+ zyxwv Human Brain Mapping 4199-209(1996) + zy Coregistration of EEG and fMRI in a Simple Motor Task Christian Gerloff, Wolfgang Grodd, Eckart Altenmiiller, Rupert Kolb, Thomas Naegele, Uwe Klose, Karsten Voigt, and JohannesDichgans zyx Departmenf zyxwvutsrq of Neurology (C.G., E.A., J. D.) and Department of Neuroradiology (W.G., R. K., T.N., U.K., K. V.), University of Tuebingen, 0-72076 Tuebingen, Germany + + Abstract: The purpose of this study was to waluate the adequacy of coregistration of movement-related cortical potentials (MRCPs) and functional magnetic resonance imaging (fMRI) data in the primary sensorimotor cortex. Data were acquired in four normal subjects during right and left simple index finger movements. In fMRI (single-slice, 1.5 Tesla, T2*-weighted FLASH sequence), contralateral primary motor (Ml) and primary sensory cortex (Sl) 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 sources were tangentially oriented. Their configuration was consistent with source locations in the anterior (Ml) and posterior (Sl) banks of the central sulcus. Accordingly, the M1 source generated the pre-movement, the S1 source largely the immediate post-movement MRCP component. Taken together, MRCP modelling and fMRI data indicated a phasic sequential activation pattern of mostly sulcal portions of contralateral M1 and S1. After coregistration of anatomical MRI, fMRI, and dipole modelling results, the average 3D-distance between fMRI activation areas and MRCP 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 ( - 17 mm) have been reported previously with MEG and PET or MRI. We conclude, therefore, that the combination of EEG and fMRI is a promising technique for validation of electrophysiological source models and for evaluation of human functional brain anatomy with both adequate spatial and temporal resolution. Key words: functional magnetic resonance imaging, movemrnt-related cortical potentials, dipole analysis, zy c 1996 wi~ey-~iss, he. topographic mapping, coregistration, sensorimotor cortex + + INTRODUCTION To study the cooperative activity of different brain areas involved in movement processing, methodolog- cal approaches with appropriate spatial and temporal resolution are important. Functional neuroimaging techniques such as positron emission tomography Received August 15,1996; accepted August 15,1996. Address reprint requests to Dr. Christian Gerloff, National Institutes of Health, NINDS, Human Motor Control Section, Building 10, Room 5N244 Bethesda, MD 20892. (PET) [Roland, 1984; Colebatch et al., 1991; Grafton et al., 1991; Mazziotta et al., 1991; Shibasaki et al., 1993; Deiber et al., 19961 and functional magnetic resonance imaging (fMRI) [Constable et al., 1993; Kim et al., 1993a,b; Rao et al., 1993; Boecker et al., 19941 provide excellent spatial accuracy (mm range), but have poor temporal resolution (seconds to minutes), and mea- sure neuronal activity quite indirectly through changes in regional cerebral blood flow (rCBF) and blood oxygenation levels (BOLD effects). Electrophysiologi- cal techniques such as EEG and magnetoencephalog- raphy (MEG) measure neuronal activity more directly z o 1996 Wiley-Liss, Inc.