Spatial empirical orthogonal functions of multichannel visual evoked response

Simulated and real visual evoked EEG data were used to study the use of empirical orthogonal functions to describe spatial EEG properties. Sixteen channels of EEG data were recorded from the back of the head during visual checkerboard stimulation. From these data the sum of cross products was obtained at discrete time intervals before and after the stimulus. The empirical orthogonal functions are the eigenvectors of the cross product matrix and their coefficients are the square roots of the corresponding eigenvalues.<>