听觉诱发电位提取方法的研究与分析

论述了运用小波变换进行听觉诱发电佗单次提取的原理、方法和实验分析。结果表明，对单次试验信号，经小波变换及相关分析后，可从带自发脑电干扰的信号中提取诱发电位信号。小波变换分析方法与传统的叠加平均方法相比，可减少试验次数，缩短检测周期。     

基于快速平稳小波变换的特征提取方法分析fMRI数据

多尺度特征提取方法( MFE)利用离散小波变换,通过只重构有用信号所在小波尺度的方式,有效去除了fMRI数据里的干扰成分.但部分尺度重构会导致混频发生,而离散小波变换的结果对小波选取比较敏感.为此,本研究把有用信号最低频率所对应的小波尺度选为舍弃尺度,利用平稳小波变换矩阵算法代替常规的逐体素算法,用sym2、syml0和sym20等3个小波分析了视觉组块型和事件相关型fMRI试验数据.结果显示,所选舍弃尺度的方法避免了混频现象,3个小波给出了相同的且比SPM8更好的分析结果.在时间消耗上,3个小波基于矩阵算法分析一个被试的组块型数据只耗时61 s,sym2基于逐体素算法耗时42 min,SPM8耗时63 s.因此,所提出的方法是一种实用性更强的MFE方法.     

ERP单次提取中的小波变换模极大值恢复算法

自发脑电的频谱不规则,与有效信号ＥＲＰ频谱相重叠,传统滤波方法难以奏效。但由于随机噪声奇异性指数与有效信号奇异性指数大小不一样,小波变换模极大值在不同尺度下传播行为也不一样,据此可将有效信号从随机噪声中提取出来。我们发现利用小波变换模极大值算法可以提取出单次ＥＲＰ,并将此方法用于１１名被试听觉的实时提取研究。     

基于小波变换的事件相关电位少次提取方法

本文以反映大脑稀少认知事件的相关电位P300为例,介绍了基于小波变换(wavelet transform,WT)进行事件相关电位(event related potential,ERP)少次提取的原理、仿真和实验结果.通过小波变换先去除与ERP混杂的EEG背景干扰,然后对消除干扰后的脑电数据进行重构和ERP波峰检测,在此基础上尝试修正ERP波峰的潜伏期时移,再通过小波重构获得通常需多次相干平均才能得到的ERP波形.仿真计算和实验数据分析结果说明小波分析具有较强的ERP峰值检测和潜伏期模式识别能力,值得进一步在临床工程中深入研究和应用推广.     

基于离散小波变换提取脑机接口中脑电特征

在脑机接口中，针对脑电特征提取利用单一种类信息、使用数据量大、分类性能较差等缺点，提出一种新颖的基于离散小波变换的方法。分析了小波变换特征提取的特点和特征表示方式，用Daubechies类db4小波函数对脑电信号进行6层分解，抽取小波变换各子带关键的部分逼近系数、小波系数、小波子带系数均值组成特征向量。以分类正确率为指标检验了提取特征的性能。实验结果表明，这种方法能够利用少量数据提取脑电信号本质特征，具有较高的分类性能，为利用脑电识别人的不同意图提供了快速而有效的手段。     

基于多分辨分析与连续小波变换提取和分析兔体感诱发电位

研究单次提取兔体感诱发电位,并定位和分析诱发电位波形成分。麻醉兔,以0.5Hz频率电脉冲刺激兔下肢隐神经,3764Hz采样率收集兔头皮电位。采用一维多分辨分析提取兔体感诱发电位,并用连续小波变换定位和分析诱发电位波形成分。单次诱发电位的小波变换与叠加平均诱发电位比较,表明Daubechies小波多分辨分析可以单次提取诱发电位。连续小波变换能够精确定位诱发电位中波形成分,并可采用连续小波变换分析诱发成分的频域特性。连续小波变换技术把一维时域信号投影到二维时频空间研究将成为医学信号处理的一个有用方法。     

测谎问题中的"情绪成分"对皮肤电反应的影响

目的：探讨测谎中个体情绪状态与皮肤电反应之间的关系，为改进测谎技术提供依据。方法：以38名大学生作为被试，以不同情绪激起程度的不良行为为素材进行测谎测试。结果：不同条件下被试皮肤电反应差异显著，其中高情绪激起问题和相关问题上的皮肤电反应更为强烈。结论：在一定的情景压力下，个体的情绪状态可以直接影响皮肤电活动；高情绪激起问题在鉴别说谎与诚实上，更加有效；除了说谎因素，测谎中测题本身所指向的事件就可以直接引起被试的情绪反应，从而产生皮肤电反应差异；当情景线索明确时，特定的目标事件更容易引起被试的关注，产生特殊的皮肤电反应。     

基于Morlet小波变换的EEG时频分析

Morlet小波变换是适用于EEG时频分析的一种比较成熟的方法，在国外的医学、心理学和认知神经科学研究中已被广泛使用。本文首先阐述了Morlet小波变换的基本原理和基于Morlet小波变换的时频分析方法的特点，然后利用此类方法对实际的EEG数据进行探索性的分析。     

小波分析理论在脑电分析中的应用

小波变换是一种把时间、频率（或尺度）两域结合起来的分析方法。它具有：（１）多分辨率；（２）相对带宽恒定；（３）适当地选择基本小波，可使小波在时、频两域都具有表征信号局部特征的能力的特点，被誉为“分析信号的显微镜”。本系统以Ｗｉｎｄｏｗｓ为操作系统平台，将小波变换用于脑电信号分析，实现病历管理，１００Ｈｚ脑电信号采样，１０分钟脑电数据存储等功能，是一个在Ｗｉｎｄｏｗｓ３．１下开发的脑电分析系统。从脑电信号小波变换后的波形可以看出，各尺度信号不仅反映信号的频率信息，同时也反映信号的时间信息，意即反映此时ＥＥＧ的状态。而传统的傅里叶分析只能获得信号的整体频谱，不能反映时域信息     

基于非负CP分解模型的边界规避任务中脑电特征提取方法研究

通过建立"碗-球"模型,执行有视觉引导的边界规避任务,以提高受试者的脑电唤醒度.在与"碗-球"模型交互过程中,采集10名健康被试关于左、右手两类运动任务的脑电数据,通过对脑电的优化特征进行分类,以实现对运动意图的解码.基于边界规避任务诱发的脑电信号进行8～13 Hz带通滤波,获得特定频带的数据,通过连续小波变换获取脑电...     

Neurocognitive sequelae of infants of diabetic mothers

On the basis of animal models, it was hypothesized that infants of diabetic mothers (IDMs) would be at risk for suffering damage to the hippocampus primarily because of fetal iron deficiency, chronic hypoxia, and hypoglycemia. This, in turn, may result in impairments in recognition memory at a young age. To test this model, the memory of 6-month-old IDMs and control infants was evaluated with electrophysiological (event-related potential [ERP]) and behavioral (looking time) measures. At 12 months, the Bayley Scales of Infant Development was administered. Our ERP measures showed robust evidence consistent with memory deficits in the IDMs. In contrast, the looking time measures and the Bayley exam failed to distinguish between the groups. From these results it was concluded that the ERP, but not the behavioral, measures are able to detect, in an at-risk population, deficits in recognition memory that are thought to be mediated by damage to the hippocampus.     

The influence of stimulus duration on odor perception.

Although different parameters are known to alter the shape of olfactory event related potentials (ERP), ERP parameters are generally thought to be independent from stimulus duration. Evidence from recent studies investigating trigeminal ERP indicates that this may not be true. Aim of the present study was to investigate the relationship of stimulus duration and ERP. A total of 20 young healthy subjects participated. Subjects were investigated on 5 occasions on 5 different days. ERP were recorded to olfactory stimuli of two different concentrations and 3 different durations (100 ms, 200 ms, 300 ms). In two sessions olfactory ERP to PEA were recorded, in another two sessions H2S was applied. During the same sessions, intensity ratings were recorded. In the fifth session, subjects were asked to rate the duration of H2S stimuli and PEA stimuli. Whereas at weak stimulus concentrations no effect of stimulus duration could be observed, there was a clear effect of "duration" in ERP amplitudes following stimuli with higher concentrations: the longer the stimulus duration the larger the ERP amplitudes. No effect was found on ERP latencies. With regard to intensity ratings, strong stimuli and longer lasting stimuli lead to higher ratings. Similarly, ratings of stimulus duration were dependent from stimulus concentration and stimulus duration. Results of the present study showed that similar to trigeminal ERP, information about stimulus duration is encoded in olfactory ERP, mainly in amplitudes.     

Influence of task difficulty on the features of event-related potential during visual oddball task

We present a comprehensive analysis of the change in event-related potential (ERP) due to task difficulty during a visual oddball task. Specifically, we investigated the inter-subject difference in difficulty-related change of ERP patterns using single-trial ERP analysis focusing on P300 and P2 components. ERPs were recorded and analyzed from 14 subjects while performing a visual oddball task with two difficulty levels. After extracting independent components (ICs) from single-trial ERPs, the averaged ERPs were used to identify which ICs originated from major ERP components. The ERP components were estimated from single-trial waveforms by back-projecting relevant ICs onto scalp electrodes after removing all other ICs; thus, the comparison of ERP components could be performed for each subject. The averaged P300 amplitude was smaller and latency was larger for the more difficult task, and this tendency was also observed for single-trial ERP analysis within each subject. P2 amplitude increased for the hard task for both group and individual analyses, suggesting that the P2 may be interpreted as a manifestation of task relevance evaluation or response generation. The P2 amplitude and latency were more notably correlated with response time for the more difficult task.     

Prestimulus EEG amplitude determinants of ERP responses in a habituation paradigm

Evidence for the nature and extent of the prestimulus EEG contributions to ERP determination has been mounting, and we have recently mapped these within an equiprobable auditory Go/NoGo task. Here we examined if the pattern of relationships in the Go/NoGo would generalise to an auditory habituation paradigm. Count and No-task conditions were assessed, and we predicted broadly corresponding effects between Go and Count, and NoGo and No-task conditions. Single-trial data were obtained at the midline sites (Fz, Cz, Pz). Prestimulus EEG in each of the traditional bands was quantified using a sliding FFT window, and five ERP components were manually identified. The corresponding EEG and ERP data were then correlated across subjects, sites, and trials, separately for each ERP component measure (amplitude, latency), task condition (Count, No-task), and EEG band (delta, theta, alpha, beta). Despite the substantial paradigm and methodological differences, 10 of the 17 expected prestimulus EEG–ERP directional relationships (i.e., direct or inverse effects) were confirmed across the traditional bands and ERP components, and only one was in the opposite direction. Importantly, 18 additional relationships reached significance here; these occurred across the EEG bands, and ERP components. Together these findings confirm the significant contributions of prestimulus EEG to subsequent ERP responses. These appear to be at least partially independent of the paradigm and EEG methodology employed, suggesting that there is merit in mapping these contributions further. Our findings also indicate the improved sensitivity of the statistical approach used here in detecting such EEG–ERP relationships.     

基于共空间模式和支持向量机算法的食物偏好脑电分类研究

研究不同食物偏好图片刺激所引起的脑电信号差异,提出一套用于分类识别的方法。18名受试者对5类食物进行评分后,参与oddball事件相关电位(ERP)实验。根据受试者评分决定其喜爱程度高和喜爱程度低的食物,并用相应图片刺激,采集受试者面对两类刺激时所诱发的ERP信号,分析两类信号在ERP成分上是否存在显著差异。利用共空间模式算法(CSP)进行特征提取,随后使用支持向量机(SVM)进行单试次脑电分类识别,并使用留一法进行交叉验证。结果表明,喜爱程度高和低食物图片刺激诱发的P3幅值在统计学上存在显著差异(P<0.05),振幅分别为(16.74±5.85)μV和(14.67±4.37)μV,相关分析结果表明食物评分与脑电P3幅值存在正相关。分类识别上,在使用4次单试次ERP信号下,CSP+SVM分类正确率可达93.16%±8.93%,取得了较好的分类识别结果。实验结果表明,脑电信号可作为一种新的食物偏好分析工具,CSP+SVM可对食物偏好脑电进行较好地识别,可为食物评价和厌食症辅助治疗等提供新的解决思路。     

癫癎患者听觉事件相关电位的检测报告

目的:探讨听觉事件相关电位(ERP)在癫癎患者中的应用价值。方法:对40例癫癎患者和30名正常人进行ERP检测比较,并将癫癎患者ERP的结果与其发作类型、用药情况等进行比较分析。结果:40例癫癎患者的ERP P300潜伏期较对照组延长(P<0．05),但其P300波幅差异无统计学意义(P>0．05)。全身强直阵挛性发作的28例癫癎患者,P300潜伏期延长尤著。多药治疗组较单药治疗组P300潜伏期延长。结论:癫癎患者存在认识功能障碍,ERP可作为癫癎患者认知功能障碍诊断的参考指标,对指导临床,及早给予干预和治疗有一定意义。     

结合小波分解和径向基神经网络进行事件相关电位的单次提取

从单次实验记录中提取事件相关电位，无论在临床诊断上还是在大脑高级功能的研究中都起着重要的作用。介绍了一种将小波多分辨率分解和重建与径向基神经网络结合起来进行事件相关电位单次提取的方法。它基于事件相关电位主要是低频信号的事实，发挥径向基神经网络对连续函数的逼近能力，从信号的小波分解系数中提取出与低频响应相关的成分，构造了一种新的时频域滤波的方法，实验表明本方法较好地从单次记录中提取出了事件相关电位。     

1539例精神疾患的事件相关脑电位定性分析

目的：分析事件相关电位在精神科疾病中的异常检出率及主要临床检查病种。方法：对1539例申请事件相关电位检查患者的P300、P50和CNV结果进行定性分析,分析其异常检出率并统计其检查病种。结果：本组精神疾患P300、P50、CNV的异常检出率分别为54.5%、61.5%和60.1%。临床申请作ERP检查的前三位病种分别是慢性精神分裂症偏执型、复发性抑郁症、首发精神分裂症（阴性症状为主）。结论：高密度脑电图及ERP新技术较适合精神科和心理学,值得进一步推广。     

基于小波和卡尔曼平滑的事件相关电位单次提取

本研究提出一种事件相关电位单次提取方法,可有效减少实验次数,并可探索实验之间ERP的变异性。此方法基于小波和卡尔曼平滑,首先利用小波变换考察ERP平均信号的时频特性,根据ERP不同分量出现的时间位置,在不同尺度上选取特定的单次实验ERP小波系数构成观测向量,其为真实ERP小波系数状态向量与噪声之和,然后对观测向量进行卡尔曼平滑,最后对卡尔曼平滑后的小波系数进行小波重构,得到单次提取的ERP信号。仿真实验表明,基于小波和卡尔曼平滑的方法不仅信噪比提高约16~18 dB,优于30次叠加平均、简单小波方法和基于高斯基函数的卡尔曼滤波方法,还可以跟踪ERP的幅度趋势变异性。与基于高斯基函数的卡尔曼滤波方法相比,所提方法降低了计算量。真实脑电ERP提取实验表明本方法较好地从单次记录中提取出了事件相关电位,并可解释ERP因适应和应激引起的趋势变异性。     

Contributions of prefrontal cortex to recognition memory: electrophysiological and behavioral evidence.

To clarify the involvement of prefrontal cortex in episodic memory, behavioral and event-related potential (ERP) measures of recognition were examined in patients with dorsolateral prefrontal lesions. In controls, recognition accuracy and the ERP old-new effect declined with increasing retention intervals. Although frontal patients showed a higher false-alarm rate to new words, their hit rate to old words and ERP old-new effect were intact, suggesting that recognition processes were not fundamentally altered by prefrontal damage. The opposite behavioral pattern was observed in patients with hippocampal lesions: a normal false-alarm rate and a precipitous decline in hit rate at long lags. The intact ERP effect and the change in response bias during recognition suggest that frontal patients exhibited a deficit in strategic processing or postretrieval monitoring, in contrast to the more purely mnemonic deficit shown by hippocampal patients.