Differential effects of predator stress and the antidepressant tianeptine on physiological plasticity in the hippocampus and basolateral amygdala

Stress can profoundly affect memory and alter the functioning of the hippocampus and amygdala. Studies have also shown that the antidepressant tianeptine can block the effects of stress on hippocampal and amygdala morphology and synaptic plasticity. We examined the effects of acute predator stress and tianeptine on long-term potentiation (LTP; induced by 100 pulses in 1 s) and primed burst potentiation (PB; a low threshold form of LTP induced by only five physiologically patterned pulses) in CA1 and in the basolateral nucleus (BLA) of the amygdala in anesthetized rats. Predator stress blocked the induction of PB potentiation in CA1 and enhanced LTP in BLA. Tianeptine blocked the stress-induced suppression of PB potentiation in CA1 without affecting the stress-induced enhancement of LTP in BLA. In addition, tianeptine administered under non-stress conditions enhanced PB potentiation in the hippocampus and LTP in the amygdala. These findings support the hypothesis that acute stress impairs hippocampal functioning and enhances amygdaloid functioning. The work also provides insight into the actions of tianeptine with the finding that it enhanced electrophysiological measures of plasticity in the hippocampus and amygdala under stress, as well as non-stress, conditions.     

The real relationship between short-term memory and working memory

Storage-oriented memory span tasks with no explicit concurrent processing are usually referred as short-term memory (STM) tasks, whereas tasks involving storage plus concurrent processing requirements are designated as working memory (WM) tasks. The present study explores a question that remains unsolved: Do STM and WM tasks clearly tap distinguishable theoretical constructs? For that purpose, a large sample of 403 participants was tested through 12 diverse memory span tasks. Half of those tasks are widely accepted as measures of STM, whereas the other half measure WM. The results show that STM and WM share largely overlapping underlying capacity limitations, suggesting that all memory span tasks tap essentially the same construct. Some implications are discussed.     

A context-specific latent inhibition effect in a human conditioned suppression task

Three studies used a computer video game preparation to demonstrate latent inhibition in adult humans. In all studies participants fired torpedoes at a target spaceship by clicking the mouse. Conditioned stimuli (CSs) were presented in the form of coloured “sensors” at the bottom of the screen. Conditioning was conducted by pairing a sensor with an attack from the target spaceship. Participants learned to suppress their rate of mouse clicking in preparation for an attack. In Experiment 1 a total of 10 preexposures to the sensor CS, prior to conditioning, retarded acquisition of suppression. In Experiment 2 the effect of preexposure was shown to be context specific. Experiment 3 showed little generalization of the preexposure effect from one sensor CS to another. Experiment 3 also showed that preexposure did not make the sensor CS inhibitory. Comparisons with conditioned suppression procedures with animals and negative-priming procedures are briefly discussed.     

Knockdown of Nurr1 in the rat hippocampus: implications to spatial discrimination learning and memory

Nurr1 expression is up-regulated in the brain following associative learning experiences, but its relevance to cognitive processes remains unclear. In these studies, rats initially received bilateral hippocampal infusions of control or antisense oligodeoxynucleotides (ODNs) 1 h prior to training in a holeboard spatial discrimination task. Such pre-training infusions of nurr1 antisense ODNs caused a moderate effect in learning the task and also impaired LTM tested 7 d later. In a second experiment, ODN infusions were given immediately after the animals had received two sessions of training, during which all animals showed normal learning. Although antisense treated rats were significantly impaired during the post-infusion stages of acquisition of the task, no group differences were observed during the LTM test given 7 d later. These animals were subjected 3 d later to reversal training in the same maze in the absence of any additional treatments. Remarkably, rats previously treated with antisense ODNs displayed perseveration: The animals were fixated with the previously learned pattern of baited holes, causing them to be significantly impaired in the extinction of acquired spatial preferences and future learning. We postulate that Nurr1 function in the hippocampus is important for normal cognitive processes.     

Individual differences in anxiety trait are related to spatial learning abilities and hippocampal expression of mineralocorticoid receptors

Although high levels of anxiety might be expected to negatively influence learning and memory, it remains to be shown whether individual differences in anxiety may influence spatial learning and memory in outbred rat populations. We have studied this possibility in male Wistar rats whose levels of anxiety were first characterized as either high (HA) or low (LA) according to their behavior in the elevated plus maze or in the open field test. Subsequently, their performance in the Morris water maze was studied, a task dependent on hippocampal activity. Interestingly, LA rats showed a faster acquisition and better memory in the water maze when compared to HA rats. Indeed, this difference in performance could mainly be attributed to the increase in thigmotactic behavior (swimming in circles close to the maze walls) displayed by HA rats during spatial navigation. Glucocorticoids are known to affect the state of anxiety and the hippocampus is the main target of glucocorticoids in the brain. Hence, we investigated whether the hippocampal expression of the two classical corticosteroid receptors, mineralocorticoid (MR) and glucocorticoid (GR) differed in the two groups of rats. We found that LA rats displayed higher hippocampal expression of MR but not GR than HA rats. Indeed, the expression levels for these receptors were positively correlated with the amount of time spent by the animals in the open arms of the elevated plus maze. Moreover, we present evidence that the levels of anxiety quantified in the first stages of our study constitute a trait rather than a state. Taken together, this study has generated evidence of a close interaction between the anxiety trait, hippocampal MR expression and the learning abilities of individuals in stressful spatial orientation tasks.     

Facial appearance and judgments of credibility: the effects of facial babyishness and age on statement credibility

Researchers have found that facial appearance influences social judgments. For example, evidence has shown that facial babyishness and age affect perceivers' impressions of the stimulus person's veracity. In this experiment, the researchers examined whether these variables also influenced the credibility attributed to written statements purportedly made by these people in addition to several topics of interest in deception-detection research. Undergraduates (N = 270) were presented babyfaced or mature-faced photographs that depicted a child, an adult, or an older individual, in addition to a written truthful or deceptive statement purportedly made by the person in the photograph. Results showed that, as predicted, when the statements were accompanied by babyfaced pictures, participants tended to judge them as truthful, but only if the pictures did not depict children. Also, when the statements were accompanied by childen's pictures, participants tended to judge them as deceptive, but only if the pictures depicted a babyish face. Overall detection accuracy was close to chance and did not correlate with either judgmental confidence or with the respondents' estimated lie-detection accuracy. However, confidence and estimated ability were significantly correlated. Also, more confidence was placed in judgments of truthfulness than in judgments of deceptiveness. Respondents' truth bias and the existence of a veracity effect in the diverse experimental conditions were examined as well.     

Stimulus-response compatibility between stimulated eye and response location: implications for attentional accounts of the Simon effect

One influential theory of the Simon effect, the attention-shift hypothesis, states that attention movements are the origin of spatial stimulus codes. According to this hypothesis, stimulus-response compatibility effects should be absent when attention shifts are prevented. To test this prediction, we used monocular patches of color that required left or right key-press responses. About half of the subjects could discriminate which eye was stimulated (in a subsequent task), and showed strong spatial compatibility effects between the stimulated eye and the response location. The other half of the subjects could not make a utrocular discrimination (i.e., they could not judge which eye had received monocular stimulation), but the pattern of results was the same: the fastest reaction times were observed when the stimulated eye corresponded spatially to the required response (i.e., a Simon effect). Since the subjects presumably did not move their attention (from the subject's point of view, the stimuli were presented centrally), our results indicate that spatial codes can be produced in the absence of attention shifts. These results also show that utrocular discrimination can be assessed via indirect measures that are much more sensitive than explicit measures.     

The conflict cycle in the case of an adolescent in crisis

This is an extension of a previous paper describing a conflict cycle in families and therapy consisting of four steps: (1) the dispute; (2) blaming; (3) shame, guilt, or denial; and (4) reparation, reconciliation, or retaliation. The focus is on a single case of a 15-year-old male with a gender identity disorder in addition to a conduct disorder. He is an adopted child living in a small community in the southern United States. Conflict is illustrated from several perspectives in a single interview with the family and over the length of contact over a nine-month period: (1) between the adolescent and parents, (2) between the adolescent and community, (3) between the parents, and (4) between the Good Self and the Bad Self of the adolescent. The thesis is that the conflict cycle is an organizing principle helpful to therapists working with families to make assessments and plan interventions.This paper is an expanded and edited version of a presentation by the senior author in San Diego, California, on November 12, 1988, at the Western States Conference of the American Society of Adolescent Psychiatry.     

Ecological validity and cultural sensitivity for outcome research: Issues for the cultural adaptation and development of psychosocial treatments with Hispanics

This article has two objectives. The first is to provide a culturally sensitive perspective to treatment outcome research as a resource to augment the ecological validity of treatment research. The relationships between external validity, ecological validity, and culturally sensitive research are reviewed. The second objective is to present a preliminary framework for culturally sensitive interventions that strengthen ecological validity for treatment outcome research. The framework, consisting of eight dimensions of treatment interventions (language, persons, metaphors, content, concepts, goals, methods, and context) can serve as a guide for developing culturally sensitive treatments and adapting existing psychosocial treatments to specific ethnic minority groups. Examples of culturally sensitive elements for each dimension of the intervention are offered. Although the focus of the article is on Hispanic populations, the framework may be valuable to other ethnic and minority groups.