COREGISTRATION OF EEG AND FMRI IN A SIMPLE MOTOR TASK

The purpose of this study was to evaluate the adequacy of coregistrati on of movement-related cortical potentials (MRCPs) and functional magn etic resonance imaging (fMRI) data in the primary sensorimotor cortex. Data were acquired in four normal subjects during right and left simp le index finger movements. In fMRI (single-slice, 1.5 Tesla, T2-weigh ted FLASH sequence), contralateral primary motor (M1) and primary sens ory cortex (S1) were activated in all subjects. Spatiotemporal dipole modelling of electric MRCP generators (BESA) revealed two main sources in the central region contralateral to the moving finger. Both source s were tangentially oriented. Their configuration was consistent with source locations in the anterior (M1) and posterior (S1) banks of the central sulcus. Accordingly, the M1 source generated the pre-movement, the S1 source largely the immediate post-movement MRCP component. Tak en together, MRCP modelling and fMRI data indicated a phasic sequentia l activation pattern of mostly sulcal portions of contralateral M1 and S1. After coregistration of anatomical MRT, fMRI, and dipole modellin g results, the average 3D-distance between fMRI activation areas and M RCP source locations was 18.6 mm (SD 7.6), with the largest deviation in the anterior-posterior direction (12.1 +/- 9.5 mm). Coregistration inaccuracies of similar magnitude (similar to 17 mm) have been reporte d previously with MEG and PET or fMRI. We conclude, therefore, that th e combination of EEG and fMRI is a promising technique for validation of electrophysiological source models and for evaluation of human func tional brain anatomy with both adequate spatial and temporal resolutio n. (C) 1996 Wiley-Liss, Inc.