Food, Form and Function: Motor Control, Movement and Modulation during Mastication in Mammals
Authors: Williams Susan H. 
Published: June 2021

Mammalian feeding is one of the many dynamic behaviors in which close form‐function relationships are readily apparent across the phylogeny. The link between masticatory morphology and function, for example, has been highlighted time and again with classic contrasts being made between major dietary groups, such as herbivores and carnivores. These contrasts emphasize differences between the teeth, muscle anatomy, temporomandibular joint (TMJ) and masticatory kinematics. In some cases, masticatory anatomy is hypothesized to significantly limit movement. Yet it has also been shown in diverse species that mastication is a behavior that has the potential for significant functional variability depending on a number of factors, including the textural, mechanical and/or physical properties of the food being consumed and jaw muscle activation patterns that move the jaw and produce the force to break down food. Here, I will explore the relationship between masticatory morphology, jaw‐muscle activity and jaw kinematics in select species representing different dietary groups (e.g., herbivory, carnivory, and omnivory) and examine the effect that food properties have on the dynamic response of the feeding system. Jaw‐muscle activity patterns were collected using electromyography and kinematic data were collected using X‐ray Reconstructing of Moving Morphology (XROMM). In goats (herbivore), increasing food toughness increases total cycle duration and the duration of jaw closing during chewing, whereas increasing food stiffness has little effect on overall temporal dynamics. Differences are observed in the jaw‐muscle firing patterns when chewing on different foods. Kinematic data from pigs (omnivore) reveal that changes in food toughness affect the chewing cycle as a whole, whereas changes in food stiffness alter the relative contribution and duration of the constituent phases of the chewing cycle, while total cycle duration remains more or less constant. Comparisons between ferrets (carnivore) and two closely related omnivorous species, skunks and raccoons in jaw kinematics, also indicate that the morphology of the TMJ and dentition may impact how jaw‐movements are modulated during mastication. Finally, kinematic data also reveal that occlusion is facilitated by rotation of the jaw about a vertical axis (“yaw”), mediolateral translation of the condyles, and/or rotation of the working‐side hemimandible around its long axis (“roll”), yet there are differences in the relative contribution of each type of movement that may be related to tooth and TMJ morphology. Combined, these experimental datasets from different species reveal new complexities to mastication and the modulation of jaw movements in mammals and help to clarify interpretations of function from morphology.Support or Funding InformationThis research was funded by National Science Foundation grants IOS‐0520855, IOS‐1456810 and DBI‐0922988.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.