Internal kinematics of the tongue during feeding in pigs.

Six ultrasonic crystals (Ø2 mm) were implanted into the tongue body to form a wedge-shaped configuration in six 12-week-old Yucatan minipigs. These crystals allow recording of the distance changes in bilateral lengths (RL/LL) and base thicknesses (RT/LT), and anterior (AW) and posterior (dorsal and ventral, PDW and PVW) widths during natural feeding. Results indicated that changes in all measured dimensions were stereotypical with considerable regularity. The greatest dimensional changes during chewing were seen in the AW (33.3%), significantly larger than those in other dimensions (P < 0.05-0.001). During ingestion, change in all widths and thicknesses reduced significantly compared with those during chewing (P < 0.05), but changes in the lengths (RL/LL) were significantly larger than those during chewing (P < 0.01). During drinking, overall dimensional changes reduced and amplitudes were symmetrically distributed in all dimensions. The timing analysis indicated that, during chewing, the reversal of dimensional decrease to increase in the PVW occurred first, followed by those of PDW, AW, RT/LT, and RL/LL (P < 0.05). During ingestion, the AW started widening first. Time sequence of these reversals during drinking was similar to that during chewing, but RT/LT thickening was behind RL/LL lengthening. These results suggested that during natural feeding, regional tongue deformations are rhythmic and stereotypical similar to jaw movement. The reversals of expansion-contraction of various dimensions are not synchronous, but occur in a sequential manner in timing. Tongue internal deformations are task-specific in both timing and amplitude. The dimensional expansions-contractions are dominant in the transverse and sagittal planes during chewing and ingestion, respectively, but are smaller and more symmetrically distributed across various dimensions during drinking. (c) 2007 Wiley-Liss, Inc.