negative [FH−]: n = 69; 76 with ADHD, aged 16.74 ± 3.14, 82 males), while accounting for continuous ADHD scores. The main analysis showed distinct positive association between ADHD scores and reaction times during neutral versus reward condition. ADHD scores were also positively associated with anticipatory responses of dorsolateral prefrontal cortex, independent of FH. There were no main FH effects on brain activation. Yet, FH+ participants showed distinct neural alterations in ventrolateral prefrontal cortex (VLPFC), dependent on ADHD. This was driven by positive association between ADHD scores and VLPFC activation during reward outcome, only in FH+. Sensitivity analysis with stricter SUD index showed hyperactivation of anterior cingulate cortex for FH+, independent of ADHD, during reward anticipation. There were no FH or ADHD effects on activation of ventral striatum in any analysis. Findings suggest both FH and ADHD effects in circuits of reward and attention/memory during reward processing. Future studies should examine whether these relate to early substance use initiation in ADHD and explore the need for adjusted SUD prevention strategies.

Structure-function coupling within the reward network in preschool children predicts executive functioning in later childhood

Early differences in reward behavior have been linked to executive functioning development. The nucleus accumbens (NAc) and orbitofrontal cortex (OFC) are activated by reward-related tasks and identified as key nodes of the brain circuit that underlie reward processing. We aimed to investigate the relation between NAc-OFC structural and functional connectivity in preschool children, as well as associations with future reward sensitivity and executive function. We showed that NAc-OFC structural and functional connectivity were not significantly associated in preschool children, but both independently predicted sensitivity to reward in males in a left-lateralized manner. Moreover, significant NAc-OFC structure-function coupling was only found in individuals who performed poorly on executive function tasks in later childhood, but not in the middle- and high-performing groups. As structure-function coupling is proposed to measure functional specialization, this finding suggests premature functional specialization within the reward network, which may impede dynamic communication with other regions, affects executive function development. Our study also highlights the utility of multimodal imaging data integration when studying the effects of reward network functional flexibility in the preschool age, a critical period in brain and executive function development.

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Functional connectivity is not tethered to structural connectivity in preschool age.

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Higher degree of SC-FC coupling reflects lower plasticity in early childhood.

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Gender differences in reward sensitivity were present as early as in preschool age.

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Early reward network SC-FC coupling affects later executive function.

Cortical Development Mediates Association of Prenatal Maternal Depressive Symptoms and Child Reward Sensitivity: A Longitudinal Study

OBJECTIVE

Maternal depression during pregnancy has long-term impacts on offspring. This study used neuroimaging and behavioral data from children aged 4 to 6 years and investigated whether prenatal maternal depressive symptoms (pre-MDS) associated with child cortical morphological development and subsequent reward-related behaviors in preschoolers.

METHOD

Pre-MDS was measured using the Edinburgh Postnatal Depression Scale at 26 weeks of pregnancy. Children (n = 130) underwent structural magnetic resonance imaging (MRI) at both 4 and 6 years of age. Child sensitivity to reward and punishment was reported by mothers when children were 6 years of age. Linear mixed-effect models examined pre-MDS associations with child cortical thickness and surface area. Mediation analysis examined whether cortical development mediated associations between pre-MDS and child sensitivity to reward and punishment.

RESULTS

The 3-way interactions of pre-MDS, age, and sex on cortical thickness and surface area were not statistically significant. We found a significant interaction of pre-MDS with sex on the cortical surface area but not on thickness or their growth from 4 to 6 years, adjusting for ethnicity, socioeconomic status, baseline age, and postnatal MDS as covariates. Higher pre-MDS scores were associated with larger surface areas in the prefrontal cortex, superior temporal gyrus, and superior parietal lobe (SPL) in boys, whereas the opposite pattern was seen in girls. The SPL surface area mediated the relationship between pre-MDS and sensitivity to reward in girls.

CONCLUSION

Prenatal maternal depression alters the cortical morphology of pre-schoolers in a sex-dependent manner.

Prenatal environmental tobacco smoke exposure alters children's cognitive control circuitry: A preliminary study

BACKGROUND AND OBJECTIVES

Prenatal exposure to environmental tobacco smoke (ETS) is associated with increased attention problems in children, however, the effects of such exposure on children's brain structure and function have not been studied. Herein, we probed effects of prenatal ETS on children's cognitive control circuitry and behavior.

METHODS

Forty-one children (7-9 years) recruited from a prospective longitudinal birth cohort of non-smoking mothers completed structural and task-functional magnetic resonance imaging to evaluate effects of maternal ETS exposure, measured by maternal prenatal urinary cotinine. Attention problems and externalizing behaviors were measured by parent report on the Child Behavior Checklist.

RESULTS

Compared to non-exposed children, exposed children had smaller left and right thalamic and inferior frontal gyrus (IFG) volumes, with large effect sizes (p-FDR < .05, Cohen's D range from 0.79 to 1.07), and increased activation in IFG during the resolution of cognitive conflict measured with the Simon Spatial Incompatibility Task (38 voxels; peak t(25) = 5.25, p-FWE = .005). Reduced thalamic volume was associated with increased IFG activation and attention problems, reflecting poor cognitive control. Mediation analyses showed a trend toward left thalamic volume mediating the association between exposure and attention problems (p = .05).

CONCLUSIONS

Our findings suggest that maternal ETS exposure during pregnancy has deleterious effects on the structure and function of cognitive control circuitry which in turn affects attentional capacity in school-age children. These findings are consistent with prior findings documenting the effects of active maternal smoking on chidlren's neurodevleoment, pointing to the neurotixicity of nicotine regardless of exposure pathway.

Which Child Will Benefit From a Behavioral Intervention for ADHD? A Pilot Study to Predict Intervention Efficacy From Individual Reward Sensitivity

Objective: This article aims to assess whether individual differences in reward sensitivity can be used to predict which children with attention-deficit/hyperactivity disorder (ADHD) will benefit most from behavioral interventions that include reinforcement. Methods: A 12-week behavioral intervention was offered to 21 children with ADHD and their parents. Reward sensitivity was assessed prior to the intervention using a combination of psychological and physiological measures. ADHD symptoms were assessed pre- and posttreatment using the Strengths and Weaknesses of ADHD and Normal behavior (SWAN) rating scale. Results: Lower scores on one of the questionnaire scales were associated with greater pre/posttreatment differences in ADHD symptoms. Conclusion: We found that pre/posttreatment change was associated with one measure of parent-rated reward sensitivity. Children with low impulsive negative behavior toward gaining reward improved most during treatment. This result suggests that aspects of reward-related behaviors in ADHD may be useful to predict the effectiveness of treatment.

This Is Your Brain on Irritability: A Clinician's Guide to Understanding How We Know What We Know Now, and What We Need to Know in the Future, About Irritability in Children and Adolescents

Irritability is a common reason why children and adolescents are brought for psychiatric care. Although research is advancing what is known about the underlying brain and behavior mechanisms of irritability, clinicians often are shut out of that research. This article explains some of these research methods, providing brief summaries of what is known about brain/behavior mechanisms in disorders involving irritability, including bipolar disorder, disruptive mood dysregulation disorder, attention-deficit/hyperactivity disorder, and autism spectrum disorder. Greater access to these methods may help clinicians now and in the future, with such mechanisms translated into improved care, as occurs in the treatment of childhood leukemia.

Is Attention-Deficit/Hyperactivity Disorder a Risk Syndrome for Parkinson's Disease?

Recent epidemiological evidence indicates that diagnosis of attention-deficit/hyperactivity disorder (ADHD) is associated with increased risk for diseases of the basal ganglia and cerebellum, including Parkinson's disease (PD). The evidence reviewed here indicates that deficits in striatal dopamine are a shared component of the causal chains that produce these disorders. Neuropsychological studies of adult ADHD, prodromal PD, and early-stage PD reveal similar deficits in executive functions, memory, attention, and inhibition that are mediated by similar neural substrates. These and other findings are consistent with the possibility that ADHD may be part of the PD prodrome. The mechanisms that may mediate the association between PD and ADHD include neurotoxic effects of stimulants, other environmental exposures, and Lewy pathology. Understanding the nature of the association between PD and ADHD may provide insight into the etiology and pathogenesis of both disorders. The possible contribution of stimulants to this association may have important clinical and public health implications.

Effects of substance misuse on reward-processing in patients with attention-deficit/hyperactivity disorder

Attention-Deficit/Hyperactivity Disorder (ADHD) and Substance Use Disorder (SUD) often co-occur and are associated with treatment resistance. Both disorders are characterized by similar reward-processing deficits with decreased striatal responses to reward anticipation, though literature is inconsistent. It is unclear whether substance misuse exaggerates reward-processing deficits observed in ADHD. The aim of this study was to examine substance misuse effects on reward-processing in ADHD. Functional MRI data in a Monetary Incentive Delay (MID) task from a multi-site study were compared across ADHD groups with and without substance misuse (ADHD + SM and ADHD-only, respectively) and healthy controls (n = 40/group, 74 males and 46 females, aged 13.7-25.9 years). Substance misuse was defined as misuse of alcohol, nicotine, or drugs. Groups were matched with presence/absence of parental SUD to avoid interference with SUD trait effects. Compared to ADHD-only and controls, ADHD + SM showed hyperactivation in putamen during reward anticipation. Compared to controls, the ADHD groups showed hypoactivation in motor/sensory cortices and hyperactivation in frontal pole and OFC during reward outcome. ADHD + SM also showed hyperactivation in frontal pole during neutral outcome. Moreover, ADHD + SM patients showed higher callous-unemotional (CU) traits that were positively correlated with putamen responses to reward anticipation. Our results show distinct condition-independent neural activation profile for ADHD + SM compared to ADHD-only and controls. Effects of comorbid substance misuse and variability of its prevalence across ADHD studies might have contributed to inconsistencies in ADHD literature. Contrasted with findings for reward-processing in SUD literature, results potentially suggest distinct underlying mechanisms for SUD subgroups with different characteristics, like antisocial/psychopathic traits.

Treatment Efficacy and Clinical Effectiveness of EEG Neurofeedback as a Personalized and Multimodal Treatment in ADHD: A Critical Review

PURPOSE

Recent reviews have proposed that scientifically validated standard EEG neurofeedback (NF) protocols are an efficacious and specific treatment for attention-deficit hyperactivity disorder (ADHD). Here, we review the current evidence for the treatment efficacy and clinical effectiveness of NF in ADHD to investigate whether NF treatment personalization (standard protocols matched to the electrophysiological features of ADHD) and combination with other interventions (psychosocial, sleep hygiene and nutritional advice) might yield superior long-term treatment outcomes relative to non-personalized NF and medication monotreatments.

METHODS

The electronic databases PubMed and PsycINFO were systematically searched using our key terms. Of the 38 resulting studies, 11 randomized controlled trials (RCTs) and open-label studies were eligible for inclusion. Studies were analyzed for effect sizes and remission rates at the end of treatment and at follow-up. The effects of personalized and multimodal NF treatments were compared to non-personalized NF monotreatments and with two benchmark medication studies.

RESULTS

The analysis of RCTs indicated that the long-term effects of personalized NF interventions were superior to non-personalized NF and comparable to those of medication alone or in combination with behavioral intervention. The analysis of open-label trials further indicates that the interaction of NF with parental interventions, sleep and nutritional advice might yield superior clinical effectiveness relative to NF and medication monotreatments.

CONCLUSION

Personalized and multimodal NF interventions seem to yield superior treatment efficacy relative to NF alone and superior clinical effectiveness relative to medication. We propose that treatment outcomes may be further enhanced by adjusting NF non-specific factors (eg, reinforcement contingencies) to specific ADHD characteristics (eg, reward sensitivity). Future NF research should focus on the systematic evaluation of the treatment outcomes of personalized and multimodal treatments.

A Systematic Review of the Positive Valence System in Autism Spectrum Disorder

This review synthesized current literature of behavioral and cognitive studies targeting reward processing in autism spectrum disorder (ASD). The National Institute of Mental Health's Research Domain Criteria (RDoC) Positive Valence System (PVS) domain was used as an overarching framework. The objectives were to determine which component operations of reward processing may be atypical in ASD and consequently postulate a heuristic model of reward processing in ASD that could be evaluated with future research. 34 studies were identified from the Embase, PubMed, PsycINFO, and Web of Science databases and included in the review using guidelines from the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (also known as PRISMA guidelines). The extant literature suggested potential relationships between social symptoms of ASD and PVS sub-constructs of reward anticipation, probabilistic and reinforcement learning, reward prediction error, reward (probability), delay, and effort as well as between restricted and repetitive behaviors and interests (RRBIs) and PVS-sub constructs of initial response to reward, reward anticipation, reward (probability), delay, and effort. However, these findings are limited by a sparse and mixed literature for some sub-constructs. We put forward a developmentally informed heuristic model that posits how these component reward processes may be implicated in early ASD behaviors as well as later emerging and more intransigent symptoms. Future research is needed to comprehensively evaluate the proposed model.

Toward a Revised Nosology for Attention-Deficit/Hyperactivity Disorder Heterogeneity

Attention-deficit/hyperactivity disorder (ADHD) is among the many syndromes in the psychiatric nosology for which etiological signal and clinical prediction are weak. Reducing phenotypic and mechanistic heterogeneity should be useful to arrive at stronger etiological and clinical prediction signals. We discuss key conceptual and methodological issues, highlighting the role of dimensional features aligned with Research Domain Criteria and cognitive, personality, and temperament theory as well as neurobiology. We describe several avenues of work in this area, utilizing different statistical, computational, and machine learning approaches to resolve heterogeneity in ADHD. We offer methodological and conceptual recommendations. Methodologically, we propose that an integrated approach utilizing theory and advanced computational logic to address targeted questions, with consideration of developmental context, can render the heterogeneity problem tractable for ADHD. Conceptually, we conclude that the field is on the cusp of justifying an emotionally dysregulated subprofile in ADHD that may be useful for clinical prediction and treatment testing. Cognitive profiles, while more nascent, may be useful for clinical prediction and treatment assignment in different ways depending on developmental stage. Targeting these psychological profiles for neurobiological and etiological study to capture different pathophysiological routes remains a near-term opportunity. Subtypes are likely to be multifactorial, cut across multiple dimensions, and depend on the research or clinical outcomes of interest for their ultimate selection. In this context parallel profiles based on cognition, emotion, and specific neural signatures appear to be on the horizon, each with somewhat different utilities. Efforts to integrate such cross-cutting profiles within a conceptual dysregulation framework are well underway.

KCNJ6 variants modulate reward-related brain processes and impact executive functions in attention-deficit/hyperactivity disorder

KCNJ6, encoding a potassium channel subunit, regulates the excitability of dopaminergic neurons and is expressed in attention-deficit/hyperactivity disorder (ADHD)-relevant brain regions. As a potential ADHD risk gene, KCNJ6, therefore, may contribute to the endophenotypic variation of the disorder. The impact of two SNPs, rs7275707 and rs6517442, both located in the transcriptional control region of KCNJ6, on reporter gene expression was explored in cultured cells. The KCNJ6 variants were then tested for association with ADHD and personality traits in a family-based sample (165 affected children) and an adult case-control sample (450 patients, 426 controls). Furthermore, the genotypic influence on performance in an n-back task and a cued continuous performance test (cCPT) was investigated by electroencephalography recordings. Finally, rs6517442 function was assessed by a reward anticipation paradigm using functional magnetic resonance imaging. Different haplotypes of rs7275707 and rs6517442 significantly influenced KCNJ6 gene expression proving their functional relevance on the molecular level. In the family-based children sample rs7275707 was associated with ADHD (p = .038). Moreover, rs7275707 showed association with the personality trait of Reward Dependence (p = .031). In the ADHD group, both rs7275707 and rs6517442 influenced the Go-centroid location in the cCPT and the N200 amplitude in the n-back task. Furthermore, ventral striatal activation was impacted by rs6517442 during reward anticipation. Our data indicate that functional variants of KCNJ6 influence brain activity during reward-related and executive processes supporting the view of a differential, age-dependent modulatory impact of dopamine-related brain processes in ADHD risk.

Emotional Instability Relates to Ventral Striatum Activity During Reward Anticipation in Females

Both non-emotional symptoms, such as inattention, and symptoms of emotional instability (EI) are partially co-varying and normally distributed in the general population. Attention Deficit Hyperactivity Disorder (ADHD), which is associated with both inattention and emotional instability, has been related to lower reward anticipation activation in the ventral striatum. However, it is not known whether non-emotional dysregulation, such as inattention, or EI—or both—are associated with this effect. We hypothesized that altered reward processing relates specifically to EI. To test this, 29 healthy participants were recruited to this functional MRI study (n = 15 females). Reward processing was studied using a modified version of the Monetary Incentive Delay (MID) task. Brown Attention-Deficit Disorder Scales questionnaire was used to assess EI and inattention symptoms on a trait level. We observed less ventral striatal activation during reward anticipation related to the EI trait in females, also when controlling for the inattention trait, but not in the whole sample or males only. Our study suggests the existence of sex differences in the relationship between reward processing and EI/inattention traits.

The influence of subcortical shortcuts on disordered sensory and cognitive processing

The very earliest stages of sensory processing have the potential to alter how we perceive and respond to our environment. These initial processing circuits can incorporate subcortical regions, such as the thalamus and brainstem nuclei, which mediate complex interactions with the brain's cortical processing hierarchy. These subcortical pathways, many of which we share with other animals, are not merely vestigial but appear to function as 'shortcuts' that ensure processing efficiency and preservation of vital life-preserving functions, such as harm avoidance, adaptive social interactions and efficient decision-making. Here, we propose that functional interactions between these higher-order and lower-order brain areas contribute to atypical sensory and cognitive processing that characterizes numerous neuropsychiatric disorders.

Executive function in children with Tourette syndrome and attention-deficit/hyperactivity disorder: Cross-disorder or unique impairments?

Findings of executive functioning deficits in Tourette syndrome (TS) have so far been inconsistent, possibly due to methodological challenges of previous studies, such as the use of small sample sizes and not accounting for comorbid attention-deficit/hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), or medication use. We aimed to address these issues by examining several areas of executive functioning (response inhibition, attentional flexibility, cognitive control, and working memory) and psychomotor speed in 174 8-to-12-year-old children with TS [n = 34 without (TS-ADHD) and n = 26 with comorbid ADHD (TS+ADHD)], ADHD without tics (ADHD-TS; n = 54), and healthy controls (n = 60). We compared executive functioning measures and psychomotor speed between these groups and related these to ADHD severity across the whole sample, and tic severity across the TS groups. Children with TS+ADHD, but not TS-ADHD, made more errors on the cognitive control task than healthy children, while TS-ADHD had a slower psychomotor speed compared to healthy controls. The ADHD group showed impairment in cognitive control and working memory versus healthy controls. Moreover, higher ADHD severity was associated with poorer cognitive control and working memory across all groups; there was no relation between any of the executive functioning measures and tic severity. OCD severity or medication use did not influence our results. In conclusion, we found little evidence for executive function impairments inherent to TS. Executive function problems appear to manifest predominantly in relation to ADHD symptomatology, with both cross-disorder and unique features of neuropsychological functioning when cross-comparing TS and ADHD.

Neural reward processing in paediatric Tourette syndrome and/or attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is the most common comorbidity in individuals with Tourette syndrome (TS). Yet, it is unclear to what extent TS and ADHD show overlapping or distinct neural abnormalities. ADHD has been associated with altered reward processing, but there are very few studies on reward processing in TS. This study assessed neural activation of basal ganglia and thalamus during reward anticipation and receipt in children with TS and/or ADHD. We analysed mean activations of a priori specified regions of interest during an fMRI monetary incentive delay task. Data was used from 124 children aged 8-12 years (TS n = 47, of which 29 had comorbid ADHD; ADHD n = 29; healthy controls n = 48). ADHD severity across ADHD and TS groups and healthy controls was marginally related to hypoactivation of the right nucleus accumbens during reward anticipation; this effect was not moderated by TS diagnosis. We detected no associations of neural activation with TS. The association between ADHD severity and hypoactivation of the right nucleus accumbens during reward anticipation, independent of the presence or absence of TS, is in line with the view of nucleus accumbens hypoactivation as a dimensional, neurofunctional marker of ADHD severity, transcending the boundaries of primary diagnosis.

Reward, Control & Decision-Making in Cannabis Use Disorder: Insights from Functional MRI

The recreational consumption of cannabis has increased significantly across the world with an estimated 180 million people currently using. In the United States, 4.1 million are currently diagnosed with cannabis use disorder. Cannabis dependence and abuse was combined into a single entity as a behavioral disorder with a problematic pattern of cannabis use and termed cannabis use disorder by the Diagnostic and Statistical Manual of Mental Disorders. Chronic use of cannabis has been linked with region-specific effects across the brain mediating reward processing, cognitive control and decision-making that are central to understanding addictive behaviors. This review presents a snapshot of the current literature assessing the effects of chronic cannabis use on human brain function via functional MRI. Studies employing various paradigms and contrasting cognitive activation amongst cannabis users and non-users were incorporated. The effects of trans-del-ta-9-tetrahydrocannabinol (Δ9-THC) in marijuana and other preparations of cannabis are mediated by the endocannabinoid system, which is also briefly introduced.Much variation exists in the current literature regarding the functional changes associated with chronic cannabis use. One possible explanation for this variation is the heterogeneity in study designs, with little implementation of standardized diagnostic criteria when selecting chronic users, distinct time points of participant assessment, differing cognitive paradigms and imaging protocols. As such, there is an urgent requirement for future investigations that further characterize functional changes associated with chronic cannabis use.

Effects of Exercise on Cognitive Performance in Children and Adolescents with ADHD: Potential Mechanisms and Evidence-based Recommendations

Attention Deficit Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder with a complex symptomatology, and core symptoms as well as functional impairment often persist into adulthood. Recent investigations estimate the worldwide prevalence of ADHD in children and adolescents to be ~7%, which is a substantial increase compared to a decade ago. Conventional treatment most often includes pharmacotherapy with central nervous stimulants, but the number of non-responders and adverse effects call for treatment alternatives. Exercise has been suggested as a safe and low-cost adjunctive therapy for ADHD and is reported to be accompanied by positive effects on several aspects of cognitive functions in the general child population. Here we review existing evidence that exercise affects cognitive functions in children with and without ADHD and present likely neurophysiological mechanisms of action. We find well-described associations between physical activity and ADHD, as well as causal evidence in the form of small to moderate beneficial effects following acute aerobic exercise on executive functions in children with ADHD. Despite large heterogeneity, meta-analyses find small positive effects of exercise in population-based control (PBC) children, and our extracted effect sizes from long-term interventions suggest consistent positive effects in children and adolescents with ADHD. Paucity of studies probing the effect of different exercise parameters impedes finite conclusions in this regard. Large-scale clinical trials with appropriately timed exercise are needed. In summary, the existing preliminary evidence suggests that exercise can improve cognitive performance intimately linked to ADHD presentations in children with and without an ADHD diagnosis. Based on the findings from both PBC and ADHD children, we cautiously provide recommendations for parameters of exercise.

Dissociation of impulsivity and aggression in mice deficient for the ADHD risk gene Adgrl3: Evidence for dopamine transporter dysregulation

Adhesion G protein-coupled receptor L3 (ADGRL3, LPHN3) has putative roles in neuronal migration and synapse function. Various polymorphisms in ADGRL3 have been linked with an increased risk of attention deficit/hyperactivity disorder (ADHD). In this study, we examined the characteristics of Adgrl3-deficient mice in multiple behavioural domains related to ADHD: locomotive activity, impulsivity, gait, visuospatial and recognition memory, sociability, anxiety-like behaviour and aggression. Additionally, we investigated the effect of Adgrl3-depletion at the transcriptomic level by RNA-sequencing three ADHD-relevant brain regions: prefrontal cortex (PFC), hippocampus and striatum. Adgrl3^-/- mice show increased locomotive activity across all tests and subtle gait abnormalities. These mice also show impairments across spatial memory and learning domains, alongside increased levels of impulsivity and sociability with decreased aggression. However, these alterations were absent in Adgrl3^+/- mice. Across all brain regions tested, the numbers of genes found to exhibit differential expression was relatively small, indicating a specific pathway of action, rather than a broad neurobiological perturbation. Gene-set analysis of differential expression in the PFC detected a number of ADHD-relevant pathways including dopaminergic synapses as well as cocaine and amphetamine addiction. The Slc6a3 gene coding for the dopamine transporter was the most dysregulated gene in the PFC. Unexpectedly, several neurohormone/peptides which are typically only expressed in the hypothamalus were found to be dysregulated in the striatum. Our study further validates Adgrl3 constitutive knockout mice as an experimental model of ADHD while providing neuroanatomical targets for future studies involving ADGRL3 modified models. This article is part of the Special Issue entitled 'Current status of the neurobiology of aggression and impulsivity'.

Can we use neuroimaging data to differentiate between subgroups of children with ADHD symptoms: A proof of concept study using latent class analysis of brain activity

BACKGROUND

Multiple pathway models of ADHD suggest that multiple, separable biological pathways may lead to symptoms of the disorder. If this is the case, it should be possible to identify subgroups of children with ADHD based on distinct patterns of brain activity. Previous studies have used latent class analysis (LCA) to define subgroups at the behavioral and cognitive level and to then test whether they differ at the neurobiological level. In this proof of concept study, we took a reverse approach. We applied LCA to functional imaging data from two previously published studies to explore whether we could identify subgroups of children with ADHD symptoms at the neurobiological level with a meaningful relation to behavior or neuropsychology.

METHODS

Fifty-six children with symptoms of ADHD (27 children with ADHD and 29 children with ASD and ADHD symptoms) and 31 typically developing children performed two neuropsychological tasks assessing reward sensitivity and temporal expectancy during functional magnetic resonance imaging. LCA was used to identify subgroups with similar patterns of brain activity separately for children with ADHD-symptoms and typically developing children. Behavioral and neuropsychological differences between subgroups were subsequently investigated.

RESULTS

For typically developing children, a one-subgroup model gave the most parsimonious fit, whereas for children with ADHD-symptoms a two-subgroup model best fits the data. The first ADHD subgroup (n = 49) showed attenuated brain activity compared to the second subgroup (n = 7) and to typically developing children (n = 31). Notably, the ADHD subgroup with attenuated brain activity showed less behavioral problems in everyday life.

CONCLUSIONS

In this proof of concept study, we showed that we could identify distinct subgroups of children with ADHD-symptoms based on their brain activity profiles. Generalizability was limited due to the small sample size, but ultimately such neurobiological profiles could improve insight in individual prognosis and treatment options.

Overlapping and Distinct Cognitive Impairments in Attention-Deficit/Hyperactivity and Autism Spectrum Disorder without Intellectual Disability

Attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) are commonly comorbid, share genetic liability, and often exhibit overlapping cognitive impairments. Clarification of shared and distinct cognitive effects while considering comorbid symptoms across disorders has been lacking. In the current study, children ages 7-15 years assigned to three diagnostic groups:ADHD (n = 509), ASD (n = 97), and controls (n = 301) completed measures spanning the cognitive domains of attention/arousal, working memory, set-shifting, inhibition, and response variability. Specific processes contributing to response variability were examined using a drift diffusion model, which separately quantified drift rate (i.e., efficiency of information processing), boundary separation (i.e., speed-accuracy trade-offs), and non-decision time. Children with ADHD and ASD were impaired on attention/arousal, processing speed, working memory, and response inhibition, but did not differ from controls on measures of delayed reward discounting, set-shifting, or interference control. Overall, impairments in the ASD group were not attributable to ADHD symptoms using either continuous symptom measures or latent categorical grouping approaches. Similarly, impairments in the ADHD group were not attributable to ASD symptoms. When specific RT parameters were considered, children with ADHD and ASD shared impairments in drift rate. However, children with ASD were uniquely characterized by a wider boundary separation. Findings suggest a combination of overlapping and unique patterns of cognitive impairment for children with ASD as compared to those with ADHD, particularly when the processes underlying reaction time measures are considered separately.

Orbitofrontal Signaling of Future Reward is Associated with Hyperactivity in Attention-Deficit/Hyperactivity Disorder

Alterations in motivated behavior are a hallmark of attention-deficit/hyperactivity disorder (ADHD), one of the most common psychiatric disorders in children and adolescents. The orbitofrontal cortex (OFC) plays a key role in controlling goal-directed behavior, but the link between OFC dysfunction and behavioral deficits in ADHD, particularly in adolescence, remains poorly understood. Here we used advanced high-resolution functional magnetic resonance imaging (fMRI) of the human OFC in adolescents with ADHD and typically developing (TD) controls (N = 39, age 12-16, all male except for one female per group) to study reward-related OFC responses and how they relate to behavioral dysfunction in ADHD. During fMRI data acquisition, participants performed a simple decision-making task, allowing us to image expectation-related responses to small and large monetary outcomes. Across all participants, we observed significant signal increases to large versus small expected rewards in the OFC. These responses were significantly enhanced in ADHD relative to TD participants. Moreover, stronger reward-related activity was correlated with individual differences in hyperactive/impulsive symptoms in the ADHD group, whereas high cognitive ability was associated with normalized OFC responses. These results provide evidence for the importance of OFC dysfunctions in the neuropathology of ADHD, highlighting the role of OFC-dependent goal-directed control mechanisms in this disorder.SIGNIFICANCE STATEMENT Attention-deficit/hyperactivity disorder (ADHD) is characterized by alterations in motivated behavior which can be understood as diminished goal-directed control. The orbitofrontal cortex (OFC) plays a key role in controlling goal-directed behavior, but its potential contribution to ADHD symptomatology remains poorly understood. Using high-resolution fMRI, we show that adolescent ADHD patients display enhanced OFC signaling of future rewards and that these increased reward-related responses are correlated with the severity of hyperactivity/impulsivity. These findings suggest that an inability to adequately evaluate future outcomes may translate into maladaptive behavior in ADHD patients. They also challenge the idea that dysfunctions in dopaminergic brain areas are the sole contributor to reward-related symptoms in ADHD and point to a central contribution of goal-directed control circuits in hyperactivity.

The effects of early life stress on reward processing

Early life stress (ELS), in the form of childhood maltreatment, abuse, or neglect, increases the risk for psychiatric sequelae later in life. The neurobiology of response to early stress and of reward processing overlap substantially, leading to the prediction that reward processing may be a primary mediator of the effects of early life stress. We describe a growing body of literature investigating the effects of early life stressors on reward processing in animals and humans. Despite variation in the reviewed studies, an emerging pattern of results indicates that ELS results in deficits of ventral striatum-related functions of reward responsiveness and approach motivation, especially when the stressor is experienced in early in development. For stressors experienced later in the juvenile period and adolescence, the animal literature suggests an opposite effect, in which ELS results in increased hedonic drive. Future research in this area will help elucidate the transdiagnostic impact of early life stress, and therefore potentially identify and intervene with at-risk youth, prior to the emergence of clinical psychopathology.

Risky decision-making in children with and without ADHD: A prospective study

Learning from past decisions can enhance successful decision-making. It is unclear whether difficulties in learning from experience may contribute to risky decision-making, which may be altered among individuals with attention-deficit/hyperactivity disorder (ADHD). This study follows 192 children with and without ADHD aged 5 to 10 years for approximately 2.5 years and examines their risky decision-making using the Balloon Emotional Learning Task (BELT), a computerized assessment of sequential risky decision-making in which participants pump up a series of virtual balloons for points. The BELT contains three task conditions: one with a variable explosion point, one with a stable and early explosion point, and one with a stable and late explosion point. These conditions may be learned via experience on the task. Contrary to expectations, ADHD status was not found to be related to greater risk-taking on the BELT, and among younger children ADHD status is in fact associated with reduced risk-taking. In addition, the typically-developing children without ADHD showed significant learning-related gains on both stable task conditions. However, the children with ADHD demonstrated learning on the condition with a stable and early explosion point, but not on the condition with the stable and late explosion point, in which more pumps are required before learning when the balloon will explode. Learning during decision-making may be more difficult for children with ADHD. Because adapting to changing environmental demands requires the use of feedback to guide future behavior, negative outcomes associated with childhood ADHD may partially reflect difficulties in learning from experience.

Prospective memory in children with attention deficit hyperactivity disorder: a review

OBJECTIVE

The objective of the paper is to synthesize the research on prospective memory (PM) in children with attention-deficit/hyperactivity disorder (ADHD).

METHOD

Research on PM and ADHD in youth was synthesized according to the PRISMA guidelines and a summary of the types of PM deficits typically seen in these children, as well as the methods currently available to assess and treat these deficits is provided. Suggestions on ways to better manage PM deficits in children's everyday lives are also discussed.

RESULTS

Six studies have investigated PM in children with ADHD. The majority of these studies found a deficit in time-based PM, but not event-based PM. The mechanisms underlying this deficit, however, are still unknown. There are currently no specific measures available to clinically assess PM in children and there are no specific evidence-based interventions available that specifically target PM deficits in children with ADHD.

CONCLUSION

Remediation strategies aimed at compensating for these PM deficits in daily life may be most useful. Nevertheless, more research is necessary to better understand PM in children with ADHD.