We have demonstrated that intraoperatively acquired cortical surface geometric data can be used to: improve image-to-patient alignment, measure brain deformations, and drive a computational approach to brain shift correction during image-guided neurosurgery. In this project, we take the final step of extensive intraoperative validation and independent testing. The hypothesis to be tested is that computer models, cortical surface geometric data, and tracked stylus digitization technology when used to compensate for deformation during image-guided brain tumor surgery can predict the locations of eloquent brain surround pathology such that this approach is an effective surrogate to intraoperative magnetic resonance (iMR) imaging.