Swallowing-related neural oscillation: An intracranial EEG study

Swallowing is a unique movement because orchestration of voluntary and involuntary movement is indispensable. The transition from voluntary swallowing to involuntary swallowing are executed on the order of milliseconds. We hypothesized that neural mechanism of it were revealed by cortical high frequency activities. Eight epileptic participants fitted with intracranial electrodes over the orofacial cortex were asked to swallow a water bolus, and cortical oscillatory changes including high {gamma} band (75-150 Hz) and {beta} band (13-30 Hz) were investigated at the time of mouth-opening, water-injection, and swallowing. High {gamma} power increases associated with mouth-opening were observed in the ventrolateral prefrontal cortex, with water-injection in the lateral central sulcus, and with swallowing in the region along the Sylvian fissure. Mouth-opening induced a {beta} power decreases, and the {beta} power decreases continued until completion of swallowing. The high {gamma} burst activity was focal and specific to swallowing, however, the {beta} activities were extensive and not specific to swallowing. At the boundary time between voluntary and involuntary swallowing, swallowing-related high {gamma} power achieved the peak, and subsequently, the power decreased. Using high {gamma} activities, we demonstrated three distinct activities related to mouth-opening, water-injection, and swallowing were induced at different timing. The peak of high {gamma} power related to swallowing suggests that during voluntary swallowing phase, the cortex is the main driving force for swallowing rather than the brain stem.