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

[Formula: see text] Beyond the rubicon: a continuum approach to investigating the impact of ADHD like characteristics on everyday executive function in children with Tourette Syndrome

Across a range of neurodevelopmental conditions, a diagnosis of attention deficit hyperactivity disorder (ADHD) has been shown to be associated with executive function impairment. However, the DSM-V emphasis upon viewing psychological characteristics as existing on a continuous distributed quantitative dimension has enabled the opportunity to consider the influence of sub-diagnostic or sub-referral levels of these psychological characteristics upon cognitive function. This study adopted a continuum approach to the consideration of this ADHD influence and examined the extent to which the difference in parental reported executive functions between children with Tourette syndrome (TS) or typically developing children could be mediated by a concurrent group difference in the possession of sub-referral levels of ADHD-like characteristics. A total of 146 children, 58 with reported TS diagnosis, participated. Parental report measures of ecological executive functioning, the Child Executive Functioning Inventory, and the Vanderbilt ADHD Diagnostic Parent Rating Scale were employed. The analyses with a full sample and a sub-referral sample revealed significant group differences in most of the key measures. In addition, these measures were highly correlated even when controlling for age and gender. A series of mediation analyses indicated that in all models, the ADHD-like measures significantly mediated the group difference in executive function. These results suggest that sub-referrals levels of ADHD-like characteristics continue to contribute to executive challenges in TS. Future intervention research targeting these executive functions should consider the presence of ADHD-like characteristics at sub-referral levels of possession.

Group comprehensive behavioral intervention for tics contribution to broader cognitive and emotion regulation in children

There is increasing evidence for the effectiveness of behavioral techniques in managing tics in youth with Tourette syndrome and tics disorders (TDs). One such intervention is Comprehensive Behavioral Intervention for Tics (CBIT), which focuses on reducing tic severity by training control and regulation. In view of the regulation deficits characteristic to TDs, in the current study, we aimed to explore the contribution of CBIT beyond tic control, to a wider expression of regulation abilities-cognitive inhibition and emotion regulation. A total of 55 participants with TDs, aged 8-15, who were randomly assigned to group-CBIT or group-Educational Intervention for Tics, were compared on cognitive inhibition tests and use of emotion-regulation strategies, pre- and post-intervention. Whereas on none of the scales a significant interaction effect was found reflecting superiority of CBIT over EIT, repeated measures ANOVA revealed a significant time effect, with post hoc analyses indicating that cognitive inhibition and cognitive reappraisal significantly increased following CBIT intervention only. Within the group-CBIT, the increase in cognitive reappraisal was associated with higher intellectual ability. These findings may lead to a broader understanding of CBIT contribution to more than tic control, but rather to better cognitive and emotional regulation abilities.

A neurocomputational theory of action regulation predicts motor behavior in neurotypical individuals and patients with Parkinson’s disease

Surviving in an uncertain environment requires not only the ability to select the best action, but also the flexibility to withhold inappropriate actions when the environmental conditions change. Although selecting and withholding actions have been extensively studied in both human and animals, there is still lack of consensus on the mechanism underlying these action regulation functions, and more importantly, how they inter-relate. A critical gap impeding progress is the lack of a computational theory that will integrate the mechanisms of action regulation into a unified framework. The current study aims to advance our understanding by developing a neurodynamical computational theory that models the mechanism of action regulation that involves suppressing responses, and predicts how disruption of this mechanism can lead to motor deficits in Parkinson’s disease (PD) patients. We tested the model predictions in neurotypical individuals and PD patients in three behavioral tasks that involve free action selection between two opposed directions, action selection in the presence of conflicting information and abandoning an ongoing action when a stop signal is presented. Our results and theory suggest an integrated mechanism of action regulation that affects both action initiation and inhibition. When this mechanism is disrupted, motor behavior is affected, leading to longer reaction times and higher error rates in action inhibition.

Partial response electromyography as a marker of action stopping

Response inhibition is among the core constructs of cognitive control. It is notoriously difficult to quantify from overt behavior, since the outcome of successful inhibition is the lack of a behavioral response. Currently, the most common measure of action stopping, and by proxy response inhibition, is the model-based stop signal reaction time (SSRT) derived from the stop signal task. Recently, partial response electromyography (prEMG) has been introduced as a complementary physiological measure to capture individual stopping latencies. PrEMG refers to muscle activity initiated by the go signal that plummets after the stop signal before its accumulation to a full response. Whereas neither the SSRT nor the prEMG is an unambiguous marker for neural processes underlying response inhibition, our analysis indicates that the prEMG peak latency is better suited to investigate brain mechanisms of action stopping. This study is a methodological resource with a comprehensive overview of the psychometric properties of the prEMG in a stop signal task, and further provides practical tips for data collection and analysis.

A Process-Oriented View of Procedural Memory Can Help Better Understand Tourette's Syndrome

Tourette's syndrome (TS) is a neurodevelopmental disorder characterized by repetitive movements and vocalizations, also known as tics. The phenomenology of tics and the underlying neurobiology of the disorder have suggested that the altered functioning of the procedural memory system might contribute to its etiology. However, contrary to the robust findings of impaired procedural memory in neurodevelopmental disorders of language, results from TS have been somewhat mixed. We review the previous studies in the field and note that they have reported normal, impaired, and even enhanced procedural performance. These mixed findings may be at least partially be explained by the diversity of the samples in both age and tic severity, the vast array of tasks used, the low sample sizes, and the possible confounding effects of other cognitive functions, such as executive functions, working memory or attention. However, we propose that another often overlooked factor could also contribute to the mixed findings, namely the multiprocess nature of the procedural system itself. We propose that a process-oriented view of procedural memory functions could serve as a theoretical framework to help integrate these varied findings. We discuss evidence suggesting heterogeneity in the neural regions and their functional contributions to procedural memory. Our process-oriented framework can help to deepen our understanding of the complex profile of procedural functioning in TS and atypical development in general.

Impaired response inhibition during a stop-signal task in children with Tourette syndrome is related to ADHD symptoms: A functional magnetic resonance imaging study

OBJECTIVES

Tourette syndrome (TS) is characterised by the presence of sudden, rapid movements and vocalizations (tics). The nature of tics suggests impairments in inhibitory control. However, findings of impaired inhibitory control have so far been inconsistent, possibly due to small sample sizes, wide age ranges, or not taking medication use or attention-deficit/hyperactivity disorder (ADHD) comorbidity into account.

METHODS

We investigated group differences in response inhibition using an fMRI-based stop-signal task in 103 8 to 12-year-old children (n = 51 with TS, of whom n = 28 without comorbid ADHD [TS - ADHD] and n = 23 with comorbid ADHD [TS + ADHD]; and n = 52 healthy controls), and related these measures to tic and ADHD severity.

RESULTS

We observed an impaired response inhibition performance in children with TS + ADHD, but not in those with TS - ADHD, relative to healthy controls, as evidenced by a slower stop-signal reaction time, slower mean reaction times, and larger variability of reaction times. Dimensional analyses implicated ADHD severity as the driving force in these findings. Neural activation during failed inhibition was stronger in the inferior frontal gyrus and temporal and parietal areas in TS + ADHD compared to healthy controls.

CONCLUSIONS

Impaired inhibitory performance and increased neural activity in TS appear to manifest predominantly in relation to ADHD symptomatology.

The cognitive neuropsychiatry of Tourette syndrome

Introduction: Converging evidence from both clinical and experimental studies has shown that Tourette syndrome (TS) is not a unitary condition, but a cluster of multiple phenotypes, which encompass both tics and specific behavioural and cognitive symptoms (mainly attention-deficit and hyperactivity disorder and obsessive-compulsive disorder). Methods: We conducted a narrative review of the recent literature on the cognitive neuropsychiatry of TS. Results: Although clinical research has shown that TS is not associated with cognitive deficits per se, the findings of recent studies have suggested the presence of subtle alterations in specific cognitive functions. A promising line of research on imitative behaviour could provide a common background for the alterations in executive control and social cognition observed in TS. Two different (but not mutually exclusive) neurocognitive theories have recently suggested that TS could originate from altered perception-action binding and social decision-making dysfunction, respectively. Conclusions: Since the presence of behavioural comorbidities influences individualised treatment approaches, it is likely that a more precise characterisation of TS phenotypes, including cognitive aspects, will result in improved levels of care for patients with tic disorders.

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

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

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.