Fig. 12. Lingual strain during human swallowing. Direction-dependent strain fields were acquired for the mid-sagittal slice of the tongue during the phases of the swallow, including early accommodation (top row), late accommodation (middle row) and propulsion (bottom row). During early accommodation, bolus containment is associated with negative y-direction strain, consistent with a synergistic contraction of the anterior genioglossus and hyoglossus, with concomitant x- and z-direction expansion. During late accommodation, the combination of y-direction contraction in the posterior tongue and expansion in the anterior tongue results in shifting of the bolus to the posterior dorsal surface of the tongue, consistent principally with contraction of the posterior genioglossus and concomitant x- and z-direction expansion. During propulsion, x- and y-direction expansion in the posterior tongue was consistent with contraction of the laterally inserted styloglossus (with associated passive drag) and z-direction contraction of the posteriorly located transversus fibers. (Reproduced with permission from Napadow et al., 1999b.)