基于脑电运动速度想象的单次识别研究

基于运动想象脑电节律活动的脑-机接口是脑-机接口系统研究中的重要范式之一。本研究给出一种基于运动速度想象的新的研究范式,探索在该研究范式下对运动速度想象具有反应性的脑电节律活动,并进行单次识别。采集了4个健康志愿者想象左手食指快速运动(4 Hz)和慢速运动(1 Hz)时的脑电信号,速度由节拍器定节奏和训练。通过能量谱分析,在C3、Cz和C4通道发现了对运动速度想象具有反应性的频带:9 Hz至13 Hz。提取通道C3、Cz和C4上9 Hz至13 Hz频带能量构建特征空间,分别利用Fisher判别分析和多层感知器神经网络进行运动速度想象的单次识别,对于左手食指快速运动和慢速运动想象,Fisher判别分析和多层感知器神经网络取得的平均误分类率分别是27.7±1.2%,28.4±4.6%,正确识别率均在70%以上。结果表明,尽管运动速度想象的单次识别是一个困难的挑战,但通过精心设计研究范式,适当训练被试,能够诱发出对速度起反应的特征频带,基于脑电单次识别运动速度想象是可行的,该研究可望能够为脑-机接口提供额外的新的速度控制参数。     

脑磁图在大脑感觉运动功能区占位性病变患者中的应用

目的：探讨脑磁图（MEG）在大脑皮层感觉、运动功能区占位性病变患者中的应用价值.方法：对81例大脑皮层感觉和（或）运动功能区及其附近占位性病变患者,应用151信道全头型MEG系统,通过电流刺激正中神经和胫神经确定上、下肢体感皮层的位置,运动皮层分别通过双手食指按压键盘引起的MEG反应来定位.术前将磁源性影像（MSI）通过神经影像导航进行三维重建,了解相应功能区与病变的解剖关系,设计手术入路.感觉功能区病变患者和运动功能区不能确定的患者术中通过电刺激正中神经（或胫神经内踝）使用皮层电极于拟定的中央沟前后的皮层记录体感诱发电位（CSEP）,依据中央沟前后皮层记录到的CSEP具有极性反转的特征来确定中央沟.其中8例患者通过对指运动行功能磁共振（fMRI）检查,在术中唤醒状态下通过电刺激大脑皮层确定运动功能区.结果：81例患者全部定位出感觉功能区,75例患者定位出运动功能区,6例患者因功能障碍或配合差运动功能区不能定位.术后1例患者病变对侧肢体运动障碍加重,其余80例患者无感觉、运动功能损害.结论：术前行MEG功能区定位有助于医生选择合适的手术入路和避免术中损伤脑功能区皮质,最大限度地保护神经功能,减少手术伤残率,提高手术疗效.     

电生理监测技术联合解剖定位在脑运动区手术中的应用

目的探讨电生理监测技术联合解剖定位在脑运动区手术中的应用。方法在Pubmed和中国知网数据库,以电生理监测技术、解剖定位和脑运动区手术为关键词,查阅1997年5月—2013年12月关于电生理监测技术与脑运动区解剖定位在脑运动区手术中应用的相关文献,进行分析总结。结果解剖定位包括功能MR和影像导航。电生理监测脑功能定位技术包括体感诱发电位位相倒置技术、经颅电刺激运动诱发电位、皮层电刺激运动区定位、皮层电刺激语言区定位、皮质下电刺激定位运动通路。解剖定位和电生理监测技术在脑运动区手术中各有利弊,目前趋势是联合应用。结论在脑运动区手术中,应用电生理监测联合解剖定位可提高脑运动区解剖定位的精确度,达到最大限度切除肿瘤、保留神经功能的作用。     

术中直接皮层电刺激判断大脑功能区在胶质瘤切除术中的应用

目的:试用术中直接电刺激判断大脑功能区的位置和范围的方法,以求术中最大程度切除肿瘤,减少神经系统损伤。方法:对唤醒麻醉下手术切除优势半球语言区胶质瘤患者26例以及邻近或累及脑运动功能区胶质瘤患者26例,在术中直接行皮层刺激,判断功能区的位置和肿瘤的关系。结果:患者在唤醒麻醉下,利用直接皮质电刺激可以准确定位初级运动皮质区和语言功能区,术后患者Karnofsky生活状态(KPS)评分结果较术前提高。结论:在唤醒麻醉下,可检测到患者的运动和语言的脑功能区,并可判断与肿瘤位置的关系。术中采用直接皮质电刺激可定位脑重要功能区,能最大限度地切除病变,最大限度地保护脑功能区。     

意识任务识别中事件相关脑电的时频域信息熵表达

事件相关脑电的量化表征对于研究意识任务识别和认识大脑思维机制具有重要意义.本研究对左右手想象意识任务的脑电信号进行小波包分析,提取出时频域信息熵用来表征事件相关脑电的变化;进而,分析了时频域信息熵特征的事件相关去同步/同步的变化时程,应用互信息评价时频域信息熵对事件相关脑电的表征能力,将相同步理论应用于导联间的脑电信号分析;设计时变线性分类器实现左右手想象运动意识任务识别,获得了满意的结果,最小分类错误率为9%.结果表明,时频域信息熵与频带能量具有一致的变化时程;时频域信息熵具有比频带能量更好的分离性,是事件相关去同步,同步的一个敏感的量化参数;时频域信息熵结合相同步相干性指数.能够提供更多反映大脑意识任务的状态信息.     

低频节律源传播方向对近真实头模型表面场电位动态参量的影响

θ振荡(4～8 Hz)是与学习、记忆等高级功能密切相关的低频脑节律,源于脑深处皮质区,头表面以额叶、颞叶最丰富。神经科学实验发现,该节律在脑内以一定方式传播,因成像技术局限和脑组织导电复杂性,其对头表面脑电节律的影响鲜有报告。依据等效偶极子电流源的脑电产生原理,以脑内低频单偶极子电流源(6 Hz正弦)偶极矩来仿真节律源驱动方向(以额叶为例定义指向),改变指向角度(以30°为移动单位),用有限元法计算电场,并对节律动态参量(大于平均值的显著能量、窄带相位)进行全局统计并对比。实验发现:脑内节律源在指向额叶表面传播时,几乎在所有指向角度下各向异性媒质会缩小显著能量空间;相反地,当源平行于额叶表面传播时,在所有指向角度下各向异性媒质会扩展显著能量空间,能量对源指向具有敏感性,而相位稳定性减小, 只与脑内节律源非线性相位时程有关,对该指向不敏感。结果表明,脑内低频节律源传播方向对头表面场电位动态参量作用不同。该研究为理解头表面低频节律动态参量提供电场计算依据,有助于理解脑内电活动、脑组织导电特性和头表面场电位动态参量之间的映射关系。     

运动意识脑电的动态独立分量分析

研究了用独立分量分析方法进行运动意识脑电信号特征分析的可行性。提出了用峭度极大动态独立分量分析方法进行μ节律提取的新思想。通过对批处理ICA算法和动态ICA算法在运动意识脑电特征分析的结果比较,得出了动态ICA算法更适合于运动意识脑电特征分析和提取。研究中发现,动态ICA混合矩阵系数的时间波形能准确即时地反映受试者进行左右手运动想象时运动神经皮层的μ节律变化,这一结果对脑认知和脑—机接口研究具有较大的实际意义,为独立分量分析方法在事件相关电位(ERP)特征提取中的应用提供了新的思路。     

生物反馈训练后癫痫患者脑电相关维数变化的分析

研究生物反馈训练对难治性癫痫患者脑电相关维数的影响。以21例难治性癫痫患者为研究对象,强化患者12~15 Hz的感觉运动节律波,抑制4~8 Hz的θ波。经过一定疗程的反馈治疗后,其中6例癫痫症状有明显改善且跟踪采集了脑电记录的病例,其16导联处的脑电相关维数均有不同程度的增加,尤其以训练点C4附近前脑区的脑电相关维数增加更加显著,表明脑电生物反馈治疗有助于皮层神经元群体电生理活动向更加混沌的状态转化,从而改善癫痫病态症状。相关维数可以通过表征大脑生理状态的改变,用于脑电生物反馈治疗效果的评价。     

基于小波包分解的不同状态下脑电信号分析

本文针对脑电信号的非平稳性,引入小波包分解理论处理临床脑电.根据脑电信号的不同节律特性,提出应用小波包分解构造不同频率特性的时变滤波器,提取脑电信号不同节律的动态特性,并由此构造各种节律的动态脑电地形图.为了研究不同脑功能状态下脑电信号各种节律的动态特性,文中对两组不同的临床脑电数据进行分析,比较两种状态下各种节律的动态特性.实验结果表明,利用小波包分解对脑电信号进行滤波,能够有效提取临床脑电不同节律的动态特性,为分析脑电信号提供一条新的途径.     

运动相关皮层电位研究的知识图谱分析

运动相关皮层电位是一种事件相关电位,可以反映运动前的策划、准备和早期的运动执行过程,近年来多受关注。以Web of Science^TM核心合集收录2000年至今“运动相关皮层电位”为研究主题的498篇文献为数据来源,利用Cite SpaceⅤ可视化技术绘制图谱分析相关问题。分析表明,研究热点主要集中于运动关联电位、运动皮层、脑电图、运动等方向。运动相关皮层电位的研究发展按照时间可以分为3个阶段：第一阶段主要以大脑额叶、诱发电位、吞咽诱发运动相关皮层电位的研究为主;第二阶段以脑机接口、运动想象、运动检测电位与帕金森综合征为主;第三阶段研究趋势逐渐向着康复性研究方向发展,主要以脑电图学、注意力、以及抓握分析为主。通过对运动相关皮层电位的研究热点以及发展历程进行分析,有助于对体育训练和运动康复等领域提供理论和应用研究方面的参考。     

Steady-State Movement-Related Potentials Evoked by Fast Repetitive Movements

We investigated steady-state movement-related cortical potentials elicited by fast repetitive movements (1/sec@rpar; with 50-channel EEG. The experimental design comprised a comparison @lpar;a@rpar; between unilateral movements of the digits and the toes and (b) between metronome-paced and self-paced initiation of the movements. A distinct biphasic pattern of electrical activity following movement onset was observed, namely a frontal negative peak at a latency of 90 ms (post-MP₁₀₀) and a frontal positive peak at a latency of 310 ms )post-MP₃₀₀(. Pacing exerted its effects mainly on the amplitude and on the latency of the post-MP₃₀₀. Source analysis revealed that both peaks could be modelled by a single source. The source locations were highly reproducible across the metronome-paced and self-paced conditions, and, they followed the expected somatotopic organisation.     

Temporal dynamics of primary motor cortex γ oscillation amplitude and piper corticomuscular coherence changes during motor control

In recent years, the use of non-invasive techniques (EEG/MEG) to measure the ~80 Hz (“gamma”) oscillations generated by the primary motor cortex during motor control has been well validated. However, primary motor cortex gamma oscillations have yet to be systematically compared with lower frequency (30–50 Hz, ‘piper’) corticomuscular coherence in the same tasks. In this paper, primary cortex gamma oscillations and piper corticomuscular coherence are compared for three types of movements: simple abductions of the index finger, repetitive abductions of the index finger of different extents and frequencies and static abduction of the index finger at two different force levels. For simple movements, piper coherence and gamma amplitude followed very similar time courses with coherence appearing at approximately half the frequency of cortical gamma oscillations. No evidence of 2:1 phase–phase coupling was observed. A similar pattern of results was observed for repetitive movements varying in size and frequency; however, during the production of static force, the time courses became dissociated. During these movements, EMG piper amplitude was sustained for the entire contraction; gamma power showed a burst at onset but no piper corticomuscular coherence was observed. For these data, this dissociation suggests that while primary motor cortex gamma oscillations and piper corticomuscular coherence may often co-occur during the production of dynamic movements, they probably reflect different functional processes in motor control.     

Behaviorally contingent property of movement-related activity of the primate putamen

1. In this study, the movement-related activity of putamen neurons was investigated in behaving monkeys. The objective of the study was to examine whether the activity occurring in phase with body movements is directly related to the movement per se by encoding movement parameters or whether it is dependent on the circumstances in which the movement is performed. 2. Sensorially triggered arm movements were used as a behavioral task. A sequence of three visually triggered repetitive flexion-extensions of the elbow joint across the target were followed by the delivery of a juice reward. 3. There are two classes of putamen cells: type I, with tonic spontaneous discharges (2-7 Hz) and broad extracellularly recorded action potentials, and type II, with very low spontaneous discharge rate (less than 1 Hz). The movement-related phasic discharges occur exclusively in type II cells. 4. The movement-related activity of type II cells is classified into two contrasting types of cells: type IIa that exhibit burst discharges preceding the first movement of a sequence of repetitive arm or orofacial movements but that are almost inactive during succeeding movements, and type IIb that show movement-locked burst discharges with one-to-one correspondence. The somatotopic location of the cells was identified by microstimulation and/or sensory responses to passive somatosensory manipulation of the periphery. 5. The activities of type IIa cells occur with a short and fairly constant latency after the visual trigger stimulus and cease as soon as the sequence of the learned movements is initiated. In the condition in which the monkey attended to the visual trigger stimulus without initiating learned movements and waited for the delivery of juice reward at a fixed time after the stimulus, type IIa cells exhibited slight but consistent phasic discharges after the visual stimulus with short latency. This indicates that the type IIa cells have a visuomovement property. The type IIb cells, on the other hand, have a longer latency of activity after the visual trigger than type IIa cells and do not have the visuomovement property. 6. The type IIa cells change their activity pattern depending on whether the direction of initial movement is predictable before the trigger stimulus or not. 7. The activities of type IIa cells in the arm area of the putamen precede the electromyogram (EMG) of prime mover muscles by greater than 100 ms on average, whereas most type IIb cells are activated after the EMG during a learned arm-movement task.(ABSTRACT TRUNCATED AT 400 WORDS)     

Low Frequency Cortico-Muscular Coherence During Voluntary Rapid Movements of the Wrist Joint

Rapid voluntary point-to-point wrist tracking movements are generated by the co-operative action of a large number of wrist muscles activated in a stereotypic pattern. This pattern is composed of a two burst sequence occurring in synergist and antagonist muscles. The time course and duration of these bursts are relatively fixed but the burst magnitude in any one muscle varies in relation to the direction of movement and the preferred directional tuning characteristic of the muscle. This creates a highly adaptive method for generating fast movements to different positions in space. In this study we have examined the extent to which this adaptive burst behaviour can be associated with activity changes occurring in the contralateral motor cortex. Time dependent coherence estimates were obtained from simultaneous recordings of the electroencephalogram (EEG) made from the contralateral sensorimotor cortex and the electromyogram (EMG) from various wrist flexor and extensor muscles during fast point-to-point wrist tracking movements. Using the onset of movement as a trigger, event related coherence estimates reveal the presence of short lasting periods of low frequency (<12 Hz) coherence during the execution of fast wrist movements. The onset and duration of the periods of low frequency coherence vary with direction of movement and the temporal burst profile of a particular muscle's EMG activity. It is therefore likely that a significant low frequency activation of the motor cortex plays a part in the generation of the EMG burst patterns that underpin rapid point-to-point movements of the human wrist.     

Temporal evolution of oscillatory activity predicts performance in a choice-reaction time reaching task

In this study, we characterized the patterns and timing of cortical activation of visually guided movements in a task with critical temporal demands. In particular, we investigated the neural correlates of motor planning and on-line adjustments of reaching movements in a choice-reaction time task. High-density electroencephalography (EEG, 256 electrodes) was recorded in 13 subjects performing reaching movements. The topography of the movement-related spectral perturbation was established across five 250-ms temporal windows (from prestimulus to postmovement) and five frequency bands (from theta to beta). Nine regions of interest were then identified on the scalp, and their activity was correlated with specific behavioral outcomes reflecting motor planning and on-line adjustments. Phase coherence analysis was performed between selected sites. We found that motor planning and on-line adjustments share similar topography in a fronto-parietal network, involving mostly low frequency bands. In addition, activities in the high and low frequency ranges have differential function in the modulation of attention with the former reflecting the prestimulus, top-down processes needed to promote timely responses, and the latter the planning and control of sensory-motor processes.     

Role of primate basal ganglia and frontal cortex in the internal generation of movements

In order to more comprehensively assess the role of the basal ganglia in the internal generation of movements, we studied the activity of neurons in the head of the caudate and in the rostral putamen in relation to the execution of movements. Monkeys performed self-initiated and stimulus-triggered arm reaching movements in separate blocks of trials. With stimulus-triggered movements, 217 striatal neurons increased their activity after the trigger stimulus (127 in caudate, 90 in putamen). Of these, 68 neurons showed time-locked responses to the trigger stimulus, with a median latency of 60 ms, that were independent of visual or auditory stimulus modalities. Three quarters of responses were conditional on a movement being performed. These responses may participate in neuronal processes through which the reception of a stimulus is translated into the execution of a behavioral reaction. Further, 44 neurons increased their activity before the earliest muscle activity without being clearly time-locked to the stimulus (148-324 ms before movement onset), 55 neurons were activated later before the movement, and 50 neurons were activated after movement onset. With self-initiated movements, 106 striatal neurons showed movement-related activity beginning up to 460 ms before movement onset (52 in caudate, 54 in putamen). Comparisons between the two types of movement were made on 53 neurons with premovement activity beginning more than 500 ms before self-initiated movements. Only one fifth of them also showed movement-related activity with stimulus-triggered movements, including trigger responses. Comparisons among 39 neurons with movement-related activity during self-initiated arm movements showed that about half of them also showed movement-related activity with stimulus-triggered movements. These data demonstrate a considerably segregated population of striatal neurons engaged in the internal generation of movements, whereas processes underlying the execution of movements appear to involve overlapping neuronal populations.     

The activation pattern in normal humans during suppression,imagination and performance of saccadic eye movements

The distribution of activated cerebral regions was examined in nine normal subjects during four different eye movement-related conditions: (1) fixation – fixation on a central light emitting diode; (2) saccadic suppression – fixation on a diode in the presence of flashing lateral targets; (3) reflexive/volitional saccades – performance of overt eye movements to two laterally lit targets and back to the centre; and (4) imagined saccades – imagining, but not performing, the same eye movements. The regional neural activity was measured indirectly using repetitive bolus injections of oxygen-15-labelled water and positron emission tomography (PET) to yield time-integrated images of the normalized count distribution. These were aligned and anatomically normalized to a standard stereotactic space and the averages of each condition were analysed categorically using statistical parametric mapping. Compared to central fixation, reflexive/volitional saccades significantly activated regions in the classically known cortical oculomotor regions. The most notable activation during the saccade suppression task, compared to central fixation alone, was a bilateral activation of the parietal cortex with a right-sided preponderance, activation of the supplementary eye field/caudal cingulate regions, and activation of frontal regions close to the frontal eye fields. Imagined performance of eye movements without overt eye movements activated the supplementary eye field and frontal eye fields identically to regions involved in overt eye movements, thus demonstrating that overt eye movements are not a prerequisite of the activation of these regions in normal humans.     

Movement-related potentials with reference to isometric force output in discrete and repetitive tasks

This study investigates whether different speed and accuracy constraints in discrete and repetitive index finger isometric force-production tasks influence the characteristics of the movement-related potentials (MRP) preceding and accompanying these tasks. Three components of MRP (Bereitschaftspotential, BP, motor potential, MP, and movement-monitoring potential, MMP) associated with isometric force output were identified and examined. Our principal finding for the MRP amplitude showed that only MMP, not BP and MP, was enhanced at higher rates of force development for both speed and accuracy tasks. That is to say, there was a high correlation between MMP peak amplitude and the rate of force development for both repetitive and discrete force-production tasks. Additionally, the amplitude of MMP was consistently higher for fast, rather than accurate, force outputs. Moreover, the results from analysis of MRP onset times suggest that, in general, the MRP begin earlier for the fast force output than for the accurate force output. Received: 9 October 1997 / Accepted: 21 May 1998     

EEG activity during the verbal-cognitive stage of motor skill acquisition

This study examined changes in EEG activity associated with motor performance during the verbal-cognitive stage of skill learning. Participants (n = 14) were required to practice a sequential finger tapping task. EEG activity was recorded both before and after short-term practice, during finger tapping and during two control conditions. EEG power (Fz, Cz, Pz, T3, T4) and coherence (T3-Fz, T4-Fz, Fz-Cz, Fz-Pz) were computed for the theta (4-8 Hz), slow alpha (8-10 Hz), fast alpha (10-12 Hz), slow beta (12-20 Hz), and fast beta (20-28 Hz) bandwidths. Changes in motor performance were rapid during the very early stages of practice and then slowed in accord with the law of practice. These changes were accompanied by increases of theta power at Fz and beta coherence at T4-Fz, suggesting that progression through the verbal-cognitive stage of a sequential finger tapping task is accompanied by more narrowed attention and improved mapping between the stimuli and the finger movements.     

Fast ballistic arm movements triggered by visual, auditory, and somesthetic stimuli in the monkey. I. Activity of precentral cortical neurons

Single-unit recordings from motor cortex (area 4) were obtained in two monkeys trained to perform simple flexion and extension movements of the arm in response to somesthetic, visual, and auditory signals. All neurons tested showed movement-related responses that were identical for equivalent movements irrespective of the modality of the triggering stimulus. Progressively longer reaction times were always associated with progressively longer latencies of unit responses. When visual and auditory stimuli were presented simultaneously, the intensity and the duration of both motor and unitary responses remained unchanged as if only one stimulus (auditory) had been given. When the auditory stimulus was appropriately delayed with respect to the visual one, shortening of motor reaction time was observed with a corresponding shortening of the latency of unit responses. In addition to movement-related responses, some neurons showed sensory-related responses mainly to the somesthetic stimulus (37%) and more rarely to the auditory (11%) and visual stimuli (3%). These "sensory" responses preceded and were independent of the movement-related responses; they showed no obvious correlation with the reaction time. Whenever tested, the somatosensory responses persisted after extinction of the motor responses. These findings suggest that, in our experimental conditions, area 4 neurons of the monkey are not involved in the early processing of sensory information required for the initiation of simple, triggered movements. Rather, they appear to generate signals that are mainly related to the characteristics of the motor responses.