An array of electrodes is applied to an internal or external surface of a biological system such as a human being. The electrodes generate signals which are processed to compute a surface differential of the surface potential at a multiplicity of spatial locations within a given time epoch. The signal...http://www.google.com/patents/US5146926?utm_source=gb-gplus-sharePatent US5146926 - Method and apparatus for imaging electrical activity in a biological system
