Visualization of magnetoencephalographic data using minimum current estimates

The locations of active brain areas can be estimated from the magnetic field the neural current sources produce. In this work, we study a visualization method of magnetoencephalographic data that is based on minimum l(1)-norm estimates. The method can represent several local or distributed sources and does not need explicit a priori information. We evaluated the performance of the method using simulation studies. In a situation resembling typical magnetoencephalographic measurement, the mean estimated source strength exceeded baseline level up to 2 cm from the simulated point-like source. The method can also visualize several sources, activated simultaneously or in a sequence, which we demonstrated by analyzing magnetic responses associated with sensory stimulation and a picture naming task. (C) 1999 Academic Press.