Predictive spelling with a P300-based brain-computer interface: Increasing the rate of communication

This study compared a conventional P300 speller brain-computer interface (BCI) to one used in conjunction with a predictive spelling program. Performance differences in accuracy, bit rate, selections per minute, and output characters per minute (OCM) were examined. An 8×9 matrix of letters, numbers, and other keyboard commands was used. Participants (n = 24) were required to correctly complete the same 58 character sentence (i.e., correcting for errors) using the predictive speller (PS) and the non-predictive speller (NS), counterbalanced. The PS produced significantly higher OCMs than the NS. Time to complete the task in the PS condition was 12min 43sec as compared to 20min 20sec in the NS condition. Despite the marked improvement in overall output, accuracy was significantly higher in the NS paradigm. P300 amplitudes were significantly larger in the NS than in the PS paradigm; which is attributed to increased workload and task demands. These results demonstrate the potential efficacy of predictive spelling in the context of BCI.     

A submatrix-based P300 brain-computer interface stimulus presentation paradigm

The P300 event-related potential (ERP), with advantages of high stability and no need for initial training, is one of the most commonly used responses in brain-computer interface (BCI) applications. The row/column paradigm (RCP) that flashes an entire column or row of a visual matrix has been used successfully to help patients to spell words. However, RCP remains subject to errors that slow down communication, such as adjacency-distraction and double-flash errors. In this paper, a new visual stimulus presentation paradigm called the submatrix-based paradigm (SBP) is proposed. SBP divides a 6×6 matrix into several submatrices. Each submatrix flashes in single cell paradigm (SCP) mode and separately performs an ensemble averaging method according to the sequences. The parameter of sequence number is used to improve further the accuracy and information transfer rate (ITR). SBP has advantages of flexibility in division of the matrix and better expansion capability, which were confirmed with different divisions of the 6×6 matrix and expansion to a 6×9 matrix. Stimulation results show that SBP is superior to RCP in performance and user acceptability.     

Detection of P300 wave from EEG data for brain-computer interface applications

In this paper, successful detection of P300 wave embedded into electroencephalogram (EEG) data is aimed. Detection performance of a previously applied method is increased by using proper pre-processing scheme. Development in the detection performance in terms of overall classification accuracy is presented in a detailed manner. The proposed method is highly capable of detecting the minor differences and can be applied to various classification problems.     

用于脑-机接口P300实验的支持向量机分类方法

脑-机接口(BCI)技术利用脑电来实现无动作的人机交互.P300字符拼写范式是利用脑电信号实现文字选择输入的一种重要BCI实验范式,它通过对EEG中的P300信号的检测和识别,来推断试验对象(被试)对字母的注意选择.以2005年脑一机接口竞赛中的一组P300字符拼写实验数据为处理对象,采用支持向量机(SVM)的机器学习方法进行算法设计,对信号通道进行了筛选,并采用较少的EEG通道数据进行处理.另外,通过调整参与训练的数据集大小,扩大了v-SVM中参数v的取值范围,更有利于分类器设计.通过上述策略,提高了该BCI实验范式中的系统总体分类精度.上述方法对于测试集字符最佳识别正确率可达到89%,相比于我们参加该届竞赛时所用的线性分类器(LDA),字符识别正确率提高了3%.     

Light on! Real world evaluation of a P300-based brain-computer interface (BCI) for environment control in a smart home

Brain-computer interface (BCI) systems aim to enable interaction with other people and the environment without muscular activation by the exploitation of changes in brain signals due to the execution of cognitive tasks. In this context, the visual P300 potential appears suited to control smart homes through BCI spellers. The aim of this work is to evaluate whether the widely used character-speller is more sustainable than an icon-based one, designed to operate smart home environment or to communicate moods and needs. Nine subjects with neurodegenerative diseases and no BCI experience used both speller types in a real smart home environment. User experience during BCI tasks was evaluated recording concurrent physiological signals. Usability was assessed for each speller type immediately after use. Classification accuracy was lower for the icon-speller, which was also more attention demanding. However, in subjective evaluations, the effect of a real feedback partially counterbalanced the difficulty in BCI use. PRACTITIONER SUMMARY: Since inclusive BCIs require to consider interface sustainability, we evaluated different ergonomic aspects of the interaction of disabled users with a character-speller (goal: word spelling) and an icon-speller (goal: operating a real smart home). We found the first one as more sustainable in terms of accuracy and cognitive effort.     

Functional brain network and multichannel analysis for the P300-based brain computer interface system of lying detection

Deception is a complex cognition process which involves activities in different brain regions. However, most of the ERP based lie detection systems focus on the features of ERPs from few channels. In this study, we designed a multi-channel ERP based brain computer interface (BCI) system for lie detection. Based on this, two new EEG feature selection approaches, bootstrapped geometric difference (BGD) and network analysis were proposed and applied to feature recognition and classification system. Unlike other methods, our approaches focus on the changes of EEGs from different brain regions and the correlation between them. For the test, we focus on visual and auditory stimuli, two groups of subjects went through the test and their EEGs were recorded. For all subjects, BGD of the P300 for all the scalp electrodes combined with SVM classifier showed the average rate of recognition accuracy was 84.4% and 82.2% for visual and auditory modality respectively. Statistical analysis of network features indicated the difference in the two groups were significant and the average accuracy rate reached 88.7% and 83.5% respectively, and the guilty group showed more obvious small-world property than innocent group. The results suggest the BGD and network analysis based approaches combined with SVM are efficient for ERP based expert and intelligent system for detection and evaluation of deception. The combination of these methods and other feature selection approaches can promote the development and application of ERP based lie detection system.     

脑-机接口研究进展

作为当前神经工程领域中最活跃的研究方向之一,脑-机接口在生物医学、神经康复和智能机器人等领域具有重要的研究意义和巨大的应用潜力.近10年来,脑-机接口技术得到了长足的进步和飞速的发展,应用领域也在逐渐扩大.在已有相关工作的基础上,介绍脑-机接口系统的主要组成部分,对各组成部分常涉及到的相关基本理论和技术作了总结和介绍,主要包括脑信号获取、脑信号预处理、特征提取、变换算法等相关技术和理论,最后对脑-机接口未来的研究方向进行了展望.     

Mental workload during brain-computer interface training

It is not well understood how people perceive the difficulty of performing brain-computer interface (BCI) tasks, which specific aspects of mental workload contribute the most, and whether there is a difference in perceived workload between participants who are able-bodied and disabled. This study evaluated mental workload using the NASA Task Load Index (TLX), a multi-dimensional rating procedure with six subscales: Mental Demands, Physical Demands, Temporal Demands, Performance, Effort, and Frustration. Able-bodied and motor disabled participants completed the survey after performing EEG-based BCI Fitts' law target acquisition and phrase spelling tasks. The NASA-TLX scores were similar for able-bodied and disabled participants. For example, overall workload scores (range 0-100) for 1D horizontal tasks were 48.5 (SD = 17.7) and 46.6 (SD 10.3), respectively. The TLX can be used to inform the design of BCIs that will have greater usability by evaluating subjective workload between BCI tasks, participant groups, and control modalities. PRACTITIONER SUMMARY: Mental workload of brain-computer interfaces (BCI) can be evaluated with the NASA Task Load Index (TLX). The TLX is an effective tool for comparing subjective workload between BCI tasks, participant groups (able-bodied and disabled), and control modalities. The data can inform the design of BCIs that will have greater usability.     

A telepresence mobile robot controlled with a noninvasive brain-computer interface

This paper reports an electroencephalogram-based brain-actuated telepresence system to provide a user with presence in remote environments through a mobile robot, with access to the Internet. This system relies on a P300-based brain-computer interface (BCI) and a mobile robot with autonomous navigation and camera orientation capabilities. The shared-control strategy is built by the BCI decoding of task-related orders (selection of visible target destinations or exploration areas), which can be autonomously executed by the robot. The system was evaluated using five healthy participants in two consecutive steps: 1) screening and training of participants and 2) preestablished navigation and visual exploration telepresence tasks. On the basis of the results, the following evaluation studies are reported: 1) technical evaluation of the device and its main functionalities and 2) the users' behavior study. The overall result was that all participants were able to complete the designed tasks, reporting no failures, which shows the robustness of the system and its feasibility to solve tasks in real settings where joint navigation and visual exploration were needed. Furthermore, the participants showed great adaptation to the telepresence system.     

Abidirectional brain-computer interface for effective epilepsy control

Brain-computer interfaces （BCIs） can provide direct bidirectional communication between the brain and a machine. Recently, the BCI technique has been used in seizure control. UsuMly, a closed-loop system based on BCI is set up which delivers a therapic electrical stimulus only in response to seizure onsets. In this way, the side effects of neurostimulation can be greatly reduced. In this paper, a new BCI-based responsive stimulation system is proposed. With an efficient morphology-based seizure detector, seizure events can be identified in the early stages which trigger electrical stimulations to be sent to the cortex of the brain. The proposed system was tested on rats with penicillin-induced epileptic seizures. Online experiments show that 83% of the seizures could be detected successfully with a short average time delay of 3.11 s. With the therapy of the BCI-based seizure control system, most seizures were suppressed within 10 s. Compared with the control group, the average seizure duration was reduced by 30.7%. Therefore, the proposed system can control epileptic seizures effectively and has potential in clinical applications.     

基于AR模型的脑－机接口问题研究

在脑一机接口的研究中分类识别技术占有重要地位。将脑电信号中事件去同步化/相同步化现象作为特征信息,深入讨论基于AR模型的自适应算法（AAR）和多变量参数AAR模型算法（MVAAR）在脑电信号特征提取中的应用。结合三种分类器,对这两种算法进行了比较,实验证明两种方法的实验效果都很好,但是MVAAR算法比AAR算法能够达到更高的分类正确率,其阶次一般选取也比较低,数据仿真吻合度高,具有更强的通用性。     

Estimation of the SSVEP-based brain-computer interface performance

Brain-computer interface performance is estimated using a model based on the detection of steady-state visual evoked potentials (SSVEPs). It is established that the most significant parameters determining if the SSVEP-based brain-computer interfaces can be used in principle are the ratio of the number of samples in the analyzed signal to the sampling rate and the frequency range in which SSVEPs are detected. If it is necessary to identify the factors that limit the performance of the interface, then the ratio of the frequency range to the number of possible frequencies of the SSVEPs and the ratio of the number of samples in the analyzed signal to the sampling rate are significant predictors. The results presented in this paper make it possible to simulate parameters of brain-computer interfaces on the basis of requirements for a particular device and its capabilities. This makes it possible to design simpler hardware and software for specific tasks and reduce debugging time.     

非侵入式脑—机接口编解码技术研究进展

脑—机接口（brain-computer interface,BCI）系统通过采集、分析大脑信号,将其转换为输出指令,从而跨越外周神经系统,实现由大脑信号对外部设备的直接控制,进而用于替代、修复、增强、补充或改善中枢神经系统的正常输出。非侵入式脑—机接口由于具有安全性以及便携性等优点,得到了广泛关注和持续研究。研究人员对脑信号编码方法的不断探索扩展了BCI系统的应用场景和适用范围。同时,脑信号解码方法的不断研发极大地克服了脑电信号信噪比低的缺点,提高了系统性能,这都为构建高性能脑—机接口系统奠定了基础。本文综述了非侵入式脑—机接口编解码技术以及系统应用的最新研究进展,展望其未来发展前景,以期促进BCI系统的深入研究与广泛应用。     

基于Emotiv的脑机接口研究

针对脑机接口中存在的信号容易受到干扰、操作复杂的问题,利用经济便携式脑电采集设备Emotiv EPOC+搭载了一套基于稳态视觉刺激的脑机交互系统。该脑机接口系统首次将功率谱密度分析、典型相关性分析等方法按照不同权重相结合,使得目标识别的准确率高达98.6%,且该系统具有很高的抗噪能力和可拓展性。     

听觉脑–机接口的智能机器人控制系统

脑-机接口系统普遍存在控制命令单一、控制效率低和控制负担重等问题.通过改进控制目标的功能或加入智能化模块可以从一定程度上改善这个问题;但这方面的研究工作相对较少.如何针对残疾人的实际情况,研究智能控制与脑-机接口系统的有效切合点,是脑-机接口系统智能化的关键所在.本文针对视觉缺陷残疾人,提出一种结合机器视觉功能的听觉脑-机接口系统,将机器人自动视觉搜索,目标智能识别与听觉脑-机接口系统相结合,利用听觉脑-机接口系统向机器人发出简单人名指令,机器人将根据指令自动搜索识别,实现目标的自动跟踪.在一定程度上弥补视觉损伤病人在日常生活中的缺陷,也为脑-机接口的智能化提供了一个依据.     

Electroencephalogram-based brain-computer interface for the Chinese spelling system: a survey

Electroencephalogram (EEG) based brain-computer interfaces allow users to communicate with the external environment by means of their EEG signals, without relying on the brain’s usual output pathways such as muscles. A popular application for EEGs is the EEG-based speller, which translates EEG signals into intentions to spell particular words, thus benefiting those suffering from severe disabilities, such as amyotrophic lateral sclerosis. Although the EEG-based English speller (EEGES) has been widely studied in recent years, few studies have focused on the EEG-based Chinese speller (EEGCS). The EEGCS is more difficult to develop than the EEGES, because the English alphabet contains only 26 letters. By contrast, Chinese contains more than 11 000 logographic characters. The goal of this paper is to survey the literature on EEGCS systems. First, the taxonomy of current EEGCS systems is discussed to get the gist of the paper. Then, a common framework unifying the current EEGCS and EEGES systems is proposed, in which the concept of EEG-based choice acts as a core component. In addition, a variety of current EEGCS systems are investigated and discussed to highlight the advances, current problems, and future directions for EEGCS.     

Towards an EEG-based brain-computer interface for online robot control

According to New York Times, 5.6 million people in the United States are paralyzed to some degree. Motivated by requirements of these paralyzed patients in controlling assisted-devices that support their mobility, we present a novel EEG-based BCI system, which is composed of an Emotive EPOC neuroheadset, a laptop and a Lego Mindstorms NXT robot in this paper. We provide online learning algorithms that consist of k-means clustering and principal component analysis to classify the signals from the headset into corresponding action commands. Moreover, we also discuss how to integrate the Emotiv EPOC headset into the system, and how to integrate the LEGO robot. Finally, we evaluate the proposed online learning algorithms of our BCI system in terms of precision, recall, and the F-measure, and our results show that the algorithms can accurately classify the subjects’ thoughts into corresponding action commands.     

基于稳态视觉诱发电位的在线脑机接口研究

针对脑机接口中存在的抗噪声能力差、操作复杂的问题,利用便携式脑电采集设备Emotiv EPOC以及NAO机器人,搭建了一个抗噪能力较好的稳态视觉诱发在线脑机接口系统。该系统采用典型相关性分析进行稳态视觉诱发电位的频率识别。在线实验中受试者通过Emotiv控制NAO机器人运动,四类任务的准确率达到87.50%。在线实验没有回避周围的噪声,表明该系统具有较好的抗噪能力。