DEVELOPMENT OF LOW FREQUENCY MEG HARDWARE AND SOFTWARE

拟议研究的总体目标是开发硬件， 软件和技术，以大幅扩展 脑磁图(MEG)作为一种临床诊断工具和AS 神经科学基础研究的一种模式。梅格已经被利用了 到目前为止，神经生成器的本地化在 病理情况(如局灶性癫痫)以及正常来源 (例如，听觉、视觉或体感诱发反应)。是这样的 本地化总是涉及重大的简化，例如 将源近似为单电流偶极子，将磁头近似为均匀 球体。这项提议的目的之一是开发新的数据分析 开发MEG提取独特能力的技术和软件 来自生理磁场的更有意义的信息种类 起源。其中将包括区分和定位弱信号的方法 几乎与更强的发电机同时点火的发电机，以及 监测脑磁图信号中细微光谱变化的方法 警觉性或觉醒的变化或自发性皮质的其他变化 活动。 脑磁图的第二个能力是完全非侵入性测量 非常慢的(DC)漂移，已知出现在各种 病理情况。这种转变不能轻易地用 体表脑电(EEG)由于阻抗的变化 不可避免地发生在电极-蒙皮界面。不幸的是，梅格 测量结果也受到环境磁噪声的污染(甚至 在精心屏蔽的房间中)和区域产生的磁场 病人身体不在研究范围内(“病人噪音”)。这样的噪音已经 在低频率的本地化研究中影响不大 噪声被过滤掉，其中实现了额外的降噪 通过对大量重复信号进行信号平均。这是 然而，对于自发低频率的观察，情况并非如此 活动。到目前为止，由 事实证明，神经磁力仪制造商不足以应对这样的情况 问题，在某些情况下，它们自己将构件引入数据。 我们实验室的初步测量表明， 这些噪音问题的各种解决方案。这样做的第二个目的是 提议是开发可靠的DC-MEG测量技术，以及 将脑磁图的能力扩展到测量绝对值 生物磁场。为了这两个目标，我们的技术将在 适当的幻影、动物模型和人类病人和对照。

The overall objective of the proposed research is to develop hardware, software, and techniques to substantially expand the utility of Magnetoencephalography (MEG), both as a clinical diagnostic tool and as a modality for basic studies in the neurosciences. MEG has been utilized extensively to date for the localization of neural generators in pathological conditions (e.g. focal epilepsy), as well as normal sources (e.g. auditory, visual, or somatosensory evoked responses). Such localizations always involve significant simplifications such as approximating sources as single current dipoles and heads as homogeneous spheres. One aim of this proposal is to develop new data analysis techniques and software to exploit the unique ability of MEG to extract more significant kinds of information from magnetic fields of physiologic origin. Among these will be methods to distinguish and localize weak generators which fire almost simultaneously with stronger ones, and methods to monitor subtle spectral changes in MEG signals accompanying changes in alertness or arousal or other changes in spontaneous cortical activity. A second capability of MEG is the completely non-invasive measurement of very slow (DC) shifts which are known to arise in a variety of pathological conditions. Such shifts cannot readily be studied using surface electroencephalography (EEG) because of impedance changes which inevitably occur at the electrode-skin interface. Unfortunately, MEG measurements are also contaminated by environmental magnetic noise (even in elaborately shielded rooms) and magnetic fields arising from regions of the patient's body not under study ("patient noise"). Such noise has been of little consequence in localization studies in which low frequency noise is filtered out and in which additional noise reduction is achieved by signal averaging over a large number of repetitive signals. This is not the case however, for the observation of spontaneous low frequency activity. To date, noise cancellation techniques provided by neuromagnetometer manufacturers have proven inadequate to deal with such problems, in some cases themselves introducing artifacts into the data. Preliminary measurements in our laboratory point the way towards a variety of solutions to these noise problems. The second aim of this proposal is to develop technology for reliable DC-MEG measurements, and to extend the capability of MEG to the measurement of absolute values of the biomagnetic field. For both aims, our techniques will be tested in phantoms, animal models and human patients and controls, as appropriate.