Executive function in children with Tourette syndrome and/or attention deficit hyperactivity disorder

Comorbidities and Disease Duration in Tourette Syndrome: Impact on Cognition and Quality of Life of Children

BACKGROUND

Cognitive functions represent foundational factors for mental health and quality of life (QoL). In Tourette syndrome (TS), psychiatric comorbidities are common and have been inconsistently reported to affect the cognition and QoL of patients, while the role of tic disorder duration has not been yet explored.

METHODS

To examine how comorbidities and TS duration may influence cognition and QoL, N = 80 children with TS (6-16 years) were evaluated using the Wechsler Intelligence Scale for Children (WISC-IV). Standardized questionnaires were used to assess the presence and severity of TS main comorbidities and QoL. Data were interpreted using linear correlations, regression, and mediation analysis.

RESULTS

Depression and attention-deficit/hyperactivity disorder (ADHD) symptoms accounted for poorer cognitive performance. Anxiety oppositely predicted better cognitive performance, while no significant role for obsessive compulsive disorder (OCD) was observed. Disease duration was associated with lower total IQ, verbal reasoning, and working memory abilities. Depression, anxiety, and TS duration also deeply influenced QoL measures.

CONCLUSIONS

TS common comorbidities have a differential impact on the cognitive abilities of children and adolescents, which translates into a complex influence on their perceived QoL. A longer clinical history of tics was related to worse cognitive outcomes, which prompts further consideration of disease duration in both clinical and research settings involving children and adolescents.

Fine Motor Skills in Children with Tourette Syndrome and their Unaffected First-degree Siblings

Background

The exact etiology of Tourette Syndrome (TS) remains unclear, making the search for impaired neuropsychological functions possibly connected to the underlying cause of TS as important as it is challenging. One neuropsychological domain of interest is fine motor skills.

Method

This study compared fine motor skill performance on the Purdue Pegboard Task (PPT) in 18 children with TS, 24 unaffected first-degree siblings and 20 controls. A set of screening questionnaires was administered to determine comorbid psychiatric illness.

Results

Children with TS, their siblings and controls did not differ significantly in fine motor skills as measured with the PPT. Performance on the PPT was not correlated with tic severity; however, we found an inverse correlation with severity of attention-deficit/hyperactivity disorder (ADHD) symptoms, as assessed by parent reported ADHD symptoms. Children with TS were found to have significantly higher parent reported ADHD symptoms compared to controls, yet only two out of the 18 participants had been diagnosed with ADHD.

Conclusion

This study suggests that fine motor skill impairment in children with TS may be more strongly correlated with comorbid ADHD than to TS and tics.

Association of resting-state theta–gamma coupling with selective visual attention in children with tic disorders

A tic disorder (TD) is a neurodevelopmental disorder characterized by tics, which are repetitive movements and/or vocalizations that occur due to aberrant sensory gating. Its pathophysiology involves dysfunction in multiple parts of the cortico-striato-thalamo-cortical circuits. Spontaneous brain activity during the resting state can be used to evaluate the baseline brain state, and it is associated with various aspects of behavior and cognitive processes. Theta–gamma coupling (TGC) is an emerging technique for examining how neural networks process information through interactions. However, the resting-state TGC of patients with TD and its correlation with cognitive function have not yet been studied. We investigated the resting-state TGC of 13 patients with TD and compared it with that of 13 age-matched healthy children. The participants underwent resting-state electroencephalography with their eyes closed. At the global level, patients with TD showed a significantly lower resting-state TGC than healthy children. Resting-state TGC with the eyes closed was significantly negatively correlated with the attention quotient calculated for omission errors in a selective visual attention test. These findings indicate that the resting-state brain network, which is important for the attentional processing of visual information, is dysfunctional in patients with TD. Additionally, these findings support the view that TGC reflects information processing and signal interactions at the global level. Patients with TD may have difficulty gating irrelevant sensory information in the resting state while their eyes are closed.

Stimulant Induced Movement Disorders in Attention Deficit Hyperactivity Disorder

Stimulants, such as amphetamine and methylphenidate, are one of the most effective treatment modalities for attention deficit hyperactivity disorder (ADHD) and may cause various movement disorders. This review discusses various movement disorders related to stimulant use in the treatment of ADHD. We reviewed the current knowledge on various movement disorders that may be related to the therapeutic use of stimulants in patients with ADHD. Recent findings suggest that the use of stimulants and the onset/aggravation of tics are more likely to be coincidental. In rare cases, stimulants may cause stereotypies, chorea, and dyskinesia, in addition to tics. Some epidemiological studies have suggested that stimulants used for the treatment of ADHD may cause Parkinson’s disease (PD) after adulthood. However, there is still a lack of evidence that the use of stimulants in patients with ADHD may cause PD, and related studies are only in the early stages. As stimulants are one of the most commonly used medications in children and adolescents, close observations and studies are necessary to assess the effects of stimulants on various movement disorders, including tic disorders and Parkinson’s disease.

Sustained attention induces altered effective connectivity of the ascending thalamo-cortical relay in obsessive-compulsive disorder

Abnormal function of the thalamo-cortical relay is considered a hallmark of obsessive-compulsive disorder (OCD) and aberrant network interactions may underpin many of the clinical and cognitive symptoms that characterize the disorder. Several statistical approaches have been applied to in vivo fMRI data to support the general loss of thalamo-cortical connectivity in OCD. However, (a) few studies have assessed the contextual constraints under which abnormal network interactions arise or (b) have used methods of effective connectivity to understand abnormal network interactions. Effective connectivity is a particularly valuable method as it describes the putative causal influences that brain regions exert over each other, as opposed to the largely statistical consistencies captured in functional connectivity techniques. Here, using dynamic causal modeling (DCM), we evaluated how attention demand induced inter-group differences (HC ≠ OCD) in effective connectivity within a motivated thalamo-cortical network. Of interest was whether these effects were observed on the ascending thalamo-cortical relay, essential for the sensory innervation of the cortex. fMRI time series data from sixty-two participants (OCD, 30; HC, 32) collected using an established sustained attention task were submitted to a space of 162 competing models. Across the space, models distinguished between competing hypotheses of thalamo-cortical interactions. Bayesian model selection (BMS) identified marginally differing likely generative model architectures in OCD and HC groups. Bayesian model averaging (BMA), was used to weight connectivity parameter estimates across all models, with each parameter weighted by each model's posterior probability, thus providing more stable estimates of effective connectivity. Inferential statistical analyses of estimated parameters revealed two principal results: (1) Significantly reduced intrinsic connectivity of the V1 → SPC pathway in OCD, suggested connective weakness in the early constituents of the dorsal visual pathway; (2) More pertinent with the discovery possibilities afforded by DCM, sustained attention in OCD patients induced significantly reduced contextual modulation of the ascending relay from the thalamus to the prefrontal cortex. These results form an important complement to our understanding of the contextual bases of thalamo-cortical network deficits in OCD, emphasizing vulnerability of the ascending relay.

Impairment of visually guided associative learning in children with Tourette syndrome

The major symptoms of Tourette syndrome are motor and vocal tics, but Tourette syndrome is occasionally associated with cognitive alterations as well. Although Tourette syndrome does not affect the majority of cognitive functions, some of them improve. There is scarce evidence on the impairment of learning functions in patients with Tourette syndrome. The core symptoms of Tourette syndrome are related to dysfunction of the basal ganglia and the frontostriatal loops. Acquired equivalence learning is a kind of associative learning that is related to the basal ganglia and the hippocampi. The modified Rutgers Acquired Equivalence Test was used in the present study to observe the associative learning function of patients with Tourette syndrome. The cognitive learning task can be divided into two main phases: the acquisition and test phases. The latter is further divided into two parts: retrieval and generalization. The acquisition phase of the associative learning test, which mainly depends on the function of the basal ganglia, was affected in the entire patient group, which included patients with Tourette syndrome with attention deficit hyperactivity disorder, obsessive compulsive disorder, autism spectrum disorder, or no comorbidities. Patients with Tourette syndrome performed worse in building associations. However, the retrieval and generalization parts of the test phase, which primarily depend on the function of the hippocampus, were not worsened by Tourette syndrome.

Assessment of changes in the macula and optic nerve head using optical coherence tomography in patients with attention deficit hyperactivity disorder

INTRODUCTION

To assess if there are any differences in macular and papillary thickness using optical coherence tomography (OCT) in patients with attention deficit hyperactivity disorder (ADHD) compared with a control group, including if there are differences between ADHD patients with and without treatment.

METHODS

Prospective observational study including 92 eyes of 46 patients divided into 2 groups: 46 eyes of 23 patients with ADHD, and a control group of 46 eyes of 23 healthy patients. The group of patients with ADHD was subdivided into those on treatment with methylphenidate (n=28) and those not on treatment (n=18). The macular thickness, the ganglion cell complex (GCC), and the retinal nerve fibre layer (RNFL) at the papillary level were measured in 12 sectors.

RESULTS

A lower central macular thickness was observed in the ADHD patients than in the controls (257.4±20μm versus 267.5±20μm, P=.013), with no differences observed in the GCC (P=.566), or in the RNFL (P=.095). There were no differences in the patients with ADHD with and without treatment, as regards macular thickness and the GCC (P=.160 and P=.375 respectively), but a lower foveal thickness (P=.018) and RNFL in 5/12 sectors at the papillary level (P=.033) were observed in those without treatment.

CONCLUSIONS

A lower macular thickness was observed in patients with ADHD than in controls. In addition, patients with ADHD without treatment had a lower thickness of the fovea and RNFL than those patients on treatment.

The Pathophysiology of Tics; An Evolving Story

Background:

Tics, defined as quick, rapid, sudden, recurrent, non-rhythmic motor movements or vocalizations are required components of Tourette Syndrome (TS) - a complex disorder characterized by the presence of fluctuating, chronic motor and vocal tics, and the presence of co-existing neuropsychological problems. Despite many advances, the underlying pathophysiology of tics/TS remains unknown.

Objective:

To address a variety of controversies surrounding the pathophysiology of TS. More specifically: 1) the configuration of circuits likely involved; 2) the role of inhibitory influences on motor control; 3) the classification of tics as either goal-directed or habitual behaviors; 4) the potential anatomical site of origin, e.g. cortex, striatum, thalamus, cerebellum, or other(s); and 5) the role of specific neurotransmitters (dopamine, glutamate, GABA, and others) as possible mechanisms (Abstract figure).

Methods:

Existing evidence from current clinical, basic science, and animal model studies are reviewed to provide: 1) an expanded understanding of individual components and the complex integration of the Cortico-Basal Ganglia-Thalamo-Cortical (CBGTC) circuit - the pathway involved with motor control; and 2) scientific data directly addressing each of the aforementioned controversies regarding pathways, inhibition, classification, anatomy, and neurotransmitters.

Conclusion:

Until a definitive pathophysiological mechanism is identified, one functional approach is to consider that a disruption anywhere within CBGTC circuitry, or a brain region inputting to the motor circuit, can lead to an aberrant message arriving at the primary motor cortex and enabling a tic. Pharmacologic modulation may be therapeutically beneficial, even though it might not be directed toward the primary abnormality.

Executive function in children with Tourette syndrome and attention-deficit/hyperactivity disorder: Cross-disorder or unique impairments?

Findings of executive functioning deficits in Tourette syndrome (TS) have so far been inconsistent, possibly due to methodological challenges of previous studies, such as the use of small sample sizes and not accounting for comorbid attention-deficit/hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), or medication use. We aimed to address these issues by examining several areas of executive functioning (response inhibition, attentional flexibility, cognitive control, and working memory) and psychomotor speed in 174 8-to-12-year-old children with TS [n = 34 without (TS-ADHD) and n = 26 with comorbid ADHD (TS+ADHD)], ADHD without tics (ADHD-TS; n = 54), and healthy controls (n = 60). We compared executive functioning measures and psychomotor speed between these groups and related these to ADHD severity across the whole sample, and tic severity across the TS groups. Children with TS+ADHD, but not TS-ADHD, made more errors on the cognitive control task than healthy children, while TS-ADHD had a slower psychomotor speed compared to healthy controls. The ADHD group showed impairment in cognitive control and working memory versus healthy controls. Moreover, higher ADHD severity was associated with poorer cognitive control and working memory across all groups; there was no relation between any of the executive functioning measures and tic severity. OCD severity or medication use did not influence our results. In conclusion, we found little evidence for executive function impairments inherent to TS. Executive function problems appear to manifest predominantly in relation to ADHD symptomatology, with both cross-disorder and unique features of neuropsychological functioning when cross-comparing TS and ADHD.

Merging the Pathophysiology and Pharmacotherapy of Tics

Background

Anatomically, cortical-basal ganglia-thalamo-cortical (CBGTC) circuits have an essential role in the expression of tics. At the biochemical level, the proper conveyance of messages through these circuits requires several functionally integrated neurotransmitter systems. In this manuscript, evidence supporting proposed pathophysiological abnormalities, both anatomical and chemical is reviewed. In addition, the results of standard and emerging tic-suppressing therapies affecting nine separate neurotransmitter systems are discussed. The goal of this review is to integrate our current understanding of the pathophysiology of Tourette syndrome (TS) with present and proposed pharmacotherapies for tic suppression.

Methods

For this manuscript, literature searches were conducted for both current basic science and clinical information in PubMed, Google-Scholar, and other scholarly journals to September 2018.

Results

The precise primary site of abnormality for tics remains undetermined. Although many pathophysiologic hypotheses favor a specific abnormality of the cortex, striatum, or globus pallidus, others recognize essential influences from regions such as the thalamus, cerebellum, brainstem, and ventral striatum. Some prefer an alteration within direct and indirect pathways, whereas others believe this fails to recognize the multiple interactions within and between CBGTC circuits. Although research and clinical evidence supports involvement of the dopaminergic system, additional data emphasizes the potential roles for several other neurotransmitter systems.

Discussion

A greater understanding of the primary neurochemical defect in TS would be extremely valuable for the development of new tic-suppressing therapies. Nevertheless, recognizing the varied and complex interactions that exist in a multi-neurotransmitter system, successful therapy may not require direct targeting of the primary abnormality.

Videos look faster as children grow up: Sense of speed and impulsivity throughout primary school

Previous research has documented systematic biases when adult observers judge the original speed of real-life video clips. What does the unfolding of events in videos-an increasingly pervasive "substitute reality"-look like as children grow up? The current study investigated the sense of speed during childhood and the relation with a number of performance and personality indexes. A group of 142 children aged 6-10 years adjusted the speed of video clips representing various scenes until reaching the apparent right speed. We found a tendency to underestimate speed; on average, videos played at their original speed were considered to be too slow. This tendency was larger in younger children and decreased with age (-3.16%/year). Uncertainty in judging video speed also decreased over the same age period (-10.79%/year). Children then performed a simple visuomotor task requiring response control, which revealed high accuracy and, in older children, faster responses. Children were also assessed for impulsivity/inattention and visuomotor habits through parents' questionnaires. When all variables were considered together, age and video game playing stood out as the only significant predictors of speed biases, both associated with an increase in apparent video speed. Thus, this study provides evidence of a change in the sense of speed during the primary school period, possibly involving the progressive overriding of a slow motion prior and/or the protracted calibration of perceptual mechanisms for speed constancy. The sense of speed, however, did not seem to be influenced by impulsivity traits in the population considered.

A Review of the Neuropsychological Dimensions of Tourette Syndrome

Neurocognitive functioning in Tourette syndrome (TS) has been the subject of intensive research in the past 30 years. A variety of impairments, presumably related to frontal and frontostriatal dysfunctions, have been observed. These impairments were found in various domains, such as attention, memory, executive functions, language, motor and visuomotor functions, among others. In line with contemporary research, other neurocognitive domains have recently been explored in TS, bringing evidence of altered social reasoning, for instance. Therefore, the aims of this review are to give an overview of the neuropsychological dimensions of TS, to report how neuropsychological functions evolve from childhood to adulthood, and to explain how various confounding factors can affect TS patients' performance in neuropsychological tasks. Finally, an important contribution of this review is to show how recent research has confirmed or changed our beliefs about neuropsychological functioning in TS.

Cognitive flexibility and its electrophysiological correlates in Gilles de la Tourette syndrome

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Gilles de la Tourette syndrome (GTS) may involve cognitive inflexibility.

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A meta-analysis reveals GTS-related deficits on the Wisconsin Card Sorting Test.

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Card-sorting deficits are larger in children than in adults with GTS.

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Adults with GTS show electrophysiological signs of enhanced cognitive control.

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This change may underlie the normalization of cognitive flexibility in adult GTS.

Motor symptoms in Gilles de la Tourette syndrome (GTS) have been related to changes in frontostriatal brain networks. These changes may also give rise to alterations in cognitive flexibility. However, conclusive evidence for altered cognitive flexibility in patients with GTS is still lacking. Here, we meta-analyzed data from 20 neuropsychological studies that investigated cognitive flexibility in GTS using the Wisconsin Card Sorting Test (WCST). Results revealed medium-sized GTS-related performance deficits, which were significantly modulated by age: Whilst being substantial in children and adolescents with GTS, WCST deficits seem to dissolve in adult patients with GTS. This age-related normalization of WCST performance might result from the compensatory recruitment of cognitive control in adult patients with GTS. We addressed this possibility by examining neural correlates of proactive and reactive cognitive control in an event-related potential (ERP) study. We analyzed cue- and target-locked ERPs from 23 adult patients with GTS and 26 matched controls who completed a computerized version of the WCST. Compared to controls, patients with GTS showed a marked increase in parietal cue-locked P3 activity, indicating enhanced proactive cognitive control. We conclude that the additional recruitment of proactive cognitive control might ensure flexible cognitive functioning in adult patients with GTS.

Cortical excitability and neuropsychological functioning in healthy adults

Evidence from clinical populations, such as epilepsy and attention deficit/hyperactivity disorder, suggests a relationship between hyperexcitability and cognitive impairment, but this relationship has not been demonstrated in healthy individuals. Here, we investigate the relationship between cortical excitability and cognitive functioning in healthy adults. Single- and paired-pulse TMS was applied to 20 healthy adults to measure cortical excitability and long-interval intracortical inhibition (LICI). A neuropsychological battery was administered to assess aspects of attention, executive function, and mood. Participants with primarily excitatory responses to the LICI paradigm performed worse on a composite measure of attention and reported more negative mood states than participants with primarily inhibitory responses. Thus, differences in attention and mood among healthy adults are related to differences in cortical excitability as measured by LICI. This is consistent with a role for GABA_B inhibitory circuits in regulating attention and mood, and suggests that individual variability in these domains may reflect variability in cortical excitability. This study demonstrates preliminary evidence that increased cortical excitability is associated with poorer cognition and mood in healthy adults. These findings provide new insight into the presence of cognitive dysfunction in several patient populations with hyperexcitability and support the development of neurostimulation interventions for clinical use.

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.

The puzzling question of inhibitory control in Tourette syndrome: A meta-analysis

Tourette syndrome (TS) is a neuropsychiatric disorder involving motor and phonic tics. Inhibitory control is a key issue in TS, and many disruptive or impulsive behaviors might arise from inhibitory deficits. However, conflicting findings regarding TS patients' inhibitory performance in neuropsychological tasks have been reported throughout the literature. Therefore, this meta-analysis aimed to evaluate inhibitory control through neuropsychological tasks, and to analyze the factors modulating inhibitory deficits. To this end, a literature search was performed through MEDLINE and PsycINFO, to retrieve studies including neuropsychological tasks that assessed inhibitory control in TS patients. Of the 4020 studies identified, 61 were included in the meta-analysis, for a total of 1717 TS patients. Our analyses revealed a small to medium effect in favor of inhibitory deficits in TS patients. This effect was larger in TS+ADHD patients, but pure TS patients also showed some inhibitory deficits. Therefore, deficits in inhibitory control seem to be an inherent component of TS, and are exacerbated when ADHD is concomitant.

Oculomotor Abnormalities in Children with Attention-Deficit/Hyperactivity Disorder Are Improved by Methylphenidate

BACKGROUND

There are relatively few studies of saccadic eye movements in children with attention-deficit/hyperactivity disorder (ADHD). The aim of this study was to examine inhibitory abilities of eye movements in children with ADHD and to explore the effect of methylphenidate (MPH) on eye movement performance.

METHODS

Thirty-one children with ADHD (mean age 9.9 ± 0.4 years) and 31 sex-, age-, and IQ-matched children with normal development were examined. Saccades elicited not only by the gap, step, overlap, and antisaccade paradigms but also a simple fixation paradigm have been recorded using an eye tracker. The latency of each type of saccade, the error rate of antisaccades, and the number of saccades made during fixation have been measured.

RESULTS

Children with ADHD and naive to treatment with respect to controls showed significantly shorter mean latency of voluntary saccades (overlap paradigm), more frequent errors during the antisaccade paradigm, and higher number of saccades made during fixation. After 1 month of MPH treatment, all these parameters changed significantly and reached control values.

CONCLUSION

Taken together, these results suggest that oculomotor abilities are poor in children with ADHD, which may correlate with deficits in inhibitory mechanisms. Treatment with MPH improves oculomotor performances through adaptive strategies, which may involve brain structures related to cognitive inhibition.

Dissociable Response Inhibition in Children With Tourette's Syndrome Compared With Children With ADHD

OBJECTIVE

This study investigates whether performance in a verbal response task (Color-Word Interference Test [CWIT]) and a motor response task (Conners' Continuous Performance Test [CCPT]) discriminates children with Tourette's Syndrome (TS), ADHD, and typically developing children (TDC).

METHOD

Nineteen children with TS, 79 with ADHD, and 50 with TDC participated (8-17 years).

RESULTS

Children with TS committed significantly fewer errors in the verbal response task than those with ADHD. Moreover, children with TS but without ADHD performed better than TDC. Errors in motor task and speed of response did not distinguish between groups. A cautious tendency of response correlated positively with rates of tics in children with TS.

CONCLUSION

Children with TS were superior in inhibiting a prepotent verbal response; however, comorbidity with ADHD in those children negatively influenced performance. Results support the hypothesis that levels of inhibitory control distinguish children with TS, ADHD, and TDC.

Cognitive Flexibility and Social Responsiveness in Children and Adolescents with Tourette Syndrome

This study examined cognitive flexibility and social responsiveness in children and adolescents with Tourette Syndrome (TS). Thirty one subjects with TS were compared to 32 age-matched healthy controls. Assessments included semi-structured interviews to assess psychopathology, parent-rated Social Responsiveness Scale (SRS) and a brief neuropsychological battery selected as measures of cognitive flexibility. Completion time for both Trail Making Tests (TMT-A and TMT-B) were significantly longer for TS group than controls, however the difference in perseverative errors on Wisconsin Card Sorting Test (WCST) was not significant. SRS total score was significantly higher in the TS group compared to controls, indicating greater impairment in social responsiveness. Group difference for TMTs and SRS failed to reach significance after controlling for co-occurring conditions. Clinicians might consider social impairment in the evaluation plan of children and adolescents with Tourette syndrome.

Jitter Reduces Response-Time Variability in ADHD: An Ex-Gaussian Analysis

OBJECTIVE

"Jitter" involves randomization of intervals between stimulus events. Compared with controls, individuals with ADHD demonstrate greater intrasubject variability (ISV) performing tasks with fixed interstimulus intervals (ISIs). Because Gaussian curves mask the effect of extremely slow or fast response times (RTs), ex-Gaussian approaches have been applied to study ISV.

METHOD

This study applied ex-Gaussian analysis to examine the effects of jitter on RT variability in children with and without ADHD. A total of 75 children, aged 9 to 14 years (44 ADHD, 31 controls), completed a go/no-go test with two conditions: fixed ISI and jittered ISI.

RESULTS

ADHD children showed greater variability, driven by elevations in exponential (tau), but not normal (sigma) components of the RT distribution. Jitter decreased tau in ADHD to levels not statistically different than controls, reducing lapses in performance characteristic of impaired response control.

CONCLUSION

Jitter may provide a nonpharmacologic mechanism to facilitate readiness to respond and reduce lapses from sustained (controlled) performance.

Executive function and attention-deficit/hyperactivity disorder in Ugandan children with perinatal HIV exposure

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is among the most commonly diagnosed mental disorders in childhood and is associated with substantial deficits in executive functioning and lost academic and occupational attainment. This study evaluates symptoms of ADHD and their association with neurocognitive deficits in a cohort of rural Ugandan children who were born to HIV-infected mothers.

METHODS

We assessed ADHD symptoms and executive function (including memory and attention) in a non-clinical sample of children born to HIV-infected mothers in rural eastern Uganda. Analyses included assessments of the psychometric properties, factor structure, and convergent and discriminant validity of the ADHD measure (ADHD-Rating Scale-IV); and executive function deficits in children meeting symptom criteria for ADHD.

RESULTS

232 children [54% female; mean age 7.8 years (s.d. 2.0)] were assessed for ADHD and executive function deficits. The ADHD measure showed good internal consistency (α = 0.85.) Confirmatory factor analysis showed an acceptable fit for the diagnostic and statistical manual of mental disorders (DSM-5) two-factor model. Subjects meeting DSM-5 symptom criteria for ADHD had worse parent-rated executive function on six out of seven subscales.

CONCLUSIONS

Our results demonstrate structural validity of the ADHD measure with this population, strong associations between ADHD symptom severity and poorer executive function, and higher levels of executive function problems in perinatally HIV-exposed Ugandan children with ADHD. These findings suggest that ADHD may be an important neurocognitive disorder associated with executive function problems among children in sub-Saharan African settings where perinatal HIV exposure is common.

[Development of the Subjective Urge Scale and its usefulness in people with tic disorders]

The impulsivity of people with tic disorder has been a recent focus of attention. This study aimed to investigate this phenomenon in people with and without tics in a non-clinical setting, focusing on the subjective urge experienced prior to impulsive behavior. In Study 1, we created a scale to measure the strength of subjective urges. This scale, which was found to comprise three subscales, had high internal consistency and high generalizability. In Study 2, using the scale developed in Study 1, we showed that people with tics felt stronger subjective urges than people without tics. This suggests that the relation between tics and impulsivity exists not only among people in clinical settings but also in non-clinical settings. Also, subjective urges significantly affect the severity of depression and this elfect was pronounced in people with tics in this study. Thus. we should consider the presence or absence of tics when we discuss impulsivity, in particular the effect of subjective urges on depression.

Pediatric Tourette syndrome: insights from recent neuroimaging studies

Tourette syndrome has been examined using many different neuroimaging techniques. There has been a recent surge of neuroimaging research papers related to Tourette syndrome that are exploring many different aspects of the disorder and its comorbidities. This brief review focuses on recent MRI-based imaging studies of pediatric Tourette syndrome, including anatomical, functional, resting state, and diffusion tensor MRI techniques. Consistencies across studies are explored, and particularly important issues involved in acquiring data from this special population are discussed.

The role of nicotinic receptors in shaping and functioning of the glutamatergic system: a window into cognitive pathology

The involvement of the cholinergic system in learning, memory and attention has long been recognized, although its neurobiological mechanisms are not fully understood. Recent evidence identifies the endogenous cholinergic signaling via nicotinic acetylcholine receptors (nAChRs) as key players in determining the morphological and functional maturation of the glutamatergic system. Here, we review the available experimental and clinical evidence of nAChRs contribution to the establishment of the glutamatergic system, and therefore to cognitive function. We provide some clues of the putative underlying molecular mechanisms and discuss recent human studies that associate genetic variability of the genes encoding nAChR subunits with cognitive disorders. Finally, we discuss the new avenues to therapeutically targeting nAChRs in persons with cognitive dysfunction for which the α7-nAChR subunit is an important etiological mechanism.

Performance lapses in children with attention-deficit/hyperactivity disorder contribute to poor reading fluency

Children with Attention-Deficit/Hyperactivity Disorder (ADHD) demonstrate increased response variability compared with controls, which is thought to be associated with deficits in attention regulation and response control that subsequently affect performance of more cognitively demanding tasks, such as reading. The present study examined response variability during a computerized simple reaction time (RT) task in 67 children. Ex-Gaussian analyses separated the response time distribution into normal (mu and sigma) and exponential (tau) components; the association of each with reading fluency was examined. Children with ADHD had significantly slower, more variable, and more skewed RTs compared with controls. After controlling for ADHD symptom severity, tau (but not mu or mean RT) was significantly associated with reduced reading fluency, but not with single word reading accuracy. These data support the growing evidence that RT variability, but not simply slower mean response speed, is the characteristic of youth with ADHD and that longer response time latencies (tau) may be implicated in the poorer academic performance associated with ADHD.

Motor excitability is reduced prior to voluntary movements in children and adolescents with Tourette syndrome

Tourette syndrome (TS) is a neuro-developmental disorder characterized by the occurrence of motor and vocal tics: involuntary, repetitive, stereotyped behaviours that occur with a limited duration, often typically many times in a single day. Previous studies suggest that children and adolescents with TS may undergo compensatory, neuroplastic changes in brain structure and function that help them gain control over their tics. In the current study we used single-pulse and dual-site paired-pulse transcranial magnetic stimulation (TMS), in conjunction with a manual choice reaction time task that induces high levels of inter-manual conflict, to investigate this conjecture in a group of children and adolescents with TS, but without co-morbid Attention Deficit Hyperactivity Disorder (ADHD). We found that performance on the behavioural response-conflict task did not differ between the adolescents with TS and a group of age-matched typically developing individuals. By contrast, our study demonstrated that cortical excitability, as measured by TMS-induced motor-evoked potentials (MEPs), was significantly reduced in the TS group in the period immediately preceding a finger movement. This effect is interpreted as consistent with previous suggestions that the cortical hyper-excitability that may give rise to tics in TS is actively suppressed by cognitive control mechanisms. Finally, we found no reliable evidence for altered patterns of functional inter-hemispheric connectivity in TS. These results provide evidence for compensatory brain reorganization that may underlie the increased self-regulation mechanisms that have been hypothesized to bring about the control of tics during adolescence.

Youths with ADHD with and without tic disorders: comorbid psychopathology, executive function and social adjustment

Attention deficit/hyperactivity disorder (ADHD) and tic disorders (TD) commonly co-occur. Clarifying the psychiatric comorbidities, executive functions and social adjustment difficulties in children and adolescents of ADHD with and without TD is informative to understand the developmental psychopathology and to identify their specific clinical needs. This matched case-control study compared three groups (n=40 each) of youths aged between 8 and 16 years: ADHD with co-occurring TD (ADHD+TD), ADHD without TD (ADHD-TD) and typically developing community controls. Both ADHD groups had more co-occurring oppositional defiant disorder than the control group, and the presence of TD was associated with more anxiety disorders. TD did not impose additional executive function impairments or social adjustment difficulties on ADHD. Interestingly, for youths with ADHD, the presence of TD was associated with less interpersonal difficulties at school, compared to those without TD. The potential various directions of effects from co-occurring TD should be carefully evaluated and investigated for youths with ADHD.

Dual Task Performance in Children With Tourette Syndrome: Controlling for Comorbid ADHD

Dual task performance in children with Tourette Syndrome (TS) was studied. The participants were children with TS (N = 48, 40 male, 8 female), Attention Deficit Hyperactivity Disorder (ADHD; mixed types N = 44, 34 male, 10 female) and unaffected controls (N = 48, 34 male, 14 female). Eleven of the TS participants had no comorbidities (TS only) and they were compared to matched groups of participants with TS plus comorbidities (TS+), ADHD, and controls. Each participant was administered screening measures of behaviour, intelligence and verbal ability, as well as specific tests of dual task performance. Children with TS-only correctly recalled fewer digit span forward trials, and identified fewer spaceship pairs than controls under single task conditions in the SkySearch subtest of the Test of Everyday Attention for Children. However, the TS-only and control groups showed better counting performance while simultaneously searching for targets, than the TS+ and ADHD groups. Taken together, these results suggest that some previously reported cognitive deficits in children with TS are due to comorbidities, rather than to the syndrome itself.

Tourette syndrome and other tic disorders

Tic disorders, including Tourette syndrome, are an intriguing group of paroxysmal movement abnormalities that begin in childhood, have a fluctuating course, are capable of causing psychosocial and physical problems, and often improve by early adulthood. These disorders are frequently associated with a variety of comorbid problems whose negative effects may exceed those of tics. Therapy is strictly symptomatic and usually includes educational, behavioral, and a variety of pharmacological therapies. Although there is strong evidence supporting an inherited basis, the precise genetic abnormality remains unknown. A proposed poststreptococcal autoimmune etiology remains controversial. Pathophysiologically, tics appear to arise from an alteration within cortico-striatal-thalamo-cortical circuits, but the definitive site is unknown. Evidence supports an abnormality of synaptic neurotransmission, likely involving the dopaminergic system.

European clinical guidelines for Tourette syndrome and other tic disorders. Part I: assessment

A working group of the European Society for the Study of Tourette Syndrome (ESSTS) has developed the first European assessment guidelines of Tourette Syndrome (TS). The available literature including national guidelines was thoroughly screened and extensively discussed in the expert group of ESSTS members. Detailed clinical assessment guidelines of tic disorders and their comorbidities in both children and adults are presented. Screening methods that might be helpful and necessary for specialists' differential diagnosis process are suggested in order to further analyse cognitive abilities, emotional functions and motor skills. Besides clinical interviews and physical examination, additional specific tools (questionnaires, checklists and neuropsychological tests) are recommended.

Performance on Wechsler intelligence scales in children with Tourette syndrome

BACKGROUND

There is some evidence that Tourette syndrome is associated with cognitive disabilities.

AIMS

To examine the cognitive performance of a clinical cohort of children with Tourette syndrome.

METHODS

266 children with Tourette syndrome have been examined with Wechsler Intelligence Scales. The presence of the co-morbidities attention deficit hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD) was assessed using validated diagnostic instruments. Eighty healthy controls matched a part of the TS cohort.

RESULTS

The children with Tourette syndrome had a mean verbal IQ (VIQ) of 92.9, performance IQ (PIQ) of 87.1, and full-scale IQ (FSIQ) of 88.8. We found statistically significant higher PIQ and FSIQ in the control group compared with a matched TS cohort and a trend towards a higher VIQ among the healthy controls. There was a statistically significant influence of age at onset of tics on PIQ. The children with co-morbid OCD scored higher on FSIQ compared with the other groups. The children with co-morbid ADHD and OCD showed problems in motor tasks and speed tasks and the children with co-morbid ADHD showed attention deficits.

CONCLUSIONS

Children with Tourette syndrome have lower IQ scores than the general population (but less than one standard deviation below) and our control group. Early onset of tics and the presence of co-morbidities might cause specific deficits on cognitive performance.

Impaired comprehension of nonliteral language in Tourette syndrome

OBJECTIVE

To investigate theory of mind and the understanding of nonliteral language in patients with Tourette syndrome (TS).

BACKGROUND

In TS, striatal dysfunction could affect the functioning of the frontal cortex. Changes in frontal functioning could lead to impairments in theory of mind: the understanding of mental states, such as beliefs, emotions, and intentions. Poor understanding of a speaker's mental state may also impair interpretation of their nonliteral remarks.

METHOD

In this study, patients with TS and healthy controls completed tasks to assess their understanding of sarcasm, metaphor, indirect requests, and theory of mind. These tasks were the Pragmatic Story Comprehension Task, the Hinting task, and a faux pas task. Inhibitory ability was also assessed through the use of the Hayling task and a black and white Stroop test.

RESULTS

Patients with TS exhibited significant impairment on the faux pas task and Pragmatic Story Comprehension Task despite limited evidence of inhibitory impairment.

CONCLUSION

TS may be associated with changes in theory of mind.

Interstimulus jitter facilitates response control in children with ADHD

Interstimulus "jitter" involves randomization of intervals between successive stimulus events, and can facilitate performance on go/no-go tests among healthy adults, though its effect in clinical populations is unclear. Children with Attention-deficit/Hyperactivity Disorder (ADHD) commonly exhibit deficient response control, leading to increased intra-subject variability (ISV), which has been linked to anomalous functioning within frontal circuits, as well as their interaction with posterior "default mode" regions. We examined effects of interstimulus jitter on response variability in 39 children, ages 9-14 years (25 ADHD, 14 controls). Participants completed 2 computerized go/no-go tests: one with fixed interstimulus interval (ISI) and one with jittered ISI. Repeated measures analysis of variance (ANOVA) revealed a significant group-by test interaction, such that introduction of jitter produced a significant decrease in ISV among children with ADHD, but not among controls. Whereas children with ADHD were significantly more variable than controls on the go/no-go test with fixed ISI, their performance with jittered ISI was equivalent to that of controls. Jittering stimulus presentation provides a nonpharmacologic mechanism for improving response control in ADHD. This bottom-up approach may be mediated by increases in vigilance through noradrenergic circuits that facilitate maintenance of frontal circuits critical to response control.

Tourette syndrome in the general child population: cognitive functioning and self- perception

The aim of the study was to examine the cognitive function and self-perception in a school-population-based sample of children with Tourette syndrome (TS). Many studies have examined cognitive and emotional functioning in clinical samples but to our knowledge, there is no population-based study of TS in schoolchildren. In a population-based sample identified in a rigid diagnostic procedure (n = 25), cognitive functioning and self-perception were examined. There was a large variation in the cognitive functioning of children with TS, at least one third obtaining subnormal results. The profile of index scores on the Wechsler Intelligence Scale for Children (WISC) factors was somewhat uneven, with the freedom from distractibility and processing speed factors presenting the lowest median scores. The TS group had more negative self-perceptions than a comparison group. Tic severity or age at onset was not associated with cognitive performance or self-perception. Children who were taking medication had lower full IQ scores than children who were not. Low cognitive abilities and negative self-perception may be common in community-based samples of children with Tourette syndrome.

Neuropsychological aspects of Tourette syndrome: a review

Tourette syndrome (TS) is assumed to result from frontostriatal dysfunction, which would be expected to result in impairments in neuropsychological functions. This possibility has been explored in a number of studies that have assessed the performance of patients with TS within major cognitive domains and on tests involving executive functioning. We aim to summarize the main findings of these studies while evaluating the influence of task limitations and potentially critical confounding factors such as the presence of comorbidity. Although there is clearly a need for improved study design, we tentatively suggest that there is considerable evidence for cognitive impairment in a subgroup of patients, and that some difficulties seem to be intrinsic to TS. These impairments may reflect dysfunction of the anterior cingulate network within the frontostriatal pathway.

Transcranial magnetic stimulation in Gilles de la Tourette syndrome

The cause of Gilles de la Tourette syndrome (GTS), a chronic motor and vocal tic disorder of childhood onset, remains unknown. Abnormalities in basal ganglia-thalamo-cortical circuits presumably play an important role in the pathophysiology underlying the involuntary tics. The use of transcranial magnetic stimulation (TMS), a noninvasive and painless tool to examine the excitability of several different circuits in the human motor cortex has advanced our understanding of the pathophysiology. Motor thresholds are similar in GTS and healthy subjects; in the resting state, recruitment of motor evoked potentials (MEPs) above threshold is more gradual in patients than controls. In contrast, recruitment of MEPs during preactivation is similar in both groups, as is the duration of the cortical silent period. This suggests that the distribution of excitability in the corticospinal system in patients at rest is different to that in healthy individuals. Importantly, correlation analysis showed that reduced levels of excitability at rest relate, in pure GTS patients, to video ratings of complex tics, and hand and finger tics, with less excitability predicting fewer tics. The correlations disappear for measures made during voluntary activation. This suggests that this is an adaptive response to abnormal basal ganglia-motor cortex inputs in an effort to reduce unwanted movements, a notion supported by electroencephalography-coherence studies that show increased cortico-cortical coupling. Compared to the healthy control group, short intracortical inhibition (SICI) thresholds are similar. However, above-threshold SICI recruitment and sensory afferent inhibition (SAI), a paradigm to examine sensory motor integration, are reduced in patients. This is consistent with the suggestion that reduced excitability of cortical inhibition is one factor that contributes to the difficulty that patients have in suppressing involuntary tics. In addition the reduced SAI indicates that impaired intracortical inhibition may not be limited to the motor cortex but also involves circuits linking sensory input and motor output. GTS with attention deficit hyperactivity disorder comorbidity is associated with more extensive changes in the excitability of motor cortex circuits than pure GTS or GTS+obsessive-compulsive disorder. The extent to which various different neuronal circuits are affected may be relevant for the phenotype of Tourette spectrum disorders.

Oculomotor anomalies in attention-deficit/hyperactivity disorder: evidence for deficits in response preparation and inhibition

OBJECTIVE

To examine patterns of executive and oculomotor control in a group of both boys and girls with attention-deficit/hyperactivity disorder (ADHD).

METHOD

Cross-sectional study of 120 children aged 8 to 12 years, including 60 with ADHD (24 girls) and 60 typically developing controls (29 girls). Oculomotor paradigms included visually guided saccades (VGS), antisaccades, memory-guided saccades, and a go/no-go test, with variables of interest emphasizing response preparation, response inhibition, and working memory.

RESULTS

As a group, children with ADHD demonstrated significant deficits in oculomotor response preparation (VGS latency and variability) and response inhibition but not working memory. Girls, but not boys with ADHD, had significantly longer VGS latencies, even after controlling for differences in ADHD symptom severity. The ADHD subtypes did not differ on response preparation or inhibition measures; however, children with the Inattentive subtype were less accurate on the working memory task than those with the Combined subtype.

CONCLUSIONS

Sex differences in children with ADHD extend beyond symptom presentation to the development of oculomotor control. Saccade latency may represent a specific deficit among girls with ADHD.

Executive functioning differences between adults with attention deficit hyperactivity disorder and autistic spectrum disorder in initiation, planning and strategy formation

Executive functioning deficits characterize the neuropsychological profiles of the childhood neurodevelopmental disorders of attention deficit hyperactivity disorder (ADHD) and autistic spectrum disorder (ASD). This study sought to determine whether similar impairments exist in adults with ADHD (N = 53) and ASD (N = 45) in comparison with a healthy control group (N = 31), whether the two disorders can be distinguished on the basis of their executive functioning features, and whether these impairments are related to symptom severity. Both clinical groups were found to exhibit executive functioning deficits. The ADHD group had difficulty withholding a response, with relative preservation of initiation and planning abilities. In contrast, the ASD group exhibited significant impairments in initiation, planning and strategy formation. The specific executive functioning deficits were related to severity of response inhibition impairments in ADHD and stereotyped, repetitive behaviours in ASD. These findings suggest the pattern of executive functioning deficits follows a consistent trajectory into adulthood.

Electrophysiological manifestations of stimulus evaluation, response inhibition and motor processing in Tourette syndrome patients

Gilles de la Tourette syndrome (GTS) is a neuropsychiatric disorder with childhood onset presenting with multiple fluctuating motor tics and one or more phonic tics. A significant proportion of people suffering from GTS are still symptomatic in adulthood and present other emotional and cognitive difficulties, along with motor problems that often accompany these comorbid conditions. The nature of these difficulties is still poorly understood and multiple comorbidities are often inadequately controlled. The current study investigates both stimulus evaluation and motor processing in GTS while controlling for comorbidity. Fifteen adults with GTS and 20 control participants were matched on gender, laterality and intelligence. The P300 component, the no-go anteriorization (NGA) as well as the stimulus and response-locked lateralized-readiness potentials (S-LRP, R-LRP) were elicited during a stimulus-response compatibility (SRC) paradigm. The standard version of the Stroop Color-Word Test (SCWT) was also administered. Reaction times showed that participants with GTS processed both the SRC and the SCWT more rapidly than the control group, while producing a delayed P300 peak latency. The GTS group also showed faster S-LRP onset in response to the incompatible and faster processing of interference in the SCWT. There was also a tendency toward a greater frontal shift of the NGA in the GTS group. The P300 latency showed that with GTS patients, stimulus evaluation occurs later whereas the overlapping pre-motor response selection processes occur faster. Our findings are congruent with a probable cortical motor over-activation hypothesis of GTS involving faster motor program selection in processing conflicting SR configuration.

Response variability in rapid automatized naming predicts reading comprehension

A total of 37 children ages 8 to 14 years, screened for word-reading difficulties (23 with attention-deficit/hyperactivity disorder, ADHD; 14 controls) completed oral reading and rapid automatized naming (RAN) tests. RAN trials were segmented into pause and articulation time and intraindividual variability. There were no group differences on reading or RAN variables. Color- and letter-naming pause times and number-naming articulation time were significant predictors of reading fluency. In contrast, number and letter pause variability were predictors of comprehension. Results support analysis of subcomponents of RAN and add to literature emphasizing intraindividual variability as a marker for response preparation, which has relevance to reading comprehension.

Arithmetic performance in children with Tourette syndrome: relative contribution of cognitive and attentional factors

The study addressed the issue of arithmetic deficiencies in children with Tourette syndrome (TS) as well as explanations for such deficiencies. A total of 47 children with TS were assigned to three subgroups based on a composite attention score from the Test of Variables of Attention (TOVA). These children, along with 17 normal controls between 8 and 16 years of age, were tested on standardized measures of IQ, attention, visuospatial ability, and arithmetic achievement. The children also were administered an experimental calculation task with two levels of structure. Children with TS scored below controls on tests of IQ, attention, and arithmetic achievement but not visuospatial ability. The TS subgroup with the greatest impairment of attention accounted for most of the differences in arithmetic achievement. Regression analysis, based on the 47 children with TS, indicated that IQ and TOVA scores were the best predictors of arithmetic achievement. Likewise, the experimental calculation task indicated that the poor performance of some children with TS could be attributed to deficient attention. Irrespective of structure, children in the TS subgroup with the greatest attentional impairment made more attention (but not visuospatial) errors than did controls on the experimental task. Thus, on both the standardized and the experimental tasks, poor arithmetic skill was found only in children with TS who had significant attentional deficits.

Neurocognitive correlates of child obsessive compulsive disorder and Tourette syndrome

This study investigated the neurocognitive correlates of childhood OCD and TS, which are purported to share frontal-striatal dysfunction. Neurocognitive measures tapping frontal-striatal functions such as executive, attention/memory, and visuomotor abilities were administered to three groups of participants, OCD without comorbid TS (OCD), TS without comorbid OCD (TS), and normal controls. Results suggested that OCD group demonstrated deficits in the area of spatial attention relative to healthy controls. The OCD participants demonstrated no cognitive deficits compared to the TS group. TS participants showed trends towards impairments in the areas of response inhibition, divided attention, and cognitive flexibility relative to the OCD and normal control groups. Spatial attention deficits for the OCD group are partially consistent with adult OCD studies indicating deficits in spatial memory. TS findings were less robust and may be construed tentatively as suggestive of executive function deficits. Future research is needed to delineate the influence of development on neurocognitive deficits associated with OCD and TS.

Process examination of executive function in ADHD: sex and subtype effects

To examine effects of group (Attention-Deficit/Hyperactivity Disorder [ADHD] versus Typically Developing [TD]), sex, and ADHD subtype on "process/optional" measures of executive functioning, children (n = 123; 54 ADHD, 69 TD) aged 8-16 completed subtests from the D-KEFS. No group, sex, or ADHD subtype effects were found on optional measures from the Trail Making, Color-Word Interference, and Tower tests. A significant interaction was found for Verbal Fluency Total Repetition Errors; boys with Combined/Hyperactive-Impulsive (ADHD-C/HI) type ADHD performed better than ADHD-C/HI girls, whereas girls with Inattentive type ADHD (ADHD-I) performed better than ADHD-I boys. Overall, children with ADHD did not differ from TD on most optional measures from the D-KEFS. When sex and ADHD subtype were considered, children with the subtype of ADHD less common for sex were at greater risk for poorer performance.