Enhancing tolerance to delayed reinforcers: the role of intervening activities.
(25/908)
Three participants with moderate to profound mental retardation were exposed to choices between an immediate small amount and a delayed larger amount of a preferred reinforcer. All participants initially showed a relatively high preference for the smaller reinforcer, suggesting impulsive choice making. However this preference reversed, suggesting self-control, when the larger reinforcer was available immediately and, over time, its delay was gradually increased. Results highlight the potential utility of incorporating concurrent activities into self-control training paradigms. (+info)
Prefrontal cortical-ventral striatal interactions involved in affective modulation of attentional performance: implications for corticostriatal circuit function.
(26/908)
Anatomically segregated systems linking the frontal cortex and the striatum are involved in various aspects of cognitive, affective, and motor processing. In this study, we examined the effects of combined unilateral lesions of the medial prefrontal cortex (mPFC) and the core subregion of the nucleus accumbens (AcbC) in opposite hemispheres (disconnection) on a continuous performance, visual attention test [five-choice serial reaction-time task (5CSRTT)]. The disconnection lesion produced a set of specific changes in performance of the 5CSRTT, resembling changes that followed bilateral AcbC lesions while, in addition, comprising a subset of the behavioral changes after bilateral mPFC lesions previously reported using the same task. Specifically, both mPFC/AcbC disconnection and bilateral AcbC lesions markedly affected aspects of response control related to affective feedback, as indexed by perseverative responding in the 5CSRTT. These effects were comparable, although not identical, to those in animals with either bilateral AcbC or mPFC/AcbC disconnection lesions. The mPFC/AcbC disconnection resulted in a behavioral profile largely distinct from that produced by disconnection of a similar circuit described previously, between the mPFC and the dorsomedial striatum, which were shown to form a functional network underlying aspects of visual attention and attention to action. This distinction provides an insight into the functional specialization of corticostriatal circuits in similar behavioral contexts. (+info)
Delay discounting by pathological gamblers.
(27/908)
Discounting of delayed rewards by pathological gamblers was compared to discounting of delayed rewards by matched control nongambling participants. All participants completed a hypothetical choice task in which they made repeated choices between dollars 1,000 available after a delay and an equal or lesser amount of money available immediately. The delay to the large amount of money was varied from 1 week to 10 years across conditions. Indifference points between immediate money and delayed money were identified at each delay condition by varying the amount of immediate money across choice trials. For the majority of participants, indifference points decreased monotonically across delays. Overall, gamblers discounted the delayed rewards more steeply than did control participants. (+info)
Impulsivity, time perception, emotion and reinforcement sensitivity in patients with orbitofrontal cortex lesions.
(28/908)
Damage to the orbitofrontal cortex (OFC) in humans has been associated with disinhibited or socially inappropriate behaviour and emotional changes. Some of the changes may be related to difficulty in responding correctly to rewards and punishers, in that these patients have difficulty in learning to correct their choice of a visual stimulus when it is no longer associated with reward. We extend this fundamental approach by investigating the relationship between frontal dysfunction and impulsive behaviour, the behavioural, emotional and personality changes seen in patients with prefrontal cortex damage, and thus in addition illuminate the cognitive and biological processes that are impaired in impulsive people. OFC patients (n = 23) performed more impulsively on both self-report and cognitive/behavioural tests of impulsivity, reported more inappropriate 'frontal' behaviours, and performed worse on a stimulus-reinforcement association reversal task, than non-OFC prefrontal cortex lesion control (n = 20) and normal control (n = 39) participants. Further, OFC patients experienced more subjective anger than non-OFC and normal participants, and less subjective happiness than normals; and had a faster subjective sense of time (overestimated and underproduced time intervals) than normal controls, while non-OFC patients did not differ from normals. Finally, both OFC and non-OFC patients were less open to experience than normal participants. There were no differences between OFC patients, non-OFC lesion patients and normal controls on all other personality traits, most notably extraversion. In a spatial working memory task, the non-OFC group, most of whom had dorsolateral prefrontal cortex lesions, were impaired in that they repeatedly returned to previously chosen empty locations ('within errors'), whereas OFC patients were not impaired on this measure. Thus there is a dissociation between the effects of OFC damage which does not affect this measure of spatial working memory but does affect impulsive and inappropriate behaviour, reversal, personality, time perception and emotion; and dorsolateral prefrontal cortex damage which does affect this measure of spatial working memory, but not impulsive and inappropriate behaviour, reversal, personality, time perception and emotion. The effects of OFC damage on impulsive and related behaviours described here have implications for understanding impulsive behaviour. (+info)
The relations of effortful control and impulsivity to children's resiliency and adjustment.
(29/908)
The unique relations of effortful control and impulsivity to resiliency and adjustment were examined when children were 4.5 to 8 years old, and 2 years later. Parents and teachers reported on all constructs and children's attentional persistence was observed. In concurrent structural equation models, effortful control and impulsivity uniquely and directly predicted resiliency and externalizing problems and indirectly predicted internalizing problems (through resiliency). Teacher-reported anger moderated the relations of effortful control and impulsivity to externalizing problems. In the longitudinal model, all relations held at T2 except for the path from impulsivity to externalizing problems. Evidence of bidirectional effects also was obtained. The results indicate that effortful control and impulsivity are distinct constructs with some unique prediction of resiliency and adjustment. (+info)
Fractionating impulsivity: contrasting effects of central 5-HT depletion on different measures of impulsive behavior.
(30/908)
Reducing levels of 5-HT in the central nervous system has been associated with increases in impulsive behavior. However, the impulsivity construct describes a wide range of behaviors, including the inability to withhold a response, intolerance to delay of reward and perseveration of a nonrewarded response. Although these behaviors are generally studied using instrumental paradigms, impulsivity may also be reflected in simple Pavlovian tasks such as autoshaping and conditioned activity. This experiment aimed to characterize further the effects of central 5-HT depletion and to investigate whether different behavioral measures of impulsivity are inter-related, thus validating the construct. Rats received intracerebroventricular (ICV) infusions of vehicle (n=10) or the serotonergic neurotoxin 5,7-dihydroxytryptamine (n=12) which depleted forebrain 5-HT levels by about 90%. Lesioned animals showed significant increases in the speed and number of responses made in autoshaping, increased premature responding on a simple visual attentional task, enhanced expression of locomotor activity conditioned to food presentation, yet no change in impulsive choice was observed, as measured by a delay-discounting paradigm. Significant positive correlations were found between responses made in autoshaping and the level of conditioned activity, indicating a possible common basis for these behaviors, yet no correlations were found between other behavioral measures. These data strengthen and extend the hypothesis that 5-HT depletion increases certain types of impulsive responding. However, not all measures of impulsivity appear to be uniformly affected by 5-HT depletion, or correlate with each other, supporting the suggestion that impulsivity is not a unitary construct. (+info)
Do alcohol expectancies and peer delinquency/substance use mediate the relationship between impulsivity and drinking behaviour in adolescence?
(31/908)
AIMS: To investigate (1). whether aggressive and delinquent behaviour problems predict subsequent adolescent drinking behaviour; and (2). to what extent this association is mediated by alcohol expectancies and/or peer delinquency/substance use. METHODS: 147 adolescents (approximately 15 years old) were interviewed with regard to their drinking behaviour. In addition, several self-rating questionnaires were given to gather information regarding the peers of these children. RESULTS: As proposed by the Acquired Preparedness Model (APM), we found that behavioural problems were related to quantity and frequency of alcohol consumed, and that this relationship was mediated by alcohol expectancies. Regarding peer relations, we found positive correlations between drinking behaviour and peer delinquency/substance use, aggression/delinquency and alcohol expectancies. Furthermore, the association between behavioural problems and drinking decreased dramatically if peer delinquency/substance use was accounted for. A hierarchical regression analysis revealed that both alcohol expectancies and peer delinquency/substance use predicted alcohol consumption of adolescents at the 1-year follow-up above and beyond the effects of age, sex, family history of alcoholism and aggression/delinquency of respondents. CONCLUSIONS: Alcohol expectancies and peer delinquency/substance use are both crucial to the amount and frequency of adolescent alcohol use. They should be considered in designing prevention and intervention strategies in this age group. (+info)
An association between a functional polymorphism in the monoamine oxidase a gene promoter, impulsive traits and early abuse experiences.
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Monoamine oxidase A (MAOA) activity is altered in mood disorders and lower activity associated with aggressive behavior. The gene has a functional polymorphism with a variable number tandem repeat (VNTR) in the upstream regulatory region (MAOA-uVNTR). In this study, we examined possible associations between the MAOA-uVNTR polymorphism and mood disorders, suicidal behavior, aggression/impulsivity, and effects of reported childhood abuse. In total, 663 unrelated subjects with a psychiatric disorder and 104 healthy volunteers were genotyped for the 30 base pair functional VNTR. A novel repeat variation was identified. No statistically significant associations were found between this functional MAOA-uVNTR polymorphism and mood disorders or suicide attempts. However, the lower expression allele was associated with a history of abuse before 15 years of age in male subjects and with higher impulsivity in males but not females. Our results suggest that the lower expression of the MAOA-uVNTR polymorphism is related to a history of early abuse and may sensitize males, but not females, to the effects of early abuse experiences on impulsive traits in adulthood. The polymorphism may be a marker for impulsivity that in turn may contribute to the risk for abuse. This trait could then be further aggravated by abuse. (+info)