1. A machine-implemented method for enhancing EEG or MEG information related to a selected behavioral activity in a subject, comprising attaching to the subject, a two-dimensional array of at least about 16 sensors for recording EEG or MEG traces from the subject, where the sensors are spaced from one another a distance which is substantially no greater than one-half the shortest expected spatial wavelength which is related to the selected behavioral activity, and where the area of placement of the array is one in which signals related to the selected activity can be detected by each sensor in the array, recording test EEG or MEG traces by the sensors over a period in which the selected behavior is manifested, selecting a test time interval within the recording period when such activity is occurring; decomposing the recorded traces into a series of basis functions B.sub.i, each of which represents a signal or clutter component which is present to various degrees in all of the traces recorded by the array sensors in the selected test interval, determining, for at least one signal basis function B.sub.j that is related to the selected behavioral activity, an amplitude matrix A.sub.j which represents the spatial pattern of amplitudes of that basis function, as measured by the individual sensors in the array, in the selected test interval, and representing test signals S.sub.a recorded during the test interval by the array of sensors in the form: EQU S.sub.a =.SIGMA..sub.j A.sub.j B.sub.j (basis functions).