Effect of skull inhomogeneities on EEG localization accuracy

The accuracy of the head model affects on the solutions of the EEG inverse problems. If a simple three-sphere model and standard conductivity values for brain, skull and scalp regions are used, significant errors may occur. One of the most sensitive head model parameters is the conductivity of the skull. A realistic three-dimensional finite-element model provides a method to study the effect of inhomogeneities of the skull on the estimates of EEG inverse problems. In this paper effect of a skull conductivity inhomogeneity on dipole localization accuracy and on cortical potential estimation are analysed by computer simulations. It is shown that if inhomogeneity of the skull conductivity is not taken into account, localization errors that are approximately 1 cm can be encountered in the equivalent current dipole estimation and in the cortical potential estimation.