Abstract
The purpose of this study was to investigate electromyographically the reflex control of the oral sensation on sucking movements in infants and adults. During bottle feeding in infants, the activities of the masseter and the suprahyoid muscles were recorded, and they were altered depending on the flow quantity of the nutrient milk. The activities of muscles being recorded were enhanced and the cycle duration of the movement was prolonged when the milk flow was increased.
During simulation of bottle feeding in adults, the electromyograms (EMGs) of the muscles and the tongue movements, recorded by the fluorograph (X-ray TV system), were observed to be nearly similar to those during the bottle feeding of infants. In adults, the EMG activities of the muscles were also enhanced by increment of the milk flow.
Local anesthesia was performed on the adults to investigate the effects of oral sensation on the simulated sucking movements. The changes of the EMG activities were analysed during simulated movements, after the local anesthesia had penetrated into the periodontium of the upper and lower incisors and canines, the hard palate, and both the upper and lower lips. After the anesthesia of the palate and/or the lips, the EMG activities of the suprahyoid muscles decreased during movements. The activities of the masseter muscles conversely increased, after the anesthesia of the lips. After the palate and the lips were anesthetized, inspite of increment of the milk flow, the activities of the muscles being recorded were not enhanced.
These results indicate that the sucking movements are controlled by oral sensation. It is also considered that the oral sensation from the palate and the lips facilitates the activities of the suprahyoid muscles which have been elucidated to play more active role in the sucking movement than the jawclosing muscles.
