DEVELOPMENT OF LOW FREQUENCY MEG HARDWARE AND SOFTWARE

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The ongoing objective of our research has been to develop hardware, software, and techniques to expand the utility of Magnetoencephalography (MEG), both as a clinical diagnostic tool, and as a modality for basic studies in the neurosciences. With a large array, whole head neuromagnetometer now available in our lab, and such systems becoming more generally available, but at quite high prices, the demonstration of added utility for MEG becomes even more significant. Sophisticated mathematical analytical techniques develooped in this lab, finite difference field mapping (FDFM) and two dimensional inverse imaging (2DII), as well as several commercial software packages, will be applied to clinical data gathered from potential epilepsy surgery patients, for presurgical mapping and source localization. The results of these techniques will be systematically compared to the standard equivalent current dipole (ECD) analysis, carried out at a number of institutions. A second method of source location utilizing the pseudo-DC magnetic fields arising post- ictally in temporal lobe epilepsy patients will also be studied using epilepsy surgery candidates. DC MEG techniques will be utilized for a continuing study of migraine and stroke patients. During the next grant period the physiological differences and similarities between migraine with aura and migraine without aura (classic and common migraine) will be studied using MEG signals essentially identical to signals measured from spreading cortical depression in animal models. Methods for using MEG measurements for determining rehabilitation and recovery in stroke patients will be developed. In all of the foregoing studies, the nature of the MEG signals detected in humans will be validated using the MEG signals arising from well-established animal models of the same conditions. These studies will be conducted in three species with progressively more complex cortexes, rat, rabbit, and swine. The use of dynamic period analysis (DPA) to produce whole head mapping of the changes in cortical activity accompanying arousal changes and sleep will be studied. 2DII imaging will be used to define active discrete and extended source activity associated with sleep. The spatial and temporal resolution of MEG will be utilized to study dyslexic subjects, and to localize regions of abnormal activity. A series of visual/auditory stimuli involving word, picture, and shape recognition will be used. If successful with young adult dyslexics, the study will be extended the study to children and individuals with other learning disabilities.