Linear estimation discriminates midline sources and a motor cortex contribution to the readiness potential

Area of Science:

• Neuroscience
• Motor Control
• Brain Imaging

Background:

• The readiness potential (RP) precedes voluntary movements, but its generators, specifically the roles of the supplementary motor area (SMA) and primary motor cortex, remain debated.
• Previous spatiotemporal dipole modeling studies have produced conflicting results regarding the precise contributions of these motor areas to the RP.

Purpose of the Study:

• To apply an alternative method, linear estimation theory, to investigate the neural sources of the readiness potential (RP).
• To differentiate the contributions of the supplementary motor area (SMA) and primary motor cortex to the RP preceding voluntary finger movements.

Main Methods:

• Electroencephalography (EEG) recordings from 28 electrodes using the extended 10-20 system.
• Linear estimation theory applied to RP data preceding fixed and freely selected finger movements.
• Spherical head model with 3 concentric spheres and current density reconstruction on a spherical surface.
• Lead field normalization applied for source analysis.

Main Results:

• The analysis successfully distinguished activity originating from both midline cortical areas (including the SMA) and the primary motor cortex.
• Evidence of separate contributions from midline sources and the motor cortex to the readiness potential was clearly identified.
• Reconstructed current densities showed activity patterns consistent with distinct generator locations.

Conclusions:

• Linear estimation theory provides a valuable approach for resolving the generators of the readiness potential.
• The study provides clear evidence for distinct contributions of the supplementary motor area and primary motor cortex to the RP.
• These findings help clarify the spatiotemporal dynamics of motor preparation in the human brain.