独立分量分析在脑电信号处理中的应用及研究进展

独立分量分析(independent component analysis,ICA)方法是从一组观测信号中提取统计独立分量的方法.因为用这种方法分解出的各信号分量之间是相互独立的,而测得的脑电信号往往包含若干相对独立的成分,所以用它来分解脑电信号,所得的结果更具有生理意义,有利于去除干扰和伪差.本文简要地回顾了ICA的发展历史和主要算法,综述了它在脑电信号处理中的应用及研究进展,并指出了需要进一步研究解决的问题.     

视觉刺激下基于“是-否”状态的脑电信号分类研究

目的为了探究脑机接口中脑电信号与判断认知心理活动之间的识别问题,本文在视觉刺激诱发实验设计中采用文字和图片结合的方式进行脑电分类研究以期提高识别率。方法通过设计视觉刺激诱发判断认知脑电实验采集到15名受试者在"是"或"否"状态下的脑电信号,经过预处理和事件相关扰动(event-related spectral dynamics,ERSP)特征分析,运用经验模式分解(empirical mode decomposition,EMD)优化共空间模式(common spatial pattern,CSP)的特征提取算法进行分类识别。首先,利用EMD对预处理后的脑电信号进行有效的固有模态函数(intrinsic mode function,IMF)频段筛选;其次,使用CSP滤波器进行滤波提取特征向量;最后,使用支持向量机(support vector machine,SVM)进行分类识别,并对测试组进行检验。结果经过EMD-CSP优化滤波后进行SVM分类正确率可达8897%,相比单独利用CSP进行特征提取下的SVM分类结果提高了约5%。结论 EMD-CSP优化滤波方法对判断认知脑电识别的可行性和有效性,为进一步开发脑机接口应用产品提供认知参考依据。     

基于固有模态分解和深度学习的抑郁症脑电信号分类分析

以采集到的抑郁症患者和正常人的脑电信号为基础,采用固有模态分解算法对原始信号去噪处理,通过卷积神经网络对抑郁症患者和正常人进行分类分析。首先通过脑电信号的采集实验,采集15位抑郁症患者和15位正常人对照组Fp1的静息态脑电信号;之后对采集到的静息态脑电进行去噪处理,脑电去噪处理主要包括固有模态分解算法对原始信号的分解获得不同层次的IMF分量,对IMF分量进行频域分析,通过硬阈值的方法剔除原始信号中的噪声信号;最后采用卷积神经网络对抑郁症患者和正常人对照组进行二值分类,结果相较于传统的特征提取-机器学习算法,分类准确率明显提高。     

基于IMF能量熵的脑电情感特征提取研究

为提高脑电信号情感识别分类准确率,结合经验模态(EMD)分解和能量熵提出一种新的脑电特征提取方法。本研究主要介绍了EMD分解的基本原理,分析了传统EMD算法中的"端点效应",采用分段幂函数插值算法改善了EMD分解的精度和性能,然后将改进后的算法应用到脑电信号特征提取,获取脑电信号的IMF分量后计算出IMF能量熵作为情感识别的特征,最后通过分类实验对比改进后的EMD算法和传统EMD算法对脑电情感特征的分类准确率。实验结果显示改进的EMD算法能使识别率提高15%左右,并且以IMF能量熵为特征的平均识别率在80%以上,实验结果表明将IMF能量熵用于脑电信号情感识别是可行的。     

运动意识脑电的动态独立分量分析

研究了用独立分量分析方法进行运动意识脑电信号特征分析的可行性。提出了用峭度极大动态独立分量分析方法进行μ节律提取的新思想。通过对批处理ICA算法和动态ICA算法在运动意识脑电特征分析的结果比较,得出了动态ICA算法更适合于运动意识脑电特征分析和提取。研究中发现,动态ICA混合矩阵系数的时间波形能准确即时地反映受试者进行左右手运动想象时运动神经皮层的μ节律变化,这一结果对脑认知和脑—机接口研究具有较大的实际意义,为独立分量分析方法在事件相关电位(ERP)特征提取中的应用提供了新的思路。     

基于SSVEP的无线脑-机接口系统研究与实现

针对目前脑-机接口存在的成本高、普及面窄、体积笨重等问题,开发基于稳态视觉诱发电位(SSVEP)的无线脑-机接口系统,并对脑电信号特征提取算法进行研究。脑电采集设备采用锂电池供电,通过无线方式传送数据到上位机进行数据处理。上位机软件对接收的信号进行滤波预处理,并基于小波变换的典型相关分析法(WT-CCA)对信号特征提取及处理,甄别视觉诱发刺激类型。对10名测试者分别测试15组数据,结果表明该系统成功获取含有特征信息的脑电信号,经过上位机处理后被外部机器人识别的准确率达90%以上。这一脑-机接口系统技术成本低、准确率高、便携可穿戴,对残障人士修复运动功能和感觉功能具有重要的应用价值,也促进脑机交互技术的普及和发展。     

基于EMD的左右手运动想象脑电信号分析研究

基于经验模态分解(EMD)理论,提出一种左右手运动想象脑电信号分析方法.首先利用时间窗对脑电信号数据进行划分,对每段数据通过经验模态分解法将其分解为一组固有模态函数IMF,提取主要信号所在的IMF层去除信号中的噪声.对含有主要信号的几层IMF进行Hilbert变换,得到瞬时频率与对应的瞬时幅值.再提取左右手想象的特定频段mu节律和beta节律的能量信号作为特征,分别利用支持向量机(SVM)和Fisher进行了分类比较.对EMD和小波包在去噪和特征提取进行了比较.结果表明,EMD是一种很有效的去噪方法,经过EMD分解后提取的能量信号在区分左右手想象上更具有优势,识别率高.     

基于HHT的生物电阻抗胃动力信号分析方法

目的 采用HHT时间序列分析方法处理从人体采集到的胃动力信号.方法 通过经验模态分解(EMD)技术将一非线性、非稳态过程的原始胃动力序列分解为一组内在模态函数(IMFs),对每一个IMF进行Hilbert 变换,得到信号的瞬时频率,然后选择与胃动力相关的频率成分,即0.03-0.06 Hz之间的IMF进行重构提取胃动力...     

基于经验模态分解自适应滤波的胎儿心电信号提取

目的提出了一种基于经验模态分解自适应滤波的胎儿心电信号提取法。方法首先利用经验模态分解算法对孕妇腹部信号进行分解得到一组内模函数(IMF),然后将这组IMF作为自适应滤波器的主输入信号,并将孕妇胸部信号作为参考输入信号。通过学习算法自适应组合IMF,滤除母体心电信号成分,从而提取胎儿心电信号。结果与结论基于仿真和临床的实验结果表明,该方法提取的胎儿心电信号误差小,性能优于传统的最小均方和归一化最小均方自适应滤波算法。     

用于控制短消息发送的实时脑机接口系统

目的：设计一种基于视觉诱发电位的实时脑机接口,用于控制短消息发送。方法：实时脑机接口系统由视觉刺激器、脑电采集电路、FPGA开发板、通讯模块组成。脑机接口界面包括短消息发送的目标选项和内容选项界面,受试者每次实验注视刺激界面中的一个模块,通过检测视觉诱发脑电来确定受试者做出的选择。利用基于FPGA的VGA视觉刺激器为受试者提供视觉刺激,采集脑电信号并在FPGA平台上对其进行在线的实时分析处理。选用小波分解提取视觉诱发电位特征向量,输入BP神经网络进行模式识别,产生脑机接口控制信号,其中,小波分解和BP神经网络两部分由NIOS II实现。脑机接口控制命令用于控制TC35无线模块发送短消息。结果：通过对五名受试者做实验,识别准确率最高可以达到100%,脑机接口系统能有效控制短消息的发送。采用小波滤波、BP神经网络识别的算法优于时域波形匹配识别法。结论：实验表明本文提出的实现脑机接口短消息发送系统的方法具有可行性。     

Renal dysplasia and asplenia in two sibs

A family is reported in which two sibs, one male and the other female, both died within 24 hours of birth with enlarged polycystic kidneys. Postmortem histology in the second child showed gross renal dysplasia. In both children the pancreas was enlarged, nodular and cystic but the liver appeared macroscopically normal. In the second child, histological examination confirmed pancreatic fibrosis with cystic dilation of ducts, but showed portal fibrosis with bile duct proliferation in the liver.
This combination of findings is very reminiscent of those in a girl and her brother reported by Ivemark et al. (1959). The children reported here also showed absence or hypoplasia of the spleen, cardiac anomalies and other features of the Ivemark syndrome (Ivemark 1955), a quite different, usually sporadic, congenital disorder. It is suggested that the children described here have a distinct lethal congenital disorder, probably inherited in an autosomal recessive manner.     

Schizophrenia in a North Swedish geographical isolate, 1900–1977. Epidemiology, genetics and biochemistry

Over 200 schizophrenic patients belonging to three major and interrelated pedigree complexes have been investigated over the past 30 years in a North Swedish geographically isolated population, presently numbering about 6,000. An intensive investigation of a number of biochemical correlates and genetic markers in a few selected families belonging to one of the major pedigrees has indicated new strategies for the current research program.
Schizophrenia, as defined operationally, is significantly associated with decreased activities of two enzymes (1) blood platelet monoamine oxidase, (2) plasma dopamine-β-hydroxylase, and (3) with the genetic marker Gc² (group specific antigen). Both enzymes are subject to genetic variation. A positive score for linkage between schizophrenia and low plasma DBH activity has been calculated, but, so far, available data are insufficient for discrimination between linkage and partial contribution of genetically controlled low plasma DBH to the pathogenesis of the disease. Alternatively, both mechanisms could be involved.
As a model for continued research, schizophrenia is explained as based on a double dominant-recessive genotype (Aabb), representing a vulnerability which in about 50 % of cases develops into clinical schizophrenia. It is suggested that the dominant mutation (A) operates on or affects MAO activity, and that the recessive genotype (bb) is instrumental in low variates of DBH activity and very likely such variates within the normal range of physiological variation. Moreover, it is suggested that the combined effects of MAO- and DBH-reduced efficiency on the metabolism of e.g. dopamine could be an essential pathogenic mechanism for the schizophrenic illness which is segregating in this population.     

The dominant diseases of modernized societies as omega-3 essential fatty acid deficiency syndrome: Substrate beriberi

About 1900, modern food selection and processing caused widespread $\text{epidemics}$ of the B vitamin deficiency diseases of beriberi and pellagra which, for genetic reasons, often expressed as different diseases ranging from bowel and heart disease to dermatoses and psychoses. But the B vitamins merely help convert essential fatty acids (EFA) into the prostaglandin (PG) tissue regulators and it now turns out that, through hydrogenation, milling and selection of w3-poor southern foods, we have also been systematically depleting, by as much as 90%, a newly discovered trace Nordic EFA (w3) of special importance to primates and sole precursor of the PG3(4) series, even as a concurrent fiber deficiency increases body demand for EFA. Since substrate EFA is processed by many B vitamin catalysts, an EFA deficiency will mimic a $\text{panh}$ypovitaminosis B, i.e., a mixture of $\text{substrate}$ beriberi and $\text{substrate}$ pellagra resembling vitamin beriberi and pellagra but exhibiting as even more diverse $\text{endemic}$ disease. This would consitute a second stage of the Modern Malnutrition and explain why some workers now hold the dominant diseases of modermized societies to be new, nutritionally based, pellagraform yet lipid-related and to range, once again, from heart disease to psychosis. It is an assumption that our dominant diseases are unrelated to each other or are merely revealed by our diagnostic acumen and therapeutic success; and that hydrogenating millions of tons of food oils annually, to destroy the rancidity producing w3-EFA, is safe for $\text{primates}$. Extensive beriberiform disease is reported here in 32 typical cases taken from medical practice which responds strikingly to linseed oil supplements (60% w3-EFA) in confirmation of identical results in Capuchins.     

What will studies of Fulani individuals naturally exposed to malaria teach us about protective immunity to malaria?

There are an estimated over 200 million yearly cases of malaria worldwide. Despite concerted international effort to combat the disease, it still causes approximately half a million deaths every year, the majority of which are young children with Plasmodium falciparum infection in sub-Saharan Africa. Successes are largely attributed to malaria prevention strategies, such as insecticide-treated mosquito nets and indoor spraying, as well as improved access to existing treatments. One important hurdle to new approaches for the treatment and prevention of malaria is our limited understanding of the biology of Plasmodium infection and its complex interaction with the immune system of its human host. Therefore, the elimination of malaria in Africa not only relies on existing tools to reduce malaria burden, but also requires fundamental research to develop innovative approaches. Here, we summarize our discoveries from investigations of ethnic groups of West Africa who have different susceptibility to malaria.     

'Very sore nights and days': the child's experience of illness in early modern England, c.1580-1720

Sick children were ubiquitous in early modern England, and yet they have received very little attention from historians. Taking the elusive perspective of the child, this article explores the physical, emotional, and spiritual experience of illness in England between approximately 1580 and 1720. What was it like being ill and suffering pain? How did the young respond emotionally to the anticipation of death? It is argued that children’s experiences were characterised by profound ambivalence: illness could be terrifying and distressing, but also a source of emotional and spiritual fulfilment and joy. This interpretation challenges the common assumption amongst medical historians that the experiences of early modern patients were utterly miserable. It also sheds light on children’s emotional feelings for their parents, a subject often overlooked in the historiography of childhood. The primary sources used in this article include diaries, autobiographies, letters, the biographies of pious children, printed possession cases, doctors’ casebooks, and theological treatises concerning the afterlife.     

Guidelines for the Validation and Use of Immunoassays for Determination of Introduced Proteins in Biotechnology Enhanced Crops and Derived Food Ingredients

Recent advancements in agricultural biotechnology have created a need for analytical techniques to determine introduced proteins in crops enhanced through modern biotechnology techniques. These proteins are expressed in plant tissues and may be present in food ingredients. Immunoassays are ideally suited for protein detection and may be used as both quantitative and threshold methods. Microplate ELISA and lateral flow devices are two of the most commonly used immunoassay formats for agricultural biotechnology applications. This paper provides general background information and a discussion of criteria for the validation and application of immunochemical methods to the analysis of proteins introduced into plants and food ingredients using biotechnology methods. It is the result of a collaborative effort of members of the Analytical Environmental Immunochemical Consortium. This collaborative effort represents the combined expertise of several organizations to reach consensus on establishing guidelines for the validation and use of immunoassays. Further, the paper offers developers and users a consistent approach to adopting the technology as well as aid in producing accurate and meaningful results.     

HLA in North Colombia Chimila Amerindians

HLA-A,-B,-C,-DRB1 and -DQB1 alleles have been studied in Chimila Amerindians from Sabana de San Angel (North Colombian Coast) by using high resolution molecular typing. A frequent extended haplotype was found:HLA-A*24:02-B*51:10-C*15:02-BRB1*04:07-DQB1*03:02 (28.7%) which has also been described in Amerinndian Mayos Mexican population (Mexico, California Gulf, Pacific Ocean). Other haplotypes had already been found in Amerindians from Mexico (Pacific and Atlantic Coast), Peru (highlands and Amazon Basin), Bolivia and North USA. A geographic pattern according to HLA allele or haplotype frequencies is lacking in Amerindians, as already known. Also, five new extended haplotypes were found in Chimila Amerindians. Their HLA-A*24:02 high frequencies characteristic is shared with aboriginal populations of Taiwan; also, HLA-C*01:02 high frequencies are found in New Zealand Maoris, New Caledonians and Kimberly Aborigines from Australia. Finally, this study may show a model of evolutionary factors acting and rising one HLA allele frequency (-A*24:02), but not in others that belong to the same or different HLA loci.     

Ultracryotomy: development and application (with examples from the yeast cytology) (author's transl)

The preparation steps usually necessary for obtaining ultrathin frozen sections of biological material (chemical prefixation, enclosing, cryoprotective treatment, freezing, sectioning, and post-staining the sections for transmission electron microscopy) are submitted to a critical analysis. The application of cryo-ultramicrotomy, in particularly for cytochemical purposes, is reviewed. Fundamental considerations of chemical prefixation and poststaining are supported by examples from yeast cytology. Furthermore, the efficiency of the cryo-ultramicrotomy (electron optical resolution of ultrastructural details) is demonstrated on yeast cells and protoplasts.     

The universal muscular chamber. A basic unit of the genitourinary, cardiovascular, gastro-intestinal, skeletal, cutaneous, respiratory and other systems, endocameral hypertension; and spasm, the key to their idiopathic diseases and arthropathies

Starting with the integument, we see many organs are contractile sacs or multiples thereof, which tubes or bags constitute the major part of the entire body. Recognition of this basic unit and its characteristics sheds new light, individually and collectively, on many disorders previously considered unrelated. Muscular tears and perforations develop in the walls of these chambers, being no way peculiar to those organs, wherein, hydrochloric acid occurs. So, it is not necessary to explain the absence of excessive acid from patients who exhibit holes in the gastric, uterine, aortic, duodenal, rectal, pulmonary, retina, and other walls. Muscle, not acid is the great common factor relating idiopathic disorders in the gastrointestinal tract to each other and to similar diseases in other systems. When the units are linked together, the lesions tend to appear as arthropathies, i.e. at the joints. Rephrasing common-place observations, frees us from conventional, conceptual cul-de-sacs. An observation is only as good as its interpretation, so all possibilities must be considered, otherwise, we will remain blinded by our misconceptions.