Food properties modulate activities in posterior parietal and visual cortex during chewing.

Cross-modal interactions between sensory modalities may be necessary for recognition of chewing food by the invisible oral cavity to avoid damaging the tongue and/or oral mucosa. The present study used functional near-infrared spectroscopy to investigate whether the food properties hardness and size influence activities in the posterior parietal cortex and visual cortex during chewing performance in healthy individuals. It was found that an increase in food hardness enhanced both posterior parietal cortex and visual cortex activities, while an increase in food size enhanced activities in the same regions. These findings suggested a quantitative relationship of oral food properties with activities in the brain regions responsible for object recognition and visuospatial processing. It is thus concluded that heightened neural activities in the posterior parietal cortex and visual area reflect an increased demand for cross-modal representation of food properties related to chewing.