Nuclear medical PET-study in the causal relationship between mastication and brain function in human evolutionary and developmental processes.

The principal author (Kubote 1995, 1997, 1998, 1999, 2000 a, b) has proposed that chewing food well from infancy will lead to a clear-headed and robust person, following which the same concept has been presented to the general public by the mass media. Unfortunately, however, there does not yet seem to be any direct evidence to support this claim. It is thus necessary to review mastication from the standpoint of the new concept of evidence-based medicine (EBM) and to create a new direction in medicodental research and treatment from the viewpoint of human evolution, because the causal relationship between mastication and brain function has never been clarified either in fossil science research or in the modem scientific bibliography. To confirm the human historical fossil record in regard to the causal relationship between the development of mastication and brain function in human evolutionary processes, the effect of gum chewing on brain reaction was examined in humans by means of a positron-emission tomography (PET) camera (Momose et al. 1997) after an antecubital intravenous injection of H215O. Powerful activation of the cortical cells was demonstrated in multiple cortical areas involving the marginal areas of the bilateral central sulci of the cerebral cortex (Fig. 1), and the activated areas coincided with our previous results in region of interest (ROI) analysis (Momose et al. 1887). Three-dimensionally, numerous cortical cells were shown to form nuclei on relief maps (Fig. 2). As diets and feeding habits changed in a stepwise manner from frugivorous to omnivorous via herbivorous and carnivorous over the lengthy progress of evolution, the brain concomitantly grew and the cranial capacity gradually increased in volume from 500 cm3, food from plant sources to animal sources (700 cm3), and then to both (1500 cm3), during the human evolutionary and developmental processes. Gradual increases in the cranial capacity of human fossils during the developmental stage have been demonstrated also by PET images of the human brain acquired by means of a PET camera and an antecubital intravenous injection of H215O during mastication that showed powerful activation of cortical cells in multiple areas. It could be concluded that human fossils give us concrete information on how to feed our children in the modern human life style from infancy to adulthood, so that we should bring children up by adhering to images of the principal feeding habits discovered during this research on human evolutionary and developmental processes.