Experimental investigation into mechanism of development and learning process of masticatory function in growing period

Abstract

It has been suggested that experiences of chewing various kinds of food with different consistency contribute significantly to the development of the human masticatory function. Nevertheless, the modern human diet consists more and more of thoroughly processed and cooked foods, which dramatically reduce the demand on the stomatognathic system. The consequences of such a change in alimentary habits are not fully understood. In this study we used three-dimensional jaw-movement tracking device and jaw-muscle electromyography (EMG) to analyze changes in masticatory function in mice fed liquid or solid diets after weaning, and the hypothesis that the daily diet of soft food prevents the development of masticatory function was examined. As a result, we found that 1) The capacity to discriminate consistency of food is reduced in mice raised on liquid diet. 2) Patterns of jaw movement trajectories and masticatory rhythm were extremely unstable in liquid diet mice. 3) Either the masticatory central pattern generator (CPG) or its peripheral feedback mechanisms may be underdeveloped in animals raised on soft foodstuffs, although the conversion from sucking to chewing is not prevented.