Task-related default mode network modulation and inhibitory control in ADHD: effects of motivation and methylphenidate

The Impact of Motivation on Sustained Attention in Very Preterm and Term-born Children: An ERP Study

OBJECTIVE

To compare the effect of motivational features on sustained attention in children born very preterm and at term.

METHOD

EEG was recorded while 34 8-to-11-year-old children born very preterm and 34 term-born peers completed two variants of a cued continuous performance task (CPT-AX); a standard CPT-AX with basic shape stimuli, and structurally similar motivating variant, with a storyline, familiar characters, and feedback.

RESULTS

Higher hit rates, quicker response times and larger event-related potential (ERP) amplitudes were observed during the motivating, compared with the standard, task. Although groups did not differ in task performance, between-task differences in ERPs associated with orienting were larger in term-born than very preterm children.

CONCLUSION

The findings add to previous evidence of disruption to the brain networks that support salience detection and selective attention in children born preterm. Manipulations that increase intrinsic motivation can promote sustained attention in both term-born and very preterm children.

Restorative Effects of Daytime Naps on Inhibitory Control: A Neuroimaging Study Following Sleep Deprivation

Background

Sleep deprivation is known to impair cognitive performance, particularly inhibitory control, which is crucial for goal-directed behavior. While extended recovery sleep is the ideal solution, the fast-paced demands of modern life often make this impractical. Brief daytime naps have emerged as a potential countermeasure, but the neural mechanisms underlying their restorative effects remain underexplored.

Objective

This study aimed to investigate the effects of a 30-minute daytime nap on brain activation patterns and cognitive performance following sleep deprivation. We used task-based functional magnetic resonance imaging (fMRI) to examine how naps modulate brain regions involved in inhibitory control.

Methods

Forty-five participants completed a dual-choice Oddball task under three conditions: Resting Wakefulness (RW), Sleep Deprivation (SD), and Post-Nap (Nap). Reaction times (RT), accuracy, and brain activation patterns were measured and analyzed across these states. Task-related brain activation was examined using fMRI, focusing on regions involved in the frontoparietal and default mode networks (DMN).

Results

Sleep deprivation significantly impaired inhibitory control, as reflected by slower RTs and reduced accuracy. A 30-minute nap partially restored cognitive performance, with RTs and accuracy showing intermediate improvement between RW and SD. Neuroimaging data revealed that the nap restored positive activation in the prefrontal cortex, occipital lobes, and middle frontal regions, which had been significantly reduced during SD. Furthermore, the nap enhanced negative activation in the middle temporal gyrus and cingulate gyrus, regions associated with the DMN, reducing cognitive interference from irrelevant stimuli.

Conclusion

Daytime naps significantly mitigate the cognitive deficits induced by SD through two primary mechanisms: (1) enhancing positive activation in task-relevant brain regions and (2) increasing negative activation in areas involved in the DMN. These findings provide novel insights into the neural basis of nap-induced cognitive recovery, underscoring the value of naps as an effective intervention to restore inhibitory control following SD.

How does attention deficit/hyperactivity disorder affect driving behavior components? Baseline findings from Persian traffic cohort

PURPOSE

Attention-deficit/hyperactivity disorder (ADHD) increases the risk of road traffic injuries through various mechanisms including higher risky driving behaviors. Therefore, drivers with ADHD are shown to be more prone to road traffic injuries. This study was conducted in a community-based sample of drivers to determine how ADHD affects driving behavior components.

METHODS

At the cross-sectional phase of a national population-based cohort, a representative sample of 1769 drivers were enrolled. Manchester driving behavior questionnaire and Conners' adult ADHD rating scales were used to assess driving behavior and ADHD symptom scores, respectively. Data were analyzed using Stata version 17. Multiple linear regression was used to investigate the association of driving behavior with ADHD while adjusting for the potential confounding role of age, sex, marital status, educational level, driving history, etc. RESULTS: According to the results, the normalized driving behavior score of drivers with ADHD was 4.64 points higher than drivers without ADHD. Having an academic compared to school education, increased the driving behavior score by 1.73 points. The normalized driving behavior score of drivers under 18 years of age was 6.27 points higher than drivers aged 31 - 45 years. The score of the aggressive violation subscale of drivers with ADHD was 7.33 points higher than drivers without ADHD compared to an increment of a range of 4.50-4.82 points for other driving subscales. The score of the ordinary violation subscale of female drivers was 2.23 points lower than that of male drivers. No significant relationship was found between sex and other subscales of driving.

CONCLUSION

Drivers with ADHD who are in adolescence or early adulthood exhibit more dangerous and aggressive driving behaviors than those who are older. Implementing training interventions to increase awareness of drivers with ADHD, their families, and psychologists regarding the effects of ADHD on driving is an essential step in preventing motor vehicle crashes among drivers with ADHD.

Neural Markers of Treatment Response in Pediatric Anxiety and PTSD

Pediatric anxiety disorders and post-traumatic stress disorder (PTSD) are associated with elevated threat sensitivity and impaired emotion regulation, accompanied by dysfunction in the neural circuits involved in these processes. Despite established treatments like cognitive behavioral therapy (CBT) and selective serotonin reuptake inhibitors, many children do not achieve remission, underscoring the importance of understanding the neurobiological underpinnings of these disorders. This review synthesizes current research on the neural predictors of treatment response and the neurofunctional changes associated with treatment in pediatric anxiety and PTSD during threat and reward processing. Several key findings emerged. First, enhanced threat/safety discrimination in the amygdala predicted better outcomes of pediatric anxiety and PTSD treatments. Second, differences in pretreatment activation within the lateral prefrontal and dorsal anterior cingulate cortices predicted treatment response, likely reflecting baseline executive control differences. Third, post-CBT decreases in activation in default mode, visuo-attentional, and sensorimotor areas may support treatment-related increases in task engagement. Finally, functional connectivity between the amygdala and other limbic, prefrontal, and default mode network nodes predicts treatment response in anxiety and PTSD, highlighting its potential as a biomarker for therapeutic efficacy. Understanding these neurofunctional markers could lead to more targeted interventions, optimizing treatment planning and potentially leading to the development of "pretreatment" strategies to enhance the efficacy of existing treatments. This review highlights the necessity for future research to establish more direct links between neuroimaging findings and clinical outcomes to facilitate the translation of these findings into clinical practice.

Neurobiology of attention-deficit hyperactivity disorder: historical challenges and emerging frontiers

Extensive investigations spanning multiple levels of inquiry, from genetic to behavioural studies, have sought to unravel the mechanistic foundations of attention-deficit hyperactivity disorder (ADHD), with the aspiration of developing efficacious treatments for this condition. Despite these efforts, the pathogenesis of ADHD remains elusive. In this Review, we reflect on what has been learned about ADHD while also providing a framework that may serve as a roadmap for future investigations. We emphasize that ADHD is a highly heterogeneous disorder with multiple aetiologies that necessitates a multifactorial dimensional phenotype, rather than a fixed dichotomous conceptualization. We highlight new findings that suggest a more brain-wide, 'global' view of the disorder, rather than the traditional localizationist framework, which asserts that a limited set of brain regions or networks underlie ADHD. Last, we underscore how underpowered studies that have aimed to associate neurobiology with ADHD phenotypes have long precluded the field from making progress. However, a new age of ADHD research with refined phenotypes, advanced methods, creative study designs and adequately powered investigations is beginning to put the field on a good footing. Indeed, the field is at a promising juncture to advance the neurobiological understanding of ADHD and fulfil the promise of clinical utility.

Interference of default mode on attention networks in adults with attention-deficit/hyperactivity disorder and its association with genetic variants and treatment outcomes

AIMS

Altered brain functional connectivity has been proposed as the neurobiological underpinnings of attention-deficit/hyperactivity disorder (ADHD), and the default mode interference hypothesis is one of the most popular neuropsychological models. Here, we explored whether this hypothesis is supported in adults with ADHD and the association with high-risk genetic variants and treatment outcomes.

METHODS

Voxel-based whole-brain connectome analysis was conducted on resting-state functional MRI data from 84 adults with ADHD and 89 healthy controls to identify functional connectivity substrates corresponding to ADHD-related alterations. The candidate genetic variants and 12-week cognitive behavioral therapy data were leveraged from the same population to assess these associations.

RESULTS

We detected breakdowns of functional connectivity in the precuneus and left middle temporal gyrus in adults with ADHD, with exact contributions from decreased connectivity within the default mode, dorsal and ventral attention networks, as well as increased connectivity among them with the middle temporal gyrus serving as a crucial 'bridge'. Additionally, significant associations between the altered functional connectivity and genetic variants in both MAOA and MAOB were detected. Treatment restored brain function, with the amelioration of connectivity of the middle temporal gyrus, accompanied by improvements in ADHD core symptoms.

CONCLUSIONS

These findings support the interference of default mode on attention in adults with ADHD and its association with genetic risk variants and clinical management, providing insights into the underlying pathogenesis of ADHD and potential biomarkers for treatment evaluation.

Attention-deficit/hyperactivity disorder in pregnancy and the postpartum period

Attention-deficit/hyperactivity disorder is a childhood-onset neurodevelopmental disorder that frequently persists into adulthood with 3% of adult women having a diagnosis of attention-deficit/hyperactivity disorder. Many women are diagnosed and treated during their reproductive years, which leads to management implications during pregnancy and the postpartum period. We know from clinical practice that attention-deficit/hyperactivity disorder symptoms frequently become challenging to manage during the perinatal period and require additional support and attention. There is often uncertainty among healthcare providers about the management of attention-deficit/hyperactivity disorder in the perinatal period, particularly the safety of pharmacotherapy for the developing fetus. This guideline is focused on best practices in managing attention-deficit/hyperactivity disorder in the perinatal period. We recommend (1) mitigating the risks associated with attention-deficit/hyperactivity disorder that worsen during the perinatal period via individualized treatment planning; (2) providing psychoeducation, self-management strategies or coaching, and psychotherapies; and, for those with moderate or severe attention-deficit/hyperactivity disorder, (3) considering pharmacotherapy for attention-deficit/hyperactivity disorder, which largely has reassuring safety data. Specifically, providers should work collaboratively with patients and their support networks to balance the risks of perinatal attention-deficit/hyperactivity disorder medication with the risks of inadequately treated attention-deficit/hyperactivity disorder during pregnancy. The risks and impacts of attention-deficit/hyperactivity disorder in pregnancy can be successfully managed through preconception counselling and appropriate perinatal planning, management, and support.

A comparison of visual attention to pictures in the Autism Diagnostic Observation Schedule in children and adolescents with ADHD and/or autism

Background

Attention-Deficit/Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD) are neurodevelopmental conditions which frequently co-occur. The Autism Diagnostic Observation Schedule (ADOS) is commonly used to aid with diagnostic assessment of ASD but was not originally designed for use in those with comorbid ADHD. Visual attention to social stimuli has been often studied in ASD using eye-tracking, to obtain quantitative indices of how attention is deployed to different parts of a social image/scene. As the ADOS includes tasks that rely on attending to and processing images of social scenes, these measures of visual attention could provide useful additional objective measurement alongside ADOS scores to enhance the characterisation of autistic symptoms in those with ADHD.

Methods

Children with ASD, comorbid ASD and ADHD, ADHD and Neurotypical (NT) controls were recruited (n=84). Visual attention was measured using eye-tracking during free viewing of social scenes selected from the ADOS. The full ADOS was then administered. Stimulant medication was temporarily withdrawn during this assessment. Research diagnoses were based on the Development and Wellbeing Assessment (DAWBA), ADOS, Social Communication Questionnaire (SCQ, a measure of ASD severity) and Conners' Rating Scales (CRS-3, a measure of ADHD severity) following clinical consensus.

Results

Using factorial ANOVAs to model ADHD, Autism and their interaction, we found that fixation duration to faces was reduced in those with ASD (ASD and ASD+ADHD) compared to those without ASD (ADHD and NT). Reduced visual attention to faces in the whole sample was associated with Autism symptom severity (SCQ subscale scores) but not ADHD symptom severity (CRS-3 scores).

Discussion

Our findings provide preliminary evidence in support of implementing visual attention measurement during assessment of ASD in the context of comorbidity with ADHD. For example, if a child with ADHD was found to reduce attention to faces in ADOS pictures this may suggest additive difficulties on the autism spectrum. Replication across a larger sample would be informative. This work has future potential in the clinic to help with complex cases, including those with co-occurring ADHD and ASD.

Creative tempo: Spatiotemporal dynamics of the default mode network in improvisational musicians

The intrinsic dynamics of human brain activity display a recurring pattern of anti-correlated activity between the default mode network (DMN), associated with internal processing and mentation, and task positive regions, associated with externally directed attention. In human functional magnetic resonance imaging (fMRI) data, this anti-correlated pattern is detectable on the infraslow timescale (<0.1 Hz) as a quasi-periodic pattern (QPP). While the DMN is implicated in creativity and musicality in traditional time-averaged functional connectivity studies, no one has yet explored how creative training may alter dynamic spatiotemporal patterns involving the DMN such as QPPs. In the present study, we compare the outputs of two QPP detection approaches, sliding window algorithm and complex principal components analysis (cPCA). We apply both methods to an existing dataset of musicians captured with resting state fMRI, grouped as either classical, improvisational, or minimally trained non-musicians. The original time-averaged functional connectivity (FC) analysis of this dataset used improvisation as a proxy for creative thinking and found that the DMN and visual networks (VIS) display higher connectivity in improvisational musicians. We expand upon this dataset's original study and find that QPP analysis detects convergent results at the group level with both methods. In improvisational musicians, dynamic functional correlation in the group-averaged QPP was found to be increased between the DMN-VIS and DMN-FPN for both the QPP algorithm and complex principal components analysis (cPCA) methods. Additionally, we found an unexpected increase in FC in the group-averaged QPP between the dorsal attention network and amygdala in improvisational musicians; this result was not reported in the original seed-based study of this dataset. The current study represents a novel application of two dynamic FC detection methods with results that replicate and expand upon previous seed-based FC findings. The results show the robustness of both the QPP phenomenon and its detection methods. This study also demonstrates the value of dynamic FC methods in reproducing seed-based findings and their promise in detecting group-wise or individual differences that may be missed by traditional seed-based resting state fMRI studies.

Translating Decades of Neuroscience Research into Diagnostic and Treatment Biomarkers for ADHD

In this chapter, we review scientific findings that form the basis for neuroimaging and neurophysiological biomarkers for ADHD diagnosis and treatment. We then highlight the different challenges in translating mechanistic findings into biomarkers for ADHD diagnosis and treatment. Population heterogeneity is a primary barrier for identifying biomarkers of ADHD diagnosis, which requires shifts toward dimensional approaches that identify clinically useful subgroups or prospective biomarkers that can identify trajectories of illness, function, or treatment response. Methodological limitations, including emphasis on group level analyses of treatment effects in small sample sizes, are the primary barriers to biomarker discovery in ADHD treatment. Modifications to clinical trials, including shifting towards testing biomarkers of a priori prediction of functionally related brain targets, treatment response, and side effects, are suggested. Finally, future directions for biomarker work are discussed.

A common spectrum underlying brain disorders across lifespan revealed by deep learning on brain networks

Brain disorders in the early and late life of humans potentially share pathological alterations in brain functions. However, the key neuroimaging evidence remains unrevealed for elucidating such commonness and the relationships among these disorders. To explore this puzzle, we build a restricted single-branch deep learning model, using multi-site functional magnetic resonance imaging data (N = 4,410, 6 sites), for classifying 5 different early- and late-life brain disorders from healthy controls (cognitively unimpaired). Our model achieves 62.6 ± 1.9% overall classification accuracy and thus supports us in detecting a set of commonly affected functional subnetworks, including default mode, executive control, visual, and limbic networks. In the deep-layer representation of data, we observe young and aging patients with disorders are continuously distributed, which is in line with the clinical concept of the "spectrum of disorders." The relationships among brain disorders from the revealed spectrum promote the understanding of disorder comorbidities and time associations in the lifespan.

The Utility of Methylphenidate for Fatigue in Long-Term Neurological Conditions: A Meta-analytical Review

OBJECTIVE

Fatigue is a chronic and debilitating symptom of many long-term neurological conditions (LTNCs). Although methylphenidate provides some promise in alleviating fatigue in other clinical groups, little work has explored its potential utility within LTNCs. The current systematic review and meta-analysis evaluates the utility of methylphenidate for symptoms of fatigue in LTNCs.

METHODS

Five databases (PsycINFO, MEDLINE, Embase, Scopus, and Cochrane Library) were searched for relevant articles from their inception to February 2022. A purpose-developed evaluation tool was used to assess each study's research quality (QuEST:F).

RESULTS

Of the 1698 articles identified, 11 articles were included within this review (n = 370). Meta-analytical findings reported an overall significant benefit of methylphenidate for symptoms of fatigue across a mixed neurological sample ( g = -0.44; 95% confidence interval, -0.77 to -0.11). Subgroup analyses identified a significantly greater benefit ( P < 0.001) of methylphenidate for fatigue in LTNCs with static pathogenic trajectories (eg, traumatic brain injury) (number needed to treat = 2.5) compared with progressive conditions (eg, multiple sclerosis) (number needed to treat = 40.2).

CONCLUSIONS

Methylphenidate may pose an effective intervention for the treatment of fatigue in a number of LTNCs. Nonetheless, given the quality of the current evidence base, there exists a clear need for further robust assessment of the utility of methylphenidate-with a focus on subgroup-specific variability.

Neurogenetic mechanisms of risk for ADHD: Examining associations of polygenic scores and brain volumes in a population cohort

BACKGROUND

ADHD polygenic scores (PGSs) have been previously shown to predict ADHD outcomes in several studies. However, ADHD PGSs are typically correlated with ADHD but not necessarily reflective of causal mechanisms. More research is needed to elucidate the neurobiological mechanisms underlying ADHD. We leveraged functional annotation information into an ADHD PGS to (1) improve the prediction performance over a non-annotated ADHD PGS and (2) test whether volumetric variation in brain regions putatively associated with ADHD mediate the association between PGSs and ADHD outcomes.

METHODS

Data were from the Philadelphia Neurodevelopmental Cohort (N = 555). Multiple mediation models were tested to examine the indirect effects of two ADHD PGSs-one using a traditional computation involving clumping and thresholding and another using a functionally annotated approach (i.e., AnnoPred)-on ADHD inattention (IA) and hyperactivity-impulsivity (HI) symptoms, via gray matter volumes in the cingulate gyrus, angular gyrus, caudate, dorsolateral prefrontal cortex (DLPFC), and inferior temporal lobe.

RESULTS

A direct effect was detected between the AnnoPred ADHD PGS and IA symptoms in adolescents. No indirect effects via brain volumes were detected for either IA or HI symptoms. However, both ADHD PGSs were negatively associated with the DLPFC.

CONCLUSIONS

The AnnoPred ADHD PGS was a more developmentally specific predictor of adolescent IA symptoms compared to the traditional ADHD PGS. However, brain volumes did not mediate the effects of either a traditional or AnnoPred ADHD PGS on ADHD symptoms, suggesting that we may still be underpowered in clarifying brain-based biomarkers for ADHD using genetic measures.

Methylphenidate as a treatment option for substance use disorder: a transdiagnostic perspective

A transition in viewing mental disorders from conditions defined as a set of unique characteristics to one of the quantitative variations on a collection of dimensions allows overlap between disorders. The overlap can be utilized to extend to treatment approaches. Here, we consider the overlap between attention-deficit/hyperactivity disorder and substance use disorder to probe the suitability to use methylphenidate as a treatment for substance use disorder. Both disorders are characterized by maladaptive goal-directed behavior, impaired cognitive control, hyperactive phasic dopaminergic neurotransmission in the striatum, prefrontal hypoactivation, and reduced frontal cortex gray matter volume/density. In addition, methylphenidate has been shown to improve cognitive control and normalize associated brain activation in substance use disorder patients and clinical trials have found methylphenidate to improve clinical outcomes. Despite the theoretical basis and promising, but preliminary, outcomes, many questions remain unanswered. Most prominent is whether all patients who are addicted to different substances may equally profit from methylphenidate treatment.

Altered functional connectivity between cortical networks associated with inhibitory control in trauma-exposed females

Post-traumatic stress disorder (PTSD) is associated with impaired inhibitory control and alterations in large-scale brain network connectivity. However, few studies to date have examined the construct of inhibitory control as it relates to resting-state functional connectivity (rsFC) in a population with PTSD or trauma-exposure. The present study investigated the relationship between impaired inhibitory control and rsFC within the default mode network (DMN), central executive network (CEN), and salience network (SN) in a sample of females exposed to interpersonal trauma with and without PTSD (n = 67). Participants completed a classic Color-Word Stroop task as a measure of inhibitory control and two resting-state fMRI scans. We conducted voxelwise rsFC analyses with seed regions in the DMN, CEN, and SN and voxelwise linear regression analyses to examine the relationship between inhibitory control and rsFC of these networks across the sample. Better Stroop performance was negatively associated with total self-reported PTSD symptoms. An analysis of PTSD symptom clusters indicated that better Stroop performance was also associated with re-experiencing and hyperarousal symptoms, but not avoidance PTSD symptoms. Decreased coupling between the CEN and the DMN was associated with better inhibitory control in this sample of trauma-exposed females. These findings lend support to the hypothesis that efficient switching between these networks may contribute to better performance on cognitive and attentional tasks in trauma-exposed individuals.

The association between different sources of distraction and symptoms of attention deficit hyperactivity disorder

Introduction

Adults with Attention-Deficit/Hyperactivity Disorder (ADHD) are generally distractible. Yet, the precise relationship between ADHD and distractibility remains under-specified in two respects. First, different sources of distraction, such as background noise or mind wandering, may not be equally associated with ADHD. Second, ADHD itself comprises a variety of symptoms that show considerable heterogeneity and it is unclear which ADHD symptoms are associated with which type of distraction.

Methods

The current study addresses these questions using one clinically evaluated sample (N = 69) and two large non-clinically evaluated samples (N = 569, N = 651). In all samples, participants completed questionnaires about their susceptibility to external distraction, unwanted intrusive thoughts, spontaneous mind-wandering and ADHD symptomatology.

Results

Traditional regression and novel network analyses revealed an overwhelming contribution of spontaneous mind-wandering in explaining ADHD symptoms, although external distraction and unwanted intrusive thoughts were also associated with a small number of ADHD symptoms.

Discussion

Findings support a growing body of literature linking spontaneous mind-wandering and ADHD, and they highlight the heterogeneity in the association between ADHD symptoms and different sources of distraction.

Characterizing different cognitive and neurobiological profiles in a community sample of children using a non-parametric approach: An fMRI study

Executive Functions (EF) is an umbrella term for a set of mental processes geared towards goal-directed behavior supporting academic skills such as reading abilities. One of the brain's functional networks implicated in EF is the Default Mode Network (DMN). The current study uses measures of inhibitory control, a main sub-function of EF, to create cognitive and neurobiological "inhibitory control profiles" and relate them to reading abilities in a large sample (N = 5055) of adolescents aged 9-10 from the Adolescent Brain Cognitive Development (ABCD) study. Using a Latent Profile Analysis (LPA) approach, data related to inhibitory control was divided into four inhibition classes. For each class, functional connectivity within the DMN was calculated from resting-state data, using a non-parametric algorithm for detecting group similarities. These inhibitory control profiles were then related to reading abilities. The four inhibitory control groups showed significantly different reading abilities, with neurobiologically different DMN segregation profiles for each class versus controls. The current study demonstrates that a community sample of children is not entirely homogeneous and is composed of different subgroups that can be differentiated both behaviorally/cognitively and neurobiologically, by focusing on inhibitory control and the DMN. Educational implications relating these results to reading abilities are noted.

Evidence from "big data" for the default-mode hypothesis of ADHD: a mega-analysis of multiple large samples

We sought to identify resting-state characteristics related to attention deficit/hyperactivity disorder, both as a categorical diagnosis and as a trait feature, using large-scale samples which were processed according to a standardized pipeline. In categorical analyses, we considered 1301 subjects with diagnosed ADHD, contrasted against 1301 unaffected controls (total N = 2602; 1710 males (65.72%); mean age = 10.86 years, sd = 2.05). Cases and controls were 1:1 nearest neighbor matched on in-scanner motion and key demographic variables and drawn from multiple large cohorts. Associations between ADHD-traits and resting-state connectivity were also assessed in a large multi-cohort sample (N = 10,113). ADHD diagnosis was associated with less anticorrelation between the default mode and salience/ventral attention (B = 0.009, t = 3.45, p-FDR = 0.004, d = 0.14, 95% CI = 0.004, 0.014), somatomotor (B = 0.008, t = 3.49, p-FDR = 0.004, d = 0.14, 95% CI = 0.004, 0.013), and dorsal attention networks (B = 0.01, t = 4.28, p-FDR < 0.001, d = 0.17, 95% CI = 0.006, 0.015). These results were robust to sensitivity analyses considering comorbid internalizing problems, externalizing problems and psychostimulant medication. Similar findings were observed when examining ADHD traits, with the largest effect size observed for connectivity between the default mode network and the dorsal attention network (B = 0.0006, t = 5.57, p-FDR < 0.001, partial-r = 0.06, 95% CI = 0.0004, 0.0008). We report significant ADHD-related differences in interactions between the default mode network and task-positive networks, in line with default mode interference models of ADHD. Effect sizes (Cohen's d and partial-r, estimated from the mega-analytic models) were small, indicating subtle group differences. The overlap between the affected brain networks in the clinical and general population samples supports the notion of brain phenotypes operating along an ADHD continuum.

Potential mechanisms underlying the accelerated cognitive decline in people with chronic low back pain: A scoping review

A growing body of evidence has shown that people with chronic low back pain (CLBP) demonstrate significantly greater declines in multiple cognitive domains than people who do not have CLBP. Given the high prevalence of CLBP in the ever-growing aging population that may be more vulnerable to cognitive decline, it is important to understand the mechanisms underlying the accelerated cognitive decline observed in this population, so that proper preventive or treatment approaches can be developed and implemented. The current scoping review summarizes what is known regarding the potential mechanisms underlying suboptimal cognitive performance and cognitive decline in people with CLBP and discusses future research directions. Five potential mechanisms were identified based on the findings from 34 included studies: (1) altered activity in the cortex and neural networks; (2) grey matter atrophy; (3) microglial activation and neuroinflammation; (4) comorbidities associated with CLBP; and (5) gut microbiota dysbiosis. Future studies should deepen the understanding of mechanisms underlying this association so that proper prevention and treatment strategies can be developed.

Treatment biomarkers for ADHD: Taking stock and moving forward

The development of treatment biomarkers for psychiatric disorders has been challenging, particularly for heterogeneous neurodevelopmental conditions such as attention-deficit/hyperactivity disorder (ADHD). Promising findings are also rarely translated into clinical practice, especially with regard to treatment decisions and development of novel treatments. Despite this slow progress, the available neuroimaging, electrophysiological (EEG) and genetic literature provides a solid foundation for biomarker discovery. This article gives an updated review of promising treatment biomarkers for ADHD which may enhance personalized medicine and novel treatment development. The available literature points to promising pre-treatment profiles predicting efficacy of various pharmacological and non-pharmacological treatments for ADHD. These candidate predictive biomarkers, particularly those based on low-cost and non-invasive EEG assessments, show promise for the future stratification of patients to specific treatments. Studies with repeated biomarker assessments further show that different treatments produce distinct changes in brain profiles, which track treatment-related clinical improvements. These candidate monitoring/response biomarkers may aid future monitoring of treatment effects and point to mechanistic targets for novel treatments, such as neurotherapies. Nevertheless, existing research does not support any immediate clinical applications of treatment biomarkers for ADHD. Key barriers are the paucity of replications and external validations, the use of small and homogeneous samples of predominantly White children, and practical limitations, including the cost and technical requirements of biomarker assessments and their unknown feasibility and acceptability for people with ADHD. We conclude with a discussion of future directions and methodological changes to promote clinical translation and enhance personalized treatment decisions for diverse groups of individuals with ADHD.

Sex differences in neural correlates of common psychopathological symptoms in early adolescence

BACKGROUND

Sex-related differences in psychopathology are known phenomena, with externalizing and internalizing symptoms typically more common in boys and girls, respectively. However, the neural correlates of these sex-by-psychopathology interactions are underinvestigated, particularly in adolescence.

METHODS

Participants were 14 years of age and part of the IMAGEN study, a large (N = 1526) community-based sample. To test for sex-by-psychopathology interactions in structural grey matter volume (GMV), we used whole-brain, voxel-wise neuroimaging analyses based on robust non-parametric methods. Psychopathological symptom data were derived from the Strengths and Difficulties Questionnaire (SDQ).

RESULTS

We found a sex-by-hyperactivity/inattention interaction in four brain clusters: right temporoparietal-opercular region (p < 0.01, Cohen's d = -0.24), bilateral anterior and mid-cingulum (p < 0.05, Cohen's d = -0.18), right cerebellum and fusiform (p < 0.05, Cohen's d = -0.20) and left frontal superior and middle gyri (p < 0.05, Cohen's d = -0.26). Higher symptoms of hyperactivity/inattention were associated with lower GMV in all four brain clusters in boys, and with higher GMV in the temporoparietal-opercular and cerebellar-fusiform clusters in girls.

CONCLUSIONS

Using a large, sex-balanced and community-based sample, our study lends support to the idea that externalizing symptoms of hyperactivity/inattention may be associated with different neural structures in male and female adolescents. The brain regions we report have been associated with a myriad of important cognitive functions, in particular, attention, cognitive and motor control, and timing, that are potentially relevant to understand the behavioural manifestations of hyperactive and inattentive symptoms. This study highlights the importance of considering sex in our efforts to uncover mechanisms underlying psychopathology during adolescence.

Cognitive enhancement: Effects of methylphenidate, modafinil, and caffeine on latent memory and resting state functional connectivity in healthy adults

Stimulants like methylphenidate, modafinil, and caffeine have repeatedly shown to enhance cognitive processes such as attention and memory. However, brain-functional mechanisms underlying such cognitive enhancing effects of stimulants are still poorly characterized. Here, we utilized behavioral and resting-state fMRI data from a double-blind randomized placebocontrolled study of methylphenidate, modafinil, and caffeine in 48 healthy male adults. The results show that performance in different memory tasks is enhanced, and functional connectivity (FC) specifically between the frontoparietal network (FPN) and default mode network (DMN) is modulated by the stimulants in comparison to placebo. Decreased negative connectivity between right prefrontal and medial parietal but also between medial temporal lobe and visual brain regions predicted stimulant-induced latent memory enhancement. We discuss dopamine's role in attention and memory as well as its ability to modulate FC between large-scale neural networks (e.g., FPN and DMN) as a potential cognitive enhancement mechanism.

Obesity and acute stress modulate appetite and neural responses in food word reactivity task

Obesity can result from excess intake in response to environmental food cues, and stress can drive greater intake and body weight. We used a novel fMRI task to explore how obesity and stress influenced appetitive responses to relatively minimal food cues (words representing food items, presented similarly to a chalkboard menu). Twenty-nine adults (16F, 13M), 17 of whom had obesity and 12 of whom were lean, completed two fMRI scans, one following a combined social and physiological stressor and the other following a control task. A food word reactivity task assessed subjective food approach (wanting) as well as food avoidant (restraint) responses, along with neural responses, to words denoting high energy-density (ED) foods, low-ED foods, and non-foods. A multi-item ad-libitum meal followed each scan. The obese and lean groups demonstrated differences as well as similarities in activation of appetitive and attention/self-regulation systems in response to food vs. non-food, and to high-ED vs. low-ED food words. Patterns of activation were largely similar across stress and non-stress conditions, with some evidence for differences between conditions within both obese and lean groups. The obese group ate more than the lean group in both conditions. Our results suggest that neural responses to minimal food cues in stressed and non-stressed states may contribute to excess consumption and adiposity.

From Structural Disparities to Neuropharmacology: A Review of Adult Attention-Deficit/Hyperactivity Disorder Medication Treatment

Adult attention-deficit/hyperactivity disorder (ADHD) is an early-onset disorder with many functional impairments and psychiatric comorbidities. Although no treatment fully mitigates impairments associated with ADHD, effective management is possible with pharmacologic and nonpharmacologic treatments. The etiology and pathophysiology of ADHD are remarkably complex and the disorder is continuously distributed in the population. While these findings have been well documented in studies with predominantly white samples, ADHD may affect racial and ethnic minorities differentially, given diagnostic and treatment disparities. This review provides an updated overview of the epidemiology, etiology, neurobiology, and neuropharmacology of ADHD, addressing racial and ethnic disparities whereby data are available.

Altered large-scale brain network interactions associated with HIV infection and error processing

Altered activity within and between large-scale brain networks has been implicated across various neuropsychiatric conditions. However, patterns of network dysregulation associated with human immunodeficiency virus (HIV), and further impacted by cannabis (CB) use, remain to be delineated. We examined the impact of HIV and CB on resting-state functional connectivity (rsFC) between brain networks and associations with error awareness and error-related network responsivity. Participants (N = 106), stratified into four groups (HIV+/CB+, HIV+/CB-, HIV-/CB+, HIV-/CB-), underwent fMRI scanning while completing a resting-state scan and a modified Go/NoGo paradigm assessing brain responsivity to errors and explicit error awareness. We examined separate and interactive effects of HIV and CB on resource allocation indexes (RAIs), a measure quantifying rsFC strength between the default mode network (DMN), central executive network (CEN), and salience network (SN). We observed reduced RAIs among HIV+ (vs. HIV-) participants, which was driven by increased SN-DMN rsFC. No group differences were detected for SN-CEN rsFC. Increased SN-DMN rsFC correlated with diminished error awareness, but not with error-related network responsivity. These outcomes highlight altered network interactions among participants with HIV and suggest such rsFC dysregulation may persist during task performance, reflecting an inability to disengage irrelevant mental operations, ultimately hindering error processing.

Intrinsic Functional Connectivity in the Default Mode Network Differentiates the Combined and Inattentive Attention Deficit Hyperactivity Disorder Types

Neuroimaging studies have revealed neurobiological differences in ADHD, particularly studies examining connectivity disruption and anatomical network organization. However, the underlying pathophysiology of ADHD types remains elusive as it is unclear whether dysfunctional network connections characterize the underlying clinical symptoms distinguishing ADHD types. Here, we investigated intrinsic functional network connectivity to identify neural signatures that differentiate the combined (ADHD-C) and inattentive (ADHD-I) presentation types. Applying network-based statistical (NBS) and graph theoretical analysis to task-derived intrinsic connectivity data from completed fMRI scans, we evaluated default mode network (DMN) and whole-brain functional network topology in a cohort of 34 ADHD participants (aged 8-17 years) defined using DSM-IV criteria as predominantly inattentive (ADHD-I) type (n = 15) or combined (ADHD-C) type (n = 19), and 39 age and gender-matched typically developing controls. ADHD-C were characterized from ADHD-I by reduced network connectivity differences within the DMN. Additionally, reduced connectivity within the DMN was negatively associated with ADHD-RS hyperactivity-impulsivity subscale score. Compared with controls, ADHD-C but not ADHD-I differed by reduced connectivity within the DMN; inter-network connectivity between the DMN and somatomotor networks; the DMN and limbic networks; and between the somatomotor and cingulo-frontoparietal, with ventral attention and dorsal attention networks. However, graph-theoretical measures did not significantly differ between groups. These findings provide insight into the intrinsic networks underlying phenotypic differences between ADHD types. Furthermore, these intrinsic functional connectomic signatures support neurobiological differences underlying clinical variations in ADHD presentations, specifically reduced within and between functional connectivity of the DMN in the ADHD-C type.

Effects of Methylphenidate on Somatic Symptoms and Brain Functional Connectivity in Adolescents with Attention Deficit Hyperactivity Disorder: A Pilot Study

Objective

This study aimed to evaluate whether somatic symptoms in adolescents with attention deficit hyperactivity disorder (ADHD) are associated with a dissociative pattern of functional connectivity (FC) within the default mode network (DMN) and whether methylphenidate administration can improve clinical and somatic symptoms. We also evaluated whether the improvement of somatic symptoms is associated with increased FC within the DMN in response to methylphenidate treatment.

Methods

Fifteen male adolescents with somatic symptoms of ADHD and 15 male adolescents with ADHD without somatic symptoms were included. At baseline and after 6 months of methylphenidate treatment, all adolescents were asked to complete questionnaires for the Korean version of the Dupaul’s ADHD rating scale, the symptom checklist-90- revised-somatization subscales, the Beck Depression Inventory, and the Beck Anxiety Inventory. Additionally, a resting-state functional magnetic resonance imaging scan was conducted.

Results

Methylphenidate treatment improved clinical and somatic symptoms in adolescents with ADHD. In addition, it increased brain FC within the DMN from the posterior cingulate cortex (posterior DMN) to the middle prefrontal cortex (anterior DMN). The improvement of somatic symptoms was associated with FC within the DMN from the posterior cingulate cortex to the middle prefrontal cortex in ADHD adolescents with somatic symptoms.

Conclusion

Methylphenidate increased brain FC between the anterior and posterior DMN. The improvement of somatic symptoms in adolescents with ADHD was associated with FC within the DMN. The DMN in adolescents with ADHD seems to be associated with the severity of the clinical and somatic symptoms of ADHD.

The effects of psychostimulants on cognitive functions in individuals with attention-deficit hyperactivity disorder: A systematic review

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is associated with a broad range of deficits in cognitive functions which has significant implications for quality of life. Psychostimulants are demonstrated to improve symptoms of inattention and hyperactivity/impulsivity, however, their impact on cognition remains incompletely characterized. Herein, the aim of this systematic review is to synthesize the extant literature reporting on the effects of psychostimulants on cognitive function in individuals with ADHD.

METHOD

A systematic search of PubMed, Scopus, and Web of Science from inception to July 2021 was conducted. Additional studies were identified through Google Scholar and a manual search of the reference lists of relevant articles. Inclusion criteria were original studies that evaluated the cognitive function of individuals with ADHD taking psychostimulants drugs. We assessed the quality of the included papers using the Newcastle-Ottawa scale (NOS).

RESULTS

A total of 10 studies involving 753 subjects with ADHD and 194 healthy controls were identified and eligible for inclusion. Nine studies evaluated the impact of methylphenidate on cognitive function and one study investigated the use of lisdexamfetamine. Results indicated that attentional deficits such as memory, vigilance, divided attention, phasic and tonic alertness, and focused attention were improved in ADHD patients treated with psychostimulants. The efficacy of psychostimulants in improving other domains of cognition remains inconclusive due to conflicting evidence or insignificant findings (ie. academic performance and executive function). Overall, results indicate that psychostimulants may improve only select domains of cognition (ie. memory and attention).

CONCLUSION

Psychostimulants are reported to improve several disparate aspects of cognition among individuals with ADHD. Further research is needed to better understand the complex relationships between cognition and behavior in ADHD, as well as the impact of medication on these distinct aspects of functioning. Further research is also needed to determine whether the pro-cognitive effect of stimulants would be transferable to other mental disorders.

Investigating the associations between irritability and hot and cool executive functioning in those with ADHD

BACKGROUND

Irritability is especially pertinent to those with Attention Deficit Hyperactivity Disorder (ADHD) as it is highly prevalent and associated with a more severe clinical presentation and poorer longitudinal outcomes. Preliminary evidence suggests that top-down cognitive processes taking place in emotional contexts (i.e., hot executive functions) as opposed to those evoked in abstract scenarios (i.e., cool executive functions) may be relevant to the presentation of irritability in ADHD. This study explored the cognitive mechanisms underlying irritability in young people with ADHD, hypothesising that irritability would be associated with hot, but not cool, executive function impairments.

METHODS

Our sample included 219 individuals with ADHD. A composite irritability score was derived extracting items from a parent interview, with scores ranging from 0 to 5. Associations were investigated using linear regression analyses, between irritability and four hot tasks measuring sensitivity to risk, risk-taking behaviour following reward or punishment, acceptance of reward delay and reaction to unfair behaviour from others, and two cool tasks measuring set-shifting and motor inhibition.

RESULTS

As hypothesised, there were no significant associations between irritability and cool executive functions in those with ADHD; however, contrary to expectations, there was also no significant evidence that hot executive functions were associated with irritability.

CONCLUSIONS

These results, in a large well characterised sample and using a comprehensive task battery, suggest that the variation in irritability in those with ADHD may not be associated with differences in hot or cool executive function performance.

Supported Diagnosis of Attention Deficit and Hyperactivity Disorder from EEG Based on Interpretable Kernels for Hidden Markov Models

As a neurodevelopmental pathology, Attention Deficit Hyperactivity Disorder (ADHD) mainly arises during childhood. Persistent patterns of generalized inattention, impulsivity, or hyperactivity characterize ADHD that may persist into adulthood. The conventional diagnosis relies on clinical observational processes yielding high rates of overdiagnosis due to varying interpretations among specialists or missing information. Although several studies have designed objective behavioral features to overcome such an issue, they lack significance. Despite electroencephalography (EEG) analyses extracting alternative biomarkers using signal processing techniques, the nonlinearity and nonstationarity of EEG signals restrain performance and generalization of hand-crafted features. This work proposes a methodology to support ADHD diagnosis by characterizing EEG signals from hidden Markov models (HMM), classifying subjects based on similarity measures for probability functions, and spatially interpreting the results using graphic embeddings of stochastic dynamic models. The methodology learns a single HMM for EEG signal from each patient, so favoring the inter-subject variability. Then, the Probability Product Kernel, specifically developed for assessing the similarity between HMMs, fed a support vector machine that classifies subjects according to their stochastic dynamics. Lastly, the kernel variant of Principal Component Analysis provided a means to visualize the EEG transitions in a two-dimensional space, evidencing dynamic differences between ADHD and Healthy Control children. From the electrophysiological perspective, we recorded EEG under the Stop Signal Task modified with reward levels, which considers cognitive features of interest as insufficient motivational circuits recruitment. The methodology compares the supported diagnosis in two EEG channel setups (whole channel set and channels of interest in frontocentral area) and four frequency bands (Theta, Alpha, Beta rhythms, and a wideband). Results evidence an accuracy rate of 97.0% in the Beta band and in the channels where previous works found error-related negativity events. Such accuracy rate strongly supports the dual pathway hypothesis and motivational deficit concerning the pathophysiology of ADHD. It also demonstrates the utility of joining inhibitory and motivational paradigms with dynamic EEG analysis into a noninvasive and affordable diagnostic tool for ADHD patients.

Effects of the SNAP25 on Integration Ability of Brain Functions in Children With ADHD

OBJECTIVE

The present study aimed to examine the effects of SNAP25 on the integration ability of intrinsic brain functions in children with ADHD, and whether the integration ability was associated with working memory (WM).

METHODS

A sliding time window method was used to calculate the spatial and temporal concordance among five rs-fMRI regional indices in 55 children with ADHD and 20 healthy controls.

RESULTS

The SNAP25 exhibited significant interaction effects with ADHD diagnosis on the voxel-wise concordance in the right posterior central gyrus, fusiform gyrus and lingual gyrus. Specifically, for children with ADHD, G-carriers showed increased voxel-wise concordance in comparison to TT homozygotes in the right precentral gyrus, superior frontal gyrus, postcentral gyrus, and middle frontal gyrus. The voxel-wise concordance was also found to be related to WM.

CONCLUSION

Our findings provided a new insight into the neural mechanisms of the brain function of ADHD children.

Current Pharmacological Treatments for ADHD

Attention-Deficit Hyperactivity Disorder (ADHD) is a prevalent neurodevelopmental condition associated with impaired function and increased risk of poor outcomes in children, young people and adults with the condition. Currently approved pharmacological treatments for ADHD include a range of stimulant (methylphenidate, amphetamine) and nonstimulant (atomoxetine, guanfacine, clonidine) medications. All have been shown to be effective in treating the symptoms of ADHD and improving other functional outcomes including quality of life, academic performance, rates of accidents and injuries, and do not appear to be associated with significant adverse outcomes or side effects. In this chapter, we review medications for ADHD by summarising the mechanisms of action of each of the two main classes of compounds (stimulants and nonstimulants), the formulations of the most commonly prescribed medications within each class, their efficacy in treating ADHD symptoms and other outcomes, and other factors that influence treatment decisions including side effects and tolerability, comorbidities and medical history. We conclude with a summary of the treatment decisions made by clinicians and suggest some next steps for research. Further research is needed to understand the mechanisms of action of these medications and how exactly they improve symptoms, and to examine their effects on commonly occurring comorbidities.

HIV infection is linked with reduced error-related default mode network suppression and poorer medication management abilities

OBJECTIVE

Brain activity linked with error processing has rarely been examined among persons living with HIV (PLWH) despite importance for monitoring and modifying behaviors that could lead to adverse health outcomes (e.g., medication non-adherence, drug use, risky sexual practices). Given that cannabis (CB) use is prevalent among PLWH and impacts error processing, we assessed the influence of HIV serostatus and chronic CB use on error-related brain activity while also considering associated implications for everyday functioning and clinically-relevant disease management behaviors.

METHODS

A sample of 109 participants, stratified into four groups by HIV and CB (HIV+/CB+, n = 32; HIV+/CB-, n = 27; HIV-/CB+, n = 28; HIV-/CB-, n = 22), underwent fMRI scanning while completing a modified Go/NoGo paradigm called the Error Awareness Task (EAT). Participants also completed a battery of well-validated instruments including a subjective report of everyday cognitive failures and an objective measure of medication management abilities.

RESULTS

Across all participants, we observed expected error-related anterior insula (aI) activation which correlated with better task performance (i.e., less errors) and, among HIV- participants, fewer self-reported cognitive failures. Regarding awareness, greater insula activation as well as greater posterior cingulate cortex (PCC) deactivation were notably linked with aware (vs. unaware) errors. Regarding group effects, unlike HIV- participants, PLWH displayed a lack of error-related deactivation in two default mode network (DMN) regions (i.e., PCC, medial prefrontal cortex [mPFC]). No CB main or interaction effects were detected. Across all participants, reduced error-related PCC deactivation correlated with reduced medication management abilities and PCC deactivation mediated the effect of HIV on such abilities. More lifetime CB use was linked with reduced error-related mPFC deactivation among HIV- participants and poorer medication management across CB users.

CONCLUSIONS

These results demonstrate that insufficient error-related DMN suppression linked with HIV infection, as well as chronic CB use among HIV- participants, has real-world consequences for medication management behaviors. We speculate that insufficient DMN suppression may reflect an inability to disengage task irrelevant mental operations, ultimately hindering error monitoring and behavior modification.

Decreased Neural Connectivity in the Default Mode Network Among Youth and Young Adults With Chronic Kidney Disease

An increasing amount of literature has indicated that chronic kidney disease (CKD) is associated with cognitive deficits that increase with worsening disease severity. Although abnormalities in brain structure have been widely documented, few studies to date have examined the functioning of brain areas associated with the specific cognitive domains affected by CKD (namely, attention and executive functions). Furthermore, few studies have examined functional connectivity among CKD youth who are relatively early in the course of the disease. The present study used functional magnetic resonance imaging to examine the resting state connectivity in 67 youth with CKD (mean age, 17 y) and 58 age-matched healthy controls. Using seed-based multiple regression, decreased connectivity was observed within the anterior cingulate portion of the default mode network. In addition, decreased connectivity within the dorsolateral prefrontal cortex, paracingulate gyrus, and frontal pole were correlated significantly with disease severity. These data indicate that connectivity deficits in circuits implementing attentional processes may represent an early marker for cognitive decline in CKD.

Purkinje cells translate subjective salience into readiness to act and choice performance

The brain selectively allocates attention from a continuous stream of sensory input. This process is typically attributed to computations in distinct regions of the forebrain and midbrain. Here, we explore whether cerebellar Purkinje cells encode information about the selection of sensory inputs and could thereby contribute to non-motor forms of learning. We show that complex spikes of individual Purkinje cells change the sensory modality they encode to reflect changes in the perceived salience of sensory input. Comparisons with mouse models deficient in cerebellar plasticity suggest that changes in complex spike activity instruct potentiation of Purkinje cells simple spike firing, which is required for efficient learning. Our findings suggest that during learning, climbing fibers do not directly guide motor output, but rather contribute to a general readiness to act via changes in simple spike activity, thereby bridging the sequence from non-motor to motor functions.

Assessment of Optical Coherence Tomography Findings in Adults with Attention Deficit Hyperactivity Disorder: A Case-Control Study

Background

To assess retinal nerve fiber layer and ganglion cell-inner plexiform layer thickness using optical coherence tomography in attention deficit hyperactivity disorder adults on regular methylphenidate treatment, comparing them to healthy controls.

Methods

A total of 33 attention deficit hyperactivity disorder adults and 31 healthy subjects, matched for age, gender, and education (control group), were included in this study. Retinal nerve fiber layer and ganglion cell-inner plexiform layer thickness of both eyes were measured using optical coherence tomography, and symptom severity was evaluated using Adult Attention Deficit Hyperactivity Disorder Self-Report Scale and Wender Utah Rating Scale.

Results

There was no significant difference in retinal nerve fiber layer thickness between the attention deficit hyperactivity disorder and control groups (P > .05). Thinner ganglion cell-inner plexiform layer total (P = .044), inferior (P = .012), and inferior nasal quadrant thickness (P = .049) were observed in attention deficit hyperactivity disorder patients as compared to the controls.

Conclusion

Findings detected thinner ganglion cell-inner plexiform layer in some quadrants of attention deficit hyperactivity disorder adults, indicating an early disorder in retinal structure development. Whether retinal structures are sensitive attention deficit hyperactivity disorder biomarkers should be supported and investigated in future multimodal studies.

Context Regulation of Mind Wandering in ADHD

OBJECTIVE

We aimed to understand the association between MW frequency and clinical measures, context regulation of MW and group differences in task performance.

METHOD

27 adults with ADHD and 29 controls performed tasks manipulating demand on working memory and sustained attention, and recorded their MW frequency using probes.

RESULTS

A significant association between MW frequency and the clinical measures was demonstrated. Along with increased MW frequency, individuals with ADHD reported decreasing MW frequency during increasing demands on working memory (context regulation), but not on sustained attention (deficient context regulation). Controls, however, maintained continuous task focus across all conditions. Group differences in task performance were no longer significant after adding MW frequency as a covariate.

CONCLUSION

Deficient context regulation during increasing demands on sustained attention suggests that sustained attention deficits may play a more important role in regulation of MW in ADHD. MW frequency might also underpin performance deficits in ADHD.

The Limits of Motivational Influence in ADHD: No Evidence for an Altered Reaction to Negative Reinforcement

Functional magnetic resonance imaging studies have reported a diminished response in the brain’s reward circuits to contingent cues predicting future monetary gain in adolescents with attention-deficit/hyperactivity disorder (ADHD). The situation with regard to monetary loss is less clear, despite recognition that both positive and negative consequences impact ADHD behaviour. Here, we employ a new Escape Monetary Loss Incentive task in an MRI scanner, which allows the differentiation of contingency and valence effects during loss avoidance, to examine ADHD-related alterations in monetary loss processing. There was no evidence of atypical processing of contingent or non-contingent monetary loss cues in ADHD — either in terms of ratings of emotional and motivational significance or brain responses. This suggests that the ability to process contingencies between performance and negative outcomes is intact in ADHD and that individuals with ADHD are no more (or less) sensitive to negative outcomes than controls. This latter finding stands in stark contrast to recent evidence from a similar task of atypical emotion network recruitment (e.g. amygdala) in ADHD individuals to cues predicting another negative event, the imposition of delay, suggesting marked specificity in the way they respond to negative events.

Methylphenidate for attention-deficit/hyperactivity disorder in adults: a narrative review

RATIONALE

Psychostimulants, including methylphenidate (MPH), are the mainstay of pharmacotherapy for attention-deficit/hyperactivity disorder (ADHD) in adults. Even though MPH is the most commonly used medication for ADHD these days, there are relatively few resources available that provide comprehensive insight into the pharmacological and clinical features of the compound.

OBJECTIVE

The aim of this paper is to provide an up-to-date outline of the pharmacology and clinical utility of MPH for ADHD in adult patients.

METHODS

While conducting the narrative review, we applied structured search strategies covering the two major online databases (MEDLINE and Cochrane Central Register of Controlled Trials). In addition, we performed handsearching of reference lists of relevant papers.

RESULTS

Methylphenidate exhibits multimodal mechanism of action, working primarily as a dopamine and noradrenaline reuptake inhibitor. It also protects the dopaminergic system against the ongoing 'wearing off' (by securing a substantial reserve pool of the neurotransmitter, stored in the presynaptic vesicles). In placebo-controlled trials, MPH was shown to be moderately effective both against the core ADHD symptoms (standardized mean difference [SMD], 0.49; 95% confidence interval [CI], 0.35-0.64), and the accompanying emotion regulation deficits (SMD, 0.34; 95% CI, 0.23-0.45). The most common adverse events related to long-term treatment with MPH are decreased appetite (~ 20%), dry mouth (15%), heart palpitations (13%), gastrointestinal infections (~ 10%), and agitation/feeling restless (~ 10%).

CONCLUSIONS

There is substantial body of evidence to suggest that MPH is an effective and safe treatment option for adults with ADHD.

A Longitudinal Study of Resting-State Connectivity and Response to Psychostimulant Treatment in ADHD

OBJECTIVE

Psychostimulants are first-line pharmacological treatments for attention deficit hyperactivity disorder (ADHD), although symptom reduction varies widely between patients and these individual differences in treatment response are poorly understood. The authors sought to examine whether the resting-state functional connectivity within and between cingulo-opercular, striato-thalamic, and default mode networks was associated with treatment response to psychostimulant medication, and whether this relationship changed with development.

METHODS

Patients with ADHD (N=110; 196 observations; mean age at first observation, 10.83 years, SD=2.2) and typically developing control subjects (N=142; 330 observations; mean age at first observation, 10.49 years, SD=2.81) underwent functional neuroimaging on up to five occasions during development (age range, 6-17 years). For patients, symptoms were assessed on and off psychostimulant medication (methylphenidate-based treatments: N=132 observations, 67%; amphetamine-based treatments: N=64 observations, 33%) using the Diagnostic Interview for Children and Adolescents for parents. Linear mixed-effects models examined whether resting-state connectivity was associated with treatment response and its interaction with age. Comparisons with typically developing control subjects were performed to contextualize any significant associations.

RESULTS

Resting-state connectivity within the cingulo-opercular network was associated with a significant interaction between treatment response and age. Specifically, worse responses to treatment compared with better responses to treatment among patients and compared with typically developing control subjects were associated with an atypical increase in cingulo-opercular connectivity with increasing age from childhood to adolescence.

CONCLUSIONS

This work delineates how resting-state connectivity may be associated over development with response to psychostimulants in ADHD. Functioning and development within the cingulo-opercular network may warrant further investigation as a contributor to differential response to psychostimulants.

ADHD symptoms map onto noise-driven structure-function decoupling between hub and peripheral brain regions

Adults with childhood-onset attention-deficit hyperactivity disorder (ADHD) show altered whole-brain connectivity. However, the relationship between structural and functional brain abnormalities, the implications for the development of life-long debilitating symptoms, and the underlying mechanisms remain uncharted. We recruited a unique sample of 80 medication-naive adults with a clinical diagnosis of childhood-onset ADHD without psychiatric comorbidities, and 123 age-, sex-, and intelligence-matched healthy controls. Structural and functional connectivity matrices were derived from diffusion spectrum imaging and multi-echo resting-state functional MRI data. Hub, feeder, and local connections were defined using diffusion data. Individual-level measures of structural connectivity and structure-function coupling were used to contrast groups and link behavior to brain abnormalities. Computational modeling was used to test possible neural mechanisms underpinning observed group differences in the structure-function coupling. Structural connectivity did not significantly differ between groups but, relative to controls, ADHD showed a reduction in structure-function coupling in feeder connections linking hubs with peripheral regions. This abnormality involved connections linking fronto-parietal control systems with sensory networks. Crucially, lower structure-function coupling was associated with higher ADHD symptoms. Results from our computational model further suggest that the observed structure-function decoupling in ADHD is driven by heterogeneity in neural noise variability across brain regions. By highlighting a neural cause of a clinically meaningful breakdown in the structure-function relationship, our work provides novel information on the nature of chronic ADHD. The current results encourage future work assessing the genetic and neurobiological underpinnings of neural noise in ADHD, particularly in brain regions encompassed by fronto-parietal systems.

Response inhibition in adolescents is moderated by brain connectivity and social network structure

The social environment an individual is embedded in influences their ability and motivation to engage self-control processes, but little is known about the neural mechanisms underlying this effect. Many individuals successfully regulate their behavior even when they do not show strong activation in canonical self-control brain regions. Thus, individuals may rely on other resources to compensate, including daily experiences navigating and managing complex social relationships that likely bolster self-control processes. Here, we employed a network neuroscience approach to investigate the role of social context and social brain systems in facilitating self-control in adolescents. We measured brain activation using functional magnetic resonance imaging (fMRI) as 62 adolescents completed a Go/No-Go response inhibition task. We found that self-referential brain systems compensate for weaker activation in executive function brain systems, especially for adolescents with more friends and more communities in their social networks. Collectively, our results indicate a critical role for self-referential brain systems during the developmental trajectory of self-control throughout adolescence.

Do Teachers Confirm Parent's Ratings of ADHD DSM-IV Criteria? A Study of a Mexican Population

BACKGROUND AND OBJECTIVE

Collecting information from different raters is important for diagnosing ADHD, but several factors can lead to gathering discrepant information. Our aim was to determine the agreement between parent and teacher's when rating the list of ADHD symptoms (criterion A, DSM-IV) in a sample of Mexican school-age children. We explored whether inter-rater agreement varied by children's age and sex, and each symptom of inattention, hyperactivity, and impulsivity.

METHODS

A total of 789 children (335 girls) from six elementary school grades grouped as G1 [grades 1-2], G2 [grades 3-4], and G3 [grades 5-6]) were rated by their parents and teachers. We identified inter-rater reliability by using Cohen's kappa coefficient by school level, sex, and ADHD symptoms. We explored the presence of symptoms considering parents' and teachers' ratings, individually and collapsed, using the AND/OR rules.

RESULTS

Low inter-rater agreement was observed. Moderate levels were observed in G1, but not in G2 or G3. Both groups of informants reported that more boys than girls met these criteria, but agreement by sex was still low, as were the results of the analyses by individual symptoms. Among the children that met the ADHD criteria, an inattention symptom was the one most frequently reported by both raters, whereas among non-ADHD children, a hyperactive symptom was the one most often reported.

DISCUSSION

The exclusive use of questionnaires fails to provide convergent information between raters. We highlight the importance of conducting comprehensive clinical histories when diagnosing ADHD in order to explore what these discrepancies show about the relationship symptoms/context.

Electrophysiological Correlates of Rodent Default-Mode Network Suppression Revealed by Large-Scale Local Field Potential Recordings

The default-mode network (DMN) in humans consists of a set of brain regions that, as measured with functional magnetic resonance imaging (fMRI), show both intrinsic correlations with each other and suppression during externally oriented tasks. Resting-state fMRI studies have previously identified similar patterns of intrinsic correlations in overlapping brain regions in rodents (A29C/posterior cingulate cortex, parietal cortex, and medial temporal lobe structures). However, due to challenges with performing rodent behavior in an MRI machine, it is still unclear whether activity in rodent DMN regions are suppressed during externally oriented visual tasks. Using distributed local field potential measurements in rats, we have discovered that activity in DMN brain regions noted above show task-related suppression during an externally oriented visual task at alpha and low beta-frequencies. Interestingly, this suppression (particularly in posterior cingulate cortex) was linked with improved performance on the task. Using electroencephalography recordings from a similar task in humans, we identified a similar suppression of activity in posterior cingulate cortex at alpha/low beta-frequencies. Thus, we have identified a common electrophysiological marker of DMN suppression in both rodents and humans. This observation paves the way for future studies using rodents to probe circuit-level functioning of DMN function.

SIGNIFICANCE

Here we show that alpha/beta frequency oscillations in rats show key features of DMN activity, including intrinsic correlations between DMN brain regions, task-related suppression, and interference with attention/decision-making. We found similar task-related suppression at alpha/low beta-frequencies of DMN activity in humans.

Temporal Dynamics of Functional Brain States Underlie Cognitive Performance

The functional organization of the human brain adapts dynamically in response to a rapidly changing environment. However, the relation of these rapid changes in functional organization to cognitive functioning is not well understood. This study used a graph-based time-frame modularity analysis approach to identify temporally recurrent functional configuration patterns in neural responses to an n-back working memory task during fMRI. Working memory load was manipulated to investigate the functional relevance of the identified brain states. Four distinct brain states were defined by the predominant patterns of activation in the task-positive, default-mode, sensorimotor, and visual networks. Associated with escalating working memory load, the occurrence of the task-positive state and the probability of transitioning into this state increased. In contrast, the occurrence of the default-mode and sensorimotor states and the probability of these 2 states transitioning away from the task-positive state decreased. The task-positive state occurrence rate and the probability of transitioning from the default-mode state back to the task-positive state explained a significant and unique portion of the variance in task performance. The results demonstrate that dynamic brain activities support successful cognitive functioning and may have heuristic value for understanding abnormal cognitive functioning associated with multiple neuropsychiatric disorders.

l-Cystine is associated with the dysconnectivity of the default-mode network and salience network in attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder. Distributed dysconnectivity within both the default-mode network (DMN) and the salience network (SN) has been observed in ADHD. L-cystine may serve as a neuroprotective molecule and signaling pathway, as well as a biomarker of ADHD. The purpose of this study was to explore whether differential brain network connectivity is associated with peripheral L-cystine levels in ADHD patients. We recruited a total of 31 drug-naïve patients with ADHD (mean age: 10.4 years) and 29 healthy controls (mean age: 10.3 years) that underwent resting state functional magnetic resonance imaging scans. Functional connectomes were generated for each subject, and we examined the cross-sectional group difference in functional connectivity (FC) within and between DMN and SN. L-cystine plasma levels were determined using high-performance chemical isotope labeling (CIL)-based liquid chromatography-mass spectrometry (LC-MS). Compared to the control group, the ADHD group showed decreased FC of dorsal DMN (p = 0.031), as well as decreased FC of precuneus-post SN (p = 0.006) and ventral DMN-post SN (p = 0.001). The plasma L-cystine levels of the ADHD group were significantly higher than in the control group (p = 0.002). Furthermore, L-cystine levels were negatively correlated with FC of precuneus-post SN (r = -0.404, p = 0.045) and ventral DMN-post SN (r = -0.540, p = 0.007). The findings suggest that decreased synergies of DMN and SN may serve as neurobiomarkers for ADHD, while L-cystine may be involved in the pathophysiology of network dysconnectivity. Future studies on the molecular mechanism of the cystine-glutamate system in brain network connectivity are warranted.

A new era for executive function research: On the transition from centralized to distributed executive functioning

"Executive functions" (EFs) is an umbrella term for higher cognitive control functions such as working memory, inhibition, and cognitive flexibility. One of the most challenging problems in this field of research has been to explain how the wide range of cognitive processes subsumed as EFs are controlled without an all-powerful but ill-defined central executive in the brain. Efforts to localize control mechanisms in circumscribed brain regions have not led to a breakthrough in understanding how the brain controls and regulates itself. We propose to re-conceptualize EFs as emergent consequences of highly distributed brain processes that communicate with a pool of highly connected hub regions, thus precluding the need for a central executive. We further discuss how graph-theory driven analysis of brain networks offers a unique lens on this problem by providing a reference frame to study brain connectivity in EFs in a holistic way and helps to refine our understanding of the mechanisms underlying EFs by providing new, testable hypotheses and resolves empirical and theoretical inconsistencies in the EF literature.

Categorizing SHR and WKY rats by chi2 algorithm and decision tree

Classifying mental disorder is a big issue in psychology in recent years. This article focuses on offering a relation between decision tree and encoding of fMRI that can simplify the analysis of different mental disorders and has a high ROC over 0.9. Here we encode fMRI information to the power-law distribution with integer elements by the graph theory in which the network is characterized by degrees that measure the number of effective links exceeding the threshold of Pearson correlation among voxels. When the degrees are ranked from low to high, the network equation can be fit by the power-law distribution. Here we use the mentally disordered SHR and WKY rats as samples and employ decision tree from chi2 algorithm to classify different states of mental disorder. This method not only provides the decision tree and encoding, but also enables the construction of a transformation matrix that is capable of connecting different metal disorders. Although the latter attempt is still in its fancy, it may have a contribution to unraveling the mystery of psychological processes.

Emotion recognition and mind wandering in adults with attention deficit hyperactivity disorder or autism spectrum disorder

Attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) in adults are often undiagnosed and overlap in psychopathology. Here we investigated the transdiagnostic traits of emotion recognition and mind wandering in a sample of 103 adults (43 with ADHD and 14 with ASD). The ability to correctly identify a facial expression of anger, fear, disgust or surprise was no different between the adults with ADHD or ASD and neurotypical (NT) adults. However, adults with ADHD or ASD were on average almost 200 ms slower in making a correct decision, suggesting a larger speed-accuracy trade-off in facial emotion recognition compared to NT adults. General processing speed was associated with excessive mind wandering in adults with ADHD, but not with ASD. The deficits in emotional processing were independent from mind wandering in both adults with ADHD or ASD. Emotional dysregulation and functional impairment scales separated adults with ADHD and ASD from the NT adults, but not from each other. When controlling for self-reported ADHD and ASD symptom severity, mind wandering in ADHD was independent from both ADHD and ASD symptom severity. In ASD, mind wandering was related to ASD but not ADHD symptom severity. Our results suggest that ASD and ADHD share a slower ability to recognize emotions, which is exacerbated by excessive mind wandering in ADHD, and by decreased processing speed in ASD.