Generators of Movement-Related Cortical Potentials: fMRI-Constrained EEG Dipole Source Analysis

• Published in: NeuroImage (Orlando, Fla.) Fla.), 2002-09, Vol.17 (1), p.161-173
• Main Authors: Toma, Keiichiro, Matsuoka, Takahiro, Immisch, Ilka, Mima, Tatsuya, Waldvogel, Daniel, Koshy, Benjamin, Hanakawa, Takashi, Shill, Holly, Hallett, Mark
• Format: Article
• Language: English
• Subjects: Adult; Cerebral Cortex - physiology; Electroencephalography - statistics & numerical data; Electromyography; Female; Fingers - physiology; Humans; Image Processing, Computer-Assisted; Magnetic Resonance Imaging - methods; Magnetic Resonance Imaging - statistics & numerical data; Male; Middle Aged; Models, Neurological; Movement - physiology; Psychomotor Performance - physiology; Time Factors
• ISSN: 1053-8119; 1095-9572
• DOI: 10.1006/nimg.2002.1165

To clarify the precise location and timing of the motor cortical activation in voluntary movement, dipole source analysis integrating multiple constraints was conducted for the movement-related cortical potential (MRCP). Six healthy subjects performed single self-paced extensions of the right index finger at about 15-s intervals during EEG and event-related fMRI acquisitions. EEG was recorded from 58 scalp electrodes, and fMRI of the entire brain was obtained every 2.6 s. Coordinates of the two methods were coregistered using anatomical landmarks. During dipole source modeling, a realistic three-layer head model was used as a volume conductor. To identify the number of uncorrelated sources in the MRCP, principal component (PC) analysis was performed, which was consistent with the existence of six sources in the left (Lt SM1) and right (Rt SM1) sensorimotor and medial frontocentral (MFC) areas. After dipoles were seeded at the activated spots revealed by fMRI, dipole orientations were fixed based on the interpretation of the topography of distribution of the PC. The strength of the six dipoles (three dipoles in Lt SM1, two in Rt SM1, and one in MFC) was then computed over time. Within the bilateral SM1, activation of the precentral gyrus occurs bilaterally with similar strength from −1.2 s, followed by that of the precentral bank from −0.5 s with contralateral preponderance. Subsequently, the postcentral bank becomes active only on the contralateral side at 0.1 s after movement. Activation of the MFC shows timing similar to that of the bilateral precentral gyri. These deduced patterns of activation are consistent with previous studies of electrocorticography in humans.