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891.
J L Vercher N Dusticier Y Ebihara A Nieoullon G M Gauthier 《Behavioral and neural biology》1990,53(3):411-427
A method was developed to determine the effects of pyridostigmine on sensory-motor control in baboons trained to perform visuo-oculo-manual tracking tasks. The performance was evaluated in terms of accuracy, maximum smooth pursuit velocity, and gain. Administration of pyridostigmine (0.4-0.7 mg/kg intramuscularly) induced a dose-related decrease in smooth pursuit performance which appeared 10 to 30 min after injection and lasted about 1 h. If the animal was allowed to track the target with its hand or to move the target itself, the smooth pursuit performance increased significantly, returning to near normal values. The movement of the hand was not altered. The effect of intramuscular injections of pyridostigmine (0.5 mg/kg) was studied on blood acetylcholinesterase activity in alert baboons. Maximum inhibition of about 60% of baseline activity was observed 10 min after pyridostigmine injection. Subsequently the activity slowly tended to return to control level. Three hours after drug administration, acetylcholinesterase activity inhibition was still 34.1% of control value. In the baboon, the time-course of acetylcholinesterase activity recovery after injection is similar to that recorded in human. The similarity of the time-course of blood acetylcholinesterase activity and changes in smooth pursuit performance suggests a causal relationship between the two factors. A further experiment showed that pyridostigmine administered per os at a dose normally used as a prophylactic against organophosphates does not significantly alter sensorimotor performance as evaluated at the oculomanual tracking system level. When compared to the literature, our results suggest that the baboon can be used as a human experimental analog for pharmacological studies such as the action of acetylcholinesterase inhibitors. 相似文献
892.
893.
Manin DY 《Cognitive Science》2008,32(7):1075-1098
Zipf's law states that if words of language are ranked in the order of decreasing frequency in texts, the frequency of a word is inversely proportional to its rank. It is very reliably observed in the data, but to date it escaped satisfactory theoretical explanation. This article suggests that Zipf's law may result from a hierarchical organization of word meanings over the semantic space, which in turn is generated by the evolution of word semantics dominated by expansion of meanings and competition of synonyms. A study of the frequency of partial synonyms in Russian provides experimental evidence for the hypothesis that word frequency is determined by semantics. 相似文献
894.
Recent work has shown that correcting a dispositional inference may lead social observers to over‐emphasize the role of dispositional factors in subsequent judgments. This effect has been explained as a procedural rebound following a phase of dispositional suppression. We conducted two experiments to test an alternative explanation in terms of ego‐depletion. In Experiment 1, we compared the effects of ego‐depletion and dispositional rebound by relying on the attitude attribution paradigm and the cookie paradigm. In Experiment 2, we turned to a difficult math task in order to induce fatigue. We were able to replicate the dispositional rebound and the ego‐depletion effects but none of the experiments supported an ego‐depletion explanation of post‐suppression dispositional rebound. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
895.
Terri R. Kurtzberg Charles E. Naquin Liuba Y. Belkin 《Organizational behavior and human decision processes》2005,98(2):1294-226
Across three empirical studies, this paper explores the effect of using e-mail as a communication medium (versus pen-and-paper) when conducting performance appraisals of peers. The notion put forth by Media Richness Theory that paper-form and e-mail media should be considered identical for conveying this information was theoretically challenged and differences were empirically supported. Using two different settings, results demonstrate that evaluators offered more negative appraisals of their peers when using e-mail than when using traditional paper-form methods. Reduced feelings of social obligation in the e-mail condition were found to mediate this relationship, indicating that social psychological processes can influence the effects of different media on peer ratings. 相似文献
896.
Perceived barriers to help-seeking among adolescents attending a suicide education program were examined. A total of 854 high school students in Colorado completed one of two questionnaires, measuring barriers to help-seeking for self or friend. The most prominent barriers for self were: inability to discuss problems with adults, self-overconfidence, fear of hospitalization, and lack of closeness to school adults. The most prominent barriers for troubled friends were: friendship concerns, unapproachability of school adults, fear of friend's hospitalization, and underestimating friend's problems. Results reveal multiple constraints limiting the program's utilization, supporting the need for comprehensive system approaches to suicide prevention. 相似文献
897.
How do infants identify the psychological actors in their environments? Three groups of 12‐month‐old infants were tested for their willingness to encode a simple approach behavior as goal‐directed as a function of whether it was performed by (1) a human hand, (2) a morphologically unfamiliar green object that interacted with a confederate and behaved intentionally, or (3) the same unfamiliar green object that behaved in a matched, but apparently random manner. Using a visual habituation technique, only infants in the first two conditions were found to encode the approach behavior as goal‐directed. Thus infants appear able to attribute goals to non‐human, even unfamiliar agents. These results imply that by the end of the first year of life infants have a broad notion of what counts as an agent that cannot easily be reduced to humans, objects that are perceptually similar to humans, or objects that display self‐propulsion. 相似文献
898.
We investigated the interaction between transient change in the local structure of gastrocnemius muscle fibers and the segmented leg motor responses elicited by toes-up rotation of the support surface. The gastrocnemius muscle in healthy young subjects underwent a sustained 2-min, isometric stretch (Prestretch group), followed immediately by the rotations. Analysis showed that the prestretch affected the amplitude of the monosynaptic but not the automatic components of the medial gastrocnemius muscle responses (monosynaptic response: 93 +/- 20% of the mean of the last three rotations in the Prestretch group compared to 174 +/- 42% in the Control group; automatic response: 128 +/- 18% in the Prestretch group versus 123 +/- 31% in the Control group). The shortened tibialis anterior muscle response and the onset latencies of responses were not affected by prestretching the gastrocnemius muscle. The prestretch effect on the amplitude of the monosynaptic (mediated by group Ia afferents) but not the automatic gastrocnemius muscle response (mediated by group II afferents) suggests that the automatic component of the muscle response to platform rotations has a stronger supraspinal influence than the monosynaptic response and is thus less affected by local events such as prolonged stretching. 相似文献
899.
In three European regions (The Netherlands, Northern Italy and Southern Italy) we investigated whether mothers of healthy pre‐term infants (n=92) adjust their expectations for the timing of developmental milestones in the first years of life as compared to mothers of full‐term infants (n=140). We examined whether these adjustments could be seen as reflecting a pessimistic view, as would be predicted from the ‘prematurity stereotype’ perspective. Partial corrections for prematurity were regularly made, but no indications were found for an overly pessimistic view. Moreover, the differences between the regions in the anticipated timing of mastery of milestones were larger than the effects of prematurity. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
900.
Carrianne K.Y. Leung 《Studies in Ethnicity and Nationalism》2006,6(2):162-179
Notions of national heritage and identity are complicated in Canada, a settler nation with its central characteristic presented as institutionalised multiculturalism. Popular and official discourses of heritage and multiculturalism work together to produce ideas of Canadian‐ness. The twin objectives of this paper are to describe how representations of racial difference are used as a resource to produce notions of official multiculturalism and a ‘heritage of multiculturalism’ discourse — or how notions of multiculturalism emerge as an integral part of national culture/heritage/identity. I argue that the conceptualisation of ‘heritage’ and ‘multiculturalism’ are produced through the representation of racialised difference in national narratives and that taken together, the two discourses act as a highly flexible form of governmentality. 相似文献