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1.1 Bioelectric Volume Conductors     continued...

A similar but more complicated process of depolarization occurs in the brain. While it too undergoes an activation process, the propagation occurs in a less continuous manner than in the heart. In the brain, the individual neurons determine the path that activation takes. Thus the activation process in the brain is inherently discontinuous.

Because is, in general, time-varying, the resulting field quantities are governed by Maxwell's equations. For a discussion on modeling the wave propagation through active myocardial tissue, the reader is directed to [9,10,11,12,13]. For the macroscopic volume conductor problem (in which we do not consider the individual membrane currents), we can utilize a quasi-static approximation. Because the displacement current, (), is much smaller than the conduction current, (), propagation effects are negligible, and inductive effects are minute [7].