Observing the steady-state visual evoked potentials with a compact quad-channel spin exchange relaxation-free magnetometer

We observed the steady-state visually evoked potential(SSVEP) from a healthy subject using a compact quad-channel potassium spin exchange relaxation-free(SERF) optically pumped magnetometer(OPM). To this end, 30 s of data were collected, and SSVEP-related magnetic responses with signal intensity ranging from 150 fT to 300 f T were observed for all four channels. The corresponding signal to noise ratio(SNR) was in the range of 3.5–5.5. We then used different channels to operate the sensor as a gradiometer. In the specific case of detecting SSVEP, we noticed that the short channel separation distance led to a strongly diminished gradiometer signal. Although not optimal for the case of SSVEP detection, this set-up can prove to be highly useful for other magnetoencephalography(MEG) paradigms that require good noise cancellation.Considering its compactness, low cost, and good performance, the K-SERF sensor has great potential for biomagnetic field measurements and brain-computer interfaces(BCI).

Influence of stimuli color on steady-state visual evoked potentials based BCI wheelchair control

In recent years, Brain Computer Interface (BCI) systems based on Steady-State Visual Evoked Potential (SSVEP) have received much attention. This study tries to develop a SSVEP based BCI system that can control a wheelchair prototype in five different positions including stop position. In this study four different flickering frequencies in low frequency region were used to elicit the SSVEPs and were displayed on a Liquid Crystal Display (LCD) monitor using Lab-VIEW. Four stimuli colors, green, red, blue and violet were used to investigate the color influence in SSVEPs. The Electroencephalogram (EEG) signals recorded from the occipital region were segmented into 1 second window and features were extracted by using Fast Fourier Transform (FFT). One-Against-All (OAA), a popular strategy for multiclass SVM, is used to classify SSVEP signals. During stimuli color comparison SSVEP with violet color showed higher accuracy than that with green, red and blue stimuli.

Variation of the Multifocal Visual Evoked Potential with Eccentricity in Isometropic Amblyopes

Purpose: To investigate the variation of visual function in different eccentricities of the visual field in isometropic amblyopes.Method: The stimulus matrix containing 61 hexagons was generated on a monitor. The diameter of the entire stimulating field was approximately 13.6 deg of arc; the frame rate of the monitor was 67 Hz. Every hexagon of the display contained a number of black and white small hexagonal patches which reversed during stimulation. These hexagons were simultaneously but independently modulated in time by the controlling computer program. The flashed elements were selected differently on each frame according to a computer-generated binary pseudo-random time series (m-sequence); the response contributions from each of the individual stimulus elements could be extracted from the cross corre-ation function. Subjects were asked to maintain fixation at the center of the stimulus pattern while each of the hexagons of the display reversed. The VERB system extracted the local responses by

A Secure Cryptographic System Based on Steady-State Visual Evoked Potential Brain-Computer Interface Technology

Addressing the vulnerability of contact-based keyboard password systems to disclosure,this paper proposes and validates the feasibility of a non-contact secure password system based on brain-computer interface(BCI)technology that detects steady-state visual evoked potential(SSVEP)signals.The system first lets a testee look at a digital stimulus source flashing at a specific frequency,and uses a wearable dry electrode sensor to collect the SSVEP signal.Secondly,a canonical correlation analysis method is applied to analyze the frequency of the stimulus source that the testee is looking at,and feeds back a code result through headphones.Finally,after all password codes are input,the system makes a judgment and provides visual feedback to the testee.Experiments were conducted to test the accuracy of the system,where twelve stimulus target frequencies between 10-16Hz were selected within the easily recognizable flicker frequency range of human brain,and each of them was tested for 12 times.The results demonstrate that this SSVEP-BCI-based system is feasible,achieving an average accuracy rate of 97.2%,and exhibits promising applications in various domains such as financial transactions and identity recognition.

Review of brain-computer interface based on steady-state visual evoked potential

The brain-computer interface(BCI)technology has received lots of attention in the field of scientific research because it can help disabled people improve their quality of life.Steady-state visual evoked potential(SSVEP)is the most researched BCI experimental paradigm,which offers the advantages of high signal-to-noise ratio and short training-time requirement by users.In a complete BCI system,the two most critical components are the experimental paradigm and decoding algorithm.However,a systematic combination of the SSVEP experimental paradigm and decoding algorithms is missing in existing studies.In the present study,the transient visual evoked potential,SSVEP,and various improved SSVEP paradigms are compared and analyzed,and the problems and development bottlenecks in the experimental paradigm are finally pointed out.Subsequently,the canonical correlation analysis and various improved decoding algorithms are introduced,and the opportunities and challenges of the SSVEP decoding algorithm are discussed.

Studying the Effect of the Pre-Stimulation Paradigm on Steady-State Visual Evoked Potentials with Dynamic Models Based on the Zero-Pole Analytical Method

This study explored methods for improving the performance of Steady-State Visual Evoked Potential(SSVEP)-based Brain-Computer Interfaces(BCI), and introduced a new analytical method to quantitatively analyze and reflect the characteristics of SSVEP. We focused on the effect of the pre-stimulation paradigm on the SSVEP dynamic models and the dynamic response process of SSVEP, and performed a comparative analysis of three pre-stimulus paradigms(black, gray, and white). Four dynamic models with different orders(second-and third-order)and with and without a zero point were used to fit the SSVEP envelope. The zero-pole analytical method was adopted to conduct quantitative analysis on the dynamic models, and the response characteristics of SSVEP were represented by zero-pole distribution characteristics. The results of this study indicated that the pre-stimulation paradigm affects the characteristics of SSVEP, and the dynamic models had good fitting abilities with SSVEPs under various types of pre-stimulation. Furthermore, the zero-pole characteristics of the models effectively characterize the damping coefficient, oscillation period, and other SSVEP characteristics. The comparison of zeros and poles indicated that the gray pre-stimulation condition corresponds to a lower damping coefficient, thus showing its potential to improve the performance of SSVEP-BCIs.

Effect of background luminance of visual stimulus on elicited steady-state visual evoked potentials

Steady-state visual evoked potential(SSVEP)-based brain-computer interfaces(BCIs)have been widely studied.Considerable progress has been made in the aspects of stimulus coding,electroencephalogram processing,and recognition algorithms to enhance system performance.The properties of SSVEP have been demonstrated to be highly sensitive to stimulus luminance.However,thus far,there have been very few reports on the impact of background luminance on the system performance of SSVEP-based BCIs.This study investigated the impact of stimulus background luminance on SSVEPs.Specifically,this study compared two types of background luminance,i.e.,(1)black luminance[red,green,blue(rgb):(0,0,0)]and(2)gray luminance[rgb:(128,128,128)],and determined their effect on the classification performance of SSVEPs at the stimulus frequencies of 9,11,13,and 15 Hz.The offline results from nine healthy subjects showed that compared with the gray background luminance,the black background luminance induced larger SSVEP amplitude and larger signal-to-noise ratio,resulting in a better classification accuracy.These results suggest that the background luminance of visual stimulus has a considerable effect on the SSVEP and therefore has a potential to improve the BCI performance.

Brain-computer control interface design for virtual household appliances based on steady-state visually evoked potential recognition

Brain–computer interface is a new form of interaction between humans and machines.This interaction helps the human brain control or operate external devices directly using electroencephalograph(EEG)signals.In this study,we first adopt a canonical correlation analysis method to find the stimulation frequency by calculating the correlation coefficient between the EEG data and multiple sets of harmonics with different frequencies.Then,we select the maximum correlation coefficient as the stimulus frequency and consequently identify steady-state visual evoked potentials.Afterward,we introduce power spectral density to adjust the stimulus frequency and a voting mechanism to reduce the false activation rate.Finally,we build a virtual household electrical appliance brain–computer control interface,which achieves over 72.84%accuracy for three classification problems.

Visual Functions and TraceElement Metabolism in Tobacco-toxic Optic Neuropathy

Visual functions and nutrition metabolic characteristics werestudied in 8 subjects(16 eyes)with tobacco-toxic optic neuropathy(TTON).Their visual functions tested by psychophysical and electrophysiologicmethods showed that:1.central vision diminished in 16 eyes,2.dyschromatopsias were found in 14 tested eyes,3.bilateral symmetricalcentral or cecocentral scotomas were the visual field characteristics in allcases,4.PVEP were severe abnormal in 3 spatial frequencies in all cases and56.3% of 15' checkboard ...

AB053.Oscillatory activity specific to peripheral emotional treatment induced by a visual steady state

Background:Research suggests that the analysis of facial expressions by a healthy brain would take place approximately 170 ms after the presentation of a facial expression in the superior temporal sulcus and the fusiform gyrus,mostly in the right hemisphere.Some researchers argue that a fast pathway through the amygdala would allow automatic and early emotional treatment around 90 ms after stimulation.This treatment would be done subconsciously,even before this stimulus is perceived and could be approximated by presenting the stimuli quickly on the periphery of the fovea.The present study aimed to identify the neural correlates of a peripheral and simultaneous presentation of emotional expressions through a frequency tagging paradigm.Methods:The presentation of emotional facial expressions at a specific frequency induces in the visual cortex a stable and precise response to the presentation frequency[i.e.,a steady-state visual evoked potential(ssVEP)]that can be used as a frequency tag(i.e.,a frequency-tag to follow the cortical treatment of this stimulus.Here,the use of different specific stimulation frequencies allowed us to label the different facial expressions presented simultaneously and to obtain a reliable cortical response being associated with(I)each of the emotions and(II)the different times of presentations repeated(1/0.170 ms=~5.8 Hz,1/0.090 ms=~10.8 Hz).To identify the regions involved in emotional discrimination,we subtracted the brain activity induced by the rapid presentation of six emotional expressions of the activity induced by the presentation of the same emotion(reduced by neural adaptation).The results were compared to the hemisphere in which attention was sought,emotion and frequency of stimulation.Results:The signal-to-noise ratio of the cerebral oscillations referring to the treatment of the expression of fear was stronger in the regions specific to the emotional treatment when they were presented in the subjects peripheral vision,unbeknownst to them.In addition,the peripheral emotional treatment of fear at 10.8 Hz was associated with greater activation within the Gamma 1 and 2 frequency bands in the expected regions(frontotemporal and T6),as well as desynchronization in the Alpha frequency bands for the temporal regions.This modulation of the spectral power is independent of the attentional request.Conclusions:These results suggest that the emotional stimulation of fear presented in the peripheral vision and outside the attentional framework elicit an increase in brain activity,especially in the temporal lobe.The localization of this activity as well as the optimal stimulation frequency found for this facial expression suggests that it is treated by the fast pathway of the magnocellular layers.

基于可穿戴式脑磁图的视觉混合脑机接口研究

新兴的可穿戴式脑磁图技术为脑机接口(BCI)提供高质量数据奠定了基础.为探究可穿戴式脑磁图应用于视觉混合BCI上的可行性,本文基于稳态视觉诱发场(SSVEF)和Alpha波设计了SSVEF-Alpha混合BCI,并在不同分类模型上进行了性能对比结果表明,基于用户依赖(UD)的训练方法,混合BCI6分类平均分类准确率为(93.29±1.69)%,信息传输速率可达86.81bits/min,且使用短数据长度进行用户独立(UI)的训练方法比免训练的方法更具优越性.本研究验证了视觉混合BCI的有效性,为进一步开发设计可穿戴式脑磁图的BCI应用产品提供参考范例.

An extended binary subband canonical correlation analysis detection algorithm oriented to the radial contraction-expansion motion steady- state visual evoked paradigm

The radial contraction-expansion motion paradigm is a novel steady-state visual evoked experimental paradigm,and the electroencephalography(EEG)evoked potential is different from the traditional luminance modulation paradigm.The signal energy is concentrated chiefly in the fundamental frequency,while the higher harmonic power is lower.Therefore,the conventional steady-state visual evoked potential recognition algorithms optimizing multiple harmonic response components,such as the extended canonical correlation analysis(eCCA)and task-related component analysis(TRCA)algorithm,have poor recognition performance under the radial contraction-expansion motion paradigm.This paper proposes an extended binary subband canonical correlation analysis(eBSCCA)algorithm for the radial contraction-expansion motion paradigm.For the radial contraction-expansion motion paradigm,binary subband filtering was used to optimize the weighting coefficients of different frequency response signals,thereby improving the recognition performance of EEG signals.The results of offline experiments involving 13 subjects showed that the eBSCCA algorithm exhibits a better performance than the eCCA and TRCA algorithms under the stimulation of the radial contraction-expansion motion paradigm.In the online experiment,the average recognition accuracy of 13 subjects was 88.68%±6.33%,and the average information transmission rate(ITR)was 158.77±43.67 bits/min,which proved that the algorithm had good recognition effect signals evoked by the radial contraction-expansion motion paradigm.

斜视性弱视儿童多焦视觉诱发电位的研究

目的:研究斜视性弱视多焦视觉诱发电位特征,探讨弱视发病机制。方法:采用德国Roland公司的RETIscan3.15多焦视觉电生理仪,记录和分析了斜视性弱视儿童80眼,外斜43眼内斜37眼,并与正常对照组儿童60眼作比较。结果:弱视眼N1-P1波振幅密度平均值和P1-N2波振幅平均值较正常组儿童在中央视野有下降,随离心度增加,这种现象呈下降趋势。P1波潜伏期平均值无明显异常。正常组和各斜视性弱视组N1-P1波振幅密度平均值:颞侧<鼻侧,P1波潜伏期平均值:颞侧>鼻侧。结论:斜视性弱视mfVEP中心区损害重于周边区,波形异常程度与弱视程度无关。内斜性弱视波形异常程度大于外斜性弱视。

视觉电生理与客观视功能检查

对视觉电生理在客观视功能检测中的应用进行了综述,主要是图形视觉诱发电位和扫描图形视觉诱发电位在客观视力测定,及多焦视觉诱发电位在客观视野检测中的应用。

非动脉炎性前部缺血性视神经病变的电生理及临床特征分析

目的研究非动脉炎性前部缺血性视神经病变(NAION)的电生理及临床特征。方法收集2013年3月至2014年3月我院确诊为NAION的17例患者28眼,分析其图形视觉诱发电位(PVEP)、荧光素眼底血管造影(FFA)、视野(VF)等临床检查特征。结果 28眼均行PVEP检查,其中21眼P100波幅值在1°或15'空间频率均出现不同程度降低。P100波峰时在1°空间频率5眼中度延迟(>15 ms),其余23眼未见明显延迟或者轻度延迟;15'空间频率时6眼中度延迟(>15 ms),其余22眼峰时未见明显延迟或者轻度延迟(<15 ms)。15患者23眼行FFA检查,其中6患者(40%)患者臂-视网膜循环时间(ART)大于15 s。7眼后期出现高荧光,其余后期呈低荧光。28眼均行视野检查,其中10眼正常,7眼视敏度降低或暗点(4眼集中在生理盲点附近),7眼呈现与生理盲点相连的缺损,4眼残存部分视野。对比分析PVEP和FFA,发现FFA后期高荧光的患眼P100波峰时呈中度以上延迟,后期低荧光患眼的峰时未见明显延迟或轻度延迟。对比分析PVEP和视野,发现14眼VF和PVEP均异常,7眼视野正常时PVEP异常,4眼PVEP正常时而VF异常。结论 NAION的PVEP的P100波峰时大多为正常或轻度延迟,当视乳头水肿、FFA后期视盘高荧光时P100波峰时明显延迟。FFA的ART延长不是NAION的敏感指标。PVEP对于视野正常的患眼有辅助诊断的价值。

垂体瘤患者神经眼科学检查分析72例

目的分析垂体瘤患者静态中心视野、视觉诱发电位及头磁共振成像(magnetic resonance imaging,MRI)检查结果的关系,探讨静态中心视野检查及视觉诱发电位检查在垂体瘤早期诊断及病情评估中的临床意义。方法选择2010年7月至2011年12月由我院神经外科确诊为垂体瘤的30～50岁患者72例(144眼),经头MRI强化检查显示瘤体均位于蝶鞍内或突破鞍隔向上生长。应用全自动视野分析仪24-2阈值程序进行静态中心视野检查,记录平均缺损(meandefect,MD)值,应用诱发电位仪进行图形翻转视觉诱发电位检查(pattern reserval visual evoked potential,PRVEP)。根据视野检查结果将患者分为4组:正常视野组9例;轻度缺损组13例(-5dB≤MD<0dB);中度缺损组38例(-15dB<MD<-5dB);重度缺损组12例(MD≤-15dB),采用单因素方差分析及q检验分析比较各组患者MRI正中矢状位、冠状位肿瘤的相对高度及PRVEPP100波潜伏期。结果患者视野异常以颞侧偏盲最多,此外可见不典型视野缺损。随着视野缺损程度的增加,MRI正中矢状位及冠状位肿瘤相对高度均增大(F=125.1,P<0.05;F=109.8,P<0.05),正常视野组为(0.9±0.3)cm/(0.7±0.2)cm,轻度缺损组为(1.1±0.4)cm/(0.8±0.2)cm,中度缺损组为(2.6±0.5)cm/(2.4±0.6)cm,重度缺损组为(3.9±0.4)cm/(3.8±0.4)cm。其中正常视野组与轻度缺损组比较,差异无统计学意义(q=1.49,P>0.05)。随着视野缺损程度的增加,PRVEPP100波潜伏期也呈逐渐延长趋势(F=23.5,P<0.05),正常视野组为(102.2±4.3)ms,轻度缺损组为(109.4±5.4)ms,中度缺损组为(114.5±4.8),至重度缺损组达(118.1±3.9)ms。根据MRI结果,垂体微腺瘤共11例,其中行静态中心视野检查异常率为27.3%,行PRVEP检查异常率达72.7%,差异具有统计学意义(χ2=4.55,P<0.05)。结论静态中心视野检查结果有助于垂体瘤的定性、定位诊断。视野缺损程度与垂体瘤所致视神经功能受损程度一致,且与头MRI所示瘤体大小相对应。对于垂体微腺瘤引起的视功能亚临床损害,PRVEP检查更为敏感,对垂体瘤的早期诊断具有重要价值。

多焦视觉诱发电位及其在青光眼中的应用

多焦视觉诱发电位(mVEP)近来在青光眼中多有介绍。较之传统的VEP,它具有更佳的空间定位能力,同时,相对于主观视野检查,因为没有学习曲线,更容易让患者接受。本文就mVEP的记录方法,正常人的mVEP及其在青光眼中的应用,特别是它与主观视野的关系作一综述。

多焦视觉诱发电位在客观视野评估的研究现状

视野检查是法医临床学视功能评估的重要指标之一。多焦视觉诱发电位(mVEP,multi-focalvisuale-vokedpotential)技术能精确、敏感、快速、客观地检测视野。笔者结合国内外文献,对mVEP的刺激、记录、分析方法及其在视野评定中的研究现状进行综述。

针药并用治疗视神经萎缩疗效观察

目的观察针药并用治疗视神经萎缩的临床疗效。方法 64例视神经萎缩患者88只眼,随机分为治疗组(33例46只眼)和药物组(31例42只眼)。药物组予以口服复方银杏胶囊、甲钴胺治疗,治疗组在药物组治疗的基础上联合针刺治疗。观察两组治疗前后视野MD值和视觉诱发电位(P-VEP)值变化,并比较两组临床疗效。结果治疗组总有效率为87.0%,对照组为59.5%,两组比较差异有统计学意义(P<0.05)。两组治疗后视野MD值和P-VEP值与治疗前比较,差异有统计学意义(P<0.05)。两组治疗后视野MD值和P-VEP值比较,差异有统计学意义(P<0.05)。结论针药并用可以改善视神经萎缩患者的视野和视觉诱发电位,效果显著。

超声乳化白内障吸除术和小切口非超声乳化囊外摘除术在高龄白内障患者中的疗效对比分析

目的对比分析超声乳化白内障吸除术和小切口非超声乳化囊外摘除术在高龄白内障患者中的疗效。方法将80例高龄白内障患者按照奇偶数字法随机均分为超声乳化白内障吸除术组与小切口非超声乳化囊外摘除术组,每组各40例。比较两组患者手术前后视力、散光度、视野缺损值、诱发电位振幅、诱发电位潜伏期及并发症发生率。结果 1两组患者术后视力较术前均显著改善(P均<0.05),观察组患者术后1周及术后1个月视力均显著优于对照组(P均<0.05),但两组患者术后3个月视力比较差异无显著性(P>0.05);2两组患者术前散光度数比较差异无显著性(P>0.05),术后1周、1个月、3个月两组患者散光度数比较差异无显著性(P>0.05);3超声乳化白内障吸除术组患者术后1个月及3个月、小切口非超声乳化囊外摘除术组患者术后1周、1个月及3个月视野较本组术前比较差异均具有显著性(P<0.05,P<0.01),且术后1周、1个月及3个月视野组间比较差异均具有显著性(P均<0.05);4两组患者术前诱发电位振幅、平均标准偏差模式组间比较差异均无显著性(P均>0.05);超声乳化白内障吸除术组患者术后1周、1个月、3个月诱发电位振幅、平均标准偏差模式均显著高于小切口非超声乳化囊外摘除术组,差异具有显著性(P<0.05,P<0.01);5超声乳化白内障吸除术组患者并发症发生率为27.50%,小切口非超声乳化囊外摘除术组为15.00%,比较差异具有显著性(P<0.05)。结论与超声乳化白内障吸除术相比,小切口非超声乳化囊外摘除术治疗高龄白内障疗效更加显著,安全性更高,值得临床推广应用。