A holy grail of neuroimaging is direct mapping of neural activity, as the BOLD contrast used by fMRI is both spatially and temporally separated from active cells. Changes in membrane conductivity are actually a more promising contrast to use for imaging neural currents than other suggested methods such as neural current MRI, since membrane conductivity images are not prone to cancellation effects. We are developing of high field Magnetic Resonance Electrical Impedance Tomography (MREIT) techniques and models for this purpose, including full-field electromagnetic models of neural complexes that include active membrane behavior.
There has recently been a proliferation of new methods for modulating the brain’s electrical activity. Three examples are Deep Brain Stimulation (DBS), transcranial DC stimulation (tDCS) and vagus nerve stimulation. While applications and scenarios of these vary, no consistent explanation of the mechanism of these therapies exists. Our present work includes detailed modeling of DBS and tDCS using finite element methods. The state-of-the-art in modeling is inclusion of white matter anisotropy in brain tissue models. While we use these models we are also developing methods of directly imaging current flow using a variation on MRI-based methods developed in the early 1990s.
Hemorrhage inside the brain’s ventricles affects approximately 50% of premature newborns at gestational ages less than 33 weeks. As methods to limit this often fatal or disabling condition are developed, the need for early detection becomes crucial. Many cases involving low levels of intraventricular hemorrhage (< 50% ventricular filling) are missed by transcranial ultrasound. We have used spherical and realistic geometry phantoms to test the sensitivity of our different measurement protocols to ventricular blood.