Visualization of magnetoencephalographic data using minimum current estimates

The locations of active brain areas can be estimated from the magnetic fiel d the neural current sources produce. In this work, we study a visualizatio n method of magnetoencephalographic data that is based on minimum l(1)-norm estimates. The method can represent several local or distributed sources a nd does not need explicit a priori information. We evaluated the performanc e of the method using simulation studies. In a situation resembling typical magnetoencephalographic measurement, the mean estimated source strength ex ceeded 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 Pres s.