Exploring Motor Imagery EEG: Enhanced EEG Microstate Analysis with GMD-Driven Density Canopy Method

The analysis of microstates in EEG signals is a crucial technique for understanding the spatiotemporal dynamics of brain electrical activity.Traditional methods such as Atomic Agglomerative Hierarchical Clustering(AAHC),K-means clustering,Principal Component Analysis(PCA),and Independent Component Analysis(ICA)are limited by a fixed number of microstate maps and insufficient capability in cross-task feature extraction.Tackling these limitations,this study introduces a Global Map Dissimilarity(GMD)-driven density canopy K-means clustering algorithm.This innovative approach autonomously determines the optimal number of EEG microstate topographies and employs Gaussian kernel density estimation alongside the GMD index for dynamic modeling of EEG data.Utilizing this advanced algorithm,the study analyzes the Motor Imagery(MI)dataset from the GigaScience database,GigaDB.The findings reveal six distinct microstates during actual right-hand movement and five microstates across other task conditions,with microstate C showing superior performance in all task states.During imagined movement,microstate A was significantly enhanced.Comparison with existing algorithms indicates a significant improvement in clustering performance by the refined method,with an average Calinski-Harabasz Index(CHI)of 35517.29 and a Davis-Bouldin Index(DBI)average of 2.57.Furthermore,an information-theoretical analysis of the microstate sequences suggests that imagined movement exhibits higher complexity and disorder than actual movement.By utilizing the extracted microstate sequence parameters as features,the improved algorithm achieved a classification accuracy of 98.41%in EEG signal categorization for motor imagery.A performance of 78.183%accuracy was achieved in a four-class motor imagery task on the BCI-IV-2a dataset.These results demonstrate the potential of the advanced algorithm in microstate analysis,offering a more effective tool for a deeper understanding of the spatiotemporal features of EEG signals.

Macrostate and Microstate of EEG Spatio-Temporal Nonlinear Dynamics in Zen Meditation

Macrostate and microstate characteristics of interregional nonlinear interdependence of brain dynamics are investigated for Zen-meditation and normal resting EEG. Evaluation of nonlinear interdependence based on nonlinear dynamic theory and phase space reconstruction is employed in the 30-channel electroencephalographic (EEG) signals to characterize the functioning interactions among different local neuronal networks. This paper presents a new scheme for exploring the microstate and macrostate of interregional brain neural network interactivity. Nonlinear interdependence quantified by similarity index is applied to the phase trajectory reconstructed from multi-channel EEG. The microstate similarity-index matrix (miSIM) is evaluated every 5 millisecond. The miSIMs are classified by K-means clustering. The cluster center corresponds to the macrostate SIM (maSIM) evaluated by conventional scheme. Zen-meditation EEG exhibits rather stationary and stronger interconnectivity among frontal midline regional neural oscillators, whereas resting EEG appears to drift away more often from the midline and extend to the inferior brain regions.

基于马尔可夫转移概率的意识障碍识别研究

意识障碍可分为最小意识状态和植物状态,目前对两类患者的区分主要基于行为量表的方法,但仍存在40%的误判率,脑电信号可以作为临床诊断的辅助工具.微状态可以反应大脑潜在认知机制的时空信息,探讨较短且具有平稳性微状态序列的低阶马尔可夫性质鲜少研究.基于18名意识障碍患者的静息态脑电信号,在具有平稳性的时间尺度上(60 s)对微状态序列进行分割,然后计算状态转换序列的一阶马尔可夫和二阶马尔可夫转移概率,得到两类意识障碍患者具有统计学差异的转移模式,并将差异模式作为特征进行交叉验证,最高得到92%的分类准确率.结果表明:意识障碍患者的统计差异模式更倾向于转向C状态和D状态,一阶马尔可夫比二阶马尔可夫具有更好的分类效果.上述结果为区分两类意识障碍患者以及医疗领域的微状态研究提供了新方法.

癫痫EEG信号相空间重构参数的计算和分析

根据癫痫发作过程中,EEG信号表现出来的发作间期和发作期2种不同的状态,通过分析发现在该过程中大脑动力系统存在不同的动力学嵌入空间,存在不同的吸引子。还应用伪邻点法、互信息法和C-C方法进行了推导和仿真,对2种不同状态进行相空间重构,确定了癫痫病人不同状态EEG不同吸引子的参数,并在此基础上提出了若干新的见解。

基于EEG熵值的驾驶员脑力负荷水平识别方法

为了对驾驶员脑力负荷予以有效识别,基于脑电信号指标构建了一种驾驶员脑力负荷识别方法.对驾驶员脑电信号进行快速傅里叶变换（FFT）,选取θ（4~8 Hz）,α（8~13 Hz）,β（13~30 Hz）3个频段的频谱幅值分别进行熵处理,对所得到的熵值作为脑力负荷识别参数,并对识别参数进行Kruskal-Wallis检验,选取差异最为显著的10项参数作为脑力负荷特征指标,在此基础上结合BP模型构建了驾驶员脑力负荷识别模型.基于驾驶模拟器实验数据,模型识别正确率为87.8%~90.4%.结果表明,该模型对驾驶员脑力负荷识别具有较高准确性,可实现不同驾驶员脑力负荷的有效识别,为未来自动辅助驾驶系统构建及车载信息系统优化设计提供算法依据.

巅峰式神经反馈训练提升射击表现效果和无应答者特性分析

为探索神经反馈训练在提升射击表现方面的应用效果和训练过程中的无应答者特性,开展一项用于提升射击表现的神经反馈训练(neurofeedback training for sport performance,SP-NFT)实验研究,招募20名受试者,进行2周4次的“巅峰”范式SP-NFT,采集受试者前、后测隐显目标射击表现和相关脑电(electroencephalograph,EEG)数据,检验SP-NFT对射击表现的提升效果、静息态EEG特征、SP-NFT期间正常组和无应答组EEG特性变化情况。结果表明:受试者后测射击成绩显著高于前测(P<0.01),静息态theta频带功率显著降低(P<0.01);相对正常受试者,无应答者在SP-NFT期间的努力程度更高,theta频段功率和SMR功率的变化程度更低,SP-NFT能够有效提升受试者射击表现,进一步揭示了无应答者的相关生理机制。研究成果为用于提升射击表现的SP-NFT技术进一步发展提供理论支撑和实验证据。

一种EEG信号盲分离和分类的神经网络方法

提出一种采用多神经网络处理脑电 (EEG)信号的方法。首先 ,对混有噪声的脑电信号给出一种盲分离的自适应神经算法。通过寻求采样时间序列线性组合的kurtosis系数的局部极值 ,得出该算法的模型和步骤。在盲分离的基础上 ,对分离出的估计信号进一步利用Kohonen网络进行分类。将该算法用于 30 0个EEG样本处理 ,并给出处理结果。

电离辐射对人脑影响的脑电信号分析

目的空间辐射是影响航天员健康、工效的重要环境要素。本研究探索辐射对脑电信号的影响规律,以期为深入研究辐射对中枢神经系统(脑)损伤作用提供参考。方法采集放疗志愿者接受射线辐射前后的静息态脑电信号(EEG),通过频谱分析、非线性动力学特征分析、相关系数和微状态分析等方法,研究辐射对EEG的影响规律。结果辐射诱导EEG频谱出现“慢波化”现象,重心频率、样本熵和复杂度下降,疲劳指标上升。EEG微状态C的平均持续时间和频率下降,微状态A与微状态C的平均相关系数上升,微状态D的平均持续时间下降。结论辐射导致神经元兴奋性下降,可能影响认知脑网络和大脑注意力。本研究可为辐射对中枢神经系统(脑)损伤研究提供依据。

基于脑电微状态的虚拟现实晕动症研究

针对脑电节律能量无法反映时间信息且对空间信息的探讨并不充分等问题,通过运用微状态分析方法,对虚拟现实晕动症(vRMS)相关脑电信号的时空模式进行了研究,从而检测虚拟现实晕动症。使用多元变分模态分解(MVMD)将脑电信号划分为从低频到高频的5个频段,分析了脑电微状态的出现频率、平均持续时间、覆盖率以及转换率的变化,最后利用统计分析和分类方法验证这些特征的有效性。研究结果表明,5个频段融合所有特征的分类准确率达到最大值83.9%。因此,微状态方法可望为研究VRMS提供新思路。

基于微状态的抑郁症静息态脑电信号分析

抑郁症(MDD)患者存在认知功能障碍,但其瞬时神经异常活动尚未研究清楚,对此采用脑电(EEG)微状态方法对抑郁症患者的脑电数据进行研究。比较22名抑郁症患者和25名正常人的128导闭眼脑电数据微状态特征,进行差异性分析并探索与量表得分之间的相关性。结果发现,相对于健康对照组,抑郁症患者微状态C的出现次数和涵盖比更高,且与其他微状态之间的转换概率较高,而其微状态D的平均持续时间较低,且与微状态B之间的转换次数减少。此外,微状态C和微状态D与抑郁量表和焦虑量表均呈显著相关性,表明基于脑电微状态方法可以捕捉到抑郁症患者异常大脑动态特性,为抑郁症临床早期诊治提供客观参考。

基于GRNN的可穿戴式脑电仪EEG疲劳检测

针对单电极可穿戴式脑电仪的脑电波信号(EEG)的疲劳状态智能识别,进行了基于广义回归神经网络(GRNN)的疲劳状态检测的研究。首先,通过调查问卷调查用户主观疲劳量,结合疲劳检测手环实现EEG数据的疲劳等级标记以建立数据集;其次,采用数据清洗等方式实现数据预处理并提取数据的时域特征、频域特征;运用主元分析进行特征降维;然后,建立GRNN疲劳识别模型并计算识别准确率;同时以支持向量机(SVM)方法作为对比实验检验模型效果;最后,以建立好的GRNN模型进行疲劳检测。研究发现,GRNN模型下EEG疲劳状态识别准确率最高为88.1%,相比SVM模型更高,对于EEG的疲劳状态的检测具有更好的稳定性和区分度。

基于EEG微状态方法的视觉想象识别研究

运动想象MI是基于想象的脑机交互BCI中常用的任务,但MI不易习得和控制,且存在“BCI盲”现象,使得该类BCI的实用化受限。针对较易习得和控制的视觉想象VI任务进行识别,旨在构建基于VI的BCI(VI-BCI)。招募了15名被试者参加2种动态图像的视觉想象任务并采集脑电EEG数据;然后采用EEG微状态方法研究了这2种VI任务诱发的EEG在微状态时间参数上的差异,并选用差异显著的微状态时间参数构建特征向量;最后采用SVM对2类VI任务进行识别。结果显示提取微状态特征所取得的最高、最低和平均分类精度分别为90%,56%和80.6±2.58%。表明微状态方法可以有效提取VI相关EEG特征并得到具有可比性的分类精度,可望为构建相对较新的在线VI-BCI提供思路。

Multi-Modal Domain Adaptation Variational Autoencoder for EEG-Based Emotion Recognition

Traditional electroencephalograph(EEG)-based emotion recognition requires a large number of calibration samples to build a model for a specific subject,which restricts the application of the affective brain computer interface(BCI)in practice.We attempt to use the multi-modal data from the past session to realize emotion recognition in the case of a small amount of calibration samples.To solve this problem,we propose a multimodal domain adaptive variational autoencoder(MMDA-VAE)method,which learns shared cross-domain latent representations of the multi-modal data.Our method builds a multi-modal variational autoencoder(MVAE)to project the data of multiple modalities into a common space.Through adversarial learning and cycle-consistency regularization,our method can reduce the distribution difference of each domain on the shared latent representation layer and realize the transfer of knowledge.Extensive experiments are conducted on two public datasets,SEED and SEED-IV,and the results show the superiority of our proposed method.Our work can effectively improve the performance of emotion recognition with a small amount of labelled multi-modal data.

Seizure detection using earth movers' distance and SVM in intracranial EEG

Seizure detection is extremely essential for long-term monitoring of epileptic patients. This paper investigates the detection of epileptic seizures in multi-channel long-term intracranial electroencephalogram （iEEG）. The algorithm conducts wavelet decomposition of iEEGs with five scales, and transforms the sum of the three frequency bands into histogram for computing the distance. The proposed method combines a novel feature called EMD-L1, which is an efficient algorithm of earth movers＇ distance （EMD）, with support vector machine （SVM） for binary classification between seizures and non-sei- zures. The EMD-LI used in this method is characterized by low time complexity and high processing speed by exploiting the L~ metric structure. The smoothing and collar technique are applied on the raw outputs of SVM classifier to obtain more ac- curate results. Several evaluation criteria are recommended to compare our algorithm with other conventional methods using the same dataset from the Freiburg EEG database. Experiment results show that the proposed method achieves a high sensi- tivity, specificity and low false detection rate, which are 95.73 %, 98.45 % and 0.33/h, respectively. This algorithm is char- acterized by its robustness and high accuracy with the possibility of performing real-time analysis of EEG data, and may serve as a seizure detection tool for monitoring long-term EEG.

基于脑电EEG信号的分析分类方法

随着脑科学与生物医学工程研究的不断深入,脑电信号的分析方法发展迅速。脑电信号的分析分类处理主要包含脑电信号预处理、特征提取和分类识别3个阶段,而每个阶段具有各种不同的处理方法,通过对不同阶段的分类处理方法进行分析,侧重关注现代脑电信号的预处理、特征提取和分类识别的重要内容及处理方法。

Cross-task emotion recognition using EEG measures: first step towards practical application

Electroencephalographic(EEG)-based emotion recognition has received increasing attention in the field of human-computer interaction(HCI)recently,there however remains a number of challenges in building a generalized emotion recognition model,one of which includes the difficulty of an EEG-based emotion classifier trained on a specific task to handle other tasks.Lit-tle attention has been paid to this issue.The current study is to determine the feasibility of coping with this challenge using feature selection.12 healthy volunteers were emotionally elicited when conducting picture induced and videoinduced tasks.Firstly,support vector machine(SVM)classifier was examined under within-task conditions(trained and tested on the same task)and cross-task conditions(trained on one task and tested on another task)for pictureinduced and videoinduced tasks.The within-task classification performed fairly well(classification accuracy:51.6%for picture task and 94.4%for video task).Cross-task classification,however,deteriorated to low levels(around 44%).Trained and tested with the most robust feature subset selected by SVM-recursive feature elimination(RFE),the performance of cross-task classifier was significantly improved to above 68%.These results suggest that cross-task emotion recognition is feasible with proper methods and bring EEG-based emotion recognition models closer to being able to discriminate emotion states for any tasks.

Comparison of Spatio-Spectral Properties of Zen-Meditation and Resting EEG Based on Unsupervised Learning

This paper reports distinct spatio-spectral properties of Zen-meditation EEG (electroencephalograph), compared with resting EEG, by implementing unsupervised machine learning scheme in clustering the brain mappings of centroid frequency (BMFc). Zen practitioners simultaneously concentrate on the third ventricle, hypothalamus and corpora quadrigemina touniversalize all brain neurons to construct a detached brain and gradually change the normal brain traits, leading to the process of brain-neuroplasticity. During such tri-aperture concentration, EEG exhibits prominent diffuse high-frequency oscillations. Unsupervised self-organizing map (SOM), clusters the dataset of quantitative EEG by matching the input feature vector Fc and the output cluster center through the SOM network weights. Input dataset contains brain mappings of 30 centroid frequencies extracted from CWT (continuous wavelet transform) coefficients. According to SOM clustering results, resting EEG is dominated by global low-frequency (<14 Hz) activities, except channels T7, F7 and TP7 (>14.4 Hz);whereas Zen-meditation EEG exhibits globally high-frequency (>16 Hz) activities throughout the entire record. Beta waves with a wide range of frequencies are often associated with active concentration. Nonetheless, clinic report discloses that benzodiazepines, medication treatment for anxiety, insomnia and panic attacks to relieve mind/body stress, often induce beta buzz. We may hypothesize that Zen-meditation practitioners attain the unique state of mindfulness concentration under optimal body-mind relaxation.

Online prediction of EEG based on KRLST algorithm

Kernel adaptive algorithm is an extension of adaptive algorithm in nonlinear,and widely used in the field of non-stationary signal processing.But the distribution of classic data sets seems relatively regular and simple in time series.The distribution of the electroencephalograph(EEG)signal is more randomness and non-stationarity,so online prediction of EEG signal can further verify the robustness and applicability of kernel adaptive algorithms.What’s more,the purpose of modeling and analyzing the time series of EEG signals is to discover and extract valuable information,and to reveal the internal relations of EEG signals.The time series prediction of EEG plays an important role in EEG time series analysis.In this paper,kernel RLS tracker(KRLST)is presented to online predict the EEG signals of motor imagery and compared with other 13 kernel adaptive algorithms.The experimental results show that KRLST algorithm has the best effect on the brain computer interface(BCI)dataset.

Epileptic Encephalopathies in Infants and Children: Study of Clinico-Electroencephalographic Spectrum in a Tertiary Hospital in Bangladesh

Background: The epileptic encephalopathies collectively exact an immense personal, medical, and financial toll on the affected children, their families, and the healthcare system. Objective: This study was aimed to delineate the clinical spectrum of patients with Epileptic encephalopathies (EEs) and classify them under various epileptic syndromes. Methods: This was a cross-sectional study that was carried out in the department of Neurophysiology of the National Institute of Neurosciences and Hospital, Bangladesh from July 2016 to June 2019. Children with recurrent seizures which were difficult to control and associated with developmental arrest or regression in absence of a progressive brain pathology were considered to be suffering from EE. Children under 12 years of age fulfilling the inclusion criteria were enrolled in the study. These patients were evaluated clinically and Electroencephalography (EEG) was done in all children at presentation. Based on the clinical profile and EEG findings the patients were categorized under various epileptic syndromes according to International League Against Epilepsy (ILAE) classification 2010. Results: A total of 1256 children under 12 years of age were referred to the Neurophysiology Department. Among them, 162 (12.90%) fulfilled the inclusion criteria. Most of the patients were male (64.2%) and below 1 year (37.7%) of age. The majority (56.8%) were delivered at the hospital and 40.1% had a history of perinatal asphyxia. Development was age-appropriate before the onset of a seizure in 38.9% of cases. Most (53.7%) of the patients had seizure onset within 3 months of age. Categorization of Epileptic syndromes found that majority had West Syndrome (WS) (37.65%) followed by Lennox-Gastaut syndrome (LGS) (22.22%), Otahara syndrome (11.73%), Continuous spike-and-wave during sleep (CSWS) (5.66%), Myoclonic astatic epilepsy (MAE) (4.94%), Early myoclonic encephalopathy (EME) (3.7%), Dravet syndrome (3.7%) and Landau-Kleffner syndrome (LKS) (1.23%). 9.26% of syndromes were unclassified. Conclusion: EEG was found to be a useful tool in the evaluation of Epileptic encephalopathies. The clinico-electroencephalographic features are age-related. Their recognition and appropriate management are critical.

睡眠呼吸暂停综合症患者脑电微状态发生改变

睡眠呼吸暂停综合症(SAS)是一种常见的睡眠障碍,传统上往往采用时频分析等方法研究其脑电信号的异常,都忽略了睡眠脑电的空间位置信息和特征的差异。采用微状态分析的方法,分别对健康人和SAS患者5个睡眠阶段(W、N1、N2、N3、REM)的脑电进行分析,探究SAS患者睡眠脑电特征在时间和空间上的差异。选取66名SAS患者和10名健康人的睡眠脑电,计算W-REM的全局场功率(GFP)并取GFP峰值数据进行聚类。得到4个微状态,这4个微状态地形图分别呈现为右额左后(A)、左额右后(B)、额枕中线(C)和额中线(D),并且计算微状态参数(出现频率、平均持续时间、覆盖率)。此外,还计算了微状态序列的静态属性[全局方差(GEV)],动态属性(熵率),转换概率和转移矩阵的对称性。最后,用Hurst指数来评估微状态序列的远程相关性。在W-REM阶段,健康人和SAS患者的出现频率、平均持续时间、覆盖率、GEV、转换概率、熵率、Hurst指数均存在显著差异(P<0.05)。转移矩阵均具有对称性(P>0.01)。Hurst指数均大于0.5,具有远程相关性。与健康人相比,SAS患者W-N3阶段微状态B、C的持续时间降低。SAS患者GEV的SUM大于健康人,说明SAS患者大脑活跃度更高。W-N3阶段健康人的Hurst指数逐渐减小,长期记忆减弱,而SAS患者从N1-N3阶段Hurst指数逐渐减小。每个睡眠阶段健康人的熵率都大于SAS患者,携带的脑电信息较少。