Movement-related magnetic fields to tongue protrusion

Movement-related magnetic fields (MRFs) associated with tongue protrusion w ere measured in five normal subjects using a helmet-shaped magnetoencephalo graphy system. Bihemispherical two-dipolar patterns appeared from approxima tely -2000 or -1000 to 0 ms to the trigger signal indicating when protrusio n of the tongue tip reached the frontal part of the palate. Equivalent curr ent dipoles (ECDs) for the MRFs, were localized on the central sulcus, 14.4 +/- 6.1 min inferior (P < 0.0001) and 7.6 +/- 6.9 mm anterior (P < 0.01). to the ECD for the N20m in the somatosensory evoked fields for median nerve stimuli. The ECD orientations of MRFs were anterior and perpendicular to t he central sulcus. These results correspond to the movement-related potenti als for tongue protrusion previously recorded from subdural electrodes in p atients with epilepsy. Magnetoencephalography can be applied to analyze cor tical functions related to tongue movement with high resolution in time and space in normal subjects. (C) 2001 Academic Press.