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Measurement of impulsivity: construct coherence, longitudinal stability, and relationship with externalizing problems in middle childhood and adolescence.

This study focused on the assessment of impulsivity in nonreferred school-aged children. Children had been participants since infancy in the Bloomington Longitudinal Study. Individual differences in impulsivity were assessed in the laboratory when children were 6 (44 boys, 36 girls) and 8 (50 boys, 39 girls) years of age. Impulsivity constructs derived from these assessments were related to parent and teacher ratings of externalizing problems across the school-age period (ages 7-10) and to parent and self-ratings of these outcomes across adolescence (ages 14-17). Consistent with prior research, individual measures of impulsivity factor-analyzed into subdimensions reflecting children's executive control capabilities, delay of gratification, and ability or willingness to sustain attention and compliance during work tasks. Children's performance on the main interactive task index, inhibitory control, showed a signficant level of stability between ages 6 and 8. During the school-age years, children who performed impulsively on the laboratory measures were perceived by mothers and by teachers as more impulsive, inattentive, and overactive than others, affirming the external validity of the impulsivity constructs. Finally, impulsive behavior in the laboratory at ages 6 and 8 predicted maternal and self-ratings of externalizing problem behavior across adolescence, supporting the long-term predictive value of the laboratory-derived impulsivity measures.

Adolescent↗

Measuring impulsivity and examining its relationship to delinquency.

A multimethod, multisource assessment of impulsivity was conducted in a sample of more than 400 boys who were members of a longitudinal study of the development of antisocial behavior. Exploratory and confirmatory factor analysis of the 11 different impulsivity measures revealed two impulsivity factors: Cognitive and Behavioral. Cognitive and behavioral impulsivity had similar correlations with socioeconomic status. Cognitive impulsivity was more strongly related to IQ than was behavioral impulsivity. Behavioral impulsivity was more strongly related to delinquency at ages 10 and 12-13 than was cognitive impulsivity. Consistent with theoretical prediction, our results also indicate that behavioral impulsivity was especially related to serious delinquency that is stable over time.

Adolescent↗

Impulsivity and speed-accuracy tradeoffs in information processing.

Despite its theoretical importance for such areas of research as reflection-impulsivity (Kagan, 1966), there is little evidence to support the assumption that individual differences in the personality trait of impulsivity are associated with differences in the willingness to sacrifice accuracy for speed of information processing. The present studies explored this association further. In Experiment 1, high, medium, and low impulsives (identified by self-report) performed a visual-comparison task under conditions differing in the monetary payoff for speed relative to accuracy. High impulsives were consistently faster and less accurate than other subjects. However, an analysis based on Sternberg's (1969) additive-factor method indicated that high impulsives performed at least one stage of information processing as slowly and accurately as other subjects. In Experiment 2, it was found that high impulsives were actually more accurate than low impulsives when all subjects were required to process information extremely rapidly. Experiment 3 identified the response execution stage as one that high impulsives carry out just as slowly and accurately as other individuals. The data from these experiments pose problems for a simple speed-accuracy tradeoff model of impulsive cognitive functioning.

Adult↗

Impulsiveness as a factor in sexual offending by people with mild intellectual disability.

BACKGROUND: It has been suggested that sexual offending by people with intellectual disability (ID) results from a pattern of impulsive behaviour that is consistent with psychosocial disadvantage, rather than sexual deviancy. This study aimed to explore this hypothesis by assessing levels of impulsiveness in sexual offenders, non-sexual offenders and non-offenders with mild ID. METHOD: Impulsiveness was assessed using a modified version of the Barratt Impulsiveness Scale (11th edition). Total impulsivity scores were compared between sexual offenders, non-sexual offenders and non-offenders, all with mild ID. RESULTS: There was a significant difference in the levels of impulsiveness between sexual offenders and non-sexual offenders with ID (t=2.83, P<0.01). The sexual offenders were less impulsive than non-sexual offenders. CONCLUSIONS: This study did not support the hypothesis that sexual offending by people with ID is better explained by impulsive behaviour rather than sexual deviancy. It supports recent findings that among the general population, sexual offenders are less impulsive than controls and violent offenders.

Adult↗

Behavioural aspects of impulsivity in alcoholics with and without a cluster-B personality disorder.

AIMS: Studies have shown that alcoholics with a cluster-B personality disorder (cluster-B PD) are characterized by high levels of impulsivity. However, impulsivity has mainly been studied as a broad concept without its different aspects being considered. The present study compared abstinent alcoholic inpatients without any personality disorder (PD) and abstinent alcoholics with cluster-B PD on different aspects of impulsivity, i.e. self-reported impulsivity and neuropsychological indicators such as behavioural control and delay of gratification. METHODS: Forty alcohol-dependent inpatients without PD and 22 alcohol-dependent inpatients with a cluster-B PD were compared on two self-report impulsivity questionnaires (Barratt impulsiveness scale; sensation-seeking scales) and three behavioural impulsivity tasks [Go/No-Go task; delay discounting task (DDT); Stroop colour word test]. Tests were administered after stable abstinence of at least 3 weeks. RESULTS: Self-report measures of impulsivity were higher in cluster-B alcoholics than in alcoholics without PD. Behavioural tasks revealed a more differentiated pattern of impairments. On the Go/No-Go task, cluster-B alcoholics were impaired in inhibitory control but not in reaction time compared with alcoholics without PD. In contrast, no significant differences on the DDT and the Stroop were observed. CONCLUSION: Alcohol-dependent patients with and without a cluster-B PD differ in terms of behavioural inhibition but not in terms of activation or the ability to delay gratification. This finding may partly account for their impulsive and (self-) destructive behaviours. Treatment planning should pay specific attention to these impairments in behavioural control.

Adult↗

Impulsiveness without discounting: the ecological rationality hypothesis.

Observed animal impulsiveness challenges ideas from foraging theory about the fitness value of food rewards, and may play a role in important behavioural phenomena such as cooperation and addiction. Behavioural ecologists usually invoke temporal discounting to explain the evolution of animal impulsiveness. According to the discounting hypothesis, delay reduces the fitness value of the delayed food. We develop an alternative model for the evolution of impulsiveness that does not require discounting. We show that impulsive or short-sighted rules can maximize long-term rates of food intake. The advantages of impulsive rules come from two sources. First, naturally occurring choices have a foreground-background structure that reduces the long-term cost of impulsiveness. Second, impulsive rules have a discrimination advantage because they tend to compare smaller quantities. Discounting contributes little to this result. Although we find that impulsive rules are optimal in a simple foreground-background choice situation in the absence of discounting, in contrast we do not find comparable impulsiveness in binary choice situations even when there is strong discounting.

Animals↗

Impulsivity: a link between bipolar disorder and substance abuse.

BACKGROUND: Substance abuse is present in most patients with bipolar disorder and associated with poor treatment outcome and increased risk of suicide. Increased impulsivity may be a link between bipolar disorder and substance abuse. METHODS: First, we compared impulsivity as a stable trait (Barratt Impulsiveness Scale, BIS) and as state-dependent behavioral laboratory performance (Immediate Memory-Delayed Memory task, derived from the Continuous Performance Task) in interepisode bipolar and non-bipolar subjects with and without substance abuse. Secondly, we compared impulsivity in interepisode and manic bipolar subjects with and without substance abuse. RESULTS: The BIS scores were increased in interepisode bipolar disorder and in subjects with histories of substance abuse, and were increased further in interepisode bipolar subjects with substance abuse. Performance impulsivity was increased in subjects with substance abuse, regardless of whether they had bipolar disorder. Among subjects with bipolar disorder, after correction for age, BIS scores were increased in those with substance abuse. Performance impulsivity was increased in manic compared with interepisode subjects, regardless of substance abuse history, and was increased in interepisode subjects with substance abuse similarly to manic subjects without substance abuse. These differences could not be accounted for by age, gender, or course of illness. CONCLUSIONS: Trait impulsivity is increased additively in bipolar disorder and substance abuse. Performance impulsivity is increased in interepisode bipolar disorder only if a history of substance abuse is present. This increased predisposition to impulsivity when not manic may contribute to the decrement in treatment outcome and compliance, and increased risk for suicide and aggression, in bipolar disorder with substance abuse.

Adult↗

P300 event-related potential amplitude and impulsivity in cocaine-dependent subjects.

Previous studies report reduced amplitude of the P300 event-related potential in cocaine-dependent individuals. Cocaine dependence is also associated with increased impulsivity, possibly due to deficits in cognitive function that are associated with reduced P300 amplitude. In the current study, the relationship between cocaine dependence, impulsivity, and P300 amplitude were examined. An auditory oddball event-related potential task along with self-report (Barratt Impulsiveness Scale version 11) and behavioral laboratory (Immediate and Delayed Memory Task) measures of impulsivity were assessed in healthy controls (n = 14) and subjects who met DSM-IV criteria for current cocaine dependence (n = 17). P300 amplitude was reduced and self-reported and behavioral laboratory impulsivity scores were elevated among the cocaine-dependent group compared to controls. There was a positive correlation between the questionnaire and behavioral laboratory measures of impulsivity, and a negative correlation between impulsivity measures and P300 amplitude. The correlation between self-reported impulsivity scores and P300 amplitude remained after taking into account the number of childhood conduct disorder symptoms. This study supports the hypothesis that the basic neurophysiology responsible for the P300 amplitude in cocaine-dependent individuals is associated with impulsivity independent of a history of childhood conduct disorder symptoms.

Adult↗

Impulse control disorders in adult psychiatric inpatients.

OBJECTIVE: The authors' goal was to examine the prevalence of impulse control disorders in psychiatric inpatients. METHOD: They used the Minnesota Impulsive Disorders Interview, a semistructured clinical interview assessing pathological gambling, trichotillomania, kleptomania, pyromania, intermittent explosive disorder, compulsive buying, and compulsive sexual behavior, to screen 204 consecutively admitted psychiatric inpatients. One hundred twelve of the inpatients were women (54.9%), and the mean age of the 204 inpatients was 40.5 years (SD=13.2, range=18-83). Patients whose screen was positive for an impulse control disorder were evaluated with structured clinical interviews. RESULTS: Sixty-three patients (30.9%) were diagnosed with at least one current impulse control disorder. The most common impulse control disorders were compulsive buying (N=19 [9.3%]), kleptomania (N=16 [7.8%]), and pathological gambling (N=14 [6.9%]). Patients with and without co-occurring impulse control disorders did not differ significantly from each other on demographic measures or number or type of psychiatric diagnoses other than impulse control disorders. CONCLUSIONS: Impulse control disorders appear common among psychiatric inpatients. Additional, larger studies are needed to examine the prevalence of impulse control disorders in the general population and specific psychiatric groups.

Adolescent↗

Psychological, neuroimaging, and biochemical studies on functional association between impulsive behavior and the 5-HT2A receptor gene polymorphism in humans.

It has been suggested that impulsive behavior is caused by dysfunctional serotonergic 5-HT neurotransmission in the central nervous system (CNS). Brain neuroimaging studies have shown that behavioral inhibition is linked to the activation of cortex sites such as the ventral frontal cortex. Positron emission tomography (PET) imaging with [(18)F]altanserin to characterize 5-HT(2A) receptor binding revealed a reduction in 5-HT(2A) binding in the ventral frontal cortex in women who had recovered from impulsive diseases. These clinical, neuroimaging, and pharmacological studies appear to support the hypothesis that functional alteration of neurotransmission due to genetic polymorphisms of the 5-HT receptors may be involved in impulsive behavior modulation. Following evaluation by a self-reporting measure, it was proposed that a polymorphism in the promoter of the 5-HT(2A) receptor gene is the underlying cause of impulsive behavior; however, this hypothesis is not convincing. We examined whether the polymorphism in the 5-HT(2A) receptor gene promoter is involved in impulsive aggression by evaluating a behavioral task (Go/No-go task) in normal volunteers. The polymorphism of the 5-HT(2A) receptor gene promoter in lymphocytes from 71 volunteers was analyzed by using PCR. Impulsivity was defined as the number of commission errors (responding when one should not) recorded during a Go/No-go task; a larger number of commission errors indicate greater difficulty in inhibiting impulsive behavior. The subjects of the A-1438A allele group for the 5-HT(2A) receptor gene made more commission errors under the punishment-reward (PR)condition in a Go/No-go task than those in the G-1438G group. In the present review, we discuss and suggest the possible involvement of the A-1438A polymorphism of the 5HT2A receptor gene promoter in impulsive behavior. This hypothesis was evaluated by using a behavioral task measure that could directly reveal impulsive behavioral traits in humans.

Brain↗

Stressful life events and impulsiveness in failed suicide.

The relationship of recent stressful life events with impulsiveness in triggering suicide attempts and how impulsiveness changes from one suicide attempt to another is unclear. This study used structured-interview tools and standardized measurements to examine the relationship between life stress and impulsiveness in a sample of patients who required hospitalization for a medically serious suicide attempt. After controlling for potentially confounding variables, the number of disrupted interpersonal relationships in the preceding year was a significant predictor of the impulsiveness of the suicide attempt, with three or more losses (but not other life stresses) associated with less impulsive attempts (T = 2.4, p = .02). Female gender (T = -1.98, p = .05) and lifetime DMS-III-R diagnoses (T = -2.45, p = .02) were significantly associated with more impulsive attempts. In 55 patients with at least two suicide attempts, impulsiveness, lethal intent, and communication of intent were significantly greater for the present compared to the prior attempt (p = 0.000). Certain stressful life events, gender, and total lifetime DSM-III-R diagnoses are associated with impulsiveness of failed suicide attempts; yet, impulsiveness is not necessarily consistent from one suicide attempt to another. This evidence supports and amplifies a stress-diathesis model of suicide behavior. Accordingly, efforts to increase personal resilience in individuals who have "failed suicide" may be more effective at preventing suicide morbidity than simple stress-reduction measures alone.

Female↗

Characteristics of impulsive suicide attempts and attempters.

Suicide attempts often are impulsive, yet little is known about the characteristics of impulsive suicide. We examined impulsive suicide attempts within a population-based, case-control study of nearly lethal suicide attempts among people 13-34 years of age. Attempts were considered impulsive if the respondent reported spending less than 5 minutes between the decision to attempt suicide and the actual attempt. Among the 153 case-subjects, 24% attempted impulsively. Impulsive attempts were more likely among those who had been in a physical fight and less likely among those who were depressed. Relative to control subjects, male sex, fighting, and hopelessness distinguished impulsive cases but depression did not. Our findings suggest that inadequate control of aggressive impulses might be a greater indicator of risk for impulsive suicide attempts than depression.

Adolescent↗

Impulsivity in pathological gambling: the antisocial impulsivist.

The construct of impulsivity has to date remained relatively unexplored in the pathological gambling literature. This is in spite of recent claims suggesting that impulsivity may be an important feature characterizing a subgroup of pathological gamblers who are claimed to suffer from a Multi-Impulse Personality Disorder. The present study examined the potential role of impulsivity using the Eysenck Impulsivity Scale among 115 pathological gamblers. Results indicate that heightened impulsivity is associated with the degree of severity of psychological and behavioural change in pathological gamblers. However, the findings also indicate that impulsivity closely mirrors components contained in Eysenck Personality Questionnaire Psychoticism Scale, the California Personality Inventory Socialization Scale and DSM-III Antisocial Personality Disorder. This is manifest both in terms of high intercorrelations between the measures of psychopathy and impulsivity and in their predictive relationship to the level of psychological distress suggesting a uniform impulsivity/psychopathy construct. Thus, the research supports a model of pathological gambling in which the severity of associated behavioural and psychological disturbance is mediated by a impulsivity/ psychopathy construct.

Adolescent↗

The nerve impulse in the axon--a new theory.

The Classical Theory of function in the nervous system postulates that the nerve impulse is the result of a sequential reversal of the membrane potential due to an increased permeability of the membrane, first to sodium ions, then to potassium ions. The new theory presents a bio-physical model which depicts the nerve impulse as an event involving the motions of electrons and waves, and their interactions with sodium and potassium atoms and ions. The velocity of the nerve impulse (the most important parameter of nerve function) is determined by the product of two constants: c = the speed of light, which is a constant for all nerves; k = a constant for each nerve and is believed to be a specific property of nerve matter related in some way to the atomic process. The theory proposes that the nerve impulse in the axon is 'dualistic' in nature (particles and waves play equally significant roles). The dualistic nature accounts for the three most fundamental characteristics of conduction of the nerve impulse: periodicity (conduction of a nerve impulse over long distances with constant velocity and form); non-summing (two nerve impulses cannot be in the same place at the same time); 'quantum nature' of each nerve impulse - i.e., the unit message of the nerve impulse is an indivisible unit.

Axons↗

Conduction of trans of impulses in uniform myelinated fibers: computed dependence on stimulus frequency.

The conduction of trains of action potentials in myelinated fibers was studied using computer simulations based on a modification of the Hodgkin-Huxley equations. Stimulation at short but regular interstimulus intervals caused some stimuli to fail to elicit propagated action potentials. Propagated impulse trains observed close to the stimulation site, elicited by high frequency stimulus trains, took the form of "clusters" of impulses, e.g. doublets or triplets. When these impulse trains were observed at distances farther from the stimulation site, interspike intervals were more uniform. For interstimulus intervals of less than 10 ms, distant intervals between impulses were relatively insensitive to the temporal patterning of impulses at the initiation zone and tended toward regular intervals corresponding to the average interstimulus intervals for propagated stimuli. This tendency toward uniform intervals between impulses was also observed for lower average frequency stimulus trains with irregular interstimulus intervals. Moreover, for the first two stimuli in a train, there was a very tendency toward impulse entrainment. These results indicate that intervals between impulses along unbranched myelinated axons are not fixed, but vary according to the site along the conduction pathway where they are observed. The tendency toward entrainment, and regularization of intervals, may represent a factor limiting the frequency with which interval-coded impulses are initiated.

Action Potentials↗

Impulsivity as a confounding factor in certain animal tests of cognitive function.

Performance in cognitive tasks which require the subject to wait and/or to process a large amount of information can be disrupted by an increase in impulsive-like behaviour. Accordingly, a decrease in impulsive-like behaviour can improve performance in such tasks. Conversely, impulsive-like behaviour may improve performance in cognitive tasks where simple and fast responses and/or only little information processing is required. Thus, impulsivity constitutes a confounding factor in studies of cognitive function. Impulsive-like behaviour may be modified by serotonergic (5-HT) activity, with underactivity in 5-HT neurotransmission increasing impulsivity and vice versa. Drug- or lesion-induced alteration in 5-HT neurotransmission may, therefore, constitute suitable tools to investigate the role of impulsivity in animal tests of cognitive function. Benzodiazepines also increase impulsive-like behaviour, possibly by decreasing 5-HT neurotransmission. Hence, the effects of modulation of 5-HT systems and of the benzodiazepine-binding site on performance in animals tests of cognitive function will be discussed. It is predicted that the effects of manipulations of serotonergic activity or of benzodiazepine administration depend upon the nature of the response required, and that these effects may be mediated through changes in impulse control.

Animals↗

Impulsiveness and lack of inhibitory control in eating disorders.

UNLABELLED: Eating disorders are considered to lie on a spectrum of disorders with varying degrees of obsessive-compulsive and impulsive traits. Restrictive anorexia nervosa patients (AN-R) are thought to belong to the obsessive pole of the spectrum, and purging-anorexia (AN-P) and bulimia nervosa (BN) patients to the impulsive pole. In this study we have compared impulsive traits in three groups of eating disordered patients (total N=56) and a control group of 83 female students. Information about impulsive traits and lack of inhibitory control was gathered by means of standardized rating scales (Eysenck's Impulsiveness Scale, Barrett's Impulsiveness Scale, and Carver and White's BIS/BAS scale) and a behavioral measure of impulsiveness (stop-go task). On the questionnaires AN-R patients reported to be less impulsive than controls, AN-P and BN patients. In the stop-go task, we did not find significant differences between the different groups. Correlations between self-reported measures of impulsiveness and behavioral measures were not significant. IN CONCLUSION: Our results from the self-report measures are at odds with the behavioral measures certainly in the AN-R group. Perhaps the latter patients' distorted self-perception and/or self-description may explain this discrepancy.

Adolescent↗

The effects of altering mean pressure, pulse pressure and pulse frequency on the impulse activity in baroreceptor fibres from the aortic arch and right subclavian artery in the rabbit.

1. A method is described for perfusing an isolated preparation of the rabbit aortic arch with independently controlled mean pressure, pulse pressure and pulse frequency.2. Recordings made from single or few-fibre preparations from the aortic arch and right subclavian baroreceptor regions show that the number of impulses per second or per cycle in a single fibre is the same during pulsatile perfusion as during non-pulsatile perfusion if the pressure is above the threshold pressure to non-pulsatile perfusion during all phases of the pressure cycle.3. In multi-fibre recordings the total number of impulses is greater during pulsatile perfusion than during non-pulsatile perfusion due largely to recruitment of fibres during systole.4. The relationship between instantaneous impulse frequency and aortic arch pressure during one pressure cycle forms an elliptiform curve.5. Increasing the pulse pressure increases the ellipse and causes additional recruitment of other fibres during systole, thus augmenting the total impulse activity.6. Increasing the pulse frequency reduces the number of impulses per cycle for single fibres but produces a small increase in the total impulse frequency in one second period due to recruitment.7. Increasing the rate of change of pressure by increasing the pulse pressure or pulse frequency produced a small reduction or no change of the threshold pressure. Similarly the ;cut off' pressure was elevated in some fibres.8. At low initial mean pressures, an increment of pressure, at constant pulse pressure and pulse frequency, increases the total impulse activity by increasing the frequency of impulses in single fibres already active during systole and diastole and by additional recruitment of other fibres. At higher mean pressures there is little increase in impulse activity as the maximum frequency of fibres is attained or superseded and there is little recruitment.

Action Potentials↗