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Patterns of variation across primates in jaw-muscle electromyography during mastication.

Publication ,  Journal Article
Vinyard, CJ; Wall, CE; Williams, SH; Hylander, WL
Published in: Integrative and comparative biology
August 2008

Biologists that study mammals continue to discuss the evolution of and functional variation in jaw-muscle activity during chewing. A major barrier to addressing these issues is collecting sufficient in vivo data to adequately capture neuromuscular variation in a clade. We combine data on jaw-muscle electromyography (EMG) collected during mastication from 14 species of primates and one of treeshrews to assess patterns of neuromuscular variation in primates. All data were collected and analyzed using the same methods. We examine the variance components for EMG parameters using a nested ANOVA design across successive hierarchical factors from chewing cycle through species for eight locations in the masseter and temporalis muscles. Variation in jaw-muscle EMGs was not distributed equally across hierarchical levels. The timing of peak EMG activity showed the largest variance components among chewing cycles. Relative levels of recruitment of jaw muscles showed the largest variance components among chewing sequences and cycles. We attribute variation among chewing cycles to (1) changes in food properties throughout the chewing sequence, (2) variation in bite location, and (3) the multiple ways jaw muscles can produce submaximal bite forces. We hypothesize that variation among chewing sequences is primarily related to variation in properties of food. The significant proportion of variation in EMGs potentially linked to food properties suggests that experimental biologists must pay close attention to foods given to research subjects in laboratory-based studies of feeding. The jaw muscles exhibit markedly different variance components among species suggesting that primate jaw muscles have evolved as distinct functional units. The balancing-side deep masseter (BDM) exhibits the most variation among species. This observation supports previous hypotheses linking variation in the timing and activation of the BDM to symphyseal fusion in anthropoid primates and in strepsirrhines with robust symphyses. The working-side anterior temporalis shows a contrasting pattern with little variation in timing and relative activation across primates. The consistent recruitment of this muscle suggests that primates have maintained their ability to produce vertical jaw movements and force in contrast to the evolutionary changes in transverse occlusal forces driven by the varying patterns of activation in the BDM.

Duke Scholars

Published In

Integrative and comparative biology

DOI

EISSN

1557-7023

ISSN

1540-7063

Publication Date

August 2008

Volume

48

Issue

2

Start / End Page

294 / 311

Related Subject Headings

  • Evolutionary Biology
  • 3109 Zoology
  • 3104 Evolutionary biology
  • 3103 Ecology
  • 0608 Zoology
  • 0602 Ecology
  • 0601 Biochemistry and Cell Biology
 

Citation

APA
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ICMJE
MLA
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Vinyard, C. J., Wall, C. E., Williams, S. H., & Hylander, W. L. (2008). Patterns of variation across primates in jaw-muscle electromyography during mastication. Integrative and Comparative Biology, 48(2), 294–311. https://doi.org/10.1093/icb/icn071
Vinyard, Christopher J., Christine E. Wall, Susan H. Williams, and William L. Hylander. “Patterns of variation across primates in jaw-muscle electromyography during mastication.Integrative and Comparative Biology 48, no. 2 (August 2008): 294–311. https://doi.org/10.1093/icb/icn071.
Vinyard CJ, Wall CE, Williams SH, Hylander WL. Patterns of variation across primates in jaw-muscle electromyography during mastication. Integrative and comparative biology. 2008 Aug;48(2):294–311.
Vinyard, Christopher J., et al. “Patterns of variation across primates in jaw-muscle electromyography during mastication.Integrative and Comparative Biology, vol. 48, no. 2, Aug. 2008, pp. 294–311. Epmc, doi:10.1093/icb/icn071.
Vinyard CJ, Wall CE, Williams SH, Hylander WL. Patterns of variation across primates in jaw-muscle electromyography during mastication. Integrative and comparative biology. 2008 Aug;48(2):294–311.
Journal cover image

Published In

Integrative and comparative biology

DOI

EISSN

1557-7023

ISSN

1540-7063

Publication Date

August 2008

Volume

48

Issue

2

Start / End Page

294 / 311

Related Subject Headings

  • Evolutionary Biology
  • 3109 Zoology
  • 3104 Evolutionary biology
  • 3103 Ecology
  • 0608 Zoology
  • 0602 Ecology
  • 0601 Biochemistry and Cell Biology