Impaired Inhibitory Control Research Articles

REM theta activity enhances inhibitory control in typically developing children but not children with ADHD symptoms.

Sleep disturbances impair cognitive functioning in typically developing populations. Children with attention-deficit/hyperactivity disorder (ADHD), a disorder characterized by impaired inhibitory control and attention, commonly experience sleep disturbances. Whether inhibitory impairments are related to sleep deficits in children with ADHD is unknown. Children with ADHD (n = 18; M age = 6.70 years) and typically developing controls (n = 15; M age = 6.73 years) completed a Go/No-Go task to measure inhibitory control and sustained attention before and after polysomnography-monitored overnight sleep. Inhibitory control and sustained attention were improved following overnight sleep in typically developing children. Moreover, morning inhibitory control was positively correlated with rapid eye movement (REM) theta activity in this group. Although REM theta activity was greater in children with ADHD compared to typically developing children, it was functionally insignificant. Neither inhibitory control nor sustained attention was improved following overnight sleep in children with ADHD symptoms, and neither of these behaviors was associated with REM theta activity in this group. Taken together, these results indicate that elevated REM theta activity may be functionally related to ADHD symptomology, possibly reflecting delayed cortical maturation.

Prepotent response inhibition and reaction times in children with attention deficit/hyperactivity disorder from a Caribbean community.

Impairment in inhibitory control has been postulated as an underlying hallmark of attention deficit/hyperactivity disorder (ADHD), which can be utilized as a quantitative trait for genetic studies. Here, we evaluate whether inhibitory control, measured by simple automatized prepotent response (PR) inhibition variables, is a robust discriminant function for the diagnosis of ADHD in children and can be used as an endophenotype for future genetic studies. One hundred fifty-two school children (30.9% female, 67.8% with ADHD) were recruited. The ADHD checklist was used as the screening tool, whilst the DSM-IV Mini International Neuropsychiatry Interview, neurologic interview and neurologic examination, and the WISC III FSIQ test were administered as the gold standard procedure to assert ADHD diagnosis. A Go/No-Go task using a naturalistic and automatized visual signal was administered. A linear multifactor model (MANOVA) was fitted to compare groups including ADHD status, age, and gender as multiple independent factors. Linear discriminant analysis and the receiver operating characteristic curve were used to assess the predictive performance of PR inhibition variables for ADHD diagnosis. We found that four variables of prepotent response reaction time- and prepotent response inhibition established statistically significant differences between children with and without ADHD. Furthermore, these variables generated a strong discriminant function with a total classification capability of 73, 84% specificity, 68% sensitivity, and 90% positive predictive value for ADHD diagnosis, which support reaction times as a candidate endophenotype that could potentially be used in future ADHD genetic research.

The consummatory and motivational behaviors for natural rewards following long-term withdrawal from morphine: no anhedonia but persistent maladaptive behaviors for high-value rewards.

The negative affective state, e.g., anhedonia, emerges after abstinence from abused drugs may be linked to the motivational processes of drug craving and relapse. Although anhedonia diminishes over time with drug abstinence, it is not yet rather explicit whether anhedonia exists or not following protracted withdrawal. The behavioral responses to natural rewards were examined after 2 to 3weeks withdrawal from morphine. Male rats were pretreated with either a binge-like morphine paradigm or daily saline injection for 5days. The consummatory and motivational behaviors for three natural rewards (sucrose solutions 4, 15, and 60%, social stimulus: male rat, and sexual stimulus: estrous female rat) were examined under varied testing conditions. The morphine-withdrawn rats significantly increased their intake of 15% sucrose solution during the 1-h consumption test and their operant responding for 15% sucrose solution under a progressive ratio (PR) schedule of reinforcement. When obtaining a reinforcer was associated with a 0.5mA foot shock under a PR-punishment schedule, the morphine-withdrawn rats showed a higher performance for 60% sucrose solution. Meanwhile, the morphine-withdrawn rats displayed a higher motivation to sexual stimulus during the free-approach test and more approaching behaviors towards sexual stimulus in a conflict-based approach test (concurrent presence of reward and aversive stimulus). No anhedonia-like behavior but sensitized behaviors for natural rewards were found after long-term morphine withdrawal. Notably, the morphine-withdrawn rats displayed persistent motivated behaviors for high-value rewards (60% sucrose and sexual stimulus) in the conflict tests suggesting impairments in inhibitory control in morphine-treated rats.

P237 Modulating executive functions and working memory performance on clinical neuropsychological tasks with theta burst transcranial magnetic stimulation

Introduction Theta burst stimulation (TBS) protocols hold high promise in neuropsychological rehabilitation thanks to its ability to induce lasting effects on cortical excitability following a short delivery time. Nevertheless, its ability to inhibit (continuous protocol, cTBS) or facilitate (intermittent, iTBS) brain function from cortical areas other than the motor cortex remains to be fully established. The behavioral effects of TBS over the dorsolateral prefrontal cortex (DLPFC) are particularly interesting given its involvement in working memory and executive processing, often impaired after brain injury, and also due to its role of hub of frontal areas, for which it is frequently chosen as a target for treatment and rehabilitation. Objective To explore the ability of cTBS and iTBS to modulate working memory and executive functions assessed with clinical neuropsychological tasks. Materials and methods 36 healthy participants performed 3 clinical neuropsychological tasks: Digits Backward, Stroop test and Tower of Hanoi (Fig. 1). Subjects were assessed twice, first at baseline 1 week prior to stimulation and immediately following a single session of either active cTBS, active iTBS or sham TBS, delivered to the left DLPFC. Results Following sham TBS participants’ performance improved in the Stroop test, with higher scores in Color and Color-Word conditions, as well as lower interference scores (Fig. 2), likely caused by practice effects. Both, iTBS and cTBS, yielded improvements in the Digits Backward task and the Word score of the Stroop test. Moreover, similarly to the sham group, following iTBS participants showed lower Interference scores. In contrast, expected improvements in color score were not induced. Finally, cTBS decreased the number of movements necessary to complete the Tower of Hanoi. Nonetheless, at difference with the sham group, no improvements were observed in the Interference score of Stroop test. Conclusions TBS over DLPFC modulates working memory performance and executive processes. Both protocols resulted in similar working memory and information processing speed outcomes, whereas their effect on executive functions differed: cTBS impaired inhibitory control but improved planning abilities in a spatial task, meanwhile, no specific effects were observed following iTBS. Download : Download high-res image (431KB) Download : Download full-size image Download : Download high-res image (217KB) Download : Download full-size image

Are you a doctor? … Are you a doctor? I’m not a doctor! A reappraisal of mitigated echolalia in aphasia with evaluation of neural correlates and treatment approaches

ABSTRACTBackground: Mitigated echolalia (ME) is a symptom of aphasia which refers to a seemingly deliberate repetition of just-heard words and phrase fragments. ME has historically been viewed as a compensatory strategy aimed to strengthen auditory comprehension. Nevertheless, this hypothesis and other possible functional deficits underlying ME have not been evaluated so far.Aims: This study aimed to (a) reappraise ME in the frame of modern neuroscience; (b) report the effects of Constraint-Induced Aphasia Therapy (CIAT) and a cognition-enhancing drug (memantine) on detrimental ME in a patient (CCR) with fluent aphasia; and (c) analyse the functional and structural brain correlates of ME in CCR with multimodal neuroimaging.Methods & Procedure: Tasks tapping verbal expression and auditory comprehension were administered to CCR to evaluate ME. After baseline testing, evaluations were performed under placebo alone (weeks 0–16), combined placebo with CIAT (weeks 16–18), placebo treatment alone (weeks 18–20), washout (weeks 20–24) and memantine (weeks 24–48). Instructions to reduce ME during CIAT were provided to CCR. Language evaluation and multimodal neuroimaging were also performed 10 years after ending treatment.Outcomes & Results: At baseline, ME occurred in spontaneous speech and in difficult-to-understand single words, indicating impaired meaning access. However, more instances of ME were heard in sentence comprehension, reflecting additional impairment in short-term memory. ME also occurred in words that were correctly defined and understood to the extent that even after accessing word meaning successfully, CCR repeated the same word several times, suggesting impaired inhibitory response control. In comparison with baseline, analysis of auditory sentence comprehension under treatment revealed significant decrements of ME just after ending CIAT and 2 weeks later. These gains were maintained under memantine 6 months later. No changes in ME were found during both placebo and washout phases. Instructions to constrain ME reduced the time to complete a sentence comprehension task 2 weeks after CIAT. ME returned to baseline levels 10 years later. Multimodal imaging suggested that ME in CCR resulted from residual activity of remnants of the left dorsal stream and the intact right white matter tracts after extensive damage to the left ventral stream.Conclusions: ME in CCR interfered with functional communication, and it may be attributed to deficits in sound-meaning mapping, auditory short-term memory, attentional control, and inhibition of repetition mechanisms. Our preliminary evidence suggests that ME, in patients like CCR, may be modulated with specific instructions during aphasia therapy and drugs.

Suppression of Competing Memories in Substance-Related and Addictive Disorders

Substance-related and addictive disorders have been strongly linked to inhibitory control impairment. However, inhibitory deficits in this class of psychiatric disorders have been tested almost exclusively with measures of inhibition of motor, overt behavior. Here, instead, we investigated inhibitory deficits in these disorders by assessing the integrity of inhibitory control over internal, covert responses. Two groups of patients with alcohol and drug addiction and a control group of healthy individuals were administered a retrieval-practice paradigm assessing inhibition of competing memories. All groups showed comparable beneficial effects of retrieval practice. In contrast, successful suppression of competing memories was achieved by the control group only. This indicates that the deficit in clinical groups can be ascribed to an impairment in inhibitory control over memory retrieval rather than to a general memory impairment. In conclusion, inhibitory deficits in addiction are more widespread than previously shown, as they encompass memory control mechanisms.

The BACHD Rat Model of Huntington Disease Shows Signs of Fronto-Striatal Dysfunction in Two Operant Conditioning Tests of Short-Term Memory

The BACHD rat is a recently developed transgenic animal model of Huntington disease, a progressive neurodegenerative disorder characterized by extensive loss of striatal neurons. Cognitive impairments are common among patients, and characterization of similar deficits in animal models of the disease is therefore of interest. The present study assessed the BACHD rats' performance in the delayed alternation and the delayed non-matching to position test, two Skinner box-based tests of short-term memory function. The transgenic rats showed impaired performance in both tests, indicating general problems with handling basic aspects of the tests, while short-term memory appeared to be intact. Similar phenotypes have been found in rats with fronto-striatal lesions, suggesting that Huntington disease-related neuropathology might be present in the BACHD rats. Further analyses indicated that the performance deficit in the delayed alternation test might be due to impaired inhibitory control, which has also been implicated in Huntington disease patients. The study ultimately suggests that the BACHD rats might suffer from neuropathology and cognitive impairments reminiscent of those of Huntington disease patients.

失眠患者的抑制控制功能受损及其脑机制

失眠的发生和维持与抑制控制功能受损息息相关。失眠患者抑制控制受损表现在注意控制、反应抑制和认知抑制三方面，其中注意控制受损得到多数研究的证实。认知抑制和反应抑制是否受损尚存争议，但失眠患者存在前额叶、海马、丘脑等脑区静息态结构和功能的受损以及任务态下前额叶的激活不足，都提示失眠患者可能有认知抑制和反应抑制能力的受损。右侧额中回结构和功能的受损可能是这三种抑制控制功能受损的共同脑机制。未来的研究应对失眠患者抑制控制功能受损进行干预，推进其认知抑制的研究，揭示失眠持续时间、严重程度和抑制控制功能的关系，力图深入探讨失眠患者抑制控制功能受损的原因及干预方法。 The impairment of inhibitory control plays an important role in the development and mainten-ance of insomnia. The injury on inhibitory control of insomnia disorder included attention control, response inhibition, and cognitive inhibition, but most researches focused on the injury of attention control. The damage of cognitive inhibition and response inhibition is remaining controversial. However, the damage of structure and function in prefrontal cortex, hippocampus, and thalamus in resting state, and prefrontal hypoactivation in task may point out the impairment. The common mechanisms of the three injury inhibitory control functions may be derived from right middle frontal gyri. Future researches need focus on the intervention on impaired inhibitory control, promote the research of cognitive inhibition in patients with insomnia, and investigate the relationship between inhibitory control, insomnia duration and its severity. Thus we can fully explore the causes of the impaired inhibitory control and find its corresponding intervention methods.

Angry but not neutral faces facilitate response inhibition in schizophrenia patients.

Schizophrenia is a very heterogeneous disorder with extensive impairments in cognitive as well as emotional abilities. One critical domain is response inhibition, and previous studies in schizophrenia patients have mostly observed impairments, i.e., slower inhibition. Moreover, response inhibition to socially salient stimuli has not been investigated in schizophrenia so far. Therefore, to elucidate emotion-cognition interactions by examining potential emotional effects on inhibition processes and further investigate the association of cognition with inhibition we used an emotional stop signal task in 27 schizophrenia patients and 27 gender- and age-matched controls. Task irrelevant emotional faces (angry and neutral) were used as stimuli in a stop signal reaction time task. Regarding accuracy, patients showed significantly worse performance in neutral trials, while their performance in anger trials (stop and go) was similar to controls. Angry faces elicited faster response inhibition in both groups, underlining an emotional facilitation effect. Neurocognitive functions significantly correlated with accuracy in the stop signal task in schizophrenia patients, thus further strengthening the notion of the strong link between cognitive abilities and inhibition processes. Inhibitory control impairments are of high clinical interest due to their association with substance abuse, impulsive behavior and suicide. Based on our data, neutral faces significantly affect response inhibition in schizophrenia while an emotional facilitation effect was apparent for angry faces even in schizophrenia patients. Thus, our data further support the notion that neutral face processing is critically impaired in schizophrenia.

Neurocognitive predictors of treatment response to randomized treatment in adults with tic disorders

Tourette's disorder (TS) and chronic tic disorder (CTD) are neurodevelopmental disorders characterized by involuntary vocal and motor tics. Consequently, TS/CTD have been conceptualized as disorders of cognitive and motor inhibitory control. However, most neurocognitive studies have found comparable or superior inhibitory capacity among individuals with TS/CTD relative to healthy controls. These findings have led to the hypothesis that individuals with TS/CTD develop increased inhibitory control due to the constant need to inhibit tics. However, the role of cognitive control in TS/CTD is not yet understood, particularly in adults. To examine the role of inhibitory control in TS/CTD, the present study investigated this association by assessing the relationship between inhibitory control and treatment response in a large sample of adults with TS/CTD. As part of a large randomized trial comparing behavior therapy versus supportive psychotherapy for TS/CTD, a battery of tests, including tests of inhibitory control was administered to 122 adults with TS/CTD at baseline. We assessed the association between neuropsychological test performance and change in symptom severity, as well as compared the performance of treatment responders and non-responders as defined by the Clinical Global Impression Scale. Results indicated that change in symptoms, and treatment response were not associated with neuropsychological performance on tests of inhibitory control, intellectual ability, or motor function, regardless of type of treatment. The finding that significant change in symptom severity of TS/CTD patients is not associated with impairment or change in inhibitory control regardless of treatment type suggests that inhibitory control may not be a clinically relevant facet of these disorders in adults.

Alcohol's acute effect on food intake is mediated by inhibitory control impairments

Alcohol's acute effect on food intake is mediated by inhibitory control impairments

Gray Matter Morphological Alteration in Obsessive Compulsive Disorder: Evidence for an Inhibitory Control and Emotional Regulation Disorder

The integration of obsessive compulsive disorders (OCD) in the Obsessive Compulsive and Related Disorders cluster, while emphasizing the centrality of inhibitory control and repetitive behaviors may fail to fully acknowledge the existence of significant affective and other cognitive impairments. The objective of this paper is to review evidence from gray matter morphology imaging studies identifying brain abnormalities in OCD that may help to explain the complexity of OCD impairments. Building on these studies, OCD seems to be a disorder of both inhibitory control and emotional regulation. Volumetric and shape abnormalities in different brain territories of the prefrontal cortex, orbitofrontal cortex, thalamus, striate and cerebellum may contribute to impairments in inhibitory control. On the other side, gray matter shape and volume alterations in regions such as the anterior cingulate, insula, amygdala and supramarginal gyrus may contribute to difficulties in emotional regulation. Beyond this inhibitory control – emotional regulation dichotomy, there are other psychological impairments that may be associated with gray matter alterations. For example, difficulties in memory monitoring may be sustained by shape and volumetric alterations in the dorso-lateral prefrontal cortex and the hippocampus. Additionally, visual-spatial impairments may be explained by gray matter shape and volume alterations in the superior parietal and occipital lobes as well as the precuneus. Overall the research confirms changes in volume and shape in multiple cortical and subcortical regions which can help to explain the complexity of OCD symptomatology and the diversity of OCD endophenotypes. Additionally, the evidence from brain shape anomalies may suggest the additional possibility of neurodevelopmental changes associated with the pathogenesis of OCD.

Inhibitory control and traumatic brain injury: The association between executive control processes and social communication deficits

Primary objective: To further examine the proposed relationship between executive impairments in inhibitory control and social communication difficulties reflecting poor inhibition following TBI.Method: Inhibitory control was assessed in 14 adults with TBI on the Hayling Sentence Completion Test (HSCT). Errors on Part B (failed inhibition) and Part B-Part A response latencies (delayed inhibition) were examined. A relative, friend or frequent communication partner of each participant with TBI completed the La Trobe Communication Questionnaire (LCQ) on the communication difficulties of the person with TBI. The Inhibitory Control Factor (ICF) score of the LCQ based on seven items relating to poor inhibition was specifically analysed against performance on the HSCT.Results: Multiple regression analysis indicated that 58% (51% adjusted) of the variance in LCQ ICF scores was accounted for by measures on the HSCT. Only B–A response latencies on the HSCT explained a significant proportion of the variability in LCQ ICF scores.Conclusions: Reduced inhibition speed may more strongly contribute to disinhibited communication behaviours than failures in inhibition. These findings contribute to understanding of the cognitive processes underlying social communication and have the potential to support and inform the use and development of management practices for individuals following TBI.

ADHD symptoms in non-treatment seeking young adults: relationship with other forms of impulsivity.

Attention-deficit hyperactivity disorder (ADHD) has been associated with various manifestations of impulsivity in adults, including elevated rates of other impulsive disorders, substance use, questionnaire-based impulsivity scores, and inhibitory dysregulation on neurocognitive tests. The relationship between ADHD and all these other forms of impulsivity has yet to be explored within the context of a single comprehensive study. A total of 423 young adults, who gambled ≥5 times in the preceding year, were recruited using media advertisements and undertook detailed assessment including structured psychiatric interview, questionnaires, and neurocognitive tests. Participants with ADHD symptoms were identified using the Adult ADHD Self-Report Scale Screener (ASRS-V1.1) and were compared to controls using multivariate analysis of variance (MANOVA). ADHD symptoms were found in 20.3% of the sample, but only 7.3% of these subjects had ever received a formal diagnosis. ADHD symptoms were associated with significantly lower quality of life, lower self-esteem, higher emotional dysregulation, higher impulsivity questionnaire scores, more problematic Internet use, greater occurrence of psychiatric disorders, and impaired stop-signal reaction times. Of these variables, stop-signal reaction times and Barratt attentional impulsiveness were the strongest predictors of group classification. ADHD symptoms are common and under-diagnosed in young adults who gamble, and are most strongly linked with certain other types of impulsivity (questionnaire- and cognitive-based measures) and with emotional dysregulation, suggesting that these are each important considerations in understanding the pathophysiology of the disorder, but also potential treatment targets. It is necessary to question whether treatment for adult ADHD could be enhanced by considering self-esteem, emotional reactivity, and impaired inhibitory control as specific treatment targets, in addition to the core diagnostic symptoms of the disorder.

Neural signature of behavioural inhibition in women with bulimia nervosa.

Impaired inhibitory control is considered a behavioural phenotype in patients with bulimia nervosa. However, the underlying neural correlates of impaired general and food-specific behavioural inhibition are largely unknown. Therefore, we investigated brain activation during the performance of behavioural inhibition to general and food-related stimuli in adults with bulimia nervosa. Women with bulimia and healthy control women underwent event-related fMRI while performing a general and a food-specific no-go task. We included 28 women with bulimia nervosa and 29 healthy control women in our study. On a neuronal level, we observed significant group differences in response to general no-go stimuli in women with bulimia nervosa with high symptom severity; compared with healthy controls, the patients showed reduced activation in the right sensorimotor area (postcentral gyrus, precentral gyrus) and right dorsal striatum (caudate nucleus, putamen). The present results are limited to adult women with bulimia nervosa. Furthermore, it remains unclear whether impaired behavioural inhibition in patients with this disorder are a cause or consequence of chronic illness. Our findings suggest that diminished frontostriatal brain activation in patients with bulimia nervosa contribute to the severity of binge eating symptoms. Gaining further insight into the neural mechanisms of behavioural inhibition problems in individuals with this disorder may inform brain-directed treatment approaches and the development of response inhibition training approaches to improve inhibitory control in patients with bulimia nervosa. The present study does not support greater behavioural and neural impairments to food-specific behavioural inhibition in these patients.

Air pollution exposure during pregnancy and brain morphology in young children: a population-based prospective birth cohort study

Background: Increasing evidence indicates that air pollution exposure during pregnancy is related to impaired child neuropsychological development. However, it is unclear if brain structural alterations underlie this association. Therefore, we aimed to assess whether air pollution exposure during pregnancy is related to brain morphology in young children. Methods: Population-based birth cohort set up in Rotterdam, The Netherlands (2002-2006). Air pollution levels at birth addresses were estimated by land-use or dispersion models based on monitoring campaigns done between 2008 and 2010. Levels were extrapolated back in time to the pregnancy period using routine background monitoring network. Structural neuroimaging, diffusion tensor imaging, and neuropsychological assessment using NEPSY-II were performed at age 8 years (n=783). Results: Air pollution levels were not associated with global brain volumes or white matter microstructure. Conversely, children exposed to PM2.5, PMcoarse, PM2.5absorbance, and benzo(a)pyrene (BaP) during pregnancy had thinner cortices in several brain regions particularly in the frontal lobe, after adjusting for child’s sex, age, IQ, and parental socioeconomic and life-style characteristics. Specifically, PM2.5 and BaP levels were associated with a reduced cortical thickness of the rostral middle frontal and praecuneus regions, and PM2.5 levels during pregnancy were related to the pars orbitalis region. PM2.5 and BaP levels were associated with an impaired worse inhibitory control of the children, while a reduced cortical thickness of the regions related to these pollutants was also associated with an impaired inhibitory control. Conclusions: Our results suggested that air pollution exposure during pregnancy is associated with a reduced cortical thickness in several brain regions, particularly in the frontal lobe. Both the exposure and the regions with reduced cortical thickness were related to an impaired inhibitory control in children.

Examining the interaction between cognitive control and reward sensitivity in substance use dependence

BackgroundDrug dependence is characterized by altered reward processing and poor cognitive control, expressed as a preference for immediate rewards and impaired inhibitory control, respectively. To examine the interaction between reward processing (via the presence or absence of reward) and mechanisms of inhibitory control in drug dependence, the current study used the Monetary Incentive Control Task (MICT) to examine whether a group of opiate dependent persons demonstrated greater difficulty exerting control over immediate rewards compared to neutral stimuli. MethodsThe MICT is a Go/Stop paradigm that examines inhibitory control over immediate rewards. Performance of 32 opiate dependent individuals was compared to 29 healthy controls. ResultsOpiate users demonstrated poorer inhibitory performance than controls, irrespective of cues signaling immediate reward. Whereas control participants’ responses were modulated by probability cues, the opiate group did not show a capacity to up-regulate their cognitive control performance. ConclusionsThe present results suggest a general decrease in cognitive control in opiate dependence, accompanied by a reduced ability to optimally modulate behavior in accordance with external cues. Opiate users and controls did not differ in the interaction between cognitive control and reward. The study highlights important issues for future research to consider when further examining this interaction in drug dependence.

Auditory top-down control and affective theory of mind in schizophrenia with and without hallucinations

Social cognitive impairments may represent a core feature of schizophrenia and above all are a strong predictor of positive psychotic symptoms. Previous studies could show that reduced inhibitory top-down control contributes to deficits in theory of mind abilities and is involved in the genesis of hallucinations. The current study aimed to investigate the relationship between auditory inhibition, affective theory of mind and the experience of hallucinations in patients with schizophrenia. In the present study, 20 in-patients with schizophrenia and 20 healthy controls completed a social cognition task (the Reading the Mind in the Eyes Test) and an inhibitory top-down Dichotic Listening Test. Schizophrenia patients with greater severity of hallucinations showed impaired affective theory of mind as well as impaired inhibitory top-down control. More dysfunctional top-down inhibition was associated with poorer affective theory of mind performance, and seemed to mediate the association between impairment to affective theory of mind and severity of hallucinations. The findings support the idea of impaired theory of mind as a trait marker of schizophrenia. In addition, dysfunctional top-down inhibition may give rise to hallucinations and may further impair affective theory of mind skills in schizophrenia.

Testing differential susceptibility: Plasticity genes, the social environment, and their interplay in adolescent response inhibition

Objectives: Impaired inhibitory control is a key feature of attention-deficit/hyperactivity disorder (ADHD). We investigated gene–environment interaction (GxE) as a possible contributing factor to response inhibition variation in context of the differential susceptibility theory. This states individuals carrying plasticity gene variants will be more disadvantaged in negative, but more advantaged in positive environments.Methods: Behavioural and neural measures of response inhibition were assessed during a Stop-signal task in participants with (N = 197) and without (N = 295) ADHD, from N = 278 families (age M = 17.18, SD =3.65). We examined GxE between candidate plasticity genes (DAT1, 5-HTT, DRD4) and social environments (maternal expressed emotion, peer affiliation).Results: A DRD4 × Positive peer affiliation interaction was found on the right fusiform gyrus (rFG) activation during successful inhibition. Further, 5-HTT short allele carriers showed increased rFG activation during failed inhibitions. Maternal warmth and positive peer affiliation were positively associated with right inferior frontal cortex activation during successful inhibition. Deviant peer affiliation was positively related to the error rate.Conclusions: While a pattern of differential genetic susceptibility was found, more clarity on the role of the FG during response inhibition is warranted before firm conclusions can be made. Positive and negative social environments were related to inhibitory control. This extends previous research emphasizing adverse environments.

Transcranial Direct Current Stimulation Over the Right Frontal Inferior Cortex Decreases Neural Activity Needed to Achieve Inhibition: A Double-Blind ERP Study in a Male Population.

Inhibitory control refers to the ability to inhibit an action once it has been initiated. Impaired inhibitory control plays a key role in triggering relapse in some pathological states, such as addictions. Therefore, a major challenge of current research is to establish new methods to strengthen inhibitory control in these "high-risk" populations. In this attempt, the right inferior frontal cortex (rIFC), a neural correlate crucial for inhibitory control, was modulated using transcranial direct current stimulation (tDCS). Healthy participants (n = 31) were presented with a "Go/No-go" task, a well-known paradigm to measure inhibitory control. During this task, an event-related potential (ERP) recording (T1; 32 channels) was performed. One subgroup (n = 15) was randomly assigned to a condition with tDCS (anodal electrode was placed on the rIFC and the cathodal on the neck); and the other group (n = 16) to a condition with sham (placebo) tDCS. After one 20- minute neuromodulation session, all participants were confronted again with the same ERP Go/No-go task (T2). To ensure that potential tDCS effects were specific to inhibition, ERPs to a face-detection task were also recorded at T1 and T2 in both subgroups. The rate of commission errors on the Go/No-go task was similar between T1 and T2 in both neuromodulation groups. However, the amplitude of the P3d component, indexing the inhibition function per se, was reduced at T2 as compared with T1. This effect was specific for participants in the tDCS (and not sham) condition for correctly inhibited trials. No difference in the P3 component was observable between both subgroups at T1 and T2 for the face detection task. Overall, the present data indicate that boosting the rIFC specifically enhances inhibitory skills by decreasing the neural activity needed to correctly inhibit a response.