Many researchers have posited that mammalian motor patterns are conserved during mastication (Hiiemae 1978; Bramble and Wake 1985; Weijs 1994). While Weijs (1994) was not the first researcher to recognize that transverse jaw movement during jaw closing is produced by asymmetric activation of the superficial masseter, medial pterygoid, and posterior temporalis (Herring 1973 1976 1979; Gorniak 1977 1985; Weijs and Dantuma 1980), he did reify the triplet motor pattern into an ancestral motor pattern modified by natural selection to produce the range of motor patterns observed in extant mammals. However there is little evidence to suggest that masticatory motor patterns are homologous. Computational studies of a variety of tasks suggest that movement primitives (simple spatiotemporal elements or building blocks) of behaviors, such as mastication, may represent local optima emerging from a learning process, whereby functional criteria are applied to a range of possible ways of moving until a local functional optimum is reached (Flash and Hogan 1985). The present study begins to determine why some motor patterns are more common than others from both a biomechanical perspective and a neural one. The overarching goal was to facilitate information transfer between the fields of biomechanics, neuroscience, and dynamical systems. Specific aim I determined the extent to which the triplet motor pattern is conserved during mastication. Specific aim II determined whether the CNS views the triplet motor pattern as a unit of control. It suggests concise and quantifiable definitions for unison, synchrony, and coordination to facilitate the flow of info between the fields of neuroscience, biomechanics, and dynamical systems. Specific aim III determined how functional groups of muscles are organized within the cortex.




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