Drug discrimination under concurrent variable-ratio variable-ratio schedules

Pigeons were trained to discriminate 5 mg/kg pentobarbital from saline under concurrent variable-ratio (VR) VR schedules, in which responses on the pentobarbital-biased lever were reinforced under the VR schedule with the smaller response requirements when pentobarbital was given before the session, and responses on the saline-biased key were reinforced under the VR schedule with the larger response requirements. When saline was administered before the session, the reinforcement contingencies associated with the two response keys were reversed. When responding stabilized under concurrent VR 20 VR 30, concurrent VR 10 VR 40, or concurrent VR 5 VR 50 schedules, pigeons responded almost exclusively on the key on which fewer responses were required to produce the reinforcer. When other doses of pentobarbital and other drugs were substituted for the training dose, low doses of all drugs produced responding on the saline-biased key. Higher doses of pentobarbital and chlordiazepoxide produced responding only on the pentobarbital-biased key, whereas higher doses of ethanol and phencyclidine produced responding only on this key less often. d-Amphetamine produced responding primarily on the saline-biased key. When drugs generalized to pentobarbital, the shape of the generalization curve under concurrent VR VR schedules was more often graded than quantal in shape. Thus, drug discrimination can be established under concurrent VR VR schedules, but the shapes of drug-discrimination dose-response curves under concurrent VR VR schedules more closely resemble those seen under interval schedules than those seen under fixed-ratio schedules. Graded dose-response curves under concurrent VR VR schedules may relate to probability matching and difficulty in discriminating differences in reinforcement frequency.     

Sentence processing strategies in healthy seniors with poor comprehension: an fMRI study

We used fMRI to examine patterns of brain recruitment in 22 healthy seniors, half of whom had selective comprehension difficulty for grammatically complex sentences. We found significantly reduced recruitment of left posterolateral temporal [Brodmann area (BA) 22/21] and left inferior frontal (BA 44/6) cortex in poor comprehenders compared to the healthy seniors with good sentence comprehension, cortical regions previously associated with language comprehension and verbal working memory, respectively. The poor comprehenders demonstrated increased activation of left prefrontal (BA 9/46), right dorsal inferior frontal (BA 44/6), and left posterior cingulate (BA 31/23) cortices for the grammatically simpler sentences that they understood. We hypothesize that these brain regions support an alternate, nongrammatical strategy for processing complex configurations of symbolic information. Moreover, these observations emphasize the crucial role of the left perisylvian network for grammatically guided sentence processing in subjects with good comprehension.     

共享概念的性质对拥有关系句子情景模型建立的影响

应用扇效应技术探讨共享概念的性质对建构拥有关系情境模型的影响。共包括2个实验,探讨在将“多人买1物”句式中的所购“物品”改变为隐含共同地点信息的“物品”条件下,被试对“多人买1物”拥有行为句式的学习是否表现出扇效应。结果表明,当所购物品隐含的相同地点信息的情况下,“多人买1物”的拥有行为句式无论是否具有明确的地点状语,都如同“1人买多物”的句式一样,没有表现出扇效应,与Radvanskv的研究结果不同。据此认为,只有在共享概念是属于情景模型建构的维度信息的情况下,有共享概念的信息才能整合为同一个情景模型。     

Immediate-early Fos protein levels in brainstem neurons of male and female gonadectomized mice subjected to cold exposure

The expression of the immediate early gene c-fos has been used extensively as a marker for neural activation in response to acute and chronic stressful stimuli in brain and spinal cord. The present study examined the expression of Fos protein in the brainstem nuclei of male and female gonadectomized mice in response to cold stress. Free-floating sections were processed immunohistochemically for Fos protein using standard avidin-biotin complex methods. The number of Fos-positive neurons in each nucleus was determined. Although the experiment was designed to look for gender differences, results were equivalent between females and males. After mice were exposed to a cold ambient temperature (4 degrees C) for 2 h, elevated numbers of Fos-positive neurons were counted in the medullary gigantocellular reticular nucleus, medullary raphe nucleus, nucleus of the solitary tract and in locus coeruleus. However, no elevated expression was found in nucleus ambiguus, nor in neurons of the A1 group, nor the C2 or C3 group. Similar to rats, these results with mice reveal a widespread arousal system in the lower brainstem activated by cold stress in both genders. These findings in gonadectomized mice have set the stage for investigations following hormonal and genetic manipulations.     

中国幼儿数数过程信息加工活动研究

探讨中国幼儿数数发展特点。实验1探讨3－5岁幼儿数数的终结点分布状况,结果表明,最大的密集终结点是“19”。实验2进一步考察幼儿在其数数范围内与范围外的起点进行数数的成绩,结果表明,数数范围为11－19的幼儿就开始有部分人可以在其数数范围外的起点进行数数,此表明他们开始应用了数列规则。据此可以认为,中国幼儿的数数活动同样包括联结学习与数列规则学习两种信息加工活动,但中国幼儿数列规则的学习活动在“11－19”数数过程开始。     

Examination of relationships among trait-like individual differences, state-like individual differences, and learning performance

Several authors (e.g., J.T. Austin & H.J. Klein, 1996; R. Kanfer, 1990b, 1992) have urged researchers to examine comprehensive models of distal individual differences as predictors of proximal motivational processes and performance. Two field studies in an academic setting tested a model of relationships among trait-like individual differences (cognitive ability, general self-efficacy, and goal orientation), state-like individual differences (state anxiety, task-specific self-efficacy, and goals), and learning performance. Most hypothesized relationships among these constructs received support when tested on 2 samples, when examining different performance episodes, and when using different goal orientation and state-anxiety measures. In general, state-like individual differences were found to mediate the relationships between trait-like individual differences and learning performance. Implications of these results are discussed and suggestions for future research are provided.     

Effects of antecedent order and semantic context on Chinese pronoun resolution

Three reading time experiments were conducted in order to examine the relative contributions of order of antecedents and semantic context to the resolution of temporarily ambiguous Chinese pronouns. These pronouns were ambiguous because each of them was preceded by two antecedents, both of which were likely candidates for coreference. The identity of the pronoun was revealed by subsequent disambiguating information that constrained the pronoun to one particular interpretation. Experiment 1 showed that reading of the disambiguating phrase was slower when the phrase confined the pronoun to the second rather than to the first antecedent. Experiment 2 produced the same effect of antecedent order (first vs. second antecedent) regardless of whether the target antecedent was an action-performing or an action-receiving entity. In Experiment 3, the order effect was eliminated by a biasing modifier inserted immediately before the pronoun. These results indicate that in a semantically neutral environment, the first-appearing antecedent is the preferred candidate for coreferencing the ambiguous Chinese pronoun. The interaction between order of antecedents and semantic context (in the form of preposed biasing modifiers) suggests that the initial comprehension of Chinese pronouns depends as much on contextual as on structural factors.     

Evaluating gene x psychological risk factor effects in the pathogenesis of anxiety: a new model approach

The present study evaluated the singular and interactive effects of a functional polymorphism (variation) in the serotonin transporter (5-HTT) gene and a psychological trait (anxiety sensitivity [AS], i.e., fear of arousal symptoms) in predicting subjective and physiological responses to a 35% carbon dioxide (CO2) challenge in a community sample (N = 72). Genotypes were divided into 2 groups in accord with prior research. Findings were partially supportive of the hypothesized risk model. These indicated that the Group L genotype (homozygous for the 1 allele), compared with the Group S genotype (homozygous for the s allele plus heterozygous individuals), predicted greater fearful response to the biological challenge. There was also an AS x Genotype interaction predicting heart rate variability (HRV) in response to the CO2, suggesting that high AS plus Group L status predicts decreased HRV.     

The role of inhibition in the regulation of sequential action

We investigated the regulation of sequential action using a new paradigm. Participants learned a sequence of seven stimulus categories and then monitored for them during successive displays. All displays were instances of these categories, presented in pseudorandom order. On each trial, participants monitored for an instance of Category 1, pressed a key on a computer keyboard, then monitored for an instance of Category 2, pressed a key on the keyboard, and so on for all seven categories. Thus, a perfect trial contained exactly seven responses. Intrusion errors were classified as a function of ordinal distance from the current serial position ( n ). Fewer intrusion errors were made at near serial positions than at far ones, suggesting a gradient of lateral inhibition. In addition, more intrusions were made on n + 1 categories than n − 1 categories, suggesting greater availability of intended than completed goals. In accord with current models of sequential action, the results indicate lateral and self-inhibition as important mechanisms in regulation of sequential action.     

A multilevel examination of the relationships among training outcomes, mediating regulatory processes, and adaptive performance

This study examined whether cognitive, affective-motivational, and behavioral training outcomes relate to posttraining regulatory processes and adaptive performance similarly at the individual and team levels of analysis. Longitudinal data were collected from 156 individuals composing 78 teams who were trained on and then performed a simulated flight task. Results showed that posttraining regulation processes related similarly to adaptive performance across levels. Also, regulation processes fully mediated the influences of self- and collective efficacy beliefs on individual and team adaptive performance. Finally, knowledge and skill more strongly and directly related to adaptive performance at the individual than the team level of analysis. Implications to theory and practice, limitations, and future directions are discussed.