A Mahnam - Visiting Research Scholar in the Department of Biomedical Engineering, Pratt School of Engineering, Duke University, NC, USA as part of his PhD program at Faculty of Biomedical Engineering, Amirkabir University of Technology, Tehran, IRAN
S.M.R. Hashemi - Faculty of Biomedical Engineering, Amirkabir University of Technology, Tehran, IRAN
W.M. Grill - Department of Biomedical Engineering, Pratt School of Engineering, Duke University, NC, USA

For more than a century, electrical stimulation of neural tissue has been in use experimentally and clinically for a wide range of purposes. In many applications of electrical stimulation, it is important to know the spatial extent of neural activation in response to the stimulation. The refractory interaction technique is a method that exploits the interaction between the regions of activation produced by two electrodes when the second stimulus is delivered while neurons in the region activated by the first electrode are in their refractory phase. We proposed a new method to estimate the current-distance relationship based on the refractory interaction technique. We evaluated this method using computer-based simulations of electrical stimulation and demonstrated the applicability and accuracy of the method for measuring the spatial extent of activation.