Delay or probability discounting in a model of impulsive behavior: effect of alcohol.
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Little is known about the acute effects of drugs of abuse on impulsivity and self-control. In this study, impulsivity was assessed in humans using a computer task that measured delay and probability discounting. Discounting describes how much the value of a reward (or punisher) is decreased when its occurrence is either delayed or uncertain. Twenty-four healthy adult volunteers ingested a moderate dose of ethanol (0.5 or 0.8 g/kg ethanol: n = 12 at each dose) or placebo before completing the discounting task. In the task the participants were given a series of choices between a small, immediate, certain amount of money and $10 that was either delayed (0, 2, 30, 180, or 365 days) or probabilistic (i.e., certainty of receipt was 1.0, .9, .75, .5, or .25). The point at which each individual was indifferent between the smaller immediate or certain reward and the $10 delayed or probabilistic reward was identified using an adjusting-amount procedure. The results indicated that (a) delay and probability discounting were well described by a hyperbolic function; (b) delay and probability discounting were positively correlated within subjects; (c) delay and probability discounting were moderately correlated with personality measures of impulsivity; and (d) alcohol had no effect on discounting. (+info)
Behavioral methods used in the study of long-chain polyunsaturated fatty acid nutrition in primate infants.
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Domains of behavior may be broadly categorized as sensory, motor, motivational and arousal, cognitive, and social. Differences in these domains occur because of changes in brain structure and function. Docosahexaenoic acid (DHA; 22:6-23) and arachidonic acid (AA; 20:4-26) are major structural components of the brain that decrease when diets deficient in the essential fatty acids (EFA) alpha-linolenic acid and linoleic acid are consumed. Early electrophysiologic and behavioral studies in EFA-deficient rodents showed behavioral effects attributable to lower-than-normal accumulation of DHA and AA in the brain. More recently, electrophysiologic and behavioral studies in EFA-deficient primate infants and analogous studies in human infants have been conducted. The human infants were fed formulas that could result in lower-than-optimal accumulation of long-chain polyunsaturated fatty acids (LCPUFAs) in the brain during critical periods of development. This article describes the behavioral methods that have been used to study primate infants. These methods may be unfamiliar to many physicians and nutritionists who wish to read and interpret the human studies. The behavioral outcomes that have been evaluated in LCPUFA studies represent only a fraction of those available in the behavioral sciences. Specific developmental domains have been studied less often than global development, even though studies of nonhuman primates deficient in EFAs suggest that the former provide more information that could help target the underlying mechanisms of action of LCPUFAs in the brain. (+info)
Evaluating self-control and impulsivity in children with severe behavior disorders.
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Impulsivity and self-control involve a choice between a smaller, more immediate reinforcer and a larger, more delayed reinforcer. Impulsive behavior occurs when responding produces the more immediate, relatively smaller reinforcers at the expense of delayed larger reinforcers. Self-control occurs when responding produces delayed larger reinforcers at the expense of immediate smaller reinforcers. Recently, researchers in applied behavior analysis have suggested that evaluations of self-control and impulsivity are relevant to socially important behaviors. Further, common behavioral treatments such as differential reinforcement may be influenced by variables such as reinforcer delay. In this study, we showed that aggression, reinforced by access to food, could be maintained as impulsive behavior. The participants were 2 young boys with severe developmental disabilities. For both participants, descriptive observations, care provider report, and functional analyses suggested that aggression was reinforced by food access (and television access for 1 participant). Next, we introduced a differential reinforcement procedure in which appropriate mands were reinforced. After various manipulations, we showed that aggression occurred when it produced immediate but small reinforcers even though mands produced larger, more delayed reinforcers. However, both participants displayed self-control when the delay to reinforcement was signaled (with a hand gesture or a timer). (+info)
The pathological status of exercise dependence.
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OBJECTIVES: This study was concerned with the concept of exercise dependence. Levels of psychological morbidity, personality profiles, and exercise beliefs were compared among subjects screened for exercise dependence and eating disorders. METHOD: Adult female exercisers were allocated on the basis of questionnaire screening to one of the following groups: primary exercise dependence (n = 43); secondary exercise dependence, where there was the coincidence of exercise dependence and an eating disorder (n = 27); eating disorder (n =14); control, where there was no evidence of either exercise dependence or eating disorder (n = 110). Questionnaire assessment was undertaken of psychological morbidity, self esteem, weight and body shape dissatisfaction, personality, and exercise beliefs. RESULTS: Aside from a higher incidence of reported menstrual abnormalities, the primary exercise dependence group was largely indistinguishable from the controls. In stark contrast, the secondary exercise dependence group reported higher levels of psychological morbidity, neuroticism, dispositional addictiveness, and impulsiveness, lower self esteem, greater concern with body shape and weight, as well as with the social, psychological, and aesthetic costs of not exercising than the controls, but differed little from the eating disorder group. CONCLUSIONS: In the absence of an eating disorder, women identified as being exercise dependent do not exhibit the sorts of personality characteristics and levels of psychological distress that warrant the construction of primary exercise dependence as a widespread pathology. (+info)
Total serum cholesterol in relation to psychological correlates in parasuicide.
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BACKGROUND: Low cholesterol may act as a peripheral marker for parasuicide. AIMS: To examine the relationship between total serum cholesterol and psychological parameters in parasuicide. METHOD: Total serum cholesterol and self-rated scores for impulsivity, depression and suicidal intent were measured in 100 consecutive patients following parasuicide, pair-matched with normal and psychiatric control groups. RESULTS: Backward, stepwise multiple regression analysis revealed a significantly lower mean cholesterol in the parasuicide population (P < 0.01). Across all groups there was an independent significant (P < 0.01) negative correlation between cholesterol and self-reported scores of impulsivity. No correlation existed between cholesterol and scores for depression or suicidal intent. CONCLUSIONS: The data confirm previous reports of low cholesterol in parasuicide. This is the first reported investigation of the construct of impulsivity in relation to cholesterol. We hypothesise that the reported increased mortality in populations with low cholesterol may derive from increased suicide and accident rates consequent on increased tendencies to impulsivity in these populations. (+info)
Relationship between 5-HT function and impulsivity and aggression in male offenders with personality disorders.
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BACKGROUND: Reduced serotonergic (5-HT) function and elevated testosterone have been reported in aggressive populations. AIMS: To investigate relationships between impulsivity, aggression, 5-HT function and testosterone in male offenders with personality disorders. METHOD: Sixty male offenders with DSM-III-R personality disorders and 27 healthy staff controls were assessed using the Special Hospital Assessment of Personality and Socialisation (SHAPS), impulsivity and aggression ratings, d-fenfluramine challenge and plasma hormone concentrations. RESULTS: The SHAPS non-psychopaths and those with schizoid personality disorders had enhanced 5-HT function (prolactin response to d-fenfluramine). Reduced 5-HT function was found in offenders with DSM-III-R borderline personality disorders and those with a history of repeated self-harm or alcohol misuse. The 5-HT function was inversely correlated more strongly with impulsivity than with aggression. Plasma testosterone correlated positively with aggressive acts. The SHAPS primary psychopaths had lower initial cortisol and higher testosterone concentrations than controls. CONCLUSIONS: Future studies are needed to investigate regional brain 5-HT function. (+info)
Impulsive choice induced in rats by lesions of the nucleus accumbens core.
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Impulsive choice is exemplified by choosing a small or poor reward that is available immediately, in preference to a larger but delayed reward. Impulsive choice contributes to drug addiction, attention-deficit/hyperactivity disorder, mania, and personality disorders, but its neuroanatomical basis is unclear. Here, we show that selective lesions of the nucleus accumbens core induce persistent impulsive choice in rats. In contrast, damage to two of its afferents, the anterior cingulate cortex and medial prefrontal cortex, had no effect on this capacity. Thus, dysfunction of the nucleus accumbens core may be a key element in the neuropathology of impulsivity. (+info)
Neuropsychological analyses of impulsiveness in childhood hyperactivity.
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BACKGROUND: Neuropsychological analyses of impulsiveness are needed to refine assessment of attention-deficit hyperactivity disorder (ADHD). AIMS: To investigate specific impairments in hyperactive children in a neuropsychological task battery of impulsiveness, the Maudsley Attention and Response Suppression (MARS) task battery, and to identify the neural substrates. METHOD: Impulsiveness was assessed using different tasks of inhibitory control and time management (MARS) in 55 children with ADHD, other diagnoses and controls. Functional magnetic resonance images were obtained from adolescents with and without ADHD during three of the tasks. RESULTS: Children with ADHD, but not psychiatric controls, were impaired on tests of response inhibition, but not of motor timing. Reduced right prefrontal activation was observed in hyperactive adolescents during higher level inhibition and delay management, but not during simple sensorimotor coordination. CONCLUSIONS: Attention-deficit hyperactivity disorder is characterised by specific deficits in tasks of motor response inhibition, but not motor timing, and by dysfunction of frontostriatal brain regions. (+info)