Conditioned and unconditioned fear organized in the periaqueductal gray are differentially sensitive to injections of muscimol into amygdaloid nuclei

The lateral and basolateral nuclei of the amygdala (LaA and BLA, respectively) serve as a filter for unconditioned and conditioned aversive information that ascends to higher structures from the brainstem, whereas the central nucleus of the amygdala (CeA) is considered to be the main output for the defense reaction. It has been shown that the dorsal periaqueductal gray (dPAG) is activated by threatening stimuli and has important functional links with the amygdala through two-way anatomical connections. In this work, we examined the influence of chemical inactivation of these nuclei of amygdala on the freezing and escape responses induced by electrical stimulation through electrodes implanted in the dPAG of Wistar rats. Each rat also bore a cannula implanted in the LaA, BLA or CeA for injections of muscimol (0.5 microg/0.5 microL) or its vehicle. The duration of freezing behavior that outlasts electrical stimulation of the dPAG was also measured. On the following day, these animals were submitted to a contextual fear-conditioning using foot shocks as unconditioned stimulus. Conditioned freezing to contextual cues previously associated with foot shocks was also inhibited by injections of muscimol into these amygdaloid nuclei. The contextual conditioned freezing behavior is generated in the neural circuits of conditioned fear in the amygdala. The data obtained also show that injections of muscimol into the three amygdaloid nuclei did not change the aversive threshold of freezing, but disrupted the dPAG post-stimulation freezing. Previous findings that the latter freezing results directly from dPAG stimulation and that it is not sensitive to a context shift suggest that it is unconditioned in nature. Thus, the amygdala can affect some, but not all, aspects of unconditioned freezing. Post-stimulation freezing may reflect the process of transferring aversive information from dPAG to higher brain structures.     

"It's magic!" The effects of presentation modality on children's event memory, suggestibility, and confidence judgments

The current study investigated the influence of presentation modality (live, video, and slide show) on children's memory, suggestibility, recognition, and metamemorial monitoring processes. A total of 270 children in three age groups (5- and 6-year-olds, 7- and 8-year-olds, and 9- and 10-year-olds) watched a magic show and were questioned about it 1 week later. The live show yielded more correct answers to nonleading questions, higher resistance to misleading questions, and better recognition memory than did the video condition, which in turn resulted in better performance than did the slide show. Although presentation modality raised the general level of memory performance, the effects were equally strong in all age groups and did not affect memory phenomena such as the size of the misinformation effect and confidence judgments.     

Hostility, anger, aggressiveness, and coronary heart disease: an interpersonal perspective on personality, emotion, and health

The related traits of hostility, anger, and aggressiveness have long been suggested as risk factors for coronary heart disease (CHD). Our prior review of this literature (Smith, 1992) found both considerable evidence in support of this hypothesis and important limitations that precluded firm conclusions. In the present review, we discuss recent research on the assessment of these traits, their association with CHD and longevity, and mechanisms possibly underlying the association. In doing so, we illustrate the value of the interpersonal tradition in personality psychology (Sullivan, 1953; Leary, 1957; Carson, 1969; Kiesler, 1996) for not only research on the health consequences of hostility, anger, and aggressiveness, but also for the general study of the effects of emotion, personality and other psychosocial characteristics on physical health.     

Lack of the metabotropic glutamate receptor subtype 7 selectively modulates Theta rhythm and working memory

Metabotropic glutamate receptors (mGluRs) are known to play a role in synaptic plasticity and learning. We have previously shown that mGluR7 deletion in mice produces a selective working memory (WM) impairment, while other types of memory such as reference memory remain unaffected. Since WM has been associated with Theta activity (6-12 Hz) in EEGs, and since EEG abnormalities have been observed in these mice before, we studied the effect of mGluR7 gene ablation on EEG activity in the hippocampus, in particular in the Theta range, during performance of a WM task. In an eight-arm maze with four arms baited, mGluR7 knock-out (KO) and wild-type mice committed the same number of reference memory errors, whereas KOs committed more WM errors. While performing the task, KO mice showed substantially higher Theta amplitudes, and the ratio of Theta to overall EEG power was much increased. No change was seen in the Delta (0-5 Hz), or Gamma (30-40 Hz) EEG bands compared with controls. When recording EEGs during periods of rest in the home cages, no difference was seen between groups. These findings suggest that mGluR7 is important for modulation and control of Theta activity. Since only WM was affected, and only the Theta range of EEG activity was altered, these results show a correlation between Theta rhythm and WM performance, and therefore support the concept that Theta activity in the hippocampus is involved in WM storage.     

Analysis of response repetition as an error-correction strategy during sight-word reading

A great deal is known about the effects of positive reinforcement on response acquisition; by contrast, much less research has been conducted on contingencies applied to errors. We examined the effects of response repetition as an error-correction procedure on the sight-word reading performance of 11 adults with developmental disabilities. Study 1 compared single-response (SR) repetition and multiple-response (MR) repetition, and results showed that all 6 participants acquired more sight words with the MR procedure. Study 2 compared MR error correction following every incorrect response (continuous) and following one third of incorrect responses (intermittent), and results showed that all 6 participants acquired more sight words when error correction was continuous. Study 3 compared MR error correction in which errors required practice of the training word (relevant) versus a different word (irrelevant), and results showed that 3 of 9 participants showed better performance under the relevant condition; however, all participants showed improvement even under the irrelevant condition. Findings are discussed in terms of the behavioral processes by which error correction may enhance performance during acquisition.     

Context effects: the proportional difference model and the reflection of preference

The reflection effect (D. Kahneman & A. Tversky, 1979) was investigated using the stochastic model of choice developed by C. Gonzalez-Vallejo (2002). The model assumes that individuals make trade-offs among attribute values by relying on a difference variable. The model also specifies a threshold representing individual proclivities to reach to attribute differences. Two experiments demonstrated that changes in risk attitudes, from a gain to a loss situation, depended on the stimuli as well as on individuals' thresholds. Thresholds were generally lower in losses than in gains, indicating a risk-taking tendency. Thresholds were also lower when participants were endowed with greater savings. Model testing revealed better fits for the stochastic model than cumulative prospect theory (A. Tversky &. D. Kahneman, 1992).     

Measuring the perceptual magnet effect in the perception of /i/ by German listeners

In a study of the internal category structure of the vowel /i/, Kuhl found a “perceptual magnet effect”: Discrimination sensitivity was poorer for category instances that were acoustically similar to the category prototype than it was for category instances that were not. The typicality of category exemplars was determined by goodness judgments and was found to correlate with the acoustics of average production. Analysis and interpretation of discrimination performance relied on two important assumptions: that listeners perceived all stimuli presented as exemplars of the same vowel category and that, apart from the influence of phonetic coding, discrimination sensitivity was the same across the investigated part of the vowel space. In the present study, it is shown that production and perception estimates of the category prototype may diverge, possibly because listeners seem to prefer hyperarticulated variants of vowel categories. An approach towards measurement of intra-category discrimination minima is put forward and tested that protects against intercategory confounds and avoids the isosensitivity assumption. Received: 26 November 1997 / Accepted: 25 May 1998     

Relevance of multicultural training to students' applications to clinical psychology programs

Interest in the efficacy of multicultural training for practitioners and scientists working with multicultural populations has led to questions about the characteristics of students who seek this training. Students of ethnic minority background, as compared with White students, may be more likely to seek programs that offer this training, and their ethnic or racial identity may be related to this preference. This study explores the relevance of multicultural training to White and ethnic minority graduate students in accredited clinical psychology programs. Students rated the relevance of multicultural and general training components to their decisions about where to apply to graduate school. The ethnic minority students' mean ratings of the relevance of multicultural components were higher than those of White students, and the degree of ethnic minority students' ethnic identification was positively correlated to these relevance ratings.