These figures show two views of an isosurface of the current magnitude due to bipolar stimulation of +/- 5mA on the surface of the brain (marked by spheres). The brain is modeled using a tetrahedral finite element mesh. Each tetrahedral element contains a conductivity tensor which describes how current will pass through that particular element. The model was built using a high resolution anatomical scan to describe the geometry. Diffusion tensor imaging was used to compute the conductivity tensors, which have the same eigenvectors and linearly scaled eigenvalues. The field solution is governed by Poisson's equation and was found using SCIRun software (Chris Johnson, University of Utah).
This model provides information about how injected current densities propogate through the the brain during direct electro-cortical stimulation (DECS) and how surrounding tissue is affected. The next step is to statistically compare these DECS results with fMRI activation maps in order validate the utility of fMRI for presurgical planning.