Abstract
In order to clarify mechanisms of swallowing initiation and patterns of swallowing motor sequence, numerous physiological studies have been done over the decades. In human studies, electromyographic and kinesiological recordings of related muscles/organs are commonly employed. The present study aimed at analyzing the effects of liquid stimulation applied to the pharynx on swallowing behaviors by means of simultaneous measurement of laryngeal movement and electromyogram of suprahyoid muscles. Both voluntary and involuntary swallowings were recorded during pharyngeal liquid stimulation using distilled water or 0.3 M NaCl solution in ten healthy volunteers. During voluntary swallow, we found the difference in the the first phase of laryngeal elevation between the liquids, in that the time duration of the first phase was shorter in swallowing of distilled water than that of NaCl solution. Between voluntary and involuntary swallows, the time duration of the first phase was longer while that of the second phase was shorter in voluntary swallow. The results suggest that the first phase of laryngeal elevation may represent effort of elevation of hyolaryngeal complex to initiate pharyngeal swallowing while the second phase may represent transition from voluntary component of movement to reflexively evoked movement.
