Electric Field Encephalography as a Tool for Functional Brain Research: A Modeling Study

Abstract

We introduce the notion of Electric Field Encephalography (EFEG) based on measuring electric fields of the brain and demonstrate, using computer modeling, that given the appropriate electric field sensors this technique may have significant advantages over the current EEG technique. Unlike EEG, EFEG can be used to measure brain activity in a contactless and reference-free manner at significant distances from the head surface. Principal component analysis using simulated cortical sources demonstrated that electric field sensors positioned 3 cm away from the scalp and characterized by the same signal-to-noise ratio as EEG sensors provided the same number of uncorrelated signals as scalp EEG. When positioned on the scalp, EFEG sensors provided 2–3 times more uncorrelated signals. This significant increase in the number of uncorrelated signals can be used for more accurate assessment of brain states for non-invasive brain-computer interfaces and neurofeedback applications. It also may lead to major improvements in source localization precision. Source localization simulations for the spherical and Boundary Element Method (BEM) head models demonstrated that the localization errors are reduced two-fold when using electric fields instead of electric potentials. We have identified several techniques that could be adapted for the measurement of the electric field vector required for EFEG and anticipate that this study will stimulate new experimental approaches to utilize this new tool for functional brain research.

Unified Expression of the Quasi-Static Electromagnetic Field: Demonstration With MEG and EEG Signals

“…In practice, EEG is the dominating measurement of the electric properties produced by the brain, but these results indicate that spatially more informative data could possibly be obtained by measuring the vector-valued electric field rather than the scalar electric potential. Previous simulation studies are in agreement with this conclusion [26]. One can estimate the electric field from the electric potential measurement by applying a spatial derivative operation to the EEG signal [36], but further studies are needed to investigate whether this approach yields similar information as the actual measurement of the electric field with distinct sensors with varying locations and orientations.…”

“…However, to our knowledge measurements of brain-related electric field have never been conducted but there are some earlier simulation studies supporting the interpretation of our mathematical theory. Specifically, Petrov and Sridhar [26] demonstrated more focal neural source reconstruction when inverse modeling was based on the measurement of the electric field instead of the potential distribution.…”

Portable System for Neuro-Optical Diagnostics Using Virtual Reality Display

“…The NeuroDot sensor is unique in that it can be operated simultaneously in regular EEG mode, as well as the new electric field encephalography (EFEG) mode which can provide enhancements in signal quality and can drastically improve the sensitivity of paradigms that probe the limits of visual function. 14,16,17 Each NeuroDot sensor array comprises 4 small-diameter biopotential electrode pins arranged in a grid with a small spacing of 1.5 cm (considered to be "ultra" or "very" high-density 17,18 ). The NeuroDotVR system (Fig.…”

Electric field encephalography for brain activity monitoring

“…While impressive progress has been made in developing wireless EEG platforms in the US [3][4][5] and abroad [6][7][8][9], even the latest commercially available portable systems are challenging to use in less controlled clinical and research settings. The previous theoretical and computational modelling work of our collaborators [10] suggests that measuring the electric fields generated by neuroelectric activity could provide higher information density (more signals that are less correlated) and better source localization for a given area of scalp coverage. This paper introduced the term 'electric field encephalography' (EFEG) to the peer-reviewed literature, describing neuroelectric field based measurement and data processing techniques; a predated patent application [11] discloses implementation details of relevance to EFEG measurement apparatus.…”