MAGNETIC-FIELD TOMOGRAPHY OF CORTICAL AND DEEP PROCESSES - EXAMPLES OF REAL-TIME MAPPING OF AVERAGED AND SINGLE TRIAL MEG SIGNALS

Magnetic field tomography (MFT) provides 3-dimensional estimates of br ain activity, from non-contact, non-invasive measurements of the magne tic field generated by coherent electrical activity in the brain. MFT analysis of averaged auditory ''odd-ball'' data show cortical and deep activation, presumably from the amygdala and hippocampus. These resul ts are compared with MFT estimates obtained from a patient who had und ergone lobectomy which removed these structures. The variability from subject to subject is confounded by variability between trials for the same subject; the relationship between the averaged and single trials is probed by bi-hemispheric simultaneous measurements performed under the same odd-ball paradigm and by MFT analysis of auditory evoked dat a and interictal epileptic activity.