Effect of taste on brain blood flow and masticatory movement

Objectives: The purpose of this experiment was to clarify the effect of the taste of food on the brain blood flow and masticatory movement. Methods: Ten healthy subjects in their twenties (5 males and 5 females, average age 25.6 years) were asked to chew three types of gummy jelly (regular, moderately bitter with 0.016% quinine, and bitter with 0.032% quinine) on their habitual side for 20 seconds. The masseter muscular activity and blood flow in the brain were recorded simultaneously using EMG and NIRS (Near-Infrared Spectroscopy). The measuring probe was placed on the skin over the cortical masticatory area. The number of cycles, integral value of masseter muscular activity and the amount of change in the blood flow during the first half of chewing and the latter half of chewing were calculated separately. The results were compared among the three types of foods. Results: During the first half of chewing, the number of cycles, integral value of the masseter muscular activity and the amount of change in the blood flow were not significantly different among the foods. During the latter half of chewing, although the integral value was not significantly different among the foods (regular: 27.0mV•msec, moderate bitter: 27.2mV•msec, bitter: 27.7mV•msec, F=0.270, p>0.05, n.s.), the number of cycles and amount of change in the blood flow were the smallest during chewing of the bitter gummy jelly and largest during chewing of the regular gummy jelly, thus, significant differences were found among the foods (number of cycles: F=9.239, p<0.05, s, amount of change in the blood flow: F=23.899, p<0.05, s). Conclusions: From these results it was suggested that the taste of food affected the brain blood flow and the masticatory movement without changing the level of muscular activity.