We study the effect of lesions on our four-electrode measurements of the ionic conductivity of (1 cm3) samples of human brain excised from patients undergoing pediatric epilepsy surgery. For most (about 94 %) samples the low-frequency ionic conductivity rises upon increasing the applied frequency. We attributed this behavior to the long-range (0.4 mm) diffusion of solvated sodium cations before encountering impenetrable blockages such as cell membranes, blood vessels and cell walls. By contrast, the low-frequency ionic conductivity of some (6 %) brain tissue samples falls with increasing applied frequency. We attribute this unusual frequency-dependence to the electric-field induced liberation of sodium cations from traps introduced by the unusually severe pathology observed in samples from these patients. Thus, the anomalous frequency-dependence of the ionic conductivity indicates trap-producing brain lesions.
@article{arxiv.1706.01775,
title = {Anomalous frequency-dependent ionic conductivity of lesion-laden human-brain tissue},
author = {David Emin and Massoud Akhtari and Aria Fallah and Harry V. Vinters and Gary W. Mathern},
journal= {arXiv preprint arXiv:1706.01775},
year = {2017}
}