Accuracy of two dipolar inverse algorithms applying reciprocity for forward calculation

Two inverse algorithms were applied for solving the EEG inverse problem ass uming a single dipole as a source model. For increasing the efficiency of t he forward computations the lead field approach based on the reciprocity th eorem was applied. This method provides a procedure to calculate the comput ationally heavy forward problem by a single solution for each EEG lead. A r ealistically shaped volume conductor model with five major tissue compartme nts was employed to obtain the lend fields of the standard 10-20 EEG electr ode system and the scalp potentials generated by simulated dipole sources. A least-squares method and a probability-based method were compared in thei r performance to reproduce the dipole source based on the reciprocal forwar d solution. The dipole localization errors were 0 to 9 mm and 2 to 22 mm wi thout and with added noise in the simulated data, respectively. The two dif ferent inverse al algorithms operated mainly very similarly. The lead field method appeared applicable for the solution of the inverse problem and esp ecially useful when a number of sources, e.g., multiple EEG time instances, must be solved. (C) 2000 Academic Press.