Variation in Reported Human Head Tissue Electrical Conductivity Values

Abstract

Overview

Electromagnetic source characterisation necessitates precise models representing head geometry and electrical conductivity fields. Traditionally, head tissue conductivity has relied on previous literature values, which are often inconsistent despite extensive research.

Findings

A comprehensive meta-analysis was conducted reviewing 3121 publications across three databases, of which 56 papers were used for data extraction. Electrical conductivity was analyzed across different tissue types and recorded under various conditions such as methodology, measurement condition, current frequency, and tissue temperature. Highlighted findings include significant variations in electrical conductivity depending on factors like demographics and methodology.

• Whole skull conductivity: 0.02 S/m
• Spongiform layer: 0.048 S/m
• Inner compact layer: 0.007 S/m
• Outer compact layer: 0.005 S/m
• CSF: 1.71 S/m
• Grey matter: 0.47 S/m
• White matter: 0.22 S/m
• Brain-to-skull conductivity ratio (BSCR): 50.4

Conclusion

Given the variation observed, it is imperative to employ caution in creating volume conductor models, ideally personalizing them rather than using assumptive literature values. In cases where individual models are not feasible, weighted averages from this meta-analysis are recommended.