Event Abstract Back to Event A Model and Numerical Tool to Simulate the Neuronal Extracellular Space Andres Agudelo Toro1* and Andreas Neef1 1 BCCN Göttingen, Germany Modeling the neuronal extracellular space is important for medical applications and research. Extracellular electrical stimulation (EES) in the form of transcranial magnetic stimulation (TMS) is a potential treatment for depression and a possible replacement for electroconvulsive therapy [1]. Deep brain stimulation for movement disorders, and closed loop stimulating devices for the treatment of epilepsy have demonstrated the benefits of EES [2,3]. EES treatments are considered more tolerable than pharmacotherapy as parameters can be tuned easier, have less side effects and no drug interactions. As a research tool, TMS has been used in humans to induce localized “virtual lesions” [4], and transcranial direct current stimulation has been used to induce excitability changes in motor cortex [5]. Extracellular recording of the local field potential (LFP) has been used empirically for decades in electro-physiology. Despite its successful and longstanding clinical application, the theoretical treatment of the extracellular space is still rather simplistic. Two independent approaches are currently used: the "activating function" and the "line source approximation". In the first, the electric potential in the extracellular space is calculated for the a stimulation source and this potential is then used to alter the potential of 1D neurites [6,7]. In the second approach, the neuron is treated as an array of point sources and these are used to calculate the LFP [8,9]. In both cases the feedback of the neuronal currents in the extracellular potential is neglected. For the study of EES and a more complete understanding of the sources of the LFP and its spectral properties it would be essential to consider the reciprocal interaction of neural activity and extracellular potential in complex geometries [8]. We present a model and a numerical tool that simulate the local potentials in extracellular and intracellular space, and alternatively the effect of electric or magnetic stimulation. The model can represent 2D and 3D membranes of arbitrary geometry and has been solved numerically for both cases. To model the electric field, a common particularization of the Maxwell's equations for biological tissues is used [10]. The membrane is treated as a special boundary where current flow is governed by the potential difference and ionic dynamics. To validate the model and the numerical tool, results are compared to well know 1D, 2D and 3D solutions of the cable and Poisson's equations.