Spatiotemporal source analysis of vocalization-associated magnetic fields

The vocalization-related cortical fields (VRCF) following vowel vocalizatio n were studied by magnetoencephalography (MEG) in eight normal subjects. A multiple-source model, BESA (Brain Electric Source Analysis), was applied t o elucidate the generating mechanism of VRCF in the period from 150 ms befo re to 150 ms after the onset of vocalization. Six sources provided satisfac tory solutions for VRCF activities during that period. Sources 1 and 2, whi ch were activated from approximately 150 ms before the vocalization onset, were located in laryngeal motor areas of the left and right hemispheres, re spectively. Sources 5 and 6 were located in the truncal motor area in each hemisphere, and they were very similar to sources 1 and 2 in terms of tempo ral change of activities. Sources 3 and 4 were located in the auditory cort ices of the left and right hemispheres, respectively, and they appeared to be activated just after the vocalization onset. However, all six sources cl ,ere temporally overlapped in the period approximately 0-100 ms after the v ocalization onset. The present results suggested that the bilateral meter c ortices, probably laryngeal and truncal areas, were activated just before t he vocalization. We considered that the activities of the bilateral auditor y areas after the vocalization were the response of the subject's central a uditory system to his/her own voice. The motor and auditory activities were temporally overlapped, and BESA was very useful to separate the activities of each source. (C) 2000 Elsevier Science B.V. All rights reserved.