Impact of predatory threat on fear extinction in Lewis rats

Humans with post-traumatic stress disorder (PTSD) are deficient at extinguishing conditioned fear responses. A study of identical twins concluded that this extinction deficit does not predate trauma but develops as a result of trauma. The present study tested whether the Lewis rat model of PTSD reproduces these features of the human syndrome. Lewis rats were subjected to classical auditory fear conditioning before or after exposure to a predatory threat that mimics a type of traumatic stress that leads to PTSD in humans. Exploratory behavior on the elevated plus maze 1 wk after predatory threat exposure was used to distinguish resilient vs. PTSD-like rats. Properties of extinction varied depending on whether fear conditioning and extinction occurred before or after predatory threat. When fear conditioning was carried out after predatory threat, PTSD-like rats showed a marked extinction deficit compared with resilient rats. In contrast, no differences were seen between resilient and PTSD-like rats when fear conditioning and extinction occurred prior to predatory threat. These findings in Lewis rats closely match the results seen in humans with PTSD, thereby suggesting that studies comparing neuronal interactions in resilient vs. at-risk Lewis rats might shed light on the causes and pathophysiology of human PTSD.Following a severe traumatic event, some individuals manifest a syndrome, known as post-traumatic stress disorder (PTSD), characterized by repeated painful recollection of the trauma, avoidance of trauma reminders, intrusive thoughts, startle, hyperarousal, and disturbed sleep. Lifetime prevalence of PTSD ranges from 1.4% to 11.2% in representative samples (Afifi et al. 2010). Review of heritability studies indicate that there is a significant genetic component to PTSD (Nugent et al. 2008) as shared genes explain approximately 25%–38% of variability in PTSD symptom clusters and total symptoms (Afifi et al. 2010). Moreover, PTSD heritability coincides with that of other psychiatric conditions such as generalized anxiety, panic disorder, and depression (Chantarujikapong et al. 2001; Fu et al. 2007), suggesting that these disorders gain expression through common biological pathways.Although our understanding of PTSD has improved recently, we still have a limited grasp of the factors that predispose some to be at risk for PTSD, as well as those contributing to PTSD expression following trauma. In part, this situation results from the ethical limitations associated with human studies. For example, humans cannot be randomly assigned to trauma, and, importantly, the invasive techniques required to study the pathophysiology of PTSD can be used only in animals. Thus, a promising approach toward understanding the underlying pathophysiology of PTSD would be to study the disease in a valid animal model of the human syndrome.Fortunately, much work has already been performed to define an animal model of PTSD that reproduces the salient features of the human syndrome (see Adamec et al. 2006; Cohen et al. 2006a; Siegmund and Wotjak 2006). The most promising research has focused on the impact of exposing rodents to species-relevant threatening stimuli that mimic the kind of life-and-death circumstances that precipitates PTSD in humans. Indeed, rodents exposed to predators or their odor develop long-lasting (3 wk or more) manifestations of anxiety as seen in a variety of behavioral assays including the elevated plus maze (EPM), social interaction test, and acoustic startle (Adamec and Shallow 1993; Blanchard et al. 2003; Adamec et al. 2006). The inherent strength of this species-relevant stimulus was demonstrated in studies where predator odor served as an unconditioned stimulus to support cued or contextual fear conditioning (Blanchard et al. 2001; McGregor et al. 2002). As is the case with human PTSD, differential vulnerability to predatory threat was also observed in rodents. In one study, for instance, the propensity of different strains of rats to develop extreme behavioral manifestations of anxiety (EBMAs) as a result of predatory threat has been characterized, revealing that a much higher proportion (50%) of Lewis rats (an inbred strain) develops EBMAs as a result of an intense predatory threat compared with 10% of Fisher rats and 20% of Sprague–Dawley rats (Cohen et al. 2006b).Although these results are promising, it remains unclear whether Lewis rats also exhibit traits that parallel the pathophysiology of human PTSD. One such factor, thought to play a particularly critical role in the persistence of PTSD, is a compromised ability to extinguish fear memories (for review, see Quirk and Mueller 2008). Two main lines of evidence support this notion. First, in functional imaging studies, the brain structures that normally support fear expression and extinction (for review, see Pape and Pare 2010) show abnormal activity patterns in PTSD (Rauch et al. 2006; Shin et al. 2006; Bremner et al. 2008; Milad et al. 2009). Second, several studies have reported that individuals with PTSD are deficient at extinguishing classically conditioned fear responses (Orr et al. 2000; Peri et al. 2000; Blechert et al. 2007; Milad et al. 2008, 2009). Of particular interest, a study of identical twins discordant for trauma exposure has revealed that this extinction deficit was not a pre-existing condition but developed as a result of trauma (Milad et al. 2008). Given the possibility that an inability to extinguish fear might contribute to the maintenance of PTSD, we therefore tested whether Lewis rats reproduced the properties of extinction seen in human PTSD.     

The effect of gender, ethnicity, and income on college students' use of communication technologies

Because campus officials are relying on personal communication technologies to communicate with students, a question arises about access and usage. Although communication technologies are popular among college students, some evidence suggests that differences exist in ownership and use. We examined patterns of student ownership and use of cell phones and use of instant messaging, focusing on three predictors of digital inequality: gender, ethnicity, and income. Logistic and hierarchical linear regression analyses were used to analyze results from 4,491 students. The odds that female and white students owned cell phones were more than twice as high as for men and African-American students. Students in the $100,000-$149,000 per year income bracket were more than three times as likely to own a cell phone than those from the median bracket. However, being female, African-American, and/or from the highest income brackets was positively predictive of the number of text messages sent and the amount of time spent talking on a cell phone per week. We found no differences between students on the use of instant messaging. Implications of these results, as well as areas for further research, are provided.     

日益孤独的中国老年人：一项横断历史研究

随着社会的巨大变迁, 我国老年人孤独感水平可能逐年增高。通过采用横断历史研究的方法, 对使用UCLA孤独量表(第三版)调查老年人孤独感的25篇文献进行元分析, 调查年代跨度为1995年至2011年, 共涉及13280名老年人。研究结果表明：(1)我国老年人孤独感水平随年代的变迁呈上升趋势; (2)不同婚姻状况、不同性别老年人的孤独感水平随年代均呈上升趋势; (3)老年人孤独感水平存在婚姻状况差异, 但不存在性别差异。     

Spatial localization of touch in the first year of life: early influence of a visual spatial code and the development of remapping across changes in limb position

Two experiments investigated infants' ability to localize tactile sensations in peripersonal space. Infants aged 10 months (Experiment 1) and 6.5 months (Experiment 2) were presented with vibrotactile stimuli unpredictably to either hand while they adopted either a crossed- or uncrossed-hands posture. At 6.5 months, infants' responses were predominantly manual, whereas at 10 months, visual orienting behavior was more evident. Analyses of the direction of the responses indicated that (a) both age groups were able to locate tactile stimuli, (b) the ability to remap visual and manual responses to tactile stimuli across postural changes develops between 6.5 and 10 months of age, and (c) the 6.5-month-olds were biased to respond manually in the direction appropriate to the more familiar uncrossed-hands posture across both postures. The authors argue that there is an early visual influence on tactile spatial perception and suggest that the ability to remap visual and manual directional responses across changes in posture develops between 6.5 and 10 months, most likely because of the experience of crossing the midline gained during this period.     

Resting on laurels: the effects of discrete progress markers as subgoals on task performance and preferences

This article investigates the influence of progress certainty and discrete progress markers (DPMs) on performance and preferences. The authors suggest that the effects of DPMs depend on whether progress certainty is high or low. When the distance to the goal is uncertain, DPMs can help reduce uncertainty and thus improve performance and increase preference. However, when the distance to the goal is certain, DPMs may generate complacency, sway motivation away from the end goal, and decrease performance in the task, as well as its appeal. Therefore, the addition of more information, feedback, or progress indicators may not always improve task performance and preference for the task. The authors validate these claims in 4 experiments.     

Internalism,externalism, and transcendental idealism

The analyses of the mind–world relation offered by transcendental idealists such as Husserl have often been dismissed with the argument that they remain committed to an outdated form of internalism. The first move in this paper will be to argue that there is a tight link between Husserl’s transcendental idealism and what has been called phenomenological externalism, and that Husserl’s endorsement of the former commits him to a version of the latter. Secondly, it will be shown that key elements in Husserl’s transcendental idealism, including his rejection of representationalism and metaphysical realism, is shared with a number of prominent contemporary defenders of an externalist view on the mind. Ultimately, however, it will be suggested that the very alternative between internalism and externalism—an alternative based on the division between inner and outer—might be inapplicable when it comes to phenomenological conceptions of the mind–world relation.     

The over-generalization problem: predicates rigidly signifying the “unnatural”

According to the simple proposal, a predicate is rigid iff it signifies the same property across the different possible worlds. The simple proposal has been claimed to suffer from an over-generalization problem. Assume that one can make sense of predicates signifying properties, and assume that trivialization concerns, to the effect that the notion would cover any predicate whatsoever, can be overcome. Still, the proposal would over-generalize, the worry has it, by covering predicates for artifactual, social, or evaluative properties, such as ‘is a knife,’ ‘is a bachelor,’ or ‘is funny.’ In defense, it is argued that rigidity for predicates as characterized plays the appropriate theoretical role, and that the contention that “unnatural” properties are not to be rigidly signified is ungrounded.     

班级生态系统对儿童亲社会行为影响的研究述评

依据生态系统观以及班级环境中亲社会行为研究的进展,在班级环境中,与儿童人际互动最密切,对其亲社会行为具有重要影响的两类人群是——同伴和教师。作者把儿童与同伴、儿童与教师之间的互动关系作为班级环境中两个重要生态子系统,依次介绍了班级环境中这两个生态子系统的各成分,以及它们对儿童亲社会行为的影响。文章最后指出,该领域的研究应注重人际间的双向互动、基于观察的互动模式研究、以及重视时间变量对行为过程的影响     

The developmental course of lexical tone perception in the first year of life

Perceptual reorganisation of infants' speech perception has been found from 6 months for consonants and earlier for vowels. Recently, similar reorganisation has been found for lexical tone between 6 and 9 months of age. Given that there is a close relationship between vowels and tones, this study investigates whether the perceptual reorganisation for tone begins earlier than 6 months. Non-tone language English and French infants were tested with the Thai low vs. rising lexical tone contrast, using the stimulus alternating preference procedure. Four- and 6-month-old infants discriminated the lexical tones, and there was no decline in discrimination performance across these ages. However, 9-month-olds failed to discriminate the lexical tones. This particular pattern of decline in nonnative tone discrimination over age indicates that perceptual reorganisation for tone does not parallel the developmentally prior decline observed in vowel perception. The findings converge with previous developmental cross-language findings on tone perception in English-language infants [Mattock, K., & Burnham, D. (2006). Chinese and English infants' tone perception: Evidence for perceptual reorganization. Infancy, 10(3)], and extend them by showing similar perceptual reorganisation for non-tone language infants learning rhythmically different non-tone languages (English and French).     

Ill-structured measurement designs in organizational research: implications for estimating interrater reliability

Organizational research and practice involving ratings are rife with what the authors term ill-structured measurement designs (ISMDs)--designs in which raters and ratees are neither fully crossed nor nested. This article explores the implications of ISMDs for estimating interrater reliability. The authors first provide a mock example that illustrates potential problems that ISMDs create for common reliability estimators (e.g., Pearson correlations, intraclass correlations). Next, the authors propose an alternative reliability estimator--G(q,k)--that resolves problems with traditional estimators and is equally appropriate for crossed, nested, and ill-structured designs. By using Monte Carlo simulation, the authors evaluate the accuracy of traditional reliability estimators compared with that of G(q,k) for ratings arising from ISMDs. Regardless of condition, G(q,k) yielded estimates as precise or more precise than those of traditional estimators. The advantage of G(q,k) over the traditional estimators became more pronounced with increases in the (a) overlap between the sets of raters that rated each ratee and (b) ratio of rater main effect variance to true score variance. Discussion focuses on implications of this work for organizational research and practice.