The electrical conductivity value of the human skull is important for biophysics research of the brain. In the present study, the human brain-to-skull conductivity ratio was estimated through in vivo experiments utilizing intracranial electrical stimulation in two epilepsy patients. A realistic geometry inhomogeneous head model including the implanted silastic grids was constructed with the aid of the finite element method, and used to estimate the conductivity ratio. Averaging over 49 sets of measurements, the mean value and standard deviation of the brain-to-skull conductivity ratio were found to be 18.7 and 2.1, respectively.
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The authors are grateful to Lei Ding for useful discussions. This work was supported in part by NIH RO1 EB00178, NSF BES-0411898, NSF BES-0602957, and partly supported by the Supercomputing Institute of the University of Minnesota.