# Anomalous frequency-dependent ionic conductivity of lesion-laden human-brain tissue

## TL;DR

This study investigates how brain lesions affect ionic conductivity measurements, revealing that most lesion-affected tissues show increased conductivity with frequency, while some show decreased conductivity due to sodium ion trapping.

## Contribution

It introduces a novel frequency-dependent analysis of ionic conductivity in lesion-laden brain tissue, linking electrical behavior to specific pathological features.

## Key findings

- Most samples show increased conductivity with frequency.
- Some samples exhibit decreased conductivity with frequency.
- Frequency dependence correlates with lesion severity.

## Abstract

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.

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Source: https://tomesphere.com/paper/1706.01775