Source localization of auditory evoked magnetic fields during waking and sleep stages

We developed a high sensitive DC-SQUID system with a first-order gradiometer. This study focuses on the source location of brain electrical activities, in particular on the sources of auditory-evoked responses during sleep using magnetic field measurements by our SQUID system. We investigated the relationships between the sources of auditory evoked responses and sleep stages. Sources of N100 components, which appeared at about 100 msec after stimulation, and P200 components, which appeared at about 200 msec were estimated during waking and sleep stages. It was revealed that the sources of N100 and P200 components were different in each sleep stage. Sources of the N330 component, which appeared 330 msec after stimulation, were also investigated. Both MEG and EEG measurements made it clear that sources of the N330 component are modeled by multiple dipoles which diffuse in the cortex.<>