The relationship of structural ischemic brain damage to neurobehavioural deficit: the effect of postischemic MK-801

Global cerebral ischemia is well known to cause neuronal necrosis in selectively vulnerable sectors of the hippocampus. Since the hippocampus of the rat is involved in spatial navigation, learning, and memory, selective deficits in these abilities may arise from ischemic brain damage. Previous studies have shown (a) a detectable neurobehavioural deficit due to ischemic brain damage limited to half of the CA1 sector of the hippocampus and (b) a reduction of ischemic neuronal necrosis with the noncompetitive N-methyl-D-Aspartate (NMDA) antagonist MK-801. This study was designed to determine the relationship between the improvement in structural brain damage in postischemically treated rats and any improvement in neurobehavioural performance, using a learning-set water task. Seventeen male Wistar rats received 10.5 min of forebrain ischemia induced by carotid clamping and hypotension. Brain temperature was estimated with probes in the temporalis muscle. Ten of these animals received no therapy (controls), and seven animals received 5 mg/kg MK-801 iv, 20 min postischemia. Six additional rats underwent a sham operation. Postischemic hypothermia was prevented with heating lamps. Four controls and one MK-801 treated animal died. The survivors were then tested on a place learning-set task in a swimming pool paradigm, and quantitative histopathologic analysis of their entire brains was done. The learning-set task revealed defects in spatial navigation, reflected as increased errors and latency in the performance of the untreated control rats. The performance of the MK-801 treated group progressively approached that of sham-operated rats over the course of testing and was significantly better than controls. Importantly, no long-term detrimental effect of MK-801 on the learning-set task performance was seen. Quantitative neuropathology revealed significantly less damage in the MK-801 treated group in all major brain regions. In the hippocampus, MK-801 treated animals showed hippocampal damage limited to the vulnerable portion of the pyramidal cell band comprising 48.8% of the CA1 pyramidal cells, as opposed to 72.4% in untreated controls. Extra-hippocampal damage was evident only in untreated control animals. MK-801 totally prevented neuronal necrosis in both the cerebral cortex and striatum and also prevented infarction in the neocortex and thalamus. Three conclusions emerge from the study. First, postischemic MK-801 mitigates structural brain damage in several brain regions in the absence of concomitant hypothermia. Second, neurobehavioural performance appears to be improved by MK-801 when performance trends are examined, but is somewhat less sensitive than quantitated histopathology due to compounding interanimal variation in performance abilities.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effects of event rate and display time on sustained attention in hyperactive,normal, and control children

Two experiments were conducted to determine whether hyperactive boys have a unique deficit in sustained attention. Groups with DSM-III diagnoses of attention deficit disorder (ADDH), conduct disorder (CD), ADDH+CD, and learning disorder were compared with normal controls on the Continuous Performance Task. In Experiment 1, stimulus presentation rate (stimulus onset asynchrony, SOA) and display time were varied to manipulate attentional demand, and speed and accuracy of performance were measured. The ADDH group was uniquely affected, with less accurate performance at the fastest and slowest SOA. To distinguish the effects of time on task and SOA, the duration of each SOA condition was held constant in Experiment 2. The poorer performance of the ADDH group at the fastest SOA was no longer evident. This finding indicates that the deficit of sustained attention in boys who have ADDH is associated with a greater susceptibility to refractory effects, which is influenced by practice.This research was supported by the Ontario Mental Health and Ruth Schwartz Foundations through a graduate fellowship awarded to P. Chee and a research grant to R. Schachar, G. Logan, and R. Wachsmuth. Dr. Schachar was also supported by the Canadian Psychiatric Research Foundation. This article is based, in part, on a doctoral dissertation submitted by the first author to the Ontario Institute for Studies in Education. The authors thank Dr. John Lovering and the staff of the Departments of Psychiatry and Psychology, The Hospital for Sick Children, for their cooperation in the conduct of this study. This paper was prepared with the assistance of the Medical Publications Department, The Hospital for Sick Children, Toronto.     

Relationships between the Dark Triad and humor styles: A replication and extension

Two hundred undergraduate students completed paper-and-pencil measures of the Dark Triad (Machiavellianism, narcissism, and psychopathy) and the Humor Styles Questionnaire, which taps two adaptive (affiliative and self-enhancing) and two maladaptive (aggressive and self-defeating) styles of humor. The first purpose of the study was to replicate relationships between these variables reported by Veselka et al. (2010). The second purpose was to expand on their results by investigating relationships between several sub-factors of the Dark Triad (in addition to global scores) and the humor styles. Results provided substantial replication of Veselka et al. at the global level and, at the sub-factor level, provided additional insights into the potential role of adaptive and maladaptive humor styles in the personality dynamics of individuals characterized by the various facets of the Dark Triad.     

Changes in materialism,changes in psychological well-being: Evidence from three longitudinal studies and an intervention experiment

Few studies have examined how changes in materialism relate to changes in well-being; fewer have experimentally manipulated materialism to change well-being. Studies 1, 2, and 3 examined how changes in materialistic aspirations related to changes in well-being, using varying time frames (12 years, 2 years, and 6 months), samples (US young adults and Icelandic adults), and measures of materialism and well-being. Across all three studies, results supported the hypothesis that people’s well-being improves as they place relatively less importance on materialistic goals and values, whereas orienting toward materialistic goals relatively more is associated with decreases in well-being over time. Study 2 additionally demonstrated that this association was mediated by changes in psychological need satisfaction. A fourth, experimental study showed that highly materialistic US adolescents who received an intervention that decreased materialism also experienced increases in self-esteem over the next several months, relative to a control group. Thus, well-being changes as people change their relative focus on materialistic goals.     

Future Professionals and Managers: Their Attitudes Toward Unions, Organizational Beliefs, and Work Ethic

The authors replicate and extend the research on future workers' union attitudes, organizational beliefs, and work ethic. Selected demographic and attitudinal data were collected from a sample of 644 students at a small, western Pennsylvania university. Compared to earlier research on pre-employment predictors of union attitudes, this study is based on a much larger sample size and includes a cross-section of majors. The results offer additional support for the family socialization process; in general, future professionals and business managers are more sympathetic to labor unions if they were children of union members. In addition, the results show that student major has a significant and systematic impact on both positive and negative union attitudes.     

Physical self-concept and self-esteem mediate cross-sectional relations of physical activity and sport participation with depression symptoms among adolescent girls.

The authors tested whether physical self-concept and self-esteem would mediate cross-sectional relations of physical activity and sport participation with depression symptoms among 1,250 girls in 12th grade. There was a strong positive relation between global physical self-concept and self-esteem and a moderate inverse relation between self-esteem and depression symptoms. Physical activity and sport participation each had an indirect, positive relation with global physical self-concept that was independent of objective measures of cardiorespiratory fitness and body fatness. These correlational findings provide initial evidence suggesting that physical activity and sport participation might reduce depression risk among adolescent girls by unique, positive influences on physical self-concept that operate independently of fitness, body mass index, and perceptions of sports competence, body fat, and appearance.     

Thawing Rivalries and Fading Friendships: An Experimental Approach to Rapprochement and Alienation

Although international relations (IR) theorists generally assume that actors update their beliefs about the intentions of adversaries and allies based on structure, costly signaling, and past actions, little is known about how the process of rapprochement between adversaries differs from the process of alienation between allies, particularly with respect to the nature and degree of costly signaling. Furthermore, until recently the role of the individual in these processes has only been engaged by a small number of scholars, and fewer still have integrated this perspective with conventional approaches to rapprochement and alienation. Drawing from findings in social psychology, We present results from an original survey experiment showing that (1) political belief systems are a powerful determinant of how individuals perceive the intentions of other states, more so than an observed state's signaling behavior; (2) there are diminishing returns in increasing the cost of a signal; and (3) hostile signals are more effective in signaling intent than reassuring signals.     

Preference exploration and learning: the role of intensiveness and extensiveness of experience

In this article, the authors partition the construct of experience into intensiveness (i.e., amount) and extensiveness (i.e., breadth) and examine the impact of the two specific types of experience on preference learning. In the first three studies, the authors' theory that experience can be partitioned into intensiveness (i.e., amount) and extensiveness (i.e., breadth) of experience and that extensiveness has a greater impact on preference learning is supported in environments where prior experience is measured. Further, in study 4 they demonstrate that extensiveness or breadth of experience exerts a larger influence on preference learning in an experiment where each unique type of experience is manipulated as well as measured.