Behavioral Measures Of Impulsivity Research Articles

Global and local morphometric differences in recently abstinent methamphetamine-dependent individuals

Methamphetamine (MA) is associated with behavioral and cognitive deficits that may be related to macrostructural abnormalities. Quantitative anatomical comparisons between controls and methamphetamine-dependent individuals have produced conflicting results. We examined local and global differences in brain structure in 61 abstinent methamphetamine-dependent individuals and 44 controls with voxel-based morphometry and tissue segmentation. We related regional differences in gray matter density and whole brain segmentation volumes to performance on a behavioral measure of impulsivity and group membership using multiple linear regression. Within the MA group, we related cortical and subcortical gray matter density to length of abstinence. Controls had greater density relative to MA in bilateral insula and left middle frontal gyrus. Impulsivity was higher in the MA group and, within all subjects, impulsivity was positively correlated with gray matter density in posterior cingulate cortex and ventral striatum and negatively correlated in left superior frontal gyrus. Length of abstinence from MA was associated with greater amygdalar density. Earlier age of first use of MA (in subjects who initiated use before age 21) was associated with smaller intracranial volume. The findings are consistent with multiple possible mechanisms including neuroadaptations due to addictive behavior, neuroinflammation as well as dopaminergic and serotonergic neurotoxicity.

Dysfunctional reward processing in male alcoholics: An ERP study during a gambling task

Objective A dysfunctional neural reward system has been shown to be associated with alcoholism. The current study aims to examine reward processing in male alcoholics by using event-related potentials (ERPs) as well as behavioral measures of impulsivity and risk-taking. Methods Outcome-related negativity (ORN/N2) and positivity (ORP/P3) derived from a single outcome gambling task were analyzed using a mixed model procedure. Current density was compared across groups and outcomes using standardized low resolution electromagnetic tomography (sLORETA). Behavioral scores were also compared across groups. Correlations of ERP factors with behavioral and impulsivity factors were also analyzed. Results Alcoholics showed significantly lower amplitude than controls during all outcome conditions for the ORP component and decreased amplitude during the loss conditions for the ORN component. Within conditions, gain produced higher amplitudes than loss conditions. Topographically, both groups had an anterior focus during loss conditions and posterior maxima during gain conditions, especially for the ORN component. Decreased ORP current density at cingulate gyrus and less negative ORN current density at sensory and motor areas characterized the alcoholics. Alcoholics had higher levels of impulsivity and risk-taking features than controls. Conclusions Deficient outcome/reward processing and increased impulsivity and risk-taking observed in alcoholics may be at least partly due to reward deficiency and/or dysfunctional reward circuitry in the brain, suggesting that alcoholism can be considered as part of the cluster of the reward deficiency syndrome (RDS).

The prescription opioid, oxycodone, does not alter behavioral measures of impulsivity in healthy volunteers

This study examined the effects of oral oxycodone, a prescription opioid, on several measures of impulsive behavior in healthy volunteers. Volunteers ( n = 12) participated in a four-session, double-blind, randomized design in which they received capsules containing oxycodone (5, 10, and 20 mg) or placebo. From 70 min to approximately 120 min after ingesting the capsules, subjects completed five impulsivity tasks: delay and probability discounting task, balloon analogue risk task (BART), go/no-go task, stop task, and simple reaction time test. Mood questionnaires were also completed at fixed time points in the sessions. Oxycodone produced prototypic changes in mood in a dose-related manner, but did not affect performance on any of the impulsivity tasks. Lack of effect on impulsivity stands in contrast to other studies in which other psychoactive drugs including ethanol, delta-9-tetrahydrocannabinol, and amphetamine altered behavior on one or more behavioral measures of impulsivity.

Impulsivity as a determinant and consequence of drug use: a review of underlying processes

Impulsive behaviors are closely linked to drug use and abuse, both as contributors to use and as consequences of use. Trait impulsivity is an important determinant of drug use during development, and in adults momentary 'state' increases in impulsive behavior may increase the likelihood of drug use, especially in individuals attempting to abstain. Conversely, acute and chronic effects of drug use may increase impulsive behaviors, which may in turn facilitate further drug use. However, these effects depend on the behavioral measure used to assess impulsivity. This article reviews data from controlled studies investigating different measures of impulsive behaviors, including delay discounting, behavioral inhibition and a newly proposed measure of inattention. Our findings support the hypothesis that drugs of abuse alter performance across independent behavioral measures of impulsivity. The findings lay the groundwork for studying the cognitive and neurobiological substrates of impulsivity, and for future studies on the role of impulsive behavior as both facilitator and a result of drug use.

Behavioral measures of impulsivity and the law

The General Theory of Crime proposes that crime is explained by the combination of situational opportunity and lack of self-control. Impulsivity is one of the important components of self-control. Because behavioral measures of impulsivity are becoming more commonly utilized to assess forensic populations, this manuscript provides an overview of three current behavioral measures. In doing so, an example of their application is provided using a group of individuals likely to come into contact with the legal system: adolescents with Conduct Disorder. Earlier age of onset of Conduct Disorder symptoms has been shown to be an important predictor of the persistence of poor outcomes into adulthood, including participation in criminal activities. This study found differential behavioral profiles across distinct measures of impulsivity by those with childhood- versus adolescent-onset Conduct Disorder. Legal implications for defining behavioral deficits using behavioral measures of impulsivity and their current limitations are discussed.

Impulsivity in Heroin Abstainers: Reaction Pattern Based on the Delay-Discounting Task and the Iowa Gambling Task

Impulsive drug-seeking has been one of typical characteristics of all drug-dependent individuals(Altman et al.,1996;Dawe et al.,2004;Dom,Hulstijn,et al., 2006),and questionnaire assessments based on self-reporting have been essentially taken as the conclusive metrical method of assessing impulsivity in the population.However,due to the varieties of meanings of "impulsivity"(Evenden,1999;Dougherty et al.,2005),the correlation between the results of self-reporting and those of laboratory tasks has been marginal,or even rather weak(Dom,D'Haene,et al.,2006;Moeller et al.,2001;Reynolds et al.,2006;Dom et al.,2007).Moreover,researchers have pointed out that behavioral measures of impulsivity may be a better predictor of relapse risk than any measure utilizing self-reporting.In laboratory methods used to assess impulsivity,the Delay-Discounting Task(DDT) and Iowa Gambling Task(IGT) have been widely adopted to explore the high impulsivity characteristic of drug-dependent individuals.The DDT was propitious in assessing "myopic" behavior for future values in humans(Green et al.,1994;Rachlin Siegel,1994;Kirby Herrnstein,1995),but the function of IGT has remained unclear,as is its relationship with that of DDT(Bartzokis et al.,2000;Bechara,2003;Monterosso et al.,2001;Dom et al.,2007).It is thus assumed in the present study that the high impulsivity characteristic of drug-dependent individuals is not only represented as a hyposensitivity to immediate rewards and an insensitivity to delayed value,but also as an immediate win-priority selection pattern and a tolerance to high risk.The present study explores the impulsive reaction patterns and the relationship in win-risk coincidence situations and delayed reinforcement situations in heroin abstainers in different abstinence phases. In the present study,61 male heroin abstainers(19~38 years old,M=29.25,SD=4.17) in a variety of abstinence phases(1~26 months,M=11.34,SD=7.09) and 32 normal male controls(18~39 years old,M=26.78,SD=7.18) were selected to undertake Chinese computerized versions of the IGT and DDT.In the IGT,subjects had to choose between four decks of cards.Unknown to the subjects,two piles offered high rewards but had potentially high losses,and hence were disadvantageous in the long run.The other two piles offered lower rewards but had much lower losses,and hence offered a net gain in the long run.In the DDT,subjects had to choose between hypothetical monetary rewards available immediately or following a delay.Delayed rewards were 1,000 and 10,000 in value,and the immediate-reward amount was adjusted until the choices reflected indifference.This process was repeated at each of eight delays(six hours to 25 years). The results of the present study showed that(1) reaction patterns for pure win-cards were consistent between heroin abstainers and normal controls;however,the former still preferred to choose high win-cards in spite of potential high punishment,whereas the latter tended to transform the direction of card selection after getting corresponding feedback,to avoid potentially high risks;(2) whether the delayed rewards were 1,000 or 10,000,the delay-discounting rates(k) of heroin abstainers were much higher than those of normal controls;(3) the delay-discounting rates based on the DDT were not correlated with the decision-making performance(net score) based on the IGT,but the former was partially correlated with the transform ratio of selecting cards after a net loss based on the IGT;and(4) the net score and transform ratio of card selection after a net loss based on the IGT and delay-discounting rates based on the DDT in heroin abstainers did not improve in line with the abstinence time course. From the present study,we conclude that(1) the impairment of the decisionmaking function in win-risk coincidence situations in heroin abstainers was demonstrated in their immediate win-priority selection pattern and tolerance to high risk;(2) the impairment of the decision-making function in delayed reinforcement situations in heroin abstainers was manifested in their hyposensitivity to immediate rewards and their insensitivity to delayed value,which led to a quick decay of long-time value;(3) the IGT was more sensitive to heroin abstainers' tolerance to risk,while the DDT was more efficient in evaluating their insensitivity to long-term value;both corresponded with two key variables of decision-making-namely,risk and delay;and(4) impulsivity in heroin abstainers did not improve in line with the abstinence time course.

Impulsive and non-impulsive suicide attempts in patients treated for alcohol dependence

BackgroundSuicidal behavior has been recognized as an increasing problem among alcohol-dependent subjects. The aim of the study was to identify correlates of impulsive and non-impulsive suicide attempts among a treated population of alcohol-dependent patients. MethodsA total of 154 patients with alcohol dependence consecutively admitted for addiction treatment participated in the study. Suicidal behavior was assessed together with severity of alcohol dependence, childhood abuse, impulsivity, and family history. A stop-signal procedure was used as a behavioral measure of impulsivity. Results and conclusionsLifetime suicide attempts were reported by 43% of patients in alcohol treatment; of which 62% were impulsive. Compared to patients without a suicide attempt, those with a non-impulsive attempt were more likely to have a history of sexual abuse (OR=7.17), a family history of suicide (OR=4.09), and higher scores on a personality measure of impulsiveness (OR=2.27). The only significant factor that distinguished patients with impulsive suicide attempts from patients without a suicide attempt and from patients with a non-impulsive suicide attempt was a higher level of behavioral impulsivity (OR=1.84–2.42). LimitationsRetrospective self-report of suicide attempts and family history. Lack of diagnostic measure.

Relation of individual differences in impulsivity to nonclinical emotional decision making

Impulsivity has been identified as a behavioral precursor to addiction, and may be the manifestation of a neurological vulnerability. The present study investigated whether individual differences in impulsivity were associated with performance on the Iowa Gambling Task (IGT, a test of emotional decision making thought to be associated in part with ventromedial prefrontal cortex function) and the Wisconsin Card Sorting Task (WCST, a set-shifting thought to be associated in part with dorsolateral prefrontal cortex function). Subjects were screened for impulsivity using the BIS-11 (self-report) and a delay discounting questionnaire (a behavioral measure of impulsivity). High impulsivity was associated with poorer performance on the final block of trials of the IGT but was not significantly related to WCST performance. Both measures were significantly correlated with scores on the BIS. These results provide support for hypothesis that, in a nonclinical sample, impulsivity may vary systematically with performance on neuropsychological indicators of prefrontal function.

A test of alcohol dose effects on multiple behavioral measures of impulsivity

Background Acute alcohol administration affects impulsive behavior, although these effects vary as a function of alcohol dose, assessment instrument, and time of measurement following administration. Methods We concurrently examined the dose-dependent effects of alcohol on three distinct types of impulsivity tasks (continuous performance [IMT], stop-signal [GoStop], and delay-discounting [SKIP] tasks). Ninety healthy alcohol drinkers were assigned to one of the three task groups ( n = 30 each), each group experienced placebo, 0.2, 0.4, 0.6, and 0.8 g/kg alcohol doses across 5 experimental days, and task performance was assessed at 0.5 h before and 0.25, 1.0, and 2.0 h after alcohol administration. We hypothesized that impulsive responding on all tasks would be increased by acute alcohol administration both across time and during the peak BrAC, but the magnitude would depend on the task being tested. Analyses included the time course and the peak BrAC effects. Task comparisons of peak behavioral changes following each dose are illustrated using standardized scores. Results While alcohol consumption increased impulsive responding during all three tasks to some extent, our hypothesis was only partially supported. During the IMT, the 0.6 and 0.8 g/kg doses produced increased impulsive responding across time and at the peak BrAC. However, during the GoStop and SKIP, impulsivity increased across time regardless of the alcohol dose size, with no differences in impulsive responding among dose conditions at peak BrAC. Conclusions This study demonstrated alcohol-induced changes in impulsivity are not uniformly affected by alcohol. These data, in conjunction with previous studies, further support that impulsivity is not a unitary construct.

Dimensions of impulsive behavior in adolescents: Laboratory behavioral assessments.

Impulsivity is a multifaceted construct that defines a range of maladaptive behavioral styles. The present research aimed to identify different dimensions of impulsive behavior in adolescents from a battery of laboratory behavioral assessments. In one analysis, correlations were examined between two self report and seven laboratory behavioral measures of impulsivity. The correlation between the two self report measures was high compared to correlations between the self report and laboratory behavioral measures. In a second analysis, a principal components analysis was performed with just the laboratory behavioral measures. Three behavioral dimensions were identified -- "impulsive decision-making", "impulsive inattention", and "impulsive disinhibition". These dimensions were further evaluated using the same sample with a confirmatory factor analysis, which did support the hypothesis that these are significant and independent dimensions of impulsivity. This research indicates there are at least three separate subtypes of impulsive behavior when using laboratory behavioral assessments with adolescent participants.

The role of behavioural measures of impulsivity in the development of alcohol dependence

Background:The link between impulsivity and alcohol use disorders has been established in longitudinal and cross-sectional studies, but little is know about the role of behavioural impulsivity in the development of substance use disorders.Objectives:Determine the role of behavioural measures of impulsivity in the development of alcohol use disorders.Design and measurements:A prospective cohort study was conducted to identify the risk factors associated with alcohol dependence. Non-dependent heavy drinkers (N=471) and healthy controls (N=149) were recruited from primary care centres. They were assessed at the end of the 4-year follow-up period. Diagnoses were rendered using the Structured Interview for DSM-IV. The continuous performance test (CPT) and stop-signal task (SST) assessed behavioural inhibition. Differential reinforcement for low-rate responding (DRLR) was used to evaluate the delay discounting dimension.Results:HD participants have significant impairments on all laboratory measures of impulsivity. In the logistic regression model, impairment on DRLR (delay discounting dimension) was the only measure that classified accurately HD. Baseline behavioural measures of impulsivity correlated positively with amount of alcohol consumption during the follow-up period. Logistic regression analysis indicated that performance on inhibitory control (SST) (behavioural inhibition dimension) was a significant predictor (odds=1.52[1.08-2.31]) for developing alcohol dependence.Conclusions:Our data support the link between behavioural measures of impulsivity and alcohol use disorders. Delay discounting dimension may be a risk factor for begin alcohol use heavily and behavioural inhibition impairment is more involved in the development of dependence.

The relationship between impulsivity and Internet addiction in a sample of Chinese adolescents

Objective Previous studies regarding Internet addiction have investigated associated psychological variables such as shyness, loneliness, self-consciousness, anxiety, depression and interpersonal relations. Few studies about the relationship between Internet Addiction and impulsivity have been done. This study aimed to assess whether Internet addiction is related to impulsivity among Chinese adolescents. Method This study was performed in two stages. We screened for the presence of Internet Addiction among 2620 high school students(age ranging from 12 years to 18 years) from four high schools of Changsha City using Diagnostic Questionnaire for Internet Addiction (YDQ). According to the modified YDQ criteria by Beard, 64 students were diagnosed as Internet addiction. Excluding current psychiatric comorbidity, 50 students who were diagnosed as Internet Addiction (mean age, 14.8 ± 1.4 years) and 50 normal students in Internet usage(mean age, 14.5 ± 1.8 years) were included in a case control study. The two groups were assessed using Barratt Impulsiveness Scale 11 (BIS-11) and behavioral measure of impulsivity (GoStop Impulsivity Paradigm). Results Sixty-four students met the modified YDQ criteria by Beard, of whom 14 students suffered from comorbid psychiatric disorders, especially comorbid ADHD. The Internet Addiction group had significantly higher scores on the BIS-11 subscales of Attentional key, Motor key, and Total scores than the control group ( P < 0.05). The Internet Addiction group scored higher than the control group on the failure to inhibit responses of GoStop Impulsivity Paradigm ( P < 0.05). There was a significant positive correlation between YDQ scores and BIS-11subscales and the number of failure to inhibit responses of GoStop Impulsivity Paradigm. Conclusion This study suggests that adolescents with Internet addiction exhibit more impulsivity than controls and have various comorbid psychiatric disorders, which could be associated with the psychopathology of Internet addiction.

Interactive Effects of Sex and 5-HTTLPR on Mood and Impulsivity During Tryptophan Depletion in Healthy People

Serotonin (5-HT) plays a central role in mood regulation and impulsivity. We studied whether healthy men and women react differently on mood and impulsivity measures during acute tryptophan depletion (ATD). We also studied the relative contribution of a functional length triallelic polymorphism in the promoter region of the serotonin transporter, designated 5-HTTLPR, to the behavioral responses to ATD. Thirty-nine men and 44 women participated in a randomized, double-blind, parallel group ATD study. Behavioral measures of impulsivity and mood were obtained. During ATD, women reported mood reduction and showed a cautious response style, which is commonly associated with depression. Men showed an impulsive response style and did not report mood reduction. The 5-HTTLPR influenced the mood response to ATD in women. Healthy men became more impulsive, whereas healthy women showed mood reduction in response to ATD. This suggests that 5-HT could be one mechanism contributing to the sex differences in the prevalence of mood and impulsivity disorders. The influence of 5-HTTLPR on mood responses in women further substantiates the relevance of this variant in the pathophysiology of at least a subgroup of patients with major depressive disorder.

Examining impulsivity as an endophenotype using a behavioral approach: a DRD2 TaqI A and DRD4 48-bp VNTR association study

BackgroundResearch on the genetic basis for impulsivity has revealed an array of ambiguous findings. This may be a result of limitations to self-report assessments of impulsivity. Behavioral measures that assess more narrowly defined aspects of impulsivity may clarify genetic influences. This study examined the relationship between possession of the DRD2 TaqI A and DRD4 48 bp VNTR genetic polymorphisms and performance on a behavioral measure of impulsivity, the delay discounting task (DDT), and three traditional self-report measures.Methods195 individuals (42% male) were recruited from a university campus and were assessed in small group sessions using personal computers. Genotyping was conducted using previously established protocols. For the DRD2 TaqI A locus, individuals were designated as possessing at least one copy of the A1 allele (A1+) or not (A1-), and for the DRD4 48-bp VNTR locus, individuals were designated as having at least one long allele (7 repeats or longer, L+) or not (L-). Principal analyses used multiple univariate factorial 2 (A1+/A1-) × 2 (L+/L-) analyses of variance.ResultsA significant main effect of A1+ status on DDT performance was evident (p = .006) as well as a significant interaction effect (p = .006) between both genes. No other significant effects were evident on the self-report measures, with the exception of a trend toward an interaction effect on the Sensation Seeking Scale. Exploratory analyses suggested that the significant effects were not a function of population stratification or gender.DiscussionThese data suggest that the DRD2 TaqI A and DRD4 VNTR polymorphisms influence impulsivity as measured with a delay discounting task. Specifically, these findings suggest that an interaction between the functional effects of the two unlinked genotypes results in significant difference in the balance of mesolimbic dopaminergic activation relative to frontal-parietal activation. However, these findings are also the first in this area and must be replicated.ConclusionThese findings suggest a meaningful interaction between the DRD2 TaqI A and DRD4 VNTR polymorphisms in the expression of impulsivity and provide initial support for the utility of using behavioral measures for clarifying genetic influences on impulsivity.

Behavioral impulsivity predicts treatment outcome in a smoking cessation program for adolescent smokers

Objective To examine the relationship between impulsivity and smoking cessation treatment response among adolescents. Methods Thirty adolescent smokers participated in a high school based smoking cessation program combining contingency management and cognitive behavioral therapy. Self-report (Barratt impulsiveness scale (BIS-II); Kirby delay discounting measure (DDM)) and behavioral (experiential discounting task (EDT); continuous performance task (CPT)) measures of impulsivity were assessed at treatment onset. Results Sixteen participants (53%) were abstinent from smoking at completion of the four-week study. Compared to abstinent adolescents, those not achieving abstinence discounted monetary rewards more on the EDT and committed more commission errors on the CPT. Group differences were not observed on the BIS-II or DDM. Conclusions These preliminary results suggest that specific behavioral measures of impulsivity may be associated with the ability to initiate and/or maintain abstinence from smoking among adolescent smokers.

Relationship between limbic and cortical 5-HT neurotransmission and acquisition and reversal learning in a go/no-go task in rats

Specific brain structures have been suggested to be involved in impulsive responding assessed by a variety of operant tasks. Central serotonin (5-HT) function has also been widely implicated in impulsivity; however, little research has addressed the regional aspect of 5-HT roles in different impulsive indices of task performance. We analyzed the relationships between acquisition and reversal learning in a go/no-go task as different behavioral measures of impulsivity and focal concentrations of 5-HT and its metabolites in the brain. Rats administered with parachloroamphetamine (PCA) and vehicle were tested in both acquisition and reversal phases in a go/no-go visual discrimination task. Neurochemical analysis was performed to determine 5-HT concentrations in micropunched brain tissues. PCA administration induced regionally 5-HT depletion in the brain and impaired learning performance in both tests. For both tests, significant negative correlations between learning performance and 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) concentrations were observed in the medial prefrontal cortex (mPFC) and amygdala (Amyg). In contrast, significant negative correlations between learning performance and 5-HT and 5-HIAA concentrations were observed for the orbitofrontal cortex (OFC) exclusively in the reversal learning phase. The present data indicate that 5-HT neurotransmission to the mPFC and Amyg is involved in inhibitory control over responses to discriminated stimuli associated with the go/no-go paradigm common to both tests. In contrast, 5-HT neurotransmission to the OFC is especially involved in additional processes associated with reversal learning.

Individual differences in drug abuse vulnerability: d-Amphetamine and sensation-seeking status

While the personality dimensions of novelty seeking and sensation seeking are associated with drug abuse vulnerability, the mechanisms associated with this vulnerability remain obscure. This study examined the behavioral effects of d-amphetamine in healthy volunteers scoring in the upper and lower quartiles based on age- and gender-adjusted population norms on the impulsive Sensation-Seeking Scale (SSS) of the Zuckerman-Kuhlman personality questionnaire (ZKPQ). Participants completed 7-day outpatient studies examining the subjective, performance, and cardiovascular effects of d-amphetamine (0, 7.5, and 15 mg/70 kg, p.o.) under double-blind conditions according to a randomized block design. Performance tasks included behavioral measures of impulsivity, including attention, inhibition, and risk-taking behavior. No differences in baseline performance or d-amphetamine effects on measures of attention, inhibition, and risk-taking behavior were observed. High impulsive sensation seekers reported greater increases on several subjective report measures associated with drug abuse potential, including visual analog scales feel drug, like drug, and high. Healthy adults scoring in the top quartile on the population of the impulsive SSS of the ZKPQ may be vulnerable to the abuse potential of d-amphetamine.

Measuring Impulsivity in Adolescents With Serious Substance and Conduct Problems

Adolescents with substance use and conduct disorders have high rates of aggression and attention deficit hyperactivity disorder (ADHD), all of which have been characterized in part by impulsivity. Developing measures that capture impulsivity behaviorally and correlate with self-reported impulsivity has been difficult. One promising behavioral measure, however, is a variant of the continuous performance test, the Immediate Memory Test/Delayed Memory Test (IMT/DMT). The authors showed significant group differences between adolescents in treatment for serious substance and conduct problems and community controls on impulsivity measures, both behavioral and self-report, as well as on aggression and problem behavior measures. Furthermore, the IMT/DMT correlated significantly with self-reported impulsivity. In summary, the IMT/DMT may be an effective behavioral measure of impulsivity in adolescents.

Diazepam impairs behavioral inhibition but not delay discounting or risk taking in healthy adults.

There are reports that diazepam can increase, decrease, or have no effect on measures of impulsive behavior, which may be related, in part, to differences among the tasks used to measure impulsivity. This study examined the effects of a relatively high dose of diazepam (20 mg) on 5 measures of impulsive behavior in healthy adult men and women. Volunteers (N = 18) participated in a 2-session double-blind randomized design in which they received 20 mg diazepam or placebo. One hour after ingesting the capsule, participants completed mood questionnaires and several impulsivity tasks to measure subtypes of impulsive behavior, including behavioral inhibition, delay and probability discounting, and risk taking. Diazepam impaired behavioral inhibition but had no effect on measures of discounting or risk taking. These results are discussed in the context of other recent findings suggesting that different behavioral indices of impulsivity are dissociable and governed by separate underlying mechanisms.

Acute Effects of 3,4-Methylenedioxymethamphetamine (MDMA) on Behavioral Measures of Impulsivity: Alone and in Combination with Alcohol

The use of 3,4-methylenedioxymethamphetamine (MDMA) has frequently been associated with increased levels of impulsivity during abstinence. The effects of MDMA on measures of impulsivity, however, have not yet been studied during intoxication. The present study was designed to assess the acute effects of MDMA and alcohol, alone and in combination, on behavioral measures of impulsivity and risk-taking behavior. A total of 18 recreational users of MDMA entered a double-blind placebo-controlled six-way crossover study. The treatments consisted of MDMA 0, 75, and 100 mg with and without alcohol. Alcohol dosing was designed to achieve a peak blood alcohol concentration (BAC) of about 0.06 g/dl during laboratory testing. Laboratory tests of impulsivity were conducted between 1.5 and 2 h post-MDMA and included a stop-signal task, a go/no-go task, and the Iowa gambling task. MDMA decreased stop reaction time in the stop-signal task indicating increased impulse control. Alcohol increased the proportion of commission errors in the stop-signal task and the go/no-go task. Signal detection analyses of alcohol-induced commission errors indicated that this effect may reflect impairment of perceptual or attentive processing rather than an increase of motor impulsivity per se. Performance in the Iowa gambling task was not affected by MDMA and alcohol, but there was a nonsignificant tendency towards improvement following alcohol intake. None of the behavioral measures of impulsivity showed a MDMA x alcohol interaction effect. The lack of interaction indicated that the CNS stimulant effects of MDMA were never sufficient to overcome alcohol-induced impairment of impulse control or risk-taking behavior.