Data from: Twist and chew: three dimensional tongue kinematics during chewing in macaque primates

Three-dimensional (3D) tongue movements are central to performance of
feeding functions by mammals and other tetrapods, but 3D tongue kinematics
during feeding are poorly understood. Tongue kinematics were recorded
during grape chewing by macaque primates using biplanar videoradiography.
Complex shape changes in the tongue during chewing are dominated by a
combination of flexion in the tongue’s sagittal planes and roll about its
long axis. As hypothesized for humans, in macaques during tongue
retraction the middle (molar region) of the tongue rolls to the chewing
(working) side simultaneous with sagittal flexion, while the tongue tip
flexes to the other (balancing) side. Twisting and flexion reach their
maxima early in the fast close phase of chewing cycles, positioning the
food bolus between the approaching teeth prior to the power stroke.
Although 3D tongue kinematics undoubtedly vary with food type, the
mechanical role of this movement—placing the food bolus on the post-canine
teeth for breakdown—is likely to be a powerful constraint on tongue
kinematics during this phase of the chewing cycle. The muscular drivers of
these movements are likely to include a combination of intrinsic and
extrinsic tongue muscles.