Measuring Impulsivity in School-Aged Boys and Examining Its Relationship with ADHD and ODD Ratings

Accentuated Paralimbic and Reduced Mesolimbic D2/3-Impulsivity Associations in Parkinson's Disease

Impulsivity is a behavioral trait that is elevated in many neuropsychiatric disorders. Parkinson's disease (PD) patients can exhibit a specific pattern of reward-seeking impulsive-compulsive behaviors (ICBs), as well as more subtle changes to generalized trait impulsivity. Prior studies in healthy controls (HCs) suggest that trait impulsivity is regulated by D2/3 autoreceptors in mesocorticolimbic circuits. While altered D2/3 binding is noted in ICB+ PD patients, there is limited prior assessment of the trait impulsivity-D2/3 relationship in PD, and no prior direct comparison with patterns in HCs. We examined 54 PD (36 M; 18 F) and 31 sex- and age-matched HC (21 M; 10 F) subjects using [18F]fallypride, a high-affinity D2/3 receptor ligand, to measure striatal and extrastriatal D2/3 nondisplaceable binding potential (BPND). Subcortical and cortical assessment exclusively used ROI or exploratory-voxelwise methods, respectively. All completed the Barratt Impulsiveness Scale, a measure of trait impulsivity. Subcortical ROI analyses indicated a negative relationship between trait impulsivity and D2/3 BPND in the ventral striatum and amygdala of HCs but not in PD. By contrast, voxelwise methods demonstrated a positive trait impulsivity-D2/3 BPND correlation in ventral frontal olfactocentric-paralimbic cortex of subjects with PD but not HCs. Subscale analysis also highlighted different aspects of impulsivity, with significant interactions between group and motor impulsivity in the ventral striatum, and attentional impulsivity in the amygdala and frontal paralimbic cortex. These results suggest that dopamine functioning in distinct regions of the mesocorticolimbic circuit influence aspects of impulsivity, with the relative importance of regional dopamine functions shifting in the neuropharmacological context of PD.SIGNIFICANCE STATEMENT The biological determinants of impulsivity have broad clinical relevance, from addiction to neurodegenerative disorders. Here, we address biomolecular distinctions in Parkinson's disease. This is the first study to evaluate a large cohort of Parkinson's disease patients and age-matched healthy controls with a measure of trait impulsivity and concurrent [18F]fallypride PET, a method that allows quantification of D2/3 receptors throughout the mesocorticolimbic network. We demonstrate widespread differences in the trait impulsivity-dopamine relationship, including (1) loss of subcortical relationships present in the healthy brain and (2) emergence of a new relationship in a limbic cortical area. This illustrates the loss of mechanisms of behavioral regulation present in the healthy brain while suggesting a potential compensatory response and target for future investigation.

Inflamed but not impulsive: Acute inflammatory cytokine response does not impact prepotent response inhibition

BACKGROUND

Prior evidence has linked inflammation with impulsivity, but most of this evidence is cross-sectional. In this study, we provoked an acute inflammatory cytokine response to see whether it lowered prepotent response inhibition on three cognitive tasks.

METHOD

This study features secondary analyses from a randomized crossover trial in which 171 postmenopausal breast cancer survivors (Stage I-IIIA) each received a typhoid capsular polysaccharide vaccination and a saline placebo injection in a random sequence at two separate visits at least one month apart. Participants completed the Stroop Color-Discrepant Task, the 2-back, and the Conners Continuous Performance Test (CPT) on the computer between 5 and 7 h after the injections. They had their blood drawn once before and repeatedly after the injection to measure interleukin-1 receptor antagonist and interleukin-6 responses.

RESULTS

Women committed marginally fewer errors on the Stroop color-discrepant trials after the typhoid vaccine (M = 0.36, SE = 0.08), compared to placebo (M = 0.54, SE = 0.09, p = .076). Injection type did not predict 2-back accuracy (p = .80) or CPT commission errors (p = .47). Inflammatory cytokine responses were also unrelated to the outcomes of interest (ps>.16).

CONCLUSION

We found no evidence that an acute inflammatory cytokine response provokes response disinhibition - an important facet of impulsivity. In fact, our only marginally non-significant result suggested that women were better able to inhibit their prepotent responses on the Stroop after receiving the typhoid vaccine, compared to placebo. Further experimental tests of the acute inflammatory cytokine response's effect on other aspects of impulsivity are warranted.

LIMITATIONS

The sample was female, primarily White, highly educated cancer survivors, and recruitment was not premised on impulsive traits or diagnosis with an impulsive-related disorder. Also, there are many facets of impulsivity, and this study only measured response inhibition.

Construction of Meta-Thinking Educational Program Based on Mental-Brain Simulation (MTMBS) and Evaluating its Effectiveness on Executive Functions, Emotion Regulation, and Impulsivity in Children With ADHD: A Resting-State Functional MRI Study

OBJECTIVE

The aim of present research was to make a Meta-Thinking educational program based on mental-brain simulation and to evaluate its effectiveness on executive functions, emotion regulation and impulsivity in children with ADHD.

METHODS

The research method was Embedded Design: Embedded Experimental Model. The research sample included 32 children with ADHD who were randomly assigned to two experimental and control groups. The intervention was implemented for eight sessions of 1.5 hr for the experimental group, and fMRI images were taken from them, while the control group didn't receive any treatment. Finally, using semi-structured interviews, coherent information was collected from the parents of the experimental group about the changes made. Data were analyzed with SPSS-24, MAXQDA, fMRIprep, and FSL software.

RESULTS

The Meta-Thinking Educational Program had effect on performance of ADHD children and suppressed brain regions related to DMN.

CONCLUSION

The Implementation of this educational program plays a vital role in improving psychological problems of children with ADHD.

Interval timing relative to response inhibition in the differential reinforcement of low-rate responding in normally developing young adults

With recent proposal suggesting the multifaceted nature of impulsivity, researchers have been intrigued by the question of whether the impulsive behaviour measured in the traditionally psychological paradigms is unitary. One such paradigm, the differential reinforcement of low-rate responding (DRL), has been used to assess response inhibition, but its underlying mechanism has still been debated. In present research, we examined and differentiated the effects of both response inhibition and interval timing on a multisession DRL-10 s (DRL-10 s) in a large sample of normally developing young adults, as well as with three other measures including the stop-signal reaction task (SSRT), time production task-10 s (TPT-10 s), and the Barrett impulsivity scale-11 (BIS-11). The results showed that behavioural changes existed in DRL. As the task sessions progressed, there was an increase in both reinforcement probability and peak time, but a decrease in burst responses. Most importantly, both principal component analysis and generalized multilevel modeling yielded consistent results that as the task progressed, there was an increasing involvement of the TPT in the late sessions of DRL. However, none of the effect of SSRT was found. In sum, the differential degrees of involvement of the timing process, relative to response inhibition, were observed in DRL.

Characterizing Youth-Caregiver Concordance and Discrepancies in Psychopathology Symptoms in a US Community Sample

Evidence shows that reports of psychopathology symptoms by youth and their caregiver informants differ. To quantify youth-caregiver discrepancies in psychopathology symptoms and factors associated with such discrepancies, we investigated differences in how youth and their caregivers rated psychopathology symptoms. The sample (N = 5094) was extracted from the Philadelphia Neurodevelopmental Cohort, a community-based sample of youth and included participants ages 11-17 years old with both youth and caregiver reported symptom scores. Across psychopathology symptoms, youth-caregiver concordance was poor to fair (Cohens kappa for symptom items ranged between 0.03-0.41). Psychosis symptoms had the lowest concordance-Cohen's kappa ranged from 0.03 to 0.17 across psychosis symptoms. Discrepancies between youth and caregiver symptom reports were greater than average for Black youth and for youth of low socioeconomic status; discrepancies were also higher than average in youth with any psychiatric disorder when compared to typically developing youth. Network analysis of difference scores obtained by subtracting youth symptom scores from caregiver reported symptom scores showed that network connectivity (i.e., correlated difference scores) was sparsest for psychosis spectrum compared to other psychiatric disorders. Using a large sample, we show that youth and their caregiver informants tend to report psychopathology symptoms differently. Youth-caregiver discrepancies were the most pronounced for Black youth and youth of low socio-economic status. Race and socioeconomic status contribute to significant differences in how youth and their caregivers report such symptoms and are important factors that should be accounted for to facilitate accurate mental health symptom assessment and evaluation.

Characterizing Underlying Cognitive Components of ADHD Presentations and Co-morbid Diagnoses: A Diffusion Decision Model Analysis

OBJECTIVE

To Explore whether subtypes and comorbidities of attention-deficit hyperactivity disorder (ADHD) induce distinct biases in cognitive components involved in information processing.

METHOD

Performance on the Integrated Visual and Auditory Continuous Performance Test (IVA-CPT) was compared between 150 children (aged 7 to 10) with ADHD, grouped by DSM-5 presentation (ADHD-C, ADHD-I) or co-morbid diagnoses (anxiety, oppositional defiant disorder [ODD], both, neither), and 60 children without ADHD. Diffusion decision modeling decomposed performance into cognitive components.

RESULTS

Children with ADHD had poorer information integration than controls. Children with ADHD-C were more sensitive to changes in presentation modality (auditory/visual) than those with ADHD-I and controls. Above and beyond these results, children with ADHD+anxiety+ODD had larger increases in response biases when targets became frequent than children with ADHD-only or with ADHD and one comorbidity.

CONCLUSION

ADHD presentations and comorbidities have distinct cognitive characteristics quantifiable using DDM and IVA-CPT. We discuss implications for tailored cognitive-behavioral therapy.

The Impact of Attention Deficit-hyperactivity Disorder Symptom Severity on the Effectiveness of Transcranial Direct Current Stimulation (tDCS) on Inhibitory Control

The present study aimed to assess the impact of transcranial direct current stimulation (tDCS) on different domains of inhibitory control in children with mild or severe ADHD symptoms. Twenty-four children with ADHD, in two groups with severe and mild symptoms, received anodal or sham tDCS over the right dorsolateral prefrontal cortex (dlPFC) during performing inhibitory control tasks. A significant main effect of stimulation condition was found that was limited to the circle tracing task, and the incongruent condition of the flanker task. Moreover, the main effects of stimulation condition and group were non-significant, but their interaction was significant for No-Go accuracy. The results suggest that the right dlPFC has a crucial role in ongoing inhibition in children with ADHD, and that tDCS has a partially symptom severity-dependent effect on inhibitory control. These findings are discussed in connection with severity-dependent psychopathology.

Upregulation of Glutamatergic Receptors in Hippocampus and Locomotor Hyperactivity in Aged Spontaneous Hypertensive Rat

Epidemiologic studies have indicated that chronic hypertension may facilitate the progression of abnormal behavior, such as emotional irritability, hyperactivity, and attention impairment. However, the mechanism of how chronic hypertension affects the brain and neuronal function remains unclear. In this study, 58-week-old male spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto (WKY) control rats were used. Their locomotor activity and neuronal function were assessed by the open field test, novel object, and Y maze recognition test. Moreover brain tissues were analyzed. We found that the aged SHR exhibited significant locomotor hyperactivity when compared to the WKY rats. However, there was no significant difference in novel object and novel arm recognition between aged SHR and the WKY rats. In the analysis of synaptic membrane protein, the expression of glutamatergic receptors, such as the N-methyl-D-aspartate (NMDA) receptor receptors subunits 2B (GluN2B) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor 1 (GluA1) in the hippocampus of SHR were significantly higher than those of WKY rats. In addition, in the synaptic membrane of SHR's hippocampus and medial prefrontal cortex (mPFC), a down-regulation of astrocytes was found, though the excitatory amino acid transporter 2 (EAAT2) remained constant. Moreover, a down-regulation of microglia in the hippocampus and mPFC was seen in the SHR brain. Long-term exposure to high blood pressure causes upregulation of glutamate receptors. The upregulation of glutamatergic receptors in hippocampus may contribute to the hyper-locomotor activity of aged rodents and may as a therapeutic target in hypertension-induced irritability and hyperactivity.

Impulsivity is a heritable trait in rodents and associated with a novel quantitative trait locus on chromosome 1

Impulsivity describes the tendency to act prematurely without appropriate foresight and is symptomatic of a number of neuropsychiatric disorders. Although a number of genes for impulsivity have been identified, no study to date has carried out an unbiased, genome-wide approach to identify genetic markers associated with impulsivity in experimental animals. Herein we report a linkage study of a six-generational pedigree of adult rats phenotyped for one dimension of impulsivity, namely premature responding on the five-choice serial reaction time task, combined with genome wide sequencing and transcriptome analysis to identify candidate genes associated with the expression of the impulsivity trait. Premature responding was found to be heritable (h² = 13-16%), with significant linkage (LOD 5.2) identified on chromosome 1. Fine mapping of this locus identified a number of polymorphic candidate genes, however only one, beta haemoglobin, was differentially expressed in both the founder strain and F6 generation. These findings provide novel insights into the genetic substrates and putative neurobiological mechanisms of impulsivity with broader translational relevance for impulsivity-related disorders in humans.

Gambling, motor cautiousness, and choice impulsivity: An experimental study

BACKGROUND

Impulsivity is currently more commonly regarded as multifaceted, comprising both motor and cognitive subdomains. However, it is less clear how distinct these subdomains are, and the extent to which they interact and draw upon the same psychological resources.

METHODS

The present experiment comprised 70 regular (non-problem) gamblers, and investigated the potential to induce impulsivity transfer effects within an electronic gambling context. Original and existing harm-minimization approaches were tested for their efficacy in inducing motor cautiousness during an electronic slot machine simulation. Participants were exposed to a forced discriminatory motor choice procedure, or pop-up responsible gambling messages that either contained emotive or non-emotive responsible gambling content. The subsequent impact these interventions had on delay discounting and reflection impulsivity was also measured using the 27-item Monetary Choice Questionnaire and Information Sampling Task, respectively.

RESULTS

Findings demonstrated that only original harm-minimization approaches, which force the gambler to engage in discriminatory motor choice procedures during gambling, were successful in inducing motor cautiousness. However, both the discriminatory choice procedure and emotive message harm-minimization approaches were successful in facilitating cognitive choice, even though the emotive message intervention was unsuccessful in facilitating motor response inhibition, suggesting both an indirect motor cautiousness route, and a more direct route to improved cognitive choice during gambling.

CONCLUSION

This study demonstrated that decision-making during gambling can be improved by making simple structural changes to slot machine platforms, by encouraging active engagement in motor processes, which result in a transfer of cautiousness to wider cognitive domains.

On the Efficiency of Individualized Theta/Beta Ratio Neurofeedback Combined with Forehead EMG Training in ADHD Children

Background: Neurofeedback training (NFT) to decrease the theta/beta ratio (TBR) has been used for treating hyperactivity and impulsivity in attention deficit hyperactivity disorder (ADHD); however, often with low efficiency. Individual variance in EEG profile can confound NFT, because it may lead to influencing non-relevant activity, if ignored. More importantly, it may lead to influencing ADHD-related activities adversely, which may even result in worsening ADHD symptoms. Electromyogenic (EMG) signal resulted from forehead muscles can also explain the low efficiency of the NFT in ADHD from both practical and psychological point-of-view. The first aim of this study was to determine EEG and EMG biomarkers most related to the main ADHD characteristics, such as impulsivity and hyperactivity. The second aim was to confirm our hypothesis that the efficiency of the TBR NFT can be increased by individual adjustment of the frequency bands and simultaneous training on forehead muscle tension. Methods: We recruited 94 children diagnosed with ADHD (ADHD) and 23 healthy controls (HC). All participants were male and aged between six and nine. Impulsivity and attention were assessed with Go/no-Go task and delayed gratification task, respectively; and 19-channel EEG and forehead EMG were recorded. Then, the ADHD group was randomly subdivided into (1) standard, (2) individualized, (3) individualized+EMG, and (4) sham NFT (control) groups. The groups were compared based on TBR and EEG alpha activity, as well as hyperactivity and impulsivity three times: pre-NFT, post-NFT and 6 months after the NFT (follow-up). Results: ADHD children were characterized with decreased individual alpha peak frequency, alpha bandwidth and alpha amplitude suppression magnitude, as well as with increased alpha1/alpha2 (a1/a2) ratio and scalp muscle tension when c (η2 ≥ 0.212). All contingent TBR NFT groups exhibited significant NFT-related decrease in TBR not evident in the control group. Moreover, we detected a higher overall alpha activity in the individualized but not in the standard NFT group. Mixed MANOVA considering between-subject factor GROUP and within-subject factor TIME showed that the individualized+EMG group exhibited the highest level of clinical improvement, which was associated with increase in the individual alpha activity at the 6 months follow-up when comparing with the other approaches (post hoc t = 3.456, p = 0.011). Conclusions: This study identified various (adjusted) alpha activity metrics as biomarkers with close relationship with ADHD symptoms, and demonstrated that TBR NFT individually adjusted for variances in alpha activity is more successful and clinically more efficient than standard, non-individualized NFT. Moreover, these training effects of the individualized TBR NFT lasted longer when combined with EMG.

Neurocognitive characteristics of youth with noncomorbid and comorbid forms of conduct disorder and attention deficit hyperactivity disorder

OBJECTIVE

Studies investigating neurocognitive deficits in youth with conduct disorder (CD) and attention deficit hyperactivity disorder (ADHD) are often confounded by the high rates of comorbidity between the two.

METHOD

Neurocognitive functioning was examined in three diagnostic groups (ADHD only, CD only, comorbid ADHD and CD) matched by age, sex, IQ, and medication status (n=28-32 per group).

RESULTS

No significant differences emerged between the diagnostic groups on measures of risk-taking or response inhibition. Children with CD performed better on a measure of spatial planning than those with comorbid ADHD and CD, and dimensional analyses in the full sample (n=265) revealed a small association between ADHD symptoms and poorer spatial planning.

CONCLUSION

These results suggest that deficits in spatial planning may be more pronounced in individuals with ADHD, but that the neurocognitive functioning of youth with noncomorbid and comorbid CD and ADHD are largely similar.

The puzzling question of inhibitory control in Tourette syndrome: A meta-analysis

Tourette syndrome (TS) is a neuropsychiatric disorder involving motor and phonic tics. Inhibitory control is a key issue in TS, and many disruptive or impulsive behaviors might arise from inhibitory deficits. However, conflicting findings regarding TS patients' inhibitory performance in neuropsychological tasks have been reported throughout the literature. Therefore, this meta-analysis aimed to evaluate inhibitory control through neuropsychological tasks, and to analyze the factors modulating inhibitory deficits. To this end, a literature search was performed through MEDLINE and PsycINFO, to retrieve studies including neuropsychological tasks that assessed inhibitory control in TS patients. Of the 4020 studies identified, 61 were included in the meta-analysis, for a total of 1717 TS patients. Our analyses revealed a small to medium effect in favor of inhibitory deficits in TS patients. This effect was larger in TS+ADHD patients, but pure TS patients also showed some inhibitory deficits. Therefore, deficits in inhibitory control seem to be an inherent component of TS, and are exacerbated when ADHD is concomitant.

The Endophenotype of Impulsivity: Reaching Consilience Through Behavioral, Genetic, and Neuroimaging Approaches

Impulsivity is a multidimensional construct with implications for understanding the etiology and treatment of multiple forms of psychopathology. As a multidimensional construct, however, the processes underlying impulsivity, particularly behavioral inhibition, must be separated to allow for investigations into its neurogenetic bases. Evidence from both animal and human studies supports the role of dopamine in impulsivity, and neuroimaging research is elucidating brain regions involved in behavioral inhibition. Evidence is now emerging that suggests an interaction between dopamine system genes and frontal brain regions in underlying individual differences in behavioral inhibition. However, to reach a comprehensive understanding of the neurogenetic bases of behavioral inhibition, an appropriate framework is required. Therefore, it is proposed that by identifying intervening variables more sensitive to the effects of genetic variation, known as an endophenotype approach, we will be able to overcome many of the methodological limitations that prevent a better understanding at present.

Blunted cardiac stress reactors exhibit relatively high levels of behavioural impulsivity

Blunted physiological reactions to acute psychological stress are associated with a range of adverse health and behavioural outcomes. This study examined whether extreme stress reactors differ in their behavioural impulsivity. Individuals showing blunted (N=23) and exaggerated (N=23) cardiovascular reactions to stress were selected by screening a healthy student population (N=276). Behavioural impulsivity was measured via inhibitory control and motor impulsivity tasks. Blunted reactors exhibited greater impulsivity than exaggerated reactors on both stop-signal, F(1,41)=4.99, p=0.03, ηp(2)=0.108, and circle drawing, F(1,43)=4.00, p=0.05, η p(2)=0.085, tasks. Individuals showing blunted cardiovascular stress reactions are characterized by greater impulsivity which may contribute to their increased susceptibility to outcomes such as obesity and addiction.

Improving impulsivity assessment using movement recognition: A pilot study

The Continuous Performance Test (CPT) is a widely used computerized test to assess impulsivity. This article proposes the use of a CPT variant based on movement recognition to obtain more accurate measurements of impulsivity. In this pilot study, 22 volunteers participated in a CPT experiment responding to the stimuli by raising his or her dominant hand instead of pressing the space bar in a keyboard. Using this method, correlations of self-reported impulsivity with number of commission errors and average reaction time improved those obtained with standard CPT.

Relationships between trait impulsivity and cognitive control: the effect of attention switching on response inhibition and conflict resolution

This study examined the relationship between trait impulsivity and cognitive control, as measured by the Barratt Impulsiveness Scale (BIS) and a focused attention dichotic listening to words task, respectively. In the task, attention was manipulated in two attention conditions differing in their cognitive control demands: one in which attention was directed to one ear at a time for a whole block of trials (blocked condition) and another in which attention was switched pseudo-randomly between the two ears from trial to trial (mixed condition). Results showed that high impulsivity participants exhibited more false alarm and intrusion errors as well as a lesser ability to distinguish between stimuli in the mixed condition, as compared to low impulsivity participants. In the blocked condition, the performance levels of the two groups were comparable with respect to these measures. In addition, total BIS scores were correlated with intrusions and laterality index in the mixed but not the blocked condition. The findings suggest that high impulsivity individuals may be less prone to attentional difficulties when cognitive load is relatively low. In contrast, when attention switching is involved, high impulsivity is associated with greater difficulty in inhibiting responses and resolving cognitive conflict than is low impulsivity, as reflected in error-prone information processing. The conclusion is that trait impulsivity in a non-clinical population is manifested more strongly when attention switching is required than during maintained attention. This may have important implications for the conceptualization and treatment of impulsivity in both non-clinical and clinical populations.

Analysis of personal and family factors in the persistence of attention deficit hyperactivity disorder: results of a prospective follow-up study in childhood

OBJECTIVES

To study the course of ADHD during childhood and analyze possible personal and family predictor variables of the results.

METHOD

Sixty-one children with ADHD who were between 6 and 12 years old at the baseline assessment were evaluated 30 months later (mean age at baseline: 8.70 ± 1.97; mean age at follow-up: 10.98 ± 2.19). Status of ADHD in follow-up was identified as persistent (met DSM-IV-TR criteria according to parents' and teachers' ratings), contextually persistent (met ADHD criteria according to one informant, and there was functional impairment) and remitted ADHD (with subthreshold clinical symptomatology). Associated psychological disorders of the three groups were analyzed in the follow-up with the Conners' Rating Scales. The groups were compared on ADHD characteristics (symptoms of ADHD and impairment), child psychopathology, executive functioning (EF; inhibition, working memory) and parenting characteristics (parental stress and discipline styles) at baseline.

RESULTS

At the follow-up, 55.7% of the children continued to meet the DSM-IV-TR criteria for ADHD, 29.5% showed contextual persistence, and 14.8% presented remission of the disorder. The persistent and contextually persistent ADHD groups showed more associated psychological disorders. Inattention, oppositional problems, cognitive problems and impairment at baseline distinguished the remitted ADHD children from the persistent and contextually persistent ADHD children. Moreover, the persistent groups had significantly more emotional liability and higher parental stress than the group in remission, while no differences in EF where found among the groups.

CONCLUSIONS

ADHD children continue to present symptoms, as well as comorbid psychological problems, during adolescence and early adulthood. These findings confirm that persistence of ADHD is associated with child psychopathology, parental stress and impairment in childhood.

Convergent pharmacological mechanisms in impulsivity and addiction: insights from rodent models

Research over the last two decades has widely demonstrated that impulsivity, in its various forms, is antecedent to the development of drug addiction and an important behavioural trait underlying the inability of addicts to refrain from continued drug use. Impulsivity describes a variety of rapidly and prematurely expressed behaviours that span several domains from impaired response inhibition to an intolerance of delayed rewards, and is a core symptom of attention deficit hyperactivity disorder (ADHD) and other brain disorders. Various theories have been advanced to explain how impulsivity interacts with addiction both causally and as a consequence of chronic drug abuse; these acknowledge the strong overlaps in neural circuitry and mechanisms between impulsivity and addiction and the seemingly paradoxical treatment of ADHD with stimulant drugs with high abuse potential. Recent years have witnessed unprecedented progress in the elucidation of pharmacological mechanisms underpinning impulsivity. Collectively, this work has significantly improved the prospect for new therapies in ADHD as well as our understanding of the neural mechanisms underlying the shift from recreational drug use to addiction. In this review, we consider the extent to which pharmacological interventions that target impulsive behaviour are also effective in animal models of addiction. We highlight several promising examples of convergence based on empirical findings in rodent-based studies.

Brain functional connectivity changes in children that differ in impulsivity temperamental trait

Impulsivity is a core personality trait forming part of normal behavior and contributing to adaptive functioning. However, in typically developing children, altered patterns of impulsivity constitute a risk factor for the development of behavioral problems. Since both pathological and non-pathological states are commonly characterized by continuous transitions, we used a correlative approach to investigate the potential link between personality and brain dynamics. We related brain functional connectivity of typically developing children, measured with magnetic resonance imaging at rest, with their impulsivity scores obtained from a questionnaire completed by their parents. We first looked for areas within the default mode network (DMN) whose functional connectivity might be modulated by trait impulsivity. Then, we calculated the functional connectivity among these regions and the rest of the brain in order to assess if impulsivity trait altered their relationships. We found two DMN clusters located at the posterior cingulate cortex and the right angular gyrus which were negatively correlated with impulsivity scores. The whole-brain correlation analysis revealed the classic network of correlating and anti-correlating areas with respect to the DMN. The impulsivity trait modulated such pattern showing that the canonical anti-phasic relation between DMN and action-related network was reduced in high impulsive children. These results represent the first evidence that the impulsivity, measured as personality trait assessed through parents' report, exerts a modulatory influence over the functional connectivity of resting state brain networks in typically developing children. The present study goes further to connect developmental approaches, mainly based on data collected through the use of questionnaires, and behavioral neuroscience, interested in how differences in brain structure and functions reflect in differences in behavior.

Differential neural control in early bilinguals and monolinguals during response inhibition

We tested the hypothesis that early bilinguals and monolinguals use different brain areas when performing nonlinguistic executive control tasks. For this, we explored brain activity of early bilinguals and monolinguals during a manual stop-signal paradigm. Behaviorally, bilinguals and monolinguals did not show significant differences in the task, which led us to compare brain activation that cannot be attributed to differences in performance. Analyses demonstrated that monolinguals activated the anterior cingulate cortex more than bilinguals when performing the stop-signal task. These results offer direct support for the notion that early bilingualism exerts an effect on neural circuitry responsible for executive control. Consistent with recent reports, we found that bilinguals used the anterior cingulate more efficiently than monolinguals to monitor nonlinguistic cognitive conflicts.

Effects of Weighted Vests on Attention, Impulse Control, and On-Task Behavior in Children With Attention Deficit Hyperactivity Disorder

OBJECTIVE. In this study, we examined the effectiveness of using weighted vests for improving attention, impulse control, and on-task behavior in children with attention deficit hyperactivity disorder (ADHD).

METHOD. In a randomized, two-period crossover design, 110 children with ADHD were measured using the Conners’ Continuous Performance Test–II (CPT–II) task.

RESULTS. In the weighted vest condition, the participants did show significant improvement in all three attentional variables of the CPT–II task, including inattention; speed of processing and responding; consistency of executive management; and three of four on-task behaviors, including off task, out of seat, and fidgets. No significant improvements in impulse control and automatic vocalizations were found.

CONCLUSION. Although wearing a weighted vest is not a cure-all strategy, our findings support the use of the weighted vest to remedy attentional and on-task behavioral problems of children with ADHD.

The effects of clinically relevant doses of amphetamine and methylphenidate on signal detection and DRL in rats

Low dose amphetamine (AMPH) and methylphenidate (MPH, Ritalin(®)) are the most widely prescribed and most effective pharmacotherapy for attention-deficit/hyperactivity disorder (ADHD). Certain low, clinically relevant doses of MPH improve sustained attention and working memory in normal rats, in contrast to higher doses that impair cognitive ability and induce locomotor activity. However, the effects of AMPH of MPH on sustained attention and behavioral inhibition remain poorly characterized. The present experiments examined the actions of AMPH (0.1 and 0.25 mg/kg) and MPH (0.5 and 1.0 mg/kg) in a rat model of 1) sustained attention, where signal and blank trials were interspersed randomly and occurred at unpredictable times, and 2) behavioral inhibition, using a differential reinforcement of low rate (DRL) schedule. In a signal detection paradigm, both 0.5 mg/kg and 1.0 mg/kg MPH and 0.25 mg/kg AMPH improve sustained attention, however neither AMPH nor MPH improve behavioral inhibition on DRL. Taken together with other recent studies, it appears that clinically-relevant doses of AMPH and MPH may preferentially improve attention-related behavior while having little effect on behavioral inhibition. These observations provide additional insight into the basic behavioral actions of low-dose psychostimulants and further suggest that the use of sustained attention tasks may be important in the development of novel pharmacological treatments for ADHD.

Comorbidities and continuities as ontogenic processes: toward a developmental spectrum model of externalizing psychopathology

Research on child and adolescent mental health problems has burgeoned since the inaugural issue of Development and Psychopathology was published in 1989. In the quarter century since, static models of psychopathology have been abandoned in favor of transactional models, following the agenda set by editor Dante Cicchetti and other proponents of the discipline. The transactional approach, which has been applied to autism, depression, self-injury, and delinquency, (a) specifies vulnerabilities and risk factors across multiple levels of analysis spanning genes to cultures, (b) identifies multifinal and equifinal pathways to psychopathology, and (c) transcends traditional disciplinary boundaries. However, as noted by Rutter and Sroufe (2000), specific mechanisms of continuity, discontinuity, and comorbidity of psychopathology must be identified if we wish to understand etiology fully. In this article, we present a model of early-onset externalizing behavior in which comorbidities and continuities are viewed as ontogenic processes: products of complex longitudinal transactions between interdependent individual-level vulnerabilities (e.g., genetic, epigenetic, allostatic) and equally interdependent contextual risk factors (e.g., coercive parenting, deviant peer group affiliations, neighborhood criminality). Through interactions across levels of analysis, some individuals traverse along the externalizing spectrum, beginning with heritable trait impulsivity in preschool and ending in antisociality in adulthood. In describing our model, we note that (a) the approach outlined in the DSM to subtyping externalizing disorders continues to obscure developmental pathways to antisociality, (b) molecular genetics studies will likely not identify meaningful subtypes of externalizing disorder, and (c) ontogenic trait approaches to psychopathology are much more likely to advance the discipline in upcoming years.

Highly impulsive rats: modelling an endophenotype to determine the neurobiological, genetic and environmental mechanisms of addiction

Impulsivity describes the tendency of an individual to act prematurely without foresight and is associated with a number of neuropsychiatric co-morbidities, including drug addiction. As such, there is increasing interest in the neurobiological mechanisms of impulsivity, as well as the genetic and environmental influences that govern the expression of this behaviour. Tests used on rodent models of impulsivity share strong parallels with tasks used to assess this trait in humans, and studies in both suggest a crucial role of monoaminergic corticostriatal systems in the expression of this behavioural trait. Furthermore, rodent models have enabled investigation of the causal relationship between drug abuse and impulsivity. Here, we review the use of rodent models of impulsivity for investigating the mechanisms involved in this trait, and how these mechanisms could contribute to the pathogenesis of addiction.

Inattention, hyperactivity, and emergent literacy: different facets of inattention relate uniquely to preschoolers' reading-related skills

Although extant studies indicate that there is a strong association between attention deficit/hyperactivity disorder and reading ability in elementary school children, knowledge regarding the relation between inattentive and hyperactive/impulsive behaviors and emergent literacy in preschool children is less established. This study examined the unique and overlapping relations between measures that assess inattention and hyperactivity/impulsivity and emergent literacy skills in preschool children. Participants included 204 preschool children (M age = 56 months, 50.9% female, 79.8% European American). Behavioral rating scales were completed by teachers, and the Continuous Performance Test (CPT) and the Test of Preschool Early Literacy were completed by the preschoolers. Across measures, inattention was a unique correlate of emergent literacy skills, whereas hyperactivity/impulsivity was not. Both rating scales and the CPT indices of inattention were uniquely associated with emergent literacy skills. These results suggest that these measures are assessing different manifestations of inattention that are both unique correlates of early reading skills.

NOS1 ex1f-VNTR polymorphism affects prefrontal oxygenation during response inhibition tasks

Impulsivity is a trait shared by many psychiatric disorders and therefore a suitable intermediate phenotype for their underlying biological mechanisms. One of the molecular determinants involved is the NOS1 ex1f-VNTR, whose short variants are associated with a variety of impulsive behaviors. Fifty-six healthy controls were stratified into homozygous long (LL) (30 probands) and short (SS) (26 probands) allele groups. Subjects completed a combined stop-signal go/nogo task, while the oxygenation in the prefrontal cortex was measured with functional near-infrared spectroscopy. Electromyography was recorded to control for differences in muscle activity in the two inhibition tasks. Two questionnaires on impulsive traits were completed. Differences between the two tasks are shown by distinct activation patterns within the prefrontal cortex. The nogo task resulted mainly in the activation of the dorsolateral prefrontal cortex (dlPFC), whereas successful and unsuccessful inhibition in the stop-signal task elicited the predicted activity in the inferior frontal cortex (IFC). Although significant differences were found in neither the scores obtained on impulsivity-related questionnaires nor the behavioral data, the LL group displayed increased dlPFC activity during nogo trials and the predicted activation in the IFC during successful inhibition in the stop-signal task, while no significant activation was found in the SS group. Our data confirm an influence of NOS1 ex1f-VNTR on impulsivity, as carriers of the short risk allele exhibited diminished activity of (pre-)frontal brain regions during the inhibition in a stop-signal task. Impairment of prefrontal control with consecutive failure of inhibitory processes might underlie association findings reported previously.

Objectively-measured impulsivity and attention-deficit/hyperactivity disorder (ADHD): testing competing predictions from the working memory and behavioral inhibition models of ADHD

Impulsivity is a hallmark of two of the three DSM-IV ADHD subtypes and is associated with myriad adverse outcomes. Limited research, however, is available concerning the mechanisms and processes that contribute to impulsive responding by children with ADHD. The current study tested predictions from two competing models of ADHD-working memory (WM) and behavioral inhibition (BI)-to examine the extent to which ADHD-related impulsive responding was attributable to model-specific mechanisms and processes. Children with ADHD (n = 21) and typically developing children (n = 20) completed laboratory tasks that provided WM (domain-general central executive [CE], phonological/visuospatial storage/rehearsal) and BI indices (stop-signal reaction time [SSRT], stop-signal delay, mean reaction time). These indices were examined as potential mediators of ADHD-related impulsive responding on two objective and diverse laboratory tasks used commonly to assess impulsive responding (CPT: continuous performance test; VMTS: visual match-to-sample). Bias-corrected, bootstrapped mediation analyses revealed that CE processes significantly attenuated between-group impulsivity differences, such that the initial large-magnitude impulsivity differences were no longer significant on either task after accounting for ADHD-related CE deficits. In contrast, SSRT partially mediated ADHD-related impulsive responding on the CPT but not VMTS. This partial attenuation was no longer significant after accounting for shared variance between CE and SSRT; CE continued to attenuate the ADHD-impulsivity relationship after accounting for SSRT. These findings add to the growing literature implicating CE deficits in core ADHD behavioral and functional impairments, and suggest that cognitive interventions targeting CE rather than storage/rehearsal or BI processes may hold greater promise for alleviating ADHD-related impairments.

Instantiating the multiple levels of analysis perspective in a program of study on externalizing behavior

During the last quarter century, developmental psychopathology has become increasingly inclusive and now spans disciplines ranging from psychiatric genetics to primary prevention. As a result, developmental psychopathologists have extended traditional diathesis-stress and transactional models to include causal processes at and across all relevant levels of analysis. Such research is embodied in what is known as the multiple levels of analysis perspective. We describe how multiple levels of analysis research has informed our current thinking about antisocial and borderline personality development among trait impulsive and therefore vulnerable individuals. Our approach extends the multiple levels of analysis perspective beyond simple Biology × Environment interactions by evaluating impulsivity across physiological systems (genetic, autonomic, hormonal, neural), psychological constructs (social, affective, motivational), developmental epochs (preschool, middle childhood, adolescence, adulthood), sexes (male, female), and methods of inquiry (self-report, informant report, treatment outcome, cardiovascular, electrophysiological, neuroimaging). By conducting our research using any and all available methods across these levels of analysis, we have arrived at a developmental model of trait impulsivity that we believe confers a greater understanding of this highly heritable trait and captures at least some heterogeneity in key behavioral outcomes, including delinquency and suicide.

Multi-Method Assessment of ADHD Characteristics in Preschool Children: Relations between Measures

Several forms of assessment tools, including behavioral rating scales and objective tests such as the Continuous Performance Test (CPT), can be used to measure inattentive and hyperactive/impulsive behaviors associated with Attention-Deficit/Hyperactivity Disorder (ADHD). However, research with school-age children has shown that the correlations between parent ratings, teacher ratings, and scores on objective measures of ADHD-characteristic behaviors are modest at best. In this study, we examined the relations between parent and teacher ratings of ADHD and CPT scores in a sample of 65 preschoolers ranging from 50 to 72 months of age. No significant associations between teacher and parent ratings of ADHD were found. Parent-ratings of both inattention and hyperactivity/impulsivity accounted for variance in CPT omission errors but not CPT commission errors. Teacher ratings showed evidence of convergent and discriminant validity when entered simultaneously in a hierarchical regression. These tools may be measuring different aspects of inattention and hyperactivity/impulsivity.

Childhood Obesity and Impulsivity: An Investigation With Performance-Based Measures

The study investigated whether obese children are more impulsive than lean children, taking into account the multidimensionality of the construct. Responses of 41 overweight children were compared to those of 40 lean children. The Stop Task, Circle Drawing Task and Opposite Worlds Task were administered to measure executive inhibitory control, and the Maudsley Index of Childhood Delay Aversion and the Door Opening Task were administered to measure motivational inhibitory control. On the Stop Task, the overweight children showed less inhibitory control. On the Opposite Worlds task, we found no significant difference, whereas on the Circle Drawing Task an unexpected group difference was found. Although on the Door Opening Task the overweight children showed greater reward sensitivity, they were equally motivated to wait on the Maudsley Index of Childhood Delay. We conclude that the findings were different depending on the measure used, but that they suggest that overweight children can be characterised by a decrease in executive and motivational inhibitory control.

Combining Cognitive and Personality Measures of Impulse Control in the Assessment of Childhood ADHD

Impulse control is measured both with personality questionnaires and in cognitive laboratory tasks, yet previous results concerning the convergence of these two types of instruments are inconsistent. The current study measured impulse control of children with and without ADHD with a personality questionnaire and a go/no-go task as well as with parent ratings of ADHD symptomatology. Scores on the two measures correlate weakly with one another, yet both correlate moderately to strongly with parent ratings – and both explain unique variance of parent ratings. Accordingly, the simple sum of the standardized scores from the two measures outperforms the single measures in diagnostic accuracy and association with ADHD symptomatology. Results show that a conjoint application of personality and cognitive measures of impulse control is useful for an extended assessment of ADHD. The adequacy of personality and cognitive measures for assessing distinct facets of impulse control is discussed with regard to theoretical models of impulsivity and with regard to ADHD symptomatology.

Common structural correlates of trait impulsiveness and perceptual reasoning in adolescence

BACKGROUND

Trait impulsiveness is a potential factor that predicts both substance use and certain psychiatric disorders. This study investigates whether there are common structural cerebral correlates of trait impulsiveness and cognitive functioning in a large sample of healthy adolescents from the IMAGEN project.

METHODS

Clusters of gray matter (GM) volume associated with trait impulsiveness, Cloningers' revised temperament, and character inventory impulsiveness (TCI-R-I) were identified in a whole brain analysis using optimized voxel-based morphometry in 115 healthy 14-year-olds. The clusters were tested for correlations with performance on the nonverbal tests (Block Design, BD; Matrix Reasoning, MT) of the Wechsler Scale of Intelligence for Children IV reflecting perceptual reasoning.

RESULTS

Cloningers' impulsiveness (TCI-R-I) score was significantly inversely associated with GM volume in left orbitofrontal cortex (OFC). Frontal clusters found were positively correlated with performance in perceptual reasoning tasks (Bonferroni corrected). No significant correlations between TCI-R-I and perceptual reasoning were observed.

CONCLUSIONS

The neural correlate of trait impulsiveness in the OFC matches an area where brain function has previously been related to inhibitory control. Additionally, orbitofrontal GM volume was associated with scores for perceptual reasoning. The data show for the first time structural correlates of both cognitive functioning and impulsiveness in healthy adolescent subjects.

Genetic and environmental influences on impulsivity: a meta-analysis of twin, family and adoption studies

A meta-analysis of twin, family and adoption studies was conducted to estimate the magnitude of genetic and environmental influences on impulsivity. The best fitting model for 41 key studies (58 independent samples from 14 month old infants to adults; N=27,147) included equal proportions of variance due to genetic (0.50) and non-shared environmental (0.50) influences, with genetic effects being both additive (0.38) and non-additive (0.12). Shared environmental effects were unimportant in explaining individual differences in impulsivity. Age, sex, and study design (twin vs. adoption) were all significant moderators of the magnitude of genetic and environmental influences on impulsivity. The relative contribution of genetic effects (broad sense heritability) and unique environmental effects were also found to be important throughout development from childhood to adulthood. Total genetic effects were found to be important for all ages, but appeared to be strongest in children. Analyses also demonstrated that genetic effects appeared to be stronger in males than in females. Method of assessment (laboratory tasks vs. questionnaires), however, was not a significant moderator of the genetic and environmental influences on impulsivity. These results provide a structured synthesis of existing behavior genetic studies on impulsivity by providing a clearer understanding of the relative genetic and environmental contributions in impulsive traits through various stages of development.

Conditioned inhibition in a rodent model of attention-deficit/hyperactivity disorder

A deficit in inhibition may underlie some of the symptoms of attention-deficit/hyperactivity disorder (ADHD), particularly impulsivity. However, the data on inhibitory deficits in children with ADHD are mixed. Moreover, there has been little characterization of inhibitory processes in animal models of ADHD. Pavlov's conditioned inhibition procedure allows a direct assessment of the inhibitory status of a stimulus via summation and retardation tests. Therefore, in the current study, we examined conditioned inhibition in spontaneously hypertensive rats (SHRs), the most well-validated animal model of ADHD. SHRs and Wistar rats were trained in a simultaneous feature-negative discrimination in eyeblink conditioning. Each session consisted of a mixture of 2 trial types: a tone paired with a periocular stimulation (A+) or a tone and light presented simultaneously without a periocular stimulation (XA-). Both SHRs and Wistars were able to discriminate A+ from XA- trials. In subsequent summation (X presented simultaneously with a different conditioned excitor, B) and retardation (X paired with the periocular stimulation) tests, the presence of inhibition to X was confirmed in both SHRs and Wistars: X reduced responding to B, and X was slow to develop excitation when paired with periocular stimulation. These results are the first to demonstrate Pavlovian conditioned inhibition in SHRs and to use summation and retardation tests to confirm X as a conditioned inhibitor. The data indicate that conditioned inhibition is intact in SHRs; thus, inhibitory processes that do not require prefrontal cortex or cerebellum may be normal in this strain.

Neurocognitive development and externalizing problems: the role of inhibitory control deficits from 4 to 6 years

Executive processes have been posited as important regulators of externalizing problems (EP), but there has been little research on the relation between executive dysfunction and EP in early childhood. During the preschool period, maturation of the prefrontostriatal circuitry parallels increases in inhibitory control (IC). Poor IC development could result in elevated levels of aggressive, disruptive, and impulsive behavior. In this investigation, the development of the relation between IC and EP was examined in preschool and early elementary school children using the Day/Night and Tapping tasks. Children with more EP made more incorrect responses on both IC tasks, consistently across age and sex. The associations between EP and response latencies differed across children, however, with longer latencies on the Tapping task being most characteristic for boys with high levels of EP. This association was not apparent for girls. Two prominent aspects of early EP, aggressive and inattentive behavior, showed only weak unique associations with IC performance. These findings imply that diminished IC accompanies elevated EP as early as the preschool years, and that this decrement persists into the elementary school-age years for both girls and boys, and that accuracy and response latency may confer different information about the development of IC.

"Cool" inferior frontostriatal dysfunction in attention-deficit/hyperactivity disorder versus "hot" ventromedial orbitofrontal-limbic dysfunction in conduct disorder: a review

Attention-deficit/hyperactivity disorder (ADHD) and conduct disorder overlap behaviorally, clinically, and cognitively. An important question of potential future clinical relevance is whether these two overlapping disorders are mediated by similar or distinct underlying brain substrates. This article reviews the modern neuroimaging literature on brain structure, function, and connectivity in both disorders, shaping out commonalities and differences. Findings show that ADHD is characterized predominantly by abnormalities in inferior frontal, striatal, parietotemporal, and cerebellar regions and networks that mediate "cool"-cognitive, i.e., inhibitory, attention and timing functions associated with the disorder. Conduct disorder, by contrast, has consistently been associated with abnormalities of the "hot" paralimbic system that regulates motivation and affect, comprising lateral orbital and ventromedial prefrontal cortices, superior temporal lobes, and underlying limbic structures, most prominently the amygdala. Direct comparisons in functional imaging show that these associations of cool inferior fronto-striato-cerebellar dysfunction in ADHD and of hot orbitofrontal-paralimbic dysfunction in conduct disorder are disorder-specific. There is, hence, evidence for dissociated underlying pathophysiologies for these two disorders that may have implications for future anatomy-based differential diagnosis and prevention and intervention.

Animal models of ADHD

Studies employing animal models of attention-deficit/hyperactivity disorder (ADHD) present clear inherent advantages over human studies. Animal models are invaluable tools for the study of underlying neurochemical, neuropathological and genetic alterations that cause ADHD, because they allow relatively fast, rigorous hypothesis testing and invasive manipulations as well as selective breeding. Moreover, especially for ADHD, animal models with good predictive validity would allow the assessment of potential new therapeutics. In this chapter, we describe and comment on the most frequently used animal models of ADHD that have been created by genetic, neurochemical and physical alterations in rodents. We then discuss that an emerging and promising direction of the field is the analysis of individual behavioural differences among a normal population of animals. Subjects presenting extreme characteristics related to ADHD can be studied, thereby avoiding some of the problems that are found in other models, such as functional recovery and unnecessary assumptions about aetiology. This approach is justified by the theoretical need to consider human ADHD as the extreme part of a spectrum of characteristics that are distributed normally in the general population, as opposed to the predominant view of ADHD as a separate pathological category.

Maternal Behavior and Children's Early Emotion Regulation Skills Differentially Predict Development of Children's Reactive Control and Later Effortful Control

The role of maternal behavior and children's early emotion regulation skills in the development of children's reactive control, specifically behavioral impulsivity, and later effortful control was examined in a sample of 435 children. HLM analyses indicated significant growth in reactive control across the toddlerhood to early childhood period. Emotion regulation at age-2 positively predicted initial levels of children's reactive control abilities while maternal overcontrol/intrusiveness predicted lower levels of reactive control growth. Maternal behaviors at age-2 predicted children's effortful control abilities at age-5.5. Emotion regulation did not predict effortful control abilities. Maternal behavior and children's early emotion regulation skills may differentially facilitate the development of reactive and effortful control abilities.

Transtorno do Déficit de Atenção/Hiperatividade: o que nos informa a investigação dimensional?

Investiga-se o Transtorno do Déficit de Atenção/Hiperatividade (TDAH) em contexto escolar adotando a perspectiva dimensional. Participaram 107 crianças com idade média de 12,37 anos. Utilizou-se a Escala de TDAH - versão para professores, uma versão adaptada para pais e tarefas computadorizadas de processamento cognitivo. A prevalência de Hiperatividade pelo relato de professores e pais foi condizente com aquela apontada pela literatura (4,7%). O Déficit de Atenção, avaliado por pais e professores, correlacionou com todas as medidas de processamento de informação. Hiperatividade e Comportamento Anti-social correlacionaram com as medidas de memória de trabalho quando a primeira foi avaliada pelos professores e a segunda pelos pais, refletindo baixa concordância entre o relato de informantes a respeito das dimensões comportamentais do TDAH. Entretanto, as respostas dos professores parecem estar mais de acordo com a literatura. Conclui-se que a perspectiva dimensional de investigação pode fornecer informações relevantes sobre as características demográficas e cognitivas do TDAH.