Magnetoencephalographic analysis of verbal generation and expression-related neural mechanisms using capping verses, “SHIRITORI” paradigm

This time we tried to analyze verbal generation mechanisms using external cue-paced capping paradigm, called “SHIRITORI” in Japanese. Responses of control session (passive hearing of tone or viewing of flash stimuli, which were used as cue stimuli in the paradigm session) and paradigm session (mental generation of words one by one according to “SHIRITORI” manner immediately after each cue stimulus emission) were recorded by magnetoencephalography (MEG), then analyzed after off-line averaging. Root mean square of averaged magnetic fields in the paradigm session delineated its increase at some latencies as compared with the control, which latencies after flash and tone stimulus onset ranged from 380 to 930 ms and 300 to 820 ms, respectively. In addition, estimated dipoles of these latencies were located to some language-related area of left hemisphere reported conventional PET and fMRI studies, including frontal operculum, fusiform and posteroinferor temporal region. Although our paradigm is necessary to be further refined, our results indicate that some of neural mechanisms specifically activated through words generation may be detectable via this paradigm.