Task control signals in pediatric tourette syndrome show evidence of immature and anomalous functional activity

A scoping review of oral language and social communication abilities in children with Tourette syndrome

BACKGROUND

Children with Tourette syndrome (TS) have historically experienced problems in academic and social settings, yet their language and communication abilities have not been extensively researched.

AIMS

This scoping review maps the literature on the oral language and social communication abilities of children with TS in order to describe the nature of the current literature, present a summary of major findings and identify where gaps exist.

METHODS

A scoping review was completed to identify studies measuring the oral language or social communication abilities of children with TS. A systematic search of six electronic databases was conducted to obtain published and unpublished literature. All English studies measuring the oral language or social communication abilities of children with TS were included. Information was extracted from records and knowledge was synthesised in a narrative summary.

MAIN CONTRIBUTION

We identified 56 records for inclusion. Almost all records were located in journals within the fields of psychology and psychiatry. Skills most often studied were verbal IQ and verbal fluency. The literature suggests an increased prevalence of language disorders and social communication problems in children with TS; however, literature comprehensively detailing these challenges was scarce. Language strengths were identified in verbal intelligence, story/sentence recall, categorisation and performance on tasks at the single-word level.

CONCLUSIONS

Oral language and social communication skills are important for academic and social success. This review brings scattered literature together to provide up-to-date information about language in children with TS and highlights that there are considerable gaps in our knowledge about language and communication in this population. This scoping review can inform future research and support speech language pathologists in the assessment of young people with TS.

WHAT THIS PAPER ADDS

What is already known on the subject Speech-language pathologists (SLPs) working in various contexts (e.g., schools, mental health teams) are likely to encounter children with Tourette syndrome (TS); however, the description of this population and potential communication characteristics is not well represented in the SLP literature. Previous literature reviews have reported strengths in verbal fluency and morphological processing. Challenges in expressive language, higher order language, social cognition and a propensity towards autistic traits have also been identified. What this paper adds to existing knowledge This review differs from previous narrative reviews by employing a systematic approach to searching for literature. As a result, we identified 25 additional studies that had not been cited in previous reviews and additional relevant findings in 23 previously reviewed studies. This review confirms several previous conclusions about language in children with TS and extends or clarifies several others, thereby providing the most current information on oral language and social communication abilities. The use of current taxonomies of language and social communication helps to organise this literature for clinicians and researchers in speech-language pathology and identifies a need for further research from the SLP perspective. What are the potential or actual clinical implications of this work? These results imply that SLPs should screen children with TS for language disorders and investigate social communication and social interaction development. Clinicians can expect greater challenges in language and communication development for children with complex forms of TS (i.e., those who exhibit co-occurring conditions such as attention-deficit/hyperactivity disorder). The multidisciplinary nature of the current literature implies that clinical collaboration with other disciplines will be of particular benefit to serving this group of children.

Emerging neurodevelopmental perspectives on mathematical learning

Strong foundational skills in mathematical problem solving, acquired in early childhood, are critical not only for success in the science, technology, engineering, and mathematical (STEM) fields but also for quantitative reasoning in everyday life. The acquisition of mathematical skills relies on protracted interactive specialization of functional brain networks across development. Using a systems neuroscience approach, this review synthesizes emerging perspectives on neurodevelopmental pathways of mathematical learning, highlighting the functional brain architecture that supports these processes and sources of heterogeneity in mathematical skill acquisition. We identify the core neural building blocks of numerical cognition, anchored in the posterior parietal and ventral temporal-occipital cortices, and describe how memory and cognitive control systems, anchored in the medial temporal lobe and prefrontal cortex, help scaffold mathematical skill development. We highlight how interactive specialization of functional circuits influences mathematical learning across different stages of development. Functional and structural brain integrity and plasticity associated with math learning can be examined using an individual differences approach to better understand sources of heterogeneity in learning, including cognitive, affective, motivational, and sociocultural factors. Our review emphasizes the dynamic role of neurodevelopmental processes in mathematical learning and cognitive development more generally.

Inhibitory control in children with tic disorder: aberrant fronto-parietal network activity and connectivity

Chronic tic disorders, including Tourette syndrome, are typically thought to have deficits in cognitive inhibition and top down cognitive control due to the frequent and repetitive occurrence of tics, yet studies reporting task performance results have been equivocal. Despite similar behavioural performance, individuals with chronic tic disorder have exhibited aberrant patterns of neural activation in multiple frontal and parietal regions relative to healthy controls during inhibitory control paradigms. In addition to these top down attentional control regions, widespread alterations in brain activity across multiple neural networks have been reported. There is a dearth, however, of studies examining event-related connectivity during cognitive inhibitory paradigms among affected individuals. The goal of this study was to characterize neural oscillatory activity and effective connectivity, using a case–control design, among children with and without chronic tic disorder during performance of a cognitive inhibition task. Electroencephalogram data were recorded in a cohort of children aged 8–12 years old (60 with chronic tic disorder, 35 typically developing controls) while they performed a flanker task. While task accuracy did not differ by diagnosis, children with chronic tic disorder displayed significant cortical source-level, event-related spectral power differences during incongruent flanker trials, which required inhibitory control. Specifically, attenuated broad band oscillatory power modulation within the anterior cingulate cortex was observed relative to controls. Whole brain effective connectivity analyses indicated that children with chronic tic disorder exhibit greater information flow between the anterior cingulate and other fronto-parietal network hubs (midcingulate cortex and precuneus) relative to controls, who instead showed stronger connectivity between central and posterior nodes. Spectral power within the anterior cingulate was not significantly correlated with any connectivity edges, suggesting lower power and higher connectivity are independent (versus resultant) neural mechanisms. Significant correlations between clinical features, task performance and anterior cingulate spectral power and connectivity suggest this region is associated with tic impairment (r = −0.31, P = 0.03) and flanker task incongruent trial accuracy (r’s = −0.27 to −0.42, P’s = 0.0008–0.04). Attenuated activation of the anterior cingulate along with dysregulated information flow between and among nodes within the fronto-parietal attention network may be neural adaptations that result from frequent engagement of neural pathways needed for inhibitory control in chronic tic disorder.

Gilles de la Tourette Syndrome-A Disorder of Action-Perception Integration

Gilles de la Tourette syndrome is a multifaceted and complex neuropsychiatric disorder. Given that tics as motor phenomena are the defining and cardinal feature of Tourette syndrome, it has long been conceptualized as a motor/movement disorder. However, considering premonitory urges preceding tics, hypersensitivity to external stimuli and abnormalities in sensorimotor integration perceptual processes also seem to be relevant in the pathophysiology of Tourette syndrome. In addition, tic expression depends on attention and tics can, at least partly and transiently, be controlled, so that cognitive processes need to be considered as well. Against this background, explanatory concepts should encompass not only the motor phenomenon tic but also perceptual and cognitive processes. Representing a comprehensive theory of the processing of perceptions and actions paying particular attention to their interdependency and the role of cognitive control, the Theory of Event Coding seems to be a suitable conceptual framework for the understanding of Tourette syndrome. In fact, recent data suggests that addressing the relation between actions (i.e., tics) and perceptions (i.e., sensory phenomena like premonitory urges) in the context of event coding allows to gaining relevant insights into perception-action coding in Tourette syndrome indicating that perception action binding is abnormally strong in this disorder.

Non-invasive Brain Stimulation for the Treatment of Gilles de la Tourette Syndrome

Gilles de la Tourette Syndrome is a multifaceted neuropsychiatric disorder typically commencing in childhood and characterized by motor and phonic tics. Its pathophysiology is still incompletely understood. However, there is convincing evidence that structural and functional abnormalities in the basal ganglia, in cortico-striato-thalamo-cortical circuits, and some cortical areas including medial frontal regions and the prefrontal cortex as well as hyperactivity of the dopaminergic system are key findings. Conventional therapeutic approaches in addition to counseling comprise behavioral treatment, particularly habit reversal therapy, oral pharmacotherapy (antipsychotic medication, alpha-2-agonists) and botulinum toxin injections. In treatment-refractory Tourette syndrome, deep brain stimulation, particularly of the internal segment of the globus pallidus, is an option for a small minority of patients. Based on pathophysiological considerations, non-invasive brain stimulation might be a suitable alternative. Repetitive transcranial magnetic stimulation appears particularly attractive. It can lead to longer-lasting alterations of excitability and connectivity in cortical networks and inter-connected regions including the basal ganglia through the induction of neural plasticity. Stimulation of the primary motor and premotor cortex has so far not been shown to be clinically effective. Some studies, though, suggest that the supplementary motor area or the temporo-parietal junction might be more appropriate targets. In this manuscript, we will review the evidence for the usefulness of repetitive transcranial magnetic stimulation and transcranial electric stimulation as treatment options in Tourette syndrome. Based on pathophysiological considerations we will discuss the rational for other approaches of non-invasive brain stimulation including state informed repetitive transcranial magnetic stimulation.

Defining Individual-Specific Functional Neuroanatomy for Precision Psychiatry

Studies comparing diverse groups have shown that many psychiatric diseases involve disruptions across distributed large-scale networks of the brain. There is hope that functional magnetic resonance imaging (fMRI) functional connectivity techniques will shed light on these disruptions, providing prognostic and diagnostic biomarkers as well as targets for therapeutic interventions. However, to date, progress on clinical translation of fMRI methods has been limited. Here, we argue that this limited translation is driven by a combination of intersubject heterogeneity and the relatively low reliability of standard fMRI techniques at the individual level. We review a potential solution to these limitations: the use of new "precision" fMRI approaches that shift the focus of analysis from groups to single individuals through the use of extended data acquisition strategies. We begin by discussing the potential advantages of fMRI functional connectivity methods for improving our understanding of functional neuroanatomy and disruptions in psychiatric disorders. We then discuss the budding field of precision fMRI and findings garnered from this work. We demonstrate that precision fMRI can improve the reliability of functional connectivity measures, while showing high stability and sensitivity to individual differences. We close by discussing the application of these approaches to clinical settings.

Increased perception-action binding in Tourette syndrome

Gilles de la Tourette syndrome is a multifaceted neurodevelopmental disorder characterized by multiple motor and vocal tics. Research in Tourette syndrome has traditionally focused on the motor system. However, there is increasing evidence that perceptual and cognitive processes play a crucial role as well. Against this background it has been reasoned that processes linking perception and action might be particularly affected in these patients with the strength of perception-action binding being increased. However, this has not yet been studied experimentally. Here, we investigated adult Tourette patients within the framework of the ‘Theory of Event Coding’ using an experimental approach allowing us to directly test the strength of perception-action binding. We included 24 adult patients with Tourette syndrome and n = 24 healthy control subjects using a previously established visual-motor event file task with four levels of feature overlap requiring repeating or alternating responses. Concomitant to behavioural testing, EEG was recorded and analysed using temporal signal decomposition and source localization methods. On a behavioural level, perception-action binding was increased in Tourette patients. Tic frequency correlated with performance in conditions where unbinding processes of previously established perception-action bindings were required with higher tic frequency being associated with stronger perception-action binding. This suggests that perception-action binding is intimately related to the occurrence of tics. Analysis of EEG data showed that behavioural changes cannot be explained based on simple perceptual or motor processes. Instead, cognitive processes linking perception to action in inferior parietal cortices are crucial. Our findings suggest that motor or sensory processes alone are less relevant for the understanding of Tourette syndrome than cognitive processes engaged in linking and restructuring of perception-action association. A broader cognitive framework encompassing perception and action appears well suited to opening new routes for the understanding of Tourette syndrome.

The New Tics study: A Novel Approach to Pathophysiology and Cause of Tic Disorders

We report on the ongoing project "The New Tics Study: A Novel Approach to Pathophysiology and Cause of Tic Disorders," describing the work completed to date, ongoing studies and long-term goals. The overall goals of this research are to study the pathophysiology of Provisional Tic Disorder, and to study tic remission (or improvement) in a prospective fashion. Preliminary data collection for the project began almost 10 years ago. The current study is nearing completion of its third year, and has already reported several novel and important results. First, surprisingly, at least 90% of children who had experienced tics for only a mean of 3 months still had tics at the 12-month anniversary of their first tic, though in some cases tics were seen only with remote video observation of the child sitting alone. Thus almost all of them now had a DSM-5 diagnosis of Tourette's Disorder or Persistent (Chronic) Tic Disorder. Baseline clinical features that predicted 12-month outcome included tic severity, subsyndromal autism spectrum symptoms, an anxiety disorder, and a history of 3 or more phonic tics. Second, we found that poorer tic suppression ability when immediately rewarded for suppression predicted greater tic severity at follow-up. Third, striatal volumes did not predict outcome as hypothesized, but a larger hippocampus at baseline predicted worse severity at follow-up. Enrollment and data collection continue, including functional connectivity MRI (fcMRI) imaging, and additional analyses are planned once the full sample is enrolled.

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.

Atypical Functional Connectivity in Tourette Syndrome Differs Between Children and Adults

BACKGROUND

Tourette syndrome (TS) is a neuropsychiatric disorder with symptomatology that typically changes over development. Whether and how brain function in TS also differs across development has been largely understudied. Here, we used functional connectivity magnetic resonance imaging to examine whole-brain functional networks in children and adults with TS.

METHODS

Multivariate classification methods were used to find patterns among functional connections that distinguish individuals with TS from control subjects separately for children and adults (N = 202). We tested whether the patterns of connections that classify diagnosis in one age group (e.g., children) could classify diagnosis in another age group (e.g., adults). We also tested whether the developmental trajectory of these connections was altered in TS.

RESULTS

Diagnostic classification was successful in children and adults separately but expressly did not generalize across age groups, suggesting that the patterns of functional connections that best distinguished individuals with TS from control subjects were age specific. Developmental patterns among these functional connections used for diagnostic classification deviated from typical development. Brain networks in childhood TS appeared "older" and brain networks in adulthood TS appeared "younger" in comparison with typically developing individuals.

CONCLUSIONS

Our results demonstrate that brain networks are differentially altered in children and adults with TS. The observed developmental trajectory of affected connections is consistent with theories of accelerated and/or delayed maturation, but may also involve anomalous developmental pathways. These findings further our understanding of neurodevelopmental trajectories in TS and carry implications for future applications aimed at predicting the clinical course of TS in individuals over development.

Trans-diagnostic comparison of response inhibition in Tourette's disorder and obsessive-compulsive disorder

OBJECTIVES

Impaired response inhibition is related to neurodevelopmental disorders, such as Tourette's disorder (TD) and obsessive-compulsive disorder (OCD). Unlike OCD, in which neural correlates of response inhibition have been extensively studied, TD literature is limited. By using a Stop-Signal task, we investigated the neural mechanisms underlying response inhibition deficits in TD compared to OCD and healthy controls (HCs).

METHODS

Twenty-three TD patients, 20 OCD patients and 22 HCs were scanned (3T MRI). Region-of-interest analyses were performed between TD, OCD and HCs.

RESULTS

Performance was similar across all subject groups. During inhibition TD compared with HCs showed higher right inferior parietal cortex (IPC) activation. During error processing TD compared with HCs showed hyperactivity in the left cerebellum, right mesencephalon, and right insula. Three-group comparison showed an effect of group for error-related activation in the supplementary motor area (SMA). Post-hoc analyses showed higher error-related SMA activity in TD compared with OCD and HCs. Error-related left cerebellar activity correlated positively with tic severity.

CONCLUSIONS

Hyperactivation of IPC during inhibition and a widespread hyperactivated network during error processing in TD suggest compensatory inhibition- and error-related circuit recruitment to boost task performance. The lack of overlap with activation pattern in OCD suggests such compensatory mechanism is TD-specific.

Patterns and Predictors of Tic Suppressibility in Youth With Tic Disorders

Tic suppression is the primary target of tic disorder treatment, but factors that influence voluntary tic inhibition are not well understood. Several studies using the Tic Suppression Task have demonstrated significant inter-individual variability in tic suppressibility but have individually been underpowered to address correlates of tic suppression. The present study explored patterns and clinical correlates of reward-enhanced tic suppression in youth with tic disorders using a large, pooled dataset. Individual-level data from nine studies using the Tic Suppression Task were pooled, yielding a sample of 99 youth with tic disorders. Analyses examined patterns of tic suppressibility and the relationship between tic suppressibility and demographic and clinical characteristics. A large majority of youth demonstrated a high degree of tic suppression, but heterogeneous patterns of tic suppressibility were also observed. Better tic suppressibility was related to older age and more frequent tics but unrelated to other clinical variables, including presence of psychiatric comorbidity, psychotropic medication status, tic and premonitory urge severity, and self-rated tic suppressibility. The mechanisms underlying the observed heterogeneity in reward-enhanced tic suppressibility warrant further investigation. The Tic Suppression Task is a promising method for testing mechanistic hypotheses related to tic suppression.

Altered topology of structural brain networks in patients with Gilles de la Tourette syndrome

Gilles de la Tourette syndrome is a neurodevelopmental disorder characterized by tics. Abnormal neuronal circuits in a wide-spread structural and functional network involved in planning, execution and control of motor functions are thought to represent the underlying pathology. We therefore studied changes of structural brain networks in 13 adult GTS patients reconstructed by diffusion tensor imaging and probabilistic tractography. Structural connectivity and network topology were characterized by graph theoretical measures and compared to 13 age-matched controls. In GTS patients, significantly reduced connectivity was detected in right hemispheric networks. These were furthermore characterized by significantly reduced local graph parameters (local clustering, efficiency and strength) indicating decreased structural segregation of local subnetworks. Contrasting these results, whole brain and right hemispheric networks of GTS patients showed significantly increased normalized global efficiency indicating an overall increase of structural integration among distributed areas. Higher global efficiency was associated with tic severity (R = 0.63, p = 0.022) suggesting the clinical relevance of altered network topology. Our findings reflect an imbalance between structural integration and segregation in right hemispheric structural connectome of patients with GTS. These changes might be related to an underlying pathology of impaired neuronal development, but could also indicate potential adaptive plasticity.

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.

Altered Spontaneous Brain Activity in Children with Early Tourette Syndrome: a Resting-state fMRI Study

Tourette syndrome (TS) is a childhood-onset chronic disorder characterized by the presence of multiple motor and vocal tics. This study investigated the alterations of spontaneous brain activities in children with TS by resting-state functional magnetic resonance imaging (rs-fMRI). We obtained rs-fMRI scans from 21 drug-naïve and pure TS children and 29 demographically matched healthy children. The amplitude of low-frequency fluctuation (ALFF), fractional ALFF (fALFF) and regional homogeneity (ReHo) of rs-fMRI data were calculated to measure spontaneous brain activity. We found significant alterations of ALFF or fALFF in vision-related structures including the calcarine sulcus, the cuneus, the fusiform gyrus, and the left insula in TS children. Decreased ReHo was found in the right cerebellum. Further analysis showed that the ReHo value of the right cerebellum was positively correlated with TS duration. Our study provides empirical evidence for abnormal spontaneous neuronal activity in TS patients, which may implicate the neurophysiological mechanism in TS children. Moreover, the right cerebellum can be potentially used as a biomarker for the pathophysiology of early TS in children.

Preparatory Engagement of Cognitive Control Networks Increases Late in Childhood

The ability to engage task control flexibly, especially in anticipation of task demands, is beneficial when juggling different tasks. We investigated whether children in late childhood or early adolescence engaged preparatory task control similar to adults in a trial-wise cued task-switching paradigm. Twenty-eight children (aged 9-15 years) and 30 adults (aged 21-30 years) participated in an fMRI study in which the Cue (preparatory) period across 2 tasks was analyzed separately from the execution of the tasks (the Target period). Children performed more slowly and less accurately than adults, and showed behavioral improvement within the child group age range of 9-15 years. Children exhibited weaker Cue period activation than adults within a number of putative cognitive control regions. In contrast, children exhibited greater activity than adults in several regions, including sensorimotor areas, during the Target period. Children who activated cognitive control-related regions more during the Cue period tended to activate the Target signal age-related regions less, and this correlated with improved accuracy and reaction time on the task, as well as age. The results endorse previous findings that preparatory cognitive control systems are still developing in late childhood, but add new evidence of age-related shifts in activity at the trial level.

The anarchic brain in action: the contribution of task-based fMRI studies to the understanding of Gilles de la Tourette syndrome

PURPOSE OF REVIEW

Gilles de la Tourette syndrome (GTS) is a frequent neurological disorder characterized by the production of tics, and frequently associated with obsessive-compulsive disorder or attention-deficit hyperactivity disorder. The aim of this article is to summarize the contribution of imaging activation techniques to the study of the syndrome.

RECENT FINDINGS

GTS has been studied with a variety of functional MRI (fMRI)/PET activation paradigms to characterize the origin of tics or their suppression, and how they compare physiologically with voluntary actions or response inhibitions. Current studies indicate overactivations of prefrontal and premotor cortices, including the supplementary motor area, and subcortical structures. Resting state functional connectivity studies complement activation studies in showing perturbed connectivity of cortico-subcortical networks. Several such findings correlate with the severity of the disease.

SUMMARY

fMRI activation techniques are contributing a system-level neurophysiological description of GTS and bridge the gap between animal models and clinical observations. fMRI clarifies brain networks involved in different aspects of GTS phenomenology with some good clinical face validity. A future generation of fMRI studies should have higher ambitions and contribute, for example, to treatment optimization including the identification of ideal targets for deep brain stimulation in drug-resistant cases; however, such goals will be achieved only through controlled large-scale cooperative studies.

Neuroimaging of tic genesis: Present status and future perspectives

Tics are hyperkinetic movements that are distinctive by their variety in semiology and duration and by their ability to be modulated by cognitive control. They are the hallmark of Gilles de la Tourette syndrome. Despite the variety of clinical presentations in this syndrome, dysfunction of cortico-striato-pallido-thalamo-cortical networks is suggested as a core pathophysiological mechanism. We review recent structural and functional neuroimaging studies that focused on the anatomical substrate of tics and their possible genesis. These studies showed a consistent relationship between structural and functional abnormalities within motor cortico-basal ganglia circuits and occurrence of tics. The failure of top-down cortical control over motor pathways because of the atypical trajectory of brain development could be a possible mechanism of tic genesis. Occurrence of tics results in several adaptive mechanisms, including modification of cortico-striatal network activity (reduced functional activation of the primary motor cortex) and neurochemical (increased γ-aminobutyric acid concentrations in the supplementary motor area) and microstructural white matter pathways rearrangements.

The Fallacy of Univariate Solutions to Complex Systems Problems

Complex biological systems, by definition, are composed of multiple components that interact non-linearly. The human brain constitutes, arguably, the most complex biological system known. Yet most investigation of the brain and its function is carried out using assumptions appropriate for simple systems—univariate design and linear statistical approaches. This heuristic must change before we can hope to discover and test interventions to improve the lives of individuals with complex disorders of brain development and function. Indeed, a movement away from simplistic models of biological systems will benefit essentially all domains of biology and medicine. The present brief essay lays the foundation for this argument.

Considerations for MRI study design and implementation in pediatric and clinical populations

Human neuroimaging, specifically magnetic resonance imaging (MRI), is being used with increasing popularity to study brain structure and function in development and disease. When applying these methods to developmental and clinical populations, careful consideration must be taken with regard to study design and implementation. In this article, we discuss two major considerations particularly pertinent to brain research in special populations. First, we discuss considerations for subject selection and characterization, including issues related to comorbid conditions, medication status, and clinical assessment. Second, we discuss methods and considerations for acquisition of adequate, useable MRI data. Given that children and patients may experience anxiety with the scanner environment, preventing participation, and that they have a higher risk of motion artifact, resulting in data loss, successful subject compliance and data acquisition are not trivial tasks. We conclude that, as researchers, we must consider a number of issues when using neuroimaging tools to study children and patients, and we should thoughtfully justify our choices of methods and study design.

Neural correlates of altered sensorimotor gating in boys with Tourette Syndrome: A combined EMG/fMRI study

OBJECTIVES

It has been hypothesised that altered sensorimotor gating might be a core problem in Tourette Syndrome (TS). However, the underlying neurophysiological mechanisms are elusive.

METHODS

We applied functional magnetic resonance imaging (fMRI) to investigate the neural correlates of altered sensorimotor gating by means of prepulse inhibition (PPI) in 22 boys with TS and 22 healthy boys using tactile PPI. The electromyography of the startle response was recorded simultaneously to the acquisition of the fMRI images.

RESULTS

As expected, PPI of the startle response was reduced in boys with TS compared to the healthy boys. We found decreased PPI-related blood oxygen level-dependent (BOLD) activity in boys with TS in the middle frontal gyrus, postcentral gyrus, superior parietal cortex, cingulate gyrus and caudate body. In boys with TS PPI of the startle response was positively correlated to PPI-related BOLD activity in the superior parietal cortex.

CONCLUSIONS

Our findings indicate that deficient sensorimotor gating in boys with TS is associated with reduced recruitment of brain regions responsible for the higher-order integration of somatosensory stimuli. Due to our strict sample selection we were able to reduce confounding by neural adaptation processes, long-term medication, gender or comorbidities.

Multivariate pattern classification of pediatric Tourette syndrome using functional connectivity MRI

Tourette syndrome (TS) is a developmental neuropsychiatric disorder characterized by motor and vocal tics. Individuals with TS would benefit greatly from advances in prediction of symptom timecourse and treatment effectiveness. As a first step, we applied a multivariate method – support vector machine (SVM) classification – to test whether patterns in brain network activity, measured with resting state functional connectivity (RSFC) MRI, could predict diagnostic group membership for individuals. RSFC data from 42 children with TS (8–15 yrs) and 42 unaffected controls (age, IQ, in‐scanner movement matched) were included. While univariate tests identified no significant group differences, SVM classified group membership with ~70% accuracy (p < .001). We also report a novel adaptation of SVM binary classification that, in addition to an overall accuracy rate for the SVM, provides a confidence measure for the accurate classification of each individual. Our results support the contention that multivariate methods can better capture the complexity of some brain disorders, and hold promise for predicting prognosis and treatment outcome for individuals with TS.

Spatial and temporal characteristics of error-related activity in the human brain

A number of studies have focused on the role of specific brain regions, such as the dorsal anterior cingulate cortex during trials on which participants make errors, whereas others have implicated a host of more widely distributed regions in the human brain. Previous work has proposed that there are multiple cognitive control networks, raising the question of whether error-related activity can be found in each of these networks. Thus, to examine error-related activity broadly, we conducted a meta-analysis consisting of 12 tasks that included both error and correct trials. These tasks varied by stimulus input (visual, auditory), response output (button press, speech), stimulus category (words, pictures), and task type (e.g., recognition memory, mental rotation). We identified 41 brain regions that showed a differential fMRI BOLD response to error and correct trials across a majority of tasks. These regions displayed three unique response profiles: (1) fast, (2) prolonged, and (3) a delayed response to errors, as well as a more canonical response to correct trials. These regions were found mostly in several control networks, each network predominantly displaying one response profile. The one exception to this "one network, one response profile" observation is the frontoparietal network, which showed prolonged response profiles (all in the right hemisphere), and fast profiles (all but one in the left hemisphere). We suggest that, in the place of a single localized error mechanism, these findings point to a large-scale set of error-related regions across multiple systems that likely subserve different functions.

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.

Reward enhances tic suppression in children within months of tic disorder onset

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We examine a common, yet rarely studied, population: children with recent-onset tics.

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The ability to suppress tics is present within months of tic onset.

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Immediate, contingent reward enhances these children's ability to suppress tics.

Tic disorders are childhood onset neuropsychiatric disorders characterized by motor and/or vocal tics. Research has demonstrated that children with chronic tics (including Tourette syndrome and Chronic Tic Disorder: TS/CTD) can suppress tics, particularly when an immediate, contingent reward is given for successful tic suppression. As a diagnosis of TS/CTD requires tics to be present for at least one year, children in these tic suppression studies had been living with tics for quite some time. Thus, it is unclear whether the ability to inhibit tics is learned over time or present at tic onset. Resolving that issue would inform theories of how tics develop and how behavior therapy for tics works. We investigated tic suppression in school-age children as close to the time of tic onset as possible, and no later than six months after onset. Children were asked to suppress their tics both in the presence and absence of a contingent reward. Results demonstrated that these children, like children with TS/CTD, have some capacity to suppress tics, and that immediate reward enhances that capacity. These findings demonstrate that the modulating effect of reward on inhibitory control of tics is present within months of tic onset, before tics have become chronic.

The NKI-Rockland Sample: A Model for Accelerating the Pace of Discovery Science in Psychiatry

The National Institute of Mental Health strategic plan for advancing psychiatric neuroscience calls for an acceleration of discovery and the delineation of developmental trajectories for risk and resilience across the lifespan. To attain these objectives, sufficiently powered datasets with broad and deep phenotypic characterization, state-of-the-art neuroimaging, and genetic samples must be generated and made openly available to the scientific community. The enhanced Nathan Kline Institute-Rockland Sample (NKI-RS) is a response to this need. NKI-RS is an ongoing, institutionally centered endeavor aimed at creating a large-scale (N > 1000), deeply phenotyped, community-ascertained, lifespan sample (ages 6-85 years old) with advanced neuroimaging and genetics. These data will be publically shared, openly, and prospectively (i.e., on a weekly basis). Herein, we describe the conceptual basis of the NKI-RS, including study design, sampling considerations, and steps to synchronize phenotypic and neuroimaging assessment. Additionally, we describe our process for sharing the data with the scientific community while protecting participant confidentiality, maintaining an adequate database, and certifying data integrity. The pilot phase of the NKI-RS, including challenges in recruiting, characterizing, imaging, and sharing data, is discussed while also explaining how this experience informed the final design of the enhanced NKI-RS. It is our hope that familiarity with the conceptual underpinnings of the enhanced NKI-RS will facilitate harmonization with future data collection efforts aimed at advancing psychiatric neuroscience and nosology.

The mixed block/event-related design

Neuroimaging studies began using block design and event-related design experiments. While providing many insights into brain functions, these fMRI design types ignore components of the BOLD signal that can teach us additional elements. The development of the mixed block/event-related fMRI design allowed for a fuller characterization of nonlinear and time-sensitive neuronal responses: for example, the interaction between block and event related factors and the simultaneous extraction of transient activity related to trials and block transitions and sustained activity related to task-level processing. This review traces the origins of the mixed block/event-related design from conceptual precursors to a seminal paper and on to subsequent studies using the method. The review also comments on aspects of the experimental design that must be considered when attempting to use the mixed block/event-related design. When taking into account these considerations, the mixed block/event-related design allows fuller utilization of the BOLD signal allowing deeper interpretation of how regions of the brain function on multiple timescales.

Dimensional brain-behavior relationships in children with attention-deficit/hyperactivity disorder

BACKGROUND

Emerging neuroscientific and genetic findings emphasize the dimensional rather than the categorical aspects of psychiatric disorders. However, the integration of dimensional approaches within the current categorical diagnostic framework remains unclear. Here, we used resting state functional magnetic resonance imaging to examine whether dimensional measures of psychiatric symptomatology capture brain-behavior relationships unaccounted for by categorical diagnoses. Additionally, we examined whether dimensional brain-behavior relationships are modified by the presence of a categorically defined illness, attention-deficit/hyperactivity disorder (ADHD).

METHODS

Resting state functional magnetic resonance imaging scans were collected from 37 typically developing children (aged 10.2 ± 2; 21 female subjects) and 37 children meeting DSM-IV Text Revision criteria for ADHD (9.7 ± 2; 11 female subjects). Parent-rated Child Behavior Checklist Externalizing and Internalizing scores served as dimensional measures in our analyses of default network (DN) resting state functional connectivity (RSFC).

RESULTS

Regardless of diagnosis, we observed several significant relationships between DN RSFC and both internalizing and externalizing scores. Increased internalizing scores were associated with stronger positive intra-DN RSFC, while increased externalizing scores were associated with reduced negative RSFC between DN and task-positive regions such as dorsal anterior cingulate cortex. Several of these brain-behavior relationships differed depending on the categorical presence of ADHD.

CONCLUSIONS

Our findings suggest that while categorical diagnostic boundaries provide an inadequate basis for understanding the pathophysiology of psychiatric disorders, psychiatric illness cannot be viewed simply as an extreme of typical neural or behavioral function. Efforts to understand the neural underpinnings of psychiatric illness should incorporate both categorical and dimensional clinical assessments.

Insights for treatment in Tourette syndrome from fMRI

In a recent American Journal of Psychiatry article, Wang and colleagues used functional MRI (fMRI) to examine cortico-striatal-thalamo-cortical circuitry in Tourette syndrome (TS), advancing the field's investigation of circuit level dysfunction in vivo in individuals with TS. Their results provide insight for interrogating neural mechanisms underlying different treatment methods.

Neurobiology of tourette syndrome: current status and need for further investigation

Tourette syndrome (TS) is a common, chronic neuropsychiatric disorder characterized by the presence of fluctuating motor and phonic tics. The typical age of onset is ∼5-7 years, and the majority of children improve by their late teens or early adulthood. Affected individuals are at increased risk for the development of various comorbid conditions, such as obsessive-compulsive disorder, attention deficit hyperactivity disorder, school problems, depression, and anxiety. There is no cure for tics, and symptomatic therapy includes behavioral and pharmacological approaches. Evidence supports TS being an inherited disorder; however, the precise genetic abnormality remains unknown. Pathologic involvement of cortico-striatal-thalamo-cortical (CSTC) pathways is supported by neurophysiological, brain imaging, and postmortem studies, but results are often confounded by small numbers, age differences, severity of symptoms, comorbidity, use of pharmacotherapy, and other factors. The primary site of abnormality remains controversial. Although numerous neurotransmitters participate in the transmission of messages through CSTC circuits, a dopaminergic dysfunction is considered a leading candidate. Several animal models have been used to study behaviors similar to tics as well as to pursue potential pathophysiological deficits. TS is a complex disorder with features overlapping a variety of scientific fields. Despite description of this syndrome in the late 19th century, there remain numerous unanswered neurobiological questions.

Development of the brain's functional network architecture

A full understanding of the development of the brain's functional network architecture requires not only an understanding of developmental changes in neural processing in individual brain regions but also an understanding of changes in inter-regional interactions. Resting state functional connectivity MRI (rs-fcMRI) is increasingly being used to study functional interactions between brain regions in both adults and children. We briefly review methods used to study functional interactions and networks with rs-fcMRI and how these methods have been used to define developmental changes in network functional connectivity. The developmental rs-fcMRI studies to date have found two general properties. First, regional interactions change from being predominately anatomically local in children to interactions spanning longer cortical distances in young adults. Second, this developmental change in functional connectivity occurs, in general, via mechanisms of segregation of local regions and integration of distant regions into disparate subnetworks.

Altered amygdala functional connectivity in adult Tourette's syndrome

Tourette's syndrome (TS) is a developmental neuropsychiatric disorder characterized by motor and vocal tics as well as psychiatric comorbidities. Recently, differences in maturation of cortical networks using functional connectivity metrics have been described for this disorder. However, adult data on subcortical networks are scarce. In particular, the connectivity of the amygdala, for which a role in the pathophysiology of TS has been established, has not been examined so far. We studied 15 adult TS patients (11 male, aged 30.4 ± 9.7y) and 15 age- and sex-matched controls (11 male, aged 32.0 ± 9.3y) in a functional magnetic resonance imaging study at 1.5T using a simple motor task. We corrected for possible confounds introduced by tics, motion and brain-structural differences as well as age, sex, and medication. Task performance was monitored by simultaneous MR-compatible video-recording. Data were analyzed using an independent component approach sensitive to functional connectivity patterns. A stable component comprising both amygdalae could be identified across all subjects. Additionally, we observed a highly significant increase in coupling between/within amygdalae in the TS group when compared to controls, although behavioral data obtained during scanning did not show significant differences. These findings are expected to add to our understanding of the functional architecture of Tourette's syndrome.

The genetics of obsessive-compulsive disorder and Tourette syndrome: an epidemiological and pathway-based approach for gene discovery

OBJECTIVE

To provide a contemporary perspective on genetic discovery methods applied to obsessive-compulsive disorder (OCD) and Tourette syndrome (TS).

METHOD

A review of research trends in genetics research in OCD and TS is conducted, with emphasis on novel approaches.

RESULTS

Genome-wide association studies (GWAS) are now in progress in OCD and TS and will provide a platform for future discovery of common gene variants. Optimally, newer next-generation genome sequencing methods can also be used to detect larger effect genes (rare gene variants), taking advantage of pedigrees. Studies of gene networks or sets rather than individual genes will be required to elucidate biological etiology, as neural systems appear to act redundantly. Newer phenotyping strategies, such as symptom-based subtypes, cross-disorder latent class types, and intermediate phenotypes (endophenotypes) will need to be developed and tested to better align clinical and physiological measures with genetic architecture.

CONCLUSION

Although genetics research has made significant advances based on computational strength and bioinformatics advances, newer approaches to phenotyping and judicious study of gene etiological networks will be needed to uncover the genetic etiology of OCD and TS.

Methodological approaches in developmental neuroimaging studies

Pediatric neuroimaging is increasingly providing insights into the neural basis of cognitive development. Indeed, we have now arrived at a stage where we can begin to identify optimal methodological and statistical approaches to the acquisition and analysis of developmental imaging data. In this article, we describe a number of these approaches and how their selection impacts the ability to examine and interpret developmental effects. We describe preferred approaches to task selection, definition of age groups, selection of fMRI designs, definition of regions of interest (ROI), optimal baseline measures, and treatment of timecourse data. Consideration of these aspects of developmental neuroimaging reveals that unlike single-group neuroimaging studies, developmental studies pose unique challenges that impact study planning, task design, data analysis, and the interpretation of findings.