Electrophysiological indices of error monitoring in juvenile and adult attention deficit hyperactivity disorder (ADHD)--a meta-analytic appraisal

Genetic Overlap Between Midfrontal Theta Signals and Attention-Deficit/Hyperactivity Disorder and Autism Spectrum Disorder in a Longitudinal Twin Cohort

BACKGROUND

Cognitive control has been strongly linked to midfrontal theta (4-8 Hz) brain activity. Such control processes are known to be impaired in individuals with psychiatric conditions and neurodevelopmental diagnoses, including attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). Temporal variability in theta, in particular, has been associated with ADHD, with shared genetic variance underlying the relationship. Here, we investigated the phenotypic and genetic relationships between theta phase variability, theta-related signals (the N2, error-related negativity, and error positivity), reaction time, and ADHD and ASD longitudinally in a large twin study of young adults to investigate the stability of the genetic relationships between these measures over time.

METHODS

Genetic multivariate liability threshold models were run on a longitudinal sample of 566 participants (283 twin pairs). Characteristics of ADHD and ASD were measured in childhood and young adulthood, while an electroencephalogram was recorded in young adulthood during an arrow flanker task.

RESULTS

Cross-trial theta phase variability in adulthood showed large positive phenotypic and genetic relationships with reaction time variability and both childhood and adult ADHD characteristics. Error positivity amplitude was negatively related phenotypically and genetically to ADHD and ASD at both time points.

CONCLUSIONS

We showed significant genetic associations between variability in theta signaling and ADHD. A novel finding from the current study is that these relationships were stable across time, indicating a core dysregulation of the temporal coordination of control processes in ADHD that persists in individuals with childhood symptoms. Error processing, indexed by the error positivity, was altered in both ADHD and ASD, with a strong genetic contribution.

The relation between executive functions, error-related brain activity, and ADHD symptoms in clinically evaluated school-aged children

Two event-related potentials (ERPs) elicited following errors, the error-related negativity (ERN) and error positivity (Pe), have been proposed to reflect cognitive control, though the specific processes remain debated. Few studies have examined the ERN and Pe's relations with individual differences in cognitive control/executive functioning using well-validated tests administered separately from the inhibition tasks used to elicit the ERN/Pe. Additionally, neurocognitive tests of executive functions tend to strongly predict ADHD symptoms, but the extent to which task-based and EEG-based estimates of executive functioning/cognitive control account for the same variance in ADHD symptoms remains unclear. The current study addressed these limitations by examining relations between the ERN/Pe and three core executive functions (working memory, inhibitory control, set shifting) in a clinically-evaluated sample of 53 children ages 8-12 (Mage = 10.36, SD = 1.42; 77.4% White/Non-Hispanic; 16 girls) with and without ADHD. Results demonstrated that neither the ERN nor Pe were related to overall cognitive control/executive functioning, or to working memory or set shifting specifically (all 95%CIs include 0.0). In contrast, a larger Pe was associated with better-developed inhibitory control (β=-.35, 95%CI excludes 0.0), but did not capture aspects of inhibitory control that are important for predicting ADHD symptoms. Neither the ERN nor Pe predicted ADHD symptoms (95%CIs include 0.0). Results were generally robust to control for age, sex, SES, ADHD symptom cluster, and anxiety, and emphasize the need for caution when interpreting the ERN/Pe as indices of broad-based cognitive control/executive functioning, as well as using the ERN/Pe to examine cognitive processes contributing to ADHD symptomatology.

Reduced Error Recognition Explains Post-Error Slowing Differences among Children with Attention Deficit Hyperactivity Disorder

OBJECTIVE

Youth with attention deficit hyperactivity disorder (ADHD) often show reduced post-error slowing (PES) compared to typically developing controls. This finding has been interpreted as evidence that children with ADHD have error recognition and adaptive control impairments. However, several studies report mixed results regarding PES differences in ADHD, and among healthy controls, there is considerable debate about the cognitive-behavioral origin of PES.

METHODS

We tested competing hypotheses aimed at clarifying whether reduced PES in children with ADHD is due to impaired error detection, deficits in adaptive control, and/or attention orienting to novelty. Children aged 7-11 years with a diagnosis of ADHD (n = 74) and controls (n = 30) completed four laboratory-based computer tasks with variable cognitive loads and error types.

RESULTS

ADHD diagnosis was associated with shorter PES only on a task with high cognitive load and low error-cuing, consistent with impaired error recognition. In contrast, there was no evidence of impaired adaptive control or heightened novelty orienting among children with ADHD.

CONCLUSIONS

The cognitive-behavioral origin of PES is multifactorial, but reduced PES among children with an ADHD diagnosis is due to impaired error recognition during cognitively demanding tasks. Behavioral interventions that scaffold error recognition may facilitate improved performance among children with ADHD.

Multimodal Virtual Reality-Based Assessment of Adult ADHD: A Feasibility Study in Healthy Subjects

Neuropsychological assessments are often surprisingly inaccurate in mapping clinically-reported attention-deficit hyperactivity disorder (ADHD) symptoms, presumably due to their low ecological validity. Virtual reality (VR) might offer a potential solution for this problem, given its capability to generate standardized and yet highly realistic virtual environments. As the first adaptation of existing virtual classroom scenarios to an adult population, we developed a Virtual Seminar Room (VSR) for multimodal characterization of ADHD symptoms. To test its feasibility, N = 35 healthy participants were immersed into the VSR via a head-mounted display and carried out a VR-embedded continuous performance task (CPT) under varying levels of distractions in two experimental blocks (24 min each). CPT performance, electroencephalography (EEG) measures, and head movements (actigraphy) were simultaneously recorded and analyzed offline. Although CPT performance remained constant throughout the task, head movements increased significantly from Block 1 to Block 2. In addition, EEG theta (4-7 Hz) and beta (13-30 Hz) power was higher during Block 1 than Block 2, and during distractor-present than distractor-absent phases. Moreover, P300 amplitudes were higher during Block 1 than Block 2, and P300 latencies were prolonged in distractor-absent compared with distractor-present phases. Although the paradigm awaits further improvements, this study confirms the general feasibility of the VSR and provides a first step toward a multimodal, ecologically valid, and reliable VR-based adult ADHD assessment.

Midfrontal Theta Activity in Psychiatric Illness: An Index of Cognitive Vulnerabilities Across Disorders

There is an urgent need to identify the mechanisms that contribute to atypical thinking and behavior associated with psychiatric illness. Behavioral and brain measures of cognitive control are associated with a variety of psychiatric disorders and conditions as well as daily life functioning. Recognition of the importance of cognitive control in human behavior has led to intensive research into behavioral and neurobiological correlates. Oscillations in the theta band (4-8 Hz) over medial frontal recording sites are becoming increasingly established as a direct neural index of certain aspects of cognitive control. In this review, we point toward evidence that theta acts to coordinate multiple neural processes in disparate brain regions during task processing to optimize behavior. Theta-related signals in human electroencephalography include the N2, the error-related negativity, and measures of theta power in the (time-)frequency domain. We investigate how these theta signals are affected in a wide range of psychiatric conditions with known deficiencies in cognitive control: anxiety, obsessive-compulsive disorder, attention-deficit/hyperactivity disorder, and substance abuse. Theta-related control signals and their temporal consistency were found to differ in most patient groups compared with healthy control subjects, suggesting fundamental deficits in reactive and proactive control. Notably, however, clinical studies directly investigating the role of theta in the coordination of goal-directed processes across different brain regions are uncommon and are encouraged in future research. A finer-grained analysis of flexible, subsecond-scale functional networks in psychiatric disorders could contribute to a dimensional understanding of psychopathology.

What Has Been Learned from Using EEG Methods in Research of ADHD?

Electrophysiological recording methods, including electroencephalography (EEG) and magnetoencephalography (MEG), have an unparalleled capacity to provide insights into the timing and frequency (spectral) composition of rapidly changing neural activity associated with various cognitive processes. The current chapter provides an overview of EEG studies examining alterations in brain activity in ADHD, measured both at rest and during cognitive tasks. While EEG resting state studies of ADHD indicate no universal alterations in the disorder, event-related studies reveal consistent deficits in attentional and inhibitory control and consequently inform the proposed cognitive models of ADHD. Similar to other neuroimaging measures, EEG research indicates alterations in multiple neural circuits and cognitive functions. EEG methods - supported by the constant refinement of analytic strategies - have the potential to contribute to improved diagnostics and interventions for ADHD, underlining their clinical utility.

A systematic review and meta-analysis of altered electrophysiological markers of performance monitoring in Obsessive-Compulsive Disorder (OCD), Gilles de la Tourette Syndrome (GTS), Attention-Deficit/Hyperactivity disorder (ADHD) and Autism

Altered performance monitoring is implicated in obsessive-compulsive disorder (OCD), Gilles de la Tourette syndrome (GTS), attention-deficit/hyperactivity disorder (ADHD) and autism. We conducted a systematic review and meta-analysis of electrophysiological correlates of performance monitoring (error-related negativity, ERN; error positivity, Pe; feedback-related negativity, FRN; feedback-P3) in individuals with OCD, GTS, ADHD or autism compared to control participants, or associations between correlates and symptoms/traits of these conditions. Meta-analyses on 97 studies (5890 participants) showed increased ERN in OCD (Hedge's g = 0.54[CIs:0.44,0.65]) and GTS (g = 0.99[CIs:0.05,1.93]). OCD also showed increased Pe (g = 0.51[CIs:0.21,0.81]) and FRN (g = 0.50[CIs:0.26,0.73]). ADHD and autism showed reduced ERN (ADHD: g=-0.47[CIs:-0.67,-0.26]; autism: g=-0.61[CIs:-1.10,-0.13]). ADHD also showed reduced Pe (g=-0.50[CIs:-0.69,-0.32]). These findings suggest overlap in electrophysiological markers of performance monitoring alterations in four common neurodevelopmental conditions, with increased amplitudes of the markers in OCD and GTS and decreased amplitudes in ADHD and autism. Implications of these findings in terms of shared and distinct performance monitoring alterations across these neurodevelopmental conditions are discussed. PROSPERO pre-registration code: CRD42019134612.

Early neurophysiological stimulus processing during a performance-monitoring task differentiates women with bipolar disorder from women with ADHD

Adults with attention-deficit/hyperactivity disorder (ADHD) or bipolar disorder (BD) may display similar cognitive impairments and clinical symptoms, which might reflect shared mechanisms. Initial evidence indicates disorder-specific and overlapping neurophysiological alterations using event-related potentials (ERPs) in individuals with BD or ADHD during attentional tasks, but it is unknown whether impairments generalize across other processes and tasks. We conduct the first comparison between women with ADHD (n = 20), women with BD (n = 20) and control women (n = 20) on ERPs from a performance-monitoring flanker task. The BD group showed a significantly attenuated frontal ERP of conflict monitoring (N2) compared to the ADHD group across both low-conflict (congruent) and high-conflict (incongruent) task conditions, and compared to controls in the high-conflict condition. However, when controlling for an earlier attentional ERP (frontal N1), which was significantly reduced in participants with BD compared to participants with ADHD and controls, N2 group differences were no longer significant. These results indicate that ERP differences in conflict monitoring may be attributable to differences in earlier attentional processes. These findings identify neural differences in early attention between BD and ADHD which precede conflict monitoring processes, potentially pointing to distinct neural mechanisms implicated in the two disorders.

What Event-Related Potential Tells Us about Brain Function: Child-Adolescent Psychiatric Perspectives

Electroencephalography (EEG) measures neural activation due to various cognitive processes. EEG and event-related potentials (ERPs) are widely used in studies investigating psychopathology and neural substrates of psychiatric diseases in children and adolescents. The present study aimed to review recent ERP studies in child and adolescent psychiatry. ERPs are non-invasive methods for studying synaptic functions in the brain. ERP might be a candidate biomarker in child-adolescent psychiatry, considering its ability to reflect cognitive and behavioral functions in humans. For the EEG study of psychiatric diseases in children and adolescents, several ERP components have been used, such as mismatch negativity, P300, error-related negativity (ERN), and reward positivity (RewP). Regarding executive functions and inhibition in patients with attention-deficit/hyperactivity disorder (ADHD), P300 latency, and ERN were significantly different in patients with ADHD compared to those in the healthy population. ERN showed meaningful changes in patients with anxiety disorders, such as generalized anxiety disorder, separation anxiety disorder, and obsessive-compulsive disorder. Patients with depression showed significantly attenuated RewP compared to the healthy population, which was related to the symptoms of anhedonia.

Event-related potential (ERP) measures of error processing as biomarkers of externalizing disorders: A narrative review

Previous studies have shown that electrophysiological measures of error processing are affected in patients at risk or diagnosed with internalizing disorders, hence, suggesting that error processing could be a suitable biomarker for internalizing disorders. In this narrative review, we will evaluate studies that address the role of event-related potential (ERP) measures of error-processing in externalizing disorders and discuss to what extend these can be considered a biomarker for externalizing disorders. Currently, there is evidence for the notion that electrophysiological indices of error processing such as the error-related negativity (ERN) and error positivity (Pe) are reduced in individuals with substance use disorders, attention-deficit/hyperactivity disorder, and in forensic populations. However, it remains unclear whether this is also the case for other understudied disorders such as behavioral addiction. Furthermore, to fully understand how these deficits affect day to day behavior, we encourage research to focus on testing current theories and hypotheses of ERN and Pe. In addition, we argue that within an externalizing disorder, individual differences in error processing deficits may be related to prognosis and gender of the patient, methodological issues and presence of comorbidity. Next, we review studies that have related treatment trajectories with ERP measures of error processing, and we discuss the prospect of improving error processing as a treatment option. We conclude that ERP measures of error processing are candidate biomarkers for externalizing disorders, albeit we strongly urge researchers to continue looking into the predictive value of these measures in the etiology and treatment outcome through multi-method and longitudinal designs.

Emotion Regulation and Children With Attention-Deficit/Hyperactivity Disorder: The Effect of Varying Phonological Working Memory Demands

Objective: Findings from extant studies of the relationship between ADHD-related emotion regulation and working memory deficits have been equivocal, and their correlational designs preclude inferences about the functional relationship between working memory demands and emotion regulation. This study aimed to experimentally examine the functional relationship between varying working memory demands and ADHD-related emotion regulation deficits. Method: Overt emotion regulation behaviors were coded while children with and without ADHD completed experimental tasks that manipulated low and high working memory demands. Results: Compared with typically developing children, children with ADHD exhibited large-magnitude overall emotion expression deficits, disproportionately greater self-criticism during high working memory conditions, and disproportionately greater positive emotion expression during low working memory demand conditions. Conclusion: These findings suggest that working memory demands are functionally related to emotion regulation deficits exhibited by children with ADHD and may explicate variability of emotion regulation difficulties related to environmental demands.

The moderating role of externalizing problems on the association between anxiety and the error-related negativity in youth

The error-related negativity (ERN) is an event-related potential that reflects error monitoring. Enhanced ERN indicates sensitivity to performance errors and is a correlate of anxiety disorders. In contrast, youth with externalizing problems exhibit a reduced ERN, suggesting decreased error monitoring. Anxiety and externalizing problems commonly co-occur in youth, but no studies have tested how comorbidity might modulate the ERN. In a sample of youth (N = 46, ages 7-19) with and without anxiety disorders, this preliminary study examined the interactive effect of anxiety and externalizing problems on ERN. Results suggest that externalizing problems moderate the relation between anxiety symptoms and ERN in youth. Anxious youth with less externalizing problems exhibited enhanced ERN response to errors. Conversely, anxious youth with greater externalizing problems demonstrated diminished ERN in response to errors. The regions of significance and proportion affected tests indicated that the moderating the effect of externalizing problems was only significant for youth with anxiety disorders. Findings suggest that enhanced neural error sensitivity could be a specific neurophysiological marker for anxiety disorders, whereas anxious individuals with comorbid externalizing problems demonstrate reduced error monitoring, similar to those with primary externalizing pathology. Results underscore the utility of examining neural correlates of pediatric anxiety comorbidity subtypes.

Error and post-error processing in children with attention-deficit/hyperactivity disorder: An electrical neuroimaging study

OBJECTIVE

Inaccurate and inconsistent response styles in attention-deficit/hyperactivity disorder (ADHD) have been observed in a wide variety of cognitive tasks, in line with regulatory deficit models of ADHD. Event-related potential (ERP) studies of error processing have provided evidence for these models, but are limited in specificity. We aimed to improve the isolation, localization and identification of error (self-monitoring and adaptive control) and post-error (implementation of cognitive control) processing in ADHD.

METHODS

ERPs were obtained for 46 ADHD and 51 typically developing (TD) children using the stop-signal task. Response-locked error (Ne and Pe) and stimulus-locked post-error (N2) components were compared between groups. Ne/Pe were corrected for preceding stimulus overlap and group differences were localized.

RESULTS

Ne was intact, while Pe amplitude was markedly reduced in children with ADHD (ηp² = 0.14). Pe differences were localized in the dorsal posterior/midcingulate (BA31/24) cortex. While the TD group showed increased N2 amplitude in post-error trials (ηp² = 0.24), localized in the left ventrolateral prefrontal cortex (VLPFC) and angular gyrus, the ADHD group did not.

CONCLUSIONS

Self-regulation deficits in ADHD are associated with later stages of error processing and subsequent implementation of cognitive control.

SIGNIFICANCE

We contribute to the literature by further specifying error processing deficits in ADHD.

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.

In Quest of Pathognomonic/Endophenotypic Markers of Attention Deficit Hyperactivity Disorder (ADHD): Potential of EEG-Based Frequency Analysis and ERPs to Better Detect, Prevent and Manage ADHD

Attention deficit hyperactivity disorder (ADHD) is a chronic heritable developmental delay psychiatric disorder requiring chronic management, characterized by inattention, hyperactivity, hyperkinectivity and impulsivity. Subjective clinical evaluation still remains crucial in its diagnosis. Discussed are two key aspects in the “characterizing ADHD” and on the quest for objective “pathognomonic/endophenotypic diagnostic markers of ADHD”. The first aspect briefly revolves around issues related to identification of pathognomonic/endophenotypic diagnostic markers in ADHD. Issues discussed include changes in ADHD definition, remission/persistence and overlapping-symptoms cum shared-heritability with its co-morbid cross-border mental disorders. The second aspect discussed is neurobiological and EEG-based studies on ADHD. Given the neurobiological and temporal aspects of ADHD symptoms the electroencephalograph (EEG) like NeuralScan by Medeia appears as an appropriate tool. The EEGs appropriateness is further enhanced when coupled with suitable behavior/cognitive/motor/psychological tasks/paradigms yielding EEG-based markers like event-related-potential (ERPs like P3 amplitudes and latency), reaction time variability (RTV), Theta:Beta ratio (TBR) and sensorimotor rhythm (SMR). At present, these markers could potentially help in the neurobiological characterization of ADHD and either help in identifying or lay the groundwork for identifying pathognomonic and/or endophenotypic EEG-based markers enabling its diagnosis, treatment and management.

Infant behavioral inhibition predicts personality and social outcomes three decades later

Does infant temperament predict adult personality and life-course patterns? To date, there is scant evidence examining relations between child temperament and adult outcomes, and extant research has relied on limited methods for measuring temperament such as maternal report. This prospective longitudinal study followed a cohort of infants (n = 165) for three decades to examine whether infant behavioral inhibition, a temperament characterized by cautious and fearful behaviors to unfamiliar situations, shapes long-term personality, social relationships, vocational/education, and mental health outcomes in adulthood. At age 14 mo, behavioral inhibition was assessed using an observation paradigm. In adolescence (15 y; n = 115), error monitoring event-related potentials were measured in a flanker task. In adulthood (26 y; n = 109), personality, psychopathology, and sociodemographics were self-reported using questionnaires. We found that infants with higher levels of behavioral inhibition at 14 mo grew up to become more reserved and introverted adults (β = 0.34) with lower social functioning with friends and family (β = -0.23) at age 26. Infant behavioral inhibition was also a specific risk factor for adult internalizing (i.e., anxiety and depression, β = 0.20) psychopathology, rather than a transdiagnostic risk for general and externalizing psychopathology. We identified a neurophysiologic mechanism underlying risk and resilience for later psychopathology. Heightened error monitoring in adolescence moderated higher levels of adult internalizing psychopathology among behaviorally inhibited individuals. These findings suggest meaningful continuity between infant temperament and the development of adult personality. They provide the earliest evidence suggesting that the foundation of long-term well-being is rooted in individual differences in temperament observed in infancy.

Patients with mutations of the Thyroid hormone beta-receptor show an ADHD-like phenotype for performance monitoring: an electrophysiological study

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Mutations in the thyroid hormone receptor beta (THRB) lead to relative hyperthyroidism in the brain.

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Electrophysiological biomarkers of performance monitoring (ERN and Pe components) show a pattern similar to ADHD in carriers of THRB mutations.

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The phenotype of THRB mutation carriers is indistinguishable from ADHD with regard to performance monitoring.

Resistance to thyroid hormone beta (RTHβ) is a syndrome of reduced responsiveness of peripheral tissue to thyroid hormone, caused by mutations in the thyroid hormone receptor beta (THRB). Its cognitive phenotype has been reported to be similar to attention deficit hyperactivity disorder (ADHD). This study used electrophysiological biomarkers of performance monitoring in RTHβ to contribute further evidence on its phenotypical similarity to ADHD. Twenty-one participants with RTHβ aged 18–67 years and 21 matched healthy controls performed a modified flanker task during EEG recording. The RTHβ and control groups were compared on behavioural measures and components of event related potentials (ERPs), i.e. the error related negativity (ERN), the error positivity (Pe) and P3 component. There were no significant group differences with regard to behaviour. RTHβ subjects displayed significantly reduced ERN and Pe amplitudes compared to the controls in the response-locked ERPs. In addition, we observed reduced P3 amplitudes in both congruent and incongruent trials, as well as prolonged P3 latencies in RTHβ subjects in the stimulus-locked ERPs. Our findings reveal alterations in error detection and performance monitoring of RTHβ patients, likely indicating reduced error awareness. The electrophysiological phenotype of RTHß subjects with regard to action monitoring is indistinguishable from ADHD.

Behavioral and Electrophysiological Correlates of Performance Monitoring and Development in Children and Adolescents with Attention-Deficit/Hyperactivity Disorder

The pathophysiology of attention-deficit/hyperactivity disorder (ADHD) involves deficits in performance monitoring and adaptive adjustments. Yet, the developmental trajectory and underlying neural correlates of performance monitoring deficits in youth with ADHD remain poorly understood. To address the gap, this study recruited 77 children and adolescents with ADHD and 77 age- and gender-matched healthy controls (HC), ages 8–18 years, who performed an arrow flanker task during electroencephalogram recording. Compared to HC, participants with ADHD responded more slowly and showed larger reaction time variability (RTV) and reduced post-error slowing; they also exhibited reduced error-related negativity (ERN) and error positivity effects, and reduced N2 and P3 congruency effects. Age effects were observed across groups: with increasing age, participants responded faster, with less variability, and with increased post-error slowing. They also exhibited increased ERN effects and increased N2 and P3 congruency effects. Increased RTV and reduced P3 amplitude in incongruent trials were associated with increased ADHD Problems Scale scores on the Child Behavior Checklist across groups. The altered behavioral and ERP responses in ADHD are consistent with the pattern associated with younger age across groups. Further research with a longitudinal design may determine specific aspects of developmental alteration and deficits in ADHD during performance monitoring.

Error-Related Dynamics of Reaction Time and Frontal Midline Theta Activity in Attention Deficit Hyperactivity Disorder (ADHD) During a Subliminal Motor Priming Task

Post-error slowing (PES) is an established performance monitoring readout. Several previous studies have found that PES is reduced in children and adolescents with attention-deficit hyperactivity disorder (ADHD). We analyzed reaction time data, along with electroencephalography (EEG) data, from a response priming experiment in children and adolescents with ADHD (N = 28) and typically developing (TD) controls (N = 15) between 10 and 17 years of age. We report dynamic reaction time changes before and after errors: whereas TD controls readjusted their response speed to their individual average speed after committing an error, this reaction time adjustment appeared to be delayed and decreased in ADHD patients. In the EEG, error trials were accompanied by increased frontal midline theta activity, which was attenuated in ADHD compared to TD. We conclude that PES has a different time course rather than being fully absent in ADHD and discuss relationships with our EEG findings and potential implications for performance monitoring in ADHD.

Impairments in error processing and their association with ADHD symptoms in individuals born preterm

Preterm birth is associated with heightened risk for attention-deficit/hyperactivity disorder (ADHD)-like symptoms and neurocognitive impairments, including impairments in performance monitoring. Here, we investigate the cognitive and neurophysiological processes from a performance-monitoring task in preterm-born adolescents and examine whether these processes in preterm-born adolescents reflect identical neurophysiological impairments to those observed in term-born adolescents with ADHD. We compared 186 preterm-born individuals to 69 term-born individuals with ADHD and 135 term-born controls on cognitive-performance measures and event-related potentials (ERPs) of conflict monitoring (N2) and error processing (ERN, Pe) from a flanker task. Preterm-born adolescents demonstrated reduced N2, ERN and Pe amplitudes, compared to controls, and similar ERN and Pe impairments to term-born adolescents with ADHD. While ADHD symptoms correlated with ERN amplitude at FCz among the preterm-born, ERN amplitude at Fz, N2 and Pe amplitude were not associated with ADHD symptoms. Preterm-born individuals show impairments on neurophysiological indices of conflict monitoring (N2) and error processing (ERN and Pe). Early neurophysiological error processing may be a marker underlying the processes linked to the increased risk for ADHD among preterm-born individuals. Error detection processes are malleable and potential targets for non-pharmacological interventions. Preterm-born individuals are likely to benefit from early interventions.

Effect of Anodal and Cathodal Transcranial Direct Current Stimulation on DLPFC on Modulation of Inhibitory Control in ADHD

OBJECTIVE

The purpose of this study was to improve the inhibitory control functions through transcranial direct current stimulation (tDCS) in adolescents with ADHD symptoms.

METHOD

Twenty high school students with ADHD symptoms participated in this single-blinded, crossover, sham-controlled study. All the participants were tested during the application of Stroop and Go/No-Go tasks that is used to measure inhibitory control, using 1.5 mA of tDCS for 15 min over the left dorsolateral prefrontal cortex (DLPFC).

RESULTS

Anodal stimulation on left DLPFC had no effect on interference inhibition during the Stroop task and increased the proportion of correct responses in the "Go stage" of the Go/No-Go test compared with sham condition. Cathodal stimulation on the left DLPFC increased the inhibition accuracy in the inhibition stage during Go/No-Go task in comparison with sham.

CONCLUSION

tDCS over the left DLPFC of adolescents who suffer from ADHD symptoms can improve inhibitory control in prepotent response inhibition.

Cognitive Control Over Visual Motion Processing - Are Children With ADHD Especially Compromised? A Pilot Study of Flanker Task Event-Related Potentials

Performance deficits and diminished brain activity during cognitive control and error processing are frequently reported in attention deficit/hyperactivity disorder (ADHD), indicating a “top-down” deficit in executive attention. So far, these findings are almost exclusively based on the processing of static visual forms, neglecting the importance of visual motion processing in everyday life as well as important attentional and neuroanatomical differences between processing static forms and visual motion. For the current study, we contrasted performance and electrophysiological parameters associated with cognitive control from two Flanker-Tasks using static stimuli and moving random dot patterns. Behavioral data and event-related potentials were recorded from 16 boys with ADHD (combined type) and 26 controls (aged 8–15 years). The ADHD group showed less accuracy especially for moving stimuli, and prolonged response times for both stimulus types. Analyses of electrophysiological parameters of cognitive control revealed trends for diminished N2-enhancements and smaller error-negativities (indicating medium effect sizes), and we detected significantly lower error positivities (large effect sizes) compared to controls, similarly for both static and moving stimuli. Taken together, the study supports evidence that motion processing is not fully developed in childhood and that the cognitive control deficit in ADHD is of higher order and independent of stimulus type.

Beneficial effects of acute high-intensity exercise on electrophysiological indices of attention processes in young adult men

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High-intensity exercise improved brain measures of attention processes.

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Fitness and physical activity level were not related to degree of improvement.

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We found no effects of exercise on subsequent Flanker and Reaction-time tasks.

Background

Emerging research suggests that a single bout of aerobic exercise can improve cognition, brain function and psychological health. Our aim was to examine the effects of high-intensity exercise on cognitive-performance and brain measures of attention, inhibition and performance-monitoring across a test-battery of three cognitive tasks.

Method

Using a randomised cross-over design, 29 young men completed three successive cognitive tasks (Cued Continuous Performance Task [CPT-OX]; Eriksen Flanker Task; four-choice reaction-time task [Fast Task]) with simultaneous electroencephalogram (EEG) recording before and after a 20-min high-intensity cycling exercise and resting control session. Cognitive-performance measures, EEG power and event-related potential measures, were obtained during the tasks. Random-intercept linear models were used to investigate the effects of exercise, compared to rest, on outcomes.

Results

A single bout of exercise significantly (p < 0.05) increased the amplitude of the event-related potential Go P3, but had no effect on the contingent negative variation (CNV), Cue P3 or NoGo P3, during the CPT-OX. Delta power, recorded during the CPT-OX, also significantly increased after exercise, whereas there was no effect on cognitive-performance in this task. Exercise did not influence any cognitive-performance or brain measures in the subsequent Flanker or Fast Tasks.

Conclusion

Acute high-intensity exercise improves brain-indices reflecting executive and sustained attention during task performance (Go P3 and delta activity), in the CPT-OX, but not anticipatory attention (Cue P3 and CNV) or response inhibition (NoGo P3) in young-adult men. Exercise had no effect on cognitive-performance or brain measures in the subsequent Flanker and Fast tasks, which may potentially be explained by the time delay after exercise.

Performance monitoring and post-error adjustments in adults with attention-deficit/hyperactivity disorder: an EEG analysis

BACKGROUND

Recently, research into attention-deficit/hyperactivity disorder (ADHD) has focused increasingly on its neurobiological underpinnings, revealing (among other things) frontal lobe alterations. Specifically, action-monitoring deficits have been described, including impaired behavioural adjustments following errors. Our aim was to examine the neurophysiological background of post-error behavioural alterations in an adult ADHD sample for the first time, hypothesizing that people with ADHD would differ from controls in neurophysiological markers of cognitive preparation and stimulus processing, specifically following errors.

METHODS

In total, 34 people with ADHD and 34 controls participated in an electroencephalography measurement while performing a flanker task. The final number of electroencephalography samples included in the analyses ranged from 23 to 28. We recorded event-related potentials for the erroneous response itself (error-related negativity) and for events following errors (intertrial interval: contingent negative variation; next flanker stimulus: P300).

RESULTS

Over frontal electrode sites, error-related negativity amplitudes were significantly reduced in people with ADHD across response conditions. Both groups showed reduced P300 amplitudes on flanker stimuli following errors. Moreover, during the intertrial interval, patients exhibited significantly reduced contingent negative variation, specifically following errors. At the behavioural level, we observed no significant group differences in post-error data.

LIMITATIONS

Only adults were examined (no longitudinal data).

CONCLUSION

Based on previous reports of post-error behavioural alterations in childhood samples, we conclude that people with ADHD develop compensatory strategies across the lifespan that lead to inconspicuous post-error behaviour in adulthood. Neurophysiologically, however, subtle alterations remain, indicating a perseverance of at least some frontal lobe deficits in people with ADHD who are partially medicated, particularly with respect to action-monitoring and post-error adaptation.

Live fast, die young? A review on the developmental trajectories of ADHD across the lifespan

Attention-deficit/hyperactivity disorder (ADHD) is highly heritable and the most common neurodevelopmental disorder in childhood. In recent decades, it has been appreciated that in a substantial number of cases the disorder does not remit in puberty, but persists into adulthood. Both in childhood and adulthood, ADHD is characterised by substantial comorbidity including substance use, depression, anxiety, and accidents. However, course and symptoms of the disorder and the comorbidities may fluctuate and change over time, and even age of onset in childhood has recently been questioned. Available evidence to date is poor and largely inconsistent with regard to the predictors of persistence versus remittance. Likewise, the development of comorbid disorders cannot be foreseen early on, hampering preventive measures. These facts call for a lifespan perspective on ADHD from childhood to old age. In this selective review, we summarise current knowledge of the long-term course of ADHD, with an emphasis on clinical symptom and cognitive trajectories, treatment effects over the lifespan, and the development of comorbidities. Also, we summarise current knowledge and important unresolved issues on biological factors underlying different ADHD trajectories. We conclude that a severe lack of knowledge on lifespan aspects in ADHD still exists for nearly every aspect reviewed. We encourage large-scale research efforts to overcome those knowledge gaps through appropriately granular longitudinal studies.

The Neurocognitive Profile of Attention-Deficit/Hyperactivity Disorder: A Review of Meta-Analyses

Objective

Numerous meta-analyses have summarized studies comparing the neurocognitive performance of individuals with attention-deficit/hyperactivity disorder (ADHD) to that of healthy controls.

Method

The present study is a systematic review and quantitative summary of those meta-analyses that aimed to determine the extent to which individuals with ADHD differ cognitively from typically developing controls.

Results

Of 253 standardized mean differences (SMDs) drawn from 34 meta-analyses, 244 (96%) were positive, indicating better neurocognitive performance in the control group than the ADHD group. The mean effect size was .45 (SD = .27). Unweighted means of SMDs for neurocognitive domains ranged from .35 (set shifting) to .54 (working memory). When weighted by the number of studies aggregated, they ranged from .35 (set shifting) to .66 (reaction time variability). Neurocognitive domains with mean effects over .50 included working memory (.54), reaction time variability (.53), response inhibition (.52), intelligence/achievement (.51), and planning/organization (.51). When weighted by number of aggregated studies, the domains with mean effects over .50 were reaction time variability (.66), intelligence/achievement (.60), vigilance (.56), working memory (.54), and response inhibition (.52). Age moderated the relationship between ADHD diagnosis and neurocognitive functioning, with greater between-groups differences among children and adults than among adolescents. Funding also moderated this relationship: meta-analyses that received drug funding found larger effect sizes than those without drug funding.

Conclusions

The evidence suggests that ADHD is associated with substantial deficits across a variety of neurocognitive domains. This is the most in-depth review of the neurocognitive functioning of people with ADHD to date.

The Significance of Impulsive Error in Children With ADHD

A deficit of inhibition ability is a neuropsychological problem in children with attention deficit hyperactivity disorder (ADHD). We investigated whether in children who made impulsive error (IE), less error-related negativity (ERN) would correlate with poorer executive attention functions (EAFs). Ninety children (49 with ADHD and 41 without ADHD) were investigated by a 4-minute simple reaction time task and simultaneous electroencephalogram. When they made IE, the ERN in response-locked event-related potential (ERP) was defined as error awareness. The average area under curve of ERN in the control group with IEs was used as the proper criterion for regrouping the children with ADHD into 2 groups: ADHD children with enough ERN (ADHD-enough ERN) and those with less ERN (ADHD-less ERN). EAFs from Comprehensive Nonverbal Attention Test were used as objective indices, and behavioral questionnaires were used as subjective indices and statistically analyzed within ADHD groups. Forty-eight percent of the children made IEs. ADHD(n = 31, 63%) was significantly more than in the control group (n = 12, 29%; P < .001). The ADHD group had significantly less ERN than did the control group while making IE, especially at frontal and central electrodes ( P < .01). Both ADHD-less ERN and ADHD-enough ERN groups had poorer subjective EAFs on questionnaires. Only the ADHD-less ERN group had significant poorer objective EAFs on the Comprehensive Nonverbal Attention Test than did the ADHD without IE. We conclude that investigating the IE and ERN of IE in children with ADHD might help to differentiate subtypes of ADHD with different neuropsychological abilities, and the possibility that ADHD-less ERN children might be confirmed a meaningful subgroup that needs close follow-up, treatments different from standard, or both.

Event-Related-Potential (ERP) Correlates of Performance Monitoring in Adults With Attention-Deficit Hyperactivity Disorder (ADHD)

Introduction: Attention-deficit hyperactivity disorder (ADHD) is one of the most frequent neurodevelopmental disorders in children and tends to persist into adulthood. Evidence from neuropsychological, neuroimaging, and electrophysiological studies indicates that alterations of error processing are core symptoms in children and adolescents with ADHD. To test whether adults with ADHD show persisting deficits and compensatory processes, we investigated performance monitoring during stimulus-evaluation and response-selection, with a focus on errors, as well as within-group correlations with symptom scores. Methods: Fifty-five participants (27 ADHD and 28 controls) aged 19-55 years performed a modified flanker task during EEG recording with 64 electrodes, and the ADHD and control groups were compared on measures of behavioral task performance, event-related potentials of performance monitoring (N2, P3), and error processing (ERN, Pe). Adult ADHD Self-Report Scale (ASRS) was used to assess ADHD symptom load. Results: Adults with ADHD showed higher error rates in incompatible trials, and these error rates correlated positively with the ASRS scores. Also, we observed lower P3 amplitudes in incompatible trials, which were inversely correlated with symptom load in the ADHD group. Adults with ADHD also displayed reduced error-related ERN and Pe amplitudes. There were no significant differences in reaction time (RT) and RT variability between the two groups. Conclusion: Our findings show deviations of electrophysiological measures, suggesting reduced effortful engagement of attentional and error-monitoring processes in adults with ADHD. Associations between ADHD symptom scores, event-related potential amplitudes, and poorer task performance in the ADHD group further support this notion.

Development of Performance and ERPs in a Flanker Task in Children and Adolescents with Tourette Syndrome-A Follow-Up Study

Background: Tourette Syndrome (TS) is a neurodevelopmental disorder with childhood-onset, with a typical decline in tic severity, as well as an increasing ability to suppress tics in late childhood and adolescence. These processes develop in parallel with general improvement of self-regulatory abilities, and performance monitoring during this age-span. Hence, changes in performance monitoring over time might provide insight into the regulation of tics in children and adolescents with TS.

Method: We measured reaction time, reaction time variability, accuracy, and event-related potentials (ERP) in 17 children with TS, including 10 children with comorbid Attention-Deficit/Hyperactivity Disorder (ADHD), 24 children with ADHD, and 29 typically developing children, using a modified Eriksen Flanker task in two testing sessions administered on average 4.5 years apart. We then compared task performance, as well as ERP components across groups, and over time using regression models.

Results: Task performance improved in all groups with age, and behavioral differences between children with TS and controls diminished at second assessment, while differences between controls and children with ADHD largely persisted. In terms of ERP, the early P3 developed earlier in children with TS compared with controls at the first assessment, but trajectories converged with maturation. ERP component amplitudes correlated with worst-ever tic scores.

Conclusions: Merging trajectories between children with TS and controls are consistent with the development of compensatory self-regulation mechanisms during early adolescence, probably facilitating tic suppression, in contrast to children with ADHD. Correlations between ERP amplitudes and tic scores also support this notion.

Endophenotype best practices

This review examines the current state of electrophysiological endophenotype research and recommends best practices that are based on knowledge gleaned from the last decade of molecular genetic research with complex traits. Endophenotype research is being oversold for its potential to help discover psychopathology relevant genes using the types of small samples feasible for electrophysiological research. This is largely because the genetic architecture of endophenotypes appears to be very much like that of behavioral traits and disorders: they are complex, influenced by many variants (e.g., tens of thousands) within many genes, each contributing a very small effect. Out of over 40 electrophysiological endophenotypes covered by our review, only resting heart, a measure that has received scant advocacy as an endophenotype, emerges as an electrophysiological variable with verified associations with molecular genetic variants. To move the field forward, investigations designed to discover novel variants associated with endophenotypes will need extremely large samples best obtained by forming consortia and sharing data obtained from genome wide arrays. In addition, endophenotype research can benefit from successful molecular genetic studies of psychopathology by examining the degree to which these verified psychopathology-relevant variants are also associated with an endophenotype, and by using knowledge about the functional significance of these variants to generate new endophenotypes. Even without molecular genetic associations, endophenotypes still have value in studying the development of disorders in unaffected individuals at high genetic risk, constructing animal models, and gaining insight into neural mechanisms that are relevant to clinical disorder.

Attention-Deficit/Hyperactivity Disorder Remission Is Linked to Better Neurophysiological Error Detection and Attention-Vigilance Processes

BACKGROUND

The processes underlying persistence and remission of attention-deficit/hyperactivity disorder (ADHD) are poorly understood. We examined whether cognitive and neurophysiological impairments on a performance-monitoring task distinguish between ADHD persisters and remitters.

METHODS

On average 6 years after initial assessment, 110 adolescents and young adults with childhood ADHD (87 persisters, 23 remitters) and 169 age-matched control participants were compared on cognitive-performance measures and event-related potentials of conflict monitoring (N2) and error processing (error-related negativity and positivity) from an arrow flanker task with low-conflict and high-conflict conditions. ADHD outcome was examined with parent-reported symptoms and functional impairment measures using a categorical (DSM-IV) and a dimensional approach.

RESULTS

ADHD persisters were impaired compared with controls on all cognitive-performance and event-related potential measures (all p < .05). ADHD remitters differed from persisters and were indistinguishable from control participants on the number of congruent (low-conflict) errors, reaction time variability, error-related negativity, and error-related positivity (all p ≤ .05). Remitters did not differ significantly from the other groups on incongruent (high-conflict) errors, mean reaction time, and N2. In dimensional analyses on all participants with childhood ADHD, ADHD symptoms and functional impairment at follow-up were significantly correlated with congruent errors, reaction time variability, and error-related positivity (r = .19-.23, p ≤ .05).

CONCLUSIONS

Cognitive and neurophysiological measures of attention-vigilance and error detection distinguished ADHD remitters from persisters. These results extend our previous findings with other tasks and indicate that such measures are markers of remission and candidates for the development of nonpharmacological interventions.

Evaluating the consequences of impaired monitoring of learned behavior in attention-deficit/hyperactivity disorder using a Bayesian hierarchical model of choice response time

OBJECTIVE

Performance monitoring deficits have been proposed as a cognitive marker involved in the development of attention-deficit/hyperactivity disorder (ADHD), but it is unclear whether these deficits cause impairment when established action sequences conflict with environmental demands. The current study applies a novel data-analytic technique to a well-established sequence learning paradigm to investigate reactions to disruption of learned behavior in ADHD.

METHOD

Children (ages 8-12) with and without ADHD completed a serial reaction time task in which they implicitly learned an 8-item sequence of keypresses over 5 training blocks. The training sequence was replaced with a novel sequence in a transfer block, and returned in 2 subsequent recovery blocks. Response time (RT) data were fit by a Bayesian hierarchical version of the linear ballistic accumulator model, which permitted the dissociation of learning processes from performance monitoring effects on RT.

RESULTS

Sequence-specific learning on the task was reflected in the systematic reduction of the amount of evidence required to initiate a response, and was unimpaired in ADHD. When the novel sequence onset, typically developing children displayed a shift in their attentional state while children with ADHD did not, leading to worse subsequent performance compared to controls.

CONCLUSIONS

Children with ADHD are not impaired in learning novel action sequences, but display difficulty monitoring their implementation and engaging top-down control when they become inadequate. These results support theories of ADHD that highlight the interactions between monitoring processes and changing cognitive demands as the cause of self-regulation and information-processing problems in the disorder. (PsycINFO Database Record

Classifying adolescent attention-deficit/hyperactivity disorder (ADHD) based on functional and structural imaging

Attention-deficit/hyperactivity disorder (ADHD) is a common disabling psychiatric disorder associated with consistent deficits in error processing, inhibition and regionally decreased grey matter volumes. The diagnosis is based on clinical presentation, interviews and questionnaires, which are to some degree subjective and would benefit from verification through biomarkers. Here, pattern recognition of multiple discriminative functional and structural brain patterns was applied to classify adolescents with ADHD and controls. Functional activation features in a Flanker/NoGo task probing error processing and inhibition along with structural magnetic resonance imaging data served to predict group membership using support vector machines (SVMs). The SVM pattern recognition algorithm correctly classified 77.78% of the subjects with a sensitivity and specificity of 77.78% based on error processing. Predictive regions for controls were mainly detected in core areas for error processing and attention such as the medial and dorsolateral frontal areas reflecting deficient processing in ADHD (Hart et al., in Hum Brain Mapp 35:3083-3094, 2014), and overlapped with decreased activations in patients in conventional group comparisons. Regions more predictive for ADHD patients were identified in the posterior cingulate, temporal and occipital cortex. Interestingly despite pronounced univariate group differences in inhibition-related activation and grey matter volumes the corresponding classifiers failed or only yielded a poor discrimination. The present study corroborates the potential of task-related brain activation for classification shown in previous studies. It remains to be clarified whether error processing, which performed best here, also contributes to the discrimination of useful dimensions and subtypes, different psychiatric disorders, and prediction of treatment success across studies and sites.

Error-processing abnormalities in pediatric anxiety and obsessive compulsive disorders

Anxiety and obsessive compulsive disorders are among the earliest occurring psychopathology and may derive from atypical maturation of neural networks for error processing. Psychological models have alternately suggested that over-detection of errors, excessive caring about errors, or failure of errors to elicit regulatory control could associate with the expression of anxiety. In this review article, the potential relevance of error processing for anxiety and obsessive compulsive disorders is described in the context of neurophysiological and functional magnetic resonance imaging (fMRI) research demonstrating altered brain response to errors in pediatric and adult patients. Finally, hypotheses about developmentally sensitive mechanisms of anxiety and obsessive compulsive disorders are drawn from the extant literature, and avenues for clinical translation are discussed.

Probabilistic reward learning in adults with Attention Deficit Hyperactivity Disorder--an electrophysiological study

Attention Deficit Hyperactivity Disorder (ADHD) is hypothesized to be characterized by altered reinforcement sensitivity. The main aim of the present study was to assess alterations in the electrophysiological correlates of monetary reward processing in adult patients with ADHD of the combined subtype. Fourteen adults with ADHD of the combined subtype and 14 healthy control participants performed an active and an observational probabilistic reward-based learning task while an electroencephalogramm (EEG) was recorded. Regardless of feedback valence, there was a general feedback-related negativity (FRN) enhancement in combination with reduced learning performance during both active and observational reward learning in patients with ADHD relative to healthy controls. Other feedback-locked potentials such as the P200 and P300 and response-locked potentials were unaltered in the patients. There were no significant correlations between learning performance, FRN amplitudes and clinical symptoms, neither in the overall group involving all participants, nor in patients or controls considered separately. This pattern of findings might reflect generally impaired reward prediction in adults with ADHD of the combined subtype. We demonstrated for the first time that patients with ADHD of the combined subtype show not only deficient active reward learning but are also impaired when learning by observing other people׳s outcomes.

Differential oscillatory electroencephalogram between attention-deficit/hyperactivity disorder subtypes and typically developing adolescents

BACKGROUND

A neurobiological-based classification of attention-deficit/hyperactivity disorder (ADHD) subtypes has thus far remained elusive. The aim of this study was to use oscillatory changes in the electroencephalogram (EEG) related to informative cue processing, motor preparation, and top-down control to investigate neurophysiological differences between typically developing (TD) adolescents, and those diagnosed with predominantly inattentive (IA) or combined (CB) (associated with symptoms of inattention as well as impulsivity/hyperactivity) subtypes of ADHD.

METHODS

The EEG was recorded from 57 rigorously screened adolescents (12 to 17 years of age; 23 TD, 17 IA, and 17 CB), while they performed a cued flanker task. We examined the oscillatory changes in theta (3-5 Hz), alpha (8-12 Hz), and beta (22-25 Hz) EEG bands after cues that informed participants with which hand they would subsequently be required to respond.

RESULTS

Relative to TD adolescents, the IA group showed significantly less postcue alpha suppression, suggesting diminished processing of the cue in the visual cortex, whereas the CB group showed significantly less beta suppression at the electrode contralateral to the cued response hand, suggesting poor motor planning. Finally, both ADHD subtypes showed weak functional connectivity between frontal theta and posterior alpha, suggesting common top-down control impairment.

CONCLUSIONS

We found both distinct and common task-related neurophysiological impairments in ADHD subtypes. Our results suggest that task-induced changes in EEG oscillations provide an objective measure, which in conjunction with other sources of information might help distinguish between ADHD subtypes and therefore aid in diagnoses and evaluation of treatment.

The neurobiological link between OCD and ADHD

Obsessive compulsive disorder (OCD) and attention deficit hyperactivity disorder (ADHD) are two of the most common neuropsychiatric diseases in paediatric populations. The high comorbidity of ADHD and OCD with each other, especially of ADHD in paediatric OCD, is well described. OCD and ADHD often follow a chronic course with persistent rates of at least 40–50 %. Family studies showed high heritability in ADHD and OCD, and some genetic findings showed similar variants for both disorders of the same pathogenetic mechanisms, whereas other genetic findings may differentiate between ADHD and OCD. Neuropsychological and neuroimaging studies suggest that partly similar executive functions are affected in both disorders. The deficits in the corresponding brain networks may be responsible for the perseverative, compulsive symptoms in OCD but also for the disinhibited and impulsive symptoms characterizing ADHD. This article reviews the current literature of neuroimaging, neurochemical circuitry, neuropsychological and genetic findings considering similarities as well as differences between OCD and ADHD.

Monoaminergic modulation of behavioural and electrophysiological indices of error processing

RATIONALE

Error processing is a critical executive function that is impaired in a large number of clinical populations. Although the neural underpinnings of this function have been investigated for decades and critical error-related components in the human electroencephalogram (EEG), such as the error-related negativity (ERN) and the error positivity (Pe), have been characterised, our understanding of the relative contributions of key neurotransmitters to the generation of these components remains limited.

OBJECTIVES

The current study sought to determine the effects of pharmacological manipulation of the dopamine, noradrenaline and serotonin neurotransmitter systems on key behavioural and event-related potential correlates of error processing.

METHODS

A randomised, double-blinded, placebo-controlled, crossover design was employed. Monoamine levels were manipulated using the clinically relevant drugs methylphenidate, atomoxetine and citalopram, in comparison to placebo. Under each of the four drug conditions, participants underwent EEG recording while performing a flanker task.

RESULTS

Only methylphenidate produced significant improvement in performance accuracy, which was without concomitant slowing of reaction time. Methylphenidate also increased the amplitude of an early electrophysiological index of error processing, the ERN. Citalopram increased the amplitude of the correct-response negativity, another component associated with response processing.

CONCLUSIONS

The effects of methylphenidate in this study are consistent with theoretical accounts positing catecholamine modulation of error monitoring. Our data suggest that enhancing catecholamine function has the potential to remediate the error-monitoring deficits that are seen in a wide range of psychiatric conditions.

The effects of performance-based rewards on neurophysiological correlates of stimulus, error, and feedback processing in children with ADHD

Rewards have been shown to improve behavior and cognitive processes implicated in attention-deficit hyperactivity disorder (ADHD), but the information-processing mechanisms by which these improvements occur remain unclear. We examined the effect of performance-based rewards on ERPs related to processing of the primary task stimuli, errors, and feedback in children with ADHD and typically developing controls. Participants completed a flanker task containing blocks with and without performance-based rewards. Children with ADHD showed reduced amplitude of ERPs associated with processing of the flanker stimuli (P3) and errors (ERN, Pe), but did not differ in feedback-processing (FRN). Rewards enhanced flanker-related P3 amplitude similarly across groups and error-related Pe amplitude differentially for children with ADHD. These findings suggest that rewards may improve cognitive deficits in children with ADHD through enhanced processing of relevant stimuli and increased error evaluation.

Psychosocial deprivation, executive functions, and the emergence of socio-emotional behavior problems

Early psychosocial deprivation can negatively impact the development of executive functions (EFs). Here we explore the impact of early psychosocial deprivation on behavioral and physiological measures (i.e., event-related potentials; ERPs) of two facets of EF, inhibitory control and response monitoring, and their associations with internalizing and externalizing outcomes in the Bucharest Early Intervention Project (BEIP; Zeanah et al., 2003). This project focuses on two groups of children placed in institutions shortly after birth and then randomly assigned in infancy to either a foster care intervention or to remain in their current institutional setting. A group of community controls was recruited for comparison. The current study assesses these children at 8-years of age examining the effects of early adversity, the potential effects of the intervention on EF and the role of EF skills in socio-emotional outcomes. Results reveal exposure to early psychosocial deprivation was associated with impaired inhibitory control on a flanker task. Children in the foster care intervention exhibited better response monitoring compared to children who remained in the institution on the error-related positivity (Pe). Moreover, among children in the foster care intervention those who exhibited larger error-related negativity (ERN) responses had lower levels of socio-emotional behavior problems. Overall, these data identify specific aspects of EF that contribute to adaptive and maladaptive socio-emotional outcomes among children experiencing early psychosocial deprivation.