Inhibition of the LH Surge by Restraint Stress in Cyclic Rats: Studies on the Role of GABAA and GABAB Receptors

There is evidence that stress can alter the activity in the brain of gamma-aminobutyricacid (GABA), a neurotransmitter that has been implicated in the regulation of LH secretion. In the present study the role of GABA in the restraint stress-induced inhibition of the LH surge was investigated in the intact cyclic rat. Intracerebroventricular (icv) administration of the GABAA receptor agonist muscimol (0.1, 0.5 or 1 μg) 5 min before the presumed onset of the pro-oestrous LH surge (at 0900 h) caused a dose dependent suppression of the surge. A single dose of the GABAB receptor agonist baclofen (1 μg; icv) injected at 0855 h postponed the onset of the LH surge, and repeated injections at 0855 and 1130 h suppressed the surge. These data indicate that GABA-ergic activity in the brain can inhibit the LH surge in the cyclic rat via GABAA and GABAB receptors. Pro-oestrous rats were subjected to 5 hrs of restraint starting at 0855 h. Pretreatment with the GABAA receptor antagonist bicuculine (1 μg; icv) at 0840, 0940 and 1040 h or pretreatment with the GABAB receptor antagonist phaclofen (10 μg; icv) at 0840 h were ineffective in preventing the restraint-induced inhibition of the LH surge. The results suggest that GABAA and GABAB receptors are not involved in the inhibitory effect of restraint stress on the LH surge.     

The time course of argument reactivation revealed: using the visual world paradigm

Previous research has found that the single argument of unaccusative verbs (such as fall) is reactivated during sentence processing, but the argument of agentive verbs (such as jump) is not (Bever & Sanz, 1997; Friedmann, Taranto, Shapiro, & Swinney, 2008). An open question so far was whether this difference in processing is caused by a difference in thematic roles the verbs assign, or a difference in the underlying syntactic structure. In the present study we tease apart these two potential sources. In order to achieve this, we included a set of verbs (like sparkle) which are equal to unaccusative verbs in the thematic role they assign to their argument, but equal to agentive verbs in the syntactic status of their argument (henceforth mixed verbs). As a method we used the visual world paradigm as this enables us to measure processing of the sentences continuously. This method also allowed us to test another hypothesis, namely the hypothesis that not only the argument of unaccusative verbs is reactivated during processing, but also the argument of agentive verbs. This reactivation is expected as the result of integrating the verb and its argument into one representation. In our experiment, participants listened to sentences including one of the three types of verbs. While listening, they viewed a visual display in which one of four objects was strongly related to the argument of the verb (wood-saw). The gaze record showed that the eyes moved to the related object (saw) upon presentation of the argument (wood). More interestingly, the eyes moved back to the related object upon presentation of the verb (fell). We found that looks to the related object increase only late after verb offset for unaccusative verbs, replicating the findings of previous research. We also found a rise in looks to the related object in agentive verbs, but this rise took place much earlier, starting slightly after verb onset. Finally, we found that mixed verbs pattern in processing with agentive verbs. We conclude that the argument of the verb is always reactivated, independent of verb type. In addition, the timing of integration differs per verb type and depends on the syntactic status of the argument and not on the thematic role that is assigned to the argument.     

Teacher practices as predictors of children's classroom social preference

Students who do not get along with their peers are at elevated risk for academic disengagement and school failure. Research has predominantly focused on factors within such children that contribute to their peer problems. This study considers whether teacher practices also predict social preference for children in that classroom. Participants were 26 elementary school teachers and 490 students in their classrooms followed for one school year. Results suggested that teachers who favored the most academically talented students in the fall had classrooms where children had lower average social preference in the spring after statistical control of children's fall social preference and externalizing behavior problems. Teachers who demonstrated emotionally supportive relationships with students in the fall had classrooms where children had greater possibility of changing their social preference from fall to spring. Although children with high externalizing behaviors tended to experience declining social preference over the course of the school year, teachers' learner-centered practices attenuated this progression. However, teachers' favoring of the most academically talented accentuated the negative relation between externalizing behaviors and social preference. Implications for school psychology practitioners are discussed.     

PET studies of language: An assessment of the reliability of the technique

In order to understand the basis of language in the brain, we must be able to describe the neurological systems that are used in language comprehension and production. In this paper, one technique for functional neuroimaging is discussed: measurement of blood flow change using positron emission tomography (PET). Two experiments were carried out investigating the usefulness of this method. One experiment examined the intrinsic time limitations of blood flow change as a measure of cognitive activity. A second issue considered is the replicability of the results obtained using this method. A comparison of two experiments containing the same conditions suggests that the results are replicable, when the experiments and method are similar. One case is discussed where the experiments differ; it is suggested that this is due to a difference in the materials used in the experiments, and that the difference has a principled basis.