Experimental tests of EEG source localization accuracy in spherical head models.

Area of Science:

• Neuroscience
• Biophysics
• Medical Imaging

Background:

• Electroencephalography (EEG) is a non-invasive technique used to estimate the location of electrical sources within the brain.
• The accuracy of EEG-based source localization is often limited due to the lack of ground truth data for validating calculated positions.
• Previous studies have faced challenges in precisely quantifying localization errors.

Purpose of the Study:

• To quantitatively assess the accuracy of brain electrical source localization using EEG data.
• To determine the impact of skull conductivity on localization error in a controlled experimental setup.
• To establish a benchmark for localization accuracy achievable with current spherical head models.

Main Methods:

• Current was injected into implanted electrodes in human subjects to create known electrical sources.
• Computed Tomography (CT) scans were used to precisely determine electrode locations.
• EEG signals were recorded and analyzed using spherical head models with varying skull conductivity ratios (1/80, 1/40, 1/20) to calculate source locations.

Main Results:

• An average localization error of 10.6 mm (SD=5.5 mm) was observed with a skull conductivity ratio of 1/40.
• Localization errors for superior and inferior sources showed slight variations but no significant differences in accuracy between deep and superficial sources.
• The chosen skull conductivity ratio had a minimal impact on the overall average localization error.

Conclusions:

• The best achievable average localization accuracy using spherical head models is approximately 10 mm.
• Achieving higher precision in brain source localization necessitates the development and application of more sophisticated and realistic head models.
• This study provides crucial data for understanding the limitations of current EEG source localization techniques.