Dopamine D2 Receptor Modulates Exercise Related Effect on Cortical Excitation/Inhibition and Motor Skill Acquisition

Exercise is known to benefit motor skill learning in health and neurological disease. Evidence from brain stimulation, genotyping, and Parkinson's disease studies converge to suggest that the dopamine D2 receptor, and shifts in the cortical excitation and inhibition (E:I) balance, are prime candidates for the drivers of exercise-enhanced motor learning. However, causal evidence using experimental pharmacological challenge is lacking. We hypothesized that the modulatory effect of the dopamine D2 receptor on exercise-induced changes in the E:I balance would determine the magnitude of motor skill acquisition. To test this, we measured exercise-induced changes in excitation and inhibition using paired-pulse transcranial magnetic stimulation (TMS) in 22 healthy female and male humans, and then had participants learn a novel motor skill-the sequential visual isometric pinch task (SVIPT). We examined the effect of D2 receptor blockade (800 mg sulpiride) on these measures within a randomized, double-blind, placebo-controlled design. Our key result was that motor skill acquisition was driven by an interaction between the D2 receptor and E:I balance. Specifically, poorer skill learning was related to an attenuated shift in the E:I balance in the sulpiride condition, whereas this interaction was not evident in placebo. Our results demonstrate that exercise-primed motor skill acquisition is causally influenced by D2 receptor activity on motor cortical circuits.

Evaluating the regulatory function of non-coding autism-associated single nucleotide polymorphisms on gene expression in human brain tissue

Common variants account for most of the estimated heritability associated with autism spectrum disorder (autism). Although several replicable single nucleotide polymorphisms (SNPs) for the condition have been detected using genome-wide association study (GWAS) methodologies, their pathophysiological relevance remains elusive. Examining this is complicated, however, as all detected loci are situated within non-coding regions of the genome. It is therefore likely that they possess roles of regulatory function as opposed to directly affecting gene coding sequences. To bridge the gap between SNP discovery and mechanistic insight, we applied a comprehensive bioinformatic pipeline to functionally annotate autism-associated polymorphisms and their non-coding linkage disequilibrium (i.e., non-randomly associated) partners. We identified 82 DNA variants of probable regulatory function that may contribute to autism pathogenesis. To validate these predictions, we measured the impact of 11 high-confidence candidates and their GWAS linkage disequilibrium partners on gene expression in human brain tissue from Autistic and non-Autistic donors. Although a small number of the surveyed variants exhibited measurable influence on gene expression as determined via quantitative polymerase chain reaction, these did not survive correction for multiple comparisons. Additionally, no significant genotype-by-diagnosis effects were observed for any of the SNP-gene associations. We contend that this may reflect an inability to effectively capture the modest, neurodevelopmental-specific impact of individual variants on biological dysregulation in available post-mortem tissue samples, as well as limitations in the existing autism GWAS data.

Attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD; also known as hyperkinetic disorder) is a common neurodevelopmental condition that affects children and adults worldwide. ADHD has a predominantly genetic aetiology that involves common and rare genetic variants. Some environmental correlates of the disorder have been discovered but causation has been difficult to establish. The heterogeneity of the condition is evident in the diverse presentation of symptoms and levels of impairment, the numerous co-occurring mental and physical conditions, the various domains of neurocognitive impairment, and extensive minor structural and functional brain differences. The diagnosis of ADHD is reliable and valid when evaluated with standard diagnostic criteria. Curative treatments for ADHD do not exist but evidence-based treatments substantially reduce symptoms and/or functional impairment. Medications are effective for core symptoms and are usually well tolerated. Some non-pharmacological treatments are valuable, especially for improving adaptive functioning. Clinical and neurobiological research is ongoing and could lead to the creation of personalized diagnostic and therapeutic approaches for this disorder.

Exploring Working Memory Capacity and Efficiency Processes to Understand Working Memory Training Outcomes in Primary School Children

Despite the abundance of research evaluating working memory training outcomes in children, few studies have examined the underlying cognitive mechanisms. This study aimed to contribute understanding by exploring whether working memory capacity (maximum span) and/or efficiency (basic and cognitive processing speeds), two proposed cognitive mechanisms, are associated with children's working memory performance immediately and 6-months post-intervention. We used data from a previous trial in primary school children (7-11 years) who completed working memory training (n = 52) or an active control (n = 36), comprising 10 sessions (each 20-minutes) in class over two weeks. Children completed five working memory measures at baseline, immediately and 6-months post-intervention: two Backwards Span and two Following Instructions measures (same paradigms as training activities), and one n-back measure (different paradigm). Maximum span, basic and cognitive processing speeds, and performance were calculated for each measure. Associations between change in maximum span, processing speeds and change in performance on the working memory measures from baseline to immediately and 6-months post-intervention did not differ between groups (all p < .05). Maximum span, processing speeds and performance on working memory measures did not differ between groups. Findings provide little evidence that the studied capacity or efficiency processes contribute to understanding working memory training outcomes in primary school children. Furthermore, working memory training did not have benefits for children's working capacity, efficiency or performance up to 6-months post-intervention. It is of interest for future studies to explore cognitive mechanisms, including strategy use, maximum span and information processing, in datasets where training effects are observed.

Age at diagnosis and diagnostic delay across attention-deficit hyperactivity and autism spectrums

BACKGROUND

Despite the known benefits of accurate and timely diagnosis for children with attention-deficit hyperactivity disorder and autism spectrum disorders (autism), for some children this goal is not always achieved. Existing research has explored diagnostic delay for autism and attention-deficit hyperactivity disorder only, and when attention-deficit hyperactivity disorder and autism co-occur, autism has been the focus. No study has directly compared age at diagnosis and diagnostic delay for males and females across attention-deficit hyperactivity disorder, autism and specifically, attention-deficit hyperactivity disorder + autism.

METHODS

Australian caregivers (N = 677) of children with attention-deficit hyperactivity disorder, autism or attention-deficit hyperactivity disorder + autism were recruited via social media (n = 594) and the Monash Autism and ADHD Genetics and Neurodevelopment Project (n = 83). Caregivers reported on their child's diagnostic process. Diagnostic delay was the mean difference between general initial developmental concerns and the child's attention-deficit hyperactivity disorder and autism diagnosis.

RESULTS

Children with autism were significantly younger at autism diagnosis than the attention-deficit hyperactivity disorder + autism group (ηp2 = 0.06), whereas children with attention-deficit hyperactivity disorder were significantly older at attention-deficit hyperactivity disorder diagnosis than the attention-deficit hyperactivity disorder + autism group (ηp2 = 0.01). Delay to attention-deficit hyperactivity disorder and autism diagnosis was significantly longer in the attention-deficit hyperactivity disorder + autism group compared to attention-deficit hyperactivity disorder (ηp2 = 0.02) and autism (η2 = 0.04) only. Delay to autism diagnosis for females with autism (η2 = 0.06) and attention-deficit hyperactivity disorder + autism (η2 = 0.04) was longer compared to males.

CONCLUSIONS

Having attention-deficit hyperactivity disorder + autism and being female were associated with longer delays to diagnosis. The reasons for these delays and possible adverse effects on outcomes require further study.

Can hubs of the human connectome be identified consistently with diffusion MRI?

Recent years have seen a surge in the use of diffusion MRI to map connectomes in humans, paralleled by a similar increase in processing and analysis choices. Yet these different steps and their effects are rarely compared systematically. Here, in a healthy young adult population (n = 294), we characterized the impact of a range of analysis pipelines on one widely studied property of the human connectome: its degree distribution. We evaluated the effects of 40 pipelines (comparing common choices of parcellation, streamline seeding, tractography algorithm, and streamline propagation constraint) and 44 group-representative connectome reconstruction schemes on highly connected hub regions. We found that hub location is highly variable between pipelines. The choice of parcellation has a major influence on hub architecture, and hub connectivity is highly correlated with regional surface area in most of the assessed pipelines (ρ > 0.70 in 69% of the pipelines), particularly when using weighted networks. Overall, our results demonstrate the need for prudent decision-making when processing diffusion MRI data, and for carefully considering how different processing choices can influence connectome organization.

Integration of xeno-free single-cell cloning in CRISPR-mediated DNA editing of human iPSCs improves homogeneity and methodological efficiency of cellular disease modeling

The capability to generate induced pluripotent stem cell (iPSC) lines, in tandem with CRISPR-Cas9 DNA editing, offers great promise to understand the underlying genetic mechanisms of human disease. The low efficiency of available methods for homogeneous expansion of singularized CRISPR-transfected iPSCs necessitates the coculture of transfected cells in mixed populations and/or on feeder layers. Consequently, edited cells must be purified using labor-intensive screening and selection, culminating in inefficient editing. Here, we provide a xeno-free method for single-cell cloning of CRISPRed iPSCs achieving a clonal survival of up to 70% within 7-10 days. This is accomplished through improved viability of the transfected cells, paralleled with provision of an enriched environment for the robust establishment and proliferation of singularized iPSC clones. Enhanced cell survival was accompanied by a high transfection efficiency exceeding 97%, and editing efficiencies of 50%-65% for NHEJ and 10% for HDR, indicative of the method's utility in stem cell disease modeling.

Effectiveness of lifestyle interventions for improving the physical health of children and adolescents taking antipsychotic medications: protocol for a systematic review and meta-analysis

INTRODUCTION

Children and adolescents are increasingly prescribed antipsychotic medications off-label in the treatment of behavioural disorders. While antipsychotic medications are effective in managing behavioural issues, they carry a significant risk of adverse events that compromise ongoing physical health. Of particular concern is the negative impact antipsychotic medications have on cardiometabolic health. Interventions that aim to modify lifestyle habits have the potential to alleviate the adverse effects of antipsychotic medication by enhancing weight management, increasing physical activity, promoting better nutritional practices, improving dietary habits and promoting healthier sleep patterns and sleep hygiene. However, a comprehensive review has not been performed to ascertain the effectiveness of lifestyle interventions for children and adolescents who are at increased risk of antipsychotic-induced compromises to their physical health.

METHODS AND ANALYSIS

This systematic review will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Four databases will be searched without any year constraints to identify randomised controlled trials that are published in the English language and report a lifestyle intervention compared with usual care with any physical health outcome measure. Trial registers and results repositories will be scoured to identify additional studies. Two reviewers will independently conduct screening, data extraction and quality assessment and compare the results. Quantitative data will be synthesised, where appropriate, through a random-effects meta-analysis model. Otherwise, data will be reported in a qualitative (narrative) synthesis. Heterogeneity will be quantified using the I2 statistic. The Cochrane Risk of Bias 2 tool will be used for risk of bias assessment. The Grading of Recommendations, Assessment, Development and Evaluation system will be used to evaluate the cumulative body of evidence.

ETHICS AND DISSEMINATION

Ethics approval is not required. The publication plan will target high-impact, peer-reviewed journals that fall under the scope of Psychiatry and Mental Health.

PROSPERO REGISTRATION NUMBER

CRD42022380277.

Amphetamines Improve the Motivation to Invest Effort in Attention-Deficit/Hyperactivity Disorder

Prevailing frameworks propose that a key feature of attention-deficit/hyperactivity disorder (ADHD) is lower motivation. An important component of motivation is the willingness to engage in cognitively or physically effortful behavior. However, the degree to which effort sensitivity is impaired in ADHD has rarely been tested, and the efficacy of stimulant medication in ameliorating any such impairments is unclear. Here, we tested 20 individuals with ADHD (11 males, 9 females) who were managed with amphetamine-based medication (dexamfetamine, lisdexamfetamine), and 24 controls (8 males, 16 females). Individuals with ADHD were tested over two counterbalanced sessions, ON and OFF their usual amphetamine-based medication. In each session, participants performed an effort-based decision-making task, in which they were required to choose how much cognitive or physical effort they were willing to engage in return for reward. Our results revealed three main findings. First, individuals with ADHD had lower motivation relative to controls to invest effort in both the cognitive and physical domains. Second, amphetamine increased motivation uniformly across both domains. Finally, the net effect of amphetamine treatment was to mostly restore motivation across both domains of effort relative to healthy controls. These data provide clear evidence for a heightened sensitivity to both cognitive and physical effort in ADHD, and reveal the efficacy of amphetamine-based drugs in restoring effort sensitivity to levels similar to controls. These findings confirm the existence of reduced motivational drive in ADHD, and more broadly provide direct causal evidence for a domain-general role of catecholamines in motivating effortful behavior.SIGNIFICANCE STATEMENT A core feature of attention-deficit/hyperactivity disorder (ADHD) is thought to be a heightened aversion to effort. Surprisingly, however, the degree to which effort sensitivity is impaired in ADHD has rarely been tested. More broadly, the relative efficacy of catecholamines in motivating the investment of cognitive and physical effort is unclear. We tested 20 individuals with ADHD ON and OFF amphetamines, and compared their behavior on an effort-based decision-making task to 24 controls. When tested OFF medication, the ADHD group was less cognitively and physically motivated than controls. However, amphetamines led to a comparable increase in motivation across both domains. This demonstrates the efficacy of catecholamines in facilitating domain-general effort, and highlights the broader potential of such drugs to treat disorders of motivation.

Mechanisms of cognitive disinhibition explain individual differences in adult attention deficit hyperactivity disorder traits

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) in adults is strongly associated with psychiatric comorbidity and functional impairment. Here, we aimed to use a newly developed online cognitive battery with strong psychometric properties for measuring individual differences in three cognitive mechanisms proposed to underlie ADHD traits in adults: 1) attentional control - the ability to mobilize cognitive resources to stop a prepotent motor response; 2) information sampling/gathering - adequate sampling of information in a stimulus detection task prior to making a decision; and 3) shifting - the ability to adapt behavior in response to positive and negative contingencies.

METHODS

This cross-sectional and correlational study recruited 650 adults (330 males) aged 18-69 years (M = 33.06; MD = 31.00; SD = 10.50), with previously diagnosed ADHD (n = 329) and those from the general community without a history of ADHD (n = 321). Self-report measures of ADHD traits (i.e., inattention/disorganization, impulsivity, hyperactivity) and the cognitive battery were completed online.

RESULTS

Latent class analysis, exploratory structural equation modeling and factor mixture modeling revealed self-reported ADHD traits formed a unidimensional and approximately normally distributed phenotype. Bayesian structural equation modeling demonstrated that all three mechanisms measured by the cognitive battery, explained unique, incremental variance in ADHD traits, with a total of 15.9% explained in the ADHD trait factor.

CONCLUSIONS

Attentional control and shifting, as well as the less researched cognitive process of information gathering, explain individual difference variance in self-reported ADHD traits with potential to yield genetic and neurobiological insights into adult ADHD.

Trans-ancestry meta-analysis of genome wide association studies of inhibitory control

Deficits in effective executive function, including inhibitory control are associated with risk for a number of psychiatric disorders and significantly impact everyday functioning. These complex traits have been proposed to serve as endophenotypes, however, their genetic architecture is not yet well understood. To identify the common genetic variation associated with inhibitory control in the general population we performed the first trans-ancestry genome wide association study (GWAS) combining data across 8 sites and four ancestries (N = 14,877) using cognitive traits derived from the stop-signal task, namely - go reaction time (GoRT), go reaction time variability (GoRT SD) and stop signal reaction time (SSRT). Although we did not identify genome wide significant associations for any of the three traits, GoRT SD and SSRT demonstrated significant and similar SNP heritability of 8.2%, indicative of an influence of genetic factors. Power analyses demonstrated that the number of common causal variants contributing to the heritability of these phenotypes is relatively high and larger sample sizes are necessary to robustly identify associations. In Europeans, the polygenic risk for ADHD was significantly associated with GoRT SD and the polygenic risk for schizophrenia was associated with GoRT, while in East Asians polygenic risk for schizophrenia was associated with SSRT. These results support the potential of executive function measures as endophenotypes of neuropsychiatric disorders. Together these findings provide the first evidence indicating the influence of common genetic variation in the genetic architecture of inhibitory control quantified using objective behavioural traits derived from the stop-signal task.

Associations Between Anxiety and Home Learning Difficulties in Children and Adolescents with ADHD During the COVID-19 Pandemic

The COVID-19 pandemic has markedly impacted functioning for children and adolescents including those with attention-deficit/hyperactivity disorder (ADHD). We explored home learning difficulties (HLD) during COVID-19 restrictions in Australian children (aged 5-17) with ADHD, aiming to: (1) describe home learning experiences, and (2) examine associations between child anxiety (i.e., concurrent anxiety symptoms and pre-existing anxiety disorder status) and HLD. Baseline data from the longitudinal ADHD COVID-19 Survey were used (n = 122). Parents reported on school factors and HLD; pre-existing anxiety and co-occurring difficulties; anxiety, ADHD, and oppositional symptoms; demographics; and medications. Parents retrospectively reported more children often looked forward to school pre-pandemic, than during the pandemic. Anxiety symptoms, but not pre-existing anxiety disorder status, were associated with HLD after accounting for covariates. ADHD inattention symptoms were also associated with HLD. Results support recommendations to continue pre-pandemic supports to assist with ADHD symptoms during home learning, and strategies/supports for families are discussed.

Against the use of the Strengths and Difficulties Questionnaire for Aboriginal and Torres Strait Islander children aged 2-15 years

OBJECTIVE

The Strengths and Difficulties Questionnaire is a widely used screening tool for emotional and behavioural problems in children. Recent quantitative analyses have raised concerns regarding its structural validity in Aboriginal and Torres Strait Islander communities. This paper aims to extend upon existing findings by analysing the factor structure of both the parent- and teacher-reported Strengths and Difficulties Questionnaire in this population across a broader age range than in previous studies.

METHODS

Participants were the caregivers and teachers of 1624 Aboriginal and Torres Strait Islander children (820 male, 804 female) aged 2-15 years from Waves 2-11 of the Longitudinal Study of Indigenous Children. The majority of children were Aboriginal living in major cities and inner regional areas. Internal consistency was estimated with McDonald's Omega. Exploratory structural equation modelling was conducted to investigate the factor structure of the parent-reported and teacher-reported versions of the Strengths and Difficulties Questionnaire.

RESULTS

Responses from teachers demonstrated higher internal consistency than responses from parents, which was unacceptably low across most age groups. The purported five-factor structure of the Strengths and Difficulties Questionnaire failed to be replicated across both parent- and teacher-reported questionnaires. The results of bifactor and hierarchical exploratory structural equation models also failed to approximate the higher-order summary scales. These results indicate that the Strengths and Difficulties Questionnaire subscales and summary scores do not provide a valid index of emotional and behavioural problems in Aboriginal and Torres Strait Islander children.

CONCLUSION

The Strengths and Difficulties Questionnaire should not be used with Aboriginal and Torres Strait Islander children.

Evidence Accumulation Rate Moderates the Relationship between Enriched Environment Exposure and Age-Related Response Speed Declines

Older adults exposed to enriched environments (EEs) maintain relatively higher levels of cognitive function, even in the face of compromised markers of brain health. Response speed (RS) is often used as a simple proxy to measure the preservation of global cognitive function in older adults. However, it is unknown which specific selection, decision, and/or motor processes provide the most specific indices of neurocognitive health. Here, using a simple decision task with electroencephalography (EEG), we found that the efficiency with which an individual accumulates sensory evidence was a critical determinant of the extent to which RS was preserved in older adults (63% female, 37% male). Moreover, the mitigating influence of EE on age-related RS declines was most pronounced when evidence accumulation rates were shallowest. These results suggest that the phenomenon of cognitive reserve, whereby high EE individuals can better tolerate suboptimal brain health to facilitate the preservation of cognitive function, is not just applicable to neuroanatomical indicators of brain aging but can be observed in markers of neurophysiology. Our results suggest that EEG metrics of evidence accumulation may index neurocognitive vulnerability of the aging brain.Significance Statement Response speed in older adults is closely linked with trajectories of cognitive aging. Here, by recording brain activity while individuals perform a simple computer task, we identify a neural metric that is a critical determinant of response speed. Older adults exposed to greater cognitive and social stimulation throughout a lifetime could maintain faster responding, even when this neural metric was impaired. This work suggests EEG is a useful technique for interrogating how a lifetime of stimulation benefits brain health in aging.

Dissecting Schizotypy and Its Association With Cognition and Polygenic Risk for Schizophrenia in a Nonclinical Sample

Schizotypy is a multidimensional construct that captures a continuum of risk for developing schizophrenia-spectrum psychopathology. Existing 3-factor models of schizotypy, consisting of positive, negative, and disorganized dimensions have yielded mixed evidence of genetic continuity with schizophrenia using polygenic risk scores. Here, we propose an approach that involves splitting positive and negative schizotypy into more specific subdimensions that are phenotypically continuous with distinct positive symptoms and negative symptoms recognized in clinical schizophrenia. We used item response theory to derive high-precision estimates of psychometric schizotypy using 251 self-report items obtained from a non-clinical sample of 727 (424 females) adults. These subdimensions were organized hierarchically using structural equation modeling into 3 empirically independent higher-order dimensions enabling associations with polygenic risk for schizophrenia to be examined at different levels of phenotypic generality and specificity. Results revealed that polygenic risk for schizophrenia was associated with variance specific to delusional experiences (γ = 0.093, P = .001) and reduced social interest and engagement (γ = 0.076, P = .020), and these effects were not mediated via the higher-order general, positive, or negative schizotypy factors. We further fractionated general intellectual functioning into fluid and crystallized intelligence in 446 (246 females) participants that underwent onsite cognitive assessment. Polygenic risk scores explained 3.6% of the variance in crystallized intelligence. Our precision phenotyping approach could be used to enhance the etiologic signal in future genetic association studies and improve the detection and prevention of schizophrenia-spectrum psychopathology.

Generation of induced pluripotent stem cell lines from three individuals with autism spectrum disorder

Uncovering the molecular mechanisms of autism spectrum disorder (autism) necessitates development of relevant experimental models that are capable of recapitulating features of the clinical phenotype. Using non-integrative episomal vectors, peripheral blood mononuclear cells derived from three unrelated individuals diagnosed with autism were reprogrammed to induced pluripotent stem cells (iPSCs). The resultant lines exhibited the expected cellular morphology, karyotype, and evidence of pluripotency. These iPSCs constitute a valuable resource to support investigations of the underlying aetiology of autism.

Regional, circuit and network heterogeneity of brain abnormalities in psychiatric disorders

The substantial individual heterogeneity that characterizes people with mental illness is often ignored by classical case-control research, which relies on group mean comparisons. Here we present a comprehensive, multiscale characterization of the heterogeneity of gray matter volume (GMV) differences in 1,294 cases diagnosed with one of six conditions (attention-deficit/hyperactivity disorder, autism spectrum disorder, bipolar disorder, depression, obsessive-compulsive disorder and schizophrenia) and 1,465 matched controls. Normative models indicated that person-specific deviations from population expectations for regional GMV were highly heterogeneous, affecting the same area in <7% of people with the same diagnosis. However, these deviations were embedded within common functional circuits and networks in up to 56% of cases. The salience-ventral attention system was implicated transdiagnostically, with other systems selectively involved in depression, bipolar disorder, schizophrenia and attention-deficit/hyperactivity disorder. Phenotypic differences between cases assigned the same diagnosis may thus arise from the heterogeneous localization of specific regional deviations, whereas phenotypic similarities may be attributable to the dysfunction of common functional circuits and networks.

Practitioner Review: It's time to bridge the gap - understanding the unmet needs of consumers with attention-deficit/hyperactivity disorder - a systematic review and recommendations

OBJECTIVE

Understanding the unmet needs of healthcare consumers with attention-deficit/hyperactivity disorder (ADHD) (individuals with ADHD and their caregivers) provides critical insight into gaps in services, education and research that require focus and funding to improve outcomes. This review examines the unmet needs of ADHD consumers from a consumer perspective.

METHODS

A standardised search protocol identified peer-reviewed studies published between December 2011 and December 2021 focusing on consumer-identified needs relating to ADHD clinical care or research priorities.

RESULTS

1,624 articles were screened with 23 studies that reviewed examining the needs of ADHD consumers from Europe, the U.K., Hong Kong, Iran, Australia, the U.S.A. and Canada. Consumer-identified needs related to: treatment that goes beyond medication (12 studies); improved ADHD-related education/training (17 studies); improved access to clinical services, carer support and financial assistance (14 studies); school accommodations/support (6 studies); and ongoing treatment efficacy research (1 study).

CONCLUSION

ADHD consumers have substantial unmet needs in clinical, psychosocial and research contexts. Recommendations to address these needs include: improving access to and quality of multimodal care provision; incorporating recovery principles into care provision; fostering ADHD health literacy; and increasing consumer participation in research, service development and ADHD-related training/education.

D2 receptor blockade eliminates exercise-induced changes in cortical inhibition and excitation

BACKGROUND

Although cardiorespiratory exercise is known to affect cortical excitatory and inhibitory activity, the neurochemical mechanisms driving this effect are poorly understood. Animal models of Parkinson's disease identify dopamine D2 receptor expression as a candidate mechanism, but the link between the D2 receptor and exercise-induced changes in cortical activity in humans is unknown.

OBJECTIVE

Here, we examined the effect of a selective dopamine D2 receptor antagonist, sulpiride, on exercise-induced changes in cortical activity.

METHODS

We acquired measures of excitatory and inhibitory activity of the primary motor cortex using transcranial magnetic stimulation (TMS) from 23 healthy adults, both before and after a 20-min bout of high-intensity interval cycling exercise. We examined the effect of D2 receptor blockade (800 mg sulpiride) on these measures within a randomised, double-blind, placebo-controlled crossover design.

RESULTS

Sulpiride abolished exercise-induced modulation of the cortical excitation:inhibition balance relative to placebo (P < 0.001, Cohen's d = 1.76). Sulpiride blocked both the increase in glutamatergic excitation and reduction in gamma-aminobutyric acid (GABA) inhibition that was observed following exercise in the placebo condition.

CONCLUSION

Our results provide causal evidence that D2 receptor blockade eliminates exercise-induced changes in excitatory and inhibitory cortical networks, and have implications for how exercise should be prescribed in diseases of dopaminergic dysfunction.

Precision behavioral phenotyping as a strategy for uncovering the biological correlates of psychopathology

Our capacity to measure diverse aspects of human biology has developed rapidly in the past decades, but the rate at which these techniques have generated insights into the biological correlates of psychopathology has lagged far behind. The slow progress is partly due to the poor sensitivity, specificity and replicability of many findings in the literature, which have in turn been attributed to small effect sizes, small sample sizes and inadequate statistical power. A commonly proposed solution is to focus on large, consortia-sized samples. Yet it is abundantly clear that increasing sample sizes will have a limited impact unless a more fundamental issue is addressed: the precision with which target behavioral phenotypes are measured. Here, we discuss challenges, outline several ways forward and provide worked examples to demonstrate key problems and potential solutions. A precision phenotyping approach can enhance the discovery and replicability of associations between biology and psychopathology.

Longitudinal Associations Between COVID-19 Stress and the Mental Health of Children With ADHD

OBJECTIVE

To investigate the longitudinal associations between COVID-19 induced stress (related to COVID-19 restrictions/changes), attention-deficit/hyperactivity disorder (ADHD) symptoms, oppositional symptoms, and mental health outcomes (negative affect, anxiety, depression, and irritability) in children with ADHD during the COVID-19 pandemic.

METHOD

Parents of 140 Australian children with ADHD (aged 5-17 years) completed an online survey in May 2020 during stay-at-home restrictions and 12-months later.

RESULTS

Baseline COVID-19 stress was associated with increased total ADHD symptom severity (β = .21, p = .007) and hyperactivity/impulsivity symptoms (β = .23, p = .002) at 12-months, after accounting for covariates (i.e., child age, gender, ADHD medication, socio-economic status, and baseline symptoms). Despite some indication of associations between baseline COVID-19 stress and 12-month oppositional symptoms and negative affect, these were attenuated when adjusting for baseline symptoms.

CONCLUSIONS

The study provides initial evidence of the medium-term impacts of pandemic-related stress for children with ADHD.

Gradients of striatal function in antipsychotic-free first-episode psychosis and schizotypy

Both psychotic illness and subclinical psychosis-like experiences (PLEs) have been associated with cortico-striatal dysfunction. This work has largely relied on a discrete parcellation of the striatum into distinct functional areas, but recent evidence suggests that the striatum comprises multiple overlapping and smoothly varying gradients (i.e., modes) of functional organization. Here, we investigated two of these functional connectivity modes, previously associated with variations in the topographic patterning of cortico-striatal connectivity (first-order gradient), and dopaminergic innervation of the striatum (second-order gradient), and assessed continuities in striatal function from subclinical to clinical domains. We applied connectopic mapping to resting-state fMRI data to obtain the first-order and second-order striatal connectivity modes in two distinct samples: (1) 56 antipsychotic-free patients (26 females) with first-episode psychosis (FEP) and 27 healthy controls (17 females); and (2) a community-based cohort of 377 healthy individuals (213 females) comprehensively assessed for subclinical PLEs and schizotypy. The first-order "cortico-striatal" and second-order "dopaminergic" connectivity gradients were significantly different in FEP patients compared to controls bilaterally. In the independent sample of healthy individuals, variations in the left first-order "cortico-striatal" connectivity gradient were associated with inter-individual differences in a factor capturing general schizotypy and PLE severity. The presumed cortico-striatal connectivity gradient was implicated in both subclinical and clinical cohorts, suggesting that variations in its organization may represent a neurobiological trait marker across the psychosis continuum. Disruption of the presumed dopaminergic gradient was only noticeable in patients, suggesting that neurotransmitter dysfunction may be more apparent to clinical illness.

Comparing Treatment Outcomes in Children and Adolescents With ADHD to Other Disorders Within an Australian and Dutch Outpatient Cohort

OBJECTIVE

Previous studies at child and youth mental health services (CYMHS) suggest that children with ADHD have poorer outcomes compared to those with other diagnoses. This study investigates this in more detail.

METHODS

Children with ADHD were compared to those with ASD and those with emotional disorders, on routinely collected outcomes at CYMHS in Australia (N = 2,513) and the Netherlands (N = 844).

RESULTS

Where the emotional disorders group reached a similar level of emotional symptoms at the end-of-treatment as the ADHD and ASD groups, the latter two groups still had higher scores on ADHD and ASD symptoms (attention and peer problems). The poorer outcomes were mainly explained by higher severity at baseline. In Australia, an ADHD and/or ASD diagnosis also independently contributed to worse outcomes.

CONCLUSION

Those with neurodevelopmental disorders within both countries had poorer outcomes than those with emotional disorders. Services should aim to optimize treatment to ensure best possible outcomes.

Examining the pharmacological and psychological treatment of child and adolescent ADHD in Australia: Protocol for a retrospective cohort study using linked national registry data

INTRODUCTION

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder which affects 5% of children globally. In Australia, it is estimated that 4.1% of children and adolescents have ADHD. While research has examined the treatment and outcomes of children with ADHD attending public mental health services during their time in the public system in Australia, it is not known what treatment they received before and after these treatment episodes, which will provide a more complete understanding of these children's treatment journey.

METHODS AND ANALYSIS

We will link clinical data from cohorts of children and adolescents treated in the public child and youth mental health and/or child development services in Brisbane, Melbourne and Sydney to the Medicare Benefits Schedule (MBS), Pharmaceutical Benefits Scheme (PBS) and National Death Index. MBS data will demonstrate the treatment journey with respect to clinicians seen, and treatment episodes from the public health service data sets will be examined to assess if the type and intensity of treatment are related to treatment outcomes. PBS data will reveal all psychotropic medications prescribed, allowing an examination of not just ADHD medications, but also other psychotropics which may indicate co-occurring conditions (eg, anxiety and mood disorders). Statistical analyses will include descriptive statistics to describe the rates of specific medications and clinician specialties seen. Linear and logistic regression will be used to model how treatment and sociodemographic variables relate to routinely collected outcome measures in the public health system while controlling for covarying factors.

ETHICS AND DISSEMINATION

This study has been approved by the following institutional ethics committees: (1) Children's Health Queensland Hospital and Health Service (HREC/21/QCHQ/76260), (2) The University of Queensland (2021/HE002143) and (3) The Australian Institute of Health and Welfare (EO2021/4/1300). Findings will be disseminated through peer-reviewed journals, conferences, professional associations and to public mental health services that treat ADHD.

Pharmacological Manipulations of Physiological Arousal and Sleep-Like Slow Waves Modulate Sustained Attention

Sustained attention describes our ability to keep a constant focus on a given task. This ability is modulated by our physiological state of arousal. Although lapses of sustained attention have been linked with dysregulations of arousal, the underlying physiological mechanisms remain unclear. An emerging body of work proposes that the intrusion during wakefulness of sleep-like slow waves, a marker of the transition toward sleep, could mechanistically account for attentional lapses. This study aimed to expose, via pharmacological manipulations of the monoamine system, the relationship between the occurrence of sleep-like slow waves and the behavioral consequences of sustained attention failures. In a double-blind, randomized-control trial, 32 healthy human male participants received methylphenidate, atomoxetine, citalopram or placebo during four separate experimental sessions. During each session, electroencephalography (EEG) was used to measure neural activity while participants completed a visual task requiring sustained attention. Methylphenidate, which increases wake-promoting dopamine and noradrenaline across cortical and subcortical areas, improved behavioral performance whereas atomoxetine, which increases dopamine and noradrenaline predominantly over frontal cortices, led to more impulsive responses. Additionally, citalopram, which increases sleep-promoting serotonin, led to more missed trials. Based on EEG recording, citalopram was also associated with an increase in sleep-like slow waves. Importantly, compared with a classical marker of arousal such as α power, only slow waves differentially predicted both misses and faster responses in a region-specific fashion. These results suggest that a decrease in arousal can lead to local sleep intrusions during wakefulness which could be mechanistically linked to impulsivity and sluggishness.SIGNIFICANCE STATEMENT We investigated whether the modulation of attention and arousal could not only share the same neuromodulatory pathways but also rely on similar neuronal mechanisms; for example, the intrusion of sleep-like activity within wakefulness. To do so, we pharmacologically manipulated noradrenaline, dopamine, and serotonin in a four-arm, randomized, placebo-controlled trial and examined the consequences on behavioral and electroencephalography (EEG) indices of attention and arousal. We showed that sleep-like slow waves can predict opposite behavioral signatures: impulsivity and sluggishness. Slow waves may be a candidate mechanism for the occurrence of attentional lapses since the relationship between slow-wave occurrence and performance is region-specific and the consequences of these local sleep intrusions are in line with the cognitive functions carried by the underlying brain regions.

Which Measures From a Sustained Attention Task Best Predict ADHD Group Membership?

Difficulty with sustaining attention to a task is a hallmark of ADHD. It would be useful to know which measures of sustained attention best predict a diagnosis of ADHD. Participants were 129 children with a diagnosis of ADHD and 129 matched controls who completed the fixed Sustained Attention to Response Task (SART). The number of commission and omission errors, standard deviation of response time (SDRT), tau, fast and slow frequency variability, d-prime, and mu were able to successfully classify children with and without ADHD. The mean response time, criterion, and sigma were not able to classify participants. The best classifiers were d-prime (0.75 Area Under the Receiver Operated Characteristic), tau (.74), SDRT (0.74), omission errors (0.72), commission errors (0.71), and SFAUS (0.70). This list of the best classifier measures derived from the SART may prove useful for the planning of future studies.

Digital cognitive training in children with attention-deficit/hyperactivity disorder: a study protocol of a randomised controlled trial

INTRODUCTION

Attention-deficit/hyperactivity disorder (ADHD) is one of the most prevalent neurodevelopmental disorders and is a persistent pattern of inattention and/or hyperactivity-impulsivity that interferes with daily functioning. Children with ADHD are developmentally vulnerable, with the disorder linked to emotional regulation difficulties, behavioural disturbances, as well as academic challenges. Emerging evidence suggests that children with ADHD may benefit from cognitive training interventions, including those focused on attention. This study aims to assess the immediate and long-term efficacy of an attention training intervention in children with ADHD.

METHODS AND ANALYSIS

This study is a preregistered, parallel, double blind, randomised controlled trial. Participants will comprise 104 children with a diagnosis of ADHD aged 5-8 years 11 months. Participants will be randomly allocated to either an adaptive, digital game-based (1) attention training programme (intervention) or (2) a numeracy programme (control). Both programmes will be delivered on a touchscreen tablet, and children will complete five 20 min sessions per week for a 5-week period at home (25 sessions in total). Assessments of the primary outcome (ie, attention and inhibitory control) and secondary outcomes (ie, selective attention, interference control, sustained attention, inhibition, behavioural attention, impairment in everyday functioning, working memory and executive functioning) will occur at preintervention, immediately postintervention and at 3-month follow-up. Multivariate linear regression will be employed to examine primary and secondary outcomes. The data analyst will be blinded to group membership.

ETHICS AND DISSEMINATION

Ethics approval has been obtained from the Monash University HREC (20495). Results will be disseminated through peer-reviewed journals, conference presentations, media outlets, the internet and various community/stakeholder activities.

TRIAL REGISTRATION NUMBER

ACTRN12620000964910, UTN U1111-1250-2620.

Dopamine influences attentional rate modulation in Macaque posterior parietal cortex

Cognitive neuroscience has made great strides in understanding the neural substrates of attention, but our understanding of its neuropharmacology remains incomplete. Although dopamine has historically been studied in relation to frontal functioning, emerging evidence suggests important dopaminergic influences in parietal cortex. We recorded single- and multi-unit activity whilst iontophoretically administering dopaminergic agonists and antagonists while rhesus macaques performed a spatial attention task. Out of 88 units, 50 revealed activity modulation by drug administration. Dopamine inhibited firing rates according to an inverted-U shaped dose-response curve and increased gain variability. D1 receptor antagonists diminished firing rates according to a monotonic function and interacted with attention modulating gain variability. Finally, both drugs decreased the pupil light reflex. These data show that dopamine shapes neuronal responses and modulates aspects of attentional processing in parietal cortex.

Examining the neural correlates of error awareness in a large fMRI study

Goal-directed behavior is dependent upon the ability to detect errors and implement appropriate posterror adjustments. Accordingly, several studies have explored the neural activity underlying error-monitoring processes, identifying the insula cortex as crucial for error awareness and reporting mixed findings with respect to the anterior cingulate cortex (ACC). Variable patterns of activation have previously been attributed to insufficient statistical power. We therefore sought to clarify the neural correlates of error awareness in a large event-related functional magnetic resonance imaging (fMRI) study. Four hundred and two healthy participants undertook the error awareness task, a motor Go/No-Go response inhibition paradigm in which participants were required to indicate their awareness of commission errors. Compared to unaware errors, aware errors were accompanied by significantly greater activity in a network of regions, including the insula cortex, supramarginal gyrus (SMG), and midline structures, such as the ACC and supplementary motor area (SMA). Error awareness activity was related to indices of task performance and dimensional measures of psychopathology in selected regions, including the insula, SMG, and SMA. Taken together, we identified a robust and reliable neural network associated with error awareness.

Recent Attitudes toward ADHD in the Broader Community: A Systematic Review

OBJECTIVE

This review aimed to understand the broader community's attitudes toward ADHD, which could facilitate public health interventions to improve outcomes for individuals with ADHD.

METHODS

A standardized protocol identified peer-reviewed studies focusing on attitudes of broader community samples, published from January 2014 to February 2020 (inclusive).

RESULTS

A total of 1,318 articles were screened and 10 studies were included, examining attitudes of broader community samples from Australia, Sweden, Germany, Finland, Korea, Indonesia, and the United States. Findings revealed that broader community samples displayed varying degrees of ADHD-related knowledge, negative attitudes (that ADHD is over-diagnosed; that pharmacological treatment is not acceptable; that those with ADHD are more likely to exhibit poor behavior), and a desire for maintaining social distance from individuals with ADHD.

CONCLUSION

Findings suggest that community attitudes are generally negative toward those with ADHD. Targeted mental health literacy could provide an important avenue for improving the broader community's attitudes toward those with ADHD.

Physical Health, Media Use, and Mental Health in Children and Adolescents With ADHD During the COVID-19 Pandemic in Australia

OBJECTIVE

To examine the impact of COVID-19 restrictions among children with attention-deficit/hyperactivity disorder (ADHD).

METHODS

Parents of 213 Australian children (5-17 years) with ADHD completed a survey in May 2020 when COVID-19 restrictions were in place (i.e., requiring citizens to stay at home except for essential reasons).

RESULTS

Compared to pre-pandemic, children had less exercise (Odds Ratio (OR) = 0.4; 95% CI 0.3-0.6), less outdoor time (OR = 0.4; 95% 0.3-0.6), and less enjoyment in activities (OR = 6.5; 95% CI 4.0-10.4), while television (OR = 4.0; 95% CI 2.5-6.5), social media (OR = 2.4; 95% CI 1.3-4.5), gaming (OR = 2.0; 95% CI 1.3-3.0), sad/depressed mood (OR = 1.8; 95% CI 1.2-2.8), and loneliness (OR = 3.6; 95% CI 2.3-5.5) were increased. Child stress about COVID-19 restrictions was associated with poorer functioning across most domains. Most parents (64%) reported positive changes for their child including more family time.

CONCLUSIONS

COVID-19 restrictions were associated with both negative and positive impacts among children with ADHD.

Cortical and subcortical neuroanatomical signatures of schizotypy in 3004 individuals assessed in a worldwide ENIGMA study

Neuroanatomical abnormalities have been reported along a continuum from at-risk stages, including high schizotypy, to early and chronic psychosis. However, a comprehensive neuroanatomical mapping of schizotypy remains to be established. The authors conducted the first large-scale meta-analyses of cortical and subcortical morphometric patterns of schizotypy in healthy individuals, and compared these patterns with neuroanatomical abnormalities observed in major psychiatric disorders. The sample comprised 3004 unmedicated healthy individuals (12-68 years, 46.5% male) from 29 cohorts of the worldwide ENIGMA Schizotypy working group. Cortical and subcortical effect size maps with schizotypy scores were generated using standardized methods. Pattern similarities were assessed between the schizotypy-related cortical and subcortical maps and effect size maps from comparisons of schizophrenia (SZ), bipolar disorder (BD) and major depression (MDD) patients with controls. Thicker right medial orbitofrontal/ventromedial prefrontal cortex (mOFC/vmPFC) was associated with higher schizotypy scores (r = 0.067, p_FDR = 0.02). The cortical thickness profile in schizotypy was positively correlated with cortical abnormalities in SZ (r = 0.285, p_spin = 0.024), but not BD (r = 0.166, p_spin = 0.205) or MDD (r = -0.274, p_spin = 0.073). The schizotypy-related subcortical volume pattern was negatively correlated with subcortical abnormalities in SZ (rho = -0.690, p_spin = 0.006), BD (rho = -0.672, p_spin = 0.009), and MDD (rho = -0.692, p_spin = 0.004). Comprehensive mapping of schizotypy-related brain morphometry in the general population revealed a significant relationship between higher schizotypy and thicker mOFC/vmPFC, in the absence of confounding effects due to antipsychotic medication or disease chronicity. The cortical pattern similarity between schizotypy and schizophrenia yields new insights into a dimensional neurobiological continuity across the extended psychosis phenotype.

Consortium neuroscience of attention deficit/hyperactivity disorder and autism spectrum disorder: The ENIGMA adventure

Neuroimaging has been extensively used to study brain structure and function in individuals with attention deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) over the past decades. Two of the main shortcomings of the neuroimaging literature of these disorders are the small sample sizes employed and the heterogeneity of methods used. In 2013 and 2014, the ENIGMA-ADHD and ENIGMA-ASD working groups were respectively, founded with a common goal to address these limitations. Here, we provide a narrative review of the thus far completed and still ongoing projects of these working groups. Due to an implicitly hierarchical psychiatric diagnostic classification system, the fields of ADHD and ASD have developed largely in isolation, despite the considerable overlap in the occurrence of the disorders. The collaboration between the ENIGMA-ADHD and -ASD working groups seeks to bring the neuroimaging efforts of the two disorders closer together. The outcomes of case-control studies of subcortical and cortical structures showed that subcortical volumes are similarly affected in ASD and ADHD, albeit with small effect sizes. Cortical analyses identified unique differences in each disorder, but also considerable overlap between the two, specifically in cortical thickness. Ongoing work is examining alternative research questions, such as brain laterality, prediction of case-control status, and anatomical heterogeneity. In brief, great strides have been made toward fulfilling the aims of the ENIGMA collaborations, while new ideas and follow-up analyses continue that include more imaging modalities (diffusion MRI and resting-state functional MRI), collaborations with other large databases, and samples with dual diagnoses.

Environmental exposures associated with elevated risk for autism spectrum disorder may augment the burden of deleterious de novo mutations among probands

Although the full aetiology of autism spectrum disorder (ASD) is unknown, familial and twin studies demonstrate high heritability of 60-90%, indicating a predominant role of genetics in the development of the disorder. The genetic architecture of ASD consists of a complex array of rare and common variants of all classes of genetic variation usually acting additively to augment individual risk. The relative contribution of heredity in ASD persists despite selective pressures against the classic autistic phenotype; a phenomenon thought to be explained, in part, by the incidence of spontaneous (or de novo) mutations. Notably, environmental exposures attributed as salient risk factors for ASD may play a causal role in the emergence of deleterious de novo variations, with several ASD-associated agents having significant mutagenic potential. To explore this hypothesis, this review article assesses published epidemiological data with evidence derived from assays of mutagenicity, both in vivo and in vitro, to determine the likely role such agents may play in augmenting the genetic liability in ASD. Broadly, these exposures were observed to elicit genomic alterations through one or a combination of: (1) direct interaction with genetic material; (2) impaired DNA repair; or (3) oxidative DNA damage. However, the direct contribution of these factors to the ASD phenotype cannot be determined without further analysis. The development of comprehensive prospective birth cohorts in combination with genome sequencing is essential to forming a causal, mechanistic account of de novo mutations in ASD that links exposure, genotypic alterations, and phenotypic consequences.

Social and Economic Costs of Attention-Deficit/Hyperactivity Disorder Across the Lifespan

OBJECTIVE

To determine the financial and non-financial costs of Attention-Deficit/Hyperactivity Disorder (ADHD) across the lifespan.

METHOD

The population costs of ADHD in Australia were estimated for the financial year 2018 to 2019 using a prevalence approach to cost estimation across all ages. Financial (healthcare, productivity, education and justice systems, and deadweight losses) and non-financial costs were measured (Disability Adjusted Life Years (DALYs)).

RESULTS

The total social and economic cost of ADHD in 2018 to 2019 were US$12.76 billion (range US$8.40 billion to US$17.44 billion, with per person costs of US$15,664 per year). Productivity costs made up 81% of the total financial costs, followed by deadweight losses (11%), and health system costs (4%). Loss in terms of wellbeing was significant (US$5.31 billion).

CONCLUSION

There is a need to raise public awareness of the considerable socioeconomic impact and burden of ADHD in order to drive investment and policy decisions that improve identification and treatment of ADHD.

Understanding the Diversity of Pharmacotherapeutic Management of ADHD With Co-occurring Autism: An Australian Cross-Sectional Survey

OBJECTIVES

Attention deficit hyperactivity disorder (ADHD) frequently co-occurs with other neurodevelopmental diagnoses, such as autism spectrum disorder (autism), which can make clinical decision making around symptom management challenging for clinicians. There is a paucity of research examining pharmacotherapeutic management of children who have ADHD with co-occurring diagnoses. We aimed to report on the co-occurring diagnoses and symptom profile of children, and report on medication use, stratified by ADHD, autism and ADHD + autism diagnoses.

METHODS AND MATERIALS

Caregivers of 505 children (2-18 years) with ADHD (n = 239), autism (n = 117), and co-occurring ADHD + autism (n = 149) completed a questionnaire on current medication use and clinical rating scales about their child's symptoms, as part of a broader project investigating diagnosis and management of symptoms in children with ADHD or autism.

RESULTS

The parents of the ADHD group reported a higher proportion of their children had learning disorders (17.15%) and speech and language disorders (4.60%) compared to the parents of the autism and ADHD + autism groups. Parents of the ADHD + autism group reported higher proportions of intellectual disability (5.37%), oppositional defiant disorder (20.13%), anxiety (38.93%), depression (6.71%) and genetic conditions (3.36%) in their children, in comparison to the parents of the ADHD and autism groups. Children with ADHD were reported to be taking a higher proportion of psychotropic medication (90%), followed by ADHD + autism (86%) and autism (39%). The parents of children with ADHD + autism reported a higher proportion of non-stimulant ADHD medication (25.5%), antipsychotic (18.79%), antidepressant (22.15%) and melatonin (31.54%) use by their children, compared to the parents of the ADHD and autism groups.

CONCLUSIONS

A similar proportion of children with ADHD + autism and ADHD were reported to be taking medication. However, the types of medication taken were different, as expected with reported co-occurring diagnoses. The complexity of symptoms and diagnoses in ADHD + autism warrants targeted research to optimize management and therapeutic outcomes.

Oculomotor deficits in attention deficit hyperactivity disorder (ADHD): A systematic review and comprehensive meta-analysis

Atypical motor coordination and cognitive processes, such as response inhibition and working memory, have been extensively researched in individuals with attention deficit hyperactivity disorder (ADHD). Oculomotor neural circuits overlap extensively with regions involved in motor planning and cognition, therefore studies of oculomotor function may offer unique insights into motor and cognitive control in ADHD. We performed a series of pairwise meta-analyses based on data from 26 oculomotor studies in ADHD to examine whether there were differences in performance on visually-guided saccade, gap, antisaccade, memory-guided, pursuit eye movements and fixation tasks. These analyses revealed oculomotor disturbances in ADHD, particularly for difficulties relating to saccade inhibition, memorizing visual target locations and initiating antisaccades. There was no evidence for pursuit eye movement disturbances or saccade dysmetria. Investigating oculomotor abnormalities in ADHD may provide insight into top-down cognitive control processes and motor control, and may serve as a promising biomarker in ADHD research and clinical practice.

Imaging Transcriptomics of Brain Disorders

Noninvasive neuroimaging is a powerful tool for quantifying diverse aspects of brain structure and function in vivo, and it has been used extensively to map the neural changes associated with various brain disorders. However, most neuroimaging techniques offer only indirect measures of underlying pathological mechanisms. The recent development of anatomically comprehensive gene expression atlases has opened new opportunities for studying the transcriptional correlates of noninvasively measured neural phenotypes, offering a rich framework for evaluating pathophysiological hypotheses and putative mechanisms. Here, we provide an overview of some fundamental methods in imaging transcriptomics and outline their application to understanding brain disorders of neurodevelopment, adulthood, and neurodegeneration. Converging evidence indicates that spatial variations in gene expression are linked to normative changes in brain structure during age-related maturation and neurodegeneration that are in part associated with cell-specific gene expression markers of gene expression. Transcriptional correlates of disorder-related neuroimaging phenotypes are also linked to transcriptionally dysregulated genes identified in ex vivo analyses of patient brains. Modeling studies demonstrate that spatial patterns of gene expression are involved in regional vulnerability to neurodegeneration and the spread of disease across the brain. This growing body of work supports the utility of transcriptional atlases in testing hypotheses about the molecular mechanism driving disease-related changes in macroscopic neuroimaging phenotypes.

Analysis of structural brain asymmetries in attention-deficit/hyperactivity disorder in 39 datasets

OBJECTIVE

Some studies have suggested alterations of structural brain asymmetry in attention-deficit/hyperactivity disorder (ADHD), but findings have been contradictory and based on small samples. Here, we performed the largest ever analysis of brain left-right asymmetry in ADHD, using 39 datasets of the ENIGMA consortium.

METHODS

We analyzed asymmetry of subcortical and cerebral cortical structures in up to 1,933 people with ADHD and 1,829 unaffected controls. Asymmetry Indexes (AIs) were calculated per participant for each bilaterally paired measure, and linear mixed effects modeling was applied separately in children, adolescents, adults, and the total sample, to test exhaustively for potential associations of ADHD with structural brain asymmetries.

RESULTS

There was no evidence for altered caudate nucleus asymmetry in ADHD, in contrast to prior literature. In children, there was less rightward asymmetry of the total hemispheric surface area compared to controls (t = 2.1, p = .04). Lower rightward asymmetry of medial orbitofrontal cortex surface area in ADHD (t = 2.7, p = .01) was similar to a recent finding for autism spectrum disorder. There were also some differences in cortical thickness asymmetry across age groups. In adults with ADHD, globus pallidus asymmetry was altered compared to those without ADHD. However, all effects were small (Cohen's d from -0.18 to 0.18) and would not survive study-wide correction for multiple testing.

CONCLUSION

Prior studies of altered structural brain asymmetry in ADHD were likely underpowered to detect the small effects reported here. Altered structural asymmetry is unlikely to provide a useful biomarker for ADHD, but may provide neurobiological insights into the trait.

The World Federation of ADHD International Consensus Statement: 208 Evidence-based conclusions about the disorder

BACKGROUND

Misconceptions about ADHD stigmatize affected people, reduce credibility of providers, and prevent/delay treatment. To challenge misconceptions, we curated findings with strong evidence base.

METHODS

We reviewed studies with more than 2000 participants or meta-analyses from five or more studies or 2000 or more participants. We excluded meta-analyses that did not assess publication bias, except for meta-analyses of prevalence. For network meta-analyses we required comparison adjusted funnel plots. We excluded treatment studies with waiting-list or treatment as usual controls. From this literature, we extracted evidence-based assertions about the disorder.

RESULTS

We generated 208 empirically supported statements about ADHD. The status of the included statements as empirically supported is approved by 80 authors from 27 countries and 6 continents. The contents of the manuscript are endorsed by 366 people who have read this document and agree with its contents.

CONCLUSIONS

Many findings in ADHD are supported by meta-analysis. These allow for firm statements about the nature, course, outcome causes, and treatments for disorders that are useful for reducing misconceptions and stigma.

The Monash Autism-ADHD genetics and neurodevelopment (MAGNET) project design and methodologies: a dimensional approach to understanding neurobiological and genetic aetiology

Background

ASD and ADHD are prevalent neurodevelopmental disorders that frequently co-occur and have strong evidence for a degree of shared genetic aetiology. Behavioural and neurocognitive heterogeneity in ASD and ADHD has hampered attempts to map the underlying genetics and neurobiology, predict intervention response, and improve diagnostic accuracy. Moving away from categorical conceptualisations of psychopathology to a dimensional approach is anticipated to facilitate discovery of data-driven clusters and enhance our understanding of the neurobiological and genetic aetiology of these conditions. The Monash Autism-ADHD genetics and neurodevelopment (MAGNET) project is one of the first large-scale, family-based studies to take a truly transdiagnostic approach to ASD and ADHD. Using a comprehensive phenotyping protocol capturing dimensional traits central to ASD and ADHD, the MAGNET project aims to identify data-driven clusters across ADHD-ASD spectra using deep phenotyping of symptoms and behaviours; investigate the degree of familiality for different dimensional ASD-ADHD phenotypes and clusters; and map the neurocognitive, brain imaging, and genetic correlates of these data-driven symptom-based clusters.

Methods

The MAGNET project will recruit 1,200 families with children who are either typically developing, or who display elevated ASD, ADHD, or ASD-ADHD traits, in addition to affected and unaffected biological siblings of probands, and parents. All children will be comprehensively phenotyped for behavioural symptoms, comorbidities, neurocognitive and neuroimaging traits and genetics.

Conclusion

The MAGNET project will be the first large-scale family study to take a transdiagnostic approach to ASD-ADHD, utilising deep phenotyping across behavioural, neurocognitive, brain imaging and genetic measures.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13229-021-00457-3.

Potential role for immune-related genes in autism spectrum disorders: Evidence from genome-wide association meta-analysis of autistic traits

The clinical heterogeneity of autism spectrum disorders majorly challenges their genetic study. Autism spectrum disorders symptoms occur in milder forms in the general population, as autistic-like traits, and share genetic factors with autism spectrum disorders. Here, we investigate the genetics of individual autistic-like traits to improve our understanding of autism spectrum disorders. We meta-analysed four population-based genome-wide association studies investigating four autistic-like traits – ‘attention-to-detail’, ‘imagination’, ‘rigidity’ and ‘social-skills’ (n = 4600). Using autism spectrum disorder summary statistics from the Psychiatric Genomic Consortium (N = 46,350), we applied polygenic risk score analyses to understand the genetic relationship between autism spectrum disorders and autistic-like traits. Using MAGMA, we performed gene-based and gene co-expression network analyses to delineate involved genes and pathways. We identified two novel genome-wide significant loci – rs6125844 and rs3731197 – associated with ‘attention-to-detail’. We demonstrated shared genetic aetiology between autism spectrum disorders and ‘rigidity’. Analysing top variants and genes, we demonstrated a role of the immune-related genes RNF114, CDKN2A, KAZN, SPATA2 and ZNF816A in autistic-like traits. Brain-based genetic expression analyses further linked autistic-like traits to genes involved in immune functioning, and neuronal and synaptic signalling. Overall, our findings highlight the potential of the autistic-like trait–based approach to address the challenges of genetic research in autism spectrum disorders. We provide novel insights showing a potential role of the immune system in specific autism spectrum disorder dimensions.

Greater time in bed and less physical activity associate with poorer cognitive functioning performance in Huntington's disease

Objective: This study aimed to investigate how sleep and physical activity habits related to cognitive functioning, in naturalistic settings, in early Huntington's disease (HD). Method: Forty-two participants with the expanded HD repeat (20 manifest, 22 premanifest) and 29 healthy controls wore Fitbit One sleep and activity monitors for 7 days and 7 nights. They used a smartphone application to complete daily sleep and activity diaries, sleep and mood inventories, and a brief battery of cognitive tests, which were completed on Day 8 of the study. All data were collected in naturalistic home and community settings. Results: Amongst participants with the expanded HD repeat, greater time spent in bed, measured by Fitbit, was associated with poorer accuracy and response speed on a test of visual memory, whereas lower levels of physical activity, measured by Fitbit, were associated with poorer accuracy on a test involving a working memory component. Neither time in bed nor physical activity is associated with a test of psychomotor speed. Groups were mostly similar across a range of Fitbit and self-report measures of sleep and physical activity, although the Manifest-HD group spent more time in bed than the Premanifest-HD and Healthy Control groups and had better self-reported sleep quality and more self-reported time spent sitting than the Healthy Control group and the Premanifest-HD group, respectively. Conclusions: Sleep timing and physical activity relate to cognitive functioning in HD and may be important targets for management in behavioral intervention studies aimed at improving cognition in HD. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Genetic influences on hub connectivity of the human connectome

Brain network hubs are both highly connected and highly inter-connected, forming a critical communication backbone for coherent neural dynamics. The mechanisms driving this organization are poorly understood. Using diffusion-weighted magnetic resonance imaging in twins, we identify a major role for genes, showing that they preferentially influence connectivity strength between network hubs of the human connectome. Using transcriptomic atlas data, we show that connected hubs demonstrate tight coupling of transcriptional activity related to metabolic and cytoarchitectonic similarity. Finally, comparing over thirteen generative models of network growth, we show that purely stochastic processes cannot explain the precise wiring patterns of hubs, and that model performance can be improved by incorporating genetic constraints. Our findings indicate that genes play a strong and preferential role in shaping the functionally valuable, metabolically costly connections between connectome hubs.

A neural index of inefficient evidence accumulation in dyslexia underlying slow perceptual decision making

Visual processing deficits have been widely reported in developmental dyslexia however the locus of cognitive dysfunction remains unclear. Here, we examined the neural correlates of perceptual decision-making using a dot-motion task and electroencephalography (EEG) and investigated whether presenting deficits were unique to children with dyslexia or if they were also evident in other, typically developing children with equally immature reading systems. Sixty-eight children participated: 32 with dyslexia (DD; 16 females); 21 age-matched controls (AM; 11 females) and 15 reading-matched controls (RM; 9 females). All participants completed a bilaterally presented random-dot-motion task while EEG was recorded. Neural signatures of low level sensory processing (steady state visual evoked potentials; SSVEPs), pre-target attentional bias (posterior α power), attentional orienting (N2), evidence accumulation (centro-parietal positive decision signal; CPP) and execution of a motor response (β) were obtained to dissect the temporal sequence of perceptual decision-making. Reading profile provided a score of relative lexical and sublexical skills for each participant. Although all groups performed comparably in terms of task accuracy and false alarm rate, the DD group were slower and demonstrated an earlier peak latency, reduced slope and lower amplitude of the CPP compared with both AM and RM controls. Reading profile was found to moderate the relationship between word reading ability, reaction time as well as CPP indices showing that lexical dyslexics responded more slowly and had a shallower slope, reduced amplitude and earlier latency of CPP waveforms than sublexical dyslexics. These findings suggest that children with dyslexia, particularly those with relatively poorer lexical abilities, have a reduced rate and peak of evidence accumulation as denoted by CPP markers yet remain slow in their overt response. This is in keeping with hypotheses that children with dyslexia have impairment in effectively sampling and processing evidence about visual motion stimuli.

The Hunger Games: Homeostatic State-Dependent Fluctuations in Disinhibition Measured with a Novel Gamified Test Battery

Food homeostatic states (hunger and satiety) influence the cognitive systems regulating impulsive responses, but the direction and specific mechanisms involved in this effect remain elusive. We examined how fasting, and satiety, affect cognitive mechanisms underpinning disinhibition using a novel framework and a gamified test-battery. Thirty-four participants completed the test-battery measuring three cognitive facets of disinhibition: attentional control, information gathering and monitoring of feedback, across two experimental sessions: one after overnight fasting and another after a standardised meal. Homeostatic state was assessed using subjective self-reports and biological markers (i.e., blood-derived liver-expressed antimicrobial protein 2 (LEAP-2), insulin and leptin). We found that participants who experienced greater subjective hunger during the satiety session were more impulsive in the information gathering task; results were not confounded by changes in mood or anxiety. Homeostatic state did not significantly influence disinhibition mechanisms linked to attentional control or feedback monitoring. However, we found a significant interaction between homeostatic state and LEAP-2 on attentional control, with higher LEAP-2 associated with faster reaction times in the fasted condition only. Our findings indicate lingering hunger after eating increases impulsive behaviour via reduced information gathering. These findings identify a novel mechanism that may underpin the tendency to overeat and/or engage in broader impulsive behaviours.

Cognition, ADHD Symptoms, and Functional Impairment in Children and Adolescents With Neurofibromatosis Type 1

Objective: We examined the contribution of attention and executive cognitive processes to ADHD symptomatology in NF1, as well as the relationships between cognition and ADHD symptoms with functional outcomes. Methods: The study sample consisted of 141 children and adolescents with NF1. Children were administered neuropsychological tests that assessed attention and executive function, from which latent cognitive variables were derived. ADHD symptomatology, adaptive skills, and quality of life (QoL) were assessed using parent-rated questionnaires. Path analyses were conducted to test relationships among cognitive functioning, ADHD symptomatology, and functional outcomes. Results: Significant deficits were observed on all outcome variables. Cognitive variables did not predict ADHD symptomatology. Neither did they predict functional outcomes. However, elevated ADHD symptomatology significantly predicted functional outcomes. Conclusion: Irrespective of cognitive deficits, elevated ADHD symptoms in children with NF1 negatively impact daily functioning and emphasize the importance of interventions aimed at minimizing ADHD symptoms in NF1.