Increased event-related theta activity as a psychophysiological marker of comorbidity in children with tics and attention-deficit/hyperactivity disorders

Additive and Interactive Effects of Attention-Deficit/Hyperactivity Disorder and Tic Disorder on Brain Connectivity

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) and persistent tic disorder (PTD) are two neurodevelopmental disorders that frequently co-occur. Contributions of each disorder to cognitive and behavioral deficits have been reported. In this paper, we tested 3 models of pathophysiology for the two disorders (additive, interactive, and phenotypic) using resting-state connectivity associated with each disorder separately and together.

METHODS

Participants were 148 children (55 with ADHD only, 33 with ADHD and PTD, 27 with PTD only, and 33 healthy control subjects) at ages 8 to 12 years. Following diagnostic interviews and behavioral assessment, participants underwent a 128-channel electroencephalography recording. Resting-state, cortical source-level effective connectivity was analyzed across the 4 groups using a 2 × 2 factorial design with factors of ADHD (with/without) and PTD (with/without).

RESULTS

ADHD diagnosis was the primary driver of cognitive and behavioral deficits, while deficits associated with PTD were primarily with thought problems and internalizing problems when compared with controls. Subadditive effects were observed in co-occurring ADHD+PTD for parent-rated behavioral problems and cognitive functions. Aberrant effective connectivity was primarily associated with ADHD, more specifically with lower posterior and occipital-frontal connectivity, while children with PTD exhibited greater left postcentral to precuneus connectivity. Weaker ADHD-related connectivity was associated with more severe behavioral problems, including internalizing behaviors, thought problems, and working memory deficits.

CONCLUSIONS

Similar to general behavioral deficits, aberrant resting-state neural connectivity in pediatric ADHD and PTD combines additively in co-occurring cases. The findings of this study support ADHD as a focus of treatment in comorbid cases, given the driving role of ADHD in both behavioral and neurophysiological deficits.

Co-Occurrence of Tic Disorders and Attention-Deficit/Hyperactivity Disorder-Does It Reflect a Common Neurobiological Background?

BACKGROUND

The co-existence of tic disorders and attention-deficit/hyperactivity disorder (TD + ADHD) has proven to be highly important in daily clinical practice. The factor ADHD is not only associated with further comorbidities, but also has a long-term negative psychosocial effect, while the factor TD is usually less disturbing for the major part of the patients. It remains unclear how far this is related to a different neurobiological background of the associated disorders or whether TD + ADHD reflects a common one.

OBJECTIVE

This review provides an update on the neurobiological background of TD + ADHD in order to better understand and treat this clinical problem, while clarifying whether an additive model of TD + ADHD holds true and should be used as a basis for further clinical recommendations.

METHOD

A comprehensive research of the literature was conducted and analyzed, including existing clinical guidelines for both TD and ADHD. Besides genetical and environmental risk factors, brain structure and functions, neurophysiological processes and neurotransmitter systems were reviewed.

RESULTS

Only a limited number of empirical studies on the neurobiological background of TD and ADHD have taken the peculiarity of co-existing TD + ADHD into consideration, and even less studies have used a 2 × 2 factorial design in order to disentangle the impact/effects of the factors of TD versus those of ADHD. Nevertheless, the assumption that TD + ADHD can best be seen as an additive model at all levels of investigation was strengthened, although some overlap of more general, disorder non-specific aspects seem to exist.

CONCLUSION

Beyond stress-related transdiagnostic aspects, separate specific disturbances in certain neuronal circuits may lead to disorder-related symptoms inducing TD + ADHD in an additive way. Hence, within a classificatory categorical framework, the dimensional aspects of multilevel diagnostic-profiling seem to be a helpful precondition for personalized decisions on counselling and disorder-specific treatment in TD + ADHD.

Associations of Hyperactivity and Inattention Scores with Theta and Beta Oscillatory Dynamics of EEG in Stop-Signal Task in Healthy Children 7-10 Years Old

Simple Summary

Most studies on ADHD have been focused on the comparisons between healthy subjects and clinical patients. The dimensional approaches propose that the main pathological behavioral domains are distributed in the normal population and not only in individual categories of people (as assumed in traditional schemes of comparisons between patients and controls). In the current study, we used a similar approach to identify potential markers of ADHD by studying the EEG dynamics of healthy children with a natural variability in hyperactivity and inattention scores during performance of the Stop-Signal task. We found that hyperactivity/inattention scores were positively associated with RT variability. Hyperactivity/inattention scores were negatively associated with an increase in beta spectral power in the first 200 ms and positively associated with an increase in theta rhythm at about 300 ms after presentation of the Go stimulus. It has been hypothesized that such results imply insufficient vigilance in the early stages of perception and subsequent compensatory enhancing of attention to the stimulus in children with higher hyperactivity and inattention scores.

Abstract

In the current study, we aimed to investigate the associations between the natural variability in hyperactivity and inattention scores, as well as their combination with EEG oscillatory responses in the Stop-Signal task in a sample of healthy children. During performance, the Stop-Signal task EEGs were recorded in 94 Caucasian children (40 girls) from 7 to 10 years. Hyperactivity/inattention and inattention scores positively correlated with RT variability. Hyperactivity/inattention and inattention scores negatively correlated with an increase in beta spectral power in the first 200 ms after presentation of the Go stimulus. Such results are in line with the lack of arousal model in ADHD children and can be associated with less sensory arousal in the early stages of perception in children with symptoms of inattention. The subsequent greater increase in theta rhythm at about 300 ms after presentation of the Go stimulus in children with higher inattention scores may be associated with increased attention processes and compensation for insufficient vigilance in the early stages of perception.

Electrophysiology Echoes Brain Dynamics in Children and Adolescents With Tourette Syndrome-A Developmental Perspective

The development of the complex clinical picture of motor and vocal tics in children and adolescents with Tourette syndrome (TS) must be paralleled by changes in the underlying pathophysiology. Electrophysiological methods such as EEG and event-related potentials (ERPs) are non-invasive, safe and easy to apply and thus seem to provide an adequate means to investigate brain dynamics during this brain maturational period. Also, electrophysiology is characterized by a high time resolution and can reflect motor, sensory and cognitive aspects as well as sleep behavior. Hence, this narrative review focuses on how electrophysiology echoes brain dynamics during development of youngsters with TS and might be useful for the treatment of tics. A comprehensive picture of developmental brain dynamics could be revealed showing that electrophysiological parameters evolve concurrently with clinical characteristics of TS. Specifically, evidence for a maturational delay of motor inhibition related to cortico-spinal hyper-excitability and brain mechanisms for its cognitive compensation could be shown. Moreover, deviant sleep parameters and probably a stronger perception-action binding were reported. For neuromodulatory treatments (e.g., neurofeedback; repetitive transcranial magnetic stimulation, rTMS/transcranial direct current stimulation, tDCS) targeting neuronal deficits and/or strengthening compensatory brain mechanisms, pilot studies support the possibility of positive effects regarding tic reduction. Finally, attention-deficit/hyperactivity disorder (ADHD), as a highly frequent co-existing disorder with TS, has to be considered when using and interpreting electrophysiological measures in TS. In conclusion, application of electrophysiology seems to be promising regarding clinical and research aspects in youngsters with TS.

Potential Role of ADRA2A Genetic Variants in the Etiology of ADHD Comorbid With Tic Disorders

Objective: To evaluate the role of the adrenergic receptor alpha-2A gene (ADRA2A) in the genetic etiology of ADHD comorbid with tic disorders (ADHD+TD). Method: Two single nucleotide polymorphisms (SNPs) of ADRA2A were genotyped and analyzed in 936 normal controls and 1,815 ADHD probands, including 1,249 trios. Approximately 16% of the ADHD probands also had a diagnosis of TD. Results: No significant association was found between ADRA2A and ADHD in general. Case-control analyses indicated different allelic and genotypic distributions of rs553668 between ADHD+TD and controls in males. Family-based association tests showed that the G allele of rs1800544, the A allele of rs553668, and the GA haplotype consisting of these two SNPs were overtransmitted in the ADHD+TD trios, especially in males. Moreover, the allelic/genotypic distribution and allelic transmission were different between ADHD+TD and ADHD without TD. Conclusion:ADRA2A may be associated with ADHD+TD, especially in males.

Neural generators involved in visual cue processing in children with attention-deficit/hyperactivity disorder (ADHD)

Event-related potentials (ERP) studies report alterations in the ongoing visuo-attentional processes in children with attention-deficit/hyperactivity disorder (ADHD). We hypothesized that the neural generators progressively recruited after a cue stimulus imply executive-related areas well before engagement in executive processing in children with ADHD compared to typically developed children (TDC). We computed source localization (swLORETA) of the ERP and ERSP evoked by the Cue stimulus during a visual Cue-Go/Nogo paradigm in 15 ADHD compared to 16 TDC. A significant difference in N200/P200 amplitude over the right centro-frontal regions was observed between ADHD and TDC, supported by a stronger contribution of the left visuo-motor coordination area, premotor cortex, and prefrontal cortex in ADHD. In addition, we recorded a greater beta power spectrum in ADHD during the 80-230 ms interval, which was explained by increased activity in occipito-parieto-central areas and lower activity in the left supramarginal gyrus and prefrontal areas in ADHD. Successive analysis of the ERP generators (0-500 ms with successive periods of 50 ms) revealed significant differences beginning at 50 ms, with higher activity in the ventral anterior cingulate cortex, premotor cortex, and fusiform gyrus, and ending at 400-500 ms with higher activity of the dorsolateral prefrontal cortex and lower activity of the posterior cingulate cortex in ADHD compared to TDC. The areas contributing to ERP in ADHD and TDC differ from the early steps of visuo-attentional processing and reveal an overinvestment of the executive networks interfering with the activity of the dorsal attention network in children with ADHD.

Aggressive symptoms in children with tic disorders

Episodes of explosive anger and aggression are reported in patients with tic disorders and probably contribute to psychosocial stress and low quality of life. The source of these symptoms is controversial. The objective of the study was to study the relationship between tic disorders, their associated comorbidities, and aggressive behavior. The cohort included 47 children and adolescents (age 7-17 years) with Tourette syndrome or other chronic tic disorders attending a tertiary pediatric Tourette clinic. Associated psychopathology was assessed with the Yale Global Tic Severity Scale, Yale Brown Obsessive Compulsive Scale, Conners ADHD Rating Scale, Screen for Child Anxiety-Related Emotional Disorders, and Child Depression Inventory. Aggression was assessed with the Overt Aggression Scale and scores were compared with a group of 32 healthy age- and sex-matched children. There were no significant differences in aggression scores between the children with tic disorders and controls. Verbal aggression was the most prevalent type of aggression, found in 70% of the patients with tic disorders. The level of aggression was not correlated to tic severity. Comorbid attention-deficit hyperactivity disorder and obsessive-compulsive disorder increased the probability of aggressive behavior in patients with tic disorders. On regression analysis, the only significant predictor of aggression was the severity of attention-deficit hyperactivity disorder. This study suggests that there is no difference in aggressive behavior between children with tics without comorbidities and healthy children. It is possible that aggressive behavior in children with tic disorders is predominantly associated with comorbid attention-deficit hyperactivity disorder.

Deep Learning Convolutional Neural Networks Discriminate Adult ADHD From Healthy Individuals on the Basis of Event-Related Spectral EEG

Attention deficit hyperactivity disorder (ADHD) is a heterogeneous neurodevelopmental disorder that affects 5% of the pediatric and adult population worldwide. The diagnosis remains essentially clinical, based on history and exam, with no available biomarkers. In this paper, we describe a convolutional neural network (CNN) with a four-layer architecture combining filtering and pooling, which we train using stacked multi-channel EEG time-frequency decompositions (spectrograms) of electroencephalography data (EEG), particularly of event-related potentials (ERP) from ADHD patients (n = 20) and healthy controls (n = 20) collected during the Flanker Task, with 2800 samples for each group. We treat the data as in audio or image classification approaches, where deep networks have proven successful by exploiting invariances and compositional features in the data. The model reaches a classification accuracy of 88% ± 1.12%, outperforming the Recurrent Neural Network and the Shallow Neural Network used for comparison, and with the key advantage, compared with other machine learning approaches, of avoiding the need for manual selection of EEG spectral or channel features. The event-related spectrograms also provide greater accuracy compared to resting state EEG spectrograms. Finally, through the use of feature visualization techniques such as DeepDream, we show that the main features exciting the CNN nodes are a decreased power in the alpha band and an increased power in the delta-theta band around 100 ms for ADHD patients compared to healthy controls, suggestive of attentional and inhibition deficits, which have been previously suggested as pathophyisiological signatures of ADHD. While confirmation with larger clinical samples is necessary, these results suggest that deep networks may provide a useful tool for the analysis of EEG dynamics even from relatively small datasets, highlighting the potential of this methodology to develop biomarkers of practical clinical utility.

Neural activation and connectivity during cued eye blinks in Chronic Tic Disorders

Objective

The pathophysiology of Chronic Tic Disorders (CTDs), including Tourette Syndrome, remains poorly understood. The goal of this study was to compare neural activity and connectivity during a voluntary movement (VM) paradigm that involved cued eye blinks among children with and without CTDs. Using the precise temporal resolution of electroencephalography (EEG), we used the timing and location of cortical source resolved spectral power activation and connectivity to map component processes such as visual attention, cue detection, blink regulation and response monitoring. We hypothesized that neural activation and connectivity during the cued eye blink paradigm would be significantly different in regions typically associated with effortful control of eye blinks, such as frontal, premotor, parietal, and occipital cortices between children with and without CTD.

Method

Participants were 40 children (23 with CTD, 17 age-matched Healthy Control [HC]), between the ages of 8–12 (mean age = 9.5) years old. All participants underwent phenotypic assessment including diagnostic interviews, behavior rating scales and 128-channel EEG recording. Upon presentation of a cue every 3 s, children were instructed to make an exaggerated blink.

Results

Behaviorally, the groups did not differ in blink number, latency, or ERP amplitude. Within source resolved clusters located in left dorsolateral prefrontal cortex, posterior cingulate, and supplemental motor area, children with CTD exhibited higher gamma band spectral power relative to controls. In addition, significant diagnostic group differences in theta, alpha, and beta band power in inferior parietal cortex emerged. Spectral power differences were significantly associated with clinical characteristics such as tic severity and premonitory urge strength. After calculating dipole density for 76 anatomical regions, the CTD and HC groups had 70% overlap of top regions with the highest dipole density, suggesting that similar cortical networks were used across groups to carry out the VM. The CTD group exhibited significant information flow increase and dysregulation relative to the HC group, particularly from occipital to frontal regions.

Conclusion

Children with CTD exhibit abnormally high levels of neural activation and dysregulated connectivity among networks used for regulation and effortful control of voluntary eye blinks.

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First cortical source level EEG study on brain activity and connectivity in CTD.

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Children with CTD exhibit aberrant levels of neural activation and connectivity.

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Neural activation was significantly associated with tic severity and premonitory urge.

EEG Dynamics of a Go/Nogo Task in Children with ADHD

Background: Studies investigating event-related potential (ERP) evoked in a Cue-Go/NoGo paradigm have shown lower frontal N1, N2 and central P3 in children with attention-deficit/hyperactivity disorder (ADHD) compared to typically developing children (TDC). However, the electroencephalographic (EEG) dynamics underlying these ERPs remain largely unexplored in ADHD. Methods: We investigate the event-related spectral perturbation and inter-trial coherence linked to the ERP triggered by visual Cue-Go/NoGo stimuli, in 14 children (7 ADHD and 7 TDC) aged 8 to 12 years. Results: Compared to TDC, the EEG dynamics of children with ADHD showed a lower theta-alpha ITC concomitant to lower occipito-parietal P1-N2 and frontal N1-P2 potentials in response to Cue, Go and Nogo stimuli; an upper alpha power preceding lower central Go-P3; a lower theta-alpha power and ITC were coupled to a lower frontal Nogo-N3; a lower low-gamma power overall scalp at 300 ms after Go and Nogo stimuli. Conclusion: These findings suggest impaired ability in children with ADHD to conserve the brain oscillations phase associated with stimulus processing. This physiological trait might serve as a target for therapeutic intervention or be used as monitoring of their effects.

Synchronization of fronto-parietal beta and theta networks as a signature of visual awareness in neglect

In the neglect syndrome, the perceptual deficit for contra-lesional hemi-space is increasingly viewed as a dysfunction of fronto-parietal cortical networks, the disruption of which has been described in neuroanatomical and hemodynamic studies. Here we exploit the superior temporal resolution of electroencephalography (EEG) to study dynamic transient connectivity of fronto-parietal circuits at early stages of visual perception in neglect. As reflected by inter-regional phase synchronization in a full-field attention task, two functionally distinct fronto-parietal networks, in beta (15-25Hz) and theta (4-8Hz) frequency bands, were related to stimulus discrimination within the first 200 ms of visual processing. Neglect pathology was specifically associated with significant suppressions of both beta and theta networks engaging right parietal regions. These connectivity abnormalities occurred in a pattern that was distinctly different from what was observed in right-hemisphere lesion patients without neglect. Also, both beta and theta abnormalities contributed additively to visual awareness decrease, quantified in the Behavioural Inattention Test. These results provide evidence for the impairment of fast dynamic fronto-parietal interactions during early stages of visual processing in neglect pathology. Also, they reveal that different modes of fronto-parietal dysfunction contribute independently to deficits in visual awareness at the behavioural level.

Deficient Event-Related Theta Oscillations in Individuals at Risk for Alcoholism: A Study of Reward Processing and Impulsivity Features

BACKGROUND

Individuals at high risk to develop alcoholism often manifest neurocognitive deficits as well as increased impulsivity. Event-related oscillations (EROs) have been used to effectively measure brain (dys)function during cognitive tasks in individuals with alcoholism and related disorders and in those at risk to develop these disorders. The current study examines ERO theta power during reward processing as well as impulsivity in adolescent and young adult subjects at high risk for alcoholism.

METHODS

EROs were recorded during a monetary gambling task (MGT) in 12-25 years old participants (N = 1821; males = 48%) from high risk alcoholic families (HR, N = 1534) and comparison low risk community families (LR, N = 287) from the Collaborative Study on the Genetics of Alcoholism (COGA). Impulsivity scores and prevalence of externalizing diagnoses were also compared between LR and HR groups.

RESULTS

HR offspring showed lower theta power and decreased current source density (CSD) activity than LR offspring during loss and gain conditions. Younger males had higher theta power than younger females in both groups, while the older HR females showed more theta power than older HR males. Younger subjects showed higher theta power than older subjects in each comparison. Differences in topography (i.e., frontalization) between groups were also observed. Further, HR subjects across gender had higher impulsivity scores and increased prevalence of externalizing disorders compared to LR subjects.

CONCLUSIONS

As theta power during reward processing is found to be lower not only in alcoholics, but also in HR subjects, it is proposed that reduced reward-related theta power, in addition to impulsivity and externalizing features, may be related in a predisposition to develop alcoholism and related disorders.

EEG theta and beta power spectra in adolescents with ADHD versus adolescents with ASD + ADHD

Attention problems are common in youngsters with attention deficit hyperactivity disorder (ADHD) as well as in adolescents with combined autism spectrum disorder (ASD) and ADHD. However, it is unknown whether there is psychophysiological overlap and/or a difference in electroencephalogram (EEG) power spectra between ADHD and comorbid ASD and ADHD (ASD + ADHD), on and off stimulant medication. To explore potential differences and overlap, measures of theta and beta power in adolescents diagnosed with ADHD (n = 33) versus adolescents with combined ASD + ADHD (n = 20), categorized by stimulant medication use (57 % of the total sample), were compared. EEG measures were acquired in three conditions: (1) resting state, eyes closed (2) resting state, eyes open and (3) during an oddball task. In addition, performance on the d2 attention test was analyzed. Adolescents with ADHD displayed more absolute theta activity than adolescents with ASD + ADHD during the eyes open and task conditions, independent of stimulant medication use. In addition, only the adolescents with ADHD showed an association between diminished attention test performance and increased theta in the eyes open condition. Results of the current study suggest that although there is behavioral overlap between ADHD characteristics in adolescents with ADHD and adolescents with combined ASD + ADHD, the underlying psychophysiological mechanisms may be different. Adolescents with ASD + ADHD exhibited fewer of the EEG physiological signs usually associated with ADHD, although there was an overlap in attentional problems between the groups. This may indicate that treatments developed for ADHD work differently in some adolescents with ASD + ADHD and adolescents with ADHD only.

Neurofeedback and its possible relevance for the treatment of Tourette syndrome

Neurofeedback is an increasingly recognized therapeutic option in various neuropsychiatric disorders to treat dysfunctions in cognitive control as well as disorder-specific symptoms. In this review we propose that neurofeedback may also reflect a valuable therapeutic option to treat executive control functions in Gilles-de-la-Tourette syndrome (GTS). Deficits in executive control functions when ADHD symptoms appear in GTS likely reflect pathophysiological processes in cortico-thalamic-striatal circuits and may also underlie the motor symptoms in GTS. Such executive control deficits evident in comorbid GTS/ADHD depend on neurophysiological processes well-known to be modifiable by neurofeedback. However, so far efforts to use neurofeedback to treat cognitive dysfunctions are scarce. We outline why neurofeedback should be considered a promising treatment option, what forms of neurofeedback may prove to be most effective and how neurofeedback may be implemented in existing intervention strategies to treat comorbid GTS/ADHD and associated dysfunctions in cognitive control. As cognitive control deficits in GTS mostly appear in comorbid GTS/ADHD, neurofeedback may be most useful in this frequent combination of disorders.

Tourette's syndrome and associated disorders: a systematic review

Objective: To compile data on Tourette's syndrome (TS), tics and associated disorders.Methods: A systematic review of the literature was conducted using the 5S levels of organization of healthcare research evidence (systems, summaries, synopses, syntheses, studies), based on the model described by Haynes. The search keywords were Tourette, tics and comorbidity, which were cross-referenced. Studies provided by publishers and articles being processed on July 31, 2013, were also included.Results: Of all studies retrieved during the search, 64 were selected because they analyzed the epidemiology, clinical features and etiopathogenesis of TS and its comorbidities. TS is classified as a hyperkinetic movement disorder, and at least 90% of the patients have neuropsychiatric comorbidities, of which attention deficit hyperactivity and obsessive-compulsive disorders are the most common. The syndrome is clinically heterogeneous and has been associated with a dysfunction of cortico-striatal-thalamic-cortical circuits involving various neurotransmitters. Although its genetic etiology has been widely studied, other factors may be important to understand this syndrome and its associated disorders.Conclusions: TS is a neurodevelopmental disorder that results from the impact of stress factors on a vulnerable biological substrate during the critical periods of neurodevelopment. The study of TS and its comorbidities may contribute, at different levels, to the understanding of several neuropsychiatric disorders of clinical and therapeutic relevance.

EEG anomalies in adult ADHD subjects performing a working memory task

Functional imaging studies have revealed differential brain activation patterns in attention deficit hyperactivity disorder (ADHD) adult patients performing working memory (WM) tasks. The existence of alterations in WM-related cortical circuits during childhood may precede executive dysfunctions in this disorder in adults. To date, there is no study exploring the electrophysiological activation of WM-related neural networks in ADHD. To address this issue, we carried out an electroencephalographic (EEG) activation study associated with time-frequency (TF) analysis in 15 adults with ADHD and 15 controls performing two visual N-back WM tasks, as well as oddball detection and passive fixation tasks. Frontal transient (phasic) theta event-related synchronization (ERS, 0-500 msec) was significantly reduced in ADHD as compared to control subjects. Such reduction was equally present in a task-independent manner. In contrast, the power of the later sustained (∼500-1200 msec) theta ERS for all tasks was comparable in ADHD and control groups. In active WM tasks, ADHD patients displayed lower alpha event-related desynchronization (ERD, ∼200-900 msec) and higher subsequent alpha ERS (∼900-2400 msec) compared to controls. The time course of alpha ERD/ERS cycle was modified in ADHD patients compared to controls, suggesting that they are able to use late compensatory mechanisms in order to perform this WM task. These findings support the idea of an ADHD-related dysfunction of neural generators sub-serving attention directed to the incoming visual information. ADHD cases may successfully face WM needs depending on the preservation of sustained theta ERS and prolonged increase of alpha ERS at later post-stimulus time points.

Event-related oscillations reflect functional asymmetry in children with attention deficit/hyperactivity disorder

Previous studies have found that event-related theta and gamma oscillations elicited in an auditory selective attention task are deviant in children with attention deficit/hyperactivity disorder (ADHD). It has been suggested that these deviations are associated with deficient motor inhibition in ADHD, which may lead to increased excitability of not only the motor generation networks but also the networks involved in sensory and cognitive processing of the stimulus requiring motor response. Within this suggestion, the present study used the same experimental database to compare the motor cortical activation of healthy controls and children with ADHD during the performance of the auditory selective attention task. Electroencephalography mu (8-12 Hz) activity at C3 and C4 electrodes was used as a measure of motor cortical activation. Mu power was analyzed for four stimulus conditions of the task (attended target, unattended target, attended nontarget, and unattended nontarget). It was found that motor cortical activation as reflected by mu power suppression was not overall greater in ADHD than healthy children. However, stimuli that possessed only partial target features and did not require motor responding (unattended target and attended nontarget) produced a significant reduction of mu activity in ADHD patients. These results suggest that motor cortical excitability is not generally increased in ADHD children. Rather, the co-existence of conflict features in complex stimuli induces task-irrelevant motor activation in these children. The deficient inhibition of motor cortical networks contralateral to the response may therefore be responsible for the functional asymmetry in stimulus processing in ADHD.

Ten years on: a follow-up review of ERP research in attention-deficit/hyperactivity disorder

This article reviews the event-related potential (ERP) literature in relation to attention-deficit/hyperactivity disorder (AD/HD) over the years 2002-2012. ERP studies exploring various aspects of brain functioning in children and adolescents with AD/HD are reviewed, with a focus on group effects and interpretations in the domains of attention, inhibitory control, performance monitoring, non-pharmacological treatments, and ERP/energetics interactions. There has been a distinct shift in research intensity over the past 10 years, with a large increase in ERP studies conducted in the areas of inhibitory control and performance monitoring. Overall, the research has identified a substantial number of ERP correlates of AD/HD. Robust differences from healthy controls have been reported in early orienting, inhibitory control, and error-processing components. These data offer potential to improve our understanding of the specific brain dysfunction(s) which contribute to the disorder. The literature would benefit from a more rigorous approach to clinical group composition and consideration of age effects, as well as increased emphasis on replication and extension studies using exacting participant, task, and analysis parameters.

Smooth pursuit and fixation ability in children with Tourette syndrome

OBJECTIVE

The smooth pursuit eye movements and fixation ability of children aged 8 to 16 years with Tourette syndrome (TS) were examined.

BACKGROUND

Although several studies have examined the saccadic ability of patients with TS, there have been only a few studies examining pursuit ability in TS.

METHOD

Pursuit gain (eye velocity/target velocity) and intrusive saccades during fixation were measured in children with TS-only, TS+attention deficit hyperactivity disorder (ADHD), and TS+ADHD+obsessive compulsive disorder (OCD), and in controls (8 to 16 y). Two pursuit tasks and 1 fixation task were used. In random pursuit 1 (RP1), each step and ramp cycle began from fixation; in random pursuit 2 (RP2), each cycle followed the next. In the fixation task, children were required to maintain fixation on a center dot and ignore distractor stimuli.

RESULTS

All children had significantly higher pursuit gains in RP2 than in RP1 when pursuing a 30 degrees/s moving target. In addition, in RP2, the TS+ADHD+OCD group displayed significantly higher pursuit gains relative to the TS-only, TS+ADHD, and control groups. In the fixation task, the TS+ADHD group exhibited significantly more intrusive saccades than the TS+ADHD+OCD and control groups.

CONCLUSIONS

Our findings support an enhanced oculomotor ability in the TS+ADHD+OCD group and the presence of an online gain control mechanism during ongoing pursuit. These findings are discussed in more detail.

Attentional performance in children and adolescents with tic disorder and co-occurring attention-deficit/hyperactivity disorder: new insights from a 2 × 2 factorial design study

The aim of the present study was to investigate the effect of both tic disorder (TD) and attention-deficit/hyperactivity disorder (ADHD) on attentional functions. N=96 children and adolescents participated in the study, including n=21 subjects with TD, n=23 subjects with ADHD, n=25 subjects with TD+ADHD, and n=27 controls. Attentional performance was tested based on four computerized attention tasks (sustained attention, divided attention, go/nogo and set shifting). The effect of TD as well as ADHD on attentional performance was tested using a 2 × 2 factorial approach. A diagnosis of TD had no negative impact on attentional functions but was associated with improved performance in the set shifting task. By contrast, regardless of a diagnosis of TD, subjects with ADHD were found to perform worse in the sustained attention, divided attention and go/nogo task. No interaction effect between the factors TD and ADHD was revealed for any of the attention measures. Our results add to findings from other areas of research, showing that in subjects with TD and ADHD, ADHD psychopathology is often the main source of impairment, whereas a diagnosis of TD has little or no impact on neuropsychological performance in most cases and even seems to be associated with adaptive mechanisms.

Developmental gender differences in the synchronization of auditory event-related oscillations

OBJECTIVES

The aim of the present study was to explore the neurophysiologic origins of gender differences in auditory processing mechanisms of 7-10 year-old children by means of event-related oscillations. It was tested if the developmental changes in synchronization and magnitude of oscillations in different processing conditions depended on gender.

METHODS

Eighteen girls and 18 boys aged 7-10 years were pair wise matched for age and were divided into two age groups. Auditory event-related potentials (ERPs) were recorded in passive, sensorimotor and working memory conditions. Phase-locking and single-trial magnitude of ERPs were analyzed in the delta (0.5-4 Hz), theta (4-7 Hz), slow (7-10 Hz), and fast (10-14 Hz) alpha frequency bands to test the effects of gender, age, and processing condition.

RESULTS

The phase-locking of auditory delta, theta, and slow alpha oscillations increased with development only in girls, independently of task processing. Only for the theta phase-locking was this effect additionally affected by the motor-related task. No changes in the magnitude of oscillations accompanied these gender differences in synchronization except for parietal delta responses that also increased with development only in girls.

CONCLUSIONS

The results demonstrate that gender differences in auditory ERPs basically originate from a stronger functional synchronization of oscillatory responses generated during stimulus processing.

SIGNIFICANCE

The study provides evidence that the functional maturation of oscillatory auditory networks reflected by a progressive developmental increase of synchronization, is accelerated in girls relative to boys between 7 and 10 years of age.

Comorbidity in the context of neural network properties

Cramer et al.'s network approach reconceptualizes mental comorbidity on the basis of symptom space originating from psychometric signatures. We argue that the advantages of this approach need to be regarded in the context of the multi-level functional organization of the neural substrate, ranging from neurogenetic to psychometric. Neuroelectric oscillations are proposed as a level-integrating principle.

Task-related modulation of anterior theta and posterior alpha EEG reflects top-down preparation

Background

Prestimulus EEG alpha activity in humans has been considered to reflect ongoing top-down preparation for the performance of subsequent tasks. Since theta oscillations may be related to poststimulus top-down processing, we investigated whether prestimulus EEG theta activity also reflects top-down cognitive preparation for a stimulus.

Results

We recorded EEG data from 15 healthy controls performing a color and shape discrimination task, and used the wavelet transformation to investigate the time course and power of oscillatory activity in the signals. We observed a relationship between both anterior theta and posterior alpha power in the prestimulus period and the type of subsequent task.

Conclusions

Since task-differences were reflected in both theta and alpha activities prior to stimulus onset, both prestimulus theta (particularly around the anterior region) and prestimulus alpha (particularly around the posterior region) activities may reflect prestimulus top-down preparation for the performance of subsequent tasks.

Electrophysiological indices of abnormal error-processing in adolescents with attention deficit hyperactivity disorder (ADHD)

BACKGROUND

Impaired cognitive control has been frequently observed in children and young people with attention deficit hyperactivity disorder (ADHD) and might underlie the excessive hyperactivity and impulsivity in this population. We investigated behavioural and electrophysiological indices relevant to one domain of cognitive control; namely error processing.

METHODS

Adolescents aged 14 to 17 with ADHD (n = 23) and a typically developing control group (HC; n = 19) performed a visual go/no-go task. Electro-encephalography (EEG) data were collected simultaneously and response-locked error trials were averaged to derive two event-related potentials, the error-related negativity (ERN) and error positivity (Pe). Evoked theta power and inter-trial phase coherence (ITC) were measured in two time windows ('early' and 'late') equivalent to those used for detection of the ERN and Pe.

RESULTS

Analysis revealed normal ERN amplitude and a statistical trend for smaller Pe amplitude at a fronto-central electrode site in the ADHD group. The group also showed significant reductions in late evoked theta power and early and late theta ITC. Relationships between behavioural measures and ITC were different between groups, particularly for post-error slowing, a measure of strategic response adjustment on trials immediately following an error.

CONCLUSIONS

The results reveal abnormalities in behavioural and electrophysiological indices of error processing in adolescents with ADHD and suggest that ITC is more sensitive than traditional ERP measures to error-processing abnormalities.

Event-Related Brain Oscillations

Neuroelectric oscillations provide important tools to study information processing in the brain. In this paper, major concepts and advantages of event-related oscillations (EROs) are considered, with a focus on their relevance for developmental research. Findings from previous studies in passive and oddball conditions are summarized to demonstrate that the age-dependent power decrease of theta (4–7 Hz) and alpha (8–14 Hz) EROs is accompanied by an increase in the synchronization of these oscillations. New data are presented to test whether this dissociation depends on processing demands in a frequency-specific manner. Results from an auditory serial learning task with working memory activation performed by 70 subjects (children from 6 to 10 years of age and adults) indicate that this effect was observed for theta and slow alpha oscillations, whereas an age-dependent decrease in event-related phase synchronization was found for fast alpha oscillations. It is concluded that phase synchronization of only the major theta and alpha EROs may reflect the neurobiological maturation of neural networks involved in perception. Phase synchronization of EROs, however, especially from faster frequency bands, essentially depends on the mode of network involvement and functional competence, which is associated with cognitive processing abilities or strategies in the course of development.

Brain oscillations forever--neurophysiology in future research of child psychiatric problems

For decades neurophysiology has successfully contributed to research and clinical care in child psychiatry. Recently, methodological progress has led to a revival of interest in brain oscillations (i.e., a band of periodic neuronal frequencies with a wave-duration from milliseconds to several seconds which may code and decode information). These oscillations will nurture future information processing research during normal and pathological brain development, allowing us to investigate basic neuronal connectivity as well as interactions of brain systems and their modulation (e.g., by temporal neuronal synchronisation) as close correlates of behaviour and intermediate phenotypes from genes to behavioural variations. Especially, a systematic neurodynamic look at transitional processes from rest to stimulus-triggered goal-directed performance will aid behavioural understanding and guidance of children. Preliminary data suggest two separate oscillatory mechanisms in this respect. One is ongoing from pre- to post-stimulus processing and related to quantitative modification of behaviour, while another is merely related to qualitative effects of behaviour and reflects 'on-top' post-stimulus processing by temporal neuronal synchronisation of the oscillatory network in question. Suggested neurodynamic models may be tested in multilevel clinical experiments as well as in the framework of computational neuropsychiatry.

Event-Related Oscillations and Cognitive Processes in Children

Event-related EEG modulations, which are phase-locked to perceptual, cognitive, and motor processes, are often studied by means of event-related potentials (ERPs), although event-related oscillatory responses in different EEG frequency bands allow a more refined analysis, closer to brain physiology. This article introduces the basics of time-frequency methods, which are typically applied for the analysis of event-related oscillations, focusing on adaptive procedures (e.g., wavelet networks). The potential of these methods is illustrated. Findings about event-related oscillations (gamma responses, theta responses) in children performing an auditory selective attention task are reviewed. Both the neuronal substrates of gamma (30–70 Hz) networks and the ability to synchronize these networks in relation to task-specific processes are available in children and adolescents from 9 to 16 years of age. Developmental changes in the task reactivity of synchronized gamma oscillations may provide evidence for a transition in cognitive processing strategies emerging at the age of 12–13 years. Event-related theta (3–7.5 Hz) activity is enhanced in two latency ranges. The early event-related theta response occurring 0–200 ms after a stimulus may be associated with representations of relevant target features in working memory. The late fronto-central theta response (200 – 450 ms) could be related to the processing of task-irrelevant information. In summary, event-related oscillations can be analyzed using time-frequency methods like wavelet networks. This approach should be used intensively to study neurocognitive development in children.

Gender-specific development of auditory information processing in children: an ERP study

OBJECTIVES

The aim of the present study was to evaluate the effects of gender on sensory and cognitive information processing in children by analyzing auditory event-related potentials (ERPs). The major questions were: (1) do ERPs differ between girls and boys aged 7-10years, (2) do gender differences in ERPs depend on the development with age, on task-processing demands, and on the development of neuroelectric networks as reflected by the spontaneous EEG?

METHODS

Thirty-six healthy children (18 girls and 18 boys) were divided in two age groups (7- to 8- and 9- to 10-year-old). Boys and girls were pairwise matched for age. Auditory ERPs were analyzed in a passive listening condition (PLC), a simple reaction task (SRT) and a serial learning reaction task (SLRT), in which memory and sensorimotor processes were varied in a balanced way. Cognitive performance, reaction times (RTs), and the spontaneous electroencephalogram (EEG) were also measured.

RESULTS

Cognitive performance improved earlier in girls than boys, whereas response speed was not affected by gender. Independent of processing demands, ERP components within 300ms after stimulation (N1, P2, N2 and P3) increased with development only in the group of girls. For later components, the developmental speeding of the parietal P3b component to task-relevant stimuli also tended to be more expressed in girls than boys, whereas a late frontal negative wave N400-700 was shorter in the girls than boys from the two age groups. Likewise, independently of age, the spontaneous EEG manifested a larger theta activity in girls than boys.

CONCLUSIONS

Developmental changes of basic auditory processing mechanisms strongly depend on gender in children between 7 and 10years by being faster in girls. This gender-specific development of early ERP components is not modulated by processing demands, cannot be attributed to a faster cognitive maturation of girls, nor can it be explained with the gender-specific maturation of background neuroelectric networks. Rather, it reflects an accelerated functional activation of auditory processing networks in girls. Interestingly, the cognitive development was also faster in girls, but it occurred earlier than the functional activation of auditory processing networks.

SIGNIFICANCE

This study provides evidence for accelerated neuroelectric (as reflected by spontaneous EEG), neurofunctional (as reflected by auditory ERPs), and neurocognitive (as reflected by learning performance) development in 7- to 10-year-old girls than boys.

A subgroup of Tourette's patients overexpress specific natural killer cell genes in blood: a preliminary report

Gilles de la Tourette Syndrome (TS) is a heritable, neurodevelopmental disorder characterized by motor and vocal tics. As no single gene or region has emerged from standard linkage approaches, TS may result from several as-yet-unidentified genetic factors, and may also occur due to infection-triggered, autoimmune processes. Etiological or pathogenic differences might result in clinically indistinguishable TS subgroups. We have previously used whole genome human oligonucleotide microarrays in an attempt to identify patterns of gene expression in blood linked with TS. In this proof-of-principle study, we applied Principal Components Analysis to a previously collected set of 16 familial TS and 16 control blood samples to identify subgroups. Fourteen genes, primarily Natural Killer Cell (NK) genes, discriminated between TS and all controls. Granzyme B and NKG7 were confirmed using RT-PCR. Five probesets (four genes) reside in chromosomal regions previously linked to familial TS or obsessive-compulsive disorder. Using the 14 genes, a Principal Components Analysis as well as a cluster analysis identified a TS subgroup (n = 10/16) that overexpressed the NK genes. 7/10 subjects within this subgroup were diagnosed with attention-deficit hyperactivity disorder (ADHD), suggesting that this expression profile might be associated with TS and co-morbid ADHD. Principal Components Analysis of gene expression in blood may be useful for identifying subgroups of other complex neurodevelopmental diseases, and the gene expression profile identified in this study may provide a biomarker for at least one subgroup of heritable TS.

Attentional functions in children and adolescents with attention-deficit/hyperactivity disorder with and without comorbid tic disorder

Although the coexistence of attention-deficit/hyperactivity disorder (ADHD) and tic disorder (TD) is common, the nature of association is yet not fully understood. Thus, the aim of the present study was to explore attentional dysfunction in children with pure ADHD compared to children with comorbid ADHD + TD. Three groups of 20 children each, aged 8-15 years with either ADHD, ADHD + chronic tic disorder or Tourette syndrome (ADHD + TD) and a healthy control group were compared in their performance on three computerized attention tasks. Tasks of sustained attention, selective attention and interference control were employed. In addition, parental ratings of ADHD symptom severity and behaviour problems were obtained. Both clinical groups were rated as equally inattentive, however, externalising symptoms were more severe in the ADHD group. Objective measures of attentional performance revealed differences between the groups: whereas the ADHD group was markedly impaired in sustaining attention and selective attention/inhibitory control, the ADHD + TD group only showed marginal deficits in selective attention/inhibitory control. Possible explanations for the superior performance of the comorbid group are discussed: In particular, the results may indicate that in some patients, the tic disorder produces behavioural symptoms of ADHD, but not the broad neurocognitive deficits that usually are associated with ADHD. Alternatively, compensatory neural mechanisms of TD patients may result in a better neuropsychological performance of comorbid patients relative to patients suffering from pure ADHD.

Decision-making on an explicit risk-taking task in preadolescents with attention-deficit/hyperactivity disorder

Inappropriate risk-taking and disadvantageous decision-making have been described as major behavioural characteristics of patients with attention-deficit/hyperactivity disorder (ADHD). However these behaviours are difficult to measure in laboratory contexts and recent studies have yielded inconsistent results which might be related to task characteristics. The present study adopted the Game of Dice Task, a test procedure in which risks are made explicit and the load on working memory is minimal. As a result, preadolescents with ADHD (N = 23) made significantly more risky choices and suffered major losses of money compared to normal controls (N = 24) but only when they played the game a second time. Differences in risk-taking correlated significantly with hyperactivity as rated by parents and with inhibitory control, but not with working memory performance. The results are discussed in the context of current theories of ADHD.

Disentangling the effects of Tourette syndrome and attention deficit hyperactivity disorder on cognitive and behavioral phenotypes

Eighty participants (62 males; 18 females; age range: 6-16 years) took part in the study, comprising four groups of 20 subjects each: TS-only, ADHD-only, TS+ADHD, controls. The age distributions, did not differ significantly among the four groups. The severity of symptoms, assessed by the TSGS, did not differ significantly between the two TS groups. Standardised measures were used throughout. The "cases" (i.e. TS-only, TS+ADHD, ADHD-only) were significantly different from controls on most measures of behavior. There were also differences amongst the various clinical subgroups, with, in general, TS-only participants being similar to controls with regards to both "total behavior" ratings and cognitive testing results. A diagnosis of ADHD, either or its own or in association with TS, was associated with greater maladaptive behavior and worse cognitive functioning. With regards to affective symptoms and anxiety, the three clinical groups did not differ from each other, but each of them was more affected than the control group. One finding in our study which differed from previous literature was that TS-only patients were rated as more "delinquent" than controls by their parents: possible reasons for this are discussed. Oppositional defiant disorder (ODD) was seen in a few (2,3,3 ODD patients in each clinical group), but as numbers were small no statistics were undertaken. Family histories were in accord with both TS and ADHD being genetic disorders, but sharing an overlap in only some cases. The "additive effect" hypothesis is discussed in detail in the light of our results and recent literature.

Comorbidity of tic disorders & ADHD: conceptual and methodological considerations

BACKGROUND

The causes and pathophysiological mechanisms of the common comorbidity of tic disorders and Attention-deficit/Hyperactivity disorder (TD + ADHD; about 50% of TD, about 20% of ADHD) still remain unclear. Studies with a 2 x 2 design comparing groups of children with TD, ADHD, TD + ADHD and healthy controls are in need and may disentangle the influences of TD versus ADHD in the case of comorbidity. Unfortunately, conceptual and methodological problems can restrain possible conclusions from these studies.

METHOD

A review of the literature on artifactual and non-artifactual models of comorbidity in general and specially for TD + ADHD was conducted.

RESULTS

The first section describes various possible models of comorbidity and their corresponding hypotheses concerning expected patterns of findings comparing groups of children with TD, ADHD, TD + ADHD and healthy controls. In the second part research results concerning psychopathological, neuropsychological, neurophysiological, structural and functional imaging, as well as genetic characteristics are summarized. In the third section possible conclusions and their limitations due to conceptual and methodological problems possibly contributing to the ambiguous results are discussed. Finally, future research strategies and the need for full causal models are outlined.

CONCLUSION

Some components of the etiological pathways of TD + ADHD may well be shared with the 'pure' conditions while others may be unique.

The role of abnormal neural oscillations in the pathophysiology of co-occurring Tourette syndrome and attention-deficit/hyperactivity disorder

OBJECTIVE

To examine the role of aberrant neural oscillatory activity in the pathophysiology of co-occurring Tourette Syndrome (TS) and Attention-Deficit/Hyperactivity Disorder (ADHD).

METHOD

Neural oscillations refer to periodic variations in the recording of neural activity. The temporal synchronization of oscillations represents a mechanism of neural communication implicated in normal brain functioning as well as psychopathology. We reviewed physiological, imaging, and neuropsychological evidence that tics and symptoms of ADHD may result from abnormal oscillatory activity in the brain.

RESULTS

Structural and functional abnormalities in the cortical-striatal-thalamo-cortical circuits may result in the disruption of oscillatory activity within the basal ganglia of individuals with TS and lead to transient hyperpolarization of selected thalamocortical regions. Extended to TS plus ADHD this or similar mechanisms, in turn, would lead to the dysrhythmia of particular vulnerable cortical regions and give rise to various deficits in motor control (TS + ADHD) as well as impulsivity and attention (ADHD). Compensatory systems within the prefrontal cortex could be activated and trained to modulate the misguided striatal and thalamocortical oscillations.

CONCLUSIONS

Although it is highly likely that abnormal neural oscillations have a prominent role in co-occurrence of TS + ADHD, its final relevance in this case deserves further differentiated research (i.e. oscillatory networks disentangled from other neuropsychiatric disorders).

Sleep patterns in children with attention-deficit/hyperactivity disorder, tic disorder, and comorbidity

BACKGROUND

In children, attention-deficit/hyperactivity disorder (ADHD), tic disorder (TD), and their coexistence (ADHD + TD comorbidity) are very common and clinically important. Associated sleep patterns and their clinical role are still insufficiently investigated. This study aimed at characterizing these sleep patterns in children with ADHD, TD, and ADHD + TD comorbidity and determining whether, in ADHD + TD, the factors ADHD and TD may affect the sleep pattern in an independent (additive) or in a complex (interactive) manner.

METHOD

By means of polysomnography, sleep patterns were investigated in 4 groups of unmedicated 8.0-16.4-year-old children (healthy controls, ADHD-only, TD-only, and ADHD + TD). Each group consisted of 18 subjects matched for age, gender, and intelligence.

RESULTS

ADHD was primarily characterized by increase in rapid eye movement (REM) sleep, whereas TD patients displayed lower sleep efficiency and elevated arousal index in sleep. In children with ADHD + TD, both effects appeared. No interaction between the ADHD and TD factors was found for any of the sleep parameters. Significant correlations between sleep patterns and clinical symptoms were found.

CONCLUSIONS

ADHD and TD are characterized by specific sleep alterations. When coexisting, the two disorders alter the sleep pattern in an additive manner, suggesting a high impact on clinical and therapeutic perspectives.

Co-existence of tic disorders and attention-deficit/hyperactivity disorder-recent advances in understanding and treatment

In daily clinical practice of child psychiatry tic disorders (TD) and attention-deficit/hyperactivity disorder (ADHD) as well as their co-existence are common and need careful evidence-based approaches in differential diagnostics and treatment choice. Hence, their relationship at different levels (e.g., psychopathology, neuropsychology, neurobiology, treatment) needs to be elucidated in more detail. The articles of this supplement deal with this subject. It is unclear if TD + ADHD represents an own clinical entity and which component (TD vs. ADHD) is most important in case of co-existence with respect to accompanying problems like emotional or cognitive disturbances. This editorial gives a short overview of the essential research topics concerning TD + ADHD and shows where (in this ECAP supplement and other literature) empirically based answers can be found. Probably, the identification of separate or common "endophenotypes" for TD-only, ADHD-only and for TD + ADHD would help to sort out the complexities and this supplement may nurture such a perspective of future research for a better understanding and treatment of youths with TD + ADHD and their families.

Behavior therapy in tic-disorders with co-existing ADHD

OBJECTIVES

To give an overview concerning the behavioral treatment approaches for Chronic Tic Disorder (CTD) and Attention-Deficit/Hyperactivity Disorder (ADHD) and to provide some suggestions for the behavioral treatment of children and adolescents with a combination of both disorders.

RESULTS

Pharmacotherapy plays an important role in the treatment of both ADHD and CTD. However, behavior therapy has also been proven to ameliorate the core symptoms of both disorders. The most prominent behavioral technique to reduce tics is habit reversal training. In ADHD behavioral interventions, especially parent training and behavioral interventions in preschool/school, are effective in reducing ADHD core symptoms and comorbid problems. In children and adolescents with ADHD plus CTD both ADHD and tic symptoms can be treated by behavioral interventions alone or in combination with pharmacotherapy. However, most of the published studies on behavioral interventions in children with ADHD or CTD do not give detailed information on comorbidity and many studies excluded patients with comorbid problems.

CONCLUSIONS

Clinical experience suggests that in CTD+ADHD success may be easier to achieve using behavioral treatment of ADHD first. Adherence to the habit reversal procedure to reduce tics in daily living is the most important problem in the behavioral treatment of tics especially in children with comorbid ADHD. Practical suggestions to overcome these difficulties are presented.

Executive functions in children with chronic tic disorders with/without ADHD: new insights

OBJECTIVE

In Chronic Tic Disorders (CTD) associated Attention Deficit Hyperactivity Disorder (ADHD) is very common. Hence, it is important to clarify how both conditions are related to cognitive dysfunctions in patients with CTD+ADHD comorbidity. Recent studies on neuropsychology revealed equivocal results, mostly due to methodological shortcomings like problems in sample composition. Thus better and more detailed information on this topic is needed to improve diagnostic and treatment approaches.

METHOD

Three tasks related to different domains of executive functions (the Matching Familiar Figures Test, the Stroop color-word interference task, and a computerized version of the Wisconsin Card Sorting Test) have been performed in two independent samples (altogether n = 138 children) both including four groups of children (CTD-only, CTD+ADHD, ADHD-only, healthy controls) matched for age and IQ. To specify the influence of either tics or ADHD-symptoms on executive functions and to answer the question of their interactive or additive relationship two-way analyses of variance (MANOVA) for the factors CTD (yes,-no) x ADHD (yes,no) were conducted. Eta squared was calculated to reveal the effect sizes for each factor. For a deeper understanding of group differences and to better enable the comparison with data in literature, additional analyses of variance (ANOVA) with posthoc testing were applied.

RESULTS

In summary, there was a main effect only for the factor ADHD reflected by decreased performance, while no main effect of the factor CTD could be found. Admittedly, the effects were not uniform in both samples. However, in all three tasks and both samples, uniformly no interaction between the main factors has been observed.

CONCLUSIONS

In cases of coexisting CTD+ADHD the factor ADHD shows the main negative impact on neuropsychological performance and this impact seems to be independent of any feature of the coexisting tics (additive model). This supports the notion to primarily treat the ADHD-symptoms in order to increase cognitive self regulatory abilities of these children. Contrarily, tics seem to have little impact on cognitive performance in most cases.

Psychopathological profile in children with chronic tic disorder and co-existing ADHD: additive effects

The nature of the co-occurrence of chronic tic disorders (CTD) and attention deficit hyperactivity disorder (ADHD) is unclear. Especially in the field of psychopathology, the relationship of CTD and ADHD remains to be clarified. Thus, the aim of the present chart review study was to specify the contribution of CTD and/or ADHD to the psychopathological profile of the comorbid group (CTD+ADHD). The psychopathological profiles of four large groups (CTD-only (n=112), CTD+ADHD (n=82), ADHD-only (n=129), controls (n=144)) were measured by the eight subscales of the Child Behavior Checklist (CBCL) and analyzed by a 2x2 factorial design followed by contrasts. There were main effects of ADHD diagnosis on all but one subscale of the CBCL (Somatic Complaints). For CTD diagnosis, main effects were found for Attention Problems, Anxious/Depressed, Thought Problems, Social Problems and Somatic Complaints. The only interaction effect was seen for Somatic Complaints. While CTD and ADHD were both related to internalizing psychopathology of children in the CTD+ADHD group, ADHD had the largest effect on externalizing psychopathology in the comorbid group. At the level of psychopathology, an additive model for the co-occurrence of CTD and ADHD is strongly supported. In the comorbid group (CTD+ADHD), the ADHD diagnosis shows the strongest relation to externalizing psychopathology.