Behavioral models of impulsivity in relation to ADHD: translation between clinical and preclinical studies

Methylphenidate and Atomoxetine-Responsive Prefrontal Cortical Genetic Overlaps in "Impulsive" SHR/NCrl and Wistar Rats

Impulsivity, the predisposition to act prematurely without foresight, is associated with a number of neuropsychiatric disorders, including attention-deficit/hyperactivity disorder (ADHD). Identifying genetic underpinnings of impulsive behavior may help decipher the complex etiology and neurobiological factors of disorders marked by impulsivity. To identify potential genetic factors of impulsivity, we examined common differentially expressed genes (DEGs) in the prefrontal cortex (PFC) of adolescent SHR/NCrl and Wistar rats, which showed marked decrease in preference for the large but delayed reward, compared with WKY/NCrl rats, in the delay discounting task. Of these DEGs, we examined drug-responsive transcripts whose mRNA levels were altered following treatment (in SHR/NCrl and Wistar rats) with drugs that alleviate impulsivity, namely, the ADHD medications methylphenidate and atomoxetine. Prefrontal cortical genetic overlaps between SHR/NCrl and Wistar rats in comparison with WKY/NCrl included genes associated with transcription (e.g., Btg2, Fos, Nr4a2), synaptic plasticity (e.g., Arc, Homer2), and neuron apoptosis (Grik2, Nmnat1). Treatment with methylphenidate and/or atomoxetine increased choice of the large, delayed reward in SHR/NCrl and Wistar rats and changed, in varying degrees, mRNA levels of Nr4a2, Btg2, and Homer2, genes with previously described roles in neuropsychiatric disorders characterized by impulsivity. While further studies are required, we dissected potential genetic factors that may influence impulsivity by identifying genetic overlaps in the PFC of "impulsive" SHR/NCrl and Wistar rats. Notably, these are also drug-responsive transcripts which may be studied further as biomarkers to predict response to ADHD drugs, and as potential targets for the development of treatments to improve impulsivity.

Morphological connectivity correlates with trait impulsivity in healthy adults

Background

Impulsivity is one crucial personality trait associated with various maladaptive behavior and many mental disorders. In the study reported here, we investigated the relationship between impulsivity and morphological connectivity (MC) between human brain regions, a newly proposed measure for brain coordination through the development and learning.

Method

Twenty-four participants’ T1-weighted magnetic resonance imaging (MRI) images and their self-reported impulsivity scores, measured by the Barratt impulsiveness scale (BIS), were retrieved from the OpenfMRI project. First, we assessed the MC by quantifying the similarity of probability density function of local morphological features between the anterior cingulate cortex (ACC), one of the most crucial hubs in the neural network modulating cognitive control, and other association cortices in each participant. Then, we correlated the MC to impulsivity scores across participants.

Results

The BIS total score was found to correlate with the MCs between the ACC and two other brain regions in the right hemisphere: the inferior frontal gyrus (IFG), a well-established structure for inhibition control; the inferior temporal gyrus (ITG), which has been previously shown to be associated with hyperactive/impulsivity symptoms. Furthermore, the ACC-IFG MC was mainly correlated with motor impulsivity, and the ACC-ITG MC was mainly correlated with attentional impulsivity.

Discussion

Together, these findings provide evidence that the ACC, IFG, and ITG in the right hemisphere are involved neural networks modulating impulsivity. Also, the current findings highlight the utility of MC analyses in facilitating our understanding of neural correlates of behavioral and personality traits.

Differential Associations of UPPS-P Impulsivity Traits With Alcohol Problems

OBJECTIVE

The UPPS-P model posits that impulsivity comprises five factors: positive urgency, negative urgency, lack of planning, lack of perseverance, and sensation seeking. Negative and positive urgency are the traits most consistently associated with alcohol problems. However, previous work has examined alcohol problems either individually or in the aggregate, rather than examining multiple problem domains simultaneously. Recent work has also questioned the utility of distinguishing between positive and negative urgency, as this distinction did not meaningfully differ in predicting domains of psychopathology. The aims of this study were to address these issues by (a) testing unique associations of UPPS-P with specific domains of alcohol problems and (b) determining the utility of distinguishing between positive and negative urgency as risk factors for specific alcohol problems.

METHOD

Associations between UPPS-P traits and alcohol problem domains were examined in two cross-sectional data sets using negative binomial regression models.

RESULTS

In both samples, negative urgency was associated with social/interpersonal, self-perception, risky behaviors, and blackout drinking problems. Positive urgency was associated with academic/occupational and physiological dependence problems. Both urgency traits were associated with impaired control and self-care problems. Associations for other UPPS-P traits did not replicate across samples.

CONCLUSIONS

Results indicate that negative and positive urgency have differential associations with alcohol problem domains. Results also suggest a distinction between the type of alcohol problems associated with these traits-negative urgency was associated with problems experienced during a drinking episode, whereas positive urgency was associated with alcohol problems that result from longer-term drinking trends.

Comparison of some behavioral effects of d- and l-methamphetamine in adult male rats

RATIONALE

Both l- and d-methamphetamine (l- and d-MA) are more potent to release norpepinephrine (NE) than dopamine, and the selectivity is greater for l-MA than d-MA. Little is known of the in vivo pharmacology of l-MA.

OBJECTIVE

This study compared the effects of l-MA and d-MA in assays of nociception, behavioral disruption, and impulsivity.

METHODS

Antinociceptive effects of d- and l-MA were examined in two pain assays: the warm water tail withdrawal test for acute nociception and the von Frey test in complete Freund's adjuvant (CFA)-treated rats for chronic inflammatory pain. Food-maintained operant responding and locomotion tests were used to assess generalized behavioral disruption. The 5-choice serial reaction time test (5-CSRTT) was used to assess drug-induced effects on impulse control. A delay discounting procedure was used to determine drug-induced changes in sensitivity to reinforcer delay (impulsive choice).

RESULTS

l-MA (3.2-10 mg/kg) produced dose-dependent antinociception in both pain assays, decreased the rate of food-maintained operant responding, and decreased locomotor activity at a higher dose (17.8 mg/kg). In contrast, d-MA (0.32-3.2 mg/kg) did not produce antinociception in either assay, produced biphasic effects on response rate, and increased locomotor activity. In the 5-CSRTT, d-MA but not l-MA produced significant increase in premature responses. In the delay discounting procedure, both drugs did not affect the delay function at doses that did not increase omissions.

CONCLUSIONS

These data suggest that d- and l-MA have different behavioral profiles. Consideration should be given to these differences in future studies when l-MA is proposed for potential therapies.

A stop-signal task for sheep: introduction and validation of a direct measure for the stop-signal reaction time

Huntington's disease (HD) patients show reduced flexibility in inhibiting an already-started response. This can be quantified by the stop-signal task. The aim of this study was to develop and validate a sheep version of the stop-signal task that would be suitable for monitoring the progression of cognitive decline in a transgenic sheep model of HD. Using a semi-automated operant system, sheep were trained to perform in a two-choice discrimination task. In 22% of the trials, a stop-signal was presented. Upon the stop-signal presentation, the sheep had to inhibit their already-started response. The stopping behaviour was captured using an accelerometer mounted on the back of the sheep. This set-up provided a direct read-out of the individual stop-signal reaction time (SSRT). We also estimated the SSRT using the conventional approach of subtracting the stop-signal delay (i.e., time after which the stop-signal is presented) from the ranked reaction time during a trial without a stop-signal. We found that all sheep could inhibit an already-started response in 91% of the stop-trials. The directly measured SSRT (0.974 ± 0.04 s) was not significantly different from the estimated SSRT (0.938 ± 0.04 s). The sheep version of the stop-signal task adds to the repertoire of tests suitable for investigating both cognitive dysfunction and efficacy of therapeutic agents in sheep models of neurodegenerative disease such as HD, as well as neurological conditions such as attention deficit hyperactivity disorder.

Prenatal nicotine exposure decreases the release of dopamine in the medial frontal cortex and induces atomoxetine-responsive neurobehavioral deficits in mice

Increased risk of attention-deficit/hyperactivity disorder (AD/HD) is partly associated with the early developmental exposure to nicotine in tobacco smoke. Emerging reports link tobacco smoke exposure or prenatal nicotine exposure (PNE) with AD/HD-like behaviors in rodent models. We have previously reported that PNE induces cognitive behavioral deficits in offspring and decreases the contents of dopamine (DA) and its turnover in the prefrontal cortex (PFC) of offspring It is well known that the dysfunction of DAergic system in the brain is one of the core factors in the pathophysiology of AD/HD. Therefore, we examined whether the effects of PNE on the DAergic system underlie the AD/HD-related behavioral changes in mouse offspring. PNE reduced the release of DA in the medial PFC (mPFC) in mouse offspring. PNE reduced the number of tyrosine hydroxylase (TH)-positive varicosities in the mPFC and in the core as well as the shell of nucleus accumbens, but not in the striatum. PNE also induced behavioral deficits in cliff avoidance, object-based attention, and sensorimotor gating in offspring. These behavioral deficits were attenuated by acute treatment with atomoxetine (3 mg/kg, s.c.) or partially attenuated by acute treatment with MPH (1 mg/kg, s.c.). Taken together, our findings support the notion that PNE induces neurobehavioral abnormalities in mouse offspring by disrupting the DAergic system and improve our understanding about the incidence of AD/HD in children whose mothers were exposed to nicotine during their pregnancy.

Frontal Traumatic Brain Injury Increases Impulsive Decision Making in Rats: A Potential Role for the Inflammatory Cytokine Interleukin-12

Traumatic brain injury (TBI) is associated with the development of numerous psychiatric diseases. Of particular concern for TBI patients is the impact of chronic impulsivity on daily functioning. Despite the scope of the human problem, little has been done to address impulsivity in animal models of brain injury. In the current study, we examined the effects of either a severe or a milder bilateral frontal controlled cortical impact injury on impulsivity using the Delay Discounting Task (DDT), in which preference for smaller-sooner over larger-later rewards is indicative of greater impulsive choice. Both milder and severe TBI caused a significant, chronic increase in impulsive decision making. Despite these pronounced changes in performance of the DDT, memory function, as assessed by the Morris Water Maze, was not impaired in more mildly injured rats and only transiently impacted in the severe TBI group. Whereas a significant lesion was only evident in severely injured rats, analysis of cytokine levels within the frontal cortex revealed a selective increase in interleukin (IL)-12 that was associated with the magnitude of the change in impulsive choice caused by both milder and severe TBI. These findings suggest that tissue loss alone cannot explain the increased impulsivity observed, and that inflammatory pathways mediated by IL-12 may be a contributing factor. The findings from this study highlight the sensitivity of sophisticated behavioral measures designed to assess neuropsychiatric dysfunction in the detection of TBI-induced cognitive impairments and their utility in identifying potential mechanistic pathways and therapeutic targets.

Selective and interactive effects of D2 receptor antagonism and positive allosteric mGluR4 modulation on waiting impulsivity

Background

Metabotropic glutamate receptor 4 (mGluR4) and dopamine D₂ receptors are specifically expressed within the indirect pathway neurons of the striato-pallidal-subthalamic pathway. This unique expression profile suggests that mGluR4 and D₂ receptors may play a cooperative role in the regulation and inhibitory control of behaviour. We investigated this possibility by testing the effects of a functionally-characterised positive allosteric mGluR4 modulator, 4-((E)-styryl)-pyrimidin-2-ylamine (Cpd11), both alone and in combination with the D₂ receptor antagonist eticlopride, on two distinct forms of impulsivity.

Methods

Rats were trained on the five-choice serial reaction time task (5-CSRTT) of sustained visual attention and segregated according to low, mid, and high levels of motor impulsivity (LI, MI and HI, respectively), with unscreened rats used as an additional control group. A separate group of rats was trained on a delay discounting task (DDT) to assess choice impulsivity.

Results

Systemic administration of Cpd11 dose-dependently increased motor impulsivity and impaired attentional accuracy on the 5-CSRTT in all groups tested. Eticlopride selectively attenuated the increase in impulsivity induced by Cpd11, but not the accompanying attentional impairment, at doses that had no significant effect on behavioural performance when administered alone. Cpd11 also decreased choice impulsivity on the DDT (i.e. increased preference for the large, delayed reward) and decreased locomotor activity.

Conclusions

These findings demonstrate that mGluR4s, in conjunction with D₂ receptors, affect motor- and choice-based measures of impulsivity, and therefore may be novel targets to modulate impulsive behaviour associated with a number of neuropsychiatric syndromes.

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Positive allosteric mGluR4 modulation increases motor impulsivity and impairs aspects of visual attention.

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Positive allosteric mGluR4 modulation decreases choice impulsivity as well as indices of motor function.

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Blocking D2 receptors selectively attenuates the effect of positive allosteric mGluR4 modulation on motor impulsivity.

Methylphenidate alleviates manganese-induced impulsivity but not distractibility

Recent studies from our lab have demonstrated that postnatal manganese (Mn) exposure in a rodent model can cause lasting impairments in fine motor control and attention, and that oral methylphenidate (MPH) treatment can effectively treat the dysfunction in fine motor control. However, it is unknown whether MPH treatment can alleviate the impairments in attention produced by Mn exposure. Here we used a rodent model of postnatal Mn exposure to determine whether (1) oral MPH alleviates attention and impulse control deficits caused by postnatal Mn exposure, using attention tasks that are variants of the 5-choice serial reaction time task, and (2) whether these treatments affected neuronal dendritic spine density in the medial prefrontal cortex (mPFC) and dorsal striatum. Male Long-Evans rats were exposed orally to 0 or 50Mn/kg/d throughout life starting on PND 1, and tested as young adults (PND 107-115) on an attention task that specifically tapped selective attention and impulse control. Animals were treated with oral MPH (2.5mg/kg/d) throughout testing on the attention task. Our findings show that lifelong postnatal Mn exposure impaired impulse control and selective attention in young adulthood, and that a therapeutically relevant oral MPH regimen alleviated the Mn-induced dysfunction in impulse control, but not selective attention, and actually impaired focused attention in the Mn group. In addition, the effect of MPH was qualitatively different for the Mn-exposed versus control animals across a range of behavioral measures of inhibitory control and attention, as well as dendritic spine density in the mPFC, suggesting that postnatal Mn exposure alters catecholaminergic systems modulating these behaviors. Collectively these findings suggest that MPH may hold promise for treating the behavioral dysfunction caused by developmental Mn exposure, although further research is needed with multiple MPH doses to determine whether a dose can be identified that ameliorates the dysfunction in both impulse control and selective attention, without impairing focused attention.

Animal models to improve our understanding and treatment of suicidal behavior

Worldwide, suicide is a leading cause of death. Although a sizable proportion of deaths by suicide may be preventable, it is well documented that despite major governmental and international investments in research, education and clinical practice suicide rates have not diminished and are even increasing among several at-risk populations. Although nonhuman animals do not engage in suicidal behavior amenable to translational studies, we argue that animal model systems are necessary to investigate candidate endophenotypes of suicidal behavior and the neurobiology underlying these endophenotypes. Animal models are similarly a critical resource to help delineate treatment targets and pharmacological means to improve our ability to manage the risk of suicide. In particular, certain pathophysiological pathways to suicidal behavior, including stress and hypothalamic-pituitary-adrenal axis dysfunction, neurotransmitter system abnormalities, endocrine and neuroimmune changes, aggression, impulsivity and decision-making deficits, as well as the role of critical interactions between genetic and epigenetic factors, development and environmental risk factors can be modeled in laboratory animals. We broadly describe human biological findings, as well as protective effects of medications such as lithium, clozapine, and ketamine associated with modifying risk of engaging in suicidal behavior that are readily translatable to animal models. Endophenotypes of suicidal behavior, studied in animal models, are further useful for moving observed associations with harmful environmental factors (for example, childhood adversity, mechanical trauma aeroallergens, pathogens, inflammation triggers) from association to causation, and developing preventative strategies. Further study in animals will contribute to a more informed, comprehensive, accelerated and ultimately impactful suicide research portfolio.

Dissociable effects of systemic and orbitofrontal administration of adrenoceptor antagonists on yohimbine-induced motor impulsivity

The α₂-adrenoceptor antagonist, yohimbine, is commonly used as a pharmacological stressor. Its behavioural effects are typically attributed to elevated noradrenaline release via blockade of central, inhibitory autoreceptors. We have previously reported that yohimbine increases motor impulsivity in rats on the five-choice serial reaction time task (5CSRTT), a cognitive behavioural assessment which measures motor impulsivity and visuospatial attention. Furthermore, this effect depended on cyclic adenomonophosphate (cAMP) signalling via cAMP response element binding (CREB) protein in the orbitofrontal cortex (OFC). However, the role of specific adrenoceptors in this effect is not well-characterised. We therefore investigated whether the pro-impulsive effects of systemic yohimbine could be reproduced by direct administration into the OFC, or attenuated by intra-OFC or systemic administration of prazosin and propranolol-antagonists at the α₁- and β-adrenoceptor, respectively. Male Long-Evans rats were trained on the 5CSRTT and implanted with guide cannulae aimed at the OFC. Systemically administered α₁- or β-adrenoceptor antagonists attenuated yohimbine-induced increases in premature responding. In contrast, local infusion of yohimbine into the OFC reduced such impulsive responding, while blockade of α₁- or β-adrenoceptors within the OFC had no effect on either basal or yohimbine-stimulated motor impulsivity. Direct administration of selective antagonists at the α₁-, α₂- or β-adrenoceptor into the OFC therefore produce clearly dissociable effects from systemic administration. Collectively, these data suggest that the pro-impulsivity effect of yohimbine can be modulated by adrenergic signalling in brain areas outside of the OFC, in addition to non-adrenergic signalling pathways within the OFC.

Understanding Within-Session Loss-Chasing: An Experimental Investigation of the Impact of Stake Size on Cognitive Control

Loss-chasing is a central feature of problematic gambling, yet it remains a poorly conceived and understood concept. Loss-chasing is believed to stem from an erosion of cognitive control when gambling. The opportunity to gamble at significantly disparate stake sizes on a gambling activity is considered to be a risk factor for loss-chasing. This study investigated the impact of gambling at disparate stake sizes on executive processes integral to maintaining cognitive control when gambling, namely response inhibition and reflection impulsivity. Frequent adult non-problem gamblers (n = 32) participated in a repeated measures experiment; and gambled at three disparate stake sizes (£20, £2 and no stake per bet) on a simulated gambling task. Participants' response inhibition performance and reflection impulsivity levels after gambling at various stake sizes were compared via a go/no-go task and information sampling task, respectively. Quality of decision-making i.e. the evaluation of available information to make probability judgements was impaired after gambling at higher stakes in comparison to lower stakes, indicating an increase in reflection impulsivity. No effect on response inhibition was observed. Although exploratory, this suggests that the opportunity for participants to substantially increase stake size on a gambling activity may be a risk factor for impaired cognitive performance when gambling, and perhaps create vulnerability for within-session loss-chasing in some players.

A one-week 5-choice serial reaction time task to measure impulsivity and attention in adult and adolescent mice

Many psychiatric disorders emerge during adolescence. The study of executive functions in animal models of these disorders critically requires short-duration tasks measuring these functions before the animal ages. Here, a novel 5-choice serial reaction time task (5-CSRTT) protocol is presented, to measure attention and impulsivity within one week, without scheduled food deprivation and with little animal handling. Mice were allowed 24-h/day task access from their home-cage, during which they could self-pace task progression and earn unlimited food rewards depending on task performance. Manipulation of task parameters in this self-paced 5-CSRTT protocol (SP-5C) affected attentional performance and impulsivity to a similar extent as previously observed in the 5-CSRTT. Task activity followed intrinsic circadian rhythm, distinctive for the SP-5C protocol, with task performance stable over the day. The sensitivity of the SP-5C protocol to detect strain differences between C57BL/6J, DBA/2 J, BXD16 and BXD62 mice was demonstrated as well as its suitability for testing adolescent mice. Acute administration of the muscarinic acetylcholine receptor antagonist scopolamine impaired attentional performance, providing initial pharmacological validation of the task. The SP-5C substantially shortens the assessment of impulsivity and attention, increases test efficiency and enables the assessment of adolescent mouse models of psychiatric disorders.

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

OBJECTIVE

Attention-deficit hyperactivity disorder (ADHD) has been associated with various manifestations of impulsivity in adults, including elevated rates of other impulsive disorders, substance use, questionnaire-based impulsivity scores, and inhibitory dysregulation on neurocognitive tests. The relationship between ADHD and all these other forms of impulsivity has yet to be explored within the context of a single comprehensive study.

METHODS

A total of 423 young adults, who gambled ≥5 times in the preceding year, were recruited using media advertisements and undertook detailed assessment including structured psychiatric interview, questionnaires, and neurocognitive tests. Participants with ADHD symptoms were identified using the Adult ADHD Self-Report Scale Screener (ASRS-V1.1) and were compared to controls using multivariate analysis of variance (MANOVA).

RESULTS

ADHD symptoms were found in 20.3% of the sample, but only 7.3% of these subjects had ever received a formal diagnosis. ADHD symptoms were associated with significantly lower quality of life, lower self-esteem, higher emotional dysregulation, higher impulsivity questionnaire scores, more problematic Internet use, greater occurrence of psychiatric disorders, and impaired stop-signal reaction times. Of these variables, stop-signal reaction times and Barratt attentional impulsiveness were the strongest predictors of group classification.

CONCLUSIONS

ADHD symptoms are common and under-diagnosed in young adults who gamble, and are most strongly linked with certain other types of impulsivity (questionnaire- and cognitive-based measures) and with emotional dysregulation, suggesting that these are each important considerations in understanding the pathophysiology of the disorder, but also potential treatment targets. It is necessary to question whether treatment for adult ADHD could be enhanced by considering self-esteem, emotional reactivity, and impaired inhibitory control as specific treatment targets, in addition to the core diagnostic symptoms of the disorder.

Time-on-task effects in children with and without ADHD: depletion of executive resources or depletion of motivation?

Children with attention-deficit/hyperactivity disorder (ADHD) are characterized by deficits in their executive functioning and motivation. In addition, these children are characterized by a decline in performance as time-on-task increases (i.e., time-on-task effects). However, it is unknown whether these time-on-task effects should be attributed to deficits in executive functioning or to deficits in motivation. Some studies in typically developing (TD) adults indicated that time-on-task effects should be interpreted as depletion of executive resources, but other studies suggested that they represent depletion of motivation. We, therefore, investigated, in children with and without ADHD, whether there were time-on-task effects on executive functions, such as inhibition and (in)attention, and whether these were best explained by depletion of executive resources or depletion of motivation. The stop-signal task (SST), which generates both indices of inhibition (stop-signal reaction time) and attention (reaction time variability and errors), was administered in 96 children (42 ADHD, 54 TD controls; aged 9-13). To differentiate between depletion of resources and depletion of motivation, the SST was administered twice. Half of the participants was reinforced during second task performance, potentially counteracting depletion of motivation. Multilevel analyses indicated that children with ADHD were more affected by time-on-task than controls on two measures of inattention, but not on inhibition. In the ADHD group, reinforcement only improved performance on one index of attention (i.e., reaction time variability). The current findings suggest that time-on-task effects in children with ADHD occur specifically in the attentional domain, and seem to originate in both depletion of executive resources and depletion of motivation. Clinical implications for diagnostics, psycho-education, and intervention are discussed.

Association between Internet gaming disorder and adult attention deficit and hyperactivity disorder and their correlates: Impulsivity and hostility

Internet gaming disorder (IGD) and attention deficit and hyperactivity disorder (ADHD) are associated with impulsivity and hostility. This study evaluated the associations among ADHD, impulsivity, hostility, and IGD. We recruited 87 individuals with IGD and 87 controls without a history of IGD. All participants underwent a diagnostic interview based on the DSM-5 IGD criteria and DSM-IV-TR ADHD criteria and completed a questionnaire regarding impulsivity and hostility. The information from the diagnostic interviews was assessed using the clinical global impression scale. The results suggested that IGD is associated with ADHD among young adults and that young adults with both IGD and ADHD have higher impulsivity and hostility. Furthermore, impulsivity and hostility mediate the association between ADHD and IGD. Thus, ADHD is a common comorbidity of IGD among young adults, and impulsivity and hostility are major factors involved in comorbid ADHD and IGD. Young adults with ADHD should be thoroughly assessed, particularly for their impulsivity and hostility, and interventions for IGD should be developed.

Comparison of impulsivity in non-problem, at-risk and problem gamblers

As a non-substance addiction, gambling disorder represents the model for studying the neurobiology of addiction without toxic consequences of chronic drug use. From a neuropsychological perspective, impulsivity is deemed as a potential construct responsible in the onset and development of drug addiction. The objective of this study was to investigate the associations between impulsivity and gambling status in young adults with varying severity of gambling. A sample of 1120 college students, equally divided into non-problem, at-risk and problem gamblers, were administered multiple measures of impulsivity including the UPPSP Impulsive Behaviors Scale (UPPSP), the Barratt Impulsiveness Scale-11 (BIS-11), and the Delay-discounting Test (DDT). Compared with non-problem gamblers, both at-risk gamblers and problem gamblers displayed elevated scores on Negative Urgency, Positive Urgency, Motor Impulsiveness, and Attentional Impulsiveness. Problem gamblers showed higher scores than at-risk gamblers on Positive Urgency. Logistic regression models revealed that only Negative Urgency positively predicted both at-risk gambling and problem gambling compared to non-problem gambling. These results suggest that dimensions of impulsivity may be differentially linked to gambling behavior in young adults, with Negative Urgency putatively identified as an important impulsivity-related marker for the development of gambling disorder, which may provide a better understanding of the pathogenesis.

Post-Error Slowing in Patients With ADHD: A Meta-Analysis

OBJECTIVE

Post-error slowing (PES) is a cognitive mechanism for adaptive responses to reduce the probability of error in subsequent trials after error. To date, no meta-analytic summary of individual studies has been conducted to assess whether ADHD patients differ from controls in PES.

METHOD

We identified 15 relevant publications, reporting 26 pairs of comparisons (ADHD, n = 1,053; healthy control, n = 614). Random-effect meta-analysis was used to determine the statistical effect size (ES) for PES.

RESULTS

PES was diminished in the ADHD group as compared with controls, with an ES in the medium range (Cohen's d = 0.42). Significant group difference was observed in relation to the inter-stimulus interval (ISI): While healthy participants slowed down after an error during long (3,500 ms) compared with short ISIs (1,500 ms), ADHD participants sustained or even increased their speed.

CONCLUSION

The pronounced group difference suggests that PES may be considered as a behavioral indicator for differentiating ADHD patients from healthy participants.

Acute effects of methylphenidate on impulsivity and attentional behavior among adolescents comorbid for ADHD and conduct disorder

Adolescents with Attention Deficit Hyperactivity Disorder (ADHD) and Conduct Disorder (CD) experience deficits in neuropsychological measures of attention, inhibition, and reward processes. Methylphenidate treatment for ADHD and CD has acute effects on these processes. Some of these same aspects of performance are separately described in the Behavioral Model of Impulsivity, which uses a modified approach to measurement. This study characterized the acute effects of methylphenidate attention, initiation, inhibition, and reward processes described in this model of impulsivity. Thirty-one adolescents from the United States of America with comorbid ADHD and CD completed measures of impulsivity (response initiation, response inhibition, and consequence) and attention following placebo, 20 mg, and 40 mg of a long-acting dose of methylphenidate. Methylphenidate effects on attentional performance was more robust than on any of the measures of impulsivity. Adolescent performance from this behavioral perspective is interpreted in the context of divergence from previous neuropsychological tests of acute methylphenidate effects.

Gambling, Delay, and Probability Discounting in Adults With and Without ADHD

OBJECTIVE

We investigated the relationship between impulsivity, as measured by delay and probability discounting, and gambling-related cognitions and behavior in adults with and without ADHD.

METHOD

Adults who met Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV) diagnostic criteria for ADHD (n = 31) and controls (n = 29) were recruited from the community. All completed an interview that included an assessment of psychiatric disorders, gambling questionnaires, and simulated gambling, delay, and probability discounting tasks.

RESULTS

The ADHD group was more likely to meet the criteria for problem gambling and was more impulsive than controls based on a composite discounting measure. ADHD symptoms were correlated with gambling-related cognitions and behavior. Probability, but not delay discounting, explained significant variance in gambling-related measures after controlling for ADHD symptoms.

DISCUSSION

Results confirm an association between adult ADHD and gambling, and suggest that the facets of impulsivity related to risk proneness may be an independent risk factor for problem gambling in this population.

Comparison between the efficacies of Risperidone with Haloperidol in the treatment of attention-deficit hyperactivity disorder (ADHD) among preschoolers: a randomized double-blind clinical trial

BACKGROUND

Attention-deficit hyperactivity disorder (ADHD) is a common psychiatric disease with a worldwide pooled prevalence of 5.29%.

OBJECTIVE

To compare the efficacy of Risperidone with Haloperidol in the treatment of attention-deficit hyperactivity disorder (ADHD) among 3- to 6-year-old children.

METHODS

In a 6-week double-blind clinical trial, the efficacy of Risperidone 0.5-2 mg with a dose of maximum Haloperidol 0.075 mg/kg was assessed in 39 children aged 3-6 years. This study was conducted at the Golestan Psychiatric Clinic (Ahvaz, Iran). Measurement tools included the Conners' Parent Rating Scale (CPRS-48), Children's Global Assessment Scale (CGAS), and the Attention Deficit Hyperactivity Disorder Rating Scale (ADHD-RS). Data were analyzed using the Wilcoxon, Mann-Whitney, and Fisher's exact tests in the SPSS 19.

RESULTS

During the 6 weeks, the decline in points was seen in Conner's rating scale and in ADHD-RS score in Risperidone and Haloperidol groups (p<0.001). On the CGAS scale, an increase of performance in both groups for six weeks was statistically significant (p<0.001). In the scales of ADHD-RS and CPRS-48, no statistically significant difference was observed between the two treatment groups; i.e., in terms of reducing the rate during weeks of two, four, and six (p>0.05).

CONCLUSIONS

Haloperidol and Risperidone possibly can be an acceptable treatment choice in the ADHD treatment of 3- to 6-year-old children.

TRIAL REGISTRATION

The trial was registered at the Iranian Registry of Clinical Trials (http://www.irct.ir) with the Irct ID: IRCT2015082623766N1.

FUNDING

This work was financially supported by grant (ref. no.: U-93130) from the vice chancellor for Research Affairs of Ahvaz Jundishapur University of Medical Sciences.

In need of constraint: Understanding the role of the cingulate cortex in the impulsive mind

Impulsive behavior often occurs without forethought and can be driven by strong emotions or sudden impulses, leading to problems in cognition and behavior across a wide range of situations. Although neuroimaging studies have explored the neurocognitive indicators of impulsivity, the large-scale functional networks that contribute to different aspects of impulsive cognition remain unclear. In particular, we lack a coherent account of why impulsivity is associated with such a broad range of different psychological features. Here, we use resting state functional connectivity, acquired in two independent samples, to investigate the neural substrates underlying different aspects of self-reported impulsivity. Based on the involvement of the anterior cingulate cortex (ACC) in cognitive but also affective processes, five seed regions were placed along the caudal to rostral gradient of the ACC. We found that positive urgency was related to functional connectivity between subgenual ACC and bilateral parietal regions such as retrosplenial cortex potentially highlighting this connection as being important in the modulation of the non-prospective, hastiness - related aspects of impulsivity. Further, two impulsivity dimensions were associated with significant alterations in functional connectivity of the supragenual ACC: (i) lack of perseverance was positively correlated to connectivity with the bilateral dorsolateral prefrontal cortex and right inferior frontal gyrus and (ii) lack of premeditation was inversely associated with functional connectivity with clusters within bilateral occipital cortex. Further analysis revealed that these connectivity patterns overlapped with bilateral dorsolateral prefrontal and bilateral occipital regions of the multiple demand network, a large-scale neural system implicated in the general control of thought and action. Together these results demonstrate that different forms of impulsivity have different neural correlates, which are linked to the functional connectivity of a region of anterior cingulate cortex. This suggests that poor perseveration and premeditation might be linked to dysfunctions in how the rostral zone of the ACC interacts with the multiple demand network that allows cognition to proceed in a controlled way.

VNTR-DAT1 and COMTVal158Met Genotypes Modulate Mental Flexibility and Adaptive Behavior Skills in Down Syndrome

Down syndrome (DS) is an aneuploidy syndrome that is caused by trisomy for human chromosome 21 resulting in a characteristic cognitive and behavioral phenotype, which includes executive functioning and adaptive behavior difficulties possibly due to prefrontal cortex (PFC) deficits. DS also present a high risk for early onset of Alzheimer Disease-like dementia. The dopamine (DA) system plays a neuromodulatory role in the activity of the PFC. Several studies have implicated trait differences in DA signaling on executive functioning based on genetic polymorphisms in the genes encoding for the catechol-O-methyltransferase (COMTVal158Met) and the dopamine transporter (VNTR-DAT1). Since it is known that the phenotypic consequences of genetic variants are modulated by the genetic background in which they occur, we here explore whether these polymorphisms variants interact with the trisomic genetic background to influence gene expression, and how this in turn mediates DS phenotype variability regarding PFC cognition. We genotyped 69 young adults of both genders with DS, and found that VNTR-DAT1 was in Hardy-Weinberg equilibrium but COMTVal158Met had a reduced frequency of Met allele homozygotes. In our population, genotypes conferring higher DA availability, such as Met allele carriers and VNTR-DAT1 10-repeat allele homozygotes, resulted in improved performance in executive function tasks that require mental flexibility. Met allele carriers showed worse adaptive social skills and self-direction, and increased scores in the social subscale of the Dementia Questionnaire for People with Intellectual Disabilities than Val allele homozygotes. The VNTR-DAT1 was not involved in adaptive behavior or early dementia symptoms. Our results suggest that genetic variants of COMTVal158Met and VNTR-DAT1 may contribute to PFC-dependent cognition, while only COMTVal158Met is involved in behavioral phenotypes of DS, similar to euploid population.

Classification and treatment of antisocial individuals: From behavior to biocognition

Antisocial behavior is a heterogeneous construct that can be divided into subtypes, such as antisocial personality and psychopathy. The adverse consequences of antisocial behavior produce great burden for the perpetrators, victims, family members, and for society at-large. The pervasiveness of antisocial behavior highlights the importance of precisely characterizing subtypes of antisocial individuals and identifying specific factors that are etiologically related to such behaviors to inform the development of targeted treatments. The goals of the current review are (1) to briefly summarize research on the operationalization and assessment of antisocial personality and psychopathy; (2) to provide an overview of several existing treatments with the potential to influence antisocial personality and psychopathy; and (3) to present an approach that integrates and uses biological and cognitive measures as starting points to more precisely characterize and treat these individuals. A focus on integrating factors at multiple levels of analysis can uncover person-specific characteristics and highlight potential targets for treatment to alleviate the burden caused by antisocial behavior.

Risk-taking behavior and impulsivity among HCV-infected patients

The association between risk behaviors and hepatitis C virus (HCV) has been extensively studied. It is also proved that impulsivity is associated with risk behaviors. However, there is a lack of studies investigating the association between HCV and impulsivity, a characteristic that can contribute directly to these risk behaviors. This study aimed to investigate HCV-infected individuals' impulsivity and whether this feature mediates risk behavior. Adult patients with liver diseases (n=269) were divided into two groups: viral group (n=157) - patients with HCV and nonviral group (n=112). Risk behaviors were evaluated by a sociodemographic questionnaire. Impulsivity was assessed through Barratt Impulsiveness Scale - BIS-11. Psychiatric comorbidities were investigated by the Mini International Neuropsychiatric Interview 5.0.0. The viral group patients had higher impulsivity than the nonviral group in all domains: attentional impulsivity, motor impulsivity, and nonplanning. Risk behaviors were also shown to be associated with impulsivity levels. Our results suggest that HCV-infected patients are more impulsive than individuals with other liver diseases, even when analyses are controlled for the presence of comorbid mental disorders. In addition, at-risk behavior was significantly mediated by impulsivity.

Variation in serotonin neurotransmission genes affects neural activation during response inhibition in adolescents and young adults with ADHD and healthy controls

OBJECTIVES

Deficits in response inhibition have been associated with attention-deficit/hyperactivity disorder (ADHD). Given the role of serotonin in ADHD and impulsivity, we postulated that genetic variants within the serotonin pathway might influence response inhibition.

METHODS

We measured neural activation during stop-signal task performance in adolescents with ADHD (N = 185), their unaffected siblings (N = 111), and healthy controls (N = 124), and investigated the relationship of two serotonin gene polymorphisms (the rs6296 SNP of the HTR1B gene and HTTLPR variants of the 5-HTT gene) with the neural correlates of response inhibition.

RESULTS

The whole-brain analyses demonstrated large scale neural activation differences in the inferior and medial frontal and temporal/parietal regions of the response inhibition network between the different variants of both the HTR1B and 5HTT genes. Activation in these regions was significantly associated with stop-task performance, but not with ADHD diagnosis or severity. No associations were found between HTR1B and 5HTT variants and ADHD or ADHD-related neural activation.

CONCLUSIONS

These results provide novel evidence that serotonin may play an important role in the neurobiology of response inhibition. Although response inhibition is strongly linked to ADHD, serotonin linked genetic variants associated with response inhibition and its neural correlates do not explain variance of the ADHD phenotype.

Preventative treatment in an animal model of ADHD: Behavioral and biochemical effects of methylphenidate and its interactions with ovarian hormones in female rats

Clinical and preclinical studies on attention deficit hyperactivity disorder (ADHD) show that juvenile males that are exposed to methylphenidate (MPH) show reduced risk for substance use later in life. In contrast, little is known about whether females have the same enduring treatment response to stimulants and how gonadal hormones influence their behavior later in life. Females received either a sham or 6-hydroxydopamine (6-OHDA) microinjection in the prefrontal cortex (PFC) at postnatal day (P)10. Subjects were then treated with Vehicle or MPH (2mg/kg, p.o.) between P20-35 and tested during late adolescence/young adulthood (P60); half of these subjects underwent ovariectomy at P55 to determine hormonal influences. Females with 6-OHDA were depleted of PFC dopamine by 61% and demonstrated increased impulsive choice (delayed discounting) and preferences for cocaine-associated environments relative to control females. Both MPH and ovariectomy reduced impulsive choice and cocaine preferences in 6-OHDA females, but had no enduring effect in Sham females. Ovariectomy itself did not significantly affect impulsivity. Juvenile MPH interacted strongly with 6-OHDA to increase D4, D5, Alpha-1A, Alpha-2A, and 5-HT-1A mRNA receptor expression in the PFC. MPH alone effected D1 mRNA, while 6-OHDA increased BDNF; all markers were decreased by ovariectomy. Together, these data suggest that 6-OHDA changes in dopamine are not only relevant for ADHD-like behaviors, but their long-term modulation by treatment and the influence of cyclical differences in menstrual cycle.

The indirect effects of childhood attention deficit hyperactivity disorder on alcohol problems in adulthood through unique facets of impulsivity

BACKGROUND AND AIMS

Research has not studied unique impulsivity dimensions as prospective links between childhood attention deficit hyperactivity disorder (ADHD) and alcohol problems. We examined the association between childhood ADHD, five facets of impulsivity and alcohol problems in adulthood and the indirect effects of childhood ADHD-to-impulsivity-to-alcohol problems.

DESIGN, SETTING AND PARTICIPANTS

Participants were from a longitudinal study (n = 289, meanage  = 28.67) of individuals with (n = 170) and without (n = 119) childhood ADHD. The ADHD sample, as part of an ADHD summer treatment program, was diagnosed initially in childhood (1987-96, Pittsburgh, PA, USA) via structured parent interview and standardized parent/teacher ratings. The ADHD sample and demographically similar individuals without ADHD (living in the greater Pittsburgh area) were recruited to participate in the Pittsburgh ADHD Longitudinal Study (PALS) between 1999 and 2003.

MEASUREMENTS

Self-reported impulsivity (UPPS-P) and alcohol-related problems were assessed in adulthood (2011-14).

FINDINGS

Adults with, compared with those without, childhood ADHD had more alcohol problems (β = 0.34, P < 0.05) and higher levels of negative urgency, positive urgency, lack of perseverance and lack of planning (βs = 0.24-0.31, Ps < 0.001). Impulsivity facets (except sensation-seeking) were related to number of alcohol problems (βs = 0.34-0.61, Ps < 0.05). Negative (β = 0.26, P < 0.01) and positive (β = 0.27, P < 0.01) urgency mediated the association between childhood ADHD and number of adult alcohol problems.

CONCLUSIONS

Elevated levels of emotional impulsivity (negative/positive urgency) may place children with attention deficit hyperactivity disorder at increased risk for alcohol problems in adulthood.

Blocking serotonin but not dopamine reuptake alters neural processing during perceptual decision making

Dopamine and serotonin have opponent interactions on aspects of impulsivity. Therefore we wanted to test the hypothesis that dopamine and serotonin would have opposing effects on speed-accuracy trade offs in a perceptual decision making task. Unlike other behavioral measures of impulsivity, perceptual decision making allows us to determine whether decreasing premature responses, often interpreted as decreased impulsivity, corresponds to increased behavioral performance. We administered GBR-12909 (a dopamine transporter blocker), escitalopram (a serotonin transporter blocker), or saline in separate sessions to 3 rhesus macaques. We found that animals had slower reaction times (RTs) on escitalopram than on GBR-12909 or saline. However, they were also least accurate on escitalopram. Animals were faster, although nonsignificantly, on GBR than saline and had equivalent accuracy. Administration of GBR-12909 did cause animals to be faster in error trials than correct trials. Therefore, from the point of view of RTs the animals were less impulsive on escitalopram. However, the decreased accuracy of the monkeys shows that they were not able to make use of their slower response times to make more accurate decisions. Therefore, impulsivity was reduced on escitalopram, but at the expense of a slower information-processing rate in the perceptual inference task. (PsycINFO Database Record

Childhood inhibitory control and adolescent impulsivity and novelty seeking as differential predictors of relational and overt aggression

Impulsivity is commonly conflated with novelty seeking, but these traits are conceptually independent and hold different predictive implications. Using a multi-informant, longitudinal design, we examined childhood inhibitory control, as well as adolescent impulsivity and novelty seeking, as predictors of aggression in a sample of 976 twins. Lower childhood inhibitory control and higher adolescent impulsivity predicted both overt and relational aggression in regression analyses that accounted for sex, puberty status, age, and socioeconomic status. As predicted, novelty seeking did not predict aggression, a finding that supports its independence from impulsivity.

Cigarette smoking and ADHD: An examination of prognostically relevant smoking behaviors among adolescents and young adults

Attention-deficit/hyperactivity disorder (ADHD) is associated with health risks in adolescence which includes the potential for smoking cigarettes, early smoking initiation, and rapid progression to daily smoking. Much less is known, however, about prognostically relevant smoking behaviors among individuals with childhood ADHD. Further research in this area is important for identifying individuals at pronounced risk for nicotine addiction, and for developing effective interventions for this population. This study examined initiation of cigarette smoking, progression to regular smoking, quantity of use, indicators of tobacco dependence, and quit rates among adolescents and young adults with (n = 364) and without (n = 240) childhood ADHD. Individuals with, versus without, ADHD histories were significantly more likely to become daily smokers independent of conduct disorder (CD). They were also more likely to initiate smoking at younger ages and to progress to regular smoking more quickly. There were no significant group differences in cigarettes smoked per day, Fagerström Test of Nicotine Dependence (FTND), or Nicotine Dependence Syndrome Scale (NDSS) scores or in smoking within 30 min of waking. However, smokers with ADHD reported more intense withdrawal and craving during periods of abstinence than non-ADHD smokers. There were no significant group differences in number of quit attempts. Lastly, there were no significant differences among symptom persisters and desisters in daily smoking and amount. Individuals with ADHD histories are at high risk for persistent smoking given their early onset, rapid course, and abstinence characteristics. Smoking cessation programs may need to be adapted or otherwise intensified for those with ADHD. (PsycINFO Database Record

Psychological and Neurobiological Correlates of Food Addiction

Food addiction (FA) is loosely defined as hedonic eating behavior involving the consumption of highly palatable foods (ie, foods high in salt, fat, and sugar) in quantities beyond homeostatic energy requirements. FA shares some common symptomology with other pathological eating disorders, such as binge eating. Current theories suggest that FA shares both behavioral similarities and overlapping neural correlates to other substance addictions. Although preliminary, neuroimaging studies in response to food cues and the consumption of highly palatable food in individuals with FA compared to healthy controls have shown differing activation patterns and connectivity in brain reward circuits including regions such as the striatum, amygdala, orbitofrontal cortex, insula, and nucleus accumbens. Additional effects have been noted in the hypothalamus, a brain area responsible for regulating eating behaviors and peripheral satiety networks. FA is highly impacted by impulsivity and mood. Chronic stress can negatively affect hypothalamic-pituitary-adrenal axis functioning, thus influencing eating behavior and increasing desirability of highly palatable foods. Future work will require clearly defining FA as a distinct diagnosis from other eating disorders.

Partial sleep deprivation impacts impulsive action but not impulsive decision-making

Sleep deprivation may lead to increased impulsivity, however, previous literature has focused on examining effects of total sleep deprivation (TSD) rather than the more common condition, partial sleep deprivation (PSD) or 'short sleep'. Moreover, it has been unclear whether PSD impacts impulse-related cognitive processes, and specifically if it differentially affects impulsive action versus impulsive decision-making. We sought to determine if short compared to long sleep (6 vs. 9h/night) impacts impulsive action via behavioral inhibition (Go/No-Go), and/or impulsive decision-making processes of risk taking (Balloon Analogue Risk Task [BART]) and preferences for immediate over delayed rewards (Delay Discounting). In a within-subject design, 34 participants (71% female, mean age=37.0years, SD=10.54) were assigned to four consecutive nights of 6h/night (short sleep) and 9h/night (long sleep) in their own home in random counterbalanced order. Sleep was measured via wrist-worn actigraphs to confirm adherence to the sleep schedules (mean short sleep=5.9h, SD=0.3; mean long sleep=8.6h, SD=0.3, p<0.001). The Go/No-Go, BART, and Delay Discounting tasks were completed following both sleep conditions. Participants had more inhibition errors on the Go/No-Go task after short (mean false alarms=19.79%, SD=14.51) versus long sleep (mean=15.97%, SD=9.51, p=0.039). This effect was strongest in participants reporting longer habitual time in bed (p=0.04). There were no differences in performance following long- versus short-sleep for either delay discounting or the BART (p's>0.4). Overall, these results indicate that four days of PSD diminishes behavioral inhibition abilities, but may not alter impulsive decision-making. These findings contribute to the emerging understanding of how partial sleep deprivation, currently an epidemic, impacts cognitive ability. Future research should continue to explore the connection between PSD and cognitive functions, and ways to minimize the occurrence and negative consequences of short sleep.

Pubertal Maturation Compression and Behavioral Impulsivity among Boys at Increased Risk for Substance Use

OBJECTIVES

While early onset of puberty among girls has been related to substance use involvement and other adverse outcomes, less research has examined pubertal development and outcomes in boys. Further, research on puberty has not been conducted in the context of other risk factors for substance use involvement such as impulsivity. To address these gaps, this study characterized boys' pubertal development from preadolescence to mid-adolescence and related it to substance use risk and behavioral impulsivity.

METHODS

A sample of 153 boys completed the Pubertal Development Scale to assess perception of their pubertal development relative to same age peers from ages 10 to 16 years, at 6-month intervals. Group-based trajectory modeling identified three distinct patterns of pubertal development: boys with more slowly developing boys with either earlier (n = 54) or later (n = 43) pubertal timing, and boys with faster tempo of pubertal development (n = 56). The groups were compared on demographic and substance use risk characteristics, as well as behavioral measures of impulsivity.

RESULTS

Boys who had the accelerated progression through puberty had the highest proportion of family histories of substance use disorder and perform more impulsively on reward choice measures.

CONCLUSIONS

Outcomes are consistent within the Maturation Compression Hypothesis and social neuroscience models of adolescent developmental risk.

The two-faceted nature of impulsivity in patients with borderline personality disorder and substance use disorder

BACKGROUND

Impulsivity, which has been the subject of extensive debate in psychiatric research, is a clinically important concept, especially with respect to Borderline Personality Disorder (BPD) and Substance Use Disorders (SUD). The current study aims to examine the presence of two aspects of impulsivity (self-reported impulsivity and delay discounting) in patients with BPD, SUD (alcohol use=AUD or drug use=DUD) and the combination of both disorders (BPD+SUD).

METHODS

Patients were recruited from eight different mental health treatment service facilities. A total of 345 participants were assessed and divided into six groups: (1) healthy controls (non-BPD, non-SUD), (2) patients with BPD (non-SUD), (3) DUD (non-BPD), (4) AUD (non-BPD), (5) BPD+AUD and (6) BPD+DUD.

RESULTS

The behavioural measure of impulsivity is more conservative than the results of self-reported impulsivity. Furthermore, ANOVA indicated that BPD and SUD have significant effects on self-reported impulsivity, even when demographic variables, income, other psychiatric symptoms or depression are considered as covariates. On the other hand, the main effects of BPD and SUD are mediated by psychiatric symptoms and depression when delay discounting is considered as a dependent variable.

CONCLUSIONS

When self-reported, impulsivity is over-estimated as compared to reports based on behavioural measures. These results provide support for the notion that impulsivity is not a unitary construct, and that it instead has different manifestations in BPD and SUD patients.

Attentional processes in posttraumatic stress disorder and the associated changes in neural functioning

Posttraumatic Stress Disorder (PTSD) is associated with alterations in attention at the behavioral and neural levels. However, there are conflicting findings regarding the specific type of attention impairments present in PTSD, as the commonly used tests of attention do not isolate the mechanisms behind attention abnormalities, and the constructs measured do not map onto the neurocircuits governing attention. Here, we review the literature on attention processing in PTSD and offer directions for future research to clarify these unanswered questions. First, using instruments that allow assessment of behavioral and neurophysiological attention components will be necessary to understand attention deficits in PTSD. Second, focus on intra-individual variability in addition to assessment of central tendency may help clarify some of the mixed findings. Third, longitudinal studies on attentional processes are warranted to determine how attention contributes to the development and maintenance of PTSD. Integration of behavioral and neural measures of attention will be useful in understanding the pathophysiology of PTSD.

Social Networking Site Use While Driving: ADHD and the Mediating Roles of Stress, Self-Esteem and Craving

BACKGROUND

Adults who present ADHD symptoms have an increased risk for vehicle accidents. One conceivable overlooked account for this association is the possibility that people with ADHD symptoms use rewarding technologies such as social networking sites (SNS) while driving, more than others. The objective of this study was to understand if and how ADHD symptoms can promote SNS use while driving and specifically to conceptualize and examine mechanisms which may underlie this association. To do so, ADHD is viewed in this study as an underlying syndrome that promotes SNS use while driving in a manner similar to how addictive syndromes promote compulsive seeking of drug rewards.

METHODS

Time-lagged survey data regarding ADHD, stress, self-esteem, SNS craving experience, SNS use while driving, and control variables were collected from a sample of 457 participants who use a popular SNS (Facebook) and drive, after face-validity examination with a panel of five users and pretest with a sample of 47. These data were subjected to structural equation modeling (SEM) analyses using the frequency of ADHD symptoms measured with ASRS v1.1 Part A as a continuous variable, as well as multivariate analysis of variance using ADHD classification based on ASRS v1.1 scoring guidelines.

RESULTS

ADHD symptoms promoted increased stress and reduced self-esteem, which in turn, together with ADHD symptoms, increased one's cravings to use the SNS. These cravings ultimately translated into increased SNS use while driving. Using the ASRS v1.1 classification, people having symptoms highly consistent with ADHD presented elevated levels of stress, cravings to use the SNS, and SNS use while driving, as well as decreased levels of self-esteem. Cravings to use the SNS among men were more potent than among women.

CONCLUSION

SNS use while driving may be more prevalent than previously assumed and may be indirectly associated with ADHD symptoms. It is a new form of impulsive and risky behavior which is more common among people with symptoms compatible with ADHD than among others. Consistent with addiction and decision making models, SNS use while driving can be viewed as a form of a compensatory reward seeking behavior. As such, prevention and reduction interventions that target the mediating perceptions and states should be devised.

Risky decision making in Attention-Deficit/Hyperactivity Disorder: A meta-regression analysis

ADHD has been associated with various forms of risky real life decision making, for example risky driving, unsafe sex and substance abuse. However, results from laboratory studies on decision making deficits in ADHD have been inconsistent, probably because of between study differences. We therefore performed a meta-regression analysis in which 37 studies (n ADHD=1175; n Control=1222) were included, containing 52 effect sizes. The overall analysis yielded a small to medium effect size (standardized mean difference=.36, p<.001, 95% CI [.22, .51]), indicating that groups with ADHD showed more risky decision making than control groups. There was a trend for a moderating influence of co-morbid Disruptive Behavior Disorders (DBD): studies including more participants with co-morbid DBD had larger effect sizes. No moderating influence of co-morbid internalizing disorders, age or task explicitness was found. These results indicate that ADHD is related to increased risky decision making in laboratory settings, which tended to be more pronounced if ADHD is accompanied by DBD. We therefore argue that risky decision making should have a more prominent role in research on the neuropsychological and -biological mechanisms of ADHD, which can be useful in ADHD assessment and intervention.

Methamphetamine-, d-Amphetamine-, and p-Chloroamphetamine-Induced Neurotoxicity Differentially Effect Impulsive Responding on the Stop-Signal Task in Rats

Abused amphetamines, such as d-amphetamine (AMPH) and methamphetamine (METH), are highly addictive and destructive to health and productive lifestyles. The abuse of these drugs is associated with impulsive behavior, which is likely to contribute to addiction. The amphetamines also differentially damage dopamine (DA) and serotonin (5-HT) systems, which regulate impulsive behavior; therefore, exposure to these drugs may differentially alter impulsive behavior to effect the progression of addiction. We examined the impact of neurotoxicity induced by three amphetamines on impulsive action using a stop-signal task in rats. Animals were rewarded with a food pellet after lever pressing (i.e., a go trial), unless an auditory cue was presented and withholding lever press gained reward (i.e., a stop trial). Animals were trained on the task and then exposed to a neurotoxic regimen of either AMPH, p-chloroamphetamine (PCA), or METH. These regimens preferentially reduced DA transporter levels in striatum, 5-HT transporter levels in prefrontal cortex, or both, respectively. Assessment of performance on the stop-signal task beginning 1 week after the treatment revealed that AMPH produced a deficit in go-trial performance, whereas PCA did not alter performance on either trial type. In contrast, METH produced a deficit in stop-trial performance (i.e., impulsive action) but not go-trial performance. These findings suggest that the different neurotoxic consequences of substituted amphetamines are associated with different effects on inhibitory control over behavior. Thus, the course of addiction and maladaptive behavior resulting from exposure to these substances is likely to differ.

Increased Delay Discounting on a Novel Real-Time Task among Girls, but not Boys, with ADHD

The aim of this study was to examine delay discounting in girls and boys with ADHD-Combined type (ADHD-C) relative to typically developing (TD) children on two tasks that differ in the extent to which the rewards and delays were experienced by participants. Children ages 8-12 years with ADHD-C (n=65; 19 girls) and TD controls (n=55; 15 girls) completed two delay discounting tasks involving a series of choices between smaller, immediate and larger, delayed rewards. The classic delay discounting task involved choices about money at delays of 1-90 days and only some of the outcomes were actually experienced by the participants. The novel real-time discounting task involved choices about an immediately consumable reward (playing a preferred game) at delays of 25-100 s, all of which were actually experienced by participants. Participants also provided subjective ratings of how much they liked playing the game and waiting to play. Girls with ADHD-C displayed greater delay discounting compared to boys with ADHD-C and TD girls and boys on the real-time discounting task. Diagnostic group differences were not evident on the classic discounting task. In addition, children with ADHD-C reported wanting to play the game more and liking waiting to play the game less than TD children. This novel demonstration of greater delay discounting among girls with ADHD-C on a discounting task in which the rewards are immediately consumable and the delays are experienced in real-time informs our understanding of sex differences and motivational processes in children with ADHD. (JINS, 2016, 22, 12-23).

Complex Living Conditions Impair Behavioral Inhibition but Improve Attention in Rats

Rapid adaptation to changes, while maintaining a certain level of behavioral inhibition is an important feature in every day functioning. How environmental context and challenges in life can impact on the development of this quality is still unknown. In the present study, we examined the effect of a complex rearing environment during adolescence on attention and behavioral inhibition in adult male rats. We also tested whether these effects were affected by an adverse early life challenge, maternal deprivation (MD). We found that animals that were raised in large, two floor Marlau^TM cages, together with 10 conspecifics, showed improved attention, but impaired behavioral inhibition in the 5-choice serial reaction time task. The early life challenge of 24 h MD on postnatal day 3 led to a decline in bodyweight during adolescence, but did not by itself influence responses in the 5-choice task in adulthood, nor did it moderate the effects of complex housing. Our data suggest that a complex rearing environment leads to a faster adaptation to changes in the environment, but at the cost of lower behavioral inhibition.

Rearing in an enriched environment attenuated hyperactivity and inattention in the Spontaneously Hypertensive Rats, an animal model of Attention-Deficit Hyperactivity Disorder

Attention-deficit hyperactivity disorder (ADHD) is a prevalent neurodevelopmental disorder, characterized by symptoms of hyperactivity, inattention, and impulsivity. It is commonly treated with psychostimulants that typically begins during childhood and lasts for an extended period of time. However, there are concerns regarding the consequences of chronic psychostimulant treatment; thus, there is a growing search for an alternative management for ADHD. One non-pharmacological management that is gaining much interest is environmental enrichment. Here, we investigated the effects of rearing in an enriched environment (EE) on the expression of ADHD-like symptoms in the Spontaneously Hypertensive Rats (SHRs), an animal model of ADHD. SHRs were reared in EE or standard environment (SE) from post-natal day (PND) 21 until PND 49. Thereafter, behavioral tests that measure hyperactivity (open field test [OFT]), inattention (Y-maze task), and impulsivity (delay discounting task) were conducted. Additionally, electroencephalography (EEG) was employed to assess the effects of EE on rat's brain activity. Wistar-Kyoto (WKY) rats, the normotensive counterpart of the SHRs, were used to determine whether the effects of EE were specific to a particular genetic background. EE improved the performance of the SHRs and WKY rats in the OFT and Y-maze task, but not the delay discounting task. Interestingly, EE induced significant EEG changes in WKY rats, but not in the SHRs. These findings show that rearing environment may play a role in the expression of ADHD-like symptoms in the SHRs and that EE may be considered as a putative complementary approach in managing ADHD symptoms.