Regulation and Mechanism of L-Type Calcium Channel Activation via V1a Vasopressin Receptor Activation in Cultured Cortical Neurons

We have sought to elucidate the biochemical mechanisms that underlie the memory enhancing properties of the neural peptide vasopressin. Toward that goal we have investigated vasopressin induction of calcium signaling cascades, long held to be involved in long-term memory function, in neurons derived from the cerebral cortex, a brain region associated with long-term memory. Our previous studies demonstrated that in cultured cortical neurons, V1a vasopressin receptor (V1aR) activation resulted in a sustained rise in intracellular calcium concentration that was dependent on calcium influx (Son & Brinton, 1998). To investigate the mechanism of V1aR-induced calcium influx, we investigated V1aR activation of the calcium channel subtype(s) in cortical neurons cultured from Sprague-Dawley rat embryonic day 18 fetuses. The results of these analyses demonstrated that the L-type calcium channel blocker nifedipine blocked 250 nM V1 vasopressin receptor agonist (V1 agonist)-induced calcium influx. Intracellular calcium imaging analyses using fura-2AM demonstrated that blockade of L-type calcium channels prevented the 250 nM V1 agonist-induced rise in intracellular calcium concentration. These results indicate that the influx of extracellular calcium via L-type calcium channels is an essential step in the initiation of the V1 agonist-induced rise in intracellular calcium concentration. To determine the mechanism of V1aR activation of L-type calcium channels, regulatory components of the phosphatidylinositol signaling pathway were investigated. The results of these analyses demonstrated that V1 agonist-induced calcium influx was blocked by both a phospholipase C inhibitor (U-73122) and a protein kinase C inhibitor (bisindolylmaleimide I). Further analysis of V1aR activation of protein kinase C (PKC) demonstrated that V1 agonist induced PKC activity within 1 min of exposure in cultured cortical neurons. These data indicate that in cultured cortical neurons, V1aR activation regulates the influx of extracellular calcium via L-type calcium channel activation through a protein kinase-C-dependent mechanism. The results of these studies provide biochemical mechanisms by which vasopressin could enhance memory function. Those mechanisms include a complex cascade that is initiated by activation of the phosphatidylinositol pathway, activation of protein kinase C, followed by phosphorylation of L-type calcium channels to initiate the influx of extracellular calcium to activate a cascade of calcium-dependent release of intracellular calcium.     

Metacognitive and control strategies in study-time allocation

This article investigates how people's metacognitive judgments influence subsequent study-time-allocation strategies. The authors present a comprehensive literature review indicating that people allocate more study time to judged-difficult than to judged-easy items--consistent with extant models of study-time allocation. However, typically, the materials were short, and participants had ample time for study. In contrast, in Experiment 1, when participants had insufficient time to study, they allocated more time to the judged-easy items than to the judged-difficult items, especially when expecting a test. In Experiment 2, when the materials were shorter, people allocated more study time to the judged-difficult materials. In Experiment 3, under high time pressure, people preferred studying judged-easy sonnets; under moderate time pressure, they showed no preference. These results provide new evidence against extant theories of study-time allocation.     

The influence of sex bias upon compliance with expert power

The present study evolved from the belief that sex bias influences the degree of expert power which the expert has in relation to the perceiver. Therefore, the influence of level of expertise, sex of the expert, sex of the influencee, and sex domination of the expert's occupation upon compliance was examined. Separate experiments were conducted for the male- and female-dominated occupations. Subjects' degree of compliance was measured by their responses to three recommendations contained in an in-basket. The three-way analyses of variance revealed that only expertise significantly affected subjects' degree of compliance. Results are discussed in terms of the presence of outside recognition of competence and legitimate power.     

Simplicity and generalization: Short-cutting abstraction in children's object categorizations

Development in any domain is often characterized by increasingly abstract representations. Recent evidence in the domain of shape recognition provides one example; between 18 and 24 months children appear to build increasingly abstract representations of object shape [Smith, L. B. (2003). Learning to recognize objects. Psychological Science, 14, 244-250]. Abstraction is in part simplification because it requires the removal of irrelevant information. At the same time, part of generalization is ignoring irrelevant differences. The resulting prediction is this: simplification may enable generalization. Four experiments asked whether simple training instances could shortcut the process of abstraction and directly promote appropriate generalization. Toddlers were taught novel object categories with either simple or complex training exemplars. We found that children who learned with simple objects were able to generalize according to shape similarity, typically relevant for early object categories, better than those who learned with complex objects. Abstraction is the product of learning; using simplified - already abstracted instances - can short-cut that learning, leading to robust generalization.     

The ameliorating effect of oroxylin A on scopolamine-induced memory impairment in mice

Oroxylin A is a flavonoid and was originally isolated from the root of Scutellaria baicalensis Georgi., one of the most important medicinal herbs in traditional Chinese medicine. The aim of this study was to investigate the ameliorating effects of oroxylin A on memory impairment using the passive avoidance test, the Y-maze test, and the Morris water maze test in mice. Drug-induced amnesia was induced by administering scopolamine (1 mg/kg, i.p.) or diazepam (1 mg/kg, i.p.). Oroxylin A (5 mg/kg) significantly reversed cognitive impairments in mice by passive avoidance and the Y-maze testing (P<.05). Oroxylin A also improved escape latencies in training trials and increased swimming times and distances within the target zone of the Morris water maze (P<.05). Moreover, the ameliorating effects of oroxylin A were antagonized by both muscimol and diazepam (0.25 mg/kg, i.p., respectively), which are GABA(A) receptor agonists. Furthermore, oroxylin A (100 microM) was found to inhibit GABA-induced inward Cl(-) current in a single cortical neuron. These results suggest that oroxylin A may be useful for the treatment of cognitive impairments induced by cholinergic dysfunction via the GABAergic nervous system.     

Metacognitive control and optimal learning

The notion of optimality is often invoked informally in the literature on metacognitive control. We provide a precise formulation of the optimization problem and show that optimal time allocation strategies depend critically on certain characteristics of the learning environment, such as the extent of time pressure, and the nature of the uptake function. When the learning curve is concave, optimality requires that items at lower levels of initial competence be allocated greater time. On the other hand, with logistic learning curves, optimal allocations vary with time availability in complex and surprising ways. Hence there are conditions under which optimal strategies will be relatively easy to uncover, and others in which suboptimal time allocation might be expected. The model can therefore be used to address the question of whether and when learners should be able to exercise good metacognitive control in practice.     

Contextualization in Perspective

In this article, we examine the hypothesis that problem comprehension and computational processes interact during the solving of an arithmetic word problem. Two experiments tested subjects on a series of addition and subtraction word problems, the content of which varied on the basis of problem type and on the magnitude of the numbers involved (problem size). Performance data are presented and analyzed in terms of solution reaction times and error patterns. Results confirmed the main effects of problem size and problem type as factors determining reaction times but failed to show any significant interaction between the two factors. These results suggest that the cognitive processes involved in understanding an arithmetic word problem and in performing the required computations are best explained by a serial processing model. The absence of an interaction between problem comprehension and computational processes questions the notion that automatized retrieval facilitates problem solving and assertions suggesting that increasing computational requirements can interfere with problem-solving performance.     

How perceived interpersonal justice relates to job burnout and intention to leave: The role of leader–member exchange and cognition‐based trust in leaders

Intense competition among companies makes it particularly important for organizations to retain talented and skilled employees to maintain their competitive advantage. This study examines the linkage between employees' perceptions of the interpersonal justice demonstrated by their leaders and consequent job burnout resulting in turnover intention by focusing on the mediating role of leader–member exchange (LMX) as well as the moderating role of employees' cognition‐based trust in their leaders. Data were obtained from 158 MBA students attending a large university in South Korea. Using structural equation modelling, we examined an integrative model that combines interpersonal justice, LMX, job burnout, and turnover intention. The results reveal that (a) LMX partially mediates the relationships between interpersonal justice and job burnout and (b) employees' cognition‐based trust in their leaders moderates the relationship between LMX and job burnout. By examining the mediating role of LMX as well as the moderating role of cognition‐based trust in the relationship between perceived interpersonal justice and employee job burnout, this study (1) provides a comprehensive explanation of employee job burnout and (2) outlines the implications for job burnout research and practice.     

Smells like cooperation? Unpleasant body odor and people's perceptions and helping behaviors

Scents are omnipresent in our daily world and they are of great importance as represented by the use of perfumes or fragrances in the work environment. Even though it has been argued that bad scents invoke negative judgments, we argued and demonstrated that a bad body odor elicits feelings of pity in others (Experiment 1) and increases prosocial behavior (Experiment 2). Further, we showed that only if a person is not held accountable for his own body odor this elevated other's prosocial behavior (Experiment 3). These findings provide a novel perspective on the way human body odor affects our perceptions and consequent behaviors.     

Attention to context: U.S. and Japanese children's emotional judgments

A growing number of studies suggest cultural differences in the attention and evaluation of information in adults (Masuda & Nisbett, 2001; Markus & Kitayama, 1991; Hedden, Ketay, Aron, Markus, & Gabrieli, 2008). One cultural comparison, between Westerners, such as Americans, and Easterners, such as the Japanese, suggest that Westerners typically focus on a central single object in a scene while Easterners often integrate their judgment of the focal object with surrounding contextual cues. There are few studies of whether such cultural differences are evident in children. This study examined 48 monolingual Japanese-speaking children residing in Japan and 48 monolingual English-speaking children residing in the U.S.A. (40 to 60 month-olds) in a task asking children to complete a picture by adding the proper emotional expression to a face. The key variable was the context and shift in context from the preceding trial for the same pictured individual. Japanese children were much more likely to shift their judgments with changes in context whereas children from the United States treated facial expression in a more trait-like manner, maintaining the same expression for the individual across contexts.