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.     

Anxiety and expectancy violations: Neural response to false feedback is exaggerated in worriers

This study investigated how individual differences in anxiety modulate the neural response to errors and performance feedback. The design included false feedback on some trials in order to test the hypothesis that anxious people show stronger neural reactions to feedback that is worse than expected. Participants completed a trial-and-error learning task that required learning the correct key to press in response to face images. EEG was recorded during the task, and the response-locked error-related negativity (ERN) and feedback-locked ERN were computed to measure neural responses to error commission and feedback. As expected, errors produced a response-locked ERN and false feedback produced a feedback-locked ERN in the group as a whole. High levels of trait worry predicted a disproportionately larger ERN following false feedback, but did not predict the magnitude of the response-locked ERN following errors. These results imply that worry-prone people react more strongly to violations of expectations, rather than to errors themselves.     

Trouble crossing the bridge: altered interhemispheric communication of emotional images in anxiety

Worry is thought to involve a strategy of cognitive avoidance, in which internal verbalization acts to suppress threatening emotional imagery. This study tested the hypothesis that worry-prone individuals would exhibit patterns of between-hemisphere communication that reflect cognitive avoidance. Specifically, the hypothesis predicted slower transfer of threatening images from the left to the right hemisphere among worriers. Event-related potential (ERP) measures of interhemispheric transfer time supported this prediction. Left-to-right hemisphere transfer times for angry faces were relatively slower for individuals scoring high in self-reported worry compared with those scoring low, whereas transfer of happy and neutral faces did not differ between groups. These results suggest that altered interhemispheric communication may constitute one mechanism of cognitive avoidance in worry.     

Error detection and posterror behavior in depressed undergraduates

This study examined the influence of depression on error-monitoring and behavioral compensation after errors, two important aspects of cognitive control. Undergraduates differing in self-reported depression levels completed a modified Stroop task while error-related scalp potentials were recorded. Behaviorally, participants with higher depression scores were disproportionately slower and less accurate after errors in a task condition that included negative emotional words. Physiological results indicated that the amplitudes of the error-related negativity (ERN) and error positivity (Pe), two indices of error detection, were not correlated with depression score. ERN amplitudes predicted behavioral slowdown after errors, but only among more depressed participants in the negative-word condition. Together, the results imply that depression is associated not with an error detection deficit, but rather with alterations in subsequent performance changes, once errors have been identified.     

Anxiety and error monitoring: Increased error sensitivity or altered expectations?

This study tested the prediction that the error-related negativity (ERN), a physiological measure of error monitoring, would be enhanced in anxious individuals, particularly in conditions with threatening cues. Participants made gender judgments about faces whose expressions were either happy, angry, or neutral. Replicating prior studies, midline scalp negativities were greater following errors than following correct responses. In addition, state anxiety interacted with facial expression to predict ERN amplitudes. Counter to predictions, participants high in state anxiety displayed smaller ERNs for angry-face blocks and larger ERNs for happy-face blocks, compared to less anxious participants. These results are inconsistent with the simple notion that anxiety enhances error sensitivity globally. Rather, we interpret the findings within an expectancy violation framework, in which anxious participants have altered expectations for success and failure in the context of happy and angry facial cues, with greater ERN amplitudes when expectations are violated.     

A comparison of the Ponzo illusion with a textural analogue

The inappropriate constancy scaling notion of geometric illusions was explored by employing a textural analogue of the Ponzo figure. Ten Ss estimated the length of a horizontal line by equating it with varying companion lines in the context of the Ponzo figure, a textural analogue, and a baseline control in which the lines appeared with no surrounding contours. The textural analogue had the added feature of imposing no contours at the ends of the horizontal lines. It was found that length estimates were significantly different between the horizontals of the Ponzo figure and control stimuli, but not between the texture figure and a context-free control. The results suggest that inappropriate constancy scaling plays a minor role at best in the perception of geometric illusions.     

Speed constancy as a function of size constancy

If perceived velocity were to be a function of phenomenal extent traversed per unit time, speed constancy would be derivable from size constancy. Experiments were performed to test this possibility in which visible frames of reference were eliminated. With cues to distance, judgments ofspeed approached constancy; without such cues, judgments of speed were in terms of rate ofimage displacement.     

Relationship‐based intervention with at‐risk mothers: Outcome in the first year of life

This study shows that a home‐visiting, relationship‐based intervention, as defined in the UCLA Family Development Project, affects certain areas of family functioning by the time an infant reaches 12 months. Within a randomized trial design, we compared two samples of mothers who were identified as at risk for inadequate parenting in the third trimester of pregnancy with their first child. The primary risk characteristics were poverty and a lack of support. Thirty‐one of these mothers experienced the intervention and thirty‐three did not. Mothers given the opportunity of a positive, trusting, and working relationship with a weekly home visitor as well as a mother–infant group scored significantly higher on measures of their experienced partner and family support. The intervention also made a significant impact on three critical social‐emotional mother–infant transactions in the first year of life. Thus, on a variety of indices including the responses to the Ainsworth Strange Situation, the children in the intervention group were more secure and their mothers more responsive to their needs. Children experiencing the intervention were also more autonomous and task oriented and were encouraged in this regard by their mothers. ©1999 Michigan Association for Infant Mental Health.