Oleg V. Tcheremissine

Relationships among laboratory and psychometric measures of impulsivity: Implications in substance abuse and dependence.

Objectives Problems with impulsive behavior are a key feature in substance use disorders. Many studies have examined this relationship, but methods used to measure impulsivity have varied greatly. The present study used a multimethod approach to determine relationships using both laboratory and psychometric measures of impulsivity commonly employed in the behavioral and health sciences. Methods Thirty-two adult male subjects participated for 5 days, completing psychometric instruments on day 1 and behavioral tests in counterbalanced order on days 2–5. Results Correlations between the behavioral and psychometric measures were uniformly low. Correlations within the psychometric instruments were consistently high. Principal components analysis revealed that the behavioral measures loaded into separate factors of response inhibition tasks and delay of reward tasks. Psychometric measures loaded into a single factor. Conclusions Results are discussed in terms of how studies of impulsivity might be interpreted based upon the tasks used, and how these interpretations may subsequently guide theory and measurement in substance abuse and dependence.

Acute marijuana effects on human risk taking.

Previous studies have established a relationship between marijuana use and risky behavior in natural settings. A limited number of laboratory investigations of marijuana effects on human risk taking have been conducted. The present study was designed to examine the acute effects of smoked marijuana on human risk taking, and to identify behavioral mechanisms that may be involved in drug-induced changes in the probability of risky behavior. Using a laboratory measure of risk taking designed to address acute drug effects, 10 adults were administered placebo cigarettes and three doses of active marijuana cigarettes (half placebo and half 1.77%; 1.77%; and 3.58% Δ9-THC) in a within-subject repeated-measures experimental design. The risk-taking task presented subjects with a choice between two response options operationally defined as risky and nonrisky. Data analyses examined cardiovascular and subjective effects, response rates, distribution of choices between the risky and nonrisky option, and first-order transition probabilities of trial-by-trial data. The 3.58% THC dose increased selection of the risky response option, and uniquely shifted response probabilities following both winning and losing outcomes following selection of the risky option. Acute marijuana administration thereby produced measurable changes in risky decision making under laboratory conditions. Consistent with previous risk-taking studies, shifts in trial-by-trial response probabilities at the highest dose suggested a change in sensitivity to both reinforced and losing risky outcomes. Altered sensitivity to consequences may be a mechanism in drug-induced changes in risk taking. Possible neurobiological sites of action related to THC are discussed.

Measurement of delay discounting using trial-by-trial consequences

DELAY DISCOUNTING IN HUMANS WAS INVESTIGATED USING THREE DIFFERENT PROCEDURES: a frequently used discounting procedure with hypothetical rewards and delays; a procedure with hypothetical rewards and delays compressed down to much smaller values; and a contingent procedure in which each choice had a direct consequence. In the contingent procedure, on every trial, participants actually experienced the delay and obtained the reward amount associated with their choice. Each participant was exposed to all three procedures. Orderly temporal discounting patterns were obtained in all three procedures and described well by a hyperbolic model. Comparisons of the data revealed patterns unique to each procedure. The distributions of the discounting measures differed across the three procedures. In the contingent procedure, several subjects showed no discounting, e.g. complete self-control. Procedural factors in studies of impulsivity are discussed, and suggestions are offered for experiments in which the contingent-discounting procedure may prove useful.

Pharmacological Aspects of the Treatment of Conduct Disorder in Children and Adolescents

In recent years, the rates of psychosocial disorders in children and adolescents have increased, with behavioural manifestations of conduct disorder being one of the most common reasons for referrals to community psychiatrists. Childhood conduct problems are associated with a variety of psychiatric disorders in adult life that extend beyond antisocial behaviour. An increased awareness of the costs of conduct disorder to individuals, families and society has led to advancements in the pharmacological and nonpharmacological therapeutic modalities for this disorder. Despite this, patients with conduct disorder are difficult to treat as the patterns of maladaptive behaviours they exhibit are diverse and can vary as a function of age and sex. A multidisciplinary approach to the treatment of conduct disorder, which includes behavioural parent training, interpersonal skills training, family therapy and the use of psychotropic agents targeted at a particular cluster of symptoms, can increase the overall effectiveness of each of the applied interventions. Aggression, hyperactivity, impulsivity and mood symptoms are the most sensitive proximal targets.Evidence suggests that antipsychotics, antidepressants, mood stabilisers, antiepileptic drugs, stimulants and adrenergic drugs can be well tolerated and effective therapeutic options for individuals with conduct disorder and comorbid psychiatric conditions. However, the most successful therapeutic outcomes are likely to be achieved by combining the current advances in psychopharmacology with behavioural and psychosocial interventions, aimed at modifying the excessive patterns of maladaptive behaviours observed in conduct disorder.

Effects of acute tiagabine administration on aggressive responses of adult male parolees

Experimental and clinical studies have supported a relationship between γ-aminobutyric acid (GABA) and aggressive behavior in non-humans and humans. Tiagabine is a GABA uptake inhibitor that has been shown to produce acute behavioral effects in animals. In addition, tiagabine has been shown to decrease aggression in agitated patients when administered chronically. The present study was designed to investigate the effects of acute administration of tiagabine on aggressive responding on a laboratory task in adult humans. Ten adult males participated in experimental sessions on the Point Subtraction Aggression Paradigm (PSAP), which provided subjects with aggressive, escape, and monetary-reinforced response options. All subjects received four acute oral doses of Tiagabine (4, 8, 12 and 16 mg) separated by placebo sessions. Tiagabine decreased aggression at doses that either did not affect, or affected to a lesser extent, monetary-reinforced responding. The results are consistent with some prior research using the PSAP showing a possible unique role for GABA in the regulation of human aggression. A possible behavioral mechanism for the rate-decreasing effects on aggressive responding produced in the present study is that tiagabine may modify aggressive responding by suppressing reactions to aversive stimuli.

Pharmacotherapy of adult attention deficit/hyperactivity disorder: review of evidence-based practices and future directions

Background: Attention deficit/hyperactivity disorder (ADHD) is the most commonly diagnosed psychiatric disorder in children and adolescents with well-known clinical consequences and functional outcomes that affect individuals throughout their lifespan. The diagnosis of adult ADHD is often a clinical diagnosis made on the basis of behavioral symptoms that begin early in life, and persist over time across different settings. Objective: Although pharmacotherapy is a first-line treatment option for ADHD across all age groups, there is a relative paucity of well-designed and well-controlled studies evaluating the treatment outcomes in adult ADHD. In this review, evidence-based pharmacotherapy of adult ADHD and directions of future research are critically examined. Methods: A literature search from 1980 to 2007, restricting papers to English, using PUBMED and PsychInfo was performed. Studies were examined based on empirically derived criteria. Results: The reviewed body of evidence strongly supports the use of pharmacotherapy as a first-line therapeutic option for the treatment of adults with ADHD.

Effects of delays on human performance on a temporal discrimination procedure: evidence of a choose-short effect

Studies of temporal discrimination in non-human subjects have reliably shown a choose-short effect: higher matching accuracy on short-duration-sample trials than on long-duration-sample trials. This effect occurs as a function of increasing the delay between the onset of sample and comparison stimuli in a delayed matching-to-sample procedure. The present experiment investigated whether the choose-short effect could be demonstrated in human subjects under conditions which paralleled those used with non-human subjects. Subjects responded under a discrete-trial procedure in which they were required to push one of two buttons depending on the duration of a sample stimulus (a blue square on a computer monitor). Delays (0, 8, 16, and 32s) separated sample and comparison stimuli (two white boxes) and were tested both within and across several sessions. Intermediate durations (probe stimuli between 2 and 4s) were also presented. The addition of a delay between the sample and comparison stimuli produced a bias to judge intervals as short when the 8 and 32-s delays were tested across sessions and when the 0, 16, and 32-s delays were tested within the same session. Thus, the choose-short effect was produced in human subjects using the interval bisection procedure regardless of delay length.

Impulsiveness and other personality dimensions in substance use disorders and conduct disorder

ObjectivesThe psychometric measurement of personality and behavior traits may inform both basic research and clinical practice in substance abuse research. Relationships among novelty seeking, harm avoidance, reward dependence, impulsivity and venturesomeness, and conduct disorder were examined in a group of subjects with a past diagnosis of a substance use disorder and controls. MethodsPsychometric data from 68 subjects were analyzed using Analysis of Variance and logistic regression. ResultsStatistical analyses demonstrated that individuals meeting criteria for a past substance use disorder showed lower reward dependenceand greater impulsivity than controls, when controlling for the presence of conduct disorder. A substance use disorder x conduct disorder interactionwas found on the dimensions of harm avoidance and venturesomeness. ConclusionsLogistic regression revealed that a past substance use disorder could be predictedfrom the combination of two factors: low reward dependence and nonplanning impulsivity. Results are discussed in the context of previous data on personality dimensions and substance abuse.

Risk reduction and resource pooling on a cooperation task

AbstractTwo experiments investigated choice in adult humans on a simulated cooperation task to evaluate a risk-reduction account of sharing based on the energy-budget rule. The energy-budget rule is an optimal foraging model that predicts risk-averse choices when net energy gains exceed energy requirements (positive energy budget) and risk-prone choices when net energy gains fall below energy requirements (negative energy budget). Because sharing can minimize variability in energy gain (i.e., is a risk-averse strategy), the model predicts that sharing should occur under positive but not negative budget conditions. Energy budgets were modeled by substituting money gains for energy gains and earnings requirements for energy requirements. Participants chose between work- alone or work-with-others (sharing) response options. Experiment 1 investigated the effects on choice of manipulating the value of the earnings requirement and the presence of the partner’s money counter. Choice for the sharing option varied as a function of the earnings requirement in a pattern consistent with the predictions of the energy-budget rule. The presence of the partner’s money counter did not influence preference. Experiment 2 replicated Experiment 1 and also showed that under conditions with no earnings requirement (conditions in which the energy-budget rule makes no predictions), subjects often preferred the sharing option over the independent option when sharing increased the partner’s 13arnings, and that subjects often preferred an independent option over the sharing option when the independent option produced a constant earnings amount. Overall, the results replicate and extend the results of earlier earnings-budget studies and further show that laboratory procedures are useful for evaluating the plredictions of risksensitive and social-foraging models.

Individual differences in aggressive responding to intravenous flumazenil administration in adult male parolees

Nonhuman and human studies have shown that benzodiazepine (BZD) receptor agonists can modify aggressive behaviour. However, it is unknown whether flumazenil, a BZD receptor antagonist, enhances or inhibits aggressive behaviour. The present study was designed to investigate the effects of acute administrations of flumazenil on aggressive responding in adult humans. Six adult males with histories of childhood conduct disorder (DSM IV R) participated in experimental sessions. Aggression was measured using the Point Subtraction Aggression Paradigm (PSAP; Cherek 1992), which provided subjects with aggressive and monetary-reinforced response options. Acute doses of flumazenil (2 and 3mg) did not produce statistically significant changes in either monetary-reinforced responding or aggressive responding. The analysis of individual subjects data revealed that aggressive responses varied across subjects. The results are discussed in terms of individual differences based on the previous history of BZD abuse. Additional laboratory research is needed to better clarify the behavioural mechanisms by which BZD receptor antagonists modify human aggressive responding.