[The effect of food consistency on conditioned avoidance response in mice and rats].

The purpose of this study was to examine the effects of chewing a hard and soft diet on acquisition of conditioned avoidance response in mice and rats. 76 C57BL mice and 38 Wistar rats were divided into 2 groups respectively 20 days after birth. One group was fed a solid diet and another was fed a powder diet containing the same components as the solid one (Nihon Crea Company, CE-2). Using the avoidance conditioning system of Gunma University, conditioned avoidance experiments started at the age of 8 weeks and the rate of avoidance (number of avoidance/number of trials) was measured. The mean percentage of avoidance rates in the solid diet group were significantly higher than those of powder diet group at level of 1% in mice and 5% in rats. These results suggest that mastication of a hard diet in younger animal may facilitate their brain function more than that of a soft diet.