Coordinated manibular and head-neck movements during jaw opening-closing activities suggest a close functionallinkage between the jaw (Th and the neck regions. The present study al., investigated whether size and texture of bolus can texl intluence head-neck behavior during chewing. Ho' Using an optoelectronic 3-D recording technique, et , we analyzed concomitant mandibular and head- and neck movements in 12 healthy adults chewing small (3 g) and large (9 g) boluses of chewing resl gum and Optosil. The main finding was a head sim extension during chewing, the amount of which cer' was related mainly to bolus size. Furthermore, suc each chewing cycle was accompanied not only by ya" mandibular movements, but a1so by head mol extension-flexion movements. Larger head the movement amplitudes were correlated with larger but size and, to some extent, also with harder texture yet of the bolus. The results suggest that head-neck of t behavior during chewing is modulated in response acCI to changes in jaw sensory-motor input.