大脑皮质运动区功能定位：皮质脑电证据

背景：神经皮质（运动区）功能定位可以帮助医生最大限度地切除病灶并避免神经功能损害,关系到病人术后的生存质量。目前的神经皮质（运动区）功能定位方法在速度、准确和安全性方面需要进一步提高。 目的：探讨皮质脑电用于术中神经皮层（运动区）功能定位的可行性和意义。 设计、时间及地点：自身对照实验。本研究采用国际BCI第IV届竞赛数据,由海港医院（华盛顿 西雅图）在2008年6月11日采集,处理由华南理工大学生物科学与工程学院（广东省广州市）在2009年9月完成。 对象：华盛顿西雅图海港医院的3位癫痫病人运动区皮质脑电信号（以下简称ECoG）数据。 方法：采集位于大脑神经皮质（运动）功能区的手指皮质区域的皮质脑电信号数据,同时采集相应手指弯曲运动数据,作自身对照;利用离散db3小波对ECoG数据进行7层小波分解并重构各单子频带信号,提取各单子频带重构信号在运动事件发生前后的能量比（ERD指标）为特征量,比较其大小确定特征频带;构造多个阈值进行特征量分类,结果与相应手指弯曲运动数据比较,比较检出正确率确定特征阈值。将20次试验采集数据分成训练和测试组,分别用于特征提取方法和分类器的设计和性能检测,进行检出正确率分析。 主要观察指标：用于特征提取和分类的特征频带、ERD指标特征量和特征阈值。 结果：以 D6（7.812-15.625 Hz）特征频带重构信号的ERD指标为特征量,以40.5%为特征阈值进行分类,ERD特征明显,识别度高。其分类定位检出正确率达到90%。 结论：自发皮质脑电信号分析可以作为神经皮质运动区功能定位的可靠方法。     

皮质脑电图小波分析定位运动区的探索性研究

目的研究术中皮质脑电图(ECoG)小波分析对运动区皮质定位的可行性。方法利用小波变换,对ECoG信号进行多层分解和重构,提取4个主要频带(δ、θ、μ和β)重构信号的运动前后能量比(ERD)为特征量,并构造特定阈值进行分类,然后与相应手指弯曲运动数据进行对照比较,分析检测的正确率。结果d6子频带(μ频带)的运动前后ERD变化最明显;以40%为阈值进行分类,其定位运动区的正确率达到93%。结论通过小波分析对ECoG的特征进行提取和分类,可有效定位运动区皮质。     

基于Mu/Beta节律的想象运动脑电信号特征提取

背景：不同的运动会产生不同的脑电信号,脑机接口技术就是利用脑电信号的特异性,通过现代信号处理技术和外部的连接实现人脑与外部设备的通信。以实现脑机接口在线研究的目标,首先要解决的是脑电信号处理的速度问题。 目的：研究快速、准确地提取脑电信号特征及分类的方法。 方法：充分利用想象运动过程中,脑电信号中Mu/Beta节律的事件相关同步化和去同步化特性,以2003年BCI竞赛数据为处理对象,采用带通滤波和小波包分析的方法提取Mu、Beta节律,提取C3、C4两通道上的能量平均值形成二维特征向量,利用matlab自带的classify函数进行分类。 结果与结论：通过对训练数据进行测试得到较为合适的参数,利用该参数对同等条件下的训练数据和测试数据分别进行判别,分类正确率分别达到87.857%和88.571%。 关键词：特征提取与分类;脑电信号;事件相关同步化/去同步化;想象运动;小波包分析     

皮质脑电图μ节律术中定位运动区皮质的研究

目的探索皮质脑电图(ECoG)μ节律分析定位运动区皮质的应用价值。方法回顾性分析8例大脑功能区病变病例资料,均在全麻术中唤醒状态下手术,术中皮质直接电刺激(DES)定位运动区皮质。采集静息、手运动任务下ECoG信号,提取ECoG 4个主要节律:δ、θ、μ、β,分析每个节律的事件相关去同步化现象(ERD),评价ECoG定位运动区皮质的灵敏性与特异性。结果术中DES均成功定位病人运动区皮质。在运动状态下,ECoG信号μ节律ERD变化最明显,其是运动区皮质的特征节律。以40%阈值为特征值,μ节律定位有较高灵敏性(81.0%)和特异性(91.7%)。结论 ECoGμ节律分析可用于术中定位运动区皮质,有望成为术中定位运动区的一种新方法。     

基于功率谱峰值及时变线性分类算法的运动意识分类

背景：脑电信号的特征提取是脑机接口系统中一个重要的环节,如何快速有效地提取反映大脑意识任务状态的脑电特征是进行分类、正确解读意识任务的关键。目前,提取脑电信号特征通常采用功率谱密度估计、自回归模型和小波变换等方法,这些特征都是以脑电信号的线性化为前提,上述方法不能很好地反映出大脑的非线性动力学性质。 目的：分析脑电信号功率谱峰值在识别左右手想象运动中的作用。 方法：采用脑机接口2003竞赛中Graz科技大学提供的脑电数据,用小波包分解获取8~24 Hz脑电信号,计算C3,C4电极脑电信号的功率谱峰值作为脑电特征向量,运用时变线性分类算法对运动意识任务运行分类。 结果与结论：对140次实验的测试样本进行数据分析,最大分类正确率可达89.29%,最大互信息和信噪比分别为0.626 9 bit和1.384 8。C3,C4电极8~24 Hz脑电信号功率谱峰值能很好地反映左右手运动想象脑电特征的变化,与事件相关去同步/事件相关同步现象变化一致,可在线识别左右手想象运动。     

术中皮质体感诱发电位与电刺激术定位脑功能区

目的探讨脑功能区手术中利用脑皮质体感诱发电位(SEP)及直接皮质电刺激定位脑功能区的方法及意义。方法对10例脑功能区病变病人在唤醒麻醉下进行手术，利用皮质SEP及皮质直接电刺激定位感觉区、运动区及语占区，住保护脑功能区的前提下，手术切除病变。结果7例病人利用SEP及皮质电刺激确定出运动感觉区，其中4例利用SEP位相倒置确定出中央沟，3例病变位于左侧额颞叶的病人通过皮质直接电刺激确定出语言区?术后功能均较术前明显好转。结论术中SEP及直接皮质电刺激可准确、实时确定脑功能区，最大程度地保护功能，切除病变。     

脑皮质电刺激对癫痫大鼠脑皮质兴奋性的影响

目的 观察重复脑皮质电刺激对氯化铁诱发慢性癫痫大鼠模型脑皮质兴奋性的影响.方法 通过在运动感觉区脑皮质注射氯化铁建立慢性癫痫大鼠模型,给予脑皮质低频(1 Hz)低强度(0.1 mA)和低频(1 Hz)高强度(1.0 mA)、高频(100 Hz)低强度(0.1 mA)和高频(100 Hz)高强度(1.0 mA)不同的重复电刺激,检测电刺激前后脑皮质后放电阈值、后放电时程和行为学评分.假刺激慢性癫痫大鼠作为对照组.结果 后放电阈值低频低强度组(2.10±0.38)mA与对照组(1.50±0.33)mA相比差异有统计学意义(P＜0.05).行为学评分和后放电时程各组与对照组相比差异无统计学意义.行为学评分与后放电阈值的比值低频低强度组(1.88±0.60)和低频高强度组(2.18±0.38)与对照组(3.22±0.67)相比差异有统计学意义(P＜0.01和P＜0.05).结论 重复低频低强度脑皮质电刺激可以升高氯化铁诱发慢性癫痫大鼠模型的脑皮质后放电阈值,降低脑皮质兴奋性,提示合适参数的脑皮质电刺激对氯化铁诱发大鼠癜痫具有抑制作用.     

应用皮质电刺激定位技术切除大脑功能区病变

目的总结皮质电刺激定位结合术中唤醒技术在脑功能区手术中的应用经验。方法回顾性分析26例脑功能区病变病人的临床资料,其中位于中央沟区14例,位于外侧裂周围12例。应用皮质电刺激结合术中唤醒麻醉技术行显微手术切除,术中实时行皮质功能定位。结果经神经导航验证肿瘤全切除19例(73.1%),部分切除7例(26.9%)。术后出现病变对侧肢体轻偏瘫2例,出现短暂性言语功能障碍2例;术后情况与术前比较无明显变化19例,肢体活动情况较术前好转3例。结论术中皮质电刺激结合术中唤醒技术是一种准确、可靠、安全的技术,可明确脑功能区,并进行术中实时监测,这可获得病变的最大程度切除,同时将术后发生永久性功能障碍的风险降到最低。     

基于LabVIEW运动想象的脑机接口系统***◆

背景：基于事件相关电位的脑-机接口,可广泛应用于残障患者的康复,显示出其重要性和未来实现的可行性。 目的：提出基于LabVIEW环境下的运动想象脑-机接口系统的实现方案。 方法：研究的关键部分是视觉刺激器的设计和脑电特征信号的特征提取两部分。测试者通过观察视觉刺激器上的左右手连续播放图像刺激产生脑电信号,采用带通滤波提高信噪比,用滑动窗截取脑电数据并且对截取的数据从能量的角度分析得到运动想象特征,同时可以在线提取特征,为实现实时系统打下了基础。 结果与结论：该方案能有效地提取出运动想象特征,并且通过离线模式识别进行了有效的分类,分类效果达到了82%。     

脑血管畸形患者运动皮质可塑性的功能MRI研究

目的 :探讨应用功能MRI(fMRI)研究位于或邻近初级运动中枢脑血管畸形患者运动皮质功能的可塑性。方法 :8例患者采集双手对掌运动激发后功能图像 ,观察功能区的分布特征 :计算活动指数 (AI)值 ;测量不同活动区信号强度 (SI)上升百分率。结果 :8例患者运动激发后在手运动区 (HRA)、辅助运动区 (SMA)、中央后回、额前区、顶叶等区域见活动。 5例有功能区移位的患者正常侧HRA活动区扩大 ,AI值为 0 3 9± 0 0 7,3例功能区无移位患者的AI值为 0 87± 0 12 (P <0 0 5 )。正常侧不同部位SI上升百分率均较病灶侧相应部位高 (P >0 0 5 )。结论 :脑血管畸形患者运动皮质可塑性改变表现为正常侧初级运动中枢的功能加强以及非特定手运动皮质的激活     

Combined MEG and EEG methodology for non-invasive recording of infraslow activity in the human cortex

OBJECTIVE: Periinfarct depolarisation and spreading depression represent key mechanisms of neuronal injury after stroke. Changes in cortical electrical potentials and magnetic fields in the very low frequency range are relevant parameters to characterize these events, which up to now have only been recorded invasively. In this study, we proved whether a non-invasive combined MEG/EEG recording technique is able to quantitatively monitor cortical infraslow activity in humans. METHODS: We used repetitive very slow and slow right finger movements as a physiological motor activation paradigm to induce cortical infraslow activity. Infraslow fields were recorded over the left hemisphere using a modulation-based MEG technique. EEG was performed using 16 standard Ag-Cl electrodes that covered the left motor cortex. RESULTS: We recorded stable focal motor-related infraslow magnetic field changes in seven out of seven subjects. We also found correlating infraslow electrical potential changes in three out of seven subjects. Slow finger movements generated significantly stronger field and potential changes than very slow movements. CONCLUSIONS: This study demonstrates the technical feasibility of combined non-invasive electrical potential and magnetic field measurements to localize and quantitatively monitor physiological, low amplitude, infraslow cortical activity in humans. This specific combination of simultaneous recording techniques allows to benefit from the specific physical advantages of each method. SIGNIFICANCE: This combined non-invasive MEG-EEG methodology is able to provide important information on infraslow neuronal activity originating from tangentially and radially oriented sources. Moreover, this dual approach has the potential to separate neuronal from non-neuronal DC-sources, e.g., radially to the head orientated DC-currents across the skin/scalp/skull/dura occurring during cerebral hypercapnia or hypoxia.     

Oscillatory cortical activity and movement-related potentials in proximal and distal movements.

OBJECTIVES: Event-related desynchronization (ERD) of alpha- and beta-rhythms, the post-movement beta-synchronization and the cortical movement-related potentials were analyzed in distal (finger) and proximal (shoulder) movements.METHODS: EEG was recorded in 7 healthy right-handed men using a 59-channel whole-head EEG system while subjects performed self-paced movements.RESULTS: The amplitude of the Bereitschaftspotential (BP) was greater over the central midline area and smaller over the contralateral sensorimotor hand area in shoulder than in finger movements. The maximal alpha- and beta-ERD was localized at parietal electrodes in shoulder movements and over the left and right sensorimotor hand area in finger movements. The post-movement beta-ERS was greater in shoulder than in finger movements, especially at the electrode located 3.5 cm left of the central midline electrode. A significant correlation between the slope of the terminal portion of the BP (negative slope) and amplitude of the post-movement beta-synchronization was observed in shoulder but not in finger movements.CONCLUSIONS: Enhancement of BP over the central midline electrode suggests increased activation of the supplementary motor area in proximal movements. The spatial distribution of the alpha- and beta-ERD and of the post-movement beta-ERS shows topographic differences which may refer to the somatotopic organization of the primary sensorimotor cortex with shoulder representation medial to hand and fingers. The correlation between the negative slope and the post-movement beta-ERS in proximal movements supports the view that the brief post-movement inhibition over the motor cortical area is related to the pre-movement activation of that area.     

High-resolution EEG in poststroke hemiparesis can identify ipsilateral generators during motor tasks

BACKGROUND AND PURPOSE: Multimodal neuroimaging with positron emission tomography (PET) scanning or functional MRI can detect and display functional reorganization of the brain's motor control in poststroke hemiplegia. We undertook a study to determine whether the new modality of 128-electrode high-resolution EEG, coregistered with MRI, could detect changes in cortical motor control in patients after hemiplegic stroke. METHODS: We recorded movement-related cortical potentials with left and right finger movements in 10 patients with varying degrees of recovery after hemiplegic stroke. All patients were male, and time since stroke varied from 6 to 144 months. All patients were right-handed. There was also a comparison group of 20 normal control subjects. RESULTS: Five of 8 patients with left hemiparesis had evidence of ipsilateral motor control of finger movements. There were only 2 cases of right hemiparesis; in addition, 1 patient had a posteriorly displaced motor potential originating behind a large left frontal infarct (rim). CONCLUSIONS: Reorganization of motor control takes place after stroke and may involve the ipsilateral or contralateral cortex, depending on the site and size of the brain lesion and theoretically, the somatotopic organization of the residual pyramidal tracts. Our results are in good agreement with PET and functional MRI studies in the current literature. High-resolution EEG coregistered with MRI is a noninvasive imaging technique capable of displaying cortical motor reorganization.     

Cortical activation during fast repetitive finger movements in humans: steady-state movement-related magnetic fields and their cortical generators

Objective: To study the cortical physiology of fast repetitive finger movements.Methods: We recorded steady-state movement-related magnetic fields (ssMRMFs) associated with self-paced, repetitive, 2-Hz finger movements in a 122-channel whole-head magnetometer. The ssMRMF generators were determined by equivalent current dipole (ECD) modeling and co-registered with anatomical magnetic resonance images (MRIs).Results: Two major ssMRMF components occurred in proximity to EMG onset: a motor field (MF) peaking at 37±11 ms after EMG onset, and a postmovement field (post-MF), with inverse polarity, peaking at 102±13 ms after EMG onset. The ECD for the MF was located in the primary motor cortex (M1), and the ECD for the post-MF in the primary somatosensory cortex (S1). The MF was probably closely related to the generation of corticospinal volleys, whereas the post-MF most likely represented reafferent feedback processing.Conclusions: The present data offer further evidence that the main phasic changes of cortical activity occur in direct proximity to repetitive EMG bursts in the contralateral M1 and S1. They complement previous electroencephalography (EEG) findings on steady-state movement-related cortical potentials (ssMRCPs) by providing more precise anatomical information, and thereby enhance the potential value of ssMRCPs and ssMRMFs for studying human sensorimotor cortex activation non-invasively and with high temporal resolution.     

Impaired movement-related potentials in acute frontal traumatic brain injury.

OBJECTIVE: Focal brain lesions due to traumatic brain injury (TBI) do not only lead to functional deficits in the lesion area, but also disturb the structurally intact neuronal network connected to the lesion site. Therefore we hypothesized dysfunctions of the cortical motor network after frontal TBI. The movement related potential (MRP) is an EEG component related to voluntary movement consisting of the Bereitschaftspotential (BP), the negative slope (NS), and the motor potential (MP). The aim of our study was to demonstrate alterations in the movement related cortical network in the acute stage after TBI by comparing our patients' MRPs to those of a healthy control group. METHODS: EEGs of 22 patients with magnetic resonance imaging defined contusions of the prefrontal cortex were recorded within 8 weeks after TBI. We further recruited a healthy control group. The paradigm consisted of self-paced abductions of the right index finger. RESULTS: Compared to healthy controls, the BP in the patient group was significantly reduced and its onset delayed. Moreover, an enhanced contribution of the postrolandic hemisphere ipsilateral to the movement and a reduced contribution of the left frontal cortex, ipsilateral to the lesion in the majority of the patients, were observed during motor execution (MP). CONCLUSIONS: Anatomical connections between the prefrontal cortex and the supplementary motor area (SMA) are known to exist. We suggest that prefrontal lesions lead to reduced neuronal input into the SMA. This deficit in the preparatory motor network may cause the reduced BPs in our patients. Moreover, an increased need for attentional resources might explain the enhanced motor potentials during movement execution. In conclusion, we demonstrated altered MRPs in the acute stage after frontal TBI, which are a consequence of disturbed neuronal networks involved in the preparation and execution of voluntary movements.     

Cortical potentials preceding voluntary movement: evidence for three periods of preparation in man

We have recorded movement-related cortical potentials (MRCPs) to voluntary middle finger extension from 10 young and 10 old subjects free of neurological disease using the method of detecting EMG onset associated with each movement described by Barrett et al. (1985). The slow potential shifts preceding movement were measured by fitting a linear regression line to the wave forms to obtain a measure of their slope. Three separate potential shifts were identified. The first had a scalp distribution and onset latency similar to the Bereitschaftspotential (BP) first reported by Kornhuber and Deecke (1964, 1965). The potential shift immediately preceding movement corresponded with the NS' of Shibasaki et al. (1980). We identified, for the first time, a third shift intervening between BP and NS' and named it the intermediate shift (IS). The onset of BP occurred about 1.6 sec before EMG onset and was followed by IS which began about 875 msec before movement. The onset of NS' occurred 300 msec before EMG onset and terminated about 90 msec before this event. The slope of BP preceding right finger movement was steeper than that preceding left hand movement in all our right-handed subjects. The distribution of BP was symmetric about the midline. The IS potential shift had a slope which was steeper on the average preceding left finger movement than right. The distribution of IS was symmetric about the midline preceding left finger movement but had a contralateral tendency preceding right hand movement. NS' had a maximum slope at contralateral electrodes over the hand motor area and parietal areas. It was suggested that the BP potential shift originates in the supplementary motor area on the medial surface of the cerebral cortex. The differing distribution of the IS shift for the two hands suggests that this potential may be generated bilaterally preceding left finger movement but from the contralateral hemisphere only preceding movement of the right finger. The most likely origin of this potential was thought to be superior premotor cortex. NS' was considered to originate in primary motor cortex with possible contributions from other cortical areas associated with movement.     

Activation-induced changes in evoked and slow brain potentials: effect of cocaine in rabbits previously subchronically treated by cocaine

To study the type of adaptive modification (tolerance vs. sensitization) in different organism's indices following intermittent cocaine (COC) administrations, acute COC (2 mg/kg, SC)-induced changes in heart and breathing rate, response to increasing noxious stimulation, spontaneous EEG and event-related evoked and slow brain potentials (ERP) registered from the occipital cortex and hippocampal CA1 region were investigated in naive rabbits and one subchronically treated with COC (6 injections at a same dose). Tolerance developed for bradycardia, depression of noxious responsiveness, cortical desynchronization and increase of main components of cortical ERP, typical to acute COC, while the changes in breathing and hippocampal ERP were stable. These changes as well as a significant increase due to COC administrations of the basal values of an animal's noxious responsiveness and increase in relative changes in main component of cortical ERP (N205) are considered as a consequence of adaptive changes in neurophysiological/neurochemical substrate accepting COC action and mediating phenomena tolerance-sensitization and dependence typical to the drug.     

Event-related desynchronization and excitability of the ipsilateral motor cortex during simple self-paced finger movements.

OBJECTIVE: To study the time course of oscillatory EEG activity and corticospinal excitability of the ipsilateral primary motor cortex (iM1) during self-paced phasic extension movements of fingers II-V. METHODS: We designed an experiment in which cortical activation, measured by spectral-power analysis of 28-channel EEG, and cortical excitability, measured by transcranial magnetic stimulation (TMS), were assessed during phasic self-paced extensions of the right fingers II-V in 28 right-handed subjects. TMS was delivered to iM1 0-1500 ms after movement onset. RESULTS: Ipsilateral event-related desynchronization (ERD) during finger movement was paralleled by increased cortical excitability of iM1 from 0-200 ms after movement onset and by increased intracortical facilitation (ICF) without changes in intracortical inhibition (ICI) or peripheral measures (F waves). TMS during periods of post-movement event-related synchronization (ERS) revealed no significant changes in cortical excitability in iM1. CONCLUSIONS: Our findings indicate that motor cortical ERD ipsilateral to the movement is associated with increased corticospinal excitability, while ERS is coupled with its removal. These data are compatible with the concept that iM1 contributes actively to motor control. No evidence for inhibitory modulation of iM1 was detected in association with self-paced phasic finger movements. SIGNIFICANCE: Understanding the physiological role of iM1 in motor control.     

Event-related cerebral potentials. Classification and clinical use]

Event-related potentials (ERP) constitute an heterogeneous group of brain electrical signals time-locked to sensory stimulation, motor responses, and associative processes, recorded using computer averaging. Several kinds of brain electric activity are encompassed by the generic term "event related potentials": sensory evoked potentials, time-coherent cerebral events related to motor acta, long-latency potentials associated with psychological variables, slow potential shifts linked to psychological constructs, and "emitted" cerebral events of endogenous origin. Shortcomings of this classification are pointed out and a simpler one is proposed, distinguishing between sensory, motor, and associative time-locked potentials. Their clinical use is illustrated under six major headings: testing of sensory function, localization of lesions, maturation of the central nervous system, genetic markers, evaluation of pharmacologic agents, and indicators of cognitive processes. Some methodological issues relevant to the clinical use of ERP are discussed.