学习障碍儿童记忆的比较研究 Ⅰ.学习障碍儿童的短时记忆和工作记忆

目的：考查学习障碍儿童的短时记忆和工作记忆及各型学习障碍儿童短时记忆特征，比较短时记忆和工作记忆对学习的相对贡献。方法：根据儿童的学科成绩、智力水平、教师对学习能力的评定，结合临床观察，从三所小学１５６４名学生中筛查出学习障碍儿童９７人（男７１人，女２６人），正常学习儿童６３人（男３６，女２７人），并根据主要困难所在把学习障碍儿童分为三组：语文障碍（３１人）、数学障碍（２１人）和混合型障碍（４５人）。对每个入组儿童作个别记忆测查，内容包括短时记忆（数字、汉词和符号）和工作记忆（数字、汉词、符号、故事）。结果：混合型障碍的短时记忆和工作记忆均低于对照组，语文障碍对言语材料的短时记忆和工作记忆中的故事理解低于对照组，数学障碍仅言语材料的短时记忆低于对照组；三型学习障碍之间仅在数字广度和故事Ⅱ阅读理解二项任务上有差异；短时记忆和工作记忆与学习成绩均有中度相关，工作记忆与数学成绩的相关更高。结论：学习障碍儿童存在共同的短时记忆和工作记忆缺陷，但缺陷程度有差异，这种缺陷可能与言语编码缺陷或记忆系统本身功能障碍有关。     

Learning,habituation, and training

Summary The apparent efficiency of sub-maximum exercise tends to be lower in subjects with a large aerobic power. This is probably an artefact arising from neglect of the oxygen debt in the calculation of mechanical efficiency. Changes in the extent of oxygen debt can obscure an increased skill of performance with training. Efficiency is improved by repetition of a given mode of exercise, but not by other forms of training. Habituation is greater during work than at rest, but even during work the change in pulse rate of young men does not exceed 2–5 beats/min over 5 experimental days. Habituation is lost if the test procedure is not repeated during training; this can complicate assessments of training from the response to sub-maximum exercise.     

Exposure to extremely low-frequency electromagnetic fields improves social recognition in male rats

The effect of exposure to low-frequency electromagnetic fields (ELF EMFs) on social recognition was studied. The test was based upon a comparison between two encounters of an adult rat and a conspecific juvenile, separated by an interexposure interval (IEI). The exposure to ELF EMF of 1 mT intensity during 2 h for 9 days increased the duration of short-term memory of adult male Wistar rats up to 300 min. These data indicate, for the first time, that ELF EMF improves social recognition memory in rats.     

Changes in muscle recruitment patterns during skill acquisition

The control of movement is predicated upon a system of constraints of musculoskeletal and neural origin. The focus of the present study was upon the manner in which such constraints are adapted or superseded during the acquisition of motor skill. Individuals participated in five experimental sessions, in which they attempted to produce abduction-adduction movements of the index finger in time with an auditory metronome. During each trial, the metronome frequency was increased in eight steps from an individually determined base frequency. Electromyographic (EMG) activity was recorded from first dorsal interosseous (FDI), first volar interosseous (FVI), flexor digitorum superficialis (FDS), and extensor digitorum communis (EDC) muscles. The movements produced on the final day of acquisition more accurately matched the required profile, and exhibited greater spatial and temporal stability, than those generated during initial performance. In the early stages of skill acquisition, an alternating pattern of activation in FDI and FVI was maintained, even at the highest frequencies. In contrast, as the frequency of movement was increased, activity in FDS and EDC was either tonic or intermittent. As learning proceeded, alterations in recruitment patterns were expressed primarily in the extrinsic muscles (EDC and FDS). These changes took the form of increases in the postural role of these muscles, shifts to phasic patterns of activation, or selective disengagement of these muscles. These findings suggest that there is considerable flexibility in the composition of muscle synergies, which is exploited by individuals during the acquisition of coordination.     

Integrated medical informatics with small group teaching in medical education

National Taiwan University College of Medicine (NTUCM) introduced small groups of teaching and basic-clinical integrated courses for medical students in 1992. By using computer network and multimedia techniques, this study tried to overcome barriers to learning in small group teaching. The Department of Medical Informatics of NTUCM established campus networking and computer classrooms and provided Internet and intranet network services including mail, netnews, bulletin board systems (BBS), world wide web (WWW), gopher, ftp and local file servers. To implement an interactive learning environment, the authors first tried mail lists, newsgroups and BBS. Next an integrated learning system prototype on the WWW was developed to provide functions including online syllabus, discussion boards simulated to BBS, online talk, interactive case studies, virtual classroom with video on demand (VOD) and Internet medical resources. The results showed that after the medical students completed the required course of medical informatics and had good network access using a network to communicate with each other became a daily practice. In the future, the system will extend to the tutoring of clinical practice and continuing medical education. The authors expect a national medical education network and more international cooperation and exchange.     

Plasticity of the medial prefrontal cortex: Facilitated acquisition of intracranial self-stimulation by pretraining stimulation

Prior electrical stimulation of the medial prefrontal cortex MFC facilitated the subsequent acquisition of intracranial self-stimulation (ICSS) from the same MFC electrode site. Stimulations that were spaced over a period of six days were more effective in producing this facilitation than the same number of stimulations delivered over a two day period. These data suggest that the rewarding effects of MFC stimulation may involve some process akin to the kindling phenomenon and as such may provide insights in the neuronal modifications thought to underlie learning and memory.     

Enhanced zinc consumption causes memory deficits and increased brain levels of zinc

Zinc deficiency has been shown to impair cognitive functioning, but little work has been done on the effects of elevated zinc. This research examined the effect on memory of raising Sprague-Dawley rats on enhanced levels of zinc (10 ppm ZnCO3; 0.153 mM) in the drinking water for periods of 3 or 9 months, both pre- and postnatally. Controls were raised on lab water. Memory was tested in a series of Morris Water Maze (MWM) experiments, and zinc-treated rats were found to have impairments in both reference and working memory. They were significantly slower to find a stationary platform and showed greater thigmotaxicity, a measure of anxiety. On a working memory task, where the platform was moved each day, zinc-treated animals had longer latencies over both trials and days, swam further from the platform, and showed greater thigmotaxicity. On trials using an Atlantis platform, which remained in one place but was lowered on probe trials, the zinc-treated animals had significantly fewer platform crossings, spent less time in the target quadrant, and did not swim as close to the platform position. They had significantly greater latency on nonprobe trials. Microprobe synchrotron X-ray fluorescence (microSXRF) confirmed that brain zinc levels were increased by adding ZnCO3 to the drinking water. These data show that long-term dietary administration of zinc can lead to impairments in cognitive function.     

The effects of practice and delay on motor skill learning and retention

The present study assessed the effects of amount of practice and length of delay on the learning and retention of a timed motor sequence task. Participants learned to reproduce ten-element visual sequences by tapping in synchrony with the stimulus. Participants were randomly assigned to a varied-practice condition or a varied-delay condition. In the varied-practice condition, participants received either one, three, or six blocks of practice followed by a fixed 4-week delayed-recall. In the varied-delay condition, participants received three blocks of practice followed by a varied delay of either 3 days, or 2, 4, or 8 weeks. Learning was assessed by changes in accuracy, response variance, and percent response asynchrony. Our results showed that amount of practice per se did not affect learning and retention of the task. Rather, distribution of practice over several days was the most important factor affecting learning and retention. We hypothesize that passage of time is essential for a maximum benefit of practice to be gained, as the time delay may allow for consolidation of learning, possibly reflecting plastic changes in motor cortical representations of the skill. With regards to delay, our findings suggest that explicit and motoric components of a motor sequence are likely to be learned and maintained in separate but interacting systems. First, only the longest delay group showed decrements in percent correct, indicating that longer lengths of delay might hinder retrieval of explicit aspects of the task. Second, all groups showed a decrement in percent response asynchrony, suggesting that synchronization may be a more difficult parameter to maintain because it relies heavily on sensorimotor integration.     

Long-term deficits after somatosensory cortical lesions in rats.

Rats having either sham operations or one-stage bilateral lesions of the two somatosensory areas of the cortex were tested for acquisition of five tactile discriminations after postoperative recovery intervals of 14, 35, 180, 365 or 730 days. The group with lesions performed worse than its time-matched control group in every instance, and there was no evidence for recovery of function with the longer postoperative recovery periods. These results suggest that time per se is not a significant determinant of restitution after somatosensory cortical ablations.     

急性乙醇中毒大鼠学习记忆行为的改变与脑组织NO和nNOS含量变化

目的：通过观察急性乙醇中毒对大鼠学习记忆的影响并测定脑组织中一氧化氮（NO）与神经型一氧化氮合酶（nNOS）含量的变化，探讨乙醇中毒影响学习记忆的分子机制。方法:成年SD大鼠随机分为2组，模型组腹腔1次性注射乙醇2.5 g/kg［用生理盐水配成含20%乙醇(W/V)溶液］制备急性乙醇中毒大鼠模型；对照组注射等容量的生理盐水。Y-型迷宫检测大鼠学习记忆成绩、硝酸还原酶法检测鼠脑海马CA1、新纹状体中NO的含量、免疫组化方法检测鼠脑海马CA1、纹状体、小脑中nNOS的含量。结果:（1）模型组大鼠达到学会标准所需要的训练次数（34.33±13.04）明显大于对照组（27.50±8.79），P<0.05；（2）海马CA1区NO的含量在模型组为23.09±9.60，明显高于对照组（8.46±5.67）（P<0.01）；新纹状体（尾壳核）NO的含量在模型组（19.46±8.25）也明显高于对照组（8.22±4.46），P<0.01；（3）海马CA1区nNOS阳性神经元的数量在模型组为18.22±7.47，明显高于对照组（10.15±4.24）（P<0.05）；新纹状体（尾壳核）nNOS阳性神经元的数量在模型组（11.38±5.00）也明显高于对照组（6.15±3.69），P<0.05。结论:乙醇的神经毒性作用可能与脑组织中nNOS和 NO信号通路有关。