974 resultados para Bidirectional modulation


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"Issued December 1981"--2d prelim. page.

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Thesis (Ph.D.)--University of Washington, 2016-06

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Thesis (Ph.D.)--University of Washington, 2016-06

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Systemic infection activates the hypothalamic-pituitary-adrenal (HPA) axis, and brainstem catecholamine cells have been shown to contribute to this response. However, recent work also suggests an important role for the central amygdala (CeA). Because direct connections between the CeA and the hypothalamic apex of the HPA axis are minimal, the present study investigated whether the bed nucleus of the stria terminalis (BNST) might act as a relay between them. This was done by using an animal model of acute systemic infection involving intravascular delivery of the proinflammatory cytokine interleukin-1 (IL-1, 1 g/kg). Unilateral ibotenic acid lesions encompassing the ventral BNST significantly reduced both IL-1-induced increases in Fos immunoreactivity in corticotropin-releasing factor (CRF) cells of the hypothalamic paraventricular nucleus (PVN) and corresponding increases in adrenocorticotropic hormone (ACTH) secretion. Similar lesions had no effect on CRF cell responses to physical restraint, suggesting that the effects of BNST lesions were not due to a nonspecific effect on stress responses. In further studies, we examined the functional connections between PVN, BNST, and CeA by combining retrograde tracing with mapping of IL-1-induced increases in Fos in BNST and CeA cells. In the case of the BNST, these studies showed that systemic IL-1 administration recruits ventral BNST cells that project directly to the PVN. In the case of the CeA, the results obtained were consistent with an arrangement whereby lateral CeA cells recruited by systemic IL-1 could regulate the activity of medial CeA cells projecting directly to the BNST. In conclusion, the present findings are consistent with the hypothesis that the BNST acts as a relay between the CeA and PVN, thereby contributing to CeA modulation of hypophysiotropic CRF cell responses to systemic administration of IL-1.

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The present research investigated the effect of performance feedback on the modulation of the acoustic startle reflex in a Go/NoGo reaction time task. Experiment 1 (n = 120) crossed warning stimulus modality (acoustic, visual, and tactile) with the provision of feedback in a between subject design. Provision of performance feedback increased the number of errors committed and reduced reaction time, but did not affect blink modulation significantly. Attentional blink latency and magnitude modulation was larger during acoustic than during visual and larger during visual than during tactile warning stimuli. In comparison to control blinks, latency shortening was significant in all modality conditions whereas magnitude facilitation was not significant during tactile warning stimuli. Experiment 2 (n = 80) employed visual warning stimuli only and crossed the provision of feedback with task difficulty. Feedback and difficulty affected accuracy and reaction time. Whereas blink latency shortening was not affected, blink magnitude modulation was smallest in the Easy/No Feedback and the Difficult/Feedback conditions. (C) 2002 Elsevier Science B.V. All rights reserved.

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Previous studies found larger attentional modulation of acoustic blinks during task-relevant than during task-irrelevant acoustic or visual, but not tactile, lead stimuli. Moreover, blink modulation was larger overall during acoustic lead stimuli. The present experiment investigated whether these results reflect modality specificity of attentional blink modulation or effects of continuous stimulation. Participants performed a discrimination and counting task with acoustic, visual, or tactile lead stimuli. Stimuli were presented Sustained or consisted of two short discrete stimuli. The sustained condition replicated previous results. In the discrete condition, blinks were larger during task-relevant than during task-irrelevant stimuli in all groups regardless of lead stimulus modality. Thus, previous results that seemed consistent with modality-specific accounts of attentional blink modulation reflect effects of continuous stimulus input.