Low-dose mecamylamine improves learning of rats in the radial-arm maze repeated acquisition procedure

The nicotinic antagonist mecamylamine has been widely shown to cause cognitive impairment. However, these effects are mainly seen with high doses. There have been scattered findings that low doses of mecamylamine can have the opposite effect. This may be due to opposite effects of low doses of mecamylamine. In the current study, an extensive dose-effect function of mecamylamine was characterized in the low-dose range. Adult female Sprague-Dawley rats were trained on a repeated acquisition procedure on an automated 8-arm radial maze. Three of the eight arms were designated as correct for any particular session. Five trials per session were run. The number of errors per trial to find the three correct arms was determined. The rats were trained on the repeated acquisition procedure for at least 18 sessions at which time they showed reliable learning each session. Then, the effect of low doses of mecamylamine between 0 and 1 mg/kg were assessed in a repeated measures counterbalanced design. This dose range of mecamylamine did not affect performance on the first trial when the rats were na?ve to the array to be learned. On trials 2-5 a significant (p<.025) quadratic dose-effect function was seen over this dose range. The most substantial effect was seen with 0.125 mg/kg of mecamylamine, which caused a significant (p<.05) improvement relative to the saline control condition. The effect diminished with increasing mecamylamine doses and with the 1 mg/kg dose choice accuracy was back to control levels. This study showed that low doses of mecamylamine can effectively improve learning. A U-shaped dose-effect curve was documented. This suggests possible low-dose nicotinic antagonist lines of treatment for cognitive impairment.     

Investigating systematic individual differences in sleep-deprived performance on a high-fidelity flight simulator

Laboratory research has revealed considerable systematic variability in the degree to which individuals' alertness and performance are affected by sleep deprivation. However, little is known about whether or not different populations exhibit similar levels of individual variability. In the present study, we examined individual variability in performance impairment due to sleep loss in a highly select population of militaryjet pilots. Ten active-duty F-117 pilots were deprived of sleep for 38 h and studied repeatedly in a high-fidelity flight simulator. Data were analyzed with a mixed-model ANOVA to quantify individual variability. Statistically significant, systematic individual differences in the effects of sleep deprivation were observed, even when baseline differences were accounted for. The findings suggest that highly select populations may exhibit individual differences in vulnerability to performance impairment from sleep loss just as the general population does. Thus, the scientific and operational communities' reliance on group data as opposed to individual data may entail substantial misestimation of the impact of job-related stressors on safety and performance.     

Establishing a Descriptive Database for Teachers with Aggressive Students

While establishing a database that describes students' aggressive behaviors and the conditions present at the time of occurrence, we discovered a variety of definitions of aggression in the literature. This lack of consistency limits the information provided to teachers working with the frequent problem of violence. We propose an inclusive and verifiable definition of aggression gleaned from experience and the literature. The definition incorporates verbal, paraverbal, nonverbal, and physical aggression. Validation is presented from the literature, and from 39 practicing teachers who used the definition to categorize 659 target behaviors. The teachers' level of agreement with the authors' categorization was 93% (median).     

WAIS test-retest reliability for a clinical out-patient sample.

WAIS test-retest reliabilities were calculated for a clinical out-patient sample with testing intervals varying from 1 to 10 yr. There was no relationship between test-retest interval and the stability of test scores and the correlations between IQs were quite satisfactory (Full Scale IQ = .897, Verbal IQ = .906, Performance IQ = .876). Reliabilities remained high even when the sample was divided by diagnosis into organic, neurotic, personality disorder, and schizophrenic subgroups.     

Evolutionary perspectives on imitation: is a comparative psychology of social learning possible?

Studies of imitation in animals have become numerous in recent times, but do they contribute to a comparative psychology of social learning? We review this burgeoning field to identify the problems and prospects for such a goal. Difficulties of two main kinds are identified. First, researchers have tackled questions about social learning from at least three very different theoretical perspectives, the "phylogenetic", "animal model", and "adaptational". We examine the conflicts between them and consider the scope for integration. A second difficulty arises in the methodological approaches used in the discipline. In relation to one of these - survey reviews of published studies - we tabulate and compare the contrasting conclusions of nine articles that together review 36 studies. The basis for authors' disagreements, including the matters of perceptual opacity, novelty, sequential structure, and goal representation, are examined. In relation to the other key method, comparative experimentation, we identify 12 studies that have explicitly compared species' imitative ability on similar tasks. We examine the principal problems of comparing like with like in these studies and consider solutions, the most powerful of which we propose to be the use of a systematic range of task designs, rather than any single "gold standard" task.     

Psychopathy and behavioral correlates of victim injury in serious juvenile offenders

The study examines delinquent behavior and psychopathy and assesses their relationship to victim injury in a population of 168 incarcerated juvenile delinquent males with lengthy histories of criminal and violent behavior. A series of multiple regressions found that 17% of the variance associated with level of victim injury was accounted for by a model that included the three-factor model of the Psychopathy Checklist: Youth Version [Forth, Kosson, and Hare, 2003], criminal versatility, and age of onset of criminal offending. Notably, anger and DSM-IV symptoms of conduct disorder were not related to level of victim injury. The results of this study support an escalation hypothesis where individuals with earlier onset to criminal behavior and greater criminal versatility escalate to more severe violence. The current results demonstrate the importance of integrating established theories of juvenile delinquency when explaining severe violence in youth.