Spatio-temporal mapping of motor preparation for self-paced saccades.

We investigated the movement related cortical potentials (MRCPs) associated with self-paced horizontal voluntary saccades and evaluated their cortical sources by applying dipole model. A fixation point and two targets (6° of eccentricity in the left and right fields) were continuously displayed on a screen. A first group (15 subjects) performed a saccade toward one of the lateral targets immediately followed by a re-centering saccade. A second group (15 subjects) performed a saccade followed by a long fixation (few seconds) before a re-centering. Results showed a sequence of activities in contralateral Intra-Parietal Sulcus (IPS), Supplementary Eye Fields and Frontal Eye Fields. In the case of long-fixation-saccades, an additional source in ipsilateral IPS was detected in the planning phase. The amplitude and timing of the planning phase, associated with BP components, were influenced by task demands. Similarity and difference between MRCPs for eyes and limbs movements are also presented.