Linking impulsivity and inhibitory control using manual and oculomotor response inhibition tasks

The antisaccadic paradigm: A complementary neuropsychological tool in basal ganglia disorders

This review explores the role of the antisaccadic task in understanding inhibitory mechanisms in basal ganglia disorders. It conducts a comparative analysis of saccadic profiles in conditions such as Parkinson's disease, Tourette syndrome, obsessive-compulsive disorder, Huntington's disease, and dystonia, revealing distinct patterns and proposing mechanisms for impaired performance. The primary focus is on two inhibitory mechanisms: global, pre-emptive inhibition responsible for suppressing prepotent responses, and slower, selective response inhibition. The antisaccadic task demonstrates practicality in clinical applications, aiding in differential diagnoses, treatment monitoring and reflecting gait control. To further enhance its differential diagnostic value, future directions should address issues such as the standardization of eye-tracking protocol and the integration of eye-tracking data with other disease indicators in a comprehensive dataset.

Assessing Inhibitory Control Deficits in Adult ADHD: A Systematic Review and Meta-analysis of the Stop-signal Task

In recent years, there has been an increasing quest in improving our understanding of the neurocognitive deficits underlying adult attention-deficit/hyperactivity disorder (ADHD). Current statistical manuals of psychiatric disorders emphasize inattention and hyperactivity-impulsivity symptoms, but empirical studies have also shown consistent alterations in inhibitory control. To date, there is no established neuropsychological test to assess inhibitory control deficits in adult ADHD. A common paradigm for assessing response inhibition is the stop-signal task (SST). Following PRISMA-selection criteria, our systematic review and meta-analysis integrated the findings of 26 publications with 27 studies examining the SST in adult ADHD. The meta-analysis, which included 883 patients with adult ADHD and 916 control participants, revealed reliable inhibitory control deficits, as expressed in prolonged SST response times, with a moderate effect size g = 0.51 (95% CI: 0.376-0.644, p < 0.0001). The deficits were not moderated by study quality, sample characteristics or clinical parameters, suggesting that they may be a phenotype in this disorder. The analyses of secondary outcome measures revealed greater SST omission errors and reduced go accuracy in patients, indicative of altered sustained attention. However, only few (N < 10) studies were available for these measures. Our meta-analysis suggests that the SST, in conjunction with other tests and questionnaires, could become a valuable tool for assessing inhibitory control deficits in adult ADHD.

Neural differences of food-specific inhibitory control in people with healthy vs higher BMI

Consistent with the idea that deficits in inhibition limit resistance to tempting, tasty, high-calorie foods, and might result in a higher BMI, we test whether people with higher BMIs (BMI >25 kg/m²) present inefficient inhibitory control over food-related responses. To unpack this association, we also examine individual differences in the neural mechanisms of food inhibitory control in healthy vs higher BMI individuals. We test these aspects with a sample of 109 participants (49 with higher BMI and 60 with healthy BMI) and the food stop-signal task, which was used to examine individuals' inhibitory control. Results demonstrated that people with higher BMI had significantly poorer food inhibitory control than healthy BMI individuals. fMRI results showed that, in both Go (Go_food vs Go_nature) and Stop conditions (Stop_food vs Stop_nature), compared to healthy BMI individuals, individuals with higher BMI had lower activation in the superior frontal gyrus, precuneus, precentral gyrus, and supramarginal gyrus in the food stimulus condition. Moreover, ROI analysis results showed that under the Stop_food condition, the activation in the inferior frontal gyrus in the higher BMI group was significantly negatively correlated with inhibitory control abilities. These results suggest that people with a higher BMI have limited ability to inhibit food impulsions, and that the prefrontal regions and parietal cortex may contribute to the progression of inhibitory control limitations in relation to food.

Both reactive and proactive control are deficient in children with ADHD and predictive of clinical symptoms

Cognitive control deficits are a hallmark of attention deficit hyperactivity disorder (ADHD) in children. Theoretical models posit that cognitive control involves reactive and proactive control processes but their distinct roles and inter-relations in ADHD are not known, and the contributions of proactive control remain vastly understudied. Here, we investigate the dynamic dual cognitive control mechanisms associated with both proactive and reactive control in 50 children with ADHD (16F/34M) and 30 typically developing (TD) children (14F/16M) aged 9-12 years across two different cognitive controls tasks using a within-subject design. We found that while TD children were capable of proactively adapting their response strategies, children with ADHD demonstrated significant deficits in implementing proactive control strategies associated with error monitoring and trial history. Children with ADHD also showed weaker reactive control than TD children, and this finding was replicated across tasks. Furthermore, while proactive and reactive control functions were correlated in TD children, such coordination between the cognitive control mechanisms was not present in children with ADHD. Finally, both reactive and proactive control functions were associated with behavioral problems in ADHD, and multi-dimensional features derived from the dynamic dual cognitive control framework predicted inattention and hyperactivity/impulsivity clinical symptoms. Our findings demonstrate that ADHD in children is characterized by deficits in both proactive and reactive control, and suggest that multi-componential cognitive control measures can serve as robust predictors of clinical symptoms.

A critical review of the relationship between type 1 diabetes mellitus, inhibition, and behavioral management

Type 1 diabetes mellitus (T1DM) is a chronic and lifelong condition that requires adequate behavior management in order to meet desired health outcomes. The effects of T1DM on the neurocognitive functioning of affected individuals raise concerns about how the disease may influence executive functioning. Inhibition is a core component of executive functioning, and plays a vital role in self-regulation and the restriction of impulsive behaviors. Inhibition may thus play a vital role in the behavior management of people with T1DM. The aim of this study was to identify current gaps in existing knowledge regarding the relationship between T1DM, inhibition, and behavior management. This study employed a critical review design to analyze and synthesize the current scientific literature. Twelve studies were identified through an appraisal process, and the data extracted were thematically analyzed and integrated. The findings of this study indicate that a possible cycle arises between these three constructs, in which T1DM affects inhibition, inhibition affects behavior management, and poor behavior management affects inhibition. It is recommended that future research should focus more specifically on this relationship.

Is history of abuse predictive of eating disorders with binge-eating episodes through an effect mediated by impulsivity? A French longitudinal study

BACKGROUND

In recent years, many studies have explored the associations among impulsivity, history of abuse, the emergence of eating disorders with episodes of binge eating (EDBE) and their severity. Nevertheless, factors associated with successful clinical outcomes of EDBE are still unknown. Our study aimed to test the hypothesis that a history of abuse is associated with unsuccessful clinical outcomes of EDBE through an effect mediated by impulsivity.

METHODS

We assessed patients older than 15 years, 3 months with EDBE at inclusion and at 1 year. Recovery was defined as the absence of eating disorders at 1 year. A mediation analysis was performed by means of structural equation modelling.

RESULTS

We included 186 patients in our analyses (54% bulimia nervosa, 29% anorexia nervosa binge eating/purging type and 17% binge-eating disorder); 179 (96%) were female. One-third (n = 63) of patients reported a history of abuse, and recovery was observed for 20% of the sample (n = 38). Contrary to our assumption, a history of abuse was not associated with the absence of recovery of EDBE at 1 year. Factors unfavourable for achieving recovery were anxiety disorders (odds ratio [OR] 0.41), vomiting (OR 0.39), physical hyperactivity (OR 0.29), negative urgency and a lack of perseverance (OR 0.85 for both). Only positive urgency was positively associated with recovery (OR 1.25).

LIMITATIONS

We excluded 219 patients lost to the 1-year follow-up.

CONCLUSION

Our findings may help to deconstruct the empirical belief that traumatic events may interfere with the successful course of treatment for eating disorders. A high level of positive urgency may be associated with more receptivity to care.

Ignore the glitch but mind the switch: Positive effects of methylphenidate on cognition in attention deficit hyperactivity disorder are related to prediction gain

Neuropsychological symptoms such as inattention and distractibility constitute a core characteristic of attention deficit hyperactivity disorder (ADHD). Here, we tested the hypothesis that attentional dysfunctions result from a deficit in neural gain modulation, which translates into difficulty in predictively weighting relevant sensory input while ignoring distraction. We compared thirty-seven hitherto untreated adults diagnosed with ADHD and thirty-eight healthy participants with a serial switch-drift task that requires internal models of predictable digit sequences to be either updated or stabilized. Switches between sequences that had to be indicated by key presses and digit omissions within a sequence (drifts) that should be ignored varied by stimulus-bound surprise quantified as Shannon information. To investigate whether catecholaminergic modulation by increasing extracellular norepinephrine and dopamine levels leads to an amelioration in prediction gain, participants were tested twice, with patients receiving a single dose of methylphenidate, a norepinephrine/dopamine reuptake inhibitor, in the second session. Patients and controls differed in both updating and stabilizing, depending on the respective event surprise. Specifically, patients showed difficulty in detecting expectable switches, while having greater difficulty to ignore surprising distractions. Thus, underconfident prior beliefs in ADHD may fail to appropriately weight expected relevant input, whereas the gain of neural responses to unexpected irrelevant distractors is increased. Methylphenidate improved both flexibility and stability of prediction and had a positive effect on selective responding over time. Our results suggest that ADHD is associated with an impairment in the use of prior expectations to optimally weight sensory inputs, which is improved by increasing catecholaminergic neurotransmission.

The Eyes Have It: A Meta-analysis of Oculomotor Inhibition in Attention-Deficit/Hyperactivity Disorder

BACKGROUND

Diminished inhibitory control is one of the main characteristics of attention-deficit/hyperactivity disorder (ADHD), and impairments in oculomotor inhibition have been proposed as a potential biomarker of the disorder. The present meta-analysis summarizes the effects reported in studies comparing oculomotor inhibition in ADHD patients and healthy control subjects.

METHODS

Inhibitory outcomes were derived from oculomotor experimental paradigms including the antisaccade (AS), memory-guided saccade, and prolonged fixation tasks. Temporal and spatial measures were also extracted from these tasks and from visually guided saccade tasks as secondary outcomes. Data were available from k = 31 studies (N = 1567 participants). Summary effect sizes were computed using random-effects models and a restricted maximum-likelihood estimator.

RESULTS

Among inhibitory outcomes, direction errors in AS, after correcting for publication bias, showed a moderate effect and large between-study heterogeneity (k = 18, n = 739, g = 0.57, 95% confidence interval [CI] [0.27, 0.88], I²= 74%); anticipatory saccades in memory-guided saccade showed a large effect and low heterogeneity (k = 11, n = 487; g = 0.86, 95% CI [0.64, 1.08], I² = 17.7%); and saccades during prolonged fixation evidenced large effect size and heterogeneity (k = 6, n = 325 g = 1.11, 95% CI [0.56, 1.65], I² = 79.1%) partially related to age. Among secondary outcomes, saccadic reaction time in AS (k = 22, n = 932, g = 0.34, 95% CI [0.06, 0.63], I² = 53.12%) and coefficient of variability in visually guided saccade (k = 5, n = 282, g = 0.53, 95% CI [0.28, 0.78], I² = 0.01%) indicated significant effects with small to moderate effects sizes.

CONCLUSIONS

ADHD groups commit more oculomotor inhibition failures than control groups. The substantial effects support the conclusion that oculomotor disinhibition is a relevant ADHD-related mechanism. Moderate effects observed in saccadic reaction time variability suggest that fluctuant performance in oculomotor tasks is another relevant characteristic of ADHD.

Executive dysfunction in affective disorders: differences in bipolar affective disorder and depressive episode

Aim. To identify the differences in executive function (inhibitory control, working memory, cognitive flexibility) between patients with bipolar affective disorder and depressive episode.

Materials and methods. A total of 72 patients with affective disorders aged 20–40 years were examined. Of them, 30 patients had bipolar affective disorder, a current episode of mild or moderate depression, and 42 patients had a mild, moderate, and severe depressive episode without symptoms of psychosis. The executive function was evaluated using PsyToolkit, a set of software tools for programming psychological experiments. Computerized Go/ No–go tasks (assessment of inhibitory control and psychomotor functions), the Corsi block-tapping test (assessment of visual and spatial working memory capacities), and the Stroop Color and Word Test (assessment of cognitive flexibility) were used.

Results. An intergroup comparison of patients revealed that patients with bipolar disorder significantly more often demonstrated false button press in the Go/No–go task (p = 0.043); however, they exhibited a greater working memory capacity in the Corsi block-tapping test (p = 0.049) compared with patients with a depressive episode.

Conclusion. Important data were obtained regarding the specifics of executive dysfunction depending on the type of affective disorder. The presented data expand and supplement available information about the cognitive characteristics of patients with bipolar affective disorder and depressive episode, which may be useful in clinical practice and serve a focus of future research.

Maladaptive Personality Traits in a Group of Patients with Substance Use Disorder and ADHD

Background and Objectives: the comorbidity of personality disorders in patients who use psychoactive substances is common in psychiatric practice. The epidemiology of disharmonious personality traits in patients with ADHD and addictions in adulthood is still insufficiently researched. The study investigated the typology of personality traits in a group of adult patients consuming psychoactive substances, in whom symptoms of ADHD were identified. Materials and Methods: the study evaluates a group of 104 patients with chronic psychoactive substances abuse, in whom symptoms of ADHD were identified in early adulthood, in terms of comorbid personality traits. Results: statistically significant data have been obtained regarding the presence of clinical traits characteristic for cluster B personality disorders, the patients presenting lower levels of self-control, self-image instability, difficulties in the areas of social relationships and own identity integration. Conclusions: ADHD symptomatology precedes the clinical traits of personality disorders in patients with addictions, negatively influencing chronic evolution and quality of life.

Eye Tracking During a Continuous Performance Test: Utility for Assessing ADHD Patients

OBJECTIVE

The use of continuous performance tests (CPTs) for assessing ADHD related cognitive impairment is ubiquitous. Novel psychophysiological measures may enhance the data that is derived from CPTs and thereby improve clinical decision-making regarding diagnosis and treatment. As part of the current study, we integrated an eye tracker with the MOXO-dCPT and assessed the utility of eye movement measures to differentiate ADHD patients and healthy controls.

METHOD

Adult ADHD patients and gender/age-matched healthy controls performed the MOXO-dCPT while their eye movements were monitored (n = 33 per group).

RESULTS

ADHD patients spent significantly more time gazing at irrelevant regions, both on the screen and outside of it, than healthy controls. The eye movement measures showed adequate ability to classify ADHD patients. Moreover, a scale that combined eye movement measures enhanced group prediction, compared to the sole use of conventional MOXO-dCPT indices.

CONCLUSIONS

Integrating an eye tracker with CPTs is a feasible way of enhancing diagnostic precision and shows initial promise for clarifying the cognitive profile of ADHD patients. Pending replication, these findings point toward a promising path for the evolution of existing CPTs.

Measuring the Impact of Bilingualism on Executive Functioning Via Inhibitory Control Abilities in Autistic Children

One factor that may influence how executive functions develop is exposure to more than one language in childhood. This study explored the impact of bilingualism on inhibitory control in autistic (n = 38) and non-autistic children (n = 51). Bilingualism was measured on a continuum of exposure to investigate the effects of language environment on two facets of inhibitory control. Behavioural control of motor impulses was modulated positively through increased bilingual exposure, irrespective of diagnostic status, but bilingual exposure did not significantly affect inhibition involving visual attention. The results partially support the hypothesis that bilingual exposure differentially affects components of inhibitory control and provides important evidence for families that bilingualism is not detrimental to their development.

Cognitive characterization of adult attention deficit hyperactivity disorder by domains: a systematic review

Attention deficit hyperactivity disorder (ADHD) is reportedly the most frequent neurodevelopmental disorder diagnosed during childhood, and it is recognized as a common condition in adulthood. We review the evidence to help identify cognitive domains associated to deficits in adult ADHD. A systematic review with narrative synthesis was performed, assessing studies on adult ADHD, neuropsychology and research on involved cognitive domains in adults 18+ years old with an established diagnosis of ADHD, in seven electronic databases (PubMed, PsychInfo, WebOfScience, Embase, Scopus, OvidSPMedline, and Teseo), and Worldcat and OpenGrey grey literature databases. 93 studies were included for this review, encompassing findings from a total 5574 adults diagnosed only with ADHD, medication-naïve or non-medicated at the moment of the assessment and 4880 healthy controls. Adults diagnosed with ADHD may show, when compared to healthy controls, a cognitive profile characterized by deficits across all attention modalities, processing speed, executive function (mainly working memory and inhibition with emphasis on reward delay and interference control), verbal memory, reading skills, social cognition and arithmetic abilities. A cognitive characterization of adult ADHD by domains is established beyond the sole consideration of attention and executive function problems. Along with these, verbal memory, language (mainly reading), social cognition and arithmetic abilities may also contribute to a more comprehensive characterization of the cognitive profile in adult ADHD.

Brain networks associated with anticipatory postural adjustments in Parkinson's disease patients with freezing of gait

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High hemodynamic response in the AI and SMA in the FoG when an APA was required.

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Connectivity between the right and left insulae was correlated with severity of FoG.

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Both groups showed different brain network organizations between SMA and bilateral AI.

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SMA was found to be a hub in patients with FoG when an APA was required.

Specific impairments of anticipatory postural adjustment (APA) during step initiation have been reported in patients with Parkinson’s disease (PD) and freezing of gait (FoG). Although APA disruption has been associated with FoG, there is scarce knowledge about its neural correlates. We sought to better understand the neural networks involved with APA in patients with FoG by assessing the level of hemodynamic response of specific brain regions and the functional connectivity during the leg lifting task. In the current investigation, APAs of patients with PD, with and without (nFoG) freezing were assessed during a leg lifting task in an event-related, functional magnetic resonance imaging (er-fMRI) protocol. Results identified a high hemodynamic response in the right anterior insula (AI) and supplementary motor area (SMA) in the FoG group when an APA was required. The nFoG had stronger connectivity between the right and left insulae than the FoG group. The strength of this connectivity was negatively correlated with the severity of FoG. Both groups showed different brain network organizations comprising the SMA and the bilateral AI. The SMA was found to be a hub in patients with FoG when an APA was required for the task. Our findings suggest that both groups used compensatory mechanism comprising the insulae during APA. Neither group used the entire network comprised of the insulae and SMA to accomplish the task. The FoG group relied more on SMA as a hub than as part of a broader network to exchange information during the APA.

Aging Modulates Prefrontal Plasticity Induced by Executive Control Training

While declines in inhibitory control, the capacity to suppress unwanted neurocognitive processes, represent a hallmark of healthy aging, whether this function is susceptible to training-induced plasticity in older populations remains largely unresolved. We addressed this question with a randomized controlled trial investigating the changes in behavior and electrical neuroimaging activity induced by a 3-week adaptive gamified Go/NoGo inhibitory control training (ICT). Performance improvements were accompanied by the development of more impulsive response strategies, but did not generalize to impulsivity traits nor quality of life. As compared with a 2-back working-memory training, the ICT in the older adults resulted in a purely quantitative reduction in the strength of the activity in a medial and ventrolateral prefrontal network over the 400 ms P3 inhibition-related event-related potentials component. However, as compared with young adults, the ICT induced distinct configurational modifications in older adults' 200 ms N2 conflict monitoring medial-frontal functional network. Hence, while older populations show preserved capacities for training-induced plasticity in executive control, aging interacts with the underlying plastic brain mechanisms. Training improves the efficiency of the inhibition process in older adults, but its effects differ from those in young adults at the level of the coping with inhibition demands.

Beyond Their HIV Status: the Occurrence of Multiple Health Risk Behavior Among Adolescents from a Rural Setting of Sub-Saharan Africa

Background

Health risk behaviors during adolescence may cluster into patterns that might be predicted by specific factors, among which HIV may have an important role.

Method

In a cross-sectional study conducted between 2017 and 2018, clustering of HRB and its associated factors was investigated in rural Kenya among 588 adolescents (36% perinatally HIV infected; 28% perinatally HIV exposed but uninfected; and 36% HIV unexposed/uninfected). Latent class analysis of 22 behaviors followed by multinomial logistic regression were conducted. Four risk behavior classes were identified.

Results

No significant differences were found in behavioral class membership across the three HIV groups (p = 0.366). The risk of membership to the higher risk behavioral classes relative to class 1 (the substance and drug abstinent low risk takers) increased with older adolescent age (p = 0.047), increased among adolescent who experienced mental distress (p < 0.001), and those who felt unsafe in their neighborhood (p < 0.002). Better working memory (p = 0.0037) was found to be protective.

Conclusion

The results highlight a need to include screening and interventions for internalizing mental health problems and deficits in executive functioning, as well as steps to involve family members and communities to address psychosocial risk factors in adolescents in Kenya.

Trait impulsiveness and response inhibition in young adults: Moderating role of resting respiratory sinus arrhythmia

Trait impulsiveness is a multifaceted construct that includes motor-, attention/cognitive- and non-planning facets, but how specific impulsiveness facets are associated with the deficit of response inhibition is not well understood. Resting respiratory sinus arrhythmia (RSA), which is considered as an index of cardiac vagal tone has been demonstrated to play a moderating role in the associations between many individual's variables. Whether resting RSA moderates the relationships between the facets of trait impulsiveness and response inhibition remains unknown. To examine these issues, data of self-reported trait impulsiveness, as assessed using the Barratt Impulsiveness Scale (BIS-II), 5-min resting RSA, and response accuracy (ACC) on a modified Go/NoGo task were collected from 132 college students. Results indicated that ACC of NoGo condition on the Go/NoGo task was negatively correlated with BIS motor and BIS total. Trait motor impulsiveness negatively predicted ACC of NoGo condition on the Go/NoGo task in the low resting RSA group but not in the high resting RSA group. This finding suggests that cardiac vagal tone could moderate the association between trait impulsiveness, especially motor impulsiveness, and deficits of response inhibition.

Working Memory and Response Inhibition Effects on At-Risk Youth's Willingness to Use Multiple Nicotine and Tobacco Products

Purpose: Past research has suggested that executive functions, such as working memory and response inhibition, predict the use of nicotine and tobacco products (NTPs). The current study extends prior research by assessing whether response inhibition and working memory are associated with at-risk youth's willingness to use NTPs. Methods: A sample of 1060 at-risk youth were recruited from alternative high schools in southern California. Participants were randomly assigned to complete the Symmetry Span Task, an indicator of working memory ability, or the cued Go/No-Go task, an indicator of response inhibition. Participants who reported never using NTPs (n = 348) indicated how willing they would be try NTPs. Results: Results from a cross-sectional zero-inflated negative binomial (ZINB) regression suggest that females with stronger working memory skills and individuals with weaker response inhibition skills were more likely to be unwilling to use NTPs. Conclusion: While further research is needed to determine whether executive functions can prospectively predict NTP use among at-risk youth, the current study indicates that both working memory and response inhibition may play a significant role.

Effects of multisensory stop signals on alcohol-induced disinhibition in adults with ADHD

Multisensory environments facilitate behavioral functioning in humans. The redundant signal effect (RSE) refers to the observation that individuals respond more quickly to stimuli when information is presented as multisensory, redundant stimuli (e.g., aurally and visually) rather than as a single stimulus presented to either modality alone. RSE appears to be because of specialized multisensory neurons in the superior colliculus and association cortex that allow intersensory coactivation between the visual and auditory channels. Our studies show that the disinhibiting effects of alcohol are attenuated when stop signals are multisensory (e.g., Visual + Auditory stop signals) versus unisensory (Roberts, Monem, & Fillmore, 2016). The present study expanded on this research to test the degree to which multisensory stop signals could also attenuate the disinhibiting effects of alcohol in those with attention-deficit hyperactivity disorder (ADHD), a clinical population characterized by poor impulse control. The study compared young adults with ADHD (n = 22) with healthy controls (n = 22) and examined the acute impairing effect of alcohol on response inhibition to stop signals that were presented as a unisensory (visual) stimulus or a multisensory (Visual + Auditory) stimulus. For controls, results showed alcohol impaired response inhibition to unisensory stop signals but not to multisensory stop signals. Response inhibition of those with ADHD was impaired by alcohol regardless of whether stop signals were unisensory or multisensory. The failure of multisensory stimuli to attenuate alcohol impairment in those with ADHD highlights a specific vulnerability that could account for heightened sensitivity to the disruptive effects of alcohol. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Individual Differences in the Neural Basis of Response Inhibition After Sleep Deprivation Are Mediated by Chronotype

Sleep deprivation (SD) has been reported to severely affect executive function, and interindividual differences in these effects may contribute to the SD-associated cognition impairment. However, it is unclear how individual differences in chronotypes (morning-type, MT; evening-type, ET) influence neurobehavioral functions after SD. To address this question, we used functional magnetic resonance imaging (fMRI) to evaluate whether 24 h of SD differentially affect response inhibition, a core component of executive function, in MT and ET individuals. Accordingly, MT and ET participants were instructed to follow their preferred 7–9-h sleep schedule for 2 weeks at home both prior to and throughout the course of the study, and then performed a go/no-go task during fMRI scanning at 08:00 a.m. both at rested wakefulness (RW) and following SD. We also examined whether the neurobehavioral inhibition differences in the chronotypes in each session can be predicted by subjective ratings (sleepiness, mood, and task) or objective attention. Behaviorally, SD led to an increased response time of go trials (hit RT), more attentional lapses, higher subjective sleepiness, and worse mood indices, but it did not impair the accuracy of go trials (hit rate) and no-go trials (stop rate). Regardless of the presence of SD, ET individuals exhibited a lower stop rate, higher subjective ratings of sleepiness, exhausted mood, and task difficulty in comparison with MT individuals. On the neural level, SD resulted in decreased inhibition-related activation of the right lateral inferior frontal gyrus (rIFG) in MT individuals and increased rIFG activation in ET individuals. Moreover, the rIFG activation in ET individuals after SD was positively correlated to the subjective ratings of sleepiness and effort put into the task, which was considered as a compensatory response to the adverse effects of SD. These findings suggest that individual differences in inhibition-related cerebral activation after SD are influenced by chronotypes. In addition, ET individuals may be vulnerable to response inhibition. Thus, it is essential to take into consideration the chronotype in SD research and sleep medicine.

Reactive and proactive control mechanisms of response inhibition in gambling disorder

Response inhibition, one component of cognitive control, refers to the ability to inhibit automatic responses and has been found to be impaired in gambling disorder. Recent models of cognitive control distinguish between two mechanisms: reactive control, the ability to stop in response to a stop-stimulus, and proactive control, the ability to anticipate and prepare for a stop. Previous studies have primarily focused on reactive modes of control in gambling disorder. The aim of the current study was to assess both reactive and proactive modes of response inhibition in individuals with gambling disorder (n = 27) and community controls (n = 21) using a variant of the stop-signal task. Second, the relationship between trait impulsivity, and reactive and proactive control was examined. No group differences in reactive or proactive control were found. However, premeditation, one domain of trait impulsivity, was associated with worse proactive control in the gambling group. These results suggest that difficulties with response inhibition may not be a core deficit in all forms of gambling disorder. Future research should continue to develop and test tasks that involve cognitive control processes in different presentations of gambling disorder.

Effect of Anodal and Cathodal Transcranial Direct Current Stimulation on DLPFC on Modulation of Inhibitory Control in ADHD

OBJECTIVE

The purpose of this study was to improve the inhibitory control functions through transcranial direct current stimulation (tDCS) in adolescents with ADHD symptoms.

METHOD

Twenty high school students with ADHD symptoms participated in this single-blinded, crossover, sham-controlled study. All the participants were tested during the application of Stroop and Go/No-Go tasks that is used to measure inhibitory control, using 1.5 mA of tDCS for 15 min over the left dorsolateral prefrontal cortex (DLPFC).

RESULTS

Anodal stimulation on left DLPFC had no effect on interference inhibition during the Stroop task and increased the proportion of correct responses in the "Go stage" of the Go/No-Go test compared with sham condition. Cathodal stimulation on the left DLPFC increased the inhibition accuracy in the inhibition stage during Go/No-Go task in comparison with sham.

CONCLUSION

tDCS over the left DLPFC of adolescents who suffer from ADHD symptoms can improve inhibitory control in prepotent response inhibition.

Examining the link between reward and response inhibition in individuals with substance abuse tendencies

BACKGROUND

Substance use problems are often characterized by dysregulation in reward sensitivity and inhibitory control. In line with this representation, the goal of this investigation was to determine how substance abuse tendencies among university students affect incentivized response inhibition. Additionally, this study examined whether striatal dopamine moderates the impact of substance use on response inhibition performance.

METHODS

The sample included ninety-eight university students. Participants completed this prospective experimental study at an on-campus laboratory. All participants completed substance abuse and disinhibition subscales of the Externalizing Spectrum Inventory-Brief Form. Using a within-subjects design, participants then performed the Stop Signal Task under both neutral (unrewarded) and reward conditions, in which correct response cancellations resulted in a monetary reward. Striatal tonic dopamine levels were operationalized using spontaneous eyeblink rate.

RESULTS

The outcome measures were Stop Signal Reaction Time (SSRT) performance in the unrewarded and rewarded phases of the task. A hierarchical linear regression analysis, controlling for trait disinhibition, age, gender, and cigarette smoking status, identified an interactive effect of substance use and striatal dopamine levels on incentivized SSRT. Substance abuse tendencies were associated with slower SSRT and thus poorer inhibitory control under reward conditions among individuals with low levels of striatal dopamine (F = 7.613, p = .007).

CONCLUSIONS

This work has implications for research examining advanced drug use trajectories. In situations in which rewards are at stake, drug users with low tonic dopamine may be more motivated to seek those rewards at the expense of regulating inhibitory control.

Reliability of triggering inhibitory process is a better predictor of impulsivity than SSRT

The ability to control behaviour is thought to rely at least partly on adequately suppressing impulsive responses to external stimuli. However, the evidence for a relationship between response inhibition ability and impulse control is weak and inconsistent. This study investigates the relationship between response inhibition and both self-report and behavioural measures of impulsivity as well as engagement in risky behaviours in a large community sample (N = 174) of healthy adolescents and young adults (15-35 years). Using a stop-signal paradigm with a number parity go task, we implemented a novel hierarchical Bayesian model of response inhibition that estimates stop-signal reaction time (SSRT) as a distribution and also accounts for failures to react to the stop-signal (i.e., "trigger failure"), and failure to react to the choice stimulus (i.e., "go failure" or omission errors). In line with previous studies, the model reduced estimates of SSRT by approximately 100 ms compared with traditional non-parametric SSRT estimation techniques. We found significant relationships between behavioural and self-report measures of impulsivity and traditionally estimated SSRT, that did not hold for the model-based SSRT estimates. Instead, behavioural impulsivity measures were correlated with rate of trigger failure. The relationship between trigger failure and impulsivity suggests that the former may index a higher order inhibition process, whereas SSRT may index a more automatic inhibition process. We suggest that the existence of distinct response inhibition processes that may be associated with different levels of cognitive control.

Impulsive reactivity to emotion and vulnerability to psychopathology

Impulsiveness has been studied as an aspect of personality and psychopathology for generations. There are longstanding disagreements about how to define it and whether it should be viewed as one construct or several. This article begins by briefly reviewing some earlier and some more recent work on impulsiveness. Several approaches have recently converged to focus on a distinction between impulsive reactions to emotion and impulsive properties that are not initiated by emotion. From this review, we turn to psychopathology. It is well known that impulsiveness is related to externalizing psychopathology, but some have concluded that a similar relation does not exist for internalizing psychopathology. A recent literature is described that challenges the latter conclusion, linking impulsive reactivity to emotion to both externalizing and internalizing aspects of psychopathology. Discussion then turns to emotion-related impulsiveness and other constructs to which it is conceptually and empirically related, reexamining whether other conceptual targets should be added to the discussion. The article closes with a consideration of how important it is to continue to remain open to new conceptual perspectives. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Training improves inhibitory control in water rescue dogs

Inhibitory control is a collection of several processes that are aimed to refrain from any impulsive response in the subject during inappropriate situations. Evidence suggests that in dogs, the inhibitory control is affected by domestication process, but also experiences during ontogeny could be an important driver in acquiring inhibitory control. The aim of the study was to compare the performance of highly trained dogs (i.e., water rescue dogs) and pet dogs in the A-not-B task. In this procedure, the animals have to inhibit their urge of going to a previous reinforced place. The results showed that the trained dogs committed fewer errors in the task than the pet dogs suggesting a better inhibitory control. This result could indicate that inhibitory control is a flexible ability affected by ontogenetic processes such as the training experience.

Distinct patterns of blood oxygenation in the prefrontal cortex in clinical phenotypes of schizophrenia and bipolar disorder

BACKGROUND

Schizophrenia (SZ) and bipolar disorder (BD) are characterized by different clinical symptoms, and have previously been considered as categorically separate. However, several lines of evidence controversially suggest that these two disorders may run on a continuum. While it is therefore important to evaluate the subtle differences between SZ and BD, few studies have investigated the difference of brain functioning between the two by focusing on the common symptoms of cognitive functioning and impulsivity, rather than positive/negative and mood symptoms. Recent developments in near-infrared spectroscopy (NIRS) technology have enabled noninvasive assessment of brain function in people with psychiatric disorders.

METHODS

Near-infrared spectroscopy (NIRS) using 24-channels was conducted during the verbal fluency task (VFT) and Stroop color-word task (SCWT) in 38 patients diagnosed with SZ, 34 patients with BD, and 26 age- and sex-matched healthy controls.

RESULTS

Oxyhemoglobin changes in the prefrontal cortex (PFC) were significantly lower particularly in the SZ compared to control group during the VFT. On the other hand, these were significantly lower particularly in the BD and SZ group to control group during the SCWT. Regression analysis showed that hemodynamic changes were significantly correlated with verbal memory and impulsivity in both disorders.

CONCLUSION

These findings suggest that different hemodynamic responses in the prefrontal cortex might reflect cognitive functioning and impulsivity, providing a greater insight into SZ and BD pathophysiology.

Early onset tobacco cigarette smokers exhibit deficits in response inhibition and sustained attention

BACKGROUND

Initiation of cigarette smoking during adolescence coincides with structural and cognitive neuromaturation. Thus, early onset smokers (EOS; initiated <16 years old) may be at unique risk of altered development of executive function relative to late onset smokers (LOS; initiated >16 years old). This study quantified the effects of age of smoking onset on response impulsivity and inhibitory control using a novel smoking Go/NoGo task (Luijten et al., 2011).

METHODS

Nicotine deprived adult EOS (n = 10) and LOS (n = 10) and adult healthy non-smokers (HNS; n = 10) were shown smoking-related and neutral images with either a blue (Go) or yellow (NoGo) frame. Participants were instructed to respond to blue-framed Go trials quickly and accurately, and withhold responding for yellow-framed NoGo trials.

RESULTS

EOS made more Go response accuracy errors (p ≤ 0.02) and failed more frequently to inhibit responses to NoGo trials (p < 0.02) than LOS and HNS. EOS also made more errors in inhibiting responses to smoking-related (p ≤ 0.02) and neutral (p ≤ 0.02) NoGo trials. EOS reported greater baseline craving for cigarette smoking than LOS (p < 0.04), and craving was significantly associated with greater omission errors (p ≤ 0.04).

CONCLUSIONS

EOS exhibited greater difficulty than LOS in responding accurately to Go stimuli and withholding responses to both smoking and neutral NoGo stimuli, indicating greater response impulsivity, poor attention, and deficits in response inhibition. These findings suggest that EO smoking, in particular, contributes to diminished task-related attention and inhibitory control behaviors in adulthood and provide support for the tobacco-induced neurotoxicity of adolescent cognitive development (TINACD) theory (DeBry and Tiffany, 2008).

Impairment of manual but not saccadic response inhibition following acute alcohol intoxication

BACKGROUND

Alcohol impairs response inhibition; however, it remains contested whether such impairments affect a general inhibition system, or whether affected inhibition systems are embedded in, and specific to, each response modality. Further, alcohol-induced impairments have not been disambiguated between proactive and reactive inhibition mechanisms, and nor have the contributions of action-updating impairments to behavioural 'inhibition' deficits been investigated.

METHODS

Forty Participants (25 female) completed both a manual and a saccadic stop-signal reaction time (SSRT) task before and after a 0.8g/kg dose of alcohol and, on a separate day, before and after a placebo. Blocks in which participants were required to ignore the signal to stop or make an additional 'dual' response were included to obtain measures of proactive inhibition as well as updating of attention and action.

RESULTS

Alcohol increased manual but not saccadic SSRT. Proactive inhibition was weakly reduced by alcohol, but increases in the reaction times used to baseline this contrast prevent clear conclusions regarding response caution. Finally, alcohol also increased secondary dual response times of the dual task uniformly as a function of the delay between tasks, indicating an effect of alcohol on action-updating or execution.

CONCLUSIONS

The modality-specific effects of alcohol favour the theory that response inhibition systems are embedded within response modalities, rather than there existing a general inhibition system. Concerning alcohol, saccadic control appears relatively more immune to disruption than manual control, even though alcohol affects saccadic latency and velocity. Within the manual domain, alcohol affects multiple types of action updating, not just inhibition.

Chronotype regulates the neural basis of response inhibition during the daytime

Studies have elucidated the various modulatory effects of chronotype and time-of-day on task-dependent brain activity, but it is unclear how chronotype and time-of-day regulate brain activity in response inhibition tasks. To address this question, we used functional magnetic resonance imaging (fMRI) to explore the effects of chronotype and time-of-day on response inhibition in normal day-night conditions. Morning-type (MT) and evening-type (ET) participants conducted the stop-signal task in morning (08:00-12:00 hours) and evening (19:00-23:00 hours) sessions. The results showed that inhibition-related cerebral responses in the medial frontal gyrus (MFG), middle cingulate cortex (MCC), thalamus and other typical regions for the execution of response inhibition significantly decreased from morning to evening in MT participants, whereas activity in the right inferior frontal gyrus (IFG)/insula, MFG, MCC and thalamus remained stable or increased in ET participants. The chronotypical differences in homeostatic sleep pressure may explain the observed individual differences in maintaining cognition-related cortical activation. These results suggest the importance of considering chronotype and time-of-day in the design and analysis of cognitive neuroscience studies.

Measures of Dogs' Inhibitory Control Abilities Do Not Correlate across Tasks

Inhibitory control, the ability to overcome prepotent but ineffective behaviors, has been studied extensively across species, revealing the involvement of this ability in many different aspects of life. While various different paradigms have been created in order to measure inhibitory control, only a limited number of studies have investigated whether such measurements indeed evaluate the same underlying mechanism, especially in non-human animals. In humans, inhibitory control is a complex construct composed of distinct behavioral processes rather than of a single unified measure. In the current study, we aimed to investigate the validity of inhibitory control paradigms in dogs. Sixty-seven dogs were tested in a battery consisting of frequently used inhibitory control tests. Additionally, dog owners were asked to complete an impulsivity questionnaire about their dog. No correlation of dogs' performance across tasks was found. In order to understand whether there are some underlying behavioral aspects explaining dogs' performance across tests, we performed principle component analyses. Results revealed that three components (persistency, compulsivity and decision speed) explained the variation across tasks. The questionnaire and dogs' individual characteristics (i.e., age and sex) provided only limited information for the derived components. Overall, results suggest that no unique measurement for inhibitory control exists in dogs, but tests rather measure different aspects of this ability. Considering the context-specificity of inhibitory control in dogs and most probably also in other non-human animals, extreme caution is needed when making conclusions about inhibitory control abilities based on a single test.

Longitudinal Visuomotor Development in a Malaria Endemic Area: Cerebral Malaria and Beyond

Paediatric cerebral malaria is the most serious complication of Plasmodium falciparum infection. While the majority recover, long-term cognitive impairment has been highlighted as a significant and neglected problem. Persistent or serious deficits in processes such as attention or behavioural inhibition should be manifest in changes to performance on oculomotor tasks. Therefore we investigated the impact of cerebral malaria on the development of reflexive pro-saccades and antisaccades. In a longitudinal study, 47 children previously admitted with retinopathy-confirmed cerebral malaria (mean age at admission 54 months), were compared with 37 local healthy controls (mean ages at first study visit 117 and 110 months respectively). In each of three or four test sessions, over a period of up to 32 months, participants completed 100 prosaccade tasks and 100 antisaccade tasks. Eye movements were recorded using infrared reflectance oculography; prosaccade, correct antisaccade and error prosaccade latency, and antisaccade directional error rate were calculated. Hierarchical linear modelling was used to investigate the effect of age and the influence of cerebral malaria on these parameters. Data were also collected from an independent, older group (mean age 183 months) of 37 local healthy participants in a separate cross-sectional study. Longitudinal data exhibited the expected decrease in latency with age for all saccade types, and a decrease in the antisaccade directional error rate. Hierarchical linear modelling confirmed that age had a statistically significant effect on all parameters (p< = 0.001). However, there were no statistically significant differences between the cerebral malaria and control groups. Combining groups, comparison with the literature demonstrated that antisaccade directional error rate for the Malawi sample was significantly higher than expected, while latencies for all saccade types were indistinguishable from published. The high directional error rate was also confirmed in the older, healthy Malawian participants from the cross sectional study. Our observation of similar oculomotor performance in cerebral malaria and control groups at long follow-up periods suggests that cerebral malaria survivors are not at a generally increased risk of persistent cognitive deficits. Our data raise questions about the prevailing hypothesis that cerebral malaria has gross impacts on the development of processes such as attention and behavioural inhibition. More importantly, our novel finding of a clear difference in antisaccade performance between all of the Malawi participants and published data suggests that the Malawian paediatric population as a whole faces serious challenges to cognitive development beyond cerebral malaria.

Is previous experience important for inhibitory control? A comparison between shelter and pet dogs in A-not-B and cylinder tasks

This study compares the performance of two groups of dogs with different levels of social interaction with humans, shelter and pet dogs, in two inhibitory control tasks. (1) In the A-not-B task, dogs were required to resist searching for food in a previously rewarded location, and (2) in the cylinder task, dogs were required to resist approaching visible food directly in favor of a detour reaching response. Our first aim was to evaluate the importance of learning and ontogeny in performing inhibitory tasks. Also, we assessed whether there is a correlation between the two tasks by comparing performance in the same subjects. Results showed significant differences between shelter and pet dogs in the A-not-B task, with poorer performance in shelter dogs. However, no differences were found in the cylinder task. The poorer performance of shelter dogs might be related to their infrequent interaction with humans, which reduces the chances to learn to inhibit certain behaviors. This result would highlight the importance of ontogeny in developing that ability. On the other hand, no correlations were found between the two tasks, which contributes information to the debate about the context specificity of inhibitory control in dogs.

Positive urgency is related to difficulty inhibiting prepotent responses

Positive urgency, the tendency to respond impulsively to positive affective states, has been linked to many psychopathologies, but little is known about mechanisms underpinning this form of impulsivity. We examined whether the Positive Urgency Measure (PUM) related to higher scores on performance-based measures of impulsivity and cognitive control that were administered after a positive mood induction. Undergraduates (n = 112) completed the self-report PUM, several positive mood inductions, and behavioral measures of impulsivity and cognitive control. PUM scores were significantly related to poor performance on the antisaccade task, a measure of prepotent response inhibition, but not to other performance measures. Together with existing literature, findings implicate deficits in response inhibition as one mechanism involved in emotion-related impulsivity. (PsycINFO Database Record

Reduced Prefrontal Cortex Hemodynamic Response in Adults with Methamphetamine Induced Psychosis: Relevance for Impulsivity

Patients with methamphetamine abuse/dependence often exhibit high levels of impulsivity, which may be associated with the structural abnormalities and functional hypoactivities observed in the frontal cortex of these subjects. Although near-infrared spectroscopy (NIRS) is a simple and non-invasive method for characterizing the clinical features of various psychiatric illnesses, few studies have used NIRS to directly investigate the association between prefrontal cortical activity and inhibitory control in patients with methamphetamine-induced psychosis (MAP). Using a 24-channel NIRS system, we compared hemodynamic responses during the Stroop color-word task in 14 patients with MAP and 21 healthy controls matched for age, sex and premorbid IQ. In addition, we used the Barrett Impulsivity Scale-11 (BIS-11) to assess impulsivity between subject groups. The MAP group exhibited significantly less activation in the anterior and frontopolar prefrontal cortex accompanied by lower Stroop color-word task performance, compared with controls. Moreover, BIS-11 scores were significantly higher in the MAP group, and were negatively correlated with the hemodynamic responses in prefrontal cortex. Our data suggest that reduced hemodynamic responses in the prefrontal cortex might reflect higher levels of impulsivity in patients with MAP, providing new insights into disrupted inhibitory control observed in MAP.

The Effects of Preresponse Cues on Inhibitory Control and Response Time in Adults With ADHD

OBJECTIVE

The purpose of this study was to examine the effects of preresponse cues on behavioral control in adults with ADHD.

METHOD

Eighty-eight adults with ADHD and 67 adults with no history of ADHD completed a cued go/no-go task. This task requires participants to respond or inhibit a response to go and no-go targets, respectively, and preresponse cues provide participants with predictive information about the upcoming target.

RESULTS

Overall, participants with ADHD made more inhibitory failures and responded more slowly than controls. These group differences were only present in the valid-cue condition, and there were no significant group differences in the invalid-cue conditions.

CONCLUSION

These findings suggest that adults with ADHD are less able to utilize predictive environmental information to facilitate behavioral control.

Modeling Impulsivity in Forensic Patients: A Three-Dimensional Model of Impulsivity

The current study investigated whether a multidimensional model could underlie impulsivity and its associations with various disorders in a forensic sample. Data were available from self-report and behavioral impulsivity instruments of 87 forensic patients. Principal component analysis (PCA) was used to derive a dimensional impulsivity model, and the relationship between and possible predictive validity of impulsivity dimensions for psychopathology was investigated using product moment correlations and regression analysis. A 3-dimensional model of impulsivity was derived, with factors labeled impulsive decision making, sensation seeking, and response inhibition. Impulsive decision making was a predictor for a history of drug dependence, the impulsive lifestyle facet of psychopathy, and antisocial personality disorder. Sensation seeking was not related to any psychopathology. Inadequate response inhibition was a predictor for drug dependence, psychopathy, and antisocial personality disorder. Given the importance of the concept of impulsivity with regard to forensic risk assessment, the current results replicated earlier impulsivity models and imply that impulsivity is a crucial target for diagnosis and interventions and underlines the importance to consider impulsivity as a multidimensional construct.

Response inhibition and interference control in patients with bipolar I disorder and first-degree relatives

OBJECTIVES

The current study aimed to assess both response inhibition (RI) and interference control (IC) in euthymic patients with bipolar disorder (BD-Ps) as well as asymptomatic first-degree relatives (BD-Rs) and healthy controls (HCs) in order to evaluate trait-as opposed to illness-associated features of these components.

METHODS

BD-Ps (n = 35) who had been in the euthymic state for at least six months, BD-Rs (n = 30), and HCs (n = 33) completed a Stop-Signal Task (SST) and Stroop Task to assess RI and IC, respectively. Groups were compared on the stop-signal reaction time (SSRT), stop-signal delay (SSD), mean reaction time on go trials (go-RT), Stroop interference score (S-interference), and number of errors on the color-word-naming trial (S-error). Associations between the patient's clinical features and RI and IC, between the patient's treatment and RI and IC, and between RI and IC in each group were investigated.

RESULTS

BD-Ps and BD-Rs had significantly shorter go-RT and SSD, and longer SSRT compared to HCs, with these scores being similar between the BD-Ps and BD-Rs. Also, both BD-Ps and BD-Rs made significantly more S-errors than HCs, whereas, the S-interference score was not significantly different between groups. There were no significant correlations between Stroop Task and SST scores within each group, nor between clinical features or treatment variables and RI and IC in BD-Ps.

CONCLUSIONS

Overall, impairment in RI and IC (only on S-error score) was present in both patients and relatives. The persistence of these deficits in the absence of mood symptoms suggests that these features may represent candidate endophenotypes for bipolar disorder.

A meta-analysis of decision-making and attention in adults with ADHD

OBJECTIVE

Deficient reward processing has gained attention as an important aspect of ADHD, but little is known about reward-based decision-making (DM) in adults with ADHD. This article summarizes research on DM in adult ADHD and contextualizes DM deficits by comparing them to attention deficits.

METHOD

Meta-analytic methods were used to calculate average effect sizes for different DM domains and continuous performance task (CPT) measures.

RESULTS

None of the 59 included studies (DM: 12 studies; CPT: 43; both: 4) had indications of publication bias. DM and CPT measures showed robust, small to medium effects. Large effect sizes were found for a drift diffusion model analysis of the CPT.

CONCLUSION

The results support the existence of DM deficits in adults with ADHD, which are of similar magnitude as attention deficits. These findings warrant further examination of DM in adults with ADHD to improve the understanding of underlying neurocognitive mechanisms.

Applying a dual process model of self-regulation: The association between executive working memory capacity, negative urgency, and negative mood induction on pre-potent response inhibition

This study tested a dual-process model of self-control where the combination of high impulsivity (negative urgency - NU), weak reflective / control processes (low executive working memory capacity - E-WMC), and a cognitive load is associated with increased failures to inhibit pre-potent responses on a cued go/no-go task. Using a within-subjects design, a cognitive load with and without negative emotional load was implemented to consider situational factors. Results suggested that: (1) high NU was associated with low E-WMC; (2) low E-WMC significantly predicted more inhibitory control failures across tasks; and (3) there was a significant interaction of E-WMC and NU, revealing those with low E-WMC and high NU had the highest rates of inhibitory control failures on all conditions of the task. In conclusion, results suggest that while E-WMC is a strong independent predictor of inhibitory control, NU provides additional information for vulnerability to problems associated with self-regulation.

Identifying the facets of impulsivity that explain the relation between ADHD symptoms and substance use in a nonclinical sample

Adults with attention-deficit/hyperactivity disorder (ADHD) are at higher risk to use substances than their nonclinical peers. Increased levels of impulsivity are generally thought to contribute to their increased levels of risk. Impulsivity is a multifaceted construct, however, and little research to date has attempted to identify which facets of impulsivity contribute to the increased rates of substance abuse among individuals with ADHD. The current study examined the relation among ADHD symptom clusters (i.e., hyperactivity/impulsivity and inattention), substance use rates (i.e., alcohol use, nicotine use, and marijuana use), and personality processes associated with impulsive behavior in a group of young adults. Participants were 361 undergraduate students. Both symptom clusters were positively associated with rates of substance use. Specifically, hyperactive/impulsive symptoms were associated with alcohol and nicotine use, and inattentive symptoms were associated with alcohol use. Several pathways from hyperactive/impulsive symptoms to alcohol, nicotine, and marijuana use via specific facets of impulsivity were identified. These findings have implications for understanding the relation between ADHD symptoms and substance use, as well as clinical implications for preventing and treating substance use problems in individuals with symptoms of ADHD.

Fluctuating disinhibition: implications for the understanding and treatment of alcohol and other substance use disorders

Disinhibition is present in various maladaptive behaviors, including substance use disorders. Most previous research has assumed that disinhibition is a psychological construct that is relatively stable within individuals. However, recent evidence suggests that the ability to inhibit behavior fluctuates in response to environmental and psychological triggers. In this review we discuss some of the factors that cause (dis)inhibition to fluctuate, we examine whether these fluctuations contribute to subjective craving and substance consumption, and we ask if they might increase the risk of relapse in those who are attempting to abstain. The research that we discuss has furthered our understanding of the causal relationships between disinhibition and substance use disorders, and it also highlights opportunities to develop novel treatment interventions. We conclude that substance misusers and their therapists should be made aware of the triggers that can cause disinhibition to fluctuate, and we highlight the need for more research to investigate the effectiveness of inhibitory control training in clinical settings.

Reduced acute recovery from alcohol impairment in adults with ADHD

RATIONALE

Prior research has found that adults with attention-deficit/hyperactivity disorder (ADHD) show increased sensitivity to the impairing effects of alcohol (Weafer et al., Exp Clin Psychopharmacol 17: 113-121, 2009). However, these studies have focused exclusively on the ascending limb of the blood alcohol concentration (BAC) curve, and it is unclear whether these adults continue to show increased sensitivity during the later phase of the dose as BAC is declining.

OBJECTIVE

This study tested the hypothesis that those with ADHD would display increased response to alcohol during the ascending limb of the BAC curve and less recovery from the impairing effects during the descending limb.

METHODS

Adult social drinkers with ADHD and control adults completed measures of motor coordination, reaction time (RT), and subjective intoxication twice following 0.64 g/kg alcohol and placebo. The measures were administered during the ascending limb of the BAC curve and again during the descending limb.

RESULTS

During the ascending limb, alcohol reduced motor coordination, slowed RT, and increased self-reports of subjective intoxication. Those with ADHD displayed greater impairment of motor coordination compared with controls. During the descending limb, controls reported diminished subjective intoxication and showed recovery from the impairing effects of alcohol on both their motor coordination and their RT. Those with ADHD showed reduced subjective intoxication and faster RT during this time, but they did not recover motor control.

CONCLUSIONS

The protracted time course of motor impairment in adults with ADHD despite reductions in subjective intoxication may contribute to poor decision making and diminished behavioral control in this group.

Constraints on information processing capacity in adults with ADHD

OBJECTIVE

Researchers in the cognitive sciences have demonstrated the existence of processing capacity bottlenecks in the human brain. These capacity bottlenecks restrict our ability to process and act on environmental information. The purpose of the current study was to examine whether adults with attention-deficit hyperactivity disorder (ADHD) show reduced capacity of working memory and response selection mechanisms.

METHOD

Thirty-eight young adults with ADHD and 33 comparison adults were assessed using two measures of processing capacity. A dual choice-response task (psychological refractory period [PRP] task) measured response selection capacity, and an n-back task measured working memory capacity. These tasks measured capacity by assessing the degree to which increasing processing load disrupted performance.

RESULTS

Results confirmed that performance declined as cognitive load was increased, and this was true for both groups on each task. On the PRP task, the performance decline resulting from increased cognitive load was more pronounced in the ADHD group than in the control group, indicative of reduced response selection capacity in the ADHD group. On the n-back task, however, there was no group difference in the degree to which increasing processing load disrupted performance.

CONCLUSIONS

Results indicate that adults with ADHD show a specific capacity reduction of response selection. This evidence suggests a dissociation between working memory and response selection capacities, and it may have implications for understanding cognitive dysfunction in adults with ADHD.