Enhanced cognitive control in Tourette Syndrome during task uncertainty

Alterations in the topological organization of the default-mode network in Tourette syndrome

BACKGROUND

The exact pathophysiology of TS is still elusive. Previous studies have identified default mode networks (DMN) abnormalities in patients with TS. However, these literatures investigated the neural activity during the tic suppression, not a true resting-state. Therefore, this study aimed to reveal the neural mechanism of Tourette's syndrome (TS) from the perspective of topological organization and functional connectivity within the DMN by electroencephalography (EEG) in resting-state.

METHODS

The study was conducted by analyzing the EEG data of TS patients with graph theory approaches. Thirty children with TS and thirty healthy controls (HCs) were recruited, and all subjects underwent resting-state EEG data acquisition. Functional connectivity within the DMN was calculated, and network properties were measured.

RESULTS

A significantly lower connectivity in the neural activity of the TS patients in the β band was found between the bilateral posterior cingulate cortex/retrosplenial cortex (t = -3.02, p < 0.05). Compared to HCs, the TS patients' local topological properties (degree centrality) in the left temporal lobe in the γ band were changed, while the global topological properties (global efficiency and local efficiency) in DMN exhibited no significant differences. It was also demonstrated that the degree centrality of the left temporal lobe in the γ band was positively related to the Yale Global Tic Severity Scale scores (r = 0.369, p = 0.045).

CONCLUSIONS

The functional connectivity and topological properties of the DMN of TS patients were disrupted, and abnormal DMN topological property alterations might affect the severity of tic in TS patients. The abnormal topological properties of the DMN in TS patients may be due to abnormal functional connectivity alterations. The findings provide novel insight into the neural mechanism of TS patients.

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

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

Inhibitory control and impulsive responses in neurodevelopmental disorders

The impairment of inhibitory control is often assumed to be the core deficit of several neurodevelopmental disorders characterized by poor impulse control. However, could the same deficit explain different clinical phenotypes? Evidence from behavioural studies is very mixed. This is partly because inhibition is a highly complex executive function. Thus, the different types of tasks that generically tap into inhibitory control are likely to provide different outcomes. Additionally, sample inhomogeneity in terms of age, comorbidity, and medical treatment are confounding factors. Therefore, to make a reliable assessment of the deficit of inhibitory control in a given disorder, the same task and samples with similar characteristics must be employed. This article reviews and discusses studies on five neurodevelopmental disorders with impaired impulse control where these criteria have been used: Tourette syndrome; obsessive-compulsive disorder; attention-deficit/hyperactivity disorder; primary motor stereotypies; and autism spectrum disorder. Overall, they suggest that the mechanisms underlying the inability to control urges are extremely heterogeneous and cannot be ascribed to a general impairment of inhibition. These findings do not support the hypothesis that inhibitory deficits represent a transdiagnostic feature of neurodevelopmental disorders with poor impulse control. WHAT THIS PAPER ADDS: The mechanisms underlying the inability to control urges in neurodevelopmental disorders are heterogeneous. Inhibition impairments cannot generally explain all neurodevelopmental disorders characterized by poor urge control.

Inhibitory Control on a Stop Signal Task in Tourette Syndrome before and after Deep Brain Stimulation of the Internal Segment of the Globus Pallidus

As part of the first randomized double-blind trial of deep brain stimulation (DBS) of the globus pallidus (GPi) in Tourette syndrome, we examined the effect of stimulation on response initiation and inhibition. A total of 14 patients with severe Tourette syndrome were recruited and tested on the stop signal task prior to and after GPi-DBS surgery and compared to eight age-matched healthy controls. Tics were significantly improved following GPi-DBS. The main measure of reactive inhibition, the stop signal reaction time did not change from before to after surgery and did not differ from that of healthy controls either before or after GPi-DBS surgery. This suggests that patients with Tourette syndrome have normal reactive inhibition which is not significantly altered by GPi-DBS.

Correlates and clinical implications of tic suppressibility

Purpose of review

Tic disorders are common in the pediatric population and are differentiated from other movement disorders by tic suppressibility. Understanding the mechanism of tic suppression may provide new insights to the pathophysiology of tic disorders. This article highlights clinical phenomenology and neuronal correlates of tic suppressibility.

Recent findings

Recent studies suggest that tic suppressibility exists in children shortly after onset of their tics. Moreover, those who are better able to suppress their tics have better tic outcomes. Interoceptive awareness and automatic action inhibition may be involved in tic suppression.

Summary

We illustrate a possible underlying mechanism of tic suppressibility and its clinical correlations and implications. New concepts such as interoceptive awareness and action inhibition may help explain tic disorders. Further study will be useful to fill remaining knowledge gaps.

The role of the cingulate cortex in the generation of motor tics and the experience of the premonitory urge-to-tic in Tourette syndrome

Tourette syndrome (TS) is a neurological disorder of childhood onset that is characterized by the occurrence of motor and vocal tics. TS is associated with cortical-striatal-thalamic-cortical circuit [CSTC] dysfunction and hyper-excitability of cortical limbic and motor regions that are thought to lead to the occurrence of tics. Individuals with TS often report that their tics are preceded by 'premonitory sensory/urge phenomena' (PU) that are described as uncomfortable bodily sensations that precede the execution of a tic and are experienced as a strong urge for motor discharge. While the precise role played by PU in the occurrence of tics is largely unknown, they are nonetheless of considerable theoretical and clinical importance as they form a core component of many behavioural therapies used in the treatment of tic disorders. Recent evidence indicates that the cingulate cortex may play an important role in the generation of PU in TS, and in 'urges-for-action' more generally. In the current study, we utilized voxel-based morphometry (VBM) techniques, together with 'seed-to-voxel' structural covariance network (SCN) mapping, to investigate the putative role played by the cingulate cortex in the generation of motor tics and the experience of PU in a relatively large group of young people with TS. Whole-brain VBM analysis revealed that TS was associated with clusters of significantly reduced grey matter volumes bilaterally within: the orbito-frontal cortex; the cerebellum; and the anterior and mid-cingulate cortex. Similarly, analysis of SCNs associated with bilateral mid- and anterior cingulate 'seed' regions demonstrated that TS is associated with increased structural covariance primarily with the bilateral motor cerebellum; the inferior frontal cortex; and the posterior cingulate cortex.

Automatic imitation in youngsters with Gilles de la Tourette syndrome: A behavioral study

It is widely known that humans have a tendency to imitate each other and that appropriate modulation of automatic imitative behaviors has a crucial function in social interactions. Gilles de la Tourette syndrome (GTS) is a childhood-onset neuropsychiatric disorder characterized by motor and phonic tics. Apart from tics, patients with GTS are often reported to show an abnormal tendency to automatically imitate others' behaviors (i.e., echophenomena), which may be related to a failure in top-down inhibition of imitative response tendencies. The aim of the current study is to explore the top-down inhibitory mechanisms on automatic imitative behaviors in youngsters with GTS. Error rates and reaction times from 32 participants with GTS and 32 controls were collected in response to an automatic imitation task assessing the influence of observed movements displayed in the first-person perspective on congruent and incongruent motor responses. Results showed that participants with GTS had higher error rates than controls, and their responses were faster than those of controls in incompatible stimuli. Our findings provide novel evidence of a key difference between youngsters with GTS and typically developing participants in the ability to effectively control the production of own motor responses to sensory inputs deriving from observed actions.

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.

Impaired automatic but intact volitional inhibition in primary tic disorders

The defining character of tics is that they can be transiently suppressed by volitional effort of will, and at a behavioural level this has led to the concept that tics result from a failure of inhibition. However, this logic conflates the mechanism responsible for the production of tics with that used in suppressing them. Volitional inhibition of motor output could be increased to prevent the tic from reaching the threshold for expression, although this has been extensively investigated with conflicting results. Alternatively, automatic inhibition could prevent the initial excitation of the striatal tic focus-a hypothesis we have previously introduced. To reconcile these competing hypotheses, we examined different types of motor inhibition in a group of 19 patients with primary tic disorders and 15 healthy volunteers. We probed proactive and reactive inhibition using the conditional stop-signal task, and applied transcranial magnetic stimulation to the motor cortex, to assess movement preparation and execution. We assessed automatic motor inhibition with the masked priming task. We found that volitional movement preparation, execution and inhibition (proactive and reactive) were not impaired in tic disorders. We speculate that these mechanisms are recruited during volitional tic suppression, and that they prevent expression of the tic by inhibiting the nascent excitation released by the tic generator. In contrast, automatic inhibition was abnormal/impaired in patients with tic disorders. In the masked priming task, positive and negative compatibility effects were found for healthy controls, whereas patients with tics exhibited strong positive compatibility effects, but no negative compatibility effect indicative of impaired automatic inhibition. Patients also made more errors on the masked priming task than healthy control subjects and the types of errors were consistent with impaired automatic inhibition. Errors associated with impaired automatic inhibition were positively correlated with tic severity. We conclude that voluntary movement preparation/generation and volitional inhibition are normal in tic disorders, whereas automatic inhibition is impaired-a deficit that correlated with tic severity and thus may constitute a potential mechanism by which tics are generated.

Tic frequency and behavioural measures of cognitive control are improved in individuals with Tourette syndrome by aerobic exercise training

Previous observations of improvements in cognition in typically developing children following moderate to vigorous exercise (e.g., Budde, Voelcker-Rehage, Pietrabyk-Kendziorra, Ribeiro, & Tidow, 2008; Hillman et al., 2009) have led to increased interest in the potential benefits of exercise for children with neurodevelopmental disorders, involving difficulties in self-regulation (e.g., Halperin & Healey, 2011; Archer & Kostrzewa, 2012). Using a within-sample design, the current study looked at the beneficial effects of non-aerobic movement training (Tai Chi), compared to aerobic movement training (Kick Boxing), on behavioural measures of cognitive control and clinical measures of tic severity in a group of young people with Tourette Syndrome (TS). We demonstrate that Kick Boxing, but not Tai Chi, led to a significant enhancement in cognitive control task performance. Furthermore, while tic frequency (tics per minute) was reduced during both types of exercise, this reduction was significantly greater, and sustained for longer, following Kick Boxing. Importantly, the magnitude of the increase in cognitive control following Kick Boxing predicted the degree of reduction in tic frequency. These findings suggest that aerobic exercise may be a useful intervention for improving self-regulation of tics in young people with TS, probably through enhancements in associated cognitive control circuits.

Loss in grey matter in a small network of brain areas underpins poor reactive inhibition in Obsessive-Compulsive Disorder patients

Reactive inhibition correlates with the severity of symptoms in paediatric patients with Obsessive-Compulsive Disorder (OCD) though not in those with Tourette syndrome (TS). Here we assessed whether structural alterations in both grey (GM) and white matter (WM) volumes correlate with a measure of reactive inhibition, i.e. the stop-signal reaction time (SSRT), and with clinical scale scores. Nine OCD and 11 TS uncomplicated drug-naïve paediatric patients and 12 age-matched controls underwent 3T magnetic resonance imaging scanning. Between-group differences in GM and WM volumes across the whole brain were assessed. Outside the scanner, patients performed a reaching version of the stop-signal task. Both behavioural inhibitory control and neuroimaging measures were normal in TS patients. By contrast, OCD patients exhibited a significant loss in GM volume in five areas. The GM volume of the left inferior frontal gyrus was inversely correlated with the length of the SSRT, the left mid-cingulate gyrus and the right middle frontal gyrus were inversely correlated with the severity of OCD symptoms, and the left insula and the right medial orbitofrontal gyrus were inversely correlated with both. These results indicate that cortical areas showing GM loss in OCD patients are also involved in the network subserving reactive inhibition.

Intact automatic motor inhibition in patients with tourette syndrome

BACKGROUND

Behavioral disinhibition has been proposed as a key mechanism in Tourette syndrome. Yet classic inhibition tasks have yielded inconsistent results, likely reflecting interference by strategies compensating for tic release.

METHODS

We examined a core inhibitory function that is immune to such interference because it suppresses movements automatically. We measured automatic motor inhibition behaviorally in 21 adults with Tourette syndrome and 21 healthy controls via the negative compatibility effect. When a motor response is activated, for example, by a subliminal prime stimulus, but execution is delayed, activation turns into inhibition, increasing reaction time and error. Diminished automatic inhibition could underlie tic release.

RESULTS

Both controls and patients showed strong automatic motor inhibition with no significant group difference. Bayesian statistics, allowing inference on the absence of effects, favored intact inhibition in patients. Our study was well powered.

CONCLUSIONS

Automatic motor inhibition in Tourette syndrome is neither impaired nor harnessed by compensation. © 2018 International Parkinson and Movement Disorder Society.

A superior ability to suppress fast inappropriate responses in children with Tourette syndrome is further improved by prospect of reward

In children with Tourette syndrome (TS), tics are often attributed to deficient self-control by health-care professionals, parents, and peers. In this behavioural study, we examined response inhibition in TS using a modified Simon task which probes the ability to solve the response conflict between a new non-spatial rule and a highly-overlearned spatial stimulus-response mapping rule. We applied a distributional analysis to the behavioural data, which grouped the trials according to the individual distribution of reaction times in four time bins. Distributional analyses enabled us to probe the children's ability to control fast, impulsive, responses, which corresponded to the trials in the fastest time bin. Additionally, we tested whether the ability to suppress inappropriate action tendencies can be improved further by the prospect of a reward. Forty-one clinically well-characterized medication-naïve children with TS, 20 children with attention-deficit/hyperactivity disorder (ADHD), and 43 typically developing children performed a Simon task during alternating epochs with and without a prospect of reward. We applied repeated measures ANCOVAs to estimate how the prospect of reward modulated reaction times and response accuracy, while taking into account the distribution of the reaction times across trials. We found between-group differences in accuracy when subjects responded relatively fast. The TS group responded more accurately than typically developing control children when resolving the response conflict introduced by the Simon task. The opposite pattern was found in children with ADHD. Prospect of reward improved accuracy rates in all groups. Although the Tourette group performed with superior accuracy in the fast trials, it was still possible for them to benefit from prospect of reward in fast trials. The findings corroborate the notion that children with TS have an enhanced capacity to inhibit fast inappropriate response tendencies. This ability can be improved further by offering a prospect of reward which might be useful during non-pharmacological therapeutic interventions.

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.

Effects of rule uncertainty on cognitive flexibility in a card-sorting paradigm

Cognitive flexibility has been studied in two separate research traditions. Neuropsychologists typically rely on rather complex assessment tools such as the Wisconsin Card Sorting Test (WCST). In contrast, task-switching paradigms are used in experimental psychology to obtain more specific measures of cognitive flexibility. We aim to contribute to the integration of these research traditions by examining the role of the key factor that differs between the WCST and experimental task-switching paradigms: rule uncertainty. In two experimental studies, we manipulated the degree of rule uncertainty after rule switches in a computerized version of the WCST. Across a variety of task parameters, reducing rule uncertainty consistently impaired the speed and accuracy of responses when the rule designated to be more likely turned out to be incorrect. Other performance measures such as the number of perseverative errors were not significantly affected by rule uncertainty. We conclude that a fine-grained analysis of WCST performance can dissociate behavioural indicators that are affected vs. unaffected by rule uncertainty. By this means, it is possible to integrate WCST results and findings obtained from task-switching paradigms that do not involve rule uncertainty.

Altered Functional Connectivity in Resting State Networks in Tourette's Disorder

Introduction: Brain regions are anatomically and functionally interconnected in order to facilitate important functions like cognition and movement. It remains incompletely understood how brain connectivity contributes to the pathophysiology of Tourette's disorder (TD). By using resting-state functional MRI, we aimed to identify alterations in the default mode network (DMN), frontal-parietal network (FPN), sensori-motor network (SMN), and salience network (SN) in TD compared with healthy control (HC) subjects. Method: In 23 adult TD patients and 22 HC, 3T-MRI resting-state scans were obtained. Independent component analysis was performed comparing TD and HC to investigate connectivity patterns within and between resting-state networks. Results: TD patients showed higher involvement of the dorsal medial prefrontal cortex in the connectivity of the DMN and less involvement of the inferior parietal cortex in the connectivity of the FPN when compared to HC. Moreover, TD patients showed a stronger coupling between DMN and left FPN than HC. Finally, in TD patients, functional connectivity within DMN correlated negatively with tic severity. Conclusion: We tentatively interpret the increased functional connectivity within DMN in TD patients as compensatory to the lower functional connectivity within left FPN. The stronger coupling between DMN and left FPN, together with the finding that higher DMN intrinsic connectivity is associated with lower tic severity would indicate that DMN is recruited to exert motor inhibition.

Executive control development in Tourette syndrome and its role in tic reduction

Tourette syndrome (TS) is a childhood-onset disorder characterized by motor and vocal tics. Recent findings point to a possible role of executive functions system development in the tic reduction observed with age. The goal of the present work was to track the development of executive functions system measured by well-established cognitive tasks and its correlation with diminished tic severity over time in order to understand the role of executive functions in the remission process observed in most adults. The first study followed 25 young TS patients, measuring their executive functions and clinical condition at three time- points. In the second study we compared executive functions performance of 19 adult TS patients with 19 healthy controls and 12 remitted TS patients. The first study showed that tic reduction is related to the development of the executive functions components associated with response inhibition. The second study similarly showed impaired inhibition ability in TS patients but not in controls or the remitted TS patients. The remitted group performed at normal or even higher levels on certain measures. We conclude that inhibition, an important executive function, is impaired in subjects suffering from TS and that intact executive function development is related to remission processes.

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.

Evidence for enhanced multi-component behaviour in Tourette syndrome - an EEG study

Evidence suggests that Tourette syndrome is characterized by an increase in dopamine transmission and structural as well as functional changes in fronto-striatal circuits that might lead to enhanced multi-component behaviour integration. Behavioural and neurophysiological data regarding multi-component behaviour was collected from 15 patients with Tourette syndrome (mean age = 30.40 ± 11.10) and 15 healthy controls (27.07 ± 5.44), using the stop-change task. In this task, participants are asked to sometimes withhold responses to a Go stimulus (stop cue) and change hands to respond to an alternative Go stimulus (change cue). Different onset asynchronies between stop and change cues were implemented (0 and 300 ms) in order to vary task difficulty. Tourette patients responded more accurately than healthy controls when there was no delay between stop and change stimulus, while there was no difference in the 300 ms delay condition. This performance advantage was reflected in a smaller P3 event related potential. Enhanced multi-component behaviour in Tourette syndrome is likely based on an enhanced ability to integrate information from multiple sources and translate it into an appropriate response sequence. This may be a consequence of chronic tic control in these patients, or a known fronto-striatal networks hyperconnectivity in Tourette syndrome.

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.

Specific executive control impairments in Tourette syndrome: The role of response inhibition

BACKGROUND

Tourette syndrome (TS) is a childhood-onset disorder characterized by motor and vocal tics. While cognitive features of common comorbid conditions such as attention deficit hyperactive disorder and obsessive compulsive disorder have been widely investigated, the cognitive profile of TS patients remains to be precisely defined. In this regard, the executive functions system (EF) is of especial interest.

AIMS

The aim of the study was to delineate the various components of executive processes in adult TS patients.

METHODS

A sample of 19 adults diagnosed with TS and 19 age-matched control subjects underwent computerized battery of executive tasks, as well as block design and memory tests. All patients received a thorough clinical assessment with an emphasis on illness severity.

RESULTS

There was a marked impairment in response inhibition ability regardless of comorbid conditions, In addition, there was decreased accuracy in set shifting, but not in response time. These results imply that impaired response inhibition in the EF system is the primary cognitive impairment in TS and that many of the previously reported impaired executive functions in TS are secondary to this impairment.

CONCLUSIONS

This finding of impaired response inhibition in TS may imply that rehabilitation of this inhibition component could prove to be an important therapeutic strategy in adults with TS.

Tourette syndrome in the context of evolution and behavioral ecology

Tourette syndrome, and the closely related spectrum of tic disorders, are inherited neuropsychiatric conditions characterized by the presence of repetitive and stereotyped movements. Tics are elicited by either environmental experiences or internal signals that instruct the basal ganglia to initiate automatic or procedural movements. In most vertebrates the basal ganglia encode instructions for habitually used sequences of motor movements that are essential to survival. Tic disorders may represent evolved phenotypes with a lower threshold for basal ganglia-directed actions. This may have produced a susceptibility to extraneous tics, but also produced fast-acting tactical solutions to immediate physical problems. During periods of nonstop movement, continual foraging, and sustained vigilance, it may have been advantageous to allow subcortical motor commands to intrude into ongoing motor activities. It is clear that the engrams for individual motor responses held in the basal ganglia are selected by converging cortical and subcortical inputs. This form of convergent action selection results in the selection of the most contextually reinforced actions. Today people with Tourette's have tics that seem arbitrary and inappropriate; however, this may be due to the vast discrepancies in reinforcement between the ancestral environment and the modern one. In prehistoric environments, the motor behaviors of individuals with tic disorders may have been appropriate in environmental context, and had ecological relevance in survival and self-promotion.

Time Processing and Motor Control in Movement Disorders

The subjective representation of “time” is critical for cognitive tasks but also for several motor activities. The neural network supporting motor timing comprises: lateral cerebellum, basal ganglia, sensorimotor and prefrontal cortical areas. Basal ganglia and associated cortical areas act as a hypothetical “internal clock” that beats the rhythm when the movement is internally generated. When timing information is processed to make predictions on the outcome of a subjective or externally perceived motor act, cerebellar processing and outflow pathways appear to be primarily involved. Clinical and experimental evidence on time processing and motor control points to a dysfunction of the neural networks involving basal ganglia and cerebellum in movement disorders. In some cases, temporal processing deficits could directly contribute to core motor features of the movement disorder, as in the case of bradykinesia in Parkinson's disease. For other movement disorders, the relationship between abnormal time processing and motor performance is less obvious and requires further investigation, as in the reduced accuracy in predicting the temporal outcome of a motor act in dystonia. We aim to review the literature on time processing and motor control in Parkinson's disease, dystonia, Huntington's disease, and Tourette syndrome, integrating the available findings with current pathophysiological models; we will highlight the areas in which future explorations are warranted, as well as the aspects of time processing in motor control that present translational aspects in future rehabilitation strategies. The subjective representation of “time” is critical for cognitive tasks but also for motor activities. Recently, greater attention has been devoted to improve our understanding of how temporal information becomes integrated within the mechanisms of motor control. Experimental evidence recognizes time processing in motor control as a complex neural function supported by diffuse cerebral networks including cortical areas, cerebellum, and other subcortical structures (Ivry and Spencer, 2004; Coull and Nobre, 2008). Timing is an essential component of motor control primarily within two types of motor tasks: (i) when producing sequential rhythmic movements or sustained movements of a definite duration (explicit timing); (ii) when the temporal information is used implicitly, such as when coordinating our movements to those of moving objects or individuals within the external environment (implicit timing). In this review, we will provide a brief description of the neural network supporting motor timing focusing only on instrumental information to explain the link between timing and motor control in movement disorders. Then we will review available data on motor timing in Parkinson's disease, dystonia, Huntington's disease, and Tourette syndrome, and discuss how this body of evidence integrates with the available information on the pathophysiology of these movement disorders. Finally, we will discuss the translational aspects of the explored neural mechanisms with respect to future rehabilitation strategies.

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.

A verbal strength in children with Tourette syndrome? Evidence from a non-word repetition task

Tourette syndrome (TS) is characterized by motor and vocal tics, and frontal/basal-ganglia abnormalities. Whereas cognitive strengths have been found in other neurodevelopmental disorders, less attention has been paid to strengths in TS, or to verbal strengths in any neurodevelopmental disorder. We examined whether the finding of speeded TS production of rule-governed morphological forms (e.g., "slipped") that involve composition (Walenski, Mostofsky, & Ullman, 2007) might extend to another language domain, phonology. Thirteen children with TS and 14 typically-developing (TD) children performed a non-word repetition task: they repeated legal phonological strings (e.g.,"naichovabe"), a task that taps rule-governed (de)composition. Parallel to the morphology findings, the children with TS showed speeded production, while the two groups had similar accuracy. The results were not explained by potentially confounding factors, including IQ. Overall, the findings suggest that rule-governed grammatical composition may be speeded in TS, perhaps due to frontal/basal-ganglia abnormalities.

Atypical Sensory behaviours in children with Tourette's Syndrome and in children with Autism Spectrum Disorders

Certain visual disturbances make it difficult to read text and have been attributed to visual stress, also called "pattern-related visual stress". 12 Children with ASD, 12 children with Tourette's syndrome and without ASD and 12 controls, all matched on age and non verbal ability, participated in an experiment exploring sensory behaviours and visual stress. Reading rate and accuracy were assessed with the Wilkins Rate of Reading test with and without the Intuitive Overlays. Both the children with Tourette's and the children with ASD showed a higher prevalence of atypical sensory behaviours and symptoms of visual stress than the typically developing control children. Six out of twelve children with Tourette's syndrome (50%) read more accurately and over 15% more quickly with a coloured overlay. Four of the 12 children with ASD and none of the control children read over 15% more quickly with an overlay. The findings are discussed in relation to problems in sensory modulation.

Electrophysiological correlates of reinforcement learning in young people with Tourette syndrome with and without co-occurring ADHD symptoms

Altered reinforcement learning is implicated in the causes of Tourette syndrome (TS) and attention-deficit/hyperactivity disorder (ADHD). TS and ADHD frequently co-occur but how this affects reinforcement learning has not been investigated. We examined the ability of young people with TS (n=18), TS+ADHD (N=17), ADHD (n=13) and typically developing controls (n=20) to learn and reverse stimulus-response (S-R) associations based on positive and negative reinforcement feedback. We used a 2 (TS-yes, TS-no)×2 (ADHD-yes, ADHD-no) factorial design to assess the effects of TS, ADHD, and their interaction on behavioural (accuracy, RT) and event-related potential (stimulus-locked P3, feedback-locked P2, feedback-related negativity, FRN) indices of learning and reversing the S-R associations. TS was associated with intact learning and reversal performance and largely typical ERP amplitudes. ADHD was associated with lower accuracy during S-R learning and impaired reversal learning (significantly reduced accuracy and a trend for smaller P3 amplitude). The results indicate that co-occurring ADHD symptoms impair reversal learning in TS+ADHD. The implications of these findings for behavioural tic therapies are discussed.

WITHDRAWN: Electrophysiological correlates of reinforcement learning in young people with Tourette syndrome with and without co-occurring ADHD symptoms

The Publisher regrets that this article is an accidental duplication of an article that has already been published, http://dx.doi.org/10.1016/j.ijdevneu.2016.04.006. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.

Performance Monitoring in Medication-Naïve Children with Tourette Syndrome

Background: Tourette syndrome (TS) is a childhood-onset neurodevelopmental disorder and its impact on cognitive development needs further study. Evidence from neuropsychological, neuroimaging and electrophysiological studies suggests that the decline in tic severity and the ability to suppress tics relate to the development of self-regulatory functions in late childhood and adolescence. Hence, tasks measuring performance monitoring might provide insight into the regulation of tics in children with TS.

Method: Twenty-five children with TS, including 14 with comorbid Attention-deficit/ hyperactivity disorder (ADHD), 39 children with ADHD and 35 typically developing children aged 8–12 years were tested with a modified Eriksen-Flanker task during a 34-channel electroencephalography (EEG) recording. Task performance, as well as stimulus-locked and response-locked event-related potentials (ERP) were analyzed and compared across groups.

Results: Participants did not differ in their behavioral performance. Children with TS showed higher amplitudes of an early P3 component of the stimulus-locked ERPs in ensemble averages and in separate trial outcomes, suggesting heightened orienting and/or attention during stimulus evaluation. In response-locked averages, children with TS had a slightly higher positive complex before the motor response, likely also reflecting a late P3. Groups did not differ in post-response components, particularly in the error-related negativity (ERN) and error-related positivity (Pe).

Conclusions: These findings suggest that children with TS may employ additional attentional resources as a compensatory mechanism to maintain equal behavioral performance.

Cognition, Emotion and Behavior in Children with Tourette's Syndrome and Children with ADHD-Combined Subtype-A Two-Year Follow-Up Study

OBJECTIVE

This two-year follow-up study investigates the course of and association among measures of cognitive control, focused attention, decision-making and symptom severity (anxiety, depression and behavior) in children and adolescents with Tourette's Syndrome (TS) or Attention-Deficit/Hyperactivity Disorder-Combined subtype (ADHD-C).

METHOD

19 children with TS, 33 with ADHD-C, and 50 typically developing children (TDC) were examined with a battery of psychometric measures and rating forms at baseline and two-years later.

RESULTS

All three groups improved likewise in measures of cognitive control over time, whereas only the TDC improved in focused attention. The group of children with TS with comorbidities performed more similar to the children with ADHD-C in cognitive control at T1 and T2, whereas the children with TS without comorbidities performed more similar to the TDC in cognitive control at T1 and T2. In the decision-making task, the children with TS (with or without comorbidities) preferred a safer strategy in selecting advantageous choices than the children with ADHD-C and the TDC at T2. Children with TS and children with ADHD-C showed higher symptoms of anxiety and depression and more problems with emotional control compared with TDC at both time points. Finally, children with ADHD-C self-reported more depression symptoms than those with TS at both assessments. For the TS group, safer decision-making was related to better emotional control, and this relationship was stronger for the TS subgroup without comorbidities.

CONCLUSION

This study emphasizes the importance of addressing symptoms of anxiety and depression in children with TS or ADHD-C, identifying the effect of comorbidities in children with TS, and that children with TS or ADHD-C likely differ in their sensitivity to reinforcement contingencies.

Inhibition, Disinhibition, and the Control of Action in Tourette Syndrome

Tourette syndrome (TS) is a neurological disorder characterized by vocal and motor tics. TS is associated with impairments in behavioral inhibition, dysfunctional signaling of the inhibitory neurotransmitter GABA, and alterations in the balance of excitatory and inhibitory influences within brain networks implicated in motor learning and the selection of actions. We review evidence that increased control over motor outputs, including the suppression of tics, may develop during adolescence in TS and be accompanied by compensatory, neuromodulatory, alterations in brain structure and function. In particular, we argue that increased control over motor outputs in TS is brought about by local increases in 'tonic' inhibition that lead to a reduction in the 'gain' of motor excitability.

The effects of co-occurring ADHD symptoms on electrophysiological correlates of cognitive control in young people with Tourette syndrome

Efficient cognitive control is implicated in tic control in young people with Tourette syndrome (TS). Attention-deficit/hyperactivity disorder (ADHD) frequently co-occurs with TS and is associated with impaired cognitive control. Young people with TS and ADHD (TS+ADHD) show poorer cognitive control performance than those with TS, but how co-occurring ADHD affects underlying neural activity is unknown. We investigated this issue by examining behavioural and event-related potential (ERP) correlates of cognitive control in young people with these conditions. Participants aged 9-17 with TS (n = 17), TS+ADHD (n = 17), ADHD (n = 11), and unaffected controls (n = 20) performed a visual Go/Nogo task during electroencephalography (EEG) recording. Behavioural performance measures (D-prime, RT, reaction time variability, post-error slowing) and ERP measures (N2, P3, error-related negativity (ERN), error positivity (Pe)) were analysed in a 2 (TS-yes, TS-no) × 2 (ADHD-yes, ADHD-no) factorial analysis to investigate the effects of TS, ADHD, and their interaction. The results of these analyses showed that ADHD was associated with poorer performance and reduced amplitude of all ERPs, reflecting widespread cognitive control impairments. Tourette syndrome was associated with slowed RTs, which might reflect a compensatory slowing of motor output to facilitate tic control. There was no interaction between the TS and ADHD factors for any behavioural or ERP measure, indicating the impairing effects of ADHD on behaviour and electrophysiological markers of cognitive control were present in TS+ADHD and that RT slowing associated with TS was unaffected by co-occurring ADHD symptoms.

Timing recalibration in childhood Tourette syndrome associated with persistent pimozide treatment

In this study, we have tested the effects of the dopamine D2 receptor blocker pimozide on timing performance in patients with Tourette syndrome (TS). Nine children with TS were tested off-medication and following 3 months of daily treatment with pimozide. Subjects completed a time reproduction and a time production task using supra-second temporal intervals. We show that pimozide improves motor timing performance by reducing the patients' variability in reproducing the duration of visual stimuli. On the other hand, this medication has no effect on the reproduction accuracy and on both variability and accuracy of the performance on the time production task. Our results suggest that pimozide might have improved motor timing variability as a result of its beneficial side effect on endogenous dopamine levels (i.e., normalization).

Oculomotor executive function abnormalities with increased tic severity in Tourette syndrome

BACKGROUND

Reports conflict as to whether Tourette syndrome (TS) confers deficits in executive function. This study's aim was to evaluate executive function in youths with TS using oculomotor tasks while controlling for confounds of tic severity, age, medication, and severity of comorbid disorders.

METHOD

Four saccade tasks requiring the executive functions of response generation, response inhibition, and working memory (prosaccade, antisaccade, 0-back, and 1-back) were administered. Twenty youths with TS and low tic severity (TS-low), nineteen with TS and moderate tic severity (TS-moderate), and 29 typically developing control subjects (Controls) completed the oculomotor tasks.

RESULTS

There were small differences across groups in the prosaccade task. Controlling for any small sensorimotor differences, TS-moderate subjects had significantly higher error rates than Controls and TS-low subjects in the 0-back and 1-back tasks. In the 1-back task, these patients also took longer to respond than Controls or TS-low subjects.

CONCLUSIONS

In a highly controlled design, the findings demonstrate for the first time that increased tic severity in TS is associated with impaired response inhibition and impaired working memory and that these executive function deficits cannot be accounted for by differences in age, medication or comorbid symptom severity.

A personal 35 year perspective on Gilles de la Tourette syndrome: assessment, investigations, and management

After having examined the definition, clinical phenomenology, comorbidity, psychopathology, and phenotypes in the first paper of this Series, here I discuss the assessment, including neuropsychology, and the effects of Gilles de la Tourette syndrome with studies showing that the quality of life of patients with Tourette's syndrome is reduced and that there is a substantial burden on the family. In this paper, I review my local and collaborative studies investigating causal factors (including genetic vulnerability, prenatal and perinatal difficulties, and neuro-immunological factors). I also present my studies on neuro-imaging, electro-encephalograms, and other special investigations, which are helpful in their own right or to exclude other conditions. Finally, I also review our studies on treatment including medications, transcranial magnetic stimulation, biofeedback, target-specific botulinum toxin injections, biofeedback and, in severe refractory adults, psychosurgery and deep brain stimulation. This Review summarises and highlights selected main findings from my clinic (initially The National Hospital for Neurology and Neurosurgery Queen Square and University College London, UK, and, subsequently, at St George's Hospital, London, UK), and several collaborations since 1980. As in Part 1 of this Series, I address the main controversies in the fields and the research of other groups, and I make suggestions for future research.

Increased GABA contributes to enhanced control over motor excitability in Tourette syndrome

Tourette syndrome (TS) is a developmental neurological disorder characterized by vocal and motor tics and associated with cortical-striatal-thalamic-cortical circuit dysfunction, hyperexcitability within cortical motor areas, and altered intracortical inhibition. TS often follows a developmental time course in which tics become increasingly more controlled during adolescence in many individuals, who exhibit enhanced control over their volitional movements. Importantly, control over motor outputs appears to be brought about by a reduction in the gain of motor excitability. Here we present a neurochemical basis for a localized gain control mechanism. We used ultra-high-field (7 T) magnetic resonance spectroscopy to investigate in vivo concentrations of γ-aminobutyric acid (GABA) within primary and secondary motor areas of individuals with TS. We demonstrate that GABA concentrations within the supplementary motor area (SMA)--a region strongly associated with the genesis of motor tics in TS--are paradoxically elevated in individuals with TS and inversely related to fMRI blood oxygen level-dependent activation. By contrast, GABA concentrations in control sites do not differ from those of a matched control group. Importantly, we also show that GABA concentrations within the SMA are inversely correlated with cortical excitability in primary motor cortex and are predicted by motor tic severity and white-matter microstructure (FA) within a region of the corpus callosum that projects to the SMA within each hemisphere. Based upon these findings, we propose that extrasynaptic GABA contributes to a form of control, based upon localized tonic inhibition within the SMA, that may lead to the suppression of tics.

Tourette-like behaviors in the normal population are associated with hyperactive/impulsive ADHD-like behaviors but do not relate to deficits in conditioned inhibition or response inhibition

Attention-Deficit Hyperactivity Disorder (ADHD) and Tourette Syndrome (TS) present as distinct conditions clinically; however, comorbidity and inhibitory control deficits have been proposed for both. Whilst such deficits have been studied widely within clinical populations, findings are mixed—partly due to comorbidity and/or medication effects—and studies have rarely distinguished between subtypes of the disorders. Studies in the general population are sparse. Using a continuity approach, the present study examined (i) the relationships between inattentive and hyperactive/impulsive aspects of ADHD and TS-like behaviors in the general population, and (ii) their unique associations with automatic and executive inhibitory control, as well as (iii) yawning (a proposed behavioral model of TS). One hundred and thirty-eight participants completed self-report measures for ADHD and TS-like behaviors as well as yawning, and a conditioned inhibition task to assess automatic inhibition. A sub-sample of fifty-four participants completed three executive inhibition tasks. An exploratory factor analysis of the TS behavior checklist supported a distinction between phonic and motor like pure TS behaviors. Whilst hyperactive/impulsive aspects of ADHD were associated with increased pure and compulsive TS-like behaviors, inattention in isolation was related to reduced obsessive-compulsive TS-like behaviors. TS-like behaviors were associated with yawning during situations of inactivity, and specifically motor TS was related to yawning during stress. Phonic TS and inattention aspects of ADHD were associated with yawning during concentration/activity. Whilst executive interference control deficits were linked to hyperactive/impulsive ADHD-like behaviors, this was not the case for inattentive ADHD or TS-like behaviors, which instead related to increased performance on some measures. No associations were observed for automatic conditioned inhibition.

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 neural correlates of tic inhibition in Gilles de la Tourette syndrome

Tics in Gilles de la Tourette syndrome (GTS) resemble fragments of normal motor behaviour but appear in an intrusive, repetitive and context-inappropriate manner. Although tics can be voluntarily inhibited on demand, the neural correlates of this process remain unclear. 14 GTS adults without relevant comorbidities participated in this study. First, tic severity and voluntary tic inhibitory capacity were evaluated outside the scanner. Second, patients were examined with resting state functional magnetic resonance imaging (RS-fMRI) in two states, free ticcing and voluntary tic inhibition. Local synchronization of spontaneous fMRI-signal was analysed with regional homogeneity (ReHo) and differences between both states (free ticcing<tic inhibition) were contrasted. Clinical correlations of the resulting differential ReHo parameters between both states and clinical measures of tic frequency, voluntary tic inhibition and premonitory urges were also performed. ReHo of the left inferior frontal gyrus (IFG) was increased during voluntary tic inhibition compared to free ticcing. ReHo increases were positively correlated with participants׳ ability to inhibit their tics during scanning sessions but also outside the scanner. There was no correlation with ratings of premonitory urges. Voluntary tic inhibition is associated with increased ReHo of the left IFG. Premonitory urges are unrelated to this process.

A Comparison of Urge Intensity and the Probability of Tic Completion During Tic Freely and Tic Suppression Conditions

Tic-suppression-based treatments (TSBTs) represent a safe and effective treatment option for Chronic Tic Disorders (CTDs). Prior research has demonstrated that treatment naive youths with CTDs have the capacity to safely and effectively suppress tics for prolonged periods. It remains unclear how tic suppression is achieved. The current study principally examines how effective suppression is achieved and preliminary correlates of the ability to suppress tics. Twelve youths, ages 10 to 17 years, with moderate-to-marked CTDs participated in an alternating sequence of tic freely and reinforced tic suppression conditions during which urge intensity and tic frequency were frequently assessed. Probability of tics occurring was half as likely following high-intensity urges during tic suppression (31%) in contrast to low-intensity urges during tic freely conditions (60%). Age was not associated with ability to suppress. Intelligence indices were associated with or trended toward greater ability to suppress tics. Attention difficulties were not associated with ability to suppress but were associated with tic severity. In contrast to our "selective suppression" hypothesis, we found participants equally capable of suppressing their tics regardless of urge intensity during reinforced tic suppression. Tic suppression was achieved with an "across-the-board" effort to resist urges. Preliminary data suggest that ability to suppress may be associated with general cognitive variables rather than age, tic severity, urge severity, and attention. Treatment naive youths appear to possess a capacity for robust tic suppression. TSBTs may bolster these capacities and/or enable their broader implementation, resulting in symptom improvement.