Non invasive 3-demensional measurement of brain function with developed synthetic aperture magnetometry

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The equivalent current dipole (ECD) method conventionally used for analysis for magnetoencephalography represent the activated brain area as one or small number of dipoles. It is not enough for comprehensive understanding of the brain activity, since the functional process of the brain is derived from the activation of neurons in a certain volume of cortex and ECD only displays the center of gravity of activated brain as a representative single point. We applied recently developed synthetic aperture magnetometry (SAM) with a spatially-selective beamformer, which filters out the background brain noise from other regions to obtain the meaningful signals from the arbitrary target regions. The neuromagnetic signals are transformed into units of dipole moment on a per voxel basis ; this enables one to measure the current density of the small portion of the brain with an enhanced sensitivity (SAM virtual sensor method). With further application of statistical imaging technique, statistical d … More ifference in the power of selected frequency band can be evaluated between the active and control states. Those areas with statistical difference can be displayed on the individual MRI in a tomographic manner (SAM statistical method). In this study, following neuro-functional processes were analyzed. Owing to the superior spatial resolution of the MEG and to the novel filtering technique of SAM, the tomography of neuromagnetic event related synchronization (ERS) or desynchronization (ERD) evoked by neurological task was demonstrated for the whole brain.1. Motor-related brain activityThe influence of the hemispheric dominance as well as hand dominance wasdisclosed.2. Sensory-related brain activitySimultaneous and multifocal brain activations with very high frequency oscillation were disclosed.3. Language-related brain activityBoth sensory and motor language area were demonstrated with reading without phonation task.4. EpilepsyThe SAM virtual sensor method demonstrated the origin and the propagation process of epileptic discharges as if the intracranial electrodes were implanted. The elimination of invasive monitoring was implied. Less