LINEAR-ESTIMATION DISCRIMINATES MIDLINE SOURCES AND A MOTOR CORTEX CONTRIBUTION TO THE READINESS POTENTIAL

Spatiotemporal dipole modelling of the generators of the readiness pot ential (RP) prior to voluntary movements has yielded diverging results concerning the contributions of supplementary motor area (SMA) and pr imary motor cortex. We applied an alternative approach (i.e, linear es timation theory) to measurements of the RP preceding fixed and freely selected finger movements, measured at 28 electrodes of the extended 1 0-20 system. The volume conductor properties of the head were modelled by 3 concentric spheres. Current densities were reconstructed on a sp herical surface, placed at a depth of 5 mm from the inside of the skul l. Lead field normalization was applied. The analysis shows activity o n the midline as well as near the primary motor area. Although some fe atures of the reconstructions are not readily interpretable, separate contributions of midline sources (including presumably SMA) and motor cortex to the RP are clearly distinguished.