Basolateral amygdala inactivation impairs learned (but not innate) fear response in rats

Numerous studies have suggested that the amygdala is involved in the formation of aversive memories, but the possibility that this structure is merely related to any kind of fear sensation or response could not be ruled out in previous studies. The present study investigated the effects of bilateral inactivation of the amygdaloid complex in rats tested in the plus-maze discriminative avoidance task. This task concomitantly evaluates aversive memory (by discrimination of the two enclosed arms) and innate fear (by open-arm exploration). Wistar rats (3-5 months-old) were implanted with bilateral guide cannulae into basolateral amygdala. After surgery, all subjects were given 1 week to recover before behavioral experiments. Afterwards, in experiment 1, 15 min prior to training, 0.5 μl of saline or muscimol (1 mg/ml) was infused in each side via microinjection needles. In experiment 2 the animals received injections immediately after the training session and in experiment 3 rats were injected prior to testing session (24 h after training). The main results showed that (1) pre-training muscimol prevented memory retention (evaluated by aversive arm exploration in the test session), but did not alter innate fear (evaluated by percent time in open arms); (2) post-training muscimol impaired consolidation, inducing increased percent in aversive arm exploration in the test session and (3) pre-testing muscimol did not affect retrieval (evaluated by aversive enclosed arm exploration in the test session). The results suggest that amygdala inactivation specifically modulated the learning of the aversive task, excluding a possible secondary effect of amygdala inactivation on general fear responses. Additionally, our data corroborate the hypothesis that basolateral amygdala is not the specific site of storage of aversive memories, since retention of the previously learned task was not affected by pre-testing inactivation.     

Pre-training anandamide infusion within the basolateral amygdala impairs plus-maze discriminative avoidance task in rats

Endocannabinoids (eCBs) modulate a variety of brain functions via activation of the widely expressed CB1 receptor. One site of high density of this receptor is the basolateral amygdala (BLA), a structure involved in the formation of aversive memories. The activation and blockade of CB1 receptors by systemic or hippocampal drug administrations have been shown to modify memory processing. However, little is known about the role of the BLA endocannabinoid system in aversive memories. Additionally, BLA endocannabinoid transmission seems to be related to emotional states, but the relevance of these effects to memory formation is still unknown. In this study we investigated the effects of the eCB anandamide (AEA) and the CB1 antagonist/inverse agonist AM251 infused into the BLA on the acquisition of an aversive memory task, concomitantly evaluating basal anxiety levels in rats. Male rats received pre-training micro-injection of AEA, AM251 or vehicle bilaterally into the BLA, and were studied with the plus-maze discriminative avoidance task (a paradigm that allows concomitant and independent evaluation of anxiety-like behavior and the memory of an aversive task). Our results showed that AEA into the BLA before training prevented memory retrieval 24 h later, as evaluated by exploration of the aversive arm of the maze, while AM251 into the BLA did not interfere with animals' performance. In addition, AEA had no effect on anxiety-like behavior (as evaluated by open arm exploration and risk assessment), while AM251 induced an anxiogenic effect. Our data indicate an important role of BLA CB1 receptors in aversive memory formation, and suggest that this involvement is not necessarily related to a possible modulation of anxiety states.     

Ethnicity and Homeownership in Montréal, Toronto and Vancouver: Measuring Effects of the Spatial Distribution of Ethnic Groups Using Multilevel Modeling in 1996 and 2001

This article presents the results of an empirical study on the relationship between the spatial distribution of ethnic groups and their access to homeownership in the three largest Canadian cities. Firstly, we argue, based on former theoretical work, that ethnicity has partly been misleadingly conceptualized in previous research on housing and neighbourhood dynamics. Consequently, we also argue that ethnic affiliation has wrongly been included as an individual trait in previous research, whereas it is a characteristic that needs to be treated as a collective trait. Multilevel modeling is presented here as a helpful way to avoid the limitation of previous research on this specific issue. Secondly, we attempt to test certain hypotheses about the emergence of an “ethnic capital” in metropolitan regions where immigration and cultural diversity are rising. In order to achieve this goal, we estimate the relationship between various dimensions of ethnic segregation and the mean level of ownership. We also try to determine whether the aggregation of ethnic groups in urban space enhances the probability of their members having access to homeownership. Our study provides mixed results in regards to these hypotheses. The “assimilation theory” seems to be applicable in most cases, while some of our results also lead to the conclusion that when ethnic groups with a higher income level are concentrated in space, this can foster their ability to access homeownership.     

The development of intergroup bias in childhood: how social norms can shape children's racial behaviours

The present research examined the developmental course of racial behaviours in childhood. It tested the hypothesis that White children's expressions of racial prejudice do not necessarily decline in middle childhood due to the development of particular cognitive skills but that instead, as argued by the socio-normative approach, children older than seven will go on expressing prejudiced attitudes under appropriate conditions. This would be explained by the presence of an anti-racism norm, along with the existence of values promoting equal rights, which impede blatant expressions of racism. In the first study 283 White children aged 6-7 and 9-10 years performed a task of resource allocation to White and Black target children in conditions of high (White interviewer was present) or low (White interviewer was absent) salience of the anti-racist norm. The 6- to 7-year-old children discriminated against the Black target in both conditions whereas older children discriminated against the Black child only when the anti-racist norm was not salient. In Study 2, 187 White children aged 6-7 and 9-10 years performed the same resource allocation task in conditions of explicit activation of similarity vs dissimilarity or egalitarian vs merit-based norms regarding race relations. Supporting the hypothesis of the role of racist or anti-racist norms on the expression of intergroup discrimination, results have again shown that 6- to 7-year-old children discriminated against the Black target in both conditions while older children presented significantly different prejudiced/nonprejudiced behaviours consistent with the activated norms. These results were discussed in terms of the need for a reanalysis of the assumptions and research results of the cognitive-developmental theory and of further developments in the socio-normative approach regarding the development of prejudice in childhood.     

Three dimensions of coping and a look at their evolutionary origin

Serious problems persist concerning the conceptualization and measurement of the coping construct. This study examines the properties and factor structure of the COPE questionnaire, one of the most widely used instruments to measure coping, in a sample of 471 patients. A series of exploratory factor procedures are applied at the item- and scale-level, and the resulting solutions are tested both by their congruence with previously published structures and by confirmatory techniques. Our finding of three robust, generalizable, and parsimonious second-order dimensions—Engagement, Disengagement, and Help-Seeking—challenges the original structure. The results are discussed from an evolutionary perspective, on the assumption that the recognition of coping as the activation of vestigial defenses may make a substantial contribution to clarifying its functions and organization.     

Numerical estimation in blind subjects: evidence of the impact of blindness and its following experience

Vision was for a long time considered to be essential in the elaboration of the semantic numerical representation. However, early visual deprivation does not seem to preclude the development of a spatial continuum oriented from left to right to represent numbers (J. Castronovo & X. Seron, 2007; D. Szücs & V. Csépe, 2005). The authors investigated the impact of blindness and its following experience on a 3rd property of the mental number line: its obedience to Weber's law. A group of blind subjects and a group of sighted subjects were submitted to 2 numerical estimation tasks: (a) a keypress estimation task and (b) an auditory events estimation task. Blind and sighted subjects' performance obeyed Weber's law. However, blind subjects demonstrated better numerical estimation abilities than did sighted subjects, especially in contexts involving proprioception, indicating the existence of better mapping abilities between the symbolic representations of numbers and their corresponding magnitude representations, obeying Weber's law (e.g., J. S. Lipton & E. Spelke, 2005). These findings suggest that blindness and its following experience with numbers might result in better accuracy in numerical processing.     

Semantic errors reconsidered in the procedural light of stack concepts

The purpose of this paper is to demonstrate the relevance of the stack concept in neuropsycholinguistics, a stack being a file with serially ordered elements. Number names (one, two, three, …) and the names of the days in the week may be viewed in this way. In a stack structure, any element is identified by two pieces of information: the particular stack to which it belongs and its position within that stack. Two experiments are reported that demonstrate a double dissociation. A deep dyslexic patient with agrammatism was found to sort stack elements on the basis of identity of position-within-stacks, while a fluent aphasic with semantic verbal paraphasias used another criterion, grouping together the items of the same stack. First revealed when handling number names, the two psycholinguistic procedures are also shown to be differentially operative with other linguistic material. Introducing the stack concept thus permits a procedural reinterpretation of some “semantic confusions,” particularly but not exclusively those dealing with quantities.     

Correspondence in children's self-report: Tacting and manding aspects

Four boys and 4 girls (3 to 5 years old) played with as many as three toys chosen from a set of six, and were then asked whether they played with each of the toys. After a baseline in which all children showed high levels of correspondence between reported and actual behavior, reports of play were differentially reinforced, first in an individual and then in a social context. Two children in the individual condition began to report play with all six toys, even though no more than three toys had been played with. When reports of play were reinforced in a group context, 5 children reported play with all six toys. When correspondence was subsequently reinforced, virtually complete correspondence returned and was maintained in a third noncontingent reinforcement condition. Correspondence and lack of correspondence were discussed in terms of self-tacting and distorted tacting or manding.