Attention Deficit Hyperactivity Disorder, Cannabis Use, and the Endocannabinoid System: A Scoping Review.

There is emerging evidence that the endocannabinoid system (ECS) plays a significant role in the pathophysiology of many psychiatric disorders, including attention deficit hyperactivity disorder (ADHD). Increasing evidence suggests that a number of neurobiological correlates between endogenous cannabinoid function and cognitive dysfunction are seen in ADHD, making the ECS a possible target for therapeutic interventions. Cannabis use and cannabis use disorder are more prevalent in individuals with ADHD, compared to the general population, and there is growing popular perception that cannabis is therapeutic for ADHD. However, the relationship between cannabis use and ADHD symptomology is poorly understood. Further understanding of the role of the ECS in ADHD pathophysiology and the molecular alterations that may be a target for treatment is needed. To further the science on this emerging area of research, this scoping review describes the preclinical and clinical evidence seeking to understand the relationship between the ECS and ADHD.

Greater Frontoparietal Connectivity During Task Engagement Among Toddlers With Parent-Reported Inattention.

Attention-deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder with lifelong impairments. ADHD-related behaviors have been observed as early as toddlerhood for children who later develop ADHD. Children with ADHD have disrupted connectivity in neural circuitry involved in executive control of attention, including the prefrontal cortex (PFC) and dorsal attention network (DAN). It is not known if these alterations in connectivity can be identified before the onset of ADHD. Children (N = 51) 1.5-3 years old were assessed using functional near-infrared spectroscopy while engaging with a book. The relation between mother-reported ADHD-related behaviors and neural connectivity, computed using robust innovation-based correlation, was examined. Task engagement was high across the sample and unrelated to ADHD-related behaviors. Observed attention was associated with greater connectivity between the right lateral PFC and the right temporal parietal junction (TPJ). Children with greater ADHD-related behaviors had greater frontoparietal connectivity, particularly between the PFC bilaterally and the right TPJ. Toddlers at risk for developing ADHD may require increased frontoparietal connectivity to sustain attention. Future work is needed to examine early interventions that enhance developing attention and their effect on neural connectivity between the PFC and attention networks.

Low-intensity transcranial ultrasound stimulation improves memory behavior in an ADHD rat model by modulating cortical functional network connectivity.

Working memory in attention deficit hyperactivity disorder (ADHD) is closely related to cortical functional network connectivity (CFNC), such as abnormal connections between the frontal, temporal, occipital cortices and with other brain regions. Low-intensity transcranial ultrasound stimulation (TUS) has the advantages of non-invasiveness, high spatial resolution, and high penetration depth and can improve ADHD memory behavior. However, how it modulates CFNC in ADHD and the CFNC mechanism that improves working memory behavior in ADHD remain unclear. In this study, we observed working memory impairment in ADHD rats, establishing a corresponding relationship between changes in CFNCs and the behavioral state during the working memory task. Specifically, we noted abnormalities in the information transmission and processing capabilities of CFNC in ADHD rats while performing working memory tasks. These abnormalities manifested in the network integration ability of specific areas, as well as the information flow and functional differentiation of CFNC. Furthermore, our findings indicate that TUS effectively enhances the working memory ability of ADHD rats by modulating information transmission, processing, and integration capabilities, along with adjusting the information flow and functional differentiation of CFNC. Additionally, we explain the CFNC mechanism through which TUS improves working memory in ADHD. In summary, these findings suggest that CFNCs are important in working memory behaviors in ADHD.

Emotional Regulation Problems in Cognitive Disengagement Syndrome (formerly Sluggish Cognitive Tempo), Attention Deficit and Hyperactivity Disorder, Anxiety and Depression.

Parents have reported emotional regulation problems in cognitive disengagement syndrome (CDS) and attention deficit and hyperactivity disorder (ADHD). The first objective of this research was to explore the differences between the parents' ratings on CDS, ADHD, hyperactivity/impulsivity, inattention, anxiety, depression and emotional dysregulation. The second one was to compare the predictive capacity of CDS and ADHD over anxiety, depression and emotional regulation problems. The third one was to analyze the mediation of emotional dysregulation in CDS, ADHD, hyperactivity/impulsivity, inattention, and anxiety and depression. The sampling used was non-probabilistic. The final sample consisted of 1,070 participants (484 fathers and 586 mothers) who completed the Emotion Regulation Checklist (ERC) and the Child and Adolescent Behavior Inventory (CABI). In relation to the first objective, first, mothers reported more emotional regulation problems in children than in fathers. Second, emotional regulation problems were more strongly correlated with hyperactivity/impulsivity. Significant differences were found in all father scores, except for anxiety and the emotional regulation subscale. Regarding mothers, significant differences were only observed in ADHD scores, hyperactivity/impulsivity, and depression. Both parents reported more problems in older children, except for hyperactivity/impulsivity scores and ADHD rated by mothers. According to the second objective, CDS scores were found to significantly predict anxiety and depression scores, but not those of inattention or emotional regulation problems. Finally, in relation to the third objective, emotional regulation problems mediated the relationships between CDS, ADHD, and anxiety and depression. In conclusion, the data support the importance of emotional regulation problems in understanding CDS and its relationship with ADHD, anxiety, and depression.

Compressed cerebro-cerebellar functional gradients in children and adolescents with attention-deficit/hyperactivity disorder.

Both cortical and cerebellar developmental differences have been implicated in attention-deficit/hyperactivity disorder (ADHD). Recently accumulating neuroimaging studies have highlighted hierarchies as a fundamental principle of brain organization, suggesting the importance of assessing hierarchy abnormalities in ADHD. A novel gradient-based resting-state functional connectivity analysis was applied to investigate the cerebro-cerebellar disturbed hierarchy in children and adolescents with ADHD. We found that the interaction of functional gradient between diagnosis and age was concentrated in default mode network (DMN) and visual network (VN). At the same time, we also found that the opposite gradient changes of DMN and VN caused the compression of the cortical main gradient in ADHD patients, implicating the co-occurrence of both low- (visual processing) and high-order (self-related thought) cognitive dysfunction manifesting in abnormal cerebro-cerebellar organizational hierarchy in ADHD. Our study provides a neurobiological framework to better understand the co-occurrence and interaction of both low-level and high-level functional abnormalities in the cortex and cerebellum in ADHD.

Global research progress of electroencephalography applications in attention deficit hyperactivity disorder: Bibliometrics and visualized analysis.

Attention deficit hyperactivity disorder (ADHD) is a profound neurodevelopmental disorder. Currently, the diagnosis of ADHD relies on clinical assessments and lacks objective testing. Research in electroencephalography (EEG) offers new hope for the diagnosis of ADHD, with researchers actively seeking objective EEG biomarkers. This study conducts a bibliometric analysis of the application of EEG in ADHD, aiming to provide a brief overview of the characteristics, main research areas, development paths, and trends in this field. The Web of Science Core Collection was queried on June 10, 2024, to gather relevant scholarly works from the period of 2004 to 2023. Analysis was conducted using CiteSpace, VOSviewer, and Microsoft Excel 2019. In the past 20 years, 1162 documents qualified, with a swift rise in annual publications. The USA, University of London, and Barry RJ led in productivity and impact, while the Clinical Neurophysiology topped in publication volume and citations. High-frequency terms include "ADHD," "EEG," "event-related potentials (ERP)," "children," and "neurofeedback." Clustering key terms such as "cognitive control," "theta waves," "epilepsy," "graph theory," "machine learning," and "neurofeedback" form the cornerstone of the current core research areas. At the same time, a series of emerging research frontiers are gradually emerging, including "theta/beta ratio (TBR)," "P300 wave," "neurofeedback," and "deep learning." Over the past 2 decades, research on the application of EEG in ADHD has been burgeoning, with themes becoming increasingly profound. These insights provide key guidance on current trends, development trajectories, and future challenges in the field.

The Utility of Neuromuscular Assessment to Identify ADHD Among Patients with a Complex Symptom Picture.

OBJECTIVE: Diagnostic assessment of ADHD is challenging due to comorbid psychopathologies and symptoms overlapping with other psychiatric disorders. In this study, we investigate if a distinct pattern of neuromuscular dysregulation previously reported in ADHD, can help identifying ADHD in psychiatric patients with diverse and complex symptoms. METHOD: We explored the impact of neuromuscular dysregulation, as measured by The Motor Function Neurologic Assessment (MFNU), on the likelihood of being diagnosed with ADHD, affective disorder, anxiety disorder, or personality disorder among adults (n = 115) referred to a psychiatric outpatient clinic. RESULTS: Logistic regression revealed that neuromuscular dysregulation was significantly associated with ADHD diagnosis only (OR 1.15, p < .01), and not with affective-, anxiety-, or personality disorders. Sensitivity and specificity for ADHD at different MFNU scores is provided. CONCLUSIONS: A test of neuromuscular dysregulation may promote diagnostic accuracy in differentiating ADHD from other psychiatric disorders in patients with an overlapping symptom picture. This may have important implications for clinical practice. More studies are needed.

ADHD-pain: Characteristics of chronic pain and association with muscular dysregulation in adults with ADHD.

OBJECTIVES: A high incidence of attention-deficit hyperactivity disorder (ADHD) has been reported in chronic pain (ChP) patients. Furthermore, an association between ChP and muscular dysregulation has been reported in adults with ADHD. The present study investigated whether ADHD was more prevalent among psychiatric outpatients with ChP than those without ChP, and if there was an association between ChP, muscular dysregulation and characteristics of pain in patients with ADHD. METHODS: One-hundred and twenty-one individuals remitted to an outpatient psychiatry unit took part in this naturalistic epidemiological cross-sectional study. They were assessed with a pain self-report form (localization, intensity, and onset) and a test of muscle dysregulation (the Motor Function Neurological Assessment). Prevalence of ADHD among patients with ChP, as well as the qualitative characteristics of ChP within the ADHDgroup are reported. Both ChP and pain intensity correlated with muscular dysregulation through Spearman's rho analysis. Additionally, the relationship between various diagnostic categories (ADHD, affective disorders, anxiety, or personality disorders) and incidence of axial pain was evaluated in logistic regression. RESULTS: ADHD was significantly more prevalent in patients with ChP, than in patients without ChP. In the ADHD group, ChP and pain intensity was associated with muscular dysregulation, particularly with high muscle tone. ChP was more axial and widespread, than for the patients without ADHD, and started at an early age. ADHD diagnosis predicted axial pain, whereas affective-, anxiety-, or personality disorders did not. CONCLUSIONS: The study suggests that ChP in ADHD is associated with muscular dysregulation and is qualitatively different from ChP in psychiatric patients without ADHD. These findings may lead to further understanding of potential mechanisms involved in ADHD and ChP, and in turn to new treatment strategies for both disorders.

Sex differences in physiological correlates of affectively driven decision-making behavior in adult ADHD.

BACKGROUND: Sex differences in the symptomatology of adults with attention-deficit/hyperactivity disorder (ADHD) have often been overlooked when studying behavioral abnormalities. However, it is known that women exhibit considerably more stronger symptoms related to emotional competence than men. Since affective functions significantly influence the processing of risky decision-making and risk-engagement, we assume that risky behavior in ADHD is affected by sex differences. Therefore, we specifically investigated sex-specific effects on the interaction between emotionally induced changes in physiology and behavioral performance on a decision-making task. METHODS: Skin conductance responses of twenty-nine adults with ADHD (n = 16 male; n = 13 female) and thirty-three adults in the control group (n = 14 male; n = 19 female) were recorded during the performance in a modified version of the Balloon Analogue Risk Task (BART). Additional questionnaires were used to reveal insights in the self-assessment of emotional competence, risk perception, and feedback sensitivity. Emotional arousal and decision-making behavior were analyzed using linear mixed-effects models. RESULTS: Results showed different effects of sex on risk behaviors in controls and ADHD. In contrast to healthy controls, female adults with ADHD showed a significantly greater risk engagement in the BART compared to males with ADHD. This contrary sex relation was not observed in skin conductance responses and revealed a significantly different sex-dependent correlation of body response and behavioral task performance in ADHD. Comparisons with results from self-assessments furthermore indicate a reduced behavioral self-perception in women with ADHD, but not in men. CONCLUSION: In summary, we found an altered interaction between physiological activity and risky behavior in women with ADHD. Thus, the present study indicates a reduced sensitivity towards the own bodily responses in women with ADHD, which could consequently cause increased risky DM behavior in daily life. The current results suggest that more consideration needs to be given to sex-specific effects on physiological processes and behavior in adults with ADHD.

Dynamics of spontaneous thoughts: Exploration, attentional profile and the segmentation of the stream of thoughts.

For a long time, clinical knowledge and first-person reports have pointed to individual differences in the dynamics of spontaneous thoughts, in particular in the extreme case of psychiatric conditions (e.g. racing thoughts in Attention Deficit / Hyperactivity Disorder, ADHD; rumination in depression). We used a novel procedure to investigate this individual variability by combining verbal fluency tasks and introspective reports of thought content. Our goal was twofold. First, we tested the hypothesis that a greater segmentation of the stream of thoughts would be associated with trait inattention, in line with subjective reports of ADHD patients. Second, we tested whether the segmentation of the stream of thoughts increased with an increased tendency for exploratory behavior, following recent theoretical claims on the mechanisms underpinning the generation of spontaneous thoughts. Our results support both hypotheses, shedding light on the factors contributing to the individual variability in the dynamics of the stream of thought.

Maternal psychopathology is differentially associated with adolescent offspring neural response to reward given offspring ADHD risk.

Reinforcement sensitivity is a hypothesized attention-deficit/hyperactivity disorder (ADHD) intermediate phenotype but its role in transgenerational transmission of ADHD-linked psychopathology risk is largely unknown. We examined, in a carefully phenotyped, N = 123 sample of adolescents (Mage = 15.27 years, SD = 0.984; 61.78% boys), whether (1) parental psychopathology is differentially associated with fMRI-indexed neural response to reward receipt and (2) both maternal and paternal psychopathology are associated with neural response to reward; across adolescents at-risk for and not at-risk for ADHD. Indices of parental psychopathology were differentially associated with adolescent offspring neural response to reward such that across measures, parental psychopathology was negatively or not associated with offspring superior frontal gyrus (SFG) response to reward receipt in adolescents at-risk for ADHD, but parental psychopathology was positively associated with offspring SFG response in adolescents not at-risk. Further, across measures, greater maternal psychopathology was associated with blunted adolescent SFG response to reward in adolescents at-risk for ADHD whereas greater maternal externalizing problems were linked to enhanced adolescent SFG response in adolescents not at-risk. Across measures, paternal psychopathology was not associated with adolescent response to reward, in either group. ADHD risk confers differential reward-related susceptibility to the effects of parental psychopathology. Results also show this association is nonspecific in terms of parental psychopathology type but is specific to maternal psychopathology.

Distinct structural brain network properties in children with familial versus non-familial attention-deficit/hyperactivity disorder (ADHD).

Attention-deficit/hyperactivity disorder (ADHD) is among the most prevalent, inheritable, and heterogeneous childhood-onset neurodevelopmental disorders. Children with a hereditary background of ADHD have heightened risk of having ADHD and persistent impairment symptoms into adulthood. These facts suggest distinct familial-specific neuropathological substrates in ADHD that may exist in anatomical components subserving attention and cognitive control processing pathways during development. The objective of this study is to investigate the topological properties of the gray matter (GM) structural brain networks in children with familial ADHD (ADHD-F), non-familial ADHD (ADHD-NF), as well as matched controls. A total of 452 participants were involved, including 132, 165 and 155 in groups of ADHD-F, ADHD-NF and typically developed children, respectively. The GM structural brain network was constructed for each group using graph theoretical techniques with cortical and subcortical structures as nodes and correlations between volume of each pair of the nodes within each group as edges, while controlled for confounding factors using regression analysis. Relative to controls, children in both ADHD-F and ADHD-NF groups showed significantly higher nodal global and nodal local efficiencies in the left caudal middle frontal gyrus. Compared to controls and ADHD-NF, children with ADHD-F showed distinct structural network topological patterns associated with right precuneus (significantly higher nodal global efficiency and significantly higher nodal strength), left paracentral gyrus (significantly higher nodal strength and trend toward significantly higher nodal local efficiency) and left putamen (significantly higher nodal global efficiency and trend toward significantly higher nodal local efficiency). Our results for the first time in the field provide evidence of familial-specific structural brain network alterations in ADHD, that may contribute to distinct clinical/behavioral symptomology and developmental trajectories in children with ADHD-F.

Effects of Auditory and Visual White Noise on Oculomotor Inhibition in Children With Attention-Deficit/Hyperactivity Disorder: Protocol for a Crossover Study.

BACKGROUND: In attention-deficit/hyperactivity disorder (ADHD), poor inhibitory control is one of the main characteristics, with oculomotor inhibition impairments being considered a potential biomarker of the disorder. While auditory white noise has demonstrated the ability to enhance working memory in this group, visual white noise is still unexplored and so are the effects of both types of white noise stimulation on oculomotor inhibition. OBJECTIVE: This crossover study aims to explore the impact of auditory and visual white noise on oculomotor inhibition in children with ADHD and typically developing (TD) children. The study will investigate the impact of different noise levels (25% and 50% visual, 78 dB auditory), and performance will be evaluated both with and without noise stimulation. We hypothesize that exposure to white noise will improve performance in children with ADHD and impair the performance for TD children. METHODS: Memory-guided saccades and prolonged fixations, known for their sensitivity in detecting oculomotor disinhibition in ADHD, will be used to assess performance. Children diagnosed with ADHD, withdrawing from medication for 24 hours, and TD children without psychiatric disorders were recruited for the study. RESULTS: Data collection was initiated in October 2023 and ended in February 2024. A total of 97 participants were enrolled, and the first results are expected between September and November 2024. CONCLUSIONS: This study will examine whether cross-modal sensory stimulation can enhance executive function, specifically eye movement control, in children with ADHD. In addition, the study will explore potential differences between auditory and visual noise effects in both groups. Our goal is to identify implications for understanding how noise can be used to improve cognitive performance. TRIAL REGISTRATION: ClinicalTrials.gov NCT06057441; https://clinicaltrials.gov/study/NCT06057441. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/56388.

Altered somatosensory processing in adult attention deficit hyperactivity disorder.

BACKGROUND: Tactile sensitivity and sensory overload in ADHD are well-documented in clinical-, self-, and parent- reports, but empirical evidence is scarce and ambiguous and focuses primarily on children. Here, we compare both empirical and self-report tactile sensitivity and ADHD symptomatology in adults with ADHD and neurotypical controls. We evaluate whether tactile sensitivity and integration is more prevalent in ADHD and whether it is related to ADHD symptom severity. METHODS: Somatosensory evoked potential (SEP) amplitudes were measured in 27 adults with ADHD and 24 controls during four conditions (rest, stroking of the own arm, stroking of the arm by a researcher, and stroking of an object). Participants also filled out questionnaires on tactile sensitivity and ADHD symptoms and performed a Qb-test as an objective measure of ADHD symptom severity. RESULTS: Participants with ADHD self-reported greater tactile sensitivity and ADHD symptom severity than controls and received higher scores on the Qb-test. These values correlated with one another. ADHD participants showed lower tolerable threshold for electrical radial nerve stimulus, and greater reduction in cortical SEP amplitudes during additional tactile stimuli which was correlated with ADHD symptoms. CONCLUSIONS: We find that ADHD symptomatology and touch sensitivity are directly linked, using both self-reports and experimental measures. We also find evidence of tactile sensory overload in ADHD, and an indication that this is linked to inattention specifically. Tactile sensitivity and sensory overload impact the functioning and life quality of many people with ADHD, and clinicians should consider this when treating their patients.

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.

Altered brain functional connectivity in patients with resistance to thyroid hormone ß.

To investigate changes in brain network organization and possible neurobehavioral similarities to attention-deficit hyperactivity disorder (ADHD), we measured changes in brain resting-state functional connectivity (rs-fMRI) and cognitive domains in patients with resistance to thyroid hormone ß (RTHß) and compared them with those in healthy control subjects. In this prospective case-control study, twenty-one participants with genetically confirmed RTHß were matched with 21 healthy controls. The Adult ADHD Self-Report Scale (ASRS-v1.1) and ADHD Rating Scale-IV were used to assess self-reported symptoms of ADHD. A voxel-wise and atlas-based approach was used to identify changes in the brain networks. The RTHß group reported behavioral symptoms similar to those of ADHD. We found evidence of weaker network integration of the lingual and fusiform gyri in the RTHß group, which was mainly driven by weaker connectivity to the bilateral insula and supplementary motor cortex. Functional connectivity between regions of the default mode network (angular gyrus/middle temporal gyrus) and regions of the cognitive control network (bilateral middle frontal gyrus) was increased in RTHß patients compared to healthy controls. Increased connectivity between regions of the default mode network and the dorsolateral prefrontal cortex is frequently reported in ADHD and is interpreted to be associated with deficits in attention. Our finding of weaker connectivity of the lingual gyrus to the bilateral insula (salience network) in RTHß patients has also been reported previously in ADHD and may reflect decreased habituation to visual stimuli and increased distractibility. Overall, our observations support the notion of neuropsychological similarities between RTHß and ADHD.

Transcranial direct current stimulation enhances effort maintenance in ADHD.

BACKGROUND: Youth with attention-deficit/hyperactivity disorder (ADHD) exhibit increased effort aversion, likely due to deficits in anticipatory dopamine firing. Previous research has shown that transcranial direct current stimulation (tDCS) targeting the right prefrontal cortex can enhance activity in dopaminergic meso-striatal regions. However, the extent to which this specific tDCS configuration effectively modulates effort behavior in anticipation of rewards in ADHD remains uncertain. HYPOTHESIS: We expected an increase of effort maintenance and invigoration during and following our tDCS set-up compared to sham in subjects with ADHD. METHODS: Twenty-four children and adolescents with ADHD (mean age: 11.6 years; 95 % CI [10.7, 12.4]) received 2 mA and sham tDCS for 20 min each. The anode was positioned over the ventromedial prefrontal cortex (PFC), while the cathode was placed over the right dorsolateral PFC, generating an electrical field with maximal strength in the right PFC. During and after the tDCS sessions, participants performed a button-pressing task aimed at earning delayed monetary rewards. Primary outcomes were effort maintenance (frequency of button presses) and invigoration (slopes of button presses), measuring motor task performance. RESULTS: We observed a significant increase in effort maintenance both during (b = 2.66; p < 0.001) and after tDCS (b = 2.04; p= .007) compared to sham. No significant difference was found for invigoration during stimulation, while after bonferroni correction (p = 0.025) a non-significant decrease was found after tDCS compared to sham (b = -5.18; p = 0.041). CONCLUSION: tDCS targeting the ventromedial PFC (anodal) and right dorsolateral PFC (cathodal) increases effort maintenance in children and adolescents with ADHD.

From neurons to brain networks, pharmacodynamics of stimulant medication for ADHD.

Stimulants represent the first line pharmacological treatment for attention-deficit/hyperactivity disorder (ADHD) and are among the most prescribed psychopharmacological treatments. Their mechanism of action at synaptic level has been extensively studied. However, it is less clear how their mechanism of action determines clinically observed benefits. To help bridge this gap, we provide a comprehensive review of stimulant effects, with an emphasis on nuclear medicine and magnetic resonance imaging (MRI) findings. There is evidence that stimulant-induced modulation of dopamine and norepinephrine neurotransmission optimizes engagement of task-related brain networks, increases perceived saliency, and reduces interference from the default mode network. An acute administration of stimulants may reduce brain alterations observed in untreated individuals in fronto-striato-parieto-cerebellar networks during tasks or at rest. Potential effects of prolonged treatment remain controversial. Overall, neuroimaging has fostered understanding on stimulant mechanism of action. However, studies are often limited by small samples, short or no follow-up, and methodological heterogeneity. Future studies should address age-related and longer-term effects, potential differences among stimulants, and predictors of treatment response.

The impact of paediatric epilepsy and co-occurring neurodevelopmental disorders on functional brain networks in wake and sleep.

Epilepsy is one of the most common neurological disorders in children. Diagnosing epilepsy in children can be very challenging, especially as it often coexists with neurodevelopmental conditions like autism and ADHD. Functional brain networks obtained from neuroimaging and electrophysiological data in wakefulness and sleep have been shown to contain signatures of neurological disorders, and can potentially support the diagnosis and management of co-occurring neurodevelopmental conditions. In this work, we use electroencephalography (EEG) recordings from children, in restful wakefulness and sleep, to extract functional connectivity networks in different frequency bands. We explore the relationship of these networks with epilepsy diagnosis and with measures of neurodevelopmental traits, obtained from questionnaires used as screening tools for autism and ADHD. We explore differences in network markers between children with and without epilepsy in wake and sleep, and quantify the correlation between such markers and measures of neurodevelopmental traits. Our findings highlight the importance of considering the interplay between epilepsy and neurodevelopmental traits when exploring network markers of epilepsy.

Electrophysiological functional connectivity and complexity reflecting cognitive processing speed heterogeneity in young children with ADHD.

Early intervention is imperative for young children with attention-deficit/hyperactivity disorder (ADHD) who manifest heterogeneous neurocognitive deficits. The study investigated the functional connectivity and complexity of brain activity among young children with ADHD exhibiting a fast cognitive processing speed (ADHD-F, n = 26), with ADHD exhibiting a slow cognitive processing speed (ADHD-S, n = 17), and typically developing children (n = 35) using wireless electroencephalography (EEG) during rest and task conditions. During rest, compared with the typically developing group, the ADHD-F group displayed lower long-range intra-hemispheric connectivity, while the ADHD-S group had lower frontal beta inter-hemispheric connectivity. During task performance, the ADHD-S group displayed lower frontal beta inter-hemispheric connectivity than the typically developing group. The ADHD-S group had lower frontal inter-hemispheric connectivity in broader frequency bands than the ADHD-F group, indicating ADHD heterogeneity in mental processing speed. Regarding complexity, the ADHD-S group tended to show lower frontal entropy estimators than the typically developing group during the task condition. These findings suggest that the EEG profile of brain connectivity and complexity can aid the early clinical diagnosis of ADHD, support subgrouping young children with ADHD based on cognitive processing speed heterogeneity, and may contain specific novel neural biomarkers for early intervention planning.