Shourei Prize 2. Utility of TMS for neuroscience of speech

Publication date: May 2018
Source:Clinical Neurophysiology, Volume 129, Issue 5
Author(s): Takenobu Murakami
Transcranial magnetic stimulation (TMS) has widely been accepted as a useful method of non-invasive brain stimulation in neuroscience. Compared with neuroimaging and intraoperative mapping, the number of speech experiments using TMS has, however, still been small. Here, an introduction to recent TMS studies that explored speech perception and imitation is presented. Single-pulse TMS of the primary motor cortex (M1) showed a speech specific and topographically specific increase of excitability in the M1 lip area during speech perception. This may be explainable by the motor theory of speech perception and reflect the function of mirror neurons. The updated speech model is constituted of dual speech processing streams; dorsal and ventral streams. A paired-coil stimulation demonstrates an increase in the effective connectivity from brain regions in the dorsal stream to the M1 lip area. Application of repetitive TMS (rTMS) to parts of the dorsal stream can modulate performance of phonological recognition, whereas semantic perception is altered by rTMS over the ventral pathway. Speech imitation combined with facilitatory rTMS over the left posterior inferior frontal gyrus can enhance accuracy of imitation performance. In summary, TMS is an innovative tool to understand the brain network of speech processing on perception and imitation.



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