Practice improves even the simplest movements

Summary Three subjects practiced accurate, fast elbow flexions of 54° to a 3° wide target. Movements of 36°, 54° and 72° were then tested. Comparison over the three distances showed that the normally monotonic relationship between movement distance and movement time is alterable by specific training. Subjects learn to go faster over the practiced distance by refining their neural commands to the muscles. The benefits of practice only partially transfer to other distances. We conclude that many of the relationships seen among movement variables in simple tasks are plastic in nature and affected by prior experience.     

Influence of histamine depletion on learning and memory recollection in rats

To clarify the role of endogenous histamine in learning and memory, the effect of -fluoromethylhistidine on active avoidance response in rats was studied. -Fluoromethylhistidine (20–100 mg/kg or 10–50 µg) significantly (P<0.05 orP<0.01) prolonged the response latency in active avoidance response when administered by either intraperitoneal or intracerebroventricular injection. These effects were dose-related and long lasting. A prolongation of the response latency induced by an intraperitoneal injection of -fluoromethylhistidine (100 mg/kg) was antagonized by intracerebroventricular injection of histamine (10 and 20 ng) in a dose-dependent manner. In addition, the acquisition of this response was retarded by a consecutive intracerebroventricular injection of -fluoromethylhistidine (50 µg), whereas histamine (100 ng) facilitated the response acquisition when administered by the same route. Both intraperitoneal (100 mg/kg) and intracerebroventricular injection of -fluoromethylhistidine (50 µg) significantly (P<0.05 orP<0.01) decreased the brain histamine content, especially in the hippocampus and hypothalamus. When -fluoromethylhistidine (50 µg) was injected intracerebroventricularly, there is a high correlation between a prolongation of the response latency and a decrease in histamine content of these brain areas. Based on these findings, it was concluded that an intimate relation may exist between a prolongation of response latency in the active avoidance response and a decrease in the brain histamine content; endogenous histamine may play an important role in learning and memory recollection in rats.     

Strain-dependent effects of post-training GABA receptor agonists and antagonists on memory storage in mice

Post-training administration of the GABA-A and GABA-B receptor agonists muscimol and baclofen dose-dependently impaired retention of an inhibitory avoidance response in C57 mice, while improving memory consolidation in the DBA strain. By contrast, picrotoxin (blocker of GABA-activated ionophores), bicuculline (GABA-A antagonist) and CGP 35348 (GABA-B antagonist) dose-dependently improved retention in C57 mice and impaired it in DBA mice. These effects cannot be ascribed to non-specific actions of the drugs on retention performance, as the latencies during the retention test of those mice that had not received footshock during the training were not lengthened by the post-training drug administration. The effects on retention performance induced by GABA agonists and antagonists are probably due to an effect on memory consolidation, since they are observed when the drugs are given at short, but not at long, intervals after training. These results are discussed in terms of possible interaction of GABA systems with endogenous opioid and dopamine systems, whose activation has been shown to produce strain-dependent effects on memory processes. The possible utilization of these results for a genetic behavioral approach with recombinant inbred (RI) mice is also considered.     

The role of body image in sexually avoidant behavior

Spectatoring refers to a cognitive self-absorption, wherein individuals fixate on and carefully monitor personal body parts and/or the adequacy of personal sexual functioning. To examine this process within a university population, undergraduate and graduate students (108 male and 140 female) filled out questionnaires that assessed body image, sexual knowledge, global sexual attitudes (i.e., liberal—conservative), general psychological adjustment, and frequency of sexual behaviors. Multiple regression analyses were used to determine if spectatoring, operationalized by measures of body image, would significantly predict sexually avoidant behavior. Results indicated that body image scores significantly predicted frequency of sexual behaviors for both genders, while general sexual knowledge and psychological adjustment did not predict sexual behavior. Overall, sexual attitude scores were the best predictors of sexual approach/avoidance behaviors for both genders. Implications are drawn for future research using the assessment of more global sex attitudes in the study of spectatoring.     

迷宫学习模型实验的时反应量-效关系

目的　分析学习记忆动物行为模型实验的时反应量 效关系指标。方法　应用Y型迷宫刺激器对大鼠进行空间学习记忆的行为模型实验。结果　测得大龄组 (约 12月 )和小龄组 (<4月 )大鼠达到学会标准前所需的刺激次数分别为 (32 .6 2± 2 0 .5 9)次 (n =2 1)和 (2 0 .6 2± 14.2 5 )次 (n =2 1,P <0 .0 5 ) ,学会时 9次正确反应的潜伏期分别为 (7.44± 2 .89)s和 (6 .93± 1.49)s(P >0 .0 5 ) ,并观察到刺激次数与逃避到安全区的潜伏期呈类双曲线型时反应量 效关系、刺激次数与移动正确率呈非线性正变关系。结论　迷宫学习模型实验存在特殊类型的时反应量 效关系。     

高压氧对幼龄小鼠自发活动及分辨学习的影响

目的 :探讨不同压力的高压氧处理后 ,幼龄小鼠对新异环境的探究行为和自发活动的变化以及分辨学习的影响。方法 :用开场行为模型和Y 迷宫分辨学习模型观察小鼠的各项行为指标。结果 :与对照相比 ,吸 10 1 3kPa高压氧的幼龄小鼠学习记忆能力明显提高 ;吸 2 5 3 3kPa高压氧的幼龄小鼠学习记忆能力无明显变化 ,但其在新异环境中的自发行为明显减少。结论 :实验结果提示 :慢性吸入 10 1 3kPa高压氧有益于幼龄小鼠脑的生长发育 ,增强脑功能活动 ,但其作用机制还有待于进一步研究     

Sensory effects of baroreceptor activation and perceived stress together predict long-term blood pressure elevations

Activating the arterial baroreceptors in animals has been shown to blunt pain sensation and provide other forms of central nervous system inhibition. This study tested the hypothesis that, among human subjects, a tonic increase in blood pressure (BP) could be a learned response to environmental stressors among subjects in whom the baroreceptor inhibitory mechanism is active. In a sample of 96 healthy, normotensive men and women, amount of pain-reduction produced by baroreceptor stimulation predicted an increase in resting BP 20 months later: the increase was proportional to self-assessed daily life stress. Among the subjects reporting the greatest amount of stress, the pain inhibition effect accounted for more than 80% of the BP variance. These results support the hypothesis that the reduction in perceived stress produced by baroreceptor stimulation may reward learned increases in BP. This research was supported by Deutsche Forschungsgemeinshaft Grant EL 101/3 to Thomas Elbert and National Institutes of Health Grant ROl HL40837 to B. R, Dworkin.     

Chronic treatment with MK-801 affects the behavioral response to both D1 and D2 dopamine agonist in the one-trial inhibitory avoidance

Post-training administration of theN-methyl-d-aspartate (NMDA) antagonists CPP (0.5 and 1.0 mg/kg) and MK-801 (0.25 and 0.5 mg/kg) impaired, in a dose dependent fashion, the one-trial inhibitory avoidance response in NMRI mice. The D₁ dopamine (DA) agonist SKF 38393 (10 and 20 mg/kg) and the D₂ agonist quinpirole (0.5 and 1.0 mg/kg) instead facilitate the response in the same behavioral paradigm. Sub-chronic blockade of NMDA receptors with MK-801 (0.25 mg/kg once a day for 14 days) did not change the response to both competitive (CPP) and non-competitive (MK-801) NMDA antagonists. The same chronic treatment with MK-801 induced an increased response to both SKF 38393 and quinpirole. These data suggest that repeated administration of MK-801 induce an upregulation of both D₁ and D₂ DA receptors without affecting NMDA receptors.     

Attitudes and Approaches of Influential Role Models in Clinical Education

The influence of a role model is a frequently cited factor in choosing a specialty choice among medical students, particularly primary care oriented students. While many studies have looked at role modeling from students' perspectives, very few have considered role modeling characteristics from the perspective of the role models. This study, using the principles of Bandura's social learning theory, determined and illuminated the characteristics and teaching methods associated with positive role modeling in clinical education from the perspective of the role model. A qualitative approach employing interviews and observations was used. Five themes emerged: the role models' approaches to teaching, their attitudes towards teaching and learning, their emphasis on clinical competence in their teaching, their roles external to their specific responsibilities, and their general affect. We found that role models were similar in their views of teaching and working with students. Also, their teaching characteristics were similar to the recommended approaches found in the literature and adhered to the principles of social learning theory. Role models were attentive to the needs of the students and tailored their teaching appropriately. They provided students with ample patient interaction so that students could apply their classroom knowledge. They also demonstrated how rewarding being an effective physician can be. This revised version was published online in June 2006 with corrections to the Cover Date.