Dipole source analysis for readiness potential and field using simultaneously measured EEG and MEG signals

Area of Science:

• Neuroscience
• Biophysics
• Medical Imaging

Background:

• Movement-related cortical potentials (MRCPs) precede self-paced movements, with generators localized using various techniques.
• Kornhuber and Decke discovered the surface negative potential preceding self-paced movement, a key finding in motor control research.

Purpose of the Study:

• To compare the source localization capabilities of electroencephalography (EEG) and magnetoencephalography (MEG) for movement-related potentials.
• To investigate the sensitivity of EEG and MEG to different source orientations (radial vs. tangential).
• To evaluate the impact of head modeling (spherical vs. realistic) on source analysis.

Main Methods:

• Simultaneous recording of multichannel EEG and MEG data from five healthy subjects during self-paced finger movements.
• Dipole source analysis applied independently to EEG, MEG, and combined data.
• Forward problem solved using boundary-element method for realistic head models and locally-fitted-sphere approach for spherical models.

Main Results:

• EEG predominantly localized radially oriented sources, while MEG localized tangential sources.
• Combined EEG and MEG analysis revealed the effect of MEG on EEG source reconstruction.
• Spherical and realistic head models yielded similar source localization results.

Conclusions:

• EEG and MEG possess complementary sensitivities to different cortical source orientations.
• Combined EEG-MEG analysis provides a more comprehensive understanding of motor-related cortical activity.
• Both spherical and realistic head models are viable for source analysis in this context.