Magnetic Source Imaging of Visually Evoked and Oscillatory Electrical Activity ofthe Human Brain

摘要

The aim of this thesis work was to develop biomagnetic recording and analysistechniques and to apply them to studies of visually-evoked and spontaneous electrical activity in the human brain. The magnetoencephalographic method was applied to studies of the human visual cortex and oscillatory brain activity. Cerebral source currents evoked by simple, passively viewed checkerboard stimuli were found to be distributed over large regions of the cortex, showing complex variations as a function of time. The usefulness of minimum-norm estimates was evident in cases in which a multitude of sources overlap, both when giving a 2D estimate of the primary current distribution and when providing a standard representation of the measured magnetic field. With retinotopically organized stimuli, some of the difficulties inherent in the biomagnetic inverse problem could be overcome. Similar differentiation of the underlying source patterns should be possible in future studies by varying other stimulus properties as well.