Walter Roberts

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

Separate cognitive processes govern the inhibitory control of manual and oculomotor movements. Despite this fundamental distinction, little is known about how these inhibitory control processes relate to more complex domains of behavioral functioning. This study sought to determine how these inhibitory control mechanisms relate to broadly defined domains of impulsive behavior. Thirty adults with attention-deficit/hyperactivity disorder (ADHD) and 28 comparison adults performed behavioral measures of inhibitory control and completed impulsivity inventories. Results suggest that oculomotor inhibitory control, but not manual inhibitory control, is related to specific domains of self-reported impulsivity. This finding was limited to the ADHD group; no significant relations between inhibitory control and impulsivity were found in comparison adults. These results highlight the heterogeneity of inhibitory control processes and their differential relations to different facets of impulsivity.

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

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

Fixation time is a sensitive measure of cocaine cue attentional bias

BACKGROUND AND AIMS Attentional bias has been demonstrated to a variety of substances. Evidence suggests that fixation time is a more direct measure of attentional bias than response time. The aims of this experiment were to demonstrate that fixation time during the visual probe task is a sensitive and stable measure of cocaine cue attentional bias in cocaine-using adults compared to controls. DESIGN A between-subject, repeated-measures experiment. SETTING An out-patient research unit. PARTICIPANTS Fifteen cocaine using and 15 non-cocaine-using adults recruited from the community. MEASUREMENTS Participants completed a visual probe task with eye tracking and a modified Stroop during two experimental sessions. FINDINGS A significant interaction between cue type and group (F = 13.5; P < 0.05) indicated that cocaine users, but not controls, displayed an attentional bias to cocaine-related images as measured by fixation time. There were no changes in the magnitude of attentional bias across sessions (F = 3.4; P > 0.05) and attentional bias correlated with self-reported life-time cocaine use (r = 0.64, P < 0.05). Response time on the visual probe (F = 1.1; P > 0.05) as well as on the modified Stroop (F = 0.1; P > 0.05) failed to detect an attentional bias. CONCLUSIONS Fixation time on cocaine-related stimuli (propensity to remain focused on the stimulus) is a sensitive and stable measure of cocaine cue attentional bias in cocaine-using adults.

Separating Automatic and Intentional Inhibitory Mechanisms of Attention in Adults With Attention-Deficit/Hyperactivity Disorder

Researchers in the cognitive sciences recognize a fundamental distinction between automatic and intentional mechanisms of inhibitory control. The use of eye-tracking tasks to assess selective attention has led to a better understanding of this distinction in specific populations, such as children with attention-deficit/hyperactivity disorder (ADHD). This study examined automatic and intentional inhibitory control mechanisms in adults with ADHD using a saccadic interference task and a delayed ocular response task. Thirty adults with ADHD were evaluated against 27 comparison adults on measures of inhibitory control. The delayed ocular response task showed that adults with ADHD were less able than comparison adults to inhibit a reflexive saccade toward the sudden appearance of a stimulus in the periphery. However, saccadic interference task performance showed that the ADHD group did not differ significantly from the comparison group on a measure of automatic inhibitory control. These findings suggest a dissociation between automatic and intentional inhibitory deficits in adults with ADHD.

Constraints on Information Processing Capacity in Adults With ADHD

OBJECTIVE Researchers in the cognitive sciences have demonstrated the existence of processing capacity bottlenecks in the human brain. These capacity bottlenecks restrict our ability to process and act on environmental information. The purpose of the current study was to examine whether adults with attention-deficit hyperactivity disorder (ADHD) show reduced capacity of working memory and response selection mechanisms. METHOD Thirty-eight young adults with ADHD and 33 comparison adults were assessed using two measures of processing capacity. A dual choice-response task (psychological refractory period [PRP] task) measured response selection capacity, and an n-back task measured working memory capacity. These tasks measured capacity by assessing the degree to which increasing processing load disrupted performance. RESULTS Results confirmed that performance declined as cognitive load was increased, and this was true for both groups on each task. On the PRP task, the performance decline resulting from increased cognitive load was more pronounced in the ADHD group than in the control group, indicative of reduced response selection capacity in the ADHD group. On the n-back task, however, there was no group difference in the degree to which increasing processing load disrupted performance. CONCLUSIONS Results indicate that adults with ADHD show a specific capacity reduction of response selection. This evidence suggests a dissociation between working memory and response selection capacities, and it may have implications for understanding cognitive dysfunction in adults with ADHD.

Drinking to Distraction: Does Alcohol Increase Attentional Bias in Adults With ADHD?

Previous research has shown that social drinkers continue to show attentional bias toward alcohol-related stimuli even after consuming a moderate dose of alcohol. In contrast, little is known about how alcohol acutely affects attentional bias in groups at risk to develop alcohol-related problems, such as adults with attention-deficit/hyperactivity disorder (ADHD). Such individuals may show increased attentional bias following alcohol relative to nonclinical controls. The present study tested this hypothesis by examining acute alcohol effects on attentional bias in 20 social drinkers with ADHD and 20 social drinkers with no history of ADHD. Participants performed a visual-probe task after receiving the following doses of alcohol: 0.64 g/kg, 0.32 g/kg, and 0.0 g/kg (placebo). Those in the ADHD group showed increased attentional bias under active alcohol doses, whereas attentional bias was similar across doses in the control group. Attentional bias predicted ad libitum alcohol consumption during a taste-rating session. This relation was observed only in the ADHD group. These findings indicate that an acute alcohol dose increases attentional bias in adults with ADHD. Further, attentional bias appears to be a predictor of ad libitum consumption in this group.

Heavy drinking and the role of inhibitory control of attention.

Alcohol can disrupt goal-directed behavior by impairing the ability to inhibit attentional shifts toward salient but goal-irrelevant stimuli. Individuals who are highly sensitive to this effect of the drug may be at increased risk for problematic drinking, especially among those whose attention is drawn to alcohol-related cues in the environment (i.e., attentional bias). The current study examined the acute impairing effect of alcohol on inhibitory mechanisms of attentional control in a group of healthy social drinkers. We then examined whether increased sensitivity to this disinhibiting effect of alcohol was associated with heavy drinking, especially among those who have an attentional bias toward alcohol-related stimuli. Eighty nondependent social drinkers performed a delayed ocular response task that measured their inhibitory control of attention by their ability to suppress attentional shifts to irrelevant stimuli. Attentional bias was measured using a visual probe task. Inhibitory control was assessed following a moderate dose of alcohol (0.64 g/kg) and a placebo. Participants made more inhibitory failures (i.e., premature saccades) following 0.64 g/kg alcohol compared with placebo and the relation of this effect to their drinking habits did depend on the level of the drinkers attentional bias to alcohol-related stimuli. Among drinkers with higher attentional bias, greater impairment of inhibitory control was associated with heavier drinking. In contrast, drinkers with little or no attentional bias showed no relation between their sensitivity to the disinhibiting effects of alcohol and drinking habits. These findings have implications for understanding how heightened incentive-salience of alcohol cues and impaired attentional control can interactively contribute to excessive alcohol use.

Attentional bias to alcohol-related stimuli as an indicator of changes in motivation to drink.

Heavy drinkers show an attentional bias toward alcohol-related visual cues. A recent study in our laboratory (Weafer & Fillmore, 2013) showed that alcohol decreases attentional bias among heavy drinkers, suggesting that alcohol satiates motivation to drink in heavy drinkers. Little is known, however, about how this satiety effect might change across the time course of the blood alcohol concentration (BAC) curve. It is possible that attentional bias may return later in the time course if the satiety effect begins to diminish. The current study tested this hypothesis in a group of high-risk binge drinkers (n = 20). Participants completed a visual-probe task to measure their attentional bias and a self-report measure of their desire for alcohol after receiving 0.64 g/kg and 0.0 g/kg alcohol (placebo) during separate dose challenge sessions. The measures were obtained during the ascending limb of the BAC curve under alcohol (Test 1) and again during the descending limb (Test 2) at a comparable BAC. The measures also were obtained at the same times following placebo. Under alcohol, no attentional bias was observed during Test 1, but drinkers reported increased desire to drink. During Test 2, attentional bias was evident, but participants reported less desire to drink. Attentional bias was not correlated with desire to drink at any time point. Following placebo, attentional bias was evident during both tests. These findings show that alcohol causes a temporary reduction of attentional bias among heavy drinkers. These changes do not correspond with their self-reported motivation to drink.

Effects of varenicline on alcohol self-administration and craving in drinkers with depressive symptoms:

Varenicline (VAR) is approved to aid in smoking cessation and has been shown to be effective for reducing alcohol consumption in heavy drinkers. Little is known, however, about treatment moderators that may influence efficacy. The current study reanalyzed data from a human laboratory study (Verplaetse et al., 2016) to determine whether VAR was more effective at reducing alcohol use among drinkers reporting symptoms of depression. Participants were 60 adults meeting DSM-IV criteria for alcohol use disorders (n = 60) who were randomly assigned to receive VAR (1 mg/day, 2 mg/day) or placebo. Following 7 days of medication pretreatment, participants attended a laboratory testing session. They provided self-reported ratings of alcohol craving and performed an ad libitum alcohol consumption task after receiving a priming dose of alcohol (target blood alcohol concentration = 0.030 g/dL). Higher blood VAR plasma levels were associated with less alcohol craving and less drinking among participants with more depressive symptoms. Among participants with fewer depressive symptoms, VAR was associated with more drinking during the ad libitum drinking task. These findings show that depression symptoms may be a moderator of VAR efficacy in alcohol users and provides evidence for the role of nAChRs in depression and alcohol use.

Intersection of Stress and Gender in Association With Transitions in Past Year DSM-5 Substance Use Disorder Diagnoses in the United States

Background Stress contributes to the development and maintenance of substance use disorders, with some research suggesting that the impact of stress on substance use disorders is greater in women. However, this has yet to be evaluated in a national dataset, across major substances of abuse. Methods Using data from the newly available U.S. National Epidemiologic Survey on Alcohol and Related Conditions (NESARC; Wave 3; n = 36,309), we evaluated relationships among past year stressful life events (0 or 1 vs. 2+ events, range 0–16) and gender, and their association with transitions (new vs. absent cases; ongoing vs. remitted cases) in Diagnostic and Statistical Manual of Mental Disorders Fifth Edition alcohol use disorder, tobacco use disorder, cannabis use disorder, and nonmedical prescription opioid use disorder diagnoses. Results Having two or more stressful life events in the past year increased the odds of having a new alcohol use disorder, tobacco use disorder, cannabis use disorder, and opioid use disorder (OR = 3.14, 2.15, 5.52, and 3.06, respectively) or ongoing alcohol use disorder, tobacco use disorder, and cannabis use disorder (OR = 2.39, 2.62, and 2.95, respectively) compared to zero or one stressful life event. A stress by gender interaction for new vs. absent alcohol use disorder demonstrated that having two or more stressful life events was associated with increased odds of new alcohol use disorder in men (OR = 2.51) and even greater odds of new alcohol use disorder in women (OR = 3.94). Conclusions Results highlight that stress is a robust factor in both men and women with new or ongoing substance use disorders, and that effective treatments for substance use should consider the role of stress in addiction etiology and maintenance. There was little evidence for gender differences in the role of stress on transitions in substance use disorders, except for the onset of alcohol use disorders. Given that rates of alcohol use disorders are increasing in women, the impact of stress needs to be considered.