Analysis of cortical activation of silent vocalization using MEG

To explore the cortical activation of vocalization, we measured evoked magnetic fields (EFs) related to time-locked imaginary vocalization using magnetoencephalography (MEG). We demonstrated a unique procedure which synchronized auditory stimuli with visually presented images, and made comparisons before and after imaginary vocalization. Since MEG measurements have high temporal resolution, we used visual stimuli for subjects who have the timing of silent articulation, and subtracted responses in each case. With this paradigm, brain activities of the right frontotemporal region and right insular area were detected at a latency of around 160 ms. These activations were thought to be the initial brain activity of human vocalization.