Meeting Abstract

90.4  Thursday, Jan. 7  Kinematic analysis of chewing in primates: comparison of analytical methods on the analysis of jaw motion IRIARTE-DIAZ, J.*; ROSS, C.F.; University of Chicago; University of Chicago jiriarte@uchicago.edu

Chewing kinematics in mammals has been traditionally characterized and described by four phases: fast close (FC), slow close (SC), fast open (FO), and slow open (SO). These phases are based on the temporal profile of jaw vertical excursion or gape angle. Jaw motion, however, is essentially three-dimensional, where significant lateral displacements and rotations are necessary to effectively process food. As a consequence, traditional segmentation of the gape cycle based on unidimensional parameters might not completely reflect the complexity and subtleties of chew kinematics. Thus, to evaluate whether traditional chewing phases accurately describe the three-dimensional kinematic, we compared the timing of phases obtained by traditional methods to phases obtained by an alternative method based on the three-dimensional trajectories of jaw motion (“3D-phases”). We propose that a 3D phase can be characterized by the period where the jaw moves predominantly in a plane in space, with a substantial change in plane orientation from one phase to another. We recorded the three-dimensional kinematics of two macaque and three capuchin subjects. Preliminary analysis suggests the existence of four 3D-phases, roughly similar to the phases obtained by traditional methods, although the timing of these phases varied between methods. For example, the timing of the SC-SO transition was usually associated with a 3D-phase transition. In contrast, the differences in timing of both FC-SC and SO-FO transitions with respect to the 3D transitions showed higher variability, suggesting that lateral motions and/or rotations of the mandible might play an important role, probably associated to tongue manipulation and repositioning of food bolus within the oral cavity.