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一种新的人脑信息传输复杂性的研究 总被引:13,自引:4,他引:9
我们在过去的工作中曾用Kolmogrov复杂性(简称KC)来研究人脑信息传输的过程。但计算KC时需要对序列作粗粒化。粗粒化过程很容易丢失许多有意义的细节。为此,本文提出一种新的复杂性测度,即C0复杂性。我们认为复杂运动时间序列是由规则运动部分时间序列及随机运动部分时间序列组成的,因此C0复杂性就被定义为随机运动部分时序与时间轴所围区域的面积与整个复杂运动时序与时间轴所围区域面积之比。C0复杂性测度在计算过程中避免了粗粒化,因而较之KC等复杂性测度能更好反映序列的动力学性质。计算C0复杂性的关键是怎样从一复杂运动时序中找到规则部分时间序列。 相似文献
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基于高阶复杂性测度的心率变异信号分析 总被引:4,自引:0,他引:4
心率变异性反映了交感神经和迷走神经对心血管系统的综合调节作用,是评价心血管系统功能的重要指标。复杂度是描述时间信号序列信息量的一个重要参数,传统算法中的过分粗略化会丢失大量的有用信息,而高阶复杂度的引入可较大程度地避免这一问题。在利用Lorenz模型数据仿真的基础上,分别对25例正常人样本和25例充血性心力衰竭病人样本的心率变异信号的1~15阶Kolmogorov复杂度进行了计算,通过对比分析后确定,5阶Kolmogorov复杂度在临床医学上可以为分析心率变异信号获得更为理想的效果。 相似文献
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在分析DNA序列复杂度、预测基因编码区和非编码的DNA边界识别等问题中,以熵为基础构造的离散量度量提供了一种强有力的工具。为改进寻找水稻基因编码与非编码区边界的效率,本文提出了两个新的离散量度量(α-KL离散量与α-Jensen-Shannon 离散量),根据密码子的GC含量对氨基酸对应密码子构建了粗粒化向量。 比较了融合Jensen-Shannon 离散量、Jensen-Renyi 离散量、α-KL离散量和α-Jensen-Shannon 离散量等不同向量所获得的精度,结果表明,在对水稻基因编码区‘终止子’的识别效率上,构建的密码子粗粒化向量融合新引进的度量方法比Bernaola等人的方法(2000)提高了4~5倍。 相似文献
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局灶性脑缺血的早期无创诊断在临床实际中有着非常重要的意义。采用SD(Sparague-Dawley)大鼠建立了局灶性脑缺血的动物实验模型,记录了缺血前后缺血区域和正常区域的脑电信号EEG。由于近似熵复杂度算法所需时间序列长度较短,大大减少了脑电信号非平稳所带来的困难,且无需粗粒化,采用近似熵对局灶性缺血动物实验模型的脑电信号的复杂度进行了分析。结果发现缺血前后缺血与非缺血区域的近似熵均有着易于区分的特征,因此EEG信号的近似熵分析可以用于对局灶性缺血的脑损伤程度进行诊断,并区分损伤区域和非损伤区域,有望在临床中加以应用。 相似文献
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建立了一个急性高空缺氧实验模型,记录了四种不同高度条件下从缺氧前(正常呼吸)到缺氧后30分钟时的EEG,分析了其复杂度。发现缺氧引起复杂度明显变化,随时间和高度增加,一定程度缺氧可使EEG复杂度低于正常。表明EEG复杂度对脑缺氧较为敏感,可用于缺氧程度进行评估,有望成为临床诊断的一个指标。 相似文献
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已有的生理信号非线性分析仅研究了信号在单一采样频率下复杂度的差异.分析认为,可通过一个频率尺度因子寻找与生命活动密切相关的多重分形特性谱参数,该参数对生理、病理活动状态具有敏感性.通过小鼠药物实验模拟不同的生理和病理条件,研究并分析了健康小鼠与不同加药组小鼠心电图(electrocardiogram,ECG)信号的质量指数谱曲率随尺度因子分布,确定该信号复杂度最强、同时对疾病最敏感的特征频率范围,并得出心跳频率、心跳动力学复杂度以及ECG信号最敏感频率范围的内在联系.结果表明,在某一尺度因子范围内,小鼠ECG信号的质量指数谱曲率绝对值最大,并且这个最大值所在的尺度因子(或频率)范围不随计算的数据长度和最大粗粒化尺度因子的变化而改变.小鼠心率与其心跳动力学非线性复杂度之间并无直接联系,只与能够表达该动力学复杂度的ECG信号最敏感的频率范围有关.与心跳动力学复杂度有直接联系的是心脏健康状况,这两者在一定尺度因子范围内正相关.随着小鼠心跳频率升高,该ECG信号的敏感频率范围段也随之向高端移动. 相似文献
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Based on a complexity analysis of mutual information transmission of EEG developed by us [Xu J, Liu Z, Liu R, Yang Q (1997)
Physica D 106: 363–374], dynamic processes of the complexity of mutual information transmission in human brains were studied.
To diminish possible problems due to coarse graining preprocessing, some new measures of complexity were used. The results
show that, just before and after generalized seizures, the complexities of almost all information transmission between different
brain areas drop significantly; there is also a temporary decrease of complexity when subjects shift their attention. The
above facts suggest that there is a transient decrease of information transmission complexity when brain state changes occur
suddenly. Mental arithmetic tasks activate the left temporal lobe to exchange more information with other brain areas. The
results hint that the methods used here might be an approach to observe quick processes in the living brain.
Received: 14 October 1999 / Accepted in revised form: 24 March 2000 相似文献
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动态神经元网络模型的复杂性问题 总被引:1,自引:1,他引:1
在动态神经元网络模型中,当神经元总数仅为3时就观察到了非周期振荡。运用Lempel和Ziv提出的复杂性度量对这种现象进行了分析,结果表明对于其中一个神经元所发出的脉冲序列来说,至少直到1000个脉冲为止还不能发现任何的周期性,并且其复杂性可以和由logistic映射所产生的时间序列当其参数落在混沌区中时所具有的复杂性相比拟.这些结果也表明这种方法是所观察的时间范围内区分长周期振荡和非周期活动的好方法。结果还提示神经生理实验记录中所谓的噪声,其中有些可能是来源于生物神经元本身的非线性性质。 相似文献
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The objective of this study was to investigate whether the sensory performance of assessors in a sensory panel maybe explained by complexity of evaluated product. We aimed to investigate whether we could observe a decline in sensory performance when increasing the complexity of the product. The products increased in number of constituents from mixtures of sucrose, sodium chloride, citric acid and caffeine in water, to the foods ice tea and tomato soup constituting different levels of the same substances. Candidates who succeeded evaluating one product were not always successful evaluating others. Few subjects were successful in everything. The conclusion was that there is only minor systematic decline with increasing complexity of products. The authors emphasize that definition of complexity involves more than just counting number of constituents and taste sensations, and suggest that minor differences in the task given to the assessor might explain different performances.
Practical use of the research presented in the present paper is in a sensory evaluation context. It is important for the users of sensory data to find out how the profiling should be organized to achieve optimum output, and in specific, the need for extensive training when dealing with a more complex product. The present study hypothesized that sensory assessors would have more difficulties evaluating a more complex product. However, the results showed that panel leaders should be more concerned with the task variables in the sensory evaluation. Even a minor shift in task variables had a stronger impact on the performance and reliability of the assessors than increasing number of constituents and/or stimuli sensations of the product. This study did not demonstrate a need for extensive training when dealing with a more complex product as hypothesized. 相似文献
PRACTICAL APPLICATIONS
Practical use of the research presented in the present paper is in a sensory evaluation context. It is important for the users of sensory data to find out how the profiling should be organized to achieve optimum output, and in specific, the need for extensive training when dealing with a more complex product. The present study hypothesized that sensory assessors would have more difficulties evaluating a more complex product. However, the results showed that panel leaders should be more concerned with the task variables in the sensory evaluation. Even a minor shift in task variables had a stronger impact on the performance and reliability of the assessors than increasing number of constituents and/or stimuli sensations of the product. This study did not demonstrate a need for extensive training when dealing with a more complex product as hypothesized. 相似文献
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不同状态下脑电图复杂性探索 总被引:14,自引:2,他引:12
Lempel-Ziv所定义的有限序列的复杂性反映了给定序列随其长度的增长出现新模式的速率,事实上它反映了序列接近随机的程度。将该复杂性度量运用于脑电分析,旨在克服分数维方法的缺陷。文中计算了八种实验条件下脑电图的复杂度,涉及看、听、休息和心算等基本的大脑功能状态,13个被试的16导数据被用于计算分析.结果显示了复杂度在不同电极位置及实验条件下都有变化,睁眼状态的复杂度高于闭眼,而施加任务时有额部大脑活动区域复杂度降低的现象。同时复杂度也提供了一些研究大脑高级认知活动的新思路。 相似文献