基于带参考信号的ICA算法的脑电信号眨眼伪差的分离研究

独立分量分析（ICA）是一种从混合信号中提取统计独立的分量的一种方法.本研究提出了一种基于带参考信号的ICA算法的脑电信号眨眼伪差的分离方法,可以得到纯净的脑电信号.这个方法的主要思路是：先选取一导眨眼伪差比较明显的数据,从中获得眨眼伪差的参考信号,再用ICA方法把眨眼伪差第一个提取出来,最后得到消除伪差后的EEG信号.详细讨论了使用带参考信号的ICA算法消除眨眼伪差的方法与步骤,并给出了应用于真实信号的实验结果.     

α频率光刺激脑电信号同步化的初步研究

研究α频率（8-13Hz）闪光刺激是否能引起人脑枕区同频率脑电信号的增加。采集15名正常志愿者在平静、光刺激状态下的脑电信号,利用脑地形图、小波分析和功率谱估计的方法对α频率光刺激前后的脑电信号进行处理,将归一化后的数据分为平静-激活组、男女对照组、两个不同电极位置组进行对比分析,对组间信号的差异进行了讨论,并对受试者精神状态的变化进行初步探讨。结果表明：周期性α频率光刺激能引起大脑枕区同频率脑电的显著增加。通过分析实验数据,初步得到了大脑在外部闪光刺激时脑电的变化规律,本实验结果对研究外部刺激对脑电的影响有一定的参考价值。     

药物依赖性实验自动控制系统

本文研究了药物依赖性实验的自动控制与测量系统,设计了实验动物的刺激信号产生,动物条件反射行为的自动检测和奖励食物的自动供给系统等部件和装置,将现有的复杂的人工操作和繁琐的数据统计工作,全部由计算机测控系统自动完成,该系统的实验样机已在中国药物依赖性研究所投入使用,达到设计性能要求。     

α频率光刺激脑电信号同步化的初步研究

研究α频率(8～13Hz)闪光刺激是否能引起人脑枕区同频率脑电信号的增加.采集15名正常志愿者在平静、光刺激状态下的脑电信号,利用脑地形图、小波分析和功率谱估计的方法对α频率光刺激前后的脑电信号进行处理,将归一化后的数据分为平静-激活组、男女对照组、两个不同电极位置组进行对比分析,对组间信号的差异进行了讨论,并对受试者精神状态的变化进行初步探讨.结果表明:周期性α频率光刺激能引起大脑枕区同频率脑电的显著增加.通过分析实验数据,初步得到了大脑在外部闪光刺激时脑电的变化规律,本实验结果对研究外部刺激对脑电的影响有一定的参考价值.     

基于扩展Infomax 独立分量分析算法的脑电信号消噪

背景：脑电信号能够反映大脑不同的生理病理状态,但在采集和分析处理过程中极易受到各种噪声的干扰,如眼球运动、眨眼、心电、肌电等,这些噪声的存在严重影响了脑电信号的分析和处理。 目的：介绍了一种基于扩展Infomax的独立分量分析方法,并用于脑电信号消噪。 方法：通过扩展Infomax算法的迭代求得分离矩阵,采用去除噪声分量后的独立成分重构需要记录的脑电信号,观察Matlab仿真得到的去噪后的脑电信号,同时比较去噪前后各导联脑电信号与眼电信号的相关性。 结果与结论：使用扩展Infomax 独立分量分析算法能够成功地去除多导脑电信号中的眼电干扰。再比较去噪前后各导联脑电信号的功率谱,可以发现使用扩展Infomax独立分量分析算法同时也能够成功地去除多导脑电信号中的工频干扰,且对脑电信号中的其他有用信号几乎没有破坏。     

基于Hermite滤波器的稳态视觉诱发电位背景标记Stroop效应包络分析

Stroop效应能够反映大脑对冲突干扰的注意。为了深入分析Stroop效应中大脑的认知活动过程,设计了稳态视觉诱发电位（SSVEP）背景标记的Stroop实验范式,记录同时含有事件相关电位（ERP）信号和SSVEP信号的脑电信号,并提出基于Hermite滤波器的脑电信号包络分析方法。采集了10例受试的脑电数据,分离得到ERP信号和SSVEP信号。在刺激后400～600 ms时间窗内,不一致条件的ERP信号比一致条件的ERP信号更负。条件之间的差异具有统计显著性,差异主要分布在前额区域,可视为Stroop效应在脑电上的体现。通过包络分析发现,SSVEP信号的包络在刺激后存在明显的下降过程。ERP信号Alpha频带总包络刺激之后的变化与其刺激之前的水平有关,若刺激之前Alpha频带总包络的水平较高,刺激之后包络先小幅上升后下降到比刺激前更低的水平;若刺激之前水平较低,刺激之后的包络上升后下降到与刺激前相当的水平。通过SSVEP背景标记Stroop实验范式和包络分析,可进一步研究Stroop效应的认知活动过程,也可为其他认知实验提供参照。     

基于脑-机接口技术的虚拟现实康复训练平台

对神经损伤的瘫痪病人进行功能恢复训练时应强调患者的主动参与。开发了一套基于脑-机接口技术的虚拟现实康复训练平台。该平台采用患者在想象运动时的脑电信号作为虚拟人运动的控制信号,从而把想象运动与运动功能恢复训练结合在一起。由于虚拟现实系统的实时性与沉浸感能给受试者提供较好的训练反馈信息,因此,使用本平台有望改善患者的训练效果。详细介绍了快速在线脑-机接口算法以及虚拟现实的实时交互技术,并提供了三名受试者的实测结果。初步实验证明了该平台设计的可行性。     

TMS线圈与EEG电极线相对位置对TMS-EEG信号的影响

通过分析经颅磁刺激线圈放电时的电场分布,探索磁刺激输出脉冲对脑电采集帽产生的伪迹信号来源。我们通过建立八字线圈感应电场分布的半无界空间数学模型,获得八字线圈感应电场的分布特性,分析磁刺激影响脑电采集回路的两种影响因素,我们用matlab软件仿真刺激线圈与脑电极线成不同角度、不同距离时产生的伪迹信号的变化趋势,通过模型试验和人体实验验证这种趋势的准确性;结果显示,脑电导线重合于线圈长轴,产生脑电伪迹最小,当线圈转动其他角度或当线圈下移时伪迹会逐渐增大,最大伪迹幅值是最小伪迹幅值的约10倍。在TMS-EEG试验中,伪迹信号的幅值、持续时间与线圈摆放位置、角度有关。通过实验前合理排布脑电极线可降低伪迹信号幅值、持续时间等参数,提高磁刺激下脑电信号特征信号提取的准确性。     

基于低频电刺激诱发表面肌电信号的肌肉疲劳度研究

目的 通过对肌肉疲劳过程中非诱发表面肌电(surface electromyography,sEMG)信号和诱发表面肌电信号的研究分析,寻找有效评价肌肉疲劳的分析测量方法.方法 对7名受试者进行自主运动和电刺激两种致肌疲劳的实验,并在两组实验中分别记录电刺激诱发与非诱发肌电信号,然后对每组信号进行傅里叶变换求取功率谱和近似熵.结果 随着疲劳的产生,两组实验诱发信号的频谱曲线左移效果优于非诱发信号,近似熵分析中电刺激组诱发信号出现先上升后下降的变化,自主运动组诱发信号则呈现单调递减的趋势.结论 低频电刺激诱发表面肌电信号更适于测量肌疲劳的动态变化.相对于传统功率谱,近似熵分析方法更适于处理电刺激诱发的表面肌电信号.     

基于OpenBCI与OpenViBE的脑机接口设计

以OpenBCI为脑电信号采集平台,OpenViBE为脑电信号分析平台,并以源自大脑感觉运动皮层的μ节律和β节律为基础,采用共空间模式算法作为特征提取方法,结合高斯核支持向量机,研制用于机械臂控制的运动想象脑机接口,并通过实验对信号特征提取方法以及分类算法的效果进行评估。初步实验结果表明,采用共空间模式算法处理后的分类准确率高于表面拉普拉斯空间滤波器,且支持向量机的分类性能优于线性判别分析。本系统的控制准确率达95%以上,可实现机械臂的有效控制。未来的研究将探索如何通过自定义插件来提高OpenViBE的硬件控制功能。 【关键词】脑机接口;脑电信号;OpenBCI;OpenViBE;运动想像     

A train of electrical pulses applied to the primary auditory cortex evokes a conditioned response in guinea pigs

As a step to develop auditory prosthesis by cortical stimulation, we tested whether a single train of pulses applied to the primary auditory cortex could elicit classically conditioned behavior in guinea pigs. Animals were trained using a tone as the conditioned stimulus and an electrical shock to the right eyelid as the unconditioned stimulus. After conditioning, a train of 11 pulses applied to the left AI induced the conditioned eye-blink response. Cortical stimulation induced no response after extinction. Our results support the feasibility of auditory prosthesis by electrical stimulation of the cortex.     

Aging of the trigeminal blink system

This study characterizes trigeminal blinks in normal human subjects between 20 and 80 years of age, 60-year-old Parkinson's disease patients, and young and old guinea pigs. In normal humans over 60 years of age, lid-closing duration, and the excitability and latency of the trigeminal reflex blink increase significantly relative to younger subjects. Aged guinea pigs appear to display similar increases in reflex blink duration and latency. Reflex blink amplitude, however, does not change consistently with age. For subjects less than 70 years of age, a unilateral trigeminal stimulus evokes a 37% larger blink in the eyelid ipsilateral to the stimulus than in the contralateral eyelid, but 70-year-olds exhibit blinks of equal amplitude. In all cases, blink duration is identical for the two eyelids. If normal, age-related loss of dopamine neurons explains these trigeminal blink modifications, then Parkinson's disease should exaggerate age-related changes in these blink parameters. Preliminary data show that Parkinson's disease increases blink duration and excitability relative to age-matched control subjects. Thus, it seems likely that normal, age-related loss of dopamine neurons accounts for increases in trigeminal blink excitability and duration. A previously uncharacterized type of trigeminally evoked blink appears after age 40 in humans and in aged guinea pigs. In subjects less than 40 years old, a single trigeminal stimulus elicits a single reflex blink. In subjects over age 40, however, a single stimulus frequently evokes a reflex blink and additional blinks that occur at a fixed interval relative to the preceding blink. These "blink oscillations" may arise from oscillatory processes within trigeminal reflex blink circuits. The presence of exaggerated blink oscillations in subjects with dry eye and benign essential blepharospasm suggests that an alteration of blink oscillation mechanisms plays a critical role in these disorders.     

Effect of isolation on classical conditioned histamine release in guinea pigs

To investigate the effect of abrupt or non-abrupt isolation stress on the classical conditioned histamine release, socially isolated or paired guinea pigs underwent conditioning procedures in which ovalbumin (OA) as an unconditioned stimulus (US) and dimethylsulfide (sulfur smelling) as a conditioned stimulus (CS) were simultaneously inhaled, and the plasma histamine levels after the exposure to the CS in a state of isolation or pairing were measured. The plasma histamine levels significantly increased from baseline in response to the CS (P < 0.05), except in the animals which were abruptly isolated during the exposure to the CS. The guinea pigs which were isolated during either the conditioning procedures or the exposure to the CS displayed significantly lower levels of plasma histamine than did the paired animals during both periods (P < 0.01, respectively). The plasma histamine levels in the guinea pigs which were isolated or paired during both periods were significantly higher than those of the control animals which had received the CS and the US separately (P < 0.05 and P < 0.01). A change of social relations, particularly isolation during the presentation of the CS, may have a suppressive effect on immediate asthmatic responses due to the conditioning mechanism.     

The role of the cerebellum in classical conditioning of discrete behavioral responses

The cerebellum and its associated circuitry constitutes the entire essential neuronal system for classical conditioning of eye-blink and other discrete responses (e.g. limb flexion) learned with an aversive unconditioned stimulus (US) using the standard delay paradigm where the conditioned stimulus (CS) and the US coterminate. Evidence reviewed here strongly supports the following conclusions. The CS pathway involves sensory relay nuclei projections to the pontine nuclei and its mossy fiber projections to the cerebellar cortex and nuclei. The US pathway involves activation of the inferior olive (dorsal accessory olive for eye blink) and its climbing fiber projections to the cerebellar cortex and nuclei. The conditioned response (CR) pathway involves the cerebellar interpositus nucleus, the superior cerebellar peduncle pathway to the magnocellular red nucleus and rubral projections to premotor and motor nuclei generating the behavioral response. Anatomical data, neuronal unit recordings, electrical stimulation, lesions and methods of reversible inactivation all strongly support the hypothesis that the essential memory trace for the learning of these discrete conditioned responses is formed and stored in the cerebellar interpositus nucleus. Neuronal/synaptic plasticity is also established in the cerebellar cortex in this form of learning but the role of the cortex is less clear. We argue that the cortex plays a key role in normal acquisition and adaptive timing of the conditioned response, under certain circumstances, but it remains unclear exactly what features of conditioning are being encoded in the cerebellar cortex in this basic form of associative learning and memory.     

Classical conditioning,sensitization and habituation in the spinal cat

Changes in the flexion reflex of the tibialis anterior muscle of acute spinal cats were examined during conditioning, sensitization and habituation paradigms. Experimental animals were classically conditioned by pairing electrical stimulation of the saphenous nerve (CS) with stimulation of the superficial peroneal nerve (US). Recordings from these nerves assured known and constant stimulus inputs. The response observed was an increase in the magnitude of the reflex response to the CS over training. Habituation (CS only) and sensitization (CS and US presentations, unpaired) control animals exhibited no such reflex facilitation. The results of post-tetanic potentiation studies indicated that the intertrial intervals used were not a factor in the differences observed between experimental and control groups. The results give positive support to the concept of spinal conditioning and emphasize the potential of this model system for the study of neural correlates of learning.     

Resting heart rate variability is associated with inhibition of conditioned fear

Startle blink as well as skin conductance responses (SCR) are widely used indices of learning processes associated with fear conditioning and extinction. During safety learning, the amygdala is under top‐down inhibitory control by the prefrontal cortex (PFC). The capacity of the PFC to exert inhibitory control over subcortical brain structures may be indexed by resting state vagally mediated heart rate variability (HRV). The present study investigated the association of resting HRV with startle blink and SCR during conditioned fear inhibition and extinction. Participants first learned to discriminate a threat cue (A) signaling an aversive unconditioned stimulus from a safety signal (B), which were each presented together with a third stimulus X (AX+/BX?). Then, both the threat and safety signal were presented together (AB) to test whether the presence of the learned safety signal inhibits the fear response to the danger signal. Finally, AX was presented without reinforcement (AX?) to investigate fear extinction. Higher HRV was associated with pronounced fear inhibition and fear extinction. Resting HRV levels were associated with fear extinction as indexed by startle blink potentiation but not SCR, which presumably reflect more cognitive aspects of learning. Resting HRV may reflect the capacity of the prefrontal cortex to inhibit subcortical fear responses in the presence of safety or when former threat cues are presented in the absence of threat.     

Orienting response and detection of thalamic stimulation: mechanism of perceptual learning in the cat

Naive cats cannot use thalamic stimulation as a signal to perform a behavioral response when stimulus intensities are too weak to evoke orienting behavior. Responses are quickly learned at higher intensities of stimulation, and with continued training, the cats become able to response to the weaker, previously ineffective stimulus. This increase in sensitivity is not due to changes in tonic arousal and appears to be relatively specific to the stimulated nucleus. The procedures may be useful in exploring the neural mechanisms of perceptual learning.     

A model of hippocampal learning during classical conditioning

During classical conditioning of the rabbit blink reflex, a large fraction of the hippocampal pyramidal neurons are recruited to respond to the conditioned stimulus. The summed response of these neurons comes to match the whole time-amplitude profile of nictitating membrane movement, whereas some individual neurons respond only to part of this profile. A model is described which accounts for these data. The model proposes a learning rule to explain neuron recruitment and uses a tapped delay line to account for the temporal learning properties of the system and the spectrum of individual unit responses.     

Cerebellum lesion impairs eyeblink-like classical conditioning in goldfish

The cerebellum of mammals is an essential component of the neural circuitry underlying classical conditioning of eyeblink and other discrete responses. Although the neuroanatomical organization of the cerebellum is notably well conserved in vertebrates, little is actually known about the cerebellar learning functions in nonmammal vertebrate groups. In this work we studied whether the cerebellum of teleost fish plays a critical role in the classical conditioning of a motor response. In Experiment 1, we classically conditioned goldfish in a procedure analogous to the eyeblink conditioning paradigm commonly used in mammals. Goldfish were able to learn to express an eyeblink-like conditioned response to a predictive light (conditioned stimulus) that was paired with a mild electric shock (unconditioned stimulus). The application of unpaired and extinction control procedures demonstrated that also in teleosts the learning of this motor response depends on associative rules. In Experiment 2 we studied whether classical conditioning of this response is critically dependent on the cerebellum and independent of telencephalic structures as occurs in mammals. Cerebellum lesion prevented the acquisition of the eyeblink-like conditioned response whereas telencephalon ablation did not impair the learning of this response. No deficit was observed following lesions in the performance of the unconditioned response or in the percentage of spontaneous responses. These results suggest that cerebellum ablation in goldfish affects a critical component of the circuitry necessary for the acquisition of the conditioned response but does not interfere with the ability of the animal to perform the response itself. The striking similarity in the role of cerebellum in classical conditioning of a motor response between teleost fish and mammals suggests that this learning function of the cerebellum could be a primitive feature of the vertebrate brain that has been conserved through evolution.     

Neutrophil response and function during acute cytomegalovirus infection in guinea pigs.

The mobilization and functional characteristics of polymorphonuclear leukocytes (PMNs) at the site of an inflammatory stimulus were studied during acute cytomegalovirus infection in guinea pigs. Weanling Hartley strain guinea pigs were inoculated subcutaneously with approximately 10(6) 50% tissue culture infective doses of virulent salivary gland-passaged guinea pig cytomegalovirus. The virus was uniformly present in bone marrow, buffy coat, and casein-elicited peritoneal exudate cells 5 to 7 days after the inoculation. The mean numbers of circulating PMNs in the animals were 2,862/microliters in uninfected controls and 880/microliters in infected animals. The total peritoneal PMNs recovered 14 h after casein injection were 491 X 10(6) and 237 X 10(6) in control and infected animals, respectively. The number of 50% tissue culture infective doses of guinea pig cytomegalovirus per 10(6) purified peritoneal PMNs was 10(2.17). Neutrophil O2 consumption was similar in infected and control animals in response to either stimulation by a neutrophil activator, phorbol myristate acetate, or phagocytosis of Staphylococcus aureus. However, the maximal rate of H2O2 release and the percent killing of S. aureus by peritoneal exudate cells from infected animals were significantly reduced compared with uninfected controls during acute infection. Granulocytopenia, a decreased mobilization of PMNs to the site of the inflammatory stimulus, a diminished cellular release of H2O2 in response to a bacterial stimulus, and a modest reduction in bacterial killing were demonstrated during experimental acute cytomegalovirus infection. Such reductions in granulocyte number and function at inflammatory sites during this type of infection could alter antimicrobial defenses.