Estimating regional brain activity from evoked potential fields on the scalp

Potential fields on the surface of the brain were estimated from discretely sampled scalp fields in human subjects. Relatively simple methods of linear algebra were combined with detailed anatomical information from magnetic resonance imaging. The method was verified using a tank model of the human head that encased a fully hydrated human skull in a polymer matrix of controlled resistivity matching that of human brain and scalp. Brain surface fields evoked by checkerboard contrast reversal spread less than their scalp field counterparts, and provided information helpful in localizing brain activity.