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191.
In 2 experiments, the effects of mental stress on limb stiffness were investigated. The relative contribution to arm stiffness of individual muscle activity, co-contraction, muscle reflexes, and postural adjustments were examined. In each experiment, participants (N = 24, Experiment 1; N = 16, Experiment 2) held their supinated hand under a tray that they were required to return to horizontal after it had been suddenly released. Electromyographic activity in the biceps and triceps muscles was recorded, as were elbow and wrist angles and tray displacement. In Experiment 1, mental arithmetic stress was shown to lead to decreased tray displacement (i.e., increased resistance) compared with displacements under the control, unstressed condition, as well as to increased elbow flexion before tray release. In Experiment 2, the increased resistance to perturbation caused by mental stress was found to be independent of initial elbow angle, but to vary as a function of the amount of upward force exerted before tray release. The authors conclude that stress-induced increases in limb stiffness result from changes in the initial position of the elbow, specified by its angle, together with the initial force exerted by participants to counteract the mechanical perturbations. 相似文献
192.
Chronic, severe hypertension does not impair spatial learning and memory in Sprague-Dawley rats 总被引:1,自引:0,他引:1 下载免费PDF全文
This study tested the hypothesis that long-term hypertension impairs spatial learning and memory in rats. In 6-wk-old Sprague-Dawley rats, chronic hypertension was induced by placing one of three sizes of stainless steel clips around the descending aorta (above the renal artery), resulting in a 20–80-mm Hg increase of arterial pressure in all arteries above the clip, that is, the upper trunk and head. Ten months later, the rats were tested for 5 d in a repeated-acquisition water maze task, and on the fifth day, they were tested in a probe trial; that is, there was no escape platform present. At the end of the testing period, the nonsurgical and sham control groups had similar final escape latencies (16±4 sec and 23±9 sec, respectively) that were not significantly different from those of the three hypertensive groups. Rats with mild hypertension (140–160 mm Hg) had a final escape latency of 25±6 sec, whereas severely hypertensive rats (170–199 mm Hg) had a final escape latency of 21±7 sec and extremely hypertensive rats (>200 Hg) had a final escape latency of 19±5 sec. All five groups also displayed a similar preference for the correct quadrant in the probe trial. Together, these data suggest that sustained, severe hypertension for over 10 mo is not sufficient to impair spatial learning and memory deficits in otherwise normal rats. 相似文献
193.
Regulation of distinct attractive and aversive mechanisms mediating benzaldehyde chemotaxis in Caenorhabditis elegans 总被引:1,自引:0,他引:1 下载免费PDF全文
Nuttley WM Harbinder S van der Kooy D 《Learning & memory (Cold Spring Harbor, N.Y.)》2001,8(3):170-181
Olfactory-mediated chemotaxis in nematodes provides a relatively simple system to study biological mechanisms of information processing. Analysis of the kinetics of chemotaxis in response to 100% benzaldehyde revealed an initial attractive response that is followed by a strong aversion to the odorant. We show that this behavior is mediated by two genetically separable attraction- and aversion-mediating response pathways. The attraction initially dominates behavior but with prolonged exposure habituation leads to a behavioral change, such that the odorant becomes repulsive. This olfactory habituation is susceptible to dishabituation, thereby re-establishing the attractive response to the odorant. Re-examination of the putative olfactory adaptation mutant adp-1(ky20) revealed that the phenotype observed in this line is due to a supersensitivity to a dishabituating stimulus, rather than a defect in the adaptation to odorants per se. A modified benzaldehyde chemotaxis assay was developed and used for the isolation of a mutant with a specific defect in habituation kinetics, expressed as a persistence of the attractive response. 相似文献
194.
Several studies have found effects of orthographically related masked nonword primes on lexical decisions to target words. These effects have been explained by the neighborhood characteristics of the target word (Forster, 1987), but the neighborhood characteristics of the prime in combination with the target are also found to be important (Hinton, Liversedge, & Underwood, 1998). In this study, we present a new account of masked form-priming effects based on the shared neighborhood of prime and target. Shared neighbors are words that are activated by both prime and target. According to the interactive activation model (McClelland & Rumelhart, 1981), shared neighborhood determines the size of priming effects. This prediction was tested and confirmed in a masked priming experiment that manipulated the shared neighborhood density of complete primes. 相似文献
195.
This article reports on the development and teaching of compulsory courses on ethics and engineering at Delft University of
Technology (DUT). Attention is paid to the teaching goals, the educational setup and methods, the contents of the courses,
involvement of staff from engineering schools, experiences to date, and challenges for the future. The choices made with respect
to the development and teaching of the courses are placed within the European and Dutch context and are compared and contrasted
with the American situation and experiences.
Previous versions of this article were presented at the meeting of the SEFI Working Group on Engineering Ethics in Rzeszow,
Poland, April 29–May 1, 1999 and at the SEFI Annual Conference in Zurich, Switzerland, September 1–3, 1999. 相似文献
196.
In this editorial contribution, two issues relevant to the question, what should be at the top of the research agenda for ethics and technology, are identified and discussed. Firstly: can, and do, engineers make a difference to the degree to which technology leads to morally desirable outcomes? What role does professional autonomy play here, and what are its limits? And secondly, what should be the scope of engineers' responsibility; that is to say, on which issues are they, as engineers, morally obliged to reflect? The research agendas proposed by the authors contributing to this special section, implicitly, give different answers to these questions. We suggest that an explicit discussion of these issues would greatly help in constructing a common research agenda. 相似文献
197.
Ton van den Beld 《Ethical Theory and Moral Practice》2001,4(4):383-399
What I set out to do is to cast some doubt on the thesis that, in Bernard Williams's words, any appeal to God in morality either adds nothing at all, or it adds the wrong sort of thing. A first conclusion is that a morality of real, inescapable and (sometimes) for the agent costly obligations, while being at home in a theistic metaphysic, does not sit easily with metaphysical, atheistic naturalism. The second conclusion is that Christine Korsgaard's impressive ethical project which is neutral towards theism and atheism fails in giving a satisfying account of such obligations. My final claim is that a theistic account in terms of a strong divine command theory might succeed where non- and atheistic accounts seem to founder. 相似文献
198.
The most generally accepted and best documented manipulation in procedural justice experiments is varying whether or not participants are allowed an opportunity to voice their opinion about a decision. To better understand the psychology of voice, the authors focus on Referent Cognitions Theory (RCT). It is argued that thus far RCT has not been used to explain the psychology of voice and that previous RCT research suffers from methodological problems and has been more outcome oriented than necessary. Two experiments resolve these problems and show that people react more strongly to procedures (especially no-voice procedures) when reference points are close as opposed to distant. These findings suggest that closeness of reference points plays an important role in the psychology of voice. The findings expand RCT in significant ways and indicate that insight into the role of reference points is essential for understanding the psychology of justice. 相似文献
199.
Los SA van den Heuvel CE 《Journal of experimental psychology. Human perception and performance》2001,27(2):370-386
The nonspecific preparation that follows a warning stimulus (WS) to speed responding to an impending imperative stimulus (IS) is generally viewed as a strategic, intentional process. An alternative view holds that WS acts as a conditioned stimulus that unintentionally elicits a tendency to respond at the moment of IS presentation as a result of a process of trace conditioning. These views were contrasted as explanatory frameworks for classical effects on reaction time of the duration and intertrial variability of the foreperiod, the interval between WS and IS. It is shown that the conditioning view accounts for the available data at least as well as the strategic view. In addition, the results of 3 experiments provide support for the conditioning view by showing that unintentional contributions to nonspecific preparation can be dissociated from intentional contributions. 相似文献
200.
The present study examined the relationship between self-reported behavioural inhibition and psychopathological symptoms in a sample of 152 children aged 12-14 years. Children were provided with a definition of behavioural inhibition and then asked to classify themselves as low, middle or high on behavioural inhibition. Furthermore, children completed questionnaires of worry, depression and anxiety symptoms. Results showed that children who endorsed the high behavioural inhibition category had elevated levels of anxiety, worry and depression compared to children who endorsed the low or middle behavioural inhibition categories. Moreover, children high on behavioural inhibition more frequently reported anxiety disorders symptoms in the subclinical range. These findings fit well with those of previous studies on behavioural inhibition. 相似文献