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PubMed1977

Efficacy of monophasic electrical impulses with steep leading and trailing edges in cardiac defibrillation.

Experiments on dogs were performed to investigate the efficacy of various defibrillation impulse waveforms. The results showed that the decisive factors for the effectiveness of the defibrillation impulse of certain shape are its relationship to the carciac tissue accomodation and the duration of the suprathreshold current flow. For cardiac defibrillation the most convenient impulse is therefore the impulse with the highest rate of rise of the leading edge as well as the trailing edge. The amplitude of the rear trailing edge of the defibrillation impulse should be either equal or higher than the amplitude of the front leading edge. That means that rectangular or trapezoidal impulses with an ascending slope may be most conveniently used for cardiac defibrillation. The biologically optimal duration of the trapezoidal impulse with an ascending slope proved to range from 7 to 14 msec. The authors emphasize the inevitability of additional characteristics of the defibrillation impulse by its peak current and total energy contents.

Animals↗

PubMed1995

Factor structure of the Barratt impulsiveness scale.

The purpose of the present study was to revise the Barratt Impulsiveness Scale Version 10 (BIS-10), identify the factor structure of the items among normals, and compare their scores on the revised form (BIS-11) with psychiatric inpatients and prison inmates. The scale was administered to 412 college undergraduates, 248 psychiatric inpatients, and 73 male prison inmates. Exploratory principal components analysis of the items identified six primary factors and three second-order factors. The three second-order factors were labeled Attentional Impulsiveness, Motor Impulsiveness, and Nonplanning Impulsiveness. Two of the three second-order factors identified in the BIS-11 were consistent with those proposed by Barratt (1985), but no cognitive impulsiveness component was identified per se. The results of the present study suggest that the total score of the BIS-11 is an internally consistent measure of impulsiveness and has potential clinical utility for measuring impulsiveness among selected patient and inmate populations.

Analysis of Variance↗

PubMed2002

Deficits in impulse control associated with tonically-elevated serotonergic function in rat prefrontal cortex.

Converging lines of evidence suggest that dysfunction of brain serotonergic systems may underlie impulsive behavior. However, the nature of this deficit remains poorly understood because indirect indices of serotonin (5-HT) function are often used in clinical and experimental studies. In this investigation we measured 5-HT release directly in the prefrontal cortex of rats using in vivo microdialysis during performance of a visual attentional task. A number of performance measures were taken, including the number of premature responses made during the inter-trial interval before the onset of the visual discriminanda. This form of behavioral disinhibition was defined as impulsive, after. Lengthening the inter-trial interval increased the sensitivity of the task for detecting impulsive tendencies. Cortical levels of 5-HT and its metabolite 5-HIAA remained at pre-task levels over 1 h of task performance. By contrast, levels of dopamine (DA) and its metabolite DOPAC increased during this period. Regression analysis established a positive relationship between premature (impulsive) responses and 5-HT efflux, both under basal (r = 0.49) and task-related (r = 0.42) conditions (n = 31). No such relationship was found for prefrontal levels of DA. However, post-mortem analysis revealed that animals that were more impulsive had a higher turnover of DA in anterior cingulate, prelimbic and infralimbic cortices but no detectable abnormalities in 5-HT function. These data indicate that elevated 5-HT release in the prefrontal cortex may underlie deficits in impulse control on this task. Additionally, DA dysfunction in this region may be another, possibly independent, trait marker of impulsivity.

Animals↗

PubMed1998

5-hydroxytryptamine and impulse control: prospects for a behavioural analysis.

Impulsiveness is a significant clinical problem associated with a variety of psychiatric and neuropsychiatric disorders. Clinical and experimental studies have provided evidence that individuals displaying impulsive behaviour tend to show signs of deficient functioning of the ascending 5-hydroxytryptaminergic (5-HTergic) pathways of the brain. A persistent problem in investigations of the biological basis of impulsive behaviour has been the lack of a satisfactory definition of 'impulsiveness', as distinct from other behavioural features, such as aggression, which are often apparent in 'impulsive' individuals. Research in the experimental analysis of behaviour suggests that two important characteristics of 'impulsiveness' are (i) deficient tolerance of delay of gratification and (ii) inability to inhibit or delay voluntary behaviour; both of these characteristics are amenable to study in laboratory animals. We describe some delayed reinforcement and delayed response paradigms which purport to capture these behavioural characteristics, and review recent evidence that manipulation of 5-HTergic function alters behaviour in these paradigms. It is argued that the two characteristics of 'impulsiveness' are themselves the product of disturbance of more fundamental behavioural processes; the nature of these processes is considered.

Animals↗

PubMed2002

Blunted prefrontal cortical 18fluorodeoxyglucose positron emission tomography response to meta-chlorophenylpiperazine in impulsive aggression.

BACKGROUND: Impulsive aggression is a prevalent problem and yet little is known about its neurobiology. Preclinical and human studies suggest that the orbital frontal cortex and anterior cingulate cortex play an inhibitory role in the regulation of aggression. METHODS: Using positron emission tomography, regional metabolic activity in response to a serotonergic stimulus, meta-chlorophenylpiperazine (m-CPP), was examined in 13 subjects with impulsive aggression and 13 normal controls. The anterior cingulate and medial orbitofrontal regions were hypothesized to respond differentially to m-CPP in patients and controls. In the frontal cortex, regional metabolic glucose response to m-CPP was entered into a group (impulsive aggressive, control) x slice (dorsal, middle, orbital) x position (medial, lateral) x location (anterior, posterior) x hemisphere (right, left) mixed-factorial analysis of variance design. A separate group (impulsive aggressive, controls) x anteroposterior location (Brodmann areas 25, 24, 31, 29) x hemisphere (right, left) analysis of variance was used to examine regional glucose metabolism in the cingulate gyrus. RESULTS: Unlike normal subjects, patients with impulsive aggression did not show activation specifically in the left anteromedial orbital cortex in response to m-CPP. The anterior cingulate, normally activated by m-CPP, was deactivated in patients; in contrast, the posterior cingulate gyrus was activated in patients and deactivated in controls. CONCLUSIONS: The decreased activation of inhibitory regions in patients with impulsive aggression in response to a serotonergic stimulus may contribute to their difficulty in modulating aggressive impulses.

Aggression↗

PubMed2004

Impulsivity as a risk factor for eating disorder behavior: assessment implications with adolescents.

OBJECTIVE: The aims of the current study were to determine if impulsivity serves as a risk factor for eating disorder behavior and to examine whether different risk outcomes are obtained depending on the assessment strategy used to measure impulsivity. METHOD: Three independent studies are reported, each of which examined the relationship of impulsivity and eating disorder behavior in a prospective longitudinal design with adolescent subjects recruited from both public and private schools. Individuals displaying eating disorder behavior at initial assessments were not included in the analyses, to ensure that we were testing the role of impulsivity in the onset of eating disorder behavior. RESULTS: Trait impulsivity, measured with traditional personality scales, failed to predict the onset of eating disorder behavior in all three studies. However, when behavioral constructs associated with impulsivity, such as delinquency or substance abuse, were examined, they significantly predicted the onset of eating disorder behavior in most of the analyses conducted. DISCUSSION: These results provide moderate support for the idea that impulsivity serves as a risk factor for the onset of eating disorder behavior. However, this is only true when more objective behavioral measures were utilized.

Adolescent↗

PubMed2004

Effects of negative mood induction and impulsivity on self-perceived emotional eating.

OBJECTIVE: The current study investigates the influence of negative mood induction and impulsivity on self-perceptions with respect to emotional eating. Negative affect as well as high impulsivity was expected to increase levels of self-perceived emotional eating. METHOD: College students who were high versus low in impulsivity were assigned randomly to either a negative (failure on a quiz) or a neutral mood induction. Their levels of self-perceived emotional eating were measured after and before mood induction. RESULTS: Negative affect appeared to enhance the level of self-perceived emotional eating significantly (p < .01). There was no statistically significant effect of impulsivity. The interaction effect of affect and impulsivity approached significance (p = .08), indicating that highly impulsive subjects compared with subjects low in impulsivity were more strongly influenced by negative affect in self-perceived emotional eating. DISCUSSION: Negative affect substantially influences self-perceptions in terms of emotional eating, which is relevant for both prevention and treatment.

Adolescent↗

PubMed2005

Impulsivity as an underlying factor in the relationship between disordered eating and sexual behavior.

OBJECTIVE: Previous research has reported associations between bulimia nervosa (BN), increased sexual activity, and impulsivity. However, most studies have examined these topics separately and have not examined the role of impulsivity in associations between bulimic and sexual behaviors. The current study sought to examine relationships between disordered eating, sexual behaviors, and impulsivity, as well as to investigate impulsivity as a third variable in these relationships. METHOD: The participants were 500 female undergraduate students from a large midwestern university who completed self-report questionnaires of binge eating, the use of compensatory behavior, sexual behavior, and impulsivity. RESULTS: Compensatory behavior, but not binge eating, was significantly correlated with sexual experiences. Partial correlations indicated that impulsivity is a third variable that partially underlies this relationship. CONCLUSION: Compensatory behaviors and increased sexual activity likely represent risky behaviors that are influenced by impulsivity levels.

Adolescent↗

PubMed1999

Effects of methamphetamine on the adjusting amount procedure, a model of impulsive behavior in rats.

RATIONALE: Moderate doses of d-amphetamine (given both acutely and chronically) have been shown to decrease impulsivity in children with attention deficit hyperactivity disorder (ADHD) and to improve attention and learning in normal adults. In contrast, chronic doses of methamphetamine (METH) in drug abusers have been associated with increased impulsivity, and impairments in learning and attention. OBJECTIVES: We report the effects of METH on an animal model of impulsive behavior. METHODS: Rats were tested using the adjusting amount (AdjAmt) procedure in which the animals choose between a delayed fixed (large) amount of water and an immediate adjusting (small) amount of water. In the acute METH study, rats were given a single dose of 0.5, 1.0, 2.0, and 4.0 mg/kg METH or saline 30 min before testing. In the chronic METH study, we determined the effects of the 4.0 mg/kg dose of METH injected chronically 1 h after behavioral testing for 14 days. Thus the rats were tested using the AdjAmt procedure 22 h after injections of METH or saline. RESULTS: After 0.5, 1.0 and 2.0 mg/kg METH, the rats valued the delayed large rewards more than after saline, indicating that the METH decreased impulsiveness. At the 4.0 mg/kg dose, the rats failed to respond. Rats treated repeatedly with the post-session large behaviorally disruptive dose of METH valued the delayed large rewards less than the saline-treated rats, indicating that this dosing regimen of METH increased impulsiveness. CONCLUSIONS: In these experiments, the rats became less impulsive after acute non-disruptive doses of pre-session METH, whereas they became more impulsive after receiving repeated post-session injections of a dose that was behaviorally disruptive when administered acutely.

Animals↗

PubMed1999

Effects of d,l-fenfluramine on aggressive and impulsive responding in adult males with a history of conduct disorder.

RATIONALE: The role of serotonin in aggression and impulsivity was examined by administering the serotonin-releasing drug, d, l-fenfluramine and measuring effects on aggressive and impulsive responding under controlled laboratory conditions. METHODS: Ten male subjects with a history of conduct disorder and criminal behavior participated in experimental sessions, which measured aggressive and impulsive responses. Aggression was measured using the Point subtraction Aggression paradigm (PSAP), which provides subjects with an aggressive, escape and monetary reinforced response options. Impulsive responses were measured using a paradigm which provided subjects with choices between small rewards after short delays versus larger rewards have long delays. RESULTS: Acute challenge doses (0.2,0.4 and 0.8 mg/kg) of d,l-fenfluramine produced significant dose-dependent decreases in aggressive and impulsive responses. Escape and monetary reinforced responses were not significantly changed. Decreases in aggressive responses were therefore selective, because escape responses were not affected, and could not be attributed to a non-specific sedative action because monetary reinforced responses were slightly increased. CONCLUSIONS: Release of serotonin and/or reuptake blockade by d,l-fenfluramine is the possible mechanism for reductions in aggression and impulsivity. These results are consistent with a large body of data linking reduced serotonin function and aggressive behavior and impulsivity.

Adult↗

PubMed2003

Effects of methylphenidate on impulsive choice in adult humans.

RATIONALE: Several studies with nonhumans and humans have shown that stimulants decrease impulsive choices on delay-to-reinforcement (self-control) procedures. Little is known, however, about the effects of the stimulant methylphenidate on choice for delayed reinforcers in humans. OBJECTIVES: The present study was designed to investigate the effects of acute methylphenidate administrations on impulsive responding in adult humans on a delay-to-reinforcement task. METHODS: Eleven adult males with a history of criminal behavior but no history of attention-deficit hyperactivity disorder (ADHD) participated. Impulsive responding was measured using an adjusting-delay procedure in which subjects were presented with repeated choices between a small amount of money delivered after a short delay and a larger amount of money delivered after a delay that adjusted as a function of previous choices. Subjects were exposed to four experimental sessions each day of participation and 60 min prior to the first daily session received placebo or 0.15, 0.30, or 0.60 mg/kg methylphenidate. Stable choice patterns were re-established between each methylphenidate dose. RESULTS: Individuals differed in their sensitivity to methylphenidate, but in over half of the subjects methylphenidate decreased impulsive (i.e., increased the number of self-control choices) and increased the delay to the large reinforcer. The largest increases in self-control choices tended to occur at the 0.30-mg/kg and 0.60-mg/kg doses, and the effects often persisted across multiple daily sessions. In six subjects, under at least one methylphenidate dose, the number of impulsive choices decreased to zero. CONCLUSIONS: Acute methylphenidate administrations tended to decrease the number of impulsive choices in adult humans on an adjusting-delay procedure, although there were substantial individual differences in the sensitivity of choice to methylphenidate. In no case, however, did methylphenidate increase impulsive choices. These results are consistent with several recent laboratory studies with nonhumans and humans showing that stimulants increase preference for large, delayed reinforcers.

Adolescent↗

PubMed2006

High-dose MDMA does not result in long-term changes in impulsivity in the rat.

RATIONALE: Evidence suggests that recreational users of (+/-)3,4-methylenedioxymethamphetamine HCl (MDMA, "ecstasy") have cognitive and behavioral deficits and show increased impulsivity consistent with 5-hydroxytryptamine (5-HT) neurotoxicity. MDMA effects on impulsivity in users are difficult to establish being confounded by polydrug use and individual predisposition to impulsivity or behavioral inhibition. OBJECTIVE: We previously observed a long-term anxiolytic effect of a neurotoxic dose of MDMA on elevated plus maze behavior in Dark Agouti (DA) rats while other strains were reported to show anxiogenesis. We have now examined whether MDMA influences impulsivity producing disinhibited behavior interpretable as anxiolysis. METHODS: Impulsivity was measured using an operant visuospatial discrimination procedure. Male DA rats (n = 24) were trained to lever press for food reward in response to a light-stimulus and subsequently required to withhold responding. Correct responses, premature responses, and response latencies were used as measures of accuracy and impulsivity. Trained rats were administered MDMA (5 mg/kg, i.p. at 3-h intervals to a total of three injections). Performance was measured at 3 h and 7, 27, 49, and 80 days posttreatment. RESULTS: There was a short-term effect of MDMA on the percentage of correct responses at 3 h and day 1 with recovery to control levels by days 7-8 and no significant long-term changes up to day 80. There was no effect of MDMA on premature responses on any of the days measured. MDMA reduced cortical 5-HT content (MDMA 363 +/- 14 ng/g and control 440 +/- 10 ng/g tissue). CONCLUSION: These results suggest that impulsivity may not be directly altered by MDMA despite serotonergic neurotoxicity.

Adrenergic Uptake Inhibitors↗

PubMed2000

Fenfluramine effects on impulsivity in a sample of adults with and without history of conduct disorder.

RATIONALE: The role of serotonin in impulsivity was examined by administering the serotonin-releasing drug, d,l-fenfluramine, and measuring effects on impulsive responding of male subjects with and without a history of conduct disorder (CD) under controlled laboratory conditions. METHODS: Five adult male subjects with a history of CD and five matched controls were recruited into a study to determine the acute effects of d,l-fenfluramine on a laboratory measure of impulsive behavior. This laboratory measure, based upon delay of gratification, presented subjects with choices between a small reward after a short delay and a larger reward after a longer delay. Impulsive behavior was indicated by frequent choices for the smaller reward. RESULTS: Acute oral doses of d,l-fenfluramine (0.21, 0.42, and 0.85 mg/kg) produced decreases in the number of impulsive choices in all subjects with a history of CD, but had no effect on the control subjects. CONCLUSIONS: This data suggests that a deficit in serotonin and/or dopamine may play a role in impulsivity in CD subjects, and drugs which act to reduce this biological deficit can reduce impulsiveness.

Adult↗

PubMed1996

Objects, decision considerations and self-image in men's and women's impulse purchases.

Current theories in economics, marketing, and psychology fail to explain underlying reasons for impulse buying and, crucially, why certain goods (e.g., clothes) are bought impulsively more than others (e.g., basic kitchen equipment). We propose and examine a social psychological model, which predicts that people impulse buy to acquire material symbols of personal and social identity. We predict that consumers will differ systematically in the goods they buy on impulse, and in their reasons for doing so, depending on their attitudes towards shopping, and also along important social categories, such as gender. Specifically, our theoretical model-drawing on a social constructionist model of material possessions (e.g., Dittmar, 1992) and symbolic self-completion theory (e.g. Wicklund and Gollwitzer, 1982)-leads to three sets of hypotheses: (i) some consumer durables are more likely to be bought on impulse than others, and there may be gender differences in object choices, (ii) differences will emerge in the buying considerations (e.g., functional, emotional, symbolic) that are used for impulse and planned buying, and (iii) magnitude of self-discrepancies will predict relative impulse buying frequency and the buying considerations used, if the individual uses consumption as a self-completion strategy. These predictions were expected to hold particularly strongly for individuals high in compulsive shopping tendencies. We test our model in a questionnaire study with a sample of British consumers (n = 61). The results lend support to all three sets of hypotheses. The implications of these findings are discussed with respect to economic and consumer theory, and the treatment offered to the increasing number of 'addicted' shoppers.

Adult↗

PubMed2005

Differences in impulsivity and sensation seeking between early- and late-onset alcoholics.

The personality traits of impulsivity and sensation seeking have been proposed as important features of early-onset alcoholism. Early-onset (EOA, n=62) and late-onset (LOA, n=68 ) alcoholic inpatients were compared as to the severity of their substance use and related problems, and self-report scales measuring impulsivity (Barratt Impulsiveness Scale, version 11), sensation seeking (Sensation Seeking Scale), and aggressiveness (Buss Durkee Hostility Inventory). The symptom severity of the EOAs' alcohol-use disorder and related problems was higher than that of the LOAs. Furthermore, the EOAs had higher levels of impulsivity, sensation seeking, and aggression relative to the LOAs. The differences in impulsivity remained after an analysis controlling for the effect of aggressiveness. Finally, cigarette smoking was positively correlated with impulsiveness across alcoholic subgroups. Active screening for impulsive traits in treatment-seeking alcohol-abusing populations is recommended to improve treatment planning and prevent early drop-out.

Adult↗

PubMed2005

Effects of temporal clumping and payoff accumulation on impulsiveness and cooperation.

Animals show impulsiveness when they prefer a smaller more immediate option, even though a larger more delayed option produces a higher intake rate. This impulsive behavior has implications for several behavioral problems including social cooperation. This paper presents two experiments using captive blue jays (Cyanocitta cristata) that consider the effects of payoff accumulation and temporal clumping on impulsiveness and cooperation. Payoff accumulation refers to a situation where the benefits gained from each choice trial accumulate from one trial to the next, and only become available to the animal after it has completed a fixed number of trials. We hypothesized that this would reduce impulsiveness because it removes the advantage of quickly realizing food gains. Clumping refers to situation in which the animal experiences several choice trials in quick succession followed by a long pause before the next clump. We hypothesized that if payoffs accumulated over a clump of trials this would enhance the effect of accumulation. We tested the effects of accumulation and clumping on impulsiveness in a self-control situation. We found a significant interaction between clumping and accumulation. Payoff accumulation reduced impulsiveness, but only when trials were clumped. Post hoc analyses suggest that clumping alone increases impulsiveness. A second experiment applied these results to cooperation. This experiment reveals an interaction between payoff accumulation and trial's position within the clump. Jays were more likely to cooperate on the first trial of a clump, but the likelihood of cooperation dropped after the first trial. However, this drop was larger when payoffs did not accumulate. This observation suggests that the difference between accumulated and un-accumulated treatments that we reported previously may be largely due to differences in how animals behave in the first trial of a clump.

Animals↗

PubMed2006

Tryptophan depletion affects heart rate variability and impulsivity in remitted depressed patients with a history of suicidal ideation.

BACKGROUND: Depression is a major risk factor for cardiovascular disease. An important risk factor for cardiovascular disease, low heart rate variability, often has been found in depressed patients and has been associated with impulsivity. The present study investigated whether experimental lowering of serotonin would decrease heart rate variability and increase impulsivity in remitted depressed patients, in particular in those patients with disturbed impulse control. METHODS: Nineteen patients in remission from depression received high-dose and low-dose acute tryptophan depletion in a randomized, counterbalanced, double-blind crossover design. Heart rate variability and impulsivity were assessed during each acute tryptophan depletion session and during a baseline session. Suicidal ideation during past depression was used as an index for individual differences in impulse control. RESULTS: High-dose acute tryptophan depletion led to a larger increase in depressive symptoms than did low-dose acute tryptophan depletion. High-dose acute tryptophan depletion decreased heart rate variability and increased impulsivity and anxiety, but only in patients with a history of suicidal ideation. Symptom effects of high-dose acute tryptophan depletion correlated with low heart rate variability at baseline. CONCLUSIONS: Depressed patients who have problems with controlling impulsivity might be more at risk for developing cardiovascular disease, possibly related to increased vulnerability to impaired 5-hydroxytryptamine function.

Adult↗

PubMedDate not supplied

Impulsive disorders in Japanese adult patients with obsessive-compulsive disorder.

In this study, we sought to characterize obsessive-compulsive disorder (OCD) patients with impulsive features, and to determine whether they constitute a distinct subtype of OCD. Therefore we systematically assessed impulse control disorders and other impulsive conditions categorized as obsessive-compulsive spectrum disorders (OCSDs) in 153 Japanese adult patients with OCD. Forty-five subjects (29%) had concurrent impulsive disorders, and they were differentiated from other OCD patients on a range of demographic features (e.g., younger age at onset), and clinical features (e.g., pervasive and severe psychopathology, and poor treatment outcome). However, on logistic regression, none of these variables predicted comorbid impulsivity. The findings appear to support the argument that OCD patients with impulsive features constitute a subtype of OCD. However, further research is necessary to determine whether impulsivity should be conceptualized as lying on a spectrum with compulsivity or as a dimension that is orthogonal to compulsivity.

Adult↗