Evaluation of Performance for Human In-Vivo Conductivity Estimation from EEG and sEEG Recorded in Simultaneous with Intracerebral Electrical Stimulation

TL;DR

This study evaluates in-vivo human head tissue conductivity estimation using simultaneous EEG and sEEG recordings during intracerebral stimulation, highlighting variability based on measurement configurations and modalities.

Contribution

It provides new insights into how measurement setup affects conductivity estimates and offers guidelines for more accurate in-vivo conductivity determination.

Findings

Conductivity estimates vary with stimulation and measurement positions.

Different measurement modalities yield different conductivity values.

The study offers guidelines to improve in-vivo conductivity estimation.

Abstract

Assigning accurate conductivity values in human head models is an essential factor for performing precise electroencephalographic (EEG) source localization and targeting of transcranial electrical stimulation (TES). Unfortunately, the literature reports diverging conductivity values of the different tissues in the human head. The current study analyzes first the performance of in-vivo conductivity estimation for different configurations concerning the localization of the electrical source and measurement. Then, it presents conductivity estimates for three epileptic patients using scalp EEG and intracerebral stereotactic EEG (sEEG) acquired in simultaneous with intracerebral electrical stimulation. The estimates of the conductivities were based on finite-element models of the human head with five tissue compartments of homogeneous and isotropic conductivities. The results of this study show that in-vivo conductivity estimation can lead to different estimated conductivities for the same patient when considering different stimulation positions, different measurement positions or different measurement modalities (sEEG or EEG). This work provides important guidelines to in-vivo conductivity estimation and explains the variability among the conductivity values which have been reported in previous studies.