磁源性影像对母语为汉语者语言皮质定位的研究

目的 确定磁源性影像(MSI)对汉字处理脑皮质的定位价值。方法 对8例右利手及1例左利手母语为汉语的健康受试者给予双耳纯音及词义相关和不相关的成对汉字刺激。由脑磁图(MEG)设备记录刺激后产生的听觉诱发磁场。对采集的数据分别按照纯音、词义相关成对汉字及词义不相关成对汉字产生的反应进行叠加。将MEG资料叠加到MRI上获得MSI。结果 所有受试者左、右半球均诱导出2个明显高的磁反应波M50、M100。M50及M100均定位于双侧颞横回。同一受试者同侧半球对词义相关的成对汉字及不相关成对汉字的反应波近似。1例左利手受试者右侧半球在300～600ms有明显高的波峰，而左侧半球无此波峰。其MSI显示语言区位于Wernicke区。2例右利手受试者双侧半球均出现明显的300—600ms磁反应波。提示这2例受试者语言区位于双侧半球。其MSI显示语言区位于Wernicke区。6例右利手受试者双侧半球均诱导出潜伏期300～600ms的反应波，但左侧半球波幅明显高于右侧半球。这6例受试者MSI显示，语言区均定位于颞上回后部及颞中回后部，即Wernicke区。结论 比较左、右两侧半球磁反应晚成分(潜伏期300～600ms的反应波)，优势半球波幅明显高于非优势半球。对词义相关及不相关的成对汉字进行判断均能够确定大脑优势半球语言皮质的位置。     

Ictal and Interictal Activity in Partial Epilepsy Recorded with Multichannel Magnetoelectroencephalography: Correlation of Electroencephalography/Electrocorticography, Magnetic Resonance Imaging, Single Photon Emission Computed Tomography, and Positron Emission Tomography Findings

Ictal and interictal epileptic activity was recorded for the first time by multichannel magnetoencephalography (MEG) in three patients with partial epilepsy. Pre- and intra-operative localization of the epileptogenic region was compared. The interictal epileptic activity was localized at the same region of the temporal or frontal lobe as the ictal activity. Main zones of ictal activity were shown to evolve from the tissue at the centers of interictal activity. Pre- and intra-operative electrocorticography (ECoG) as well as postoperative outcome confirmed localization in the temporal and frontal lobe. Results also correlated with findings from scalp EEG, interictal and ictal single photon emission computed tomography (SPECT), positron emission tomography (PET), and magnetic resonance imaging (MRI). Combined multichannel MEG/EEG recording permitted dipole localization of interictal and ictal activity.     

脑磁图在运动区脑膜瘤手术中的应用研究

目的 探讨脑磁图（MEG）在手术治疗皮质运动区脑膜瘤中的应用价值。方法 选择21例脑皮质运动区或其附近脑膜瘤患者，常规行影像学和MEG检查，配合神经导航系统行肿瘤显微手术切除。结果 肿瘤切除按Simpson分级，Ⅰ级10例，Ⅱ9例，Ⅳ级2例。术后神经功能障碍完全恢复正常17例，明显好转3例，加重1例。结论 MEG是无创性功能区定位、确定病变与皮质运动区位置关系的重要方法，对皮质功能区病变的手术方案制定和功能区脑组织的保护具有重要的指导价值。     

Delayed auditory processing underlying stimulus detection in Down syndrome

Down syndrome (DS) is characterized by intellectual disability and development of dementia that are attributed to similar neuropathological features as observed in Alzheimer's disease (AD). The aim of this study was to investigate whether DS patients have similar impairment of preattentive auditory processing as observed in AD. Sinusoidal tones were presented to DS patients and healthy controls, and evoked auditory evoked fields (AEF) were measured with a whole-head magnetoencephalography (MEG) system. Patients with DS had significantly delayed and attenuated N100m, and delayed but not attenuated P50m responses over both hemispheres. Present results indicate that preattentive auditory processing underlying stimulus detection is impaired in DS. Given that anticholinergic drugs modulate AEFs, degeneration of cholinergic system in DS could contribute to the damaged auditory processing.     

空间频率对视觉诱发磁场影响的脑磁图研究

目的 用脑磁图来研究人脑视皮质对不同空间频率黑白棋盘格翻转刺激所产生视觉诱发磁场成分之一的M100的影响，包括峰值潜伏期、振幅和源位置三方面。方法 测定9例健康志愿者对视角分别为25’、40’、50’、60’、80’、120’和240'的半视野棋盘格刺激的磁场反应。结果 格大小对M100峰值潜伏期和振幅的影响有显著统计学意义(P＜0．05)。随着格变小，M100峰值潜伏期延长、振幅减小。偶极源位于刺激野对侧的枕叶距状裂附近。结论 不同空间频率的棋盘格刺激对M100峰值潜伏期、振幅的影响均有显著意义，但对源位置无显著影响。     

抑郁症患者识别喜悦表情前额叶-杏仁核最优效能连接模式探究

目的探究抑郁症患者在识别喜悦表情时前额叶．杏仁核最优效能连接模式,并以此探讨抑郁症前额叶-杏仁核情绪加工可能的异常机制。方法利用脑磁图检测20例抑郁症患者及20例相匹配的健康对照者在识别动态面部表情时的脑部反应。通过动态因果模型方法选出最优模型,并比较抑郁症组及对照组的效能连接变化。结果贝叶斯模型选择结果显示,总体最优模型的特征是背外侧前额叶、前扣带回、杏仁核两两存在自上而下的调节连接,模型超越概率为0．41。最优模型中固有连接水平出现组间差异,在固有连接水平上,抑郁症组右侧杏仁核-前扣带回的前向连接显著减弱（t=-2．50,P=0．016）,前扣带回-背外侧前额叶的前向连接显著增强（t=2．37,P=0．022）,杏仁核-背外侧前额前向连接显著增强（t=2．10,P=0．04）。结论抑郁症患者右侧半球自下而上的固有连接异常,可能与抑郁症患者负性偏向有关;而抑郁症患者处理喜悦面孔时前额叶-杏仁核调制连接并未出现明显异常。     

Magnetic auditory M100 source location in normal females

We recorded magnetoencephalographic auditory evoked fields from the left and right hemispheres of six normal adult female subjects, in response to unattended tone pips. Magnetic field data was used to estimate location, orientation, depth, and strength of the 100-ms latency evoked field component (M100). M100 source locations did not significantly differ in left and right hemispheres. Previous studies in six normal males demonstrated M100 sources to be significantly further anterior in the right hemisphere. Compared to the previously reported male subjects, M100 sources in the right hemisphere of these females were significantly further posteriorly, by a mean value of 2.1 cm. These findings, while preliminary, support sex-related functional and/or structural differences in the superior temporal lobe, and would be compatible with the female right temporal planum extending further posteriorly. They suggest MEG recordings may be a useful addition to studies of sex-related difference in brain function and/or structure.     

Detection of fetal auditory evoked responses by means of magnetoencephalography

MagnetoEncephaloGraphy (MEG) is proposed as a non-invasive technique to detect the physiological activity of fetal brain, due to its ability to record brain activity without direct contact with the head and the transparency of magnetic signals in passing through extracerebral fetal layers and the mother's abdomen. Healthy women with uncomplicated pregnancies and fetuses in breech presentation were examined; gestational ages at time of study ranged between 36 and 40 weeks. In order to evaluate fetal well-being, ultrasound and cardiotocographic data were assessed a few days before and after MEG recording sessions. The participating women were placed in a semi-reclining position in a magnetically shielded room; here the presentation of the fetus and precise region of the mother's abdomen corresponding to the fetal head were determined by ultrasound investigation in order to place the MEG detecting system as near as possible to the fetal brain. MEG recordings were performed by means of a 28-channel neuromagnetic system. Every MEG recording session was performed during the acoustic stimulation of fetuses, in order to detect the cerebral events evoked by peripheral stimuli. The auditory stimuli were delivered from a plastic tube placed on mother's abdomen, near the fetal head, and consisted of a 300 ms 103 dB pure tone at 500 and 1000 Hz, presented at a 0.4 c/s repetition rate. In six cases following accurate digital subtraction of maternal and fetal electrocardiographic (EKG) signals we remained with a stimulus-related response peaking at about 250 ms; this was considered to originate from the fetal brain. In favour of this in three cases a clear dipolar distribution was evident at the peak of brain response centered on the fetal head and consistent with a brain generator. Despite several technical problems requiring solution before a possible routine clinical application, MEG has been found to be suitable for the non-invasive exploration of the fetal brain.     

Magnetoencephalography/Magnetic Source Imaging in the Assessment of Patients with Epilepsy

Summary: Magnetoencephalographic (MEG) dipole source localization is a particularly promising new tool for noninvasive presurgical evaluation of epileptogenic foci. It is potentially more accurate than EEG localization techniques because magnetic fields are not attenuated or distorted by the skull and scalp, which allows cerebral sources to be modeled more simply. MEG spike and seizure sources are routinely co-registered with the patient's brain MRI for clinical interpretation. This has been called magnetic source imaging. Numerous studies have shown that MEG localization of foci agreed with lesion position, depth electrode and ECoG data, PET and MRI findings, and surgical success. The recent development of whole head sensor arrays has greatly enhanced the ease with which epileptiform magnetic fields can be recorded and analyzed.     

Multiple Bilaterally Asymmetric Cortical Sources Account for the Auditory N1m Component

The hypothesis that the N1, the major negative component of the cortical evoked response to auditory stimuli, originates from the primary auditory cortex has been supported by several studies. In a previous study we showed that, when monaural stimulation with pure tones is used, the distribution of the N1 peak over the scalp could be accounted for by successive activation of adjacent sources on the floor of the Sylvian fissure. In an attempt to establish the generality of the phenomenon, in this study we investigated further the generation of the N1 component using a variety of auditory stimuli, including pure tones, complex sounds (musical notes), and words, as well as binaural stimulus presentation. Additionally, we used a new recording system which allows recording of the distribution of the magnetic flux over the entire head simultaneously, thus eliminating the need for multiple recording sessions and the related problems of habituation and of changes in attention level. We found that a series of single dipolar sources could account for the entire duration of the N1m component. The location of the sources fell within the primary auditory cortex and, during the evolution of the component, they followed a posterior-anterior, medial-lateral, superior-inferior trajectory, bilaterally, along the superior surface of the temporal lobes. Additionally, the distribution of N1 sources on the two hemispheres showed a marked asymmetry, with the right hemisphere sources covering a larger area. The established consistency of successive source excitation across subjects, studies, types of stimuli, and recording systems, as well as the newly demonstrated hemispheric asymmetry of source extent, suggest the presence of a reliable phenomenon indicative of the functional organization of the auditory cortex.