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.     

Effects of Acute Stress or Centrally Injected Interleukin-1beta on Neuropeptide Expression in the Immune System

Acute stress stimulates the expression and release of corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP) from the hypothalamus, and the pro-opiomelanocortin products beta-endorphin and ACTH from the anterior pituitary. These neuropeptides are also expressed in immune tissues, and it has been proposed that they may modulate immune responses to stress through paracrine mechanisms. We subjected rats to restraint stress or central injection of interleukin (IL)-1beta to determine whether these acute stimuli can alter the expression of neuropeptides in the spleen and thymus. Restraint stress significantly increased the contents of all these neuropeptides in thymic, but not splenic, extracts. A single icv injection of IL-1beta increased contents of CRH, AVP, ACTH and beta-endorphin in the spleens of both sham-operated and adrenalectomised (ADX) rats. IL-1beta increased thymic contents of CRH and ACTH in sham-operated rats but these increases were not observed in ADX rats. These results suggest that the effects of IL-1beta on neuropeptide expression in the spleen are independent of glucocorticoids, whereas IL-1beta stimulation of neuropeptide expression in the thymus is dependent on circulating glucocorticoids. There were significant correlations between increases in CRH, ACTH and beta-endorphin in the spleen, and between CRH and ACTH in the thymus, consistent with the suggestion that IL-1beta-induced increases in ACTH and beta-endorphin may be mediated through CRH. These results provide evidence that stressors can directly influence neuropeptide expression in immune tissues. Thus stress may influence immune functions through paracrine mechanisms involving locally synthesised neuropeptides as well as through activation of the hypothalamo-pituitary-adrenal axis.     

Gratitude in intermediate affective terrain: links of grateful moods to individual differences and daily emotional experience

Two studies were conducted to explore gratitude in daily mood and the relationships among various affective manifestations of gratitude. In Study 1, spiritual transcendence and a variety of positive affective traits were related to higher mean levels of gratitude across 21 days. Study 2 replicated these findings and revealed that on days when people had more grateful moods than was typical for them, they also reported more frequent daily episodes of grateful emotions, more intense gratitude per episode, and more people to whom they were grateful than was typical for them. In addition, gratitude as an affective trait appeared to render participants' grateful moods somewhat resistant to the effects of discrete emotional episodes of gratitude.     

Constrained maximum likelihood estimation of two-level covariance structure model via EM type algorithms

In this paper, the constrained maximum likelihood estimation of a two-level covariance structure model with unbalanced designs is considered. The two-level model is reformulated as a single-level model by treating the group level latent random vectors as hypothetical missing-data. Then, the popular EM algorithm is extended to obtain the constrained maximum likelihood estimates. For general nonlinear constraints, the multiplier method is used at theM-step to find the constrained minimum of the conditional expectation. An accelerated EM gradient procedure is derived to handle linear constraints. The empirical performance of the proposed EM type algorithms is illustrated by some artifical and real examples.This research was supported by a Hong Kong UCG Earmarked Grant, CUHK 4026/97H. We are greatly indebted to D.E. Morisky and J.A. Stein for the use of their AIDS data in our example. We also thank the Editor, two anonymous reviewers, W.Y. Poon and H.T. Zhu for constructive suggestions and comments in improving the paper. The assistance of Michael K.H. Leung and Esther L.S. Tam is gratefully acknowledged.     

Immigrant Youth and Employment: Lessons Learned from the Analysis of LSIC and 82 Lived Stories

Finding a job has become a critical challenge to many youth. Immigrant youth, who have been a key part of the global migrants, are particularly vulnerable when entering the job market of the host country due to various structural barriers. However, in both public policy discourse and research, their labour market experience tends to be overlooked. In this paper, we report the employment experience of recently arrived immigrant youth based on an analysis of the LSIC and findings of in-depth interviews of 82 immigrant youth in four cities in Canada. Our results reveal that recently arrived immigrant youth tend to work in lower-skilled employment, experience significant delays in finding employment, have difficulties with foreign credential recognition, and have fewer means to access to job markets.     

Activation of morphemic meanings in processing opaque words

Two masked priming experiments were conducted to examine the activation of morphemic forms and meanings during opaque word processing. In Experiment 1, opaque primes significantly facilitated the recognition of transparent targets, which was consistent with previous results. However, transparent primes did not influence the recognition of opaque targets. This asymmetry could not be explained solely by morpho-orthographic processing, but it was consistent with models that have assumed early morpho-semantic activation. Experiment 2 directly tested whether the meanings of the constituent morphemes in opaque words were activated. In the critical condition, the targets were unrelated to the opaque primes at the lexical level, but were semantically related to their morphemes (e.g., “butterfly–bread”). Facilitation was observed in this condition, providing strong evidence of morpho-semantic activation during opaque-word recognition. These findings indicate that although initial morphological decomposition is determined by surface morphological form, it does not necessarily imply that morphemic meanings will be activated at later stages of processing. Rather, the morphemic meanings may be available automatically once segmentation is complete.     

Regarding time-sharing with convergent operations

This study contrasts the structural bottleneck and the resource view of attentional limits in time-sharing performance. The research incorporated features of the psychological refractory period (PRP) and the relative priority paradigm designed to maximize joint performance. A main distinction between the two attention views was their prediction on the extent that graded performance tradeoff was possible with graded priority changes. Detailed analysis of the performance and time-sharing strategies called into question the conclusions based exclusively on the PRP paradigm.     

Development and Initial Validation of an Implicit Measure of Religiousness‐Spirituality

An implicit measure of religiousness‐spirituality (RS) was constructed and used in two studies. In Study 1, undergraduates completed a Religiousness‐Spirituality Implicit Association Test (RS‐IAT) and several self‐report measures of RS and related constructs (e.g., religious fundamentalism, authoritarianism). Informants rated the participants’ RS. The RS‐IAT was internally consistent. Implicit RS correlated positively with self‐reported RS, spiritual transcendence, spiritual experiences, religious fundamentalism, and intrinsic religiousness. Informant ratings correlated positively with participants’ self‐reported religiousness but not implicit RS. In Study 2, implicit RS accounted for unique variability in self‐reported attitudes toward gay men and lesbian women when controlling for self‐reported religiousness and right‐wing authoritarianism. These findings demonstrate that an implicit measure of trait RS explains some variability in attitudes that self‐report measures do not. An implicit measure of RS could advance the scientific study of religion beyond what is known from self‐report measures.     

Bimanual and Unimanual Convergent Goal-Directed Movement Times

Three experiments are reported, investigating the effects of using 1 or 2 hands when making convergent low index of difficulty (ID) and visually controlled movements (2 hands meeting together). The experiments involved movements in four different cases—a probe held in the right hand and moved to a target held in the stationary left hand, vice versa of this arrangement, both hands moving with the probe in the right hand and target in the left hand, and vice-versa of this arrangement. Experiments were the standard Fitts’ paradigm, moving a pin into a hole and a low-ID task. In Fitts’ task, 2-hand movements were faster than 1 hand only at higher IDs; this was also the case in the pin-to-hole transfer task and the movement times were lower when the pin was held in the preferred hand. Movements made with low ID showed a small effect of 1- or 2-handed movements, with the effective amplitude of the movement being reduced by about 20% when 2 hands were used.     

Cognitive Discrepancy,Dissonance, and Selective Exposure

Abstract

Although cognitive dissonance is regarded as one of the most recognized causes of selective exposure [N. J. Stroud, Niche News (Oxford University Press, 2011)], the mechanism for such causation is still unclear. By inducing dissonance in a web-based experiment, this study demonstrates how cognitive dissonance relates to information preferences—the intention to seek congruent information and the intention to seek incongruent information. The findings suggest that perceived hostility with respect to one’s belief (cognitive discrepancy) can enhance the intention to seek out for attitude-consistent information. More importantly, individuals were found to have the intention to avoid counterattitudinal information, but only when they experienced some sort of psychological discomfort (dissonance). In other words, while cognitive discrepancy leads individuals to crave for confirming information, only those who encounter negative emotions are likely to employ avoidance of disconfirming information as a dissonance-reduction strategy.