Changes in oral functions focusing on the development and decline of feeding activities

―To elucidate the mechanism of dysphagia―

Abstract

　In humans, feeding activities start with lactation, promoting infantile swallowing, which is replaced by weaning to solids at around 5 to 6 months after birth, when neonatal reflexes disappear. Subsequently, during the period of cerebral development when adult swallowing is achieved (the initial, middle, and late weaning periods), oral functions change along with changes in feeding styles. In short, the diversification of tongue motions and tooth eruption, leading to occlusal development, enable us to achieve mastication as a coordinated oral movement allowing food bolus formation.　On the other hand, when food bolus formation becomes difficult due to an age-related decline in oral functions, the incidence of dysphagia, such as aspiration and suffocation, increases, forcing a large number of the elderly to shift their daily diet to special formulations, such as those for weaning.　Such similarities of oral functions and feeding styles between the periods of development and decline have frequently been reported.