Measurements of extremely low frequency brain magnetic fields associated with four-tone memory processes

Recently magnetic-field measurements of the brain have become a useful tool to study higher brain function. The purpose of this study is to propose source models of both the memorizing process and the recognition process. The components of magnetic fields perpendicular to the surface of the head were measured by using a whole cortex type of DC SQUID with a third-derivative gradiometer. The authors observed the extremely slow components of MEG activities during both the memorizing process and the recognition process. They estimated the sources using two current dipoles, and compared the two cases