Children with primary complex motor stereotypies show impaired reactive but not proactive inhibition

Enhanced reactive inhibition in adolescents with non-suicidal self-injury disorder

AIM

To investigate whether the core of the pathophysiology underlying non-suicidal self-injury (NSSI) relates to poor impulse control due to impaired motor inhibition (i.e. the ability to inhibit a preplanned motor response).

METHOD

We conducted a case-control study to compare the proficiency of two domains of motor inhibition, that is, reactive and proactive inhibition, by giving the reaching arm version of the stop-signal task and a go-only task to 28 drug-naive adolescents with NSSI disorder (NSSID) (mean age [SD] 15 years 8 months [1 year 4 months]; three males and 25 females) and 28 typically developing adolescents (mean age 15 years 8 months [1 year 5 months]; three males and 25 females).

RESULTS

Reactive inhibition, as determined by the duration of the stop-signal reaction time, was enhanced in adolescents with NSSID compared to typically developing controls (194.2 [22.5 ms] vs 217.5 [17.3 ms], p < 0.001). By contrast, proactive inhibition was similar in both groups. Lastly, the level of impulsivity, assessed using the Barratt Impulsiveness Scale Version 11, did not differ between typically developing adolescents and adolescents with NSSID. However, adolescents with NSSID were more impulsive than controls in a subscale of the UPPS-P Impulsive Behavior Scale.

INTERPRETATION

NSSID is not driven by heightened motor impulsivity. Instead, adolescents with NSSID exhibited greater proficiency in reactive inhibition, a proxy for motor impulsivity. We suggest that the enhancement of reactive inhibition strengthens action control, allowing adolescents to suppress their self-protection instinct and perform NSSI behaviours.

Intermuscular coherence reveals that affective emotional pictures modulate neural control mechanisms during the initiation of arm pointing movements

Introduction

Several studies in psychology provided compelling evidence that emotions significantly impact motor control. Yet, these evidences mostly rely on behavioral investigations, whereas the underlying neurophysiological processes remain poorly understood.

Methods

Using a classical paradigm in motor control, we tested the impact of affective pictures associated with positive, negative or neutral valence on the kinematics and patterns of muscle activations of arm pointing movements performed from a standing position. The hand reaction and movement times were measured and electromyography (EMG) was used to measure the activities from 10 arm, leg and trunk muscles that are involved in the postural maintenance and arm displacement in pointing movements. Intermuscular coherence (IMC) between pairs of muscles was computed to measure changes in patterns of muscle activations related to the emotional stimuli.

Results

The hand movement time increased when an emotional picture perceived as unpleasant was presented as compared to when the emotional picture was perceived as pleasant. When an unpleasant emotional picture was presented, beta (β, 15-35 Hz) and gamma (γ, 35-60 Hz) IMC decreased in the recorded pairs of postural muscles during the initiation of pointing movements. Moreover, a linear relationship between the magnitude of the intermuscular coherence in the pairs of posturo-focal muscles and the hand movement time was found in the unpleasant scenarios.

Discussion

These findings reveal that emotional stimuli can significantly affect the content of the motor command sent by the central nervous system to muscles when performing voluntary goal-directed movements.

Effects of dopaminergic treatment on inhibitory control differ across Hoehn and Yahr stages of Parkinson's disease

Motor inhibitory control, a core component of cognitive control, is impaired in Parkinson's disease, dramatically impacting patients' abilities to implement goal-oriented adaptive strategies. A progressive loss of the midbrain's dopamine neurons characterizes Parkinson's disease and causes motor features responsive to dopaminergic treatments. Although such treatments restore motor symptoms, their impact on response inhibition is controversial. Most studies failed to show any effect of dopaminergic medicaments, although three studies found that these drugs selectively improved inhibitory control in early-stage patients. Importantly, all previous studies assessed only one domain of motor inhibition, i.e. reactive inhibition (the ability to react to a stop signal). The other domain, i.e. proactive inhibition (the ability to modulate reactive inhibition pre-emptively according to the current context), was utterly neglected. To re-examine this issue, we recruited cognitively unimpaired Parkinson's patients under dopaminergic treatment in the early (Hoehn and Yahr, 1-1.5, n = 20), intermediate (Hoehn and Yahr 2, n = 20), and moderate/advanced (Hoehn and Yahr, 2.5-3, n = 20) stages of the disease. Using a cross-sectional study design, we compared their performance on a simple reaction-time task and a stop-signal task randomly performed twice on dopaminergic medication (ON) and after medication withdrawal (OFF). Normative data were collected on 30 healthy controls. Results suggest that medication effects are stage-dependent. In Hoehn and Yahr 1-1.5 patients, drugs selectively impair reactive inhibition, leaving proactive inhibition unaffected. In the ON state, Hoehn and Yahr two patients experienced impaired proactive inhibition, whereas reactive inhibition is no longer affected, as it deteriorates even during the OFF state. By contrast, Hoehn and Yahr 2.5-3 patients exhibited less efficient reactive and proactive inhibition in the OFF state, and medication slightly improved proactive inhibition. This evidence aligns with the dopamine overdose hypothesis, indicating that drug administration may overdose intact dopamine circuitry in the earliest stages, impairing associated cognitive functions. In later stages, the progressive degeneration of dopaminergic neurons prevents the overdose and can exert some beneficial effects. Thus, our findings suggest that inhibitory control assessment might help tailor pharmacological therapy across the disease stage to enhance Parkinson's disease patients' quality of life by minimizing the hampering of inhibitory control and maximizing the reduction of motor symptoms.

Unveiling the influence of task-relevance of emotional faces on behavioral reactions in a multi-face context using a novel Flanker-Go/No-go task

Recent research indicates that emotional faces affect motor control only when task-relevant. However, these studies utilized a single-face presentation, which does not accurately mirror real-life situations wherein we frequently engage with multiple individuals simultaneously. To overcome this limitation, we gave 40 participants two versions of a novel Flanker-Go/No-go task, where we presented three-face stimuli with a central target and two task-irrelevant flankers that could be congruent or incongruent with the target for valence and gender. In the Emotional Discrimination Task (EDT), participants had to respond to fearful or happy targets and refrain from moving with neutral ones. In the Gender Discrimination Task (GDT), the same images were shown, but participants had to respond according to the target's gender. In line with previous studies, we found an effect of valence only in EDT, where fearful targets increased reaction times and omission error rates compared to happy faces. Notably, the flanker effect, i.e., slower and less accurate responses in incongruent than congruent conditions, was not found. This likely stems from the higher perceptual complexity of faces than that of stimuli traditionally used in the Eriksen Flanker task (letters or signs), leading to a capacity limit in face feature processing.

High-frequency rTMS over the left DLPFC improves the response inhibition control of young healthy participants: an ERP combined 1H-MRS study

Introduction

Unlike the effect of repetitive transcranial magnetic stimulation (rTMS) in treating neuropsychiatric diseases, little is known about how personal factors might account for the disparity of results from studies of cognition and rTMS. In this study, we investigated the effects of high-frequency rTMS on response inhibition control and explored the time course changes in cognitive processing and brain metabolic mechanisms after rTMS using event-related potentials (ERPs) and magnetic resonance spectroscopy (¹H-MRS).

Methods

Participants were all right-handed and were naive to rTMS and the Go/NoGo task. Twenty-five healthy young participants underwent one 10 Hz rTMS session per day in which stimulation was applied over the left dorsolateral prefrontal cortex (DLPFC), and a homogeneous participant group of 25 individuals received a sham rTMS treatment for 1  week. A Go/NoGo task was performed, an electroencephalogram (EEG) was recorded, and ¹H-MRS was performed.

Results

The results revealed that there was a strong trend of decreasing commission errors of NoGo stimuli by high frequency rTMS over the left DLPFC, whereas there was no significant difference between before and after rTMS treatment with respect to these parameters in the sham rTMS group. High-frequency rTMS significantly increased the amplitude of NoGo-N2 but not Go-N2, Go-P3, or NoGo-P3. The myo-inositol /creatine complex (MI/Cr) ratio, indexing cerebral metabolism, in the left DLPFC was decreased in the rTMS treated group.

Discussion

This observation supports the view that high-frequency rTMS over the left DLPFC has the strong tendency of reducing commission errors behaviorally, increase the amplitude of NoGo-N2 and improve the response inhibition control of healthy young participants. The results are consistent with the excitatory properties of high frequency rTMS. We suggest that the increase in the NoGo-N2 amplitude may be related to the increased excitability of the DLPFC-anterior cingulate cortex (ACC) neural loop. Metabolic changes in the DLPFC may be a possible mechanism for the improvement of the response inhibition control of rTMS.

Seeing in my way or your way: impact of intelligence, attention, and empathy on brain reactivity

Previous studies showed that neurotypical adults are able to engage in unconscious analyses of others' mental states in the context of automatic perspective taking and experience systematic difficulties when judging the conflicts between their own (Self) and another's (Other) perspective. Several functional MRI (fMRI) studies reported widespread activation of mentalizing, salience, and executive networks when adopting the Other compared to Self perspective. This study aims to explore whether cognitive and emotional parameters impact on brain reactivity in dot perspective task (dPT). We provide here an fMRI analysis based on individual z-scores in eighty-two healthy adults who underwent the Samson's dPT after detailed assessment of fluid intelligence, attention, levels of alexithymia and social cognition abilities. Univariate regression models were used to explore the association between brain activation patterns and psychological variables. There was a strong positive association between Wechsler Adult Intelligence Scale (WAIS) and fMRI z-scores in Self perspective. When the Other perspective is taken, Continuous Performance Test (CPT)-II parameters were negatively associated with fMRI z-scores. Individuals with higher Toronto Alexithymia scale (TAS) score and lower scores in mini-Social cognition and Emotional Assessment (SEA) displayed significantly higher egocentric interference-related fMRI z-scores. Our data demonstrate that brain activation when focusing on our own perspective depends on the levels of fluid intelligence. Decreased attentional recruitment and decreased inhibitory control affects the brain efforts to adopt the Other perspective. Egocentric interference-associated brain fMRI activation was less marked in cases with better empathy abilities but the opposite was true for persons who experience increased difficulties in the recognition of emotions.

Restart errors reaction time of a two-step inhibition process account for the violation of the race model's independence in multi-effector selective stop signal task

Goal-oriented actions often require the coordinated movement of two or more effectors. Sometimes multi-effector movements need to be adjusted according to a continuously changing environment, requiring stopping an effector without interrupting the movement of the others. This form of control has been investigated by the selective Stop Signal Task (SST), requiring the inhibition of an effector of a multicomponent action. This form of selective inhibition has been hypothesized to act through a two-step process, where a temporary global inhibition deactivating all the ongoing motor responses is followed by a restarting process that reactivates only the moving effector. When this form of inhibition takes place, the reaction time (RT) of the moving effector pays the cost of the previous global inhibition. However, it is poorly investigated if and how this cost delays the RT of the effector that was required to be stopped but was erroneously moved (Stop Error trials). Here we measure the Stop Error RT in a group of participants instructed to simultaneously rotate the wrist and lift the foot when a Go Signal occurred, and interrupt both movements (non-selective Stop version) or only one of them (selective Stop version) when a Stop Signal was presented. We presented this task in two experimental conditions to evaluate how different contexts can influence a possible proactive inhibition on the RT of the moving effector in the selective Stop versions. In one context, we provided the foreknowledge of the effector to be inhibited by presenting the same selective or non-selective Stop versions in the same block of trials. In a different context, while providing no foreknowledge of the effector(s) to be stopped, the selective and non-selective Stop versions were intermingled, and the information on the effector to be stopped was delivered at the time of the Stop Signal presentation. We detected a cost in both Correct and Error selective Stop RTs that was influenced by the different task conditions. Results are discussed within the framework of the race model related to the SST, and its relationship with a restart model developed for selective versions of this paradigm.

Alcohol-induced deficits in reactive control of response selection and inhibition are counteracted by a seemingly paradox increase in proactive control

High-dose alcohol intoxication reduces cognitive control, including inhibition. Although inhibition deficits may contribute to the behavioral deficits commonly observed in alcohol use disorder (AUD), many questions about potentially modulating factors have remained unanswered. We examined the effects of experimentally induced high-dose alcohol intoxication (~ 1.1 ‰) on the interplay between controlled vs. automatic response selection and inhibition in healthy young men. A holistic EEG-based theta activity analysis that considered both reactive control during task performance and preceding proactive control processes was run. It revealed a previously unknown seesaw relationship, with decreased reactive control, but paradoxically increased proactive control. Most importantly, alcohol-induced increases in proactive occipital theta band power were associated with reductions in negative alcohol effects on reactive control processes associated with decreased activity in the SMA and medial frontal cortex. Our findings demonstrate that research should not solely focus on immediate effects during task performance. Aside from differential neurobiochemical and neuroanatomical effects of alcohol, it is also conceivable that proactive control may have been recruited in a (secondary) response to compensate for alcohol-induced impairments in reactive control. Against this background, it could be promising to investigate changes in such compensatory mechanisms in pronounced alcohol-associated inhibition deficits, like in AUD patients.

Towards Conceptual Clarification of Proactive Inhibitory Control: A Review

The aim of this selective review paper is to clarify potential confusion when referring to the term proactive inhibitory control. Illustrated by a concise overview of the literature, we propose defining reactive inhibition as the mechanism underlying stopping an action. On a stop trial, the stop signal initiates the stopping process that races against the ongoing action-related process that is triggered by the go signal. Whichever processes finishes first determines the behavioral outcome of the race. That is, stopping is either successful or unsuccessful in that trial. Conversely, we propose using the term proactive inhibition to explicitly indicate preparatory processes engaged to bias the outcome of the race between stopping and going. More specifically, these proactive processes include either pre-amping the reactive inhibition system (biasing the efficiency of the stopping process) or presetting the action system (biasing the efficiency of the go process). We believe that this distinction helps meaningful comparisons between various outcome measures of proactive inhibitory control that are reported in the literature and extends to experimental research paradigms other than the stop task.

Reduced motor planning underlying inhibition of prepotent responses in children with ADHD

To flexibly regulate their behavior, children's ability to inhibit prepotent responses arises from cognitive and motor mechanisms that have an intertwined developmental trajectory. Subtle differences in planning and control can contribute to impulsive behaviors, which are common in Attention Deficit and Hyperactivity Disorder (ADHD) and difficult to be assessed and trained. We adapted a Go/No-Go task and employed a portable, low-cost kinematic sensor to explore the different strategies used by children with ADHD or typical development to provide a prepotent response (dominant condition) or inhibit the prepotent and select an alternative one (non-dominant condition). Although no group difference emerged on accuracy levels, the kinematic analysis of correct responses revealed that, unlike neurotypical children, those with ADHD did not show increased motor planning in non-dominant compared to dominant trials. Future studies should investigate whether motor control could help children with ADHD compensate for planning difficulties. This strategy might make inhibition harder in naturalistic situations that involve complex actions. Combining cognitive and kinematic measures is a potential innovative method for assessment and intervention of subtle differences in executive processes such as inhibition, going deeper than is possible based on accuracy outcomes alone.

Inhibitory Control Development: A Network Neuroscience Perspective

As one of the core executive functions, inhibition plays an important role in human life through development. Inhibitory control is defined as the ability to suppress actions when they are unlikely to accomplish valuable results. Contemporary neuroscience has investigated the underlying neural mechanisms of inhibitory control. The controversy started to arise, which resulted in two schools of thought: a modulatory and a network account of inhibitory control. In this systematic review, we survey developmental mechanisms in inhibitory control as well as neurodevelopmental diseases related to inhibitory dysfunctions. This evidence stands against the modulatory perspective of inhibitory control: the development of inhibitory control does not depend on a dedicated region such as the right inferior frontal gyrus (rIFG) but relies on a more broadly distributed network.

Two sides of the same coin: ADHD affects reactive but not proactive inhibition in children

Children with attention-deficit/hyperactivity disorder (ADHD) present a deficit in inhibitory control. Still, it remains unclear whether it comes from a deficit in reactive inhibition (ability to stop the action in progress), proactive inhibition (ability to exert preparatory control), or both.We compared the performance of 39 children with ADHD and 42 typically developing children performing a Simon choice reaction time task. The Simon task is a conflict task that is well-adapted to dissociate proactive and reactive inhibition. Beyond classical global measures (mean reaction time, accuracy rate, and interference effect), we used more sophisticated dynamic analyses of the interference effect and accuracy rate to investigate reactive inhibition. We studied proactive inhibition through the congruency sequence effect (CSE).Our results showed that children with ADHD had impaired reactive but not proactive inhibition. Moreover, the deficit found in reactive inhibition seems to be due to both a stronger impulse capture and more difficulties in inhibiting impulsive responses. These findings contribute to a better understanding of how ADHD affects inhibitory control in children.

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

Simple Summary

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

Abstract

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

Altered Effective Connectivity within an Oculomotor Control Network in Unaffected Relatives of Individuals with Schizophrenia

The ability to rapidly stop or change a planned action is a critical cognitive process that is impaired in schizophrenia. The current study aimed to examine whether this impairment reflects familial vulnerability to schizophrenia across two experiments comparing unaffected first-degree relatives to healthy controls. First, we examined performance on a saccadic stop-signal task that required rapid inhibition of an eye movement. Then, in a different sample, we investigated behavioral and neural responses (using fMRI) during a stop-signal task variant that required rapid modification of a prepared eye movement. Here, we examined differences between relatives and healthy controls in terms of activation and effective connectivity within an oculomotor control network during task performance. Like individuals with schizophrenia, the unaffected relatives showed behavioral evidence for more inefficient inhibitory processes. Unlike previous findings in individuals with schizophrenia, however, the relatives showed evidence for a compensatory waiting strategy. Behavioral differences were accompanied by more activation among the relatives in task-relevant regions across conditions and group differences in effective connectivity across the task that were modulated differently by the instruction to exert control over a planned saccade. Effective connectivity parameters were related to behavioral measures of inhibition efficiency. The results suggest that individuals at familial risk for schizophrenia were engaging an oculomotor control network differently than controls and in a way that compromises inhibition efficiency.

How Does Task Presentation Impact Motor Inhibition Performance in Young Children?

Peg tapping tasks are commonly used as a measure of inhibitory skill in young children. However, differences in the way the task is presented may influence children's performance. For example, if a peg tapping task is presented at regular intervals, children can entrain to the presentation pulse, which may in turn support their performance. This study assessed how speed and regularity of presentation may support or impair children's responses. An experimenter was filmed delivering the tapping task at two different speeds (120 bpm/3,000 ms per trial and 150 bpm/2,400 ms per trial). Additionally, they were filmed delivering the task at regular intervals (i.e., the onset of each trial was predictable), or at irregular intervals (the onset of each trial was unpredictable). N = 103 children aged between 5 and 6 years old were tested on the task. They completed one block with 20 regular interval trials and another block with 20 irregular interval trials. Block presentation order was randomized. Children who achieved over 90% accuracy on the task were then presented with two more blocks at 150 bpm. Children's response accuracy was measured. Our results show a difference in children's accuracy across all conditions with trials presented in an irregular manner producing poorer performance on the task. The study demonstrates how speed and regularity of presentation can affect children's scores on a tapping task used to measure inhibition. Demands on working memory, motor ability, and speed of processing are all affected by adjustments in presentation. Entrainment to a pulse is also a potential mechanism employed by children to support their performance on this task.

Aberrant prefrontal cortical-striatal functional connectivity in children with primary complex motor stereotypies

Motor stereotypies are rhythmic, repetitive, prolonged, predictable, and purposeless movements that stop with distraction. Although once believed to occur only in children with neurodevelopmental disorders such as autism, the presence and persistence of complex motor stereotypies (CMS) in otherwise typically developing children (primary CMS) has been well-established. Little, however, is known about the underlying pathophysiology of these unwanted actions. The aim of the present study was to use resting-state functional magnetic resonance imaging to evaluate functional connectivity within frontal-striatal circuits that are essential for goal-directed and habitual activity in children with primary complex motor stereotypies. Functional connectivity between prefrontal cortical and striatal regions, considered essential for developing goal-directed behaviors, was reduced in children with primary CMS compared to their typically developing peers. In contrast, functional connectivity between motor/premotor and striatal regions, critical for developing and regulating habitual behaviors, did not differ between groups. This documented alteration of prefrontal to striatal connectivity could provide the underlying mechanism for the presence and persistence of complex motor stereotypies in otherwise developmentally normal children.

The effects of discrimination on the adoption of different strategies in selective stopping

Selective stopping is demanded in situations where responses must be suppressed to certain signals, but not others. To explore this type of inhibition, the standard stop-signal task has been modified to include a selective implementation of response inhibition by introducing a new stimulus that participants should ignore. However, a stimulus-selective stop-signal task can be performed following different strategies. Some participants fulfill the selective implementation of the stopping process after discriminating the stop and ignore signals, but some others stop the ongoing response whenever any new stimulus appears. The factors that influence this strategy choice are being explored, where both task and participant variables are under consideration. This study aimed to investigate whether the difficulty in discriminating between stop and ignore signals influences strategy adoption. Additionally, we examined whether participants modify their strategy in a flexible manner throughout the task in alternating easy and hard discrimination condition blocks. In the easy discrimination condition, the stop and the ignore signals differed both in color and shape, whereas in the hard discrimination condition, they only differed in shape. Our results from 64 participants revealed that manipulating the difficulty of signal discrimination strongly influenced strategy choice. Also, we found that participants can adapt their strategy according to task demands. They preferentially adopted a selective stopping strategy when discrimination was easy, whereas they changed to a nonselective stopping strategy under the hard discrimination condition. Overall, results from the current study suggest that signal discrimination difficulty influences the adoption of strategies in selective stopping.

Reactive and Proactive Adaptation of Cognitive and Motor Neural Signals during Performance of a Stop-Change Task

The ability to inhibit or suppress unwanted or inappropriate actions, is an essential component of executive function and cognitive health. The immense selective pressure placed on maintaining inhibitory control processes is exemplified by the relatively small number of instances in which these systems completely fail in the average person's daily life. Although mistakes and errors do inevitably occur, inhibitory control systems not only ensure that this number is low, but have also adapted behavioral strategies to minimize future failures. The ability of our brains to adapt our behavior and appropriately engage proper motor responses is traditionally depicted as the primary domain of frontal brain areas, despite evidence to the fact that numerous other brain areas contribute. Using the stop-signal task as a common ground for comparison, we review a large body of literature investigating inhibitory control processes across frontal, temporal, and midbrain structures, focusing on our recent work in rodents, in an effort to understand how the brain biases action selection and adapts to the experience of conflict.

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.

Obsessive-Compulsive Disorder and Decision Making under Ambiguity: A Systematic Review with Meta-Analysis

In the last decade, decision-making has been proposed to have a central role in obsessive-compulsive disorder (OCD) aetiology, since patients show pathological doubt and an apparent inability to make decisions. Here, we aimed to comprehensively review decision making under ambiguity, as measured by the Iowa Gambling Task (IGT), in OCD, using a meta-analytic approach. According to PRISMA Guidelines, we selected 26 studies for a systematic review and, amongst them, 16 studies were included in a meta-analysis, comprising a total of 846 OCD patients and 763 healthy controls (HC). Our results show that OCD patients perform significantly lower than HC at the IGT, pointing towards the direction of a decision making impairment. In particular, this deficit seems to emerge mainly in the last three blocks of the IGT. IGT scores in OCD patients under the age of 18 were still significantly lower than in HC. Finally, no difference emerged between medicated and unmedicated patients, since they both scored significantly lower at the IGT compared to HC. In conclusion, our results are in line with the hypothesis according to which decision making impairment might represent a potential endophenotype lying between the clinical manifestation of OCD and its neurobiological aetiology.

Inhibitory control in trauma-exposed youth: A systematic review

The aim of this systematic review was to provide insight in inhibitory control (prepotent response inhibition and interference control) in trauma-exposed youth from a developmental perspective and exploring the effects of prolonged stress. A systematic search was conducted, resulting in 1722 abstracts. Of those, 33 studies met inclusion criteria. Twelve studies measured prepotent response inhibition (Go/no-go and Stop-signal task), 20 studies measured interference control (Flanker and Stroop task), and one measured both. Some studies indeed found evidence for prolonged trauma exposure impeding both subcomponents of inhibitory control, although others did not. At a later age, inhibitory control problems on task performance seem to disappear. However, distinct patterns of brain activity may suggest that those individuals employ compensation strategies. Together, the findings may suggest that non-specific inhibitory control problems occur after prolonged trauma exposure, with older youth possibly employing compensation strategies on the tasks. Future studies may provide a clearer picture of the compensation strategies and the circumstances in which they become visible.