Differential effects of predator stress and the antidepressant tianeptine on physiological plasticity in the hippocampus and basolateral amygdala

Stress can profoundly affect memory and alter the functioning of the hippocampus and amygdala. Studies have also shown that the antidepressant tianeptine can block the effects of stress on hippocampal and amygdala morphology and synaptic plasticity. We examined the effects of acute predator stress and tianeptine on long-term potentiation (LTP; induced by 100 pulses in 1 s) and primed burst potentiation (PB; a low threshold form of LTP induced by only five physiologically patterned pulses) in CA1 and in the basolateral nucleus (BLA) of the amygdala in anesthetized rats. Predator stress blocked the induction of PB potentiation in CA1 and enhanced LTP in BLA. Tianeptine blocked the stress-induced suppression of PB potentiation in CA1 without affecting the stress-induced enhancement of LTP in BLA. In addition, tianeptine administered under non-stress conditions enhanced PB potentiation in the hippocampus and LTP in the amygdala. These findings support the hypothesis that acute stress impairs hippocampal functioning and enhances amygdaloid functioning. The work also provides insight into the actions of tianeptine with the finding that it enhanced electrophysiological measures of plasticity in the hippocampus and amygdala under stress, as well as non-stress, conditions.     

Social Identity Theory: a critical synthesis of its bases, evidence and controversies

The social identity theory (SIT) and the self-categorization theory have had considerable influence on contemporary Social Psychology, making notable contributions to our understanding of the social dimension of behaviour. In the present work, we summarise the bases of these theories and critically review the most controversial elements of SIT, exploring its limits and potential. As shown here, the literature offers a heterogeneous body of research that includes outstanding efforts of synthesis and integration, but also numerous fragmentary studies and decontextualized interpretations that have generated distorted views of group behaviour. Taking into account the multidimensional, contextually mediated, dynamic and functional nature of identitary processes, which clearly emerge in the most serious works in the field, there is obviously a need to review the epistemological and methodological tools currently employed, with a view to developing practices that allow the study of group phenomena in a manner more suited to their complexity.     

When Thinking Rationally Increases Biases: The Role of Rational Thinking Style in Escalation of Commitment

This paper reports three studies examining the relationship between the rational thinking style (RTS, i.e. individual differences in relying on a conscious, analytical, and relatively affect‐free information processing system) and decision quality in an escalation situation. In contrast to conventional wisdom that rational thinking increases decision quality, but consistent with the predictions derived from the cognitive dissonance theory, results of Studies 1 and 2 revealed that high scorers in Pacini and Epstein's (1999 ) rationality inventory were more likely to have escalation bias than were low scorers. The results further showed that only the ability component of rationality, not the engagement component, was positively correlated with escalating commitment. Similar patterns of results were obtained for situations when participants were personally responsible for prior decisions (Study 1) and when they were not (Study 2). Results of Study 3 showed that the underlying process responsible for the effect of RTS on the escalating tendency is that RTS increases beliefs in prior decisions, which in turn increases escalation. Implications for our understanding of escalation of commitment, rationality theory, and managerial practices are discussed. Cet article rend compte de 3 études examinant la relation entre le style de pensée rationnelle (RTS i.e. les différences individuelles reposent sur un système de traitement de l’information consciente, analytique et relativement libre d’affects) et la qualité de la décision dans une situation d’escalade d’engagement. Contrairement à l’opinion communément admise pour laquelle la pensée rationnelle accroît la qualité de la décision, mais consistante avec les prédictions découlant de la théorie de la dissonance cognitive, les résultats des études 1 et 2 indiquent que des personnes obtenant un score élevéà l’Inventaire Rationnel‐Expérientiel de Pacini et Esptein (1999) sont plus enclines à tomber dans le piège de l’escalade d’engagement que celles dont le score est bas. D’autres résultats montrent que la capacitéà la rationalité, non celle à l’engagement, est positivement corrélée avec l’escalade d’engagement. Des résultats semblables sont obtenus lors de situations où les participants sont personnellement responsables de leurs décisions antérieures (Etude 1) ou non (Etude 2). Les résultats de l’étude 3 montrent que le processus responsable de l’effet du RTS sur la tendance à s’engager est le suivant: il accroît les croyances dans les décisions antérieures qui augmentent à leur tour l’engagement. Ces résultats nous permettent de mieux comprendre l’escalade d’engagement, la théorie rationnelle et les pratiques managériales.     

Impaired reward processing by anterior cingulate cortex in children with attention deficit hyperactivity disorder

Decades of research have examined the neurocognitive mechanisms of cognitive control, but the motivational factors underlying task selection and performance remain to be elucidated. We recently proposed that anterior cingulate cortex (ACC) utilizes reward prediction error signals carried by the midbrain dopamine system to learn the value of tasks according to the principles of hierarchical reinforcement learning. According to this position, disruption of the ACC–dopamine interface can disrupt the selection and execution of extended, task-related behaviors. To investigate this issue, we recorded the event-related brain potential (ERP) from children with attention deficit hyperactivity disorder (ADHD), which is strongly associated with ACC–dopamine dysfunction, and from typically developing children while they navigated a simple “virtual T-maze” to find rewards. Depending on the condition, the feedback stimuli on each trial indicated that the children earned or failed to earn either money or points. We found that the reward positivity, an ERP component proposed to index the impact of dopamine-related reward signals on ACC, was significantly larger with money feedback than with points feedback for the children with ADHD, but not for the typically developing children. These results suggest that disruption of the ACC–dopamine interface may underlie the impairments in motivational control observed in childhood ADHD.