The relationship between conductivity uncertainties and EEG source localization accuracy.

The brain-to-skull conductivity ratio (BSCR) is an important parameter in EEG source imaging and localization. Misspecification of this value may introduce localization errors in the estimation of brain electrical activity. However, the effect of this ratio has not been well understood despite many investigations. In the present study, we conducted a series of computer simulations to investigate the relationship between BSCR and EEG source localization accuracy. Furthermore, we have attempted to correlate the localization accuracy of epileptogenic regions with the BSCR in epilepsy patients. Our results indicate that the dipole localization errors ranged from 10 to 20 mm. The localization accuracy resulting when the conductivity ratio used in the inverse calculation was set at 20 was better than those resulting when the ratio was set at 80 in epilepsy patients with a deep tumor. Future work is needed to validate this finding by experimental investigations in a large patient population.