Effects of the interval between exposure to a novel environment and the occurrence of shock on the freezing responses of rats

Rats were exposed to a novel environment (E1) at time T1, given a footshock at time T2, and tested for freezing in E1 or in a second environment (E2). The function relating freezing to the T1-T2 interval among rats tested in E1 was an inverted U-shape. Rats exposed to short T1-T2 intervals displayed just as much freezing in E2 as in E1, whereas rats exposed to longer intervals froze less in E2 than in E1. These differences between the freezing responses in E1 and in E2 were obtained when the T1-T2 intervals were varied, but time spent in the shocked E1 was equated. Rats given two shocks in E1 differentiated between E1 and E2 when the initial shock occurred some time after exposure to E1, but not when the initial shock was presented shortly after that exposure. Rats shocked some time after exposure to E1 on Day 1 and shortly after exposure to that environment on Day 2 differentiated between E1 and E2 more than did rats exposed to the reverse sequence of T1-T2 intervals. The results were attributed to the formation of a network of connections among the E1 cues in rats exposed to moderate or long T1-T2 intervals, and to an impairment in the formation of this network as a result of the conditioning of a subset of cues in rats exposed to short T1-T2 intervals.     

The avian hippocampus and short-term memory for spatial and non-spatial information

Three experiments investigated the role of the pigeon hippocampal formation (the hippocampus and area-parahippocampalis) in short-term memory for non-spatial and spatial information. The acquisition of delayed matching-to-sample and the short-term retention of non-spatial visual information, using a small set of sample stimuli, were unaffected by aspiration lesions of the hippocampus or the neostriatum (Experiment 1). Similarly, acquisition and short-term retention of non-spatial information using a successive, trial-unique, delayed non-matching-to-sample procedure were unaffected by hippocampal damage; the same birds had, however, displayed a profound autoshaping impairment (Experiment 2). Acquisition of a spatial delayed matching-to-sample task was unimpaired by hippocampal damage. However, lesioned animals were impaired following the introduction of retention intervals on this procedure (Experiment 3). The correspondence between the behavioural effects of hippocampal lesions in birds and mammals on short-term memory is discussed, and the implications of these results for avian hippocampal function are considered.     

ASSESSING WOMEN'S FEMINIST IDENTITY DEVELOPMENT Studies of Convergent, Discriminant, and Structural Validity

Researchers have called for increasing sophistication in the assessment of women's feminist identity development (Enns & Hackett, 1990; Hackett, Enns, & Zetzer, 1992) to understand important psychological processes. This series of studies examined recent efforts to operationalize Downing and Roush's (1985) model of feminist identity development. Specifically, the psychometric properties of two existing measures—the Feminist Identity Development Scale (Bargad & Hyde, 1991) and the Feminist Identity Scale (Rickard, 1987)—were examined in two studies with separate samples of women (total N = 486). Results of Study 1 indicated the strengths and significant limitations associated with each scale (e.g., low internal consistency for some subscales, item-subscale inconsistency). A composite measure (derived from these scales) with better overall psychometric properties is described. In Study 2, we found good support for the composite instrument's internal consistency, as well as convergent, discriminant, and factorial validity in a sample that included a wide age range and nonstudent community residents.     

Gender specific requirement of GluR1 receptors in contextual conditioning but not spatial learning

The GluR1 subunit of the AMPA receptor is required for hippocampal-dependent memory formation, emotional learning and synaptic plasticity. Recent work has shown that GluR1-independent synaptic plasticity is mediated by nitric oxide. Nitric oxide activity is influenced by estrogen. It is unknown whether this gender-dependent effect conveys a gender dimorphic requirement of GluR1 for learning. This hypothesis was tested in two behavioral paradigms. In Experiment 1, the retention of contextual fear conditioning was impaired in male but not female GluR1 knockout mice. In Experiment 2, GluR1 knockout mice made significantly more arm entry errors during acquisition of a radial-arm watermaze task. This deficit was independent of gender. These results indicate that some forms of learning are gender dimorphic in GluR1 knockout mice. The results are discussed with reference to task and gender-specific interactions between GluR1 receptor intracellular signalling pathways.     

Configural learning without reinforcement: integrated memories for correlates of what, where, and when

In 2 experiments we examined the ability of rats to form configural memories of what auditory stimulus (X or Y) was presented where (Context A or B) and when (morning or afternoon). In both experiments, rats received morning presentations of X in Context A and Y in Context B and afternoon presentations of X in B and Y in A. Subsequently, at midday the rats were exposed to trials where X was paired with footshock whereas Y was not. We then assessed the degree of contextual fear in A and B in the morning and the afternoon. In the morning, rats showed more fear in A than in B, and in the afternoon they showed more fear in B than in A. These results indicate that rats can form configural memories that represent what (X or Y) was presented, where (A or B), and when (morning or afternoon).     

医生献血救人该不该罚——论卫生法律在卫生执法中的正确适用

卫生执法的根本目的是实现卫生法律的立法目的.卫生执法应当尊重卫生法律的基本精神,而不应当对卫生法律断章取义,并应当切实尊重公民的生命健康权.     

When stereotypes disadvantage boys: Strength of stereotypes in mathematics and language arts and their relations with grades

There is growing concern about boys' lagging performance in school, not only in language arts, where the gap is particularly pronounced, but also in mathematics. Stereotypes associating one gender with language arts or with mathematics are likely to contribute to these gaps. Such stereotypes can translate into explicit beliefs such as the extent to which students are aware of societal stereotypes or the extent to which they personally believe stereotypes to be true, but also indirectly into performance following a stereotype threat manipulation. However, few studies have considered these multiple stereotype expressions in both mathematics and language arts to examine their importance in predicting boys' and girls' actual grades in school. To fill this gap, two complementary studies examined high school boys' and girls' awareness and endorsement of stereotypes about both language arts (n = 299) and mathematics (n = 243), as well as whether stereotype threat impaired boys' performance on a spelling test. Although the effect of stereotype threat was not significant overall, our results showed that students were aware of and endorsed strong stereotypes advantaging girls in language arts. In mathematics, students endorsed counter-traditional stereotypes slightly advantaging girls. Our results also showed that these multiple expressions of stereotypes related to students' grades. In doing so, our work provides insights regarding possible targets for interventions to reduce gender gaps disadvantaging boys in school.