Investigation of Electrical Conductivity Changes during Brain Functional Activity in 3T MRI

TL;DR

This study investigates the relationship between brain activity and electrical conductivity changes during fMRI, revealing consistent patterns of conductivity decrease in active regions and supporting the potential for in-vivo electrical property measurement during brain function.

Contribution

The paper demonstrates in-vivo electrical conductivity changes during brain activity using phase-based electrical properties tomography, linking these changes to fMRI signals and validating with electromagnetic simulations.

Findings

Conductivity decreases in active brain regions during fMRI

B1 phase mapping shows positive correlation with activation

Simulations support observed conductivity and phase changes

Abstract

Blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) is widely used to visualize brain activation regions by detecting hemodynamic responses associated with increased metabolic demand. While alternative MRI methods have been employed to monitor functional activities, the investigation of in-vivo electrical property changes during brain function remains limited. In this study, we explored the relationship between fMRI signals and electrical conductivity (measured at the Larmor frequency) changes using phase-based electrical properties tomography (EPT). Our results revealed consistent patterns: conductivity changes showed negative correlations, with conductivity decreasing in the functionally active regions whereas B1 phase mapping exhibited positive correlations around activation regions. These observations were consistent across both motor and visual cortex activations. To further substantiate these findings, we conducted electromagnetic radio-frequency simulations that modeled activation states with varying conductivity, which demonstrated trends similar to our in-vivo results for both B1 phase and conductivity. These findings suggest that in-vivo electrical conductivity changes can indeed be measured during brain activity. However, further investigation is needed to fully understand the underlying mechanisms driving these measurements.