Model estimates of CSF and skull influences on scalp-recorded ERPs.

Dipole source localization promises to enhance knowledge about the structural and functional processes underlying differences in scalp-recorded ERPs observed between normal and patient populations. In this paper the Cuffin and Cohen (1) four-compartment model of volume conduction is used to examine the effects of variations in size of different compartments on scalp-recorded potentials. Using single discrete current dipoles located various distances from the center of the head, the effect of varying the thickness of the superficial extra-sulcal subarachnoid layer of CSF and the thickness of the skull are examined. Changing the thickness of the CSF layer alters amplitude recorded at the scalp and also alters the topographic distribution of the potential; these effects are more pronounced the closer the dipole source is to the surface. Changes in skull thickness have similar, but even greater effects.