Influence of chronic corticosterone and glucocorticoid receptor antagonism in the amygdala on fear conditioning

Glucocorticoid receptor activation within the basolateral amygdala (BLA) during fear conditioning may mediate enhancement in rats chronically exposed to stress levels of corticosterone. Male Sprague-Dawley rats received corticosterone (400 microg/ml) in their drinking water (days 1-21), a manipulation that was previously shown to cause hippocampal CA3 dendritic retraction. Subsequently, rats were adapted to the fear conditioning chamber (day 22), then trained (day 23), and tested for conditioned fear to context and tone (day 25). Training consisted of two tone (20s) and footshock (500 ms, 0.25 mA) pairings. In Experiment 1, muscimol (4.4 nmol/0.5 microl/side), a GABAergic agonist, was microinfused to temporarily inactivate the BLA during training. Rats given chronic corticosterone showed enhanced freezing to context, but not tone, compared to vehicle-supplemented rats. Moreover, BLA inactivation impaired contextual and tone conditioning, regardless of corticosterone treatment. In Experiment 2, RU486 (0, 0.3, and 3.0 ng/0.2 microl/side) was infused on training day to antagonize glucocorticoid receptors in the BLA. Corticosterone treatment enhanced fear conditioning to context and tone when analyzed together, but not separately. Moreover, RU486 (3.0 ng/side) selectively exacerbated freezing to context in chronic corticosterone-exposed rats only, but failed to alter tone conditioning. Serum corticosterone levels were negatively correlated with contextual, not tone, conditioning. Altogether, these suggest that chronic corticosterone influences fear conditioning differently than chronic stress as shown previously. Moreover, chronic exposure to corticosteroids alters BLA functioning in a non-linear fashion and that contextual conditioning is influenced more than tone conditioning by chronic corticosterone and BLA glucocorticoid receptor stimulation.     

Parallel processing across neural systems: implications for a multiple memory system hypothesis

A common conceptualization of the organization of memory systems in brain is that different types of memory are mediated by distinct neural systems. Strong support for this view comes from studies that show double (or triple) dissociations between spatial, response, and emotional memories following selective lesions of hippocampus, striatum, and the amygdala. Here, we examine the extent to which hippocampal and striatal neural activity patterns support the multiple memory systems view. A comparison is made between hippocampal and striatal neural correlates with behavior during asymptotic performance of spatial and response maze tasks. Location- (or place), movement, and reward-specific firing patterns were found in both structures regardless of the task demands. Many, but not all, place fields of hippocampal and striatal neurons were similarly affected by changes in the visual and reward context regardless of the cognitive demands. Also, many, but not all, hippocampal and striatal movement-sensitive neurons showed significant changes in their behavioral correlates after a change in visual context, irrespective of cognitive strategy. Similar partial reorganization was observed following manipulations of the reward condition for cells recorded from both structures, again regardless of task. Assuming that representations that persist across context changes reflect learned information, we make the following conclusions. First, the consistent pattern of partial reorganization supports a view that the analysis of spatial, response, and reinforcement information is accomplished via an error-driven, or match-mismatch, algorithm across neural systems. Second, task-relevant processing occurs continuously within hippocampus and striatum regardless of the cognitive demands of the task. Third, given the high degree of parallel processing across allegedly different memory systems, we propose that different neural systems may effectively compete for control of a behavioral expression system. The strength of the influence of any one neural system on behavioral output is likely modulated by factors such as motivation, experience, or hormone status.     

Coordination of multiple memory systems

On the basis of lesions of different brain areas, several neural systems appear to be important for processing information regarding different types of learning and memory. This paper examines the development of pharmacological and neurochemical approaches to multiple memory systems from past studies of modulation of memory formation. The findings suggest that peripheral neuroendocrine mechanisms that regulate memory processing may target their actions toward those neural systems most engaged in the processing of learning and memory. In addition, measurements of acetylcholine release in different memory systems reveals extensive interactions between memory systems, some cooperative and some competitive. These results imply that many neural systems, often characterized as relatively independent, may in fact interact extensively, blurring the dependencies of different memory tasks on specific neural systems.     

Comparative and categorical spatial judgments in the monkey: “high” and “low”

Adult human subjects can classify the height of an object as belonging to either of the high or low categories by utilizing an abstract concept of midline that divides the vertical dimension into two halves. Children lack this abstract concept of midline, do not have a sense that these categories are directional opposites, and their categorical and comparative usages of high(er) or low(er) are restricted to the corresponding poles. We investigated the abilities of a rhesus monkey to perform categorical judgments in space. We were also interested in the presence of the congruity effect (a decrease in response time when the objects compared are closer to the category pole) in the monkey. The presence of this phenomenon in the monkey would allow us to relate the behavior of the animal to the two major competing hypotheses that have been suggested to explain the congruity effect in humans: the analog and semantic models. The monkey was trained in delayed match-to-sample tasks in which it had to categorize objects as belonging to either a high or low category. The monkey was able to generate an abstract notion of midline in a fashion similar to that of adult human subjects. The congruity effect was also present in the monkey. These findings, taken together with the notion that monkeys are not considered to think in propositional terms, may favor an analog comparison model in the monkey.     

Object localisation and frames of reference

In this paper, we explore which spatial frames of reference, egocentric or allocentric, are used to locate objects either in relation to ourselves (i.e. subject-to-object localisation) or to other objects (i.e. object-to-object localisation). In particular, we wanted to know whether the same or different frames of reference are used in these two different kinds of localisation after learning the environment in an egocentric way. Egocentric frames of reference are determined by the position of the person in relation to the spatial layout, whereas allocentric frames of reference are centred on the environment or on objects, independent of a persons position. We hypothesised that subject-to-object localisation is based on egocentric spatial representations, whereas object-to-object localisation is based on allocentric spatial representations. Participants were asked to study eight common objects, placed in a circle. Next, half of the participants had to point to an object in relation to their imagined position (egocentric condition) and the other half to an object in relation to another object (allocentric condition). The overall results show no difference between subject-to-object and object-to-object localisation. In both cases, access to positions corresponding to the front/back body axis was facilitated, in terms of both latency and error. Moreover, participants were able to retrieve objects positions better from the perspective from which they had learned the spatial array than from new perspectives. These results support the conclusion that egocentric coordinates, which are selected on the basis of our body-centred experience of the environment, define spatial representations underlying both subject-to-object and object-to-object localisation.     

Children's use of geometric information in mapping tasks

Accumulating evidence, particularly from research using the disorientation technique, demonstrates early sensitivity to geometric properties of space. However, it is not known whether children can use geometric cues to interpret a map. The current study examined how 3- to 6-year-olds use geometric features of layouts in solving mapping tasks. Children were asked to identify a target location in a layout shaped as an isosceles triangle by using information provided in a picture of that layout. Performance depended on whether the shape was presented explicitly or needed to be inferred. Younger participants performed better when the triangle was formed by continuous connected lines than when it was formed by separate objects. Performance also depended on the type of geometric cues available. Children found it easier to establish mapping for targets located in the unique corner of the triangle than for targets located in equal-sized corners. Overall, the findings reveal both a remarkable early ability to use geometric information in mapping and limits in this ability.     

Grief Ministry as Homecoming: Framing Death from a Korean-American Perspective

Using the personal experience of a “homecoming” funerary journey from the U.S. to Korea, the author probes the cultural construction of familial bonds between the living and the dead in Korean and biblical (Genesis) funeral narratives. This article highlights the cultural differences between American and Korean funeral traditions — that is, (1) dying at a hospital vs. dying at home, (2) embalming vs. sup/yom (washing/binding of the corpse), (3) metal casket vs. wooden coffin, (4) committal vs. banhon (returning of the spirit) – to explore the religious and practical implications of the multicultural grieving process for pastoral care and grief ministry in which death is conceived as returning to the familial, cultural, and spiritual homes.

Child-Directed Interaction: Prediction of Change in Impaired Mother–Child Functioning

The first phase of parent–child interaction therapy (PCIT), called child-directed interaction, teaches parents to use positive and differential social attention to improve the parent–child relationship. This study examined predictors of change in mother and child functioning during the child-directed interaction for 100 mother–child dyads. The children were 3–6-years-old and diagnosed with oppositional defiant disorder. After establishing that significant improvements occurred in mother report of child disruptive behavior, parenting stress, and parenting practices, these three variables were combined to form a latent impaired mother–child functioning construct. Structural equation models were examined using maternal demographic and psychosocial variables as predictors of impaired mother–child functioning before and after the child-directed interaction. Mothers’ self-reported daily hassles and depressive symptomatology predicted 74% of variance in impaired mother–child functioning before treatment. Mothers’ report of social support predicted impaired mother–child functioning after the child-directed interaction, with 57% of the variance accounted for in this longitudinal model. These findings suggest the importance of improving maternal social support during the initial phase of PCIT.