Measurement of somatosensory evoked response using functional MR images and MEG

This study focuses on the comparison of characteristics of functional magnetic resonance imaging (fMRI) and magnetoencepalography (MEG). Activations of the primary somatosensory cortex were investigated using MEG and fMRI. A right thumb and a ring finger were stimulated by an electrical current pulse. Both MEG and fMRI identified expected anatomical regions of the primary somatosensory cortex. When the thumb and the ring finger were stimulated simultaneously, it was possible in fMRI to discriminate the area of the thumb and the ring finger in the primary somatosensory cortex. In MEG, a single current dipole model might fit with a sufficiently large correlation coefficient because two sources are closely located within 10 mm. It is difficult to discriminate two closely located dipoles, if no initial information is given.