Feed-forward-related neural activity for vocalization: A pilot study using magnetoencephalography

The present pilot study was aimed to clarifying neural activity related with the feed-forward function, sensory-motor integration processed before motor performance. Brain magnetic fields were recorded using a whole-head magnetoencephalography system before vocalization under various levels of surrounding noise in nine healthy volunteers. Participants were instructed to read a word presented on a monitor under auditory conditions with white noise of 60, 80, and 100-dB. The vocal strength of the participants significantly increased with an increase in the intensity of environmental noise. Neural connectivity associated with coherence was calculated among the vocalization-related brain areas selected: truncal area in the primary motor area (M1), premotor area (PM), supplementary motor area (SMA), posterior inferior frontal area (pIF), and posterior part of the superior temporal area (pST). Coherence between M1 and pIF in the frontal cortex without vocalization and auditory pST in the temporal area before vocalization was negatively correlated with the level of environmental noise and vocal strength, respectively. We considered that the findings in this pilot study are, at least partially, relevant to the feed-forward function for vocalization.