Tuberculosis detection by giant african pouched rats

In recent years, operant discrimination training procedures have been used to teach giant African pouched rats to detect tuberculosis (TB) in human sputum samples. This article summarizes how the rats are trained and used operationally, as well as their performance in studies published to date. Available data suggest that pouched rats, which can evaluate many samples quickly, are sufficiently accurate in detecting TB to merit further investigation as a diagnostic tool.     

Novel n-back spatial working memory task using eye movement response

We created a novel eye movement version of the n-back task to measure spatial working memory (WM). Rather than one continuous trial, discrete trials were presented in order to develop a simpler WM task. In Experiment 1, we varied the visibility of the final stimulus to maximize the difference in performance between 0-back and 1-back tasks (WM effect). In Experiment 2, we administered the optimized task to children. In Experiment 3, we further simplified the task. Both adults and children easily completed our task, displaying significant WM effects. Further, similar WM effects were obtained in our original and simplified n-back spatial WM tasks, demonstrating flexibility. Because WM deficits are often an early feature of disease and a marker of disease progression, our saccadic measure of spatial WM may be particularly useful in hard-to-test populations, such as patients and children, and may have application in brain-imaging studies that require discrete trials.     

Longitudinal stability of temperamental exuberance and social-emotional outcomes in early childhood

The goals of the current study were to investigate the stability of temperamental exuberance across infancy and toddlerhood and to examine the associations between exuberance and social-emotional outcomes in early childhood. The sample consisted of 291 4-month-olds followed at 9, 24, and 36 months and again at 5 years of age. Behavioral measures of exuberance were collected at 9, 24, and 36 months. At 36 months, frontal electroencephalogram (EEG) asymmetry was assessed. At 5 years, maternal reports of temperament and behavior problems were collected, as were observational measures of social behavior during an interaction with an unfamiliar peer in the laboratory. Latent profile analysis revealed a high, stable exuberance profile that was associated with greater ratings of 5-year externalizing behavior and surgency, as well as observed disruptive behavior and social competence with unfamiliar peers. These associations were particularly true for children who displayed left frontal EEG asymmetry. Multiple factors supported an approach bias for exuberant temperament but did not differentiate between adaptive and maladaptive social-emotional outcomes at 5 years of age.     

A Clinical Model in Action in Intensive Residential Treatment: Meeting the Needs of Adolescent Boys who have Experienced Domestic Violence

The Habitat Program at Wood’s Homes, Calgary, Alberta, is an eight bed residential treatment program for conduct-disordered youth who have been exposed or subjected to high levels of violence in their family home. The program was based on the assumption that working effectively with such youth requires consideration of the background experiences of family violence, yet traditional treatment models often ignore or minimize the importance of these experiences. We present a clinical model which incorporates aspects of milieu treatment, relationship-based daily interventions and elements of Jenkins’ invitational approach to working with men and boys who use violence as well as Wade’s response-based approach to counseling with victims and perpetrators of violence. The model also incorporates ideas based on Maruna’s research into recidivism and excuse-making. The purpose of the model is twofold: to be broad enough to structure an overall treatment strategy based on the assumption that successful treatment results from the cumulative effect of many interactions over time, and to be specific enough to guide staff in developing strategies for specific situations that typically arise in daily interaction with the youth. We use a case example format to illustrate how staff has utilized the model to engage youth in exploring both their experiences of violence in the family home and in developing new ways of thinking and talking about behavioural choices.     

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.     

Adding fear to conflict: A general purpose cognitive control network is modulated by trait anxiety

Studies of cognitive control show that the dorsal anterior cingulate cortex (dACC) and dorsolateral prefrontal cortex are involved in the detection and resolution of cognitive conflict. However, the neural and behavioral mechanisms underlying emotional interference effects are less consistent. We used fMRI during emotional and nonemotional versions of a facial Stroop task to investigate the effects of emotional stimuli on cognitive control. In the full group there was limited evidence that different prefrontal circuits manage conflict arising from emotional and nonemotional distractors. However, individual differences in trait anxiety affected both behavioral performance and neural activity during the emotional task. Relative to low-anxiety (LA) subjects, high-anxiety (HA) subjects showed greater amygdala activity to task-relevant emotional information and impaired performance and greater conflict-related activity in the dACC when emotional content was task-irrelevant. Only LA subjects activated rostral ACC during the emotional task. This is consistent with cognitive models of individual differences that hypothesize deficient control of task-irrelevant emotional information in HA subjects. Additional behavioral and fMRI results from this study may be downloaded from http://cabn.psychonomic-journals .org/content/supplemental.     

Punishing hubris: the perils of overestimating one's status in a group

Individuals engage in status self-enhancement when they form an overly positive perception of their status in a group. We argue that status self-enhancement incurs social costs and, therefore, most individuals perceive their status accurately. In contrast, theories of positive illusions suggest status self-enhancement is beneficial for the individual and that most individuals overestimate their status. We found supportive evidence for our hypotheses in a social relations analysis of laboratory groups, an experiment that manipulated status self-enhancement, and a study of real-world groups. Individuals who engaged in status self-enhancement were liked less by others and paid less for their work. Moreover, individuals tended to perceive their status highly accurately. Mediation analyses showed that status self-enhancers were socially punished because they were seen as disruptive to group processes.     

Predictors of maternal language to infants during a picture book task in the home: Family SES, child characteristics and the parenting environment

This study investigated the contribution of child characteristics and parenting environment to the relationship between family SES/demographic characteristics and maternal language to infants. 1157 children were drawn from a representative sample of 1292 infants born to mothers in rural Appalachian counties and rural counties in southern minority U.S. communities. Mothers and their 6–8 month old babies were videotaped at home while talking about a wordless picture book. Mothers' language output and complexity were analyzed. Child temperament, age, and parenting environment (knowledge of child development and observed mother–child engagement) were predictors of maternal language. Furthermore, their inclusion reduced the magnitude of the association between demographic characteristics and maternal language. Tests of mediation suggested that the parenting environment partially mediates the relationship between SES/demographic characteristics and maternal language. Findings are discussed with respect to identifying proximal processes that explain how SES may exert its influence on the language of young children.     

Does performance on the standard antisaccade task meet the co-familiality criterion for an endophenotype?

The “co-familiality” criterion for an endophenotype has two requirements: (1) clinically unaffected relatives as a group should show both a shift in mean performance and an increase in variance compared with controls; (2) performance scores should be heritable. Performance on the antisaccade task is one of several candidate endophenotypes for schizophrenia. In this paper we examine whether the various measures of performance on the standard version of the antisaccade task meet the co-familiality criterion for an endophenotype. The three measures of performance—reflexive saccade errors, latency of correct antisaccades, and gain—show a wide range of effect sizes and variance ratios as well as evidence of significant or near significant heterogeneity. The estimated mean effect sizes [Cohen’s d: error rate: 0.34 (SD: 0.29); latency: 0.33 (SD: 0.30); gain: 0.54 (SD: 0.38)] are significantly greater than 0, but the magnitude of the departures from 0 is relatively small, corresponding to modest effect sizes. The width of the 95% confidence intervals for the estimated effect sizes (error rate: 0.2–0.49; latency: 0.17–0.50; gain: 0.23–0.85) and the coefficients of variation in effect sizes (error rate: 85.3%; latency: 90.9%; gain: 68.4%) reflect heterogeneity in effect sizes. The effect sizes for error rate showed statistically significant heterogeneity and those for latency (P = .07) and gain (P = .09) showed a trend toward heterogeneity. These results indicate that the effect sizes are not consistent with a single mean and that the average effect size may be a biased estimate of the magnitude of differences in performance between relatives of schizophrenics and controls. Relatives of schizophrenics show a small but significant increase in variance in error rate, but the confidence interval is broad, perhaps reflecting the heterogeneity in effect size. The variance ratios for latency and gain did not differ in relatives of schizophrenics and controls. Performance, as measured by error rate, is moderately heritable. The data do not provide compelling support for a consistent shift in mean or variance in relatives of schizophrenia patients compared with nonpsychiatric controls, both of which are required for a major gene involved in co-familial transmission. This set of findings suggests that although intra-familial resemblance in antisaccade performance is due in part to genetic factors, it may not be related to a schizophrenia genotype. Based on the current literature, it would be premature to conclude that any of the measures of antisaccade performance unambiguously meets the co-familiality criterion for an endophenotype.     

Truthmakers and necessary connections

In this paper I examine the objection to truthmaker theory, forcibly made by David Lewis and endorsed by many, that it violates the Humean denial of necessary connections between distinct existences. In Sect. 1 I present the argument that acceptance of truthmakers commits us to necessary connections. In Sect. 2 I examine Lewis’ ‘Things-qua-truthmakers’ theory which attempts to give truthmakers without such a commitment, and find it wanting. In Sects. 3–5 I discuss various formulations of the denial of necessary connections and argue that each of them is either false or compatible with truthmaker theory. In Sect. 6 I show how the truthmaker theorist can resist the charge that they are committed to necessary exclusions between possible existents. I conclude that there is no good objection to truthmaker theory on the grounds that it violates the Humean dictum.