Acta neurologica Scandinavica. Supplementum最新文献_第3页

Muscle, reflex and central components in the control of the ankle joint in healthy and spastic man. 肌肉，反射和中枢成分在控制踝关节的健康和痉挛的人。

Acta neurologica Scandinavica. Supplementum Pub Date : 1997-01-01

T Sinkjaer

{"title":"Muscle, reflex and central components in the control of the ankle joint in healthy and spastic man.","authors":"T Sinkjaer","doi":"","DOIUrl":"","url":null,"abstract":"In understanding the control of the ankle joint during different motor tasks, we have to investigate at least three components, namely the influence of i) the passive and intrinsic properties of the intact and active muscle system around the joint (termed the non-reflex component), ii) the mechanical importance of the stretch reflex in the stretched and unloaded muscles, and iii) the supraspinal control of the stretch reflex. This thesis is dealing with the importance of the three components in healthy and spastic persons during sitting, standing, and walking. The results are based on stretch reflex and H-reflex measurements from the ankle extensor muscles. During stretch reflex experiments the foot was mounted to a platform (portable during walking) from which the ankle joint torque and the position were measured. To elicit a stretch reflex, the ankle joint was rotated by a strong motor connected to the platform. The mechanical importance of the stretch reflex was investigated by measuring the changes in joint torque. Electrically, the stretch reflex was recorded as the compound muscle action potential through bipolar surface EMG electrodes placed over the soleus muscle. During H-reflex experiments, the tibial nerve was stimulated at the popliteal fossa and the H-reflex recorded over the soleus muscle as during stretch reflex experiments. To investigate how the contractile properties of a muscle in humans depend on the history of activation, we investigated the intrinsic stiffness of the ankle extensors in healthy subjects. At matched background contraction in sitting subjects, a prolonged contraction increased the intrinsic muscle stiffness by 49%. Muscle yielding has been considered especially important for understanding the reflex compensation. We found a general lack of muscle yield and a mechanically important non-reflex stiffness of the ankle extensors showing that non-reflex stiffness is a prominent factor in normal movements of the ankle joint. In both healthy and spastic persons, we found a mechanically strong stretch reflex in the isometric, contracted muscles during sitting. This posed the question; how is the reflex regulated during more functional motor tasks. This was dealt with by studying the H-reflex during isometric ramp contractions and during walking in healthy and spastic persons. In the healthy subjects the H-reflex was modulated in consistency with a task dependent control. In the spastic patients the H-reflex lacked a task dependent modulation. In consistency with earlier findings it was suggested that the decreased modulation could have been caused by decreased control of the pre-synaptic inhibition of the Ia terminals or a change in recruitment gain. To test if the stretch reflex behaved as the H-reflex, the short latency stretch reflex was investigated during walking. Here we found that the stretch reflex was strongly modulated during a step in healthy subjects as seen for the H-reflex, but when comparing the str","PeriodicalId":75395,"journal":{"name":"Acta neurologica Scandinavica. Supplementum","volume":"170 ","pages":"1-28"},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20334065","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The impact of aging on cognitive functions. An 11 year follow-up study of four age cohorts. 衰老对认知功能的影响。一项为期11年的四组年龄组随访研究。

Acta neurologica Scandinavica. Supplementum Pub Date : 1997-01-01

P Laursen

{"title":"The impact of aging on cognitive functions. An 11 year follow-up study of four age cohorts.","authors":"P Laursen","doi":"","DOIUrl":"","url":null,"abstract":"The literature on longitudinal studies of aging and cognitive performance is reviewed. The review reveals some ambiguity which seems primarily to be due to selection bias in the study groups and insufficient statistical modelling and parameterization. The main purpose of this study was to analyze the impact of aging on cognitive performance of the general adult population. In addition, the following problems are considered: If an aging impact is found, is it then evenly distributed across different age cohorts and different cognitive functions? Is the effect of different subject-related and situational factors on the test parameters stable over time? Is it possible to eliminate the impact of the examiner in cognitive testing? Moreover, do certain background factors such as age (generation), sex, schooling, etc. or test performance in an earlier examination have predicting power for the participation at a later stage in the study? The analysis was made using a longitudinal design with four successive age cohorts born in 1952, 1942, 1932, and 1922. 1,026 subjects were examined in 1982-83 and 711 were re-examined in 1993-94. At both occasions the subjects were tested by means of the Cognitive Function Scanner method. Attrition was found in all four age cohorts but most profound in the oldest cohort. Attrition occurred most frequently among subjects with only primary schooling and low social status. Age (generation), Sex, Schooling, Occupational Activity Status, Smoking Status, Psychic Stress, and questionnaire positive Cardiovascular Disease in the 1982-83 study all had significant relation to non-participation in the follow-up, either because of death, refusal to participate or because the subjects did not turn up on the agreed date for examination. Also a few test parameters, primarily in the attention tests and concentration tests, were found to be significantly related to non-participation in the follow-up. The results of the follow-up study, in which each subject was his own reference, showed two different tendencies. One tendency indicated some decline in performance. It was found in parameters for non-verbal learning and memory, retention of verbal memory, visuomotor and visuospatial speed, concentration, and reaction time. The other tendency indicated some improvement in performance in relation to verbal learning and memory, visuomotor and visuospatial precision, and to visual perception. It was a general tendency that performance becomes more scattered with increasing age. The follow-up study showed that Generation, Sex, and Schooling are the most important subject-related factors to take into consideration in the evaluation of test results. The significant impact of the Generation factor indicates that cognitive performance depends not only on aging but is also modulated to a large extent by generation specific factors. In spite of intensive training and special focus on communication it was evident that the situational Examiner fact","PeriodicalId":75395,"journal":{"name":"Acta neurologica Scandinavica. Supplementum","volume":"172 ","pages":"7-86"},"PeriodicalIF":0.0,"publicationDate":"1997-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"20395866","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effect of Xenon. 氙的影响。