Methylphenidate normalizes fronto-striatal underactivation during interference inhibition in medication-naïve boys with attention-deficit hyperactivity disorder

Neural markers of methylphenidate response in children with attention deficit hyperactivity disorder and the impact on executive function

Background

Attention Deficit Hyperactivity Disorder (ADHD) is a common neurodevelopmental disorder characterized by inattention, hyperactivity, and impulsivity. A core cognitive deficit in ADHD is executive function (EF) impairment, which significantly impacts daily life. Methylphenidate (MPH) is a widely used first-line treatment for ADHD, but objective biomarkers to assess treatment response are lacking. The aim of this study was to investigate the effects of MPH on executive function and identify potential neural biomarkers of response in children with ADHD using electroencephalogram (EEG).

Methods

A total of 26 boys with ADHD (mean age 8.64 ± 1.30 years) participated in the study. All participants were treated with 18 mg/day of oral extended-release MPH in the morning for 8 weeks. Executive function was assessed using the BRIEF2 and Digit Span Test (DST), and event-related potentials (ERP) were measured at baseline and after 8 weeks of MPH treatment.

Results

After 8 weeks of MPH treatment, significant improvements were observed in several executive function domains. BRIEF2 scores, including inhibition, self-monitoring, shifting, emotional control, initiation, working memory, planning/organization, task monitoring, and material organization, were significantly reduced (P < 0.05). Behavioral performance in the Go/NoGo task also improved, with shorter correct response times and higher accuracy rates (P = 0.002, P = 0.009). EEG results revealed a reduction in Nogo-P300 latency at Fz, Cz and Pz compared to baseline (P<0.05).

Conclusions

The normalization of P300 latency following MPH treatment appears to be a reliable neural biomarker of positive treatment response in children with ADHD. MPH was associated with improvements in executive function, particularly in inhibitory control and working memory.

Neural correlates of executive function and attention in children with ADHD: An ALE meta-analysis of task-based functional connectivity studies

We conducted a comprehensive meta-analysis of task-based functional MRI studies on executive function and attention in children with attention deficit hyperactivity disorder (ADHD). We searched for studies published before March 20, 2023, in PubMed, Cochrane Library, Web of Science, EBSCO, Embase, and Scopus. The ALE (activation likelihood estimation) method was used to detect differences in brain activation between children with ADHD and comparison children. Fifty-seven (57) studies were included, with 2,231 participants (1,062 children with ADHD). Based on the omnibus meta-analysis findings, significant hypoactivation in children with ADHD relative to comparisons was observed in the frontoparietal network, putamen, insula, cingulate gyrus, and middle temporal gyrus, while ADHD-related hyperactivation was present in the occipital lobe, declive, middle frontal gyrus, and parahippocampal gyrus. This study highlights the critical involvement of the parietal lobe. Results also revealed abnormalities in the frontal lobe and brainstem, suggesting unintegrated primitive reflexes. For stimulant-naive children with ADHD, significant hypoactivation in the right cerebrum was observed compared to controls. Finally, dysfunctional connectivity between the frontoparietal network and the striatum may lead to inefficient working memory, while the cerebellum plays a crucial role in inhibitory control and attention tasks. These findings provide important insights into the pathology of ADHD.

Overlapping and differential neuropharmacological mechanisms of stimulants and nonstimulants for attention-deficit/hyperactivity disorder: a comparative neuroimaging analysis

BACKGROUND

Psychostimulants and nonstimulants have partially overlapping pharmacological targets on attention-deficit/hyperactivity disorder (ADHD), but whether their neuroimaging underpinnings differ is elusive. We aimed to identify overlapping and medication-specific brain functional mechanisms of psychostimulants and nonstimulants on ADHD.

METHODS

After a systematic literature search and database construction, the imputed maps of separate and pooled neuropharmacological mechanisms were meta-analyzed by Seed-based d Mapping toolbox, followed by large-scale network analysis to uncover potential coactivation patterns and meta-regression analysis to examine the modulatory effects of age and sex.

RESULTS

Twenty-eight whole-brain task-based functional MRI studies (396 cases in the medication group and 459 cases in the control group) were included. Possible normalization effects of stimulant and nonstimulant administration converged on increased activation patterns of the left supplementary motor area (Z = 1.21, p < 0.0001, central executive network). Stimulants, relative to nonstimulants, increased brain activations in the left amygdala (Z = 1.30, p = 0.0006), middle cingulate gyrus (Z = 1.22, p = 0.0008), and superior frontal gyrus (Z = 1.27, p = 0.0006), which are within the ventral attention network. Neurodevelopmental trajectories emerged in activation patterns of the right supplementary motor area and left amygdala, with the left amygdala also presenting a sex-related difference.

CONCLUSIONS

Convergence in the left supplementary motor area may delineate novel therapeutic targets for effective interventions, and distinct neural substrates could account for different therapeutic responses to stimulants and nonstimulants.

Visualizing changes in cerebral hemodynamics in children with ADHD who have discontinued methylphenidate: A pilot study on using brain function for medication discontinuation decisions

OBJECTIVE

This study undertook neuropharmacological research on the clinical course of controlled medication discontinuation to guide practitioners who are considering stopping medications for youths with attention-deficit hyperactivity disorder (ADHD).

METHODS

This study analyzed the data for 14 ADHD children (12 male and 2 female) in two datasets: The children prescribed methylphenidate (MPH) were at an initial mean age of 7.5 years (SD = 1.70, range: 6-11) with a mean ADHD-Rating Score (ADHD-RS) of 26.6 (SD = 8.64, range 15-40). The children who discontinued MPH based on clinical judgment were at a mean age of 12.21 years (SD = 2.12, range: 8-15) with a mean ADHD-RS of 15.9 (SD = 6.86, range 5-27). The go/no-go task was used to assess response inhibition, while functional near-infrared spectroscopy (fNIRS) was used to measure cerebral hemodynamics. Oxygenated hemoglobin (Oxy-Hb) values from fNIRS data were analyzed for each subject, focusing on past and current measurements. Baseline was set at 10 s pre-task, with interval means from 4 to 24 s analyzed. One-sample t-tests were used to evaluate brain activity magnitude.

RESULTS

The results of the study demonstrate that the children who had discontinued the medication exhibited activation in specific brain regions including the frontopolar cortex and the right ventrolateral prefrontal cortex. Activation (t = 2.363, p = 0.034, Cohen's d = 0.632) was found especially in the right dorsolateral prefrontal cortex during the performance of the go/no-go task. These activated areas were consistent with those observed in a previous study comparing brain activity during a go/no-go task between children with ADHD and healthy children.

CONCLUSION

The present study showed differences in cerebral hemodynamics before and after discontinuation of MPH in ADHD children whose ADHD symptoms did not recur after MPH was discontinued. In the near future, further investigations that include control groups will be conducted to demonstrate the effects of MPH prior to discontinuation based on the changes in cerebral blood flow in the right prefrontal cortex, which is involved in behavioral inhibition, as observed in this study. This and future research will facilitate the development of criteria for discontinuing treatment.

The effect of a single dose of methylphenidate on attention in children and adolescents with ADHD and comorbid Oppositional Defiant Disorder

The co-occurrence Oppositional Defiant Disorder (ODD) in children and adolescents with Attention Deficit Hyperactivity Disorder (ADHD) has been associated to difficulties in regulating adverse states, elevated functional impairment, deficits in Executive Functions and high risk for psychopathology. Recent studies have shown that ODD is a negative predictor of a positive response to methylphenidate (MPH) treatment for ADHD symptoms in children and adolescents and that patients with a diagnosis of comorbid ADHD and ODD are less likely to respond favorably to pharmacological treatment with MPH. We conducted a naturalistic study to understand the clinical characteristics of drug-naïve children and adolescents with ADHD that influence the response to MPH by measuring the effect on attention. Specifically, we investigated whether a single dose of MPH differently affects the performance of 53 children and adolescents with ADHD with or without ODD comorbidity. In addition, participant characteristics such as symptom severity, functional impairment, and associated behavioral and emotional symptoms at baseline were examined to better understand what aspects affect the response to MPH. We found that a single dose of MPH improved the attention of children and adolescents with ADHD without ODD more than those with comorbid ADHD and ODD, resulting in reduced reaction times. Our findings indicated that children and adolescents with comorbid ADHD and ODD and those with ADHD alone did not exhibit differences in measures of attention prior to taking MPH, nor in demographic variables (age, intelligence quotient, gender), clinical characteristics related to symptom severity, and adaptive behaviors. However, we observed differences between the two groups in certain behavioral aspects, including the Dysregulation Profile and disruptive behaviors. Assessing symptoms in combination with the presence of ADHD can be beneficial in determining which individuals would derive the greatest benefits from treatment.

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.

The influence of methylphenidate on auditory brainstem response patients with attention deficit hyperactivity disorder; an exploratory study

Background

Attention-deficit hyperactivity disorder (ADHD), characterized by periods of inattention, overactivity, and impulsiveness, is the most prevalent neurodevelopmental disorder among children. Auditory Brainstem Response (ABR) is a technique in which clickshaped sounds elicit potentials that are recorded from electrodes placed on a patient's skull. Extant research indicates that ABR is frequently affected in neurodevelopmental disorders such as ADHD. Methylphenidate (MPH), a psychostimulant, is often prescribed to children with ADHD as a first-line pharmacological treatment. The aim of this study was to explore the effects of Methylphenidate treatment on previously observed amplitude alterations in the ABR of patients with ADHD.

Methods

We recruited 32 drug-naïve children and adolescents (19 males and 13 females; mean age 11 years) diagnosed with ADHD and 35 health controls (15 males and 20 females; mean age 12 years). The ADHD group was treated with Methylphenidate, and ABR was recorded before treatment and at a steady state of medical treatment.

Results

Medicated ADHD patients exhibited increased activity in the right side ABR in Wave VI.

Conclusions

A significant increase in activity was found in a part of the ABR thought to correspond to the thalamic area in medicated ADHD patients compared to the same area of non-medicated ADHD patients. The results add to the growing body of research suggesting that specific ABR peaks correlate to certain psychiatric symptoms.

Single-dose effects of methylphenidate and atomoxetine on functional connectivity during an n-back task in boys with ADHD

RATIONALE

Working memory deficits and associated neurofunctional abnormalities are frequently reported in attention-deficit/hyperactivity disorder (ADHD). Methylphenidate and atomoxetine improve working memory performance and increase activation of regions under-functioning in ADHD. Additionally, methylphenidate has been observed to modulate functional networks involved in working memory. No research, however, has examined the effects of atomoxetine or compared the two drugs.

OBJECTIVES

This study aimed to test methylphenidate and atomoxetine effects on functional connectivity during working memory in boys with ADHD.

METHODS

We tested comparative effects of methylphenidate and atomoxetine on functional connectivity during the n-back task in 19 medication-naïve boys with ADHD (10-15 years old) relative to placebo and assessed potential normalisation effects of brain dysfunctions under placebo relative to 20 age-matched neurotypical boys. Patients were scanned in a randomised, double-blind, cross-over design under single doses of methylphenidate, atomoxetine, and placebo. Controls were scanned once, unmedicated.

RESULTS

Patients under placebo showed abnormally increased connectivity between right superior parietal gyrus (rSPG) and left central operculum/insula. This hyperconnectivity was not observed when patients were under methylphenidate or atomoxetine. Furthermore, under methylphenidate, patients showed increased connectivity relative to controls between right middle frontal gyrus (rMFG) and cingulo-temporo-parietal and striato-thalamic regions, and between rSPG and cingulo-parietal areas. Interrogating these networks within patients revealed increased connectivity between both rMFG and rSPG and right supramarginal gyrus under methylphenidate relative to placebo. Nonetheless, no differences across drug conditions were observed within patients at whole brain level. No drug effects on performance were observed.

CONCLUSIONS

This study shows shared modulating effects of methylphenidate and atomoxetine on parieto-insular connectivity but exclusive effects of methylphenidate on connectivity increases in fronto-temporo-parietal and fronto-striato-thalamic networks in ADHD.

Methylphenidate is more effective to improve inhibitory control and working memory compared to tDCS in children and adolescents with attention deficit/hyperactivity disorder: a proof-of-concept study

Introduction

Attention-deficit/hyperactivity disorder (ADHD) is characterized by an inappropriate, pervasive and persistent pattern of inattention, hyperactivity, and/or impulsivity and associated with substantial functional impairment. Despite considerable advances in the understanding and management of ADHD, some patients do not respond well to methylphenidate (MPH), the first-choice pharmacological treatment. Over the past decades, among non-invasive brain stimulation techniques, transcranial direct current stimulation (tDCS) has proven to be an effective and safe technique to improve behavior and cognition in children with neurodevelopmental disorders, including ADHD, by modifying cortical excitability. However, the effect of tDCS has never been directly compared with that of the MPH. The present randomized sham-controlled trial evaluated the effect of a single session of anodal tDCS compared with the administration of a single dose of MPH in children and adolescents with ADHD.

Methods

After completing baseline assessment (T0), 26 children and adolescents with ADHD were exposed to 3 conditions with a 24-h interval-sessions: (A) a single session of anodal tDCS over the left dorsolateral prefrontal cortex (DLPFC); (B) a single session of sham tDCS over the left DLPFC; (C) a single dose of MPH.

Results

Our results showed that after administering a single dose of MPH, children and adolescents with ADHD improved inhibitory control and visual-spatial WM compared with baseline, anodal, and sham tDCS. However, a single session of active tDCS over the left DLPFC was not effective compared with either baseline or sham tDCS.

Discussion

In conclusion, our protocol in ADHD involving a single tDCS session did not demonstrate consistent improvements in neurocognitive features compared with baseline, sham tDCS, or single MPH administration. Different protocols need to be developed to further test the effectiveness of tDCS in improving ADHD symptoms.

Insulin and Disorders of Behavioural Flexibility

Behavioural inflexibility is a symptom of neuropsychiatric and neurodegenerative disorders such as Obsessive-Compulsive Disorder, Autism Spectrum Disorder and Alzheimer's Disease, encompassing the maintenance of a behaviour even when no longer appropriate. Recent evidence suggests that insulin signalling has roles apart from its regulation of peripheral metabolism and mediates behaviourally-relevant central nervous system (CNS) functions including behavioural flexibility. Indeed, insulin resistance is reported to generate anxious, perseverative phenotypes in animal models, with the Type 2 diabetes medication metformin proving to be beneficial for disorders including Alzheimer's Disease. Structural and functional neuroimaging studies of Type 2 diabetes patients have highlighted aberrant connectivity in regions governing salience detection, attention, inhibition and memory. As currently available therapeutic strategies feature high rates of resistance, there is an urgent need to better understand the complex aetiology of behaviour and develop improved therapeutics. In this review, we explore the circuitry underlying behavioural flexibility, changes in Type 2 diabetes, the role of insulin in CNS outcomes and mechanisms of insulin involvement across disorders of behavioural inflexibility.

A preliminary study of white matter correlates of a laboratory measure of attention and motor stability in attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is a complex behavioral disorder, often difficult and time consuming to diagnose. Laboratory assessment of ADHD-related constructs of attention and motor activity may be helpful in elucidating neurobiology; however, neuroimaging studies evaluating laboratory measures of ADHD are lacking. In this preliminary study, we assessed the association between fractional anisotropy (FA), a measure of white matter microstructure, and laboratory measures of attention and motor behavior using the QbTest, a widely used measure thought to improve clinician diagnostic confidence. This is the first look at neural correlates of this widely used measure. The sample included adolescents and young adults (ages 12-20, 35% female) with ADHD (n = 31) and without (n = 52). As expected, ADHD status was associated with motor activity, and cognitive inattention and impulsivity in the laboratory. With regard to MRI findings, laboratory observed motor activity and inattention were associated with greater FA in white matter regions of the primary motor cortex. All three laboratory observations were associated with lower FA in regions subserving fronto-striatal-thalamic and frontoparietal (i.e. superior longitudinal fasciculus) circuitry. Further, FA in white matter regions of the prefrontal cortex appeared to mediate the relationship between ADHD status and motor activity on the QbTest. These findings, while preliminary, suggest that performance on certain laboratory tasks is informative with regard to neurobiological correlates of subdomains of the complex ADHD phenotype. In particular, we provide novel evidence for a relationship between an objective measure of motor hyperactivity and white matter microstructure in motor and attentional networks.

Effect of methylphenidate on functional controllability: a preliminary study in medication-naïve children with ADHD

Methylphenidate (MPH) is the recommended first-line treatment for attention-deficit/hyperactivity disorder (ADHD). While MPH's mechanism of action as a dopamine and noradrenaline transporter blocker is well known, how this translates to ADHD-related symptom mitigation is still unclear. As functional connectivity is reliably altered in ADHD, with recent literature indicating dysfunctional connectivity dynamics as well, one possible mechanism is through altering brain network dynamics. In a double-blind, placebo-controlled MPH crossover trial, 19 medication-naïve children with ADHD underwent two functional MRI scanning sessions (one on MPH and one on placebo) that included a resting state scan and two inhibitory control tasks; 27 typically developing (TD) children completed the same protocol without medication. Network control theory, which quantifies how brain activity reacts to system inputs based on underlying connectivity, was used to assess differences in average and modal functional controllability during rest and both tasks between TD children and children with ADHD (on and off MPH) and between children with ADHD on and off MPH. Children with ADHD on placebo exhibited higher average controllability and lower modal controllability of attention, reward, and somatomotor networks than TD children. Children with ADHD on MPH were statistically indistinguishable from TD children on almost all controllability metrics. These findings suggest that MPH may stabilize functional network dynamics in children with ADHD, both reducing reactivity of brain organization and making it easier to achieve brain states necessary for cognitively demanding tasks.

Near-infrared spectroscopy in child and adolescent neurodevelopmental disorders

Near-infrared spectroscopy (NIRS) is a noninvasive optical technique that uses the near-infrared spectrum for functional neuroimaging by measuring oxygenation and hemodynamic changes in the cerebral cortex. The advantages of NIRS include its portability and ease of application, which allows for testing with the subject in natural positions, such as sitting or standing. Since 1994, NIRS has been increasingly used to conduct functional activation studies on different psychiatric disorders, most prominently schizophrenia, depression, bipolar disorder, and neurodevelopmental disorders. However, limited information on its use among child and adolescent patients is available. We herein review recent findings obtained using NIRS measurements of the brain during cognitive tasks in neurodevelopmental disorders, such as autism spectrum disorder, attention-deficit/hyperactivity disorder, obsessive-compulsive disorder, and Tourette's disorder. This will facilitate evaluations of the causation and treatment of prefrontal cortex dysfunctions.

Double-Blind, Sham-Controlled Randomized Trial Testing the Efficacy of fMRI Neurofeedback on Clinical and Cognitive Measures in Children With ADHD

OBJECTIVE

Functional MRI neurofeedback (fMRI-NF) could potentially be a novel, safe nonpharmacological treatment for attention deficit hyperactivity disorder (ADHD). A proof-of-concept randomized controlled trial of fMRI-NF of the right inferior frontal cortex (rIFC), compared to an active control condition, showed promising improvement of ADHD symptoms (albeit in both groups) and in brain function. However, comparison with a placebo condition in a larger trial is required to test efficacy.

METHODS

This double-blind, sham-controlled randomized controlled trial tested the effectiveness and efficacy of fMRI-NF of the rIFC on symptoms and executive functions in 88 boys with ADHD (44 each in the active and sham arms). To investigate treatment-related changes, groups were compared at the posttreatment and 6-month follow-up assessments, controlling for baseline scores, age, and medication status. The primary outcome measure was posttreatment score on the ADHD Rating Scale (ADHD-RS).

RESULTS

No significant group differences were found on the ADHD-RS. Both groups showed similar decreases in other clinical and cognitive measures, except for a significantly greater decrease in irritability and improvement in motor inhibition in sham relative to active fMRI-NF at the posttreatment assessment, covarying for baseline. There were no significant side effects or adverse events. The active relative to the sham fMRI-NF group showed enhanced activation in rIFC and other frontal and temporo-occipital-cerebellar self-regulation areas. However, there was no progressive rIFC upregulation, correlation with ADHD-RS scores, or transfer of learning.

CONCLUSIONS

Contrary to the hypothesis, the study findings do not suggest that fMRI-NF of the rIFC is effective in improving clinical symptoms or cognition in boys with ADHD.

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.

A Case Study on EEG Analysis: Embedding Entropy Estimations Indicate the Decreased Neuro-Cortical Complexity Levels Mediated by Methylphenidate Treatment in Children with ADHD

Objective: Complexity analysis is a method employed to understand the activity of the brain. The effect of methylphenidate (MPH) treatment on neuro-cortical complexity changes is still unknown. This study aimed to reveal how MPH treatment affects the brain complexity of children with attention deficit hyperactivity disorder (ADHD) using entropy-based quantitative EEG analysis. Three embedding entropy approaches were applied to short segments of both pre- and post- medication EEG series. EEG signals were recorded for 25 boys with combined type ADHD prior to the administration of MPH and at the end of the first month of the treatment. Results: In comparison to Approximate Entropy (ApEn) and Sample Entropy (SampEn), Permutation Entropy (PermEn) provided the most sensitive estimations in investigating the impact of MPH treatment. In detail, the considerable decrease in EEG complexity levels were observed at six cortical regions (F3, F4, P4, T3, T6, O2) with statistically significant level (p < .05). As well, PermEn provided the most meaningful associations at central lobes as follows: 1) The largeness of EEG complexity levels was moderately related to the severity of ADHD symptom detected at pre-treatment stage. 2) The percentage change in the severity of opposition as the symptom cluster was moderately reduced by the change in entropy. Conclusion: A significant decrease in entropy levels in the frontal region was detected in boys with combined type ADHD undergoing MPH treatment at resting-state mode. The changes in entropy correlated with pre-treatment general symptom severity of ADHD and conduct disorder symptom cluster severity.

Neural Mechanisms Underlying the Effects of Novel Sounds on Task Performance in Children With and Without ADHD

Distractibility is one of the key features of attention deficit hyperactivity disorder (ADHD) and has been associated with alterations in the neural orienting and alerting networks. Task-irrelevant stimuli are thus expected to have detrimental effects on the performance of patients with ADHD. However, task-irrelevant presentation of novel sounds seems to have the opposite effect and improve subsequent attentional performance particularly in patients with ADHD. Here, we aimed to understand the neural modulations of the attention networks underlying these improvements. Fifty boys (25 with ADHD) participated in a functional magnetic resonance imaging (fMRI) study in which unique (novel) or repeatedly presented (familiar) sounds were placed before a visual flanker task in 2/3 of the trials. We found that presenting any sound improved task performance in all participants, but the underlying neural mechanisms differed for the type of sound. Familiar sounds led to a stronger increase in activity in the left posterior insula in patients with ADHD compared to typically developing peers. Novel sounds led to activations of the fronto-temporoparietal ventral attention network, likewise in ADHD and TD. These changes in signaling by novelty in the right inferior frontal gyrus were directly related to improved response speed showing that neural orienting network activity following novel sounds facilitated subsequent attentional performance. This mechanism of behavioral enhancement by short distractions could potentially be useful for cognitive trainings or homework situations.

Dorsal-to-ventral imbalance in the superior longitudinal fasciculus mediates methylphenidate's effect on beta oscillations in ADHD

While pharmacological treatment with methylphenidate (MPH) is a first line intervention for ADHD, its mechanisms of action have yet to be elucidated. We here seek to identify the white matter tracts that mediate MPH's effect on beta oscillations. We implemented a double-blind placebo-controlled crossover design, where boys diagnosed with ADHD underwent behavioral and MEG measurements during a spatial attention task while on and off MPH. The results were compared with an age/IQ-matched control group. Estimates of white matter tracts were obtained using diffusion tensor imaging (DTI). Via a stepwise model selection strategy, we identified the fiber tracts (regressors) significantly predicting values of the dependent variables of interest (i.e., oscillatory power, behavioral performance, and clinical symptoms): the anterior thalamic radiation (ATR), the superior longitudinal fasciculus ("parietal endings") (SLFp), and superior longitudinal fasciculus ("temporal endings") (SLFt). ADHD symptoms severity was associated with lower fractional anisotropy (FA) within the ATR. In addition, individuals with relatively higher FA in SLFp compared to SLFt, led to stronger behavioral effects of MPH in the form of faster and more accurate responses. Furthermore, the same parietotemporal FA gradient explained the effects of MPH on beta modulation: subjects with ADHD exhibiting higher FA in SLFp compared to SLFt also displayed greater effects of MPH on beta power during response preparation. Our data suggest that the behavioral deficits and aberrant oscillatory modulations observed in ADHD depend on a possibly detrimental structural connectivity imbalance within the SLF, caused by a diffusivity gradient in favor of parietal rather than temporal, fiber tracts.

Meta-analysis: Dose-Dependent Effects of Methylphenidate on Neurocognitive Functioning in Children With Attention-Deficit/Hyperactivity Disorder

OBJECTIVE

Neurocognitive deficits are at the heart of explanatory models of attention-deficit/hyperactivity disorder (ADHD), and lead to significant impairments in daily life. Determining the dosing effects of methylphenidate (MPH) on a broad range of neurocognitive functions and investigating possible impairing effects of high doses is therefore important.

METHOD

Placebo-controlled trials were included that investigated MPH dosing effects on neurocognitive functions in children and adolescents (aged 5-18 years) diagnosed with ADHD. Effect sizes (standardized mean differences [SMDs]) were calculated for different neurocognitive functions (baseline speed, variability in responding, nonexecutive memory and executive memory, inhibitory control, and cognitive flexibility) and, if available, for ADHD symptoms. Meta-regression analysis were used to investigate linear effects of dose (mg/kg/dose), and separate meta-analyses compared SMDs for 3 MPH dose ranges: low (0.10-0.30 mg/kg/dose), medium (0.31-0.60 mg/kg/dose), and high (0.61-1.00 mg/kg/dose).

RESULTS

A total of 31 studies fulfilled inclusion criteria, comprising 804 children with ADHD. Methylphenidate had beneficial effects on all neurocognitive functions (d = 0.20-0.73). Significant linear dosing effects were found for ADHD symptoms and lower-order neurocognitive functions (baseline speed, variability in responding, nonexecutive memory), with greater enhancement of functioning with increasing dose. No dosing effects were found for higher-order neurocognitive functions (executive memory, inhibitory control, and cognitive flexibility). No detrimental effects of MPH were found on any of the investigated functions.

CONCLUSION

Methylphenidate was superior to placebo in improving ADHD symptoms and a broad range of neurocognitive functions; however, effects sizes regarding the effects of dose vary substantially between functions. Our data highlight the importance of considering both neurocognitive and symptomatic aspects of ADHD in clinical practice.

Two sides of the same coin: ADHD affects reactive but not proactive inhibition in children

Children with attention-deficit/hyperactivity disorder (ADHD) present a deficit in inhibitory control. Still, it remains unclear whether it comes from a deficit in reactive inhibition (ability to stop the action in progress), proactive inhibition (ability to exert preparatory control), or both.We compared the performance of 39 children with ADHD and 42 typically developing children performing a Simon choice reaction time task. The Simon task is a conflict task that is well-adapted to dissociate proactive and reactive inhibition. Beyond classical global measures (mean reaction time, accuracy rate, and interference effect), we used more sophisticated dynamic analyses of the interference effect and accuracy rate to investigate reactive inhibition. We studied proactive inhibition through the congruency sequence effect (CSE).Our results showed that children with ADHD had impaired reactive but not proactive inhibition. Moreover, the deficit found in reactive inhibition seems to be due to both a stronger impulse capture and more difficulties in inhibiting impulsive responses. These findings contribute to a better understanding of how ADHD affects inhibitory control in children.

Meta-analysis of structural and functional alterations of brain in patients with attention-deficit/hyperactivity disorder

BACKGROUND

A large and growing body of neuroimaging research has concentrated on patients with attention-deficit/hyperactivity disorder (ADHD), but with inconsistent conclusions. This article was intended to investigate the common and certain neural alterations in the structure and function of the brain in patients with ADHD and further explore the differences in brain alterations between adults and children with ADHD.

METHODS

We conducted an extensive literature search of whole-brain voxel-based morphometry (VBM) and functional magnetic resonance imaging (fMRI) studies associated with ADHD. Two separate meta-analyses with the seed-based d mapping software package for functional neural activation and gray matter volume (GMV) were carried out, followed by a joint analysis and a subgroup analysis.

RESULTS

This analysis included 29 VBM studies and 36 fMRI studies. Structurally, VBM analysis showed that the largest GMV diminutions in patients with ADHD were in several frontal-parietal brain regions, the limbic system, and the corpus callosum. Functionally, fMRI analysis discovered significant hypoactivation in several frontal-temporal brain regions, the right postcentral gyrus, the left insula, and the corpus callosum.

CONCLUSION

This study showed that abnormal alterations in the structure and function of the left superior frontal gyrus and the corpus callosum may be the key brain regions involved in the pathogenesis of ADHD in patients and may be employed as an imaging metric for patients with ADHD pending future research. In addition, this meta-analysis discovered neuroanatomical or functional abnormalities in other brain regions in patients with ADHD as well as findings that can be utilized to guide future research.

Effects of methylphenidate on executive functioning in children and adolescents with ADHD after long-term use: a randomized, placebo-controlled discontinuation study

BACKGROUND

Methylphenidate may improve executive functioning in children with attention-deficit/hyperactivity disorder (ADHD). However, it is unclear if there are still acute effects of methylphenidate on executive functioning after long-term use.

METHODS

In a randomized double-blind, placebo-controlled discontinuation study, 94 children and adolescents (ages 8-18 years) who used methylphenidate beyond two years were either assigned to seven weeks of continued treatment with 36 or 54 mg of extended-release methylphenidate or to gradual withdrawal over three weeks to placebo for four weeks. Performance on neuropsychological tasks, measuring working memory, response inhibition, attentional flexibility and psychomotor speed was compared between both groups using mixed models for repeated measures. Additionally, we investigated within the discontinuation group if a deterioration on the investigator-rated Clinical Global Impressions Improvement scale after withdrawing to placebo was related to a worse performance on the neuropsychological tasks. This study was registered in the Netherlands Trial Register (www. Trialregister.nl) with identifier 5252.

RESULTS

After withdrawal of methylphenidate, the discontinuation group made more errors on working memory (β = -1.62, SD = 0.56, t = -2.88, p = .01, Cohen's f2 = .14), independent from reaction time compared to baseline, in contrast to the continuation group. We did not find differences in changes in response inhibition, attentional flexibility and psychomotor speed between the two groups. Also, there were no significant differences in task measures between the participants who deteriorated clinically and those who did not.

CONCLUSIONS

Our study shows that methylphenidate has a beneficial effect on working memory after two years of use. Future studies should explore whether cognitive outcomes may aid clinical decision-making on the continued use of methylphenidate, given dissociation between cognitive and behavioural effects of stimulant medication.

Resting state dynamic functional connectivity in children with attention deficit/hyperactivity disorder

Attention deficit/hyperactivity disorder (ADHD) is characterized by inattention, hyperactivity and impulsivity. In this study, we investigated group differences in dynamic functional connectivity (dFC) between 113 children with inattentive (46 ADHD_I) and combined (67 ADHD_C) ADHD and 76 typically developing (TD) children using resting-state functional MRI data. For dynamic connectivity analysis, the data were first decomposed into 100 independent components, among which 88 were classified into eight well-known resting-state networks (RSNs). Three discrete FC states were then identified using k-means clustering and used to estimate transition probabilities between states in both patient and control groups using a hidden Markov model. Our results showed state-dependent alterations in intra and inter-network connectivity in both ADHD subtypes in comparison with TD. Spending less time than healthy controls in state 1, both ADHD_Iand ADHD_Cwere characterized with weaker intra-hemispheric connectivity with functional asymmetries. In this state, ADHD_Ifurther showed weaker inter-hemispheric connectivity. The patients spent more time in state 2, exhibiting characteristic abnormalities in corticosubcortical and corticocerebellar connectivity. In state 3, a less frequently state observed across the ADHD and TD children, ADHD_Cwas differentiated from ADHD_Iby significant alterations in FC between bilateral temporal regions and other brain areas in comparison with TD. Across all three states, several strategic brain regions, mostly bilateral, exhibited significant alterations in both static functional connectivity (sFC) and dFC in the ADHD groups compared to TD, including inferior, middle and superior temporal gyri, middle frontal gyri, insula, anterior cingulum cortex, precuneus, calcarine, fusiform, superior motor area, and cerebellum. Our results show distributed abnormalities in sFC and dFC between different large-scale RSNs including cortical and subcortical regions in both ADHD subtypes compared to TD. Our findings show that the dynamic changes in brain FC can better explain the underlying pathophysiology of ADHD such as deficits in visual cognition, attention, memory and emotion processing, and cognitive and motor control.

Exposure to methylphenidate during peri-adolescence decouples the prefrontal cortex: a multimodal MRI study

This study was designed to assess the effects of daily psychostimulant exposure during juvenility and peri-adolescence on brain morphology and functional connectivity using multimodal magnetic resonance imaging. We hypothesized that long-term exposure to methylphenidate would enhance connectivity with the prefrontal cortex. Male rats were given daily injections of either methylphenidate (n=10), dextroamphetamine (n=10) or saline vehicle (n=10) from postnatal day 21 to 42. They were imaged between postnatal day 43 and 48. Voxel-based morphometry, diffusion weighted imaging, and resting state functional connectivity were used to quantify brain structure and function. Images from each modality were registered and analyzed, using a 3D MRI rat atlas providing site-specific data over 171 different brain areas. Following imaging, rats were tested for cognitive function using novel object preference. Long-lasting psychostimulant treatment was associated with only a few significant changes in brain volume and measures of anisotropy compared to vehicle. Resting state functional connectivity imaging revealed decreased coupling between the prefrontal cortex, basal ganglia and sensory motor cortices. There were no significant differences between experimental groups for cognitive behavior. In this exploratory study, we showed that chronic psychostimulant treatment throughout juvenility and preadolescence has a minimal effect on brain volume and gray matter microarchitecture, but significantly uncouples the connectivity in the cerebral/basal ganglia circuitry.

Visualizing Neuropharmacological Effects of Guanfacine Extended Release in Attention Deficit Hyperactivity Disorder Using Functional Near-Infrared Spectroscopy

Objective: In the current study, we explored the neural substrate for acute effects of guanfacine extended release (GXR) on inhibitory control in school-aged children with attention deficit hyperactivity disorder (ADHD), using functional near-infrared spectroscopy (fNIRS). Methods: Following a GXR washout period, 12 AD HD children (6-10 years old) performed a go/no-go task before and 3 h after GXR or placebo administration, in a randomized, double-blind, placebo-controlled, crossover design study. In the primary analysis, fNIRS was used to monitor the right prefrontal cortical hemodynamics of the participants, where our former studies showed consistent dysfunction and osmotic release oral system-methylphenidate (OROS-MPH) and atomoxetine hydrochloride (ATX) elicited recovery. We examined the inter-medication contrast, comparing the effect of GXR against the placebo. In the exploratory analysis, we explored neural responses in regions other than the right prefrontal cortex (PFC). Results: In the primary analysis, we observed no significant main effects or interactions of medication type and age in month (two-way mixed ANCOVA, Fs < 0.20, all ps > .05). However, in the post-hoc analysis, we observed significant change in the oxy-Hb signal in the right angular gyrus (AG) for inter-medication (one sample t-test, p < 0.05, uncorrected, Cohen's d = 0.71). Conclusions: These results are different from the neuropharmacological effects of OROS-MPH and ATX, which, in an upregulated manner, reduced right PFC function in ADHD children during inhibitory tasks. This analysis, while limited by its secondary nature, suggested that the improved cognitive performance was associated with activation in the right AG, which might serve as a biological marker to monitor the effect of GXR in the ADHD children.

Differential response to pharmacological intervention in ADHD furthers our understanding of the mechanisms of interference control

The deficit in "interference control" found in children with Attention Deficit Hyperactivity Disorder (ADHD) could be due to two distinct processes, which are not disentangled in most studies: a larger susceptibility to activating prepotent response impulses and a deficit in suppressing them. Here, we investigated the effect of 1/ADHD and 2/ methylphenidate (MPH), on these two components of interference control. We compared interference control between untreated children with ADHD, children with ADHD under MPH, and typically developing children performing a Simon task. The main findings were that 1/ children with ADHD were more susceptible to reacting impulsively and less efficient at suppressing impulsive actions, and 2/ MPH improved the selective inhibition of impulsive actions but did not modify the strength of response impulse. This work provides an example of how pharmacological interventions and selective responses to them can be used to investigate and further our understanding of cognitive processing.

Quantitative EEG in Childhood Attention Deficit Hyperactivity Disorder and Learning Disabilities

The clinical use of the quantitative EEG (QEEG) from the pioneering work of John has received a new impetus thanks to new neuroimaging techniques and the possibility of using a number of normative databases both of normal subjects and of subjects with definite pathologies. In this direction, the term personalized medicine is becoming more and more common, a medical procedure that separates patients into different groups based on their predicted response to the quantitative EEG. This has allowed the study of single subjects and to customize health care, with decisions and treatments tailored to each individual patient, as well as improvement of knowledge of the pathophysiological mechanisms of specific diseases. This review article will present the most recent evidence in the field of developmental neuropsychiatric disorders obtained from the application of quantitative EEG both in clinical group studies (attention deficit hyperactivity disorder, developmental dyslexia, oppositional defiant disorder) and in individual case studies not yet published.

Regional brain volume predicts response to methylphenidate treatment in individuals with ADHD

BACKGROUND

Despite the effectiveness of methylphenidate for treating ADHD, up to 30% of individuals with ADHD show poor responses to methylphenidate. Neuroimaging biomarkers to predict medication responses remain elusive. This study characterized neuroanatomical features that differentiated between clinically good and poor methylphenidate responders with ADHD.

METHODS

Using a naturalistic observation design selected from a larger cohort, we included 79 drug-naive individuals (aged 6-42 years) with ADHD without major psychiatric comorbidity, who had acceptable baseline structural MRI data quality. Based on a retrospective chart review, we defined responders by individuals' responses to at least one-month treatment with methylphenidate. A nonparametric mass-univariate voxel-based morphometric analysis was used to compare regional gray matter volume differences between good and poor responders. A multivariate pattern recognition based on the support vector machine was further implemented to identify neuroanatomical indicators to predict an individual's response.

RESULTS

63 and 16 individuals were classified in the good and poor responder group, respectively. Using the small-volume correction procedure based on the hypothesis-driven striatal and default-mode network masks, poor responders had smaller regional volumes of the left putamen as well as larger precuneus volumes compared to good responders at baseline. The machine learning approach identified that volumetric information among these two regions alongside the left frontoparietal regions, occipital lobes, and posterior/inferior cerebellum could predict clinical responses to methylphenidate in individuals with ADHD.

CONCLUSION

Our results suggest regional striatal and precuneus gray matter volumes play a critical role in mediating treatment responses in individuals with ADHD.

Structural and Functional Brain Abnormalities in Internet Gaming Disorder and Attention-Deficit/Hyperactivity Disorder: A Comparative Meta-Analysis

Background: Patients with Internet gaming disorder (IGD) and attention-deficit/hyperactivity disorder (ADHD) have high comorbidity but it is still unknown whether these disorders have shared and distinctive neuroimage alterations. Objective: The aim of this meta-analysis was to identify shared and disorder-specific structural, functional, and multimodal abnormalities between IGD and ADHD. Methods: A systematic literature search was conducted for whole-brain voxel-based morphometry (VBM) and functional magnetic resonance imaging (fMRI) studies comparing people with IGD or ADHD with healthy controls. Regional gray matter volume (GMV) and fMRI differences were compared over the patient groups and then a quantitative comparison was performed to find abnormalities (relative to controls) between IGD and ADHD using seed-based d mapping meta-analytic methods. Result: The meta-analysis contained 14 IGD VBM studies (contrasts covering 333 IGDs and 335 HCs), 26 ADHD VBM studies (1,051 patients with ADHD and 887 controls), 30 IGD fMRI studies (603 patients with IGD and 564 controls), and 29 ADHD fMRI studies (878 patients with ADHD and 803 controls). Structurally, VBM analysis showed disorder-specific GMV abnormality in the putamen among IGD subjects and orbitofrontal cortex in ADHD and shared GMV in the prefrontal cortex. Functionally, fMRI analysis discovered that IGD-differentiating increased activation in the precuneus and shared abnormal activation in anterior cingulate cortex, insular, and striatum. Conclusion: IGD and ADHD have shared and special structural and functional alterations. IGD has disorder-differentiating structural alterations in the putamen and ADHD has alterations in the orbitofrontal cortex. Disorder-differentiating fMRI activations were predominantly observed in the precuneus among IGD subjects and shared impairing function connection was in the rewards circuit (including ACC, OFC, and striatum).

Frontostriatal White Matter Integrity Relations with "Cool" and "Hot" Self-Regulation after Pediatric Traumatic Brain Injury

Traumatic brain injury (TBI) produces microstructural damage to white matter pathways connecting neural structures in pre-frontal and striatal regions involved in self-regulation (SR). Dorsal and ventral frontostriatal pathways have been linked to cognitive ("cool") and emotional ("hot") SR, respectively. We evaluated the relation of frontostriatal pathway fractional anisotropy (FA) 2 months post-TBI on cool and hot SR assessed 7 months post-TBI. Participants were 8-15 years of age, including children with uncomplicated mild TBI (mTBI; n = 24), more severe TBI (complicated-mild, moderate, severe [cms]TBI; n = 60), and typically developing (TD) children (n = 55). Diffusion tensor tractography was used to map frontostriatal pathways. Cool SR included focused and sustained attention performance, and parent-reported attention, whereas hot SR included risk-taking performance and parent-reported emotional control. Multivariate general linear models showed that children with cmsTBI had greater parent-reported cool and hot SR difficulties and lower dorsal and ventral FA than TD children. Focused attention, risk taking, and emotional control correlated with FA of specific dorsal and ventral pathways; however, only the effect of TBI on focused attention was mediated by integrity of dorsal pathways. Results suggest that frontostriatal FA may serve as a biomarker of risk for SR difficulties or to assess response to interventions targeting SR in pediatric TBI and in broader neurodevelopmental populations.

Methylphenidate challenge test in adults with attention deficit/hyperactivity disorder (ADHD): Clinical effects and their predictors

OBJECTIVE

Adult and children attention deficit/hyperactivity disorder (ADHD) share similar symptoms and responses to drugs such as methylphenidate (MPH). Yet, in Europe, these drugs remain unlicensed for adults. We aimed to assess the effects of an acute MPH challenge on the four dimensions concentration, impulsivity, tension, and general well-being in ADHD adults, and identify predictors of improvement.

METHODS

Therapeutic Drug Monitoring was performed to measure MPH plasma levels. A Visual Analogue Scale was administered to patients before and after the acute MPH challenge to measure self-reported changes in the four dimensions.

RESULTS

After the acute MPH challenge, our 71 patients showed significant improvement in concentration and tension. The MPH challenge dose correlated with lower patients' age, greater side effects, increased concentration (p = .008) and decreased tension (p = .001). At multiple linear regression MPH plasma levels and absence of postdose side effects predicted concentration improvement, MPH plasma levels predicted tension improvement. MPH plasma levels were significantly higher in patients who reported an improvement in concentration, tension, and impulsivity compared to nonimprovers (p's from .001 to .004).

CONCLUSIONS

These findings point to the efficacy of MPH challenge in improving concentration and tension in adult ADHD, thus emphasizing the need for a broader treatment access for these patients.

Increased left inferior fronto-striatal activation during error monitoring after fMRI neurofeedback of right inferior frontal cortex in adolescents with attention deficit hyperactivity disorder

Attention Deficit/Hyperactivity Disorder (ADHD) is a self-regulation disorder, with impairments in error monitoring associated with underactivation of the related brain network(s). Psychostimulant medication improves ADHD symptoms and can upregulate brain function, but has side effects, with limited evidence for longer-term effects. Real-time functional magnetic resonance neurofeedback (fMRI-NF) has potential longer-term neuroplastic effects. We previously reported the effects of 11 runs of 8.5 min of fMRI-NF of the right inferior frontal cortex (rIFC) in adolescents with ADHD. This resulted in improvement of clinical symptom and enhanced rIFC activation post-pre treatment during response inhibition, when compared to a control group receiving fMRI-NF of the left parahippocampal gyrus (lPHG). In the current study we applied a novel analysis to the existing data by investigating the effects of fMRI-NF of rIFC in 16 adolescents with ADHD compared to fMRI-NF of lPHG in 11 adolescents with ADHD on the neurofunctional correlates of error monitoring during the same fMRI tracking stop task and potential associations with cognitive and clinical measures. We found stronger performance adjustment to errors in the rIFC-NF compared to the control lPHG-NF group. At the brain function level, fMRI-NF of rIFC compared to that of lPHG was associated with increased activation in error monitoring regions of the left IFC, premotor cortex, insula and putamen. The increased activation in left IFC-insular-striatal error monitoring regions in the rIFC-NF relative to the lPHG-NF group was furthermore trend-wise correlated with NF-induced ADHD symptom improvements. The findings of this study show, that during error monitoring, fMRI-NF training of rIFC upregulation elicited improvement in post-error behavioural adjustments and concomitant increased activation in left hemispheric fronto-insular-striatal and premotor regions mediating self-control and self-monitoring functions. This suggests that the administration of fMRI-NF of the rIFC may have had an impact on wider networks of self-regulation and self-monitoring in adolescents with ADHD.

Comparative meta-analyses of brain structural and functional abnormalities during cognitive control in attention-deficit/hyperactivity disorder and autism spectrum disorder

BACKGROUND

People with attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) have abnormalities in frontal, temporal, parietal and striato-thalamic networks. It is unclear to what extent these abnormalities are distinctive or shared. This comparative meta-analysis aimed to identify the most consistent disorder-differentiating and shared structural and functional abnormalities.

METHODS

Systematic literature search was conducted for whole-brain voxel-based morphometry (VBM) and functional magnetic resonance imaging (fMRI) studies of cognitive control comparing people with ASD or ADHD with typically developing controls. Regional gray matter volume (GMV) and fMRI abnormalities during cognitive control were compared in the overall sample and in age-, sex- and IQ-matched subgroups with seed-based d mapping meta-analytic methods.

RESULTS

Eighty-six independent VBM (1533 ADHD and 1295 controls; 1445 ASD and 1477 controls) and 60 fMRI datasets (1001 ADHD and 1004 controls; 335 ASD and 353 controls) were identified. The VBM meta-analyses revealed ADHD-differentiating decreased ventromedial orbitofrontal (z = 2.22, p < 0.0001) but ASD-differentiating increased bilateral temporal and right dorsolateral prefrontal GMV (zs ⩾ 1.64, ps ⩽ 0.002). The fMRI meta-analyses of cognitive control revealed ASD-differentiating medial prefrontal underactivation but overactivation in bilateral ventrolateral prefrontal cortices and precuneus (zs ⩾ 1.04, ps ⩽ 0.003). During motor response inhibition specifically, ADHD relative to ASD showed right inferior fronto-striatal underactivation (zs ⩾ 1.14, ps ⩽ 0.003) but shared right anterior insula underactivation.

CONCLUSIONS

People with ADHD and ASD have mostly distinct structural abnormalities, with enlarged fronto-temporal GMV in ASD and reduced orbitofrontal GMV in ADHD; and mostly distinct functional abnormalities, which were more pronounced in ASD.

Auditory and Visual Executive Functions in Children and Response to Methylphenidate: A Randomized Controlled Trial

Objectives: The aim of the study was to assess auditory and visually based executive functions (EFs) and the effect of methylphenidate (MPH) in children with ADHD. Methods: Thirty-six boys between the ages of 8.3 and 9.7 years with ADHD and 36 matched controls were included. The study group was randomized into MPH and placebo for 7 days each in a crossover design. A Cued Choice Reaction Time (CCRT) test that included incongruent cuing was administered at baseline and following 1 and 2 weeks. Results: The difference between the study and control groups was more evident with visual cues and incongruent cuing. Increased gains by children with predominantly hyperactive-impulsive\combined (HI\C) type of ADHD were observed under MPH. Conclusions: The differences between children with ADHD and typical children are more pronounce under incongruent auditory cuing . The gains attributable to MPH are more specific to tasks involving auditory and visual EFs and in children with HI\C type ADHDs.

CK1δ over-expressing mice display ADHD-like behaviors, frontostriatal neuronal abnormalities and altered expressions of ADHD-candidate genes

The cognitive mechanisms underlying attention-deficit hyperactivity disorder (ADHD), a highly heritable disorder with an array of candidate genes and unclear genetic architecture, remain poorly understood. We previously demonstrated that mice overexpressing CK1δ (CK1δ OE) in the forebrain show hyperactivity and ADHD-like pharmacological responses to D-amphetamine. Here, we demonstrate that CK1δ OE mice exhibit impaired visual attention and a lack of D-amphetamine-induced place preference, indicating a disruption of the dopamine-dependent reward pathway. We also demonstrate the presence of abnormalities in the frontostriatal circuitry, differences in synaptic ultra-structures by electron microscopy, as well as electrophysiological perturbations of both glutamatergic and GABAergic transmission, as observed by altered frequency and amplitude of mEPSCs and mIPSCs. Furthermore, gene expression profiling by next-generation sequencing alone, or in combination with bacTRAP technology to study specifically Drd1a versus Drd2 medium spiny neurons, revealed that developmental CK1δ OE alters transcriptional homeostasis in the striatum, including specific alterations in Drd1a versus Drd2 neurons. These results led us to perform a fine molecular characterization of targeted gene networks and pathway analysis. Importantly, a large fraction of 92 genes identified by GWAS studies as associated with ADHD in humans are significantly altered in our mouse model. The multiple abnormalities described here might be responsible for synaptic alterations and lead to complex behavioral abnormalities. Collectively, CK1δ OE mice share characteristics typically associated with ADHD and should represent a valuable model to investigate the disease in vivo.

Methylphenidate and atomoxetine normalise fronto-parietal underactivation during sustained attention in ADHD adolescents

Problems with sustained attention are a key clinical feature of Attention Deficit/Hyperactivity Disorder (ADHD) which also manifests in poor performance and abnormal fronto-striato-parietal activation during sustained attention. Methylphenidate and atomoxetine improve attention functions and upregulate abnormal fronto-cortical activation during executive function tasks in ADHD patients. Despite this, no functional Magnetic Resonance Imaging (fMRI) study has compared the effects of methylphenidate and atomoxetine on the neurofunctional substrates of sustained attention in ADHD. This randomised, double-blind, placebo-controlled, cross-over study investigated the comparative normalisation effects of methylphenidate and atomoxetine on fMRI correlates and performance in 14 ADHD adolescents relative to 27 age-matched healthy controls during a parametric sustained attention/vigilance task with progressively increasing load of sustained attention. ADHD patients were scanned three times under a single clinical dose of either methylphenidate, atomoxetine, or placebo in pseudo-randomised order. Healthy controls were scanned once and compared to patients under each drug condition to test for potential drug-normalisation effects. Relative to controls, ADHD boys under placebo were impaired in performance and had underactivation in predominantly right-hemispheric fronto-parietal, and striato-thalamic regions. Both drugs normalised all underactivations, while only methylphenidate improved performance deficits. Within patients, methylphenidate had a drug-specific effect of upregulating left ventrolateral prefrontal/superior temporal activation relative to placebo and atomoxetine, while both drugs increased activation of right middle/superior temporal cortex, posterior cingulate, and precuneus relative to placebo. The study shows shared normalisation effects of methylphenidate and atomoxetine on fronto-striato-thalamo-parietal dysfunction in ADHD during sustained attention but a drug-specific upregulation effects of methylphenidate on ventral fronto-temporal regions.

Receptor and circuit mechanisms underlying differential procognitive actions of psychostimulants

Psychostimulants, including methylphenidate (MPH), improve cognitive processes dependent on the prefrontal cortex (PFC) and extended frontostriatal circuitry. In both humans and animals, systemic MPH improves certain cognitive processes, such as working memory, in a narrow inverted-U-shaped manner. In contrast, other processes, including attention-related, are improved over a broader/right-shifted dose range. The current studies sought to elucidate the potential circuit and receptor mechanisms underlying the divergent dose-dependent procognitive effects of psychostimulants. We first observed that, as with working memory, although sustained attention testing was highly dependent on multiple frontostriatal regions, only MPH infusion into the dorsomedial PFC improved task performance. Importantly, the dose-response curve for this action was right-shifted relative to working memory, as seen with systemic administration. Additional studies examined the receptor mechanisms within the PFC associated with the procognitive actions of MPH across working memory and sustained attention tasks. We observed that PFC α2 and D1 receptors contributed to the beneficial effects of MPH across both cognitive tasks. However, α1 receptors only contributed to MPH-induced improvement in sustained attention. Moreover, activation of PFC α1 receptors was sufficient to improve sustained attention. This latter action contrasts with the impairing actions of PFC α1 receptors reported previously for working memory. These results provide further evidence for a prominent role of the PFC in the procognitive actions of MPH and demonstrate the divergent dose sensitivity across cognitive processes aligns with the differential involvement of PFC α1 receptors.

Effects of neurofeedback versus methylphenidate for the treatment of ADHD: systematic review and meta-analysis of head-to-head trials

BACKGROUND

The comparative efficacy and tolerability of methylphenidate (MPH) and neurofeedback (NF) in individuals with attention-deficit/hyperactivity disorder (ADHD) remains uncertain. This study aimed to fill this gap by means of a systematic review/meta-analysis.

METHODS

PubMed, OVID, ERIC, Web of Science, ClinialTrials.gov and a set of Chinese databases were searched until 22 August 2018. Standardised mean differences (SMD) were pooled using comprehensive meta-analysis software.

RESULTS

18 randomised controlled trials (RCTs) were included (778 individuals with ADHD in the NF arm and 757 in the MPH group, respectively; 13 studies in Chinese, five in English). At the study first endpoint, MPH was significantly more efficacious than NF on ADHD core symptoms (ADHD symptoms combined: SMD=-0.578, 95% CI (-1.063 to -0.092)) and on two neuropsychological parameters (inattention:-0.959 (-1.711 to -0.208); inhibition:-0.469 (-0.872 to -0.066)). Dropouts were significantly lower in NF versus MPH (OR=0.412, 0.186 to 0.913). Results were robust to sensitivity analyses, with two important exceptions: removing Chinese studies and non-funded studies, no differences emerged between MPH and NF, although the number of studies was small. At the study follow-up, MPH was superior to NF in some outcomes, but results were inconsistent across raters.

CONCLUSIONS

Due to the risk of bias of included studies, the results of the sensitivity analysis excluding Chinese and non-funded studies, and the mixed findings on at the follow-up endpoint, further high quality studies are needed to assess the comparative efficacy and acceptability of NF and MPH in individuals with ADHD.

TRIAL REGISTRATION NUMBER

CRD42018090256.

Reduced Prefrontal Gyrification in Carriers of the Dopamine D4 Receptor 7-Repeat Allele With Attention Deficit/Hyperactivity Disorder: A Preliminary Report

Objective: Structural and functional abnormalities have been noted in the prefrontal cortex of individuals with neurodevelopmental disorders such as attention deficit/hyperactivity disorder (ADHD). Cortical thickness and gyrification, both of which have been reported as abnormal in the prefrontal cortex in ADHD, are thought to be modulated by genetic influences during neural development. This study aimed to investigate the effects of a polymorphism of the dopamine DRD4 gene (the 7-repeat (7R) "risk" allele) on thickness and gyrification as distinct parameters of prefrontal cortical structure in children with ADHD. Method: Structural images and genetic samples were obtained from 49 children aged 9-15 years (25 with ADHD and 24 matched controls), and measures of cortical thickness and gyrification for inferior, middle, and superior frontal cortex were calculated. Results: A significant interaction between diagnosis and genotype on prefrontal gyrification was observed, largely driven by reduced inferior frontal gyrification in patients who carried the DRD4 7R allele. Furthermore, inferior frontal gyrification-but not thickness-related to everyday executive functioning in 7R allele carriers across groups. Conclusions: Prefrontal gyrification is reduced in children with ADHD who also carry the DRD4 7R allele, and it relates to critical functional skills in the executive domain in carriers of the risk allele. More broadly, these effects highlight the importance of considering precise neurodevelopmental mechanisms through which risk alleles influence cortical neurogenesis and migration.

Understanding the neural mechanisms of lisdexamfetamine dimesylate (LDX) pharmacotherapy in Binge Eating Disorder (BED): a study protocol

BACKGROUND

The efficacy and safety of Lisdexamfetamine dimesylate (LDX) in the treatment of moderate to severe binge eating disorder (BED) has been demonstrated in multiple randomised clinical trials. Despite this, little is known about how LDX acts to improve binge eating symptoms. This study aims to provide a comprehensive understanding of the neural mechanisms by which LDX improves symptoms of BED. We hypothesise that LDX will act by normalising connectivity within neural circuits responsible for reward and impulse control, and that this normalisation will correlate with reduced binge eating episodes.

METHODS

This is an open-label Phase 4 clinical trial of LDX in adults with moderate to severe BED. Enrolment will include 40 adults with moderate to severe BED aged 18-40 years and Body Mass Index (BMI) of 20-45 kg/m², and 22 healthy controls matched for age, gender and BMI. Clinical interview and validated scales are used to confirm diagnosis and screen for exclusion criteria, which include comorbid anorexia nervosa or bulimia nervosa, use of psychostimulants within the past 6 months, and current use of antipsychotics or noradrenaline reuptake inhibitors. Baseline assessments include clinical symptoms, multimodal neuroimaging, cognitive assessment of reward sensitivity and behavioural inhibition, and an (optional) genetic sample. A subset of these assessments are repeated after eight weeks of treatment with LDX titrated to either 50 or 70 mg. The primary outcome measures are resting-state intrinsic connectivity and the number of binge eating episodes. Analyses will be applied to resting-state fMRI data to characterise pharmacological effects across the functional connectome, and assess correlations with symptom measure changes. Comparison of neural measures between controls and those with BED post-treatment will also be performed to determine whether LDX normalises brain function.

DISCUSSION

First enrolment was in May 2018, and is ongoing. This study is the first comprehensive investigation of the neurobiological changes that occur with LDX treatment in adults with moderate to severe BED.

TRIAL REGISTRATION

ACTRN12618000623291, Australian and New Zealand Clinical Trials Registry URL: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=374913&isReview=true. Date of Registration: 20 April 2018.

The Effect of Methylphenidate on the Hearing of Children with Attention Deficit Hyperactivity Disorder

Introduction  There has been a sudden idiopathic hearing loss case presented after methylphenidate treatment in a child with attention deficit hyperactivity disorder (ADHD). Objective  This study was performed to reveal the probable ototoxic side effects of methylphenidate use in patients with ADHD. Methods  Thirty pediatric patients with ADHD were included in the study. Pure tone audiometry, speech discrimination scores, waves I, III, V absolute latencies and waves I-III, I-V, III-V interpeak latencies at the 80 dB nHL intensity after click stimulus auditory brainstem response (ABR) results were compared before and 3 months after methylphenidate treatment. Results  There were no statistically significant difference between pretreatment and posttreatment pure tone and speech audiometry findings and ABR results (p > 0.05 for all parameters). Conclusion  Methylphenidate can be regarded as a safe drug regarding ototoxic side effects. Additional studies with a larger sample size and longer follow-up may be needed.

Reduced prefrontal hemodynamic response in adult attention-deficit hyperactivity disorder as measured by near-infrared spectroscopy

AIM

Recent developments in near-infrared spectroscopy (NIRS) have enabled non-invasive clarification of brain functions in psychiatric disorders. In pediatric attention-deficit hyperactivity disorder (ADHD), reduced prefrontal hemodynamic responses have been observed with NIRS repeatedly. However, there are few studies of adult ADHD by multi-channel NIRS. Therefore, in this study, we used multi-channel NIRS to examine the characteristics of prefrontal hemodynamic responses during the Stroop Color-Word Task (SCWT) in adult ADHD patients and in age- and sex-matched control subjects.

METHODS

Twelve treatment-naïve adults with ADHD and 12 age- and sex-matched healthy control subjects participated in the present study after giving consent. We used 24-channel NIRS to measure the oxygenated hemoglobin (oxy-Hb) changes at the frontal lobes of participants during the SCWT. We compared the oxy-Hb changes between adults with ADHD and control subjects by t-tests with Bonferroni correction.

RESULTS

During the SCWT, the oxy-Hb changes observed in the ADHD group were significantly smaller than those in the control group in channels 11, 16, 18, 21, 22, 23, and 24, corresponding to the prefrontal cortex. At channels 16, 21, 23, and 24 of the ADHD group, there were negative correlations between the symptomatic severity and the oxy-Hb changes.

CONCLUSION

The present study suggests that adults with ADHD have reduced prefrontal hemodynamic response as measured by NIRS.

Functional Imaging Changes in the Medial Prefrontal Cortex in Adult ADHD

OBJECTIVE

Functional imaging studies have found reduced frontal activity, mainly in dorso/ventro-lateral regions and reduced task-related de-activation of the default mode network in childhood ADHD. Adult studies are fewer and inconclusive. We aimed to investigate the potential neural bases of executive function in ADHD adults, examining brain activity during N-back task performance, and to explore the potential corrective effects of long-term methylphenidate treatment.

METHOD

We recruited a large adult ADHD-combined sample and a matched control group and obtained functional magnetic resonance imaging (fMRI) images during task. ADHD participants were subdivided in a group under long-term treatment with methylphenidate (washed out for the scan) and a treatment-naive group.

RESULTS

ADHD participants showed deficient de-activation of the medial prefrontal cortex during 2-back task, implying default mode network dysfunction. We found no relationship between blunted de-activation and treatment history.

CONCLUSION

As de-activation failure in the medial frontal cortex is linked to lapses of attention, findings suggest a potential link to ADHD symptomatology.