24例脑肿瘤病人三维脑电地形图与CT、MRI的对照研究

目的：对比研究脑肿瘤患者三维脑电地形图（３Ｄ）和二维脑电地形图（２Ｄ）的变化及临床应用价值。方法：以ＣＴ、ＭＲＩ结果对照，对２４例脑肿瘤患者进行３Ｄ、２Ｄ和常规ＥＥＧ对比分析。结果：与影像学检查一致、基本一致和不一致者：３Ｄ分别为１４、５和５例，２Ｄ为５、１３和６例，ＥＥＧ为９、９和６例。结论：３Ｄ和ＥＥＧ检查结果与影像学一致率高于２Ｄ。２Ｄ的根本缺陷是采用平面圆代表立体的大脑，不能准确显示病变与范围     

Quantitative EEG with brain mapping in strokes: Is it useful for prognosis?

Summary Thirty-two patients suffering from a stroke due to a hemispheric infarct and treated in a rehabilitation department were studied for a period of three months. They were regularly assessed by quantified EEG and mapping (three measurements) and by quantitative measurements of their performances in motor ability, activities of daily living and speech (four measurements). No correlation was found between their clinical improvement and the modifications of their EEG. Similarly no correlation was found between the initial EEG data and the clinical outcome.     

EEG assessment of brain activity: Spatial aspects,segmentation and imaging

High temporal resolution and sensitivity to index different functional brain states makes the EEG a powerful tool in psychophysiology. Its full potential can now be utilized since recording technology and computational power for the large data masses has become affordable. However, basic traditional strategies in EEG need reviewing.Conventional, spontaneous or evoked EEG traces which are used for various complex analyses give ambiguous information on EEG power (amplitude) and phase for a given point on the scalp. Principally, analysis should first be done over space, then over time, to avoid ambiguities or pre-selections. First or second spatial derivative computations can provide “reference-free” data for analyses over time. We propose to use direct, spatial approaches for the analysis of the scalp EEG field distributions when simultaneous recording in several EEG channels can be examined.The ambiguity of the conventional EEG waveshapes results in different, equally “correct” scalp maps of EEG power of the same multichannel data for different reference electrodes. An exeption are scalp maps of EEG power computed against the common, average reference, as they are related to the reference-free spatial distribution (maps) of the maximal and minimal (extreme) field values over time, and thus are directly interpretable in terms of net orientation of the generator process.A proposed, reference-free EEG segmentation into epochs of periodically stationary spatial distributions of the mapped scalp EEG fields uses the locations of maximal and minimal (extreme) field values at each moment in time as classifiers, and thus avoids the priviledging of two arbitrarily chosen recording points in the field.     

Topographic mapping of EEG during sleep

Summary Topographic aspects of all night sleep EEG were investigated in 10 healthy volunteers (age 20–35 years). EEG brain maps showed an increase of delta power from stage 1 to 4, a decrease of alpha power most pronounced parieto-occipitally and a slowing of the dominant alpha frequency. Differences of EEG power in different sleep stages (as compared to wakefulness) are displayed topographically. Analysis of the course of stage 2 showed an increase of delta power and a decrease of theta power in the first sections of the night, and an increase of beta power later in the night.     

EEG mapping in middle aged normal volunteers: The impact of cerebrovascular risk factors

Summary The impact of major risk factors for stroke on EEG mapping and routine EEG findings was evaluated in volunteers with no clinical signs of cerebrovascular or other neuropsychiatric disease. Focal changes were seen in 22 subjects (30%) by means of EEG mapping, but in only 12 cases (16%) when routine-EEG was used (p<.05). 4/35 (11%) volunteers without RF had focal changes while this was seen in 18/39 (46%) subjects in whom risk factors (RF) were found (p<.01). An association was seen between the presence of EEG foci and number of RF. 59% of subjects with 2 or 3 RF had focal abnormalities as opposed to 36% of those with 1 RF and 11% of RF free individuals (p<.05). The findings could be confirmed by averaging the EEG data according to the different number of RF revealing statistically significant differences between each of the 3 groups. Using routine EEG alone no significant correlation to the presence or number of RF was found. Our data demonstrate EEG abnormalities in a considerable portion of normal middle aged individuals which in part may be attributed to the presence of RF.This study was supported by the Steiermärkischen Krankenanstal tengesellschaft m.b.H. and by the Jubilaeumsfond of the Austrian National Bank-Project # 3905.     

EEG power mapping,dipole source and coherence analysis in chernobyl patients

Summary EEG power mapping, coherence analysis, source localization of epileptiform activity and psychoneurological investigations were performed in 100 patients (males, 25–45 years old, right-handed), who took part in the cleaning of the Chernobyl disaster in 1986–1987, and compared with a control group (healthy persons of the same age). Neuropsychological studies showed autonomie, endocrine, emotional and other disorders in all patients. About 70% of all patients had paroxysmal EEG activity and intermittent seizures sometimes associated with loss of consciousness. EEG power mapping showed higher than normal levels of alpha- and theta-bands power, mainly in the frontal and central areas in the one group of patients. In others, power was lower especially in alpha-band. Paroxysmal waves of alpha- and theta-bands had localization of dipole sources at deeper near midline levels, and as a rule with a shift to the right hemisphere. Paroxysmal beta-waves demonstrated sources of a diffuse character at a more basal level with a shift to the left hemisphere. Interhemispheric coherences had lower values in the frontal and higher in the central leads than in healthy persons. Intrahemispheric coherences were decreased in the left hemisphere and increased in the right, opposite to that in controls.     

Alzheimer型痴呆和多发梗塞痴呆的定量脑电地形图研究

对１２例Ａｌｚｈｅｉｍｅｒ型痴呆（ＤＡＴ）、１５例多发梗塞性痴呆（ＭＩＤ）、１５例健康对照组的脑电地形图的定量研究显示：痴呆病人慢波功率的增多不同于正常老化，θ功率是最早增高的指标；ＭＩＤ较ＤＡＴ有更多的不对称性改变；脑电功率不仅与痴呆程度有量化联系，而且和特定认知功能也有量化联系；首次发现ＤＡＴ和ＭＩＤ各有不同的脑电功率和认知功能的量化联系方式。结果表明定量脑电地形图在痴呆研究中有一定应用前景。     

A spreadsheet application for processing long-term EEG recordings

This study develops a Windows application for processing huge tabular text files. The tool has been especially designed for handling EEG files. As a consequence, tables with more than 65,536 rows and 256 columns, which is a limitation found in Microsoft's Excel, can be loaded, visualized and processed with no more restrictions than the ones imposed by the memory of the operating system.Beyond tabular visualization, additional tools are available for chart customization and spreadsheet like cell processing commands. Additionally, commands are included for signal processing, cluster analysis and computationally taxing matrix algebra operations.     

A hybrid algorithm for solving the EEG inverse problem from spatio-temporal EEG data

Epilepsy is a neurological disorder caused by intense electrical activity in the brain. The electrical activity, which can be modelled through the superposition of several electrical dipoles, can be determined in a non-invasive way by analysing the electro-encephalogram. This source localization requires the solution of an inverse problem. Locally convergent optimization algorithms may be trapped in local solutions and when using global optimization techniques, the computational effort can become expensive. Fast recovery of the electrical sources becomes difficult that way. Therefore, there is a need to solve the inverse problem in an accurate and fast way. This paper performs the localization of multiple dipoles using a global-local hybrid algorithm. Global convergence is guaranteed by using space mapping techniques and independent component analysis in a computationally efficient way. The accuracy is locally obtained by using the Recursively Applied and Projected-MUltiple Signal Classification (RAP-MUSIC) algorithm. When using this hybrid algorithm, a four times faster solution is obtained.     

EEG mapping for surgery of epilepsy

Summary This report describes the objectives, problems, and current techniques associated with using EEG maps in the management of surgery of epilepsy. The purpose of EEG mapping in epilepsy is to precisely identify and characterize epileptogenic zones of the brain. Such zones may be single or multiple, pointlike or diffuse, and may be near or distant from the recording electrodes. The resulting measured electric fields are used to obtain information which, when analyzed in light of all the complementary clinical information, can frequently help to localize and describe the epileptic foci with more precision.     

The EEG mapping in the evaluation of patients with late onset epilepsy

In 62 patients with late onset epilepsy the findings of EEG mapping routine EEG and CT were compared. Forty four patients had generalized, 18 partial seizures. In 39 patients (63%) EEG mapping revealed focal changes but only in 24 patients (39%) using routine EEG alone. Thus the EEG mapping showed focal abnormalities significantly more often and this could be demonstrated in the separated groups of patients with generalized or partial seizures as well. Lesions in CT occurred in 39 patients (63%). The focal abnormalities in EEG mapping were significantly related to the lesions in CT. Moreover focal changes corresponding to CT lesions were obtained by means of EEG mapping in 32 patients (82%) but only in 20 patients (51%) using routine EEG and in that way the EEG mapping could indicate focal lesions in CT significantly more often than routine EEG. Regarding etiology this was especially seen in the group with vascular origin of epilepsy.     

等效源法脑电三维成像技术研究

为了进一步完善近年出现的大脑皮层成像技术，本文基于等效源思想，对ＣＩＴ作了若干数值仿真研究。仿真结果表明，ＣＩＴ方法中测试球面上的分面目源既可为现行的径向极源，也可为点电源源；被成像的实际脑电源可以是偶极源，也可以是点电流源或四极源。     

Word onset phonetic properties and motor artifacts in speech production EEG recordings

Electrophysiological research using verbal response paradigms faces the problem of muscle artifacts that occur during speech production or in the period preceding articulation. In this context, this paper has two related aims. The first is to show how the nature of the first phoneme influences the alignment of the ERPs. The second is to further characterize the EEG signal around the onset of articulation, both in temporal and frequency domains. Participants were asked to name aloud pictures of common objects. We applied microstate analyses and time‐frequency transformations of ERPs locked to vocal onset to compare the EEG signal between voiced and unvoiced labial plosive word onset consonants. We found a delay of about 40 ms in the set of stable topographic patterns for /b/ relative to /p/ onset words. A similar shift was observed in the power increase of gamma oscillations (30–50 Hz), which had an earlier onset for /p/ trials (～150 ms before vocal onset). This 40‐ms shift is consistent with the length of the voiced proportion of the acoustic signal prior to the release of the closure in the vocal responses. These results demonstrate that phonetic features are an important parameter affecting response‐locked ERPs, and hence that the onset of the acoustic energy may not be an optimal trigger for synchronizing the EEG activity to the response in vocal paradigms. The indexes explored in this study provide a step forward in the characterization of muscle‐related artifacts in electrophysiological studies of speech and language production.     

基于fMRI加权约束的FOCUSS迭代脑电源定位方法及其初步应用

脑电(Electroencephalography, EEG)和功能磁共振(Functional magnetic resonance imaging, fMRI)技术的结合,可以实现两者优势的互补,获得更加合理的源定位结果.本文报道的是一种将fMRI先验信息结合到脑电源定位中的新方法.在该方法中,先利用SPM方法计算获得fMRI的统计映射参数,然后将基于计算获得的统计参数构造的权矩阵结合到FOCUSS的迭代过程中,对脑电的反演提供具有fMRI先验空间位置信息的约束,提高脑电的源空间定位精度,从而获得更加合理的定位结果.通过对一形状知觉实验fMRI和脑电数据的结合定位分析,结果初步证实了改进方法能获得和生理更加一致的结果.     

High resolution EEG

My research is supported by competitive grants from The National Institute of Mental Health, The National Institute of Neurological Diseases and Strokes, The Air Force Office of Scientific Research, The Office of Naval Research, The National Science Foundation and The National Institute of Alcoholism and Alcohol Abuse of the United States Federal government. I thank all my colleagues at EEG Systems Laboratory and SAM Technology for their essential contributions to our research, including especially, Jim Alexander, Jeffrey Bennett, Brian Cutillo, John Desmond, Don DuRousseau, Paul Hubenig, Judy McLaughlin, Jim Johnston, Jian Le, Harrison Leong, Nancy Martin, Vinod Menon, Bill O'Connor, Maggie Paula, Paulo Raffaelli, Bryan Reutter, Lita Sam Vargas, Michael Smith, Mike Ward, Jenny Zhang, and Jane Zhu. Thanks also to KDS.     

Mapping EEG-potentials on the surface of the brain: A strategy for uncovering cortical sources

Summary This paper describes a uniform method for calculating the interpolation of scalp EEG potential distribution, the current source density (CSD), the cortical potential distribution (cortical mapping) and the CSD of the cortical potential distribution. It will be shown that interpolation and deblurring methods such as CSD or cortical mapping are not independent of the inverse problem in potential theory. Not only the resolution but also the accuracy of these techniques, especially those of deblurring, depend greatly on the spatial sampling rate (i.e., the number of electrodes). Using examples from simulated and real (64 channels) data it can be shown that the application of more than 100 EEG channels is not only favourable but necessary to guarantee a reasonable accuracy in the calculations of CSD or cortical mapping. Likewise, it can be shown that using more than 250 electrodes does not improve the resolution.This study was supported by grants from the Deutsche Forschungsgemeinschaft to Thomas Elbert and Brigitte Rockstroh. The authors would like to thank Dr. Dorothy Charbonnier.     

Correlation of EEG activities between slow-wave sleep and wakefulness in patients with supra-tentorial stroke

Summary Using topographic EEG mapping, we studied the relationships between delta activity during slow-wave sleep (SWS) and the background EEG activity during wakefulness, in 11 normal subjects and 35 stroke patients with unilateral supra-tentorial lesions. Delta-1 power during SWS showed a significant positive correlation with alpha-1 power during wakefulness, in both hemispheres. Delta-1 and delta-2 power during SWS correlated positively not only with alpha-2 power, but also with delta-1 and delta-2 power during wakefulness in the affected hemisphere. These figures indicate that the amount of delta activity during SWS can be associated with that of alpha activity during wakefulness. A close negative correlation was observed between delta power during SWS and the age of the subjects in the patient group. The Barthel index showed no significant correlation with delta-1 or delta-2 power in either hemisphere in patient group. Our results suggest that delta activity during SWS may be associated with dysfunction of the cerebral cortex in stroke patients as well as in normal aged subjects.     

Multivariate statistical brain electromagnetic mapping

Summary Brain Electromagnetic Topography (BET) has attained widespread use. The representation of EEG or MEG parameters as scalp maps (BETm) aids its clinical interpretation. However, some critical issues limit the usefulness of BETm. In particular, the conventional statistical assessment of BETm with respect to normative data is based upon marginal significance probability scales which involve multiple univariate comparisons (one at each recording site). As a consequence, the probability of false positive findings (type I error) is increased above its nominal level. The use of conservative levels avoids this phenomenon but results in a considerable increase of the probability of not detecting real abnormality (type II error). Furthermore, BETm are constructed without taking into consideration the patterns of correlations characteristic of electromagnetic data under normal states of brain functioning. This limits the capability of BETm of representing multivariate aspects of abnormality. This paper introduces some techniques to approach these difficulties. Multivariate Brain Electromagnetic Topographic maps (MBETm) are defined, which retain the attractive features of mapping but also take advantage of multivariate characteristics (in the spatial and frequency domains) to highlight aspects of neuropathology. Moreover, simultaneous significance probability (SSP) scales, valid for both BETm and MBETm, are introduced for the global control of the probability of a type I error. The use of these techniques is illustrated with data from patients with cortical tumours and with epilepsy. ROC analysis shows that in some cases there is a significant improvement in both detection and localization accuracy.