Mandibular symphyseal fusion in fossil primates: Insights from correlated patterns of jaw shape and masticatory function in living primates.
fusion; mandible; PRIMATES; geometric morphometrics; symphysis; ELECTROMYOGRAPHY; LEMURS; MANDIBLE; MORPHOMETRICS
Objectives: Variation in primate masticatory form and function has been extensively researched through both morphological and experimental studies. As a result, symphyseal fusion in different primate clades has been linked to either the recruitment of vertically directed balancing‐side muscle force, the timing and recruitment of transversely directed forces, or both. This study investigates the relationship between jaw muscle activity patterns and morphology in extant primates to make inferences about masticatory function in extinct primates, with implications for understanding the evolution of symphyseal fusion. Materials and methods: Three‐dimensional mandibular landmark data were collected for 31 extant primates and nine fossil anthropoids and subfossil lemur species. Published electromyography (EMG) data were available for nine of the extant primate species. Partial least squares analysis and phylogenetic partial least squares analysis were used to identify relationships between EMG and jaw shape data and evaluate variation in jaw morphology. Results: Primates with partial and complete symphyseal fusion exhibit shape‐function patterns associated with the wishboning motor pattern and loading regime, in contrast to shape‐function patterns of primates with unfused jaws. All fossil primates examined (except Apidium) exhibit jaw morphologies suggestive of the wishboning motor pattern demonstrated in living anthropoids and indriids. Discussion Partial fusion in Catopithecus, similar to indriids and some subfossil lemurs, may be sufficient to resist, or transfer, some amounts of transversely directed balancing‐side muscle force at the symphysis, representing a transition to greater reliance on transverse jaw movement during mastication. Furthermore, possible functional convergences in physiological patterns during chewing (i.e., Archaeolemur) are identified. [ABSTRACT FROM AUTHOR]
Knigge RP;Vinyard CJ;McNulty KP
American Journal Of Physical Anthropology
2020
2020-10
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
journalArticle
<a href="http://doi.org/10.1002/ajpa.24048" target="_blank" rel="noreferrer noopener">10.1002/ajpa.24048</a>
Adaptation Of Oral Processing To The Fracture Properties Of Soft Solids
bolus size; chewing behavior; elastic model foods; electromyography; electromyography; Food Science & Technology; fracture properties; gel texture; gels; hardness; human mastication; jaw movement; jaw tracking; muscle-activity; oral; processing; rheology; sensory; texture
Hardness and rubberiness are distinct textural properties that are associated with extended oral processing times and therefore of interest to designing food structure for specific textural properties. Model food gels were developed with (1) increasing strength/hardness and constant deformability or (2) increasing deformability/rubberiness within a limited range of strength. Gel structures were characterized based on mechanical properties and the muscle activity (electromyography) and mandibular movements (three-dimensional jaw tracking) required for oral processing. Increased strength or deformability required more chewing cycles and increased muscle activity to breakdown samples for swallowing. In contrast, jaw movement amplitude increased in all directions with increased strength and remained constant or decreased with increased deformability. Specific mechanical properties that were correlated with oral processing parameters changed as chewing progressed, possibly reflecting a change in dominate mechanical properties and sensory perception during oral processing. Practical ApplicationsA fundamental understanding of how food structure determines sensory texture is essential to designing foods that are healthy and desirable to consumers. Oral processing, from first bite through swallowing, is the main physiological element of texture evaluation. Model soft solid foods with increasing strength/hardness or deformability/rubberiness were developed and characterized by mechanical tests and oral processing. Mastication of harder or more deformable structures required different chewing movements in bolus preparation. The specific mechanical properties relating to oral processing may change during the chewing sequence.
Koc H; Cakir E; Vinyard C J; Essick G; Daubert C R; Drake M A; Osborne J; Foegeding E A
Journal of Texture Studies
2014
2014-02
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1111/jtxs.12051" target="_blank" rel="noreferrer noopener">10.1111/jtxs.12051</a>
Ternporalis Function In Anthropoids And Strepsirrhines: An Emg Study
adductor muscle force; Anthropology; biomechanics; electromyography; Evolutionary Biology; fusion; galago crassicaudatus; invivo bone strain; jaw-adductor muscle force; macaca-fascicularis; mandibular symphysis; masseter force; mastication; patterns; postorbital septum; primates; temporalis
The major purpose of this study is to analyze anterior and posterior temporalis muscle force recruitment and firing patterns in various anthropoid and strepsirrhine primates. There are two specific goals for this project. First, we test the hypothesis that in addition to transversely directed muscle force, the evolution of symphyseal fusion in primates may also be linked to vertically directed balancing-side muscle force during chewing (Hylander et al. [2000] Am. J. Phys. Anthropol. 112:469-492). Second, we test the hypothesis of whether strepsirrhines retain the hypothesized primitive mammalian condition for the firing of the anterior temporalis, whereas anthropoids have the derived condition (Weijs [1994] Biomechanics of Feeding in Vertebrates; Berlin: Springer-Verlag, p. 282-320). Electromyographic (EMG) activities of the left and right anterior and posterior temporalis muscles were recorded and analyzed in baboons, macaques, owl monkeys, thick-tailed galagos, and ring-tailed lemurs. In addition, as we used the working-side superficial masseter as a reference muscle, we also recorded and analyzed EMG activity of the left and right superficial masseter in these primates. The data for the anterior temporalis provided no support for the hypothesis that symphyseal fusion in primates is linked to vertically directed jaw muscle forces during mastication. Thus, symphyseal fusion in primates is most likely mainly linked to the timing and recruitment of transversely directed forces from the balancing-side deep masseter (Hylander et al. [2000] Am. J. Phys. Anthropol. 112:469-492). In addition, our data demonstrate that the firing patterns for the working- and balancing-side anterior temporalis muscles are near identical in both strepsirrhines and anthropoids. Their working- and balancing-side anterior temporalis muscles fire asynchronously and reach peak activity during the power stroke. Similarly, their working- and balancing-side posterior temporalis muscles also fire asynchronously and reach peak activity during the power stroke. Compared to these strepsirrhines, however, the balancing-side posterior temporalis of anthropoids appears to have a relatively delayed firing pattern. Moreover, based on their smaller W/B ratios, anthropoids demonstrate a relative increase in muscle-force recruitment of the balancing-side posterior temporalis. This in turn suggests that anthropoids may emphasize the duration and magnitude of the power stroke during mastication. This hypothesis, however, requires additional testing. Furthermore, during the latter portion of the power stroke, the late activity of the balancing-side posterior temporalis of anthropoids apparently assists the balancing-side deep masseter in driving the working-side molars through the terminal portion of occlusion.
Hylander W L; Wall C E; Vinyard C J; Ross C; Ravosa M R; Williams S H; Johnson K R
American Journal of Physical Anthropology
2005
2005-09
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1002/ajpa.20058" target="_blank" rel="noreferrer noopener">10.1002/ajpa.20058</a>
Functional And Evolutionary Significance Of The Recruitment And Firing Patterns Of The Jaw Adductors During Chewing In Verreaux's Sifaka (propithecus Verreauxi)
Anthropology; biomechanics; bone-strain; electromyography; Evolutionary Biology; Force; fusion; lemurs lemur-catta; macaca-fascicularis; mandibular symphysis; masseter force; mastication; muscle; primates; strepsirrhines; wishboning
Jaw-muscle electromyographic (EMG) patterns indicate that compared with thick-tailed galagos and ring-tailed lemurs, anthropoids recruit more relative EMG from their balancing-side deep masseter, and that this muscle peaks late in the power stroke. These recruitment and firing patterns in anthropoids are thought to cause the mandibular symphysis to wishbone (lateral transverse bending), resulting in relatively high symphyseal stresses. We test the hypothesis that living strepsirrhines with robust, partially fused symphyses have muscle recruitment and firing patterns more similar to anthropoids, unlike those strepsirrhines with highly mobile unfused symphyses. Electromyographic (EMG) activity of the superficial and deep masseter, anterior and posterior temporalis, and medial pterygoid muscles were recorded in four dentally adult Verreaux's sifakas (Propithecus verreauxi). As predicted, we find that sifaka motor patterns are more similar to anthropoids. For example, among sifakas, recruitment levels of the balancing-side (b-s) deep masseter are high, and the b-s deep masseter fires late during the power stroke. As adult sifakas often exhibit nearly complete symphyseal fusion, these data support the hypothesis that the evolution of symphyseal fusion in primates is functionally linked to wishboning. Furthermore, these data provide compelling evidence for the convergent evolution of the wishboning motor patterns in anthropoids and sifakas. Am J Phys Anthropol 145:531-547, 2011. (C) 2011 Wiley-Liss, Inc.
Hylander W L; Vinyard C J; Wall C E; Williams S H; Johnsonl K R
American Journal of Physical Anthropology
2011
2011-08
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1002/ajpa.21529" target="_blank" rel="noreferrer noopener">10.1002/ajpa.21529</a>
Interrelations among physical characteristics, sensory perception and oral processing of protein-based soft-solid structures
Fracture; Chemistry; Food Science & Technology; feeding-behavior; human mastication; chewing patterns; electromyography; periodontal mechanoreceptors; Physiology; Microstructure; Sensory perception; Texture; food texture; breakdown; elevator muscle-activity; Mixed gels; Oral processing
Oral processing is essential in breaking down the physicochemical structure of the food and thus important to the sensory perception of food in the mouth. To have an understanding of protein-based, soft-solid texture perception, a multidisciplinary approach was applied that combined studies of food microstructure with mechanical properties, sensory evaluation, and oral physiology. Model foods were developed by combining ion-induced micro-phase separation and protein-polysaccharide phase separation and inversion. Activities of masseter, anterior temporalis and anterior digastric muscles during oral processing were recorded by electromyography (EMG), while jaw movement amplitudes, durations, and velocities were simultaneously collected by a three-dimensional jaw tracking system (JT-3D). Changes in the microstructure of mixed gels significantly altered the characteristics of the chewing sequence, including the muscle activities, number of chews, chewing duration and chewing frequency. Mechanical attributes related to structural breakdown and sensory perception of firmness were highly correlated with the amount of muscle activity required to transform the initial structure into a bolus ready for swallowing. Chewing frequency was linked to mechanical properties such as recoverable energy, fracture strain and water holding capacity of the gels. Increased adhesiveness and moisture release also resulted in slower chewing frequency. Evaluation of oral processing parameters at various stages (i.e., first cycle, first 5 cycles, and last 3 cycles) was found to be a useful method to investigate the dynamic nature of sensory perception at first bite, during chewing and after swallowing. The study showed that muscle activity and jaw movement can be used to understand the links between physical properties of foods and sensory texture. (C) 2012 Elsevier Ltd. All rights reserved.
Cakir E; Vinyard C J; Essick G; Daubert C R; Drake M; Foegeding E A
Food Hydrocolloids
2012
2012-10
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1016/j.foodhyd.2012.02.006" target="_blank" rel="noreferrer noopener">10.1016/j.foodhyd.2012.02.006</a>
EVALUATION OF TEXTURE CHANGES DUE TO COMPOSITIONAL DIFFERENCES USING ORAL PROCESSING
model; Food Science & Technology; feeding-behavior; human mastication; electromyography; Texture; Caramel; cheddar cheese texture; cheese; cooked rice; fat reduction; food texture; foods; jaw movement; jaw tracking; muscle-activity; Oral processing; reduced-fat
Replacement of ingredients or reformulating existing products can significantly change textural characteristics. Our aim was to investigate the effects of sensory input from different textures on adaptation of the chewing pattern. Jaw muscle activity and kinematic measures of mastication were collected by electromyography and a three-dimensional jaw tracking system during chewing of Cheddar cheeses (varying fat content) and caramels (two levels of total fat and sweetened condensed milk). Reducing fat in cheese is associated with increased sensory firmness, springiness and decreased cohesiveness. Oral processing adjusted to decreased fat content with increased closing muscle (temporalis and masseter) activity, a shorter cycle duration and increased power stroke time. Increased adhesiveness in caramels was associated with increased closing and opening muscle activity, longer cycle duration and increased jaw movement. It was shown that changes in composition that produced changes in sensory texture change oral processing parameters of muscle activity and jaw movement. PRACTICAL APPLICATIONS Understanding the mechanisms of texture perception is essential when tailoring food to meet nutritional needs, while maintaining an acceptable level of quality. Textural characteristics change when ingredients are replaced or products are reformulated. In particular, the textures of low-fat or low-calorie products are perceived by consumers to be less pleasing compared with those of traditional foods. Understanding how oral processing is altered in response to changes in texture provides information on the physiology of texture perception that complements sensory analysis and mechanical tests. The aim of this study was to understand how the masticatory sequence adapts to textural variations in cheese and caramel of differing compositions. This information will enhance the understanding of the relationship between food structure and texture perception.
Cakir E; Koc H; Vinyard C J; Essick G; Daubert C R; Drake M; Foegeding E A
Journal of Texture Studies
2012
2012-08
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1111/j.1745-4603.2011.00335.x" target="_blank" rel="noreferrer noopener">10.1111/j.1745-4603.2011.00335.x</a>
Telemetry System for Assessing Jaw-Muscle Function in Free-ranging Primates
Alouatta; analysis; biomechanical; bone strain; electromyography; food properties; form; galago crassicaudatus; macaca-fascicularis; mandibular symphysis; mastication; morphology; old-world monkeys; telemetry; Zoology
In vivo laboratory-based studies describing jaw-muscle activity and mandibular bone strain during mastication provide the empirical basis for most evolutionary hypotheses linking primate masticatory apparatus form to diet. However, the laboratory data pose a potential problem for testing predictions of these hypotheses because estimates of masticatory function and performance recorded in the laboratory may lack the appropriate ecological context for understanding adaptation and evolution. For example, in laboratory studies researchers elicit rhythmic chewing using foods that may differ significantly from the diets of wild primates. Because the textural and mechanical properties of foods influence jaw-muscle activity and the resulting strains, chewing behaviors studied in the laboratory may not adequately reflect chewing behaviors of primates feeding in their natural habitats. To circumvent this limitation of laboratory-based studies of primate mastication, we developed a system for recording jaw-muscle electromyograms (EMGs) from free-ranging primates so that researchers can conduct studies of primate jaw-muscle function in vivo in the field. We used the system to record jaw-muscle EMGs from mantled howlers (Alouatta palliata) at Hacienda La Pacifica, Costa Rica. These are the first EMGs recorded from a noncaptive primate feeding in its natural habitat. Further refinements of the system will allow long-term EMG data collection so that researchers can correlate jaw-muscle function with food mechanical properties and behavioral observations. In addition to furthering understanding of primate feeding biology, our work will foster improved adaptive hypotheses explaining the evolution of primate jaw form.
Williams S; Vinyard C; Glander K; Deffenbaugh M; Teaford M; Thompson C
International Journal of Primatology
2008
2008-12
Journal Article
<a href="http://doi.org/10.1007/s10764-008-9292-3" target="_blank" rel="noreferrer noopener">10.1007/s10764-008-9292-3</a>
A Preliminary Analysis of Correlated Evolution in Mammalian Chewing Motor Patterns
alpacas; discrete characters; electromyography; emg; fusion; jaw movements; masseter; masticatory muscles; mechanics; morphology; symphyseal; Zoology
Descriptive and quantitative analyses of electromyograms (EMG) from the jaw adductors during feeding in mammals have demonstrated both similarities and differences among species in chewing motor patterns. These observations have led to a number of hypotheses of the evolution of motor patterns, the most comprehensive of which was proposed by Weijs in 1994. Since then, new data have been collected and additional hypotheses for the evolution of motor patterns have been proposed. Here, we take advantage of these new data and a well-resolved species-level phylogeny for mammals to test for the correlated evolution of specific components of mammalian chewing motor patterns. We focus on the evolution of the coordination of working-side (WS) and balancing-side (BS) jaw adductors (i.e., Weijs' Triplets I and II), the evolution of WS and BS muscle recruitment levels, and the evolution of asynchrony between pairs of muscles. We converted existing chewing EMG data into binary traits to incorporate as much data as possible and facilitate robust phylogenetic analyses. We then tested hypotheses of correlated evolution of these traits across our phylogeny using a maximum likelihood method and the Bayesian Markov Chain Monte Carlo method. Both sets of analyses yielded similar results highlighting the evolutionary changes that have occurred across mammals in chewing motor patterns. We find support for the correlated evolution of (1) Triplets I and II, (2) BS deep masseter asynchrony and Triplets I and II, (3) a relative delay in the activity of the BS deep masseter and a decrease in the ratio of WS to BS muscle recruitment levels, and (4) a relative delay in the activity of the BS deep masseter and a delay in the activity of the BS posterior temporalis. In contrast, changes in relative WS and BS activity levels across mammals are not correlated with Triplets I and II. Results from this work can be integrated with dietary and morphological data to better understand how feeding and the masticatory apparatus have evolved across mammals in the context of new masticatory demands.
Williams S H; Vinyard C J; Wall C E; Doherty A H; Crompton A W; Hylander W L
Integrative and Comparative Biology
2011
2011-08
Journal Article
<a href="http://doi.org/10.1093/icb/icr068" target="_blank" rel="noreferrer noopener">10.1093/icb/icr068</a>
Masticatory motor patterns in ungulates: A quantitative assessment of jaw-muscle coordination in goats, alpacas and horses
electromyography; emg; force; fusion; mandibular symphysis; masseter muscle; movements; pigs; Zoology
We investigated patterns of jaw-muscle coordination during rhythmic mastication in three species of ungulates displaying the marked transverse jaw movements typical of many large mammalian herbivores. In order to quantify consistent motor patterns during chewing, electromyograms were recorded from the superficial masseter, deep masseter, posterior temporalis and medial pterygoid muscles of goats, alpacas and horses. Timing differences between muscle pairs were evaluated in the context of an evolutionary model of jaw-muscle function. In this model, the closing and food reduction phases of mastication are primarily controlled by two distinct muscle groups, triplet I (balancing-side superficial masseter and medial pterygoid and working-side posterior temporalis) and triplet II (working-side superficial masseter and medial pterygoid and balancing-side posterior temporalis), and the asynchronous activity of the working- and balancing-side deep masseters. The three species differ in the extent to which the jaw muscles are coordinated as triplet I and triplet II. Alpacas, And to a lesser extent, goats, exhibit the triplet pattern whereas horses do not. In contrast, all three species show marked asynchrony of the working-side and balancing-side deep masseters, with jaw closing initiated by the working-side muscle and the balancing-side muscle firing much later during closing. However, goats differ from alpacas and horses in the timing of the balancing-side deep masseter relative to the triplet II muscles. This study highlights interspecific differences in the coordination of jaw muscles to influence transverse jaw movements and the production of bite force in herbivorous ungulates.
Williams S H; Vinyard C J; Wall C E; Hylander W L
Journal of Experimental Zoology Part a-Ecological Genetics and Physiology
2007
2007-04
Journal Article
<a href="http://doi.org/10.1002/jez.a.362" target="_blank" rel="noreferrer noopener">10.1002/jez.a.362</a>
Preference and consequences: A preliminary look at whether preference impacts oral processing in non-human primates
Anthropology; bitter taste; cebus-apella; chewing behavior; electromyography; Evolutionary Biology; fallback foods; Feeding; Food mechanical properties; Food preference; hardness; mastication; mechanical properties; model foods; muscle; patterns; texture
Non-human primates demonstrate food preferences much like humans. We have little insight, however, into how those preferences impact oral processing in primates. To begin describing this relationship, we conducted a preliminary analysis measuring food preference in two tufted capuchins (Cebus apella) and comparing ranked preference to physiological variables during chewing of these foods. Food preference was assessed for each monkey across 12 foods, including monkey biscuits and 11 foods consumed by humans (e.g., various fruits and nuts). Animals chose from randomized pairs of foods to generate a ranked scale across the 12 foods. Contemporaneous with preference testing, electromyographic (EMG) activity was measured for the jaw-closing muscles to assess oral physiology during chewing of these foods. As expected, these capuchins exhibited clear preferences among these 12 foods. Based on their preferences, we identified sets of preferred and non-preferred brittle (i.e., almond versus monkey chow) and ductile (i.e., dates and prunes versus apricots) foods for physiological comparisons that broadly control variation in food mechanical properties (FMPs). As expected, oral physiology varied with FMPs in each animal. Within brittle and ductile groupings, we observed several significant differences in chewing cycle length and relative muscle activation levels that are likely related to food preference. These differences tended to be complex and individual specific. The two capuchins chewed non-preferred apricots significantly faster than preferred dates and prunes. Effect sizes for preference were smaller than those for FMPs, supporting the previous focus on FMPs in primate dietary research. Although preliminary, these results suggest that food preference may influence oral physiology in non-human primates. The prospect that this relationship exists in monkeys raises the possibility that a link between food preference and oral processing in humans may be based on shared tendencies with non-human primates, such as aversion to bitter items or preference for sweet foods. (C) 2016 Elsevier Ltd. All rights reserved.
Vinyard C J; Thompson C L; Doherty A; Robl N
Journal of Human Evolution
2016
2016-09
Journal Article
<a href="http://doi.org/10.1016/j.jhevol.2016.07.001" target="_blank" rel="noreferrer noopener">10.1016/j.jhevol.2016.07.001</a>
Reflex sympathetic dystrophy after modified radical mastectomy: a case report.
Female; Humans; Middle Aged; Pain; Electromyography; Movement; *Postoperative Complications; Arm/physiopathology; Reflex Sympathetic Dystrophy/*etiology/physiopathology/therapy; *Mastectomy; Radical
Despite the long history of descriptions of reflex sympathetic dystrophy (RSD), much confusion remains regarding its pathogenesis, diagnosis, and treatment. It most commonly occurs after trauma and is more frequent in women, white persons, and the elderly. The first case of RSD after mastectomy is reported and the proposed pathophysiology and management of RSD are reviewed.
Saddison D K; Vanek V W
Surgery
1993
1993-07
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
Vagal afferents reflexly inhibit exercise in conscious rats.
Animals; Rats; Action Potentials/drug effects/physiology; Electromyography; Blood Pressure/drug effects/physiology; Physical Exertion/*physiology; Consciousness; Heart Rate/drug effects/physiology; Afferent Pathways/drug effects/physiology; Biguanides/administration & dosage/*pharmacology; Motor Activity/*drug effects/*physiology; Muscles/drug effects/physiology; Reflex/*drug effects/*physiology; Serotonin Receptor Agonists/administration & dosage/*pharmacology; Vagus Nerve/*drug effects/*physiology; Dose-Response Relationship; Drug; Sprague-Dawley
Activation of vagal afferents reflexly inhibited locomotion induced by stimulation of the mesencephalic locomotor region in decerebrate cats. However, this reflex has not been tested in intact mammals. Therefore, the purpose of this study was to test the hypothesis that vagal afferent stimulation would inhibit somatomotor activity in the intact conscious rat. Six Sprague-Dawley rats were chronically instrumented with carotid arterial and femoral venous catheters and electromyogram (EMG) electrodes inserted into the biceps femoris muscle. Cardiac autonomic efferent blockade [atropine methyl bromide (14 mg.kg-1, i.v.) and metoprolol (14 mg.kg-1, i.v.)] and alpha-adrenergic receptor blockade [phenoxybenzamine (5 mg.kg-1, i.v.)] was achieved to prevent bradycardia and hypotension. Vagal afferents were stimulated (phenyl-biguanide 2.5 and 5.0 micrograms.kg-1 i.v.) during steady state exercise (9.0 m.min-1, 10% grade). Phenyl-biguanide decreased exercise EMG activity 30 +/- 6% and 54 +/- 10% in a dose dependent manner without significantly altering mean arterial pressure or heart rate. We speculate that this reflex may serve as a negative feedback mechanism to indirectly reduce myocardial oxygen demands during exercise.
DiCarlo S E; Collins H L; Chen C Y
Medicine and science in sports and exercise
1994
1994-04
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1249/00005768-199404000-00010" target="_blank" rel="noreferrer noopener">10.1249/00005768-199404000-00010</a>
A preliminary analysis of correlations between chewing motor patterns and mandibular morphology across mammals.
*Mastication; Animals; Biological Evolution; Bite Force; Electromyography; Feeding Behavior/physiology; Jaw/anatomy & histology/*physiology; Mammals/anatomy & histology/physiology; Masseter Muscle/anatomy & histology/*physiology; Phylogeny; Temporal Muscle/anatomy & histology/*physiology
The establishment of a publicly-accessible repository of physiological data on feeding in mammals, the Feeding Experiments End-user Database (FEED), along with improvements in reconstruction of mammalian phylogeny, significantly improves our ability to address long-standing questions about the evolution of mammalian feeding. In this study, we use comparative phylogenetic methods to examine correlations between jaw robusticity and both the relative recruitment and the relative time of peak activity for the superficial masseter, deep masseter, and temporalis muscles across 19 mammalian species from six orders. We find little evidence for a relationship between jaw robusticity and electromyographic (EMG) activity for either the superficial masseter or temporalis muscles across mammals. We hypothesize that future analyses may identify significant associations between these physiological and morphological variables within subgroups of mammals that share similar diets, feeding behaviors, and/or phylogenetic histories. Alternatively, the relative peak recruitment and timing of the balancing-side (i.e., non-chewing-side) deep masseter muscle (BDM) is significantly negatively correlated with the relative area of the mandibular symphysis across our mammalian sample. This relationship exists despite BDM activity being associated with different loading regimes in the symphyses of primates compared to ungulates, suggesting a basic association between magnitude of symphyseal loads and symphyseal area among these mammals. Because our sample primarily represents mammals that use significant transverse movements during chewing, future research should address whether the correlations between BDM activity and symphyseal morphology characterize all mammals or should be restricted to this "transverse chewing" group. Finally, the significant correlations observed in this study suggest that physiological parameters are an integrated and evolving component of feeding across mammals.
Vinyard Christopher J; Williams Susan H; Wall Christine E; Doherty Alison H; Crompton Alfred W; Hylander William L
Integrative and comparative biology
2011
2011-08
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1093/icb/icr066" target="_blank" rel="noreferrer noopener">10.1093/icb/icr066</a>
A preliminary analysis of the relationship between jaw-muscle architecture and jaw-muscle electromyography during chewing across primates.
*Mastication; Animals; Electromyography; Jaw/*anatomy & histology/physiology; Masseter Muscle/*anatomy & histology/physiology; Primates/*anatomy & histology/physiology; Temporal Muscle/*anatomy & histology/physiology
The architectural arrangement of the fibers within a muscle has a significant impact on how a muscle functions. Recent work on primate jaw-muscle architecture demonstrates significant associations with dietary variation and feeding behaviors. In this study, the relationship between masseter and temporalis muscle architecture and jaw-muscle activity patterns is explored using Belanger's treeshrews and 11 primate species, including two genera of strepsirrhines (Lemur and Otolemur) and five genera of anthropoids (Aotus, Callithrix, Cebus, Macaca, and Papio). Jaw-muscle weights, fiber lengths, and physiologic cross-sectional areas (PCSA) were quantified for this preliminary analysis or collected from the literature and compared to published electromyographic recordings from these muscles. Results indicate that masseter architecture is unrelated to the superficial masseter working-side/balancing-side (W/B) ratio across primate species. Alternatively, relative temporalis architecture is correlated with temporalis W/B ratios across primates. Specifically, relative temporalis PCSA is inversely related to the W/B ratio for the anterior temporalis, indicating that as animals recruit a larger relative percentage of their balancing-side temporalis, they possess the ability to generate relatively larger amounts of force from these muscles. These findings support three broader conclusions. First, masseter muscle architecture may have experienced divergent evolution across different primate clades related to novel functional roles in different groups. Second, the temporalis may be functionally constrained (relative to the masseter) across primates in its functional role of creating vertical occlusal forces during chewing. Finally, the contrasting results for the masseter and temporalis suggest that the fiber architecture of these muscles has evolved as distinct functional units in primates.
Vinyard Christopher J; Taylor Andrea B
Anatomical record (Hoboken, N.J. : 2007)
2010
2010-04
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1002/ar.21121" target="_blank" rel="noreferrer noopener">10.1002/ar.21121</a>
Jaw-muscle electromyography during chewing in Belanger's treeshrews (Tupaia belangeri).
Animals; Biological; Biomechanical Phenomena; Electromyography; Mastication/*physiology; Masticatory Muscles/*physiology; Models; Muscle Contraction/*physiology; Phylogeny; Time Factors; Tupaia/*physiology
We examined masseter and temporalis recruitment and firing patterns during chewing in five male Belanger's treeshrews (Tupaia belangeri), using electromyography (EMG). During chewing, the working-side masseters tend to show almost three times more scaled EMG activity than the balancing-side masseters. Similarly, the working-side temporalis muscles have more than twice the scaled EMG activity of the balancing-side temporalis. The relatively higher activity in the working-side muscles suggests that treeshrews recruit less force from their balancing-side muscles during chewing. Most of the jaw-closing muscles in treeshrews can be sorted into an early-firing or late-firing group, based on occurrence of peak activity during the chewing cycle. Specifically, the first group of jaw-closing muscles to reach peak activity consists of the working-side anterior and posterior temporalis and the balancing-side superficial masseter. The balancing-side anterior and posterior temporalis and the working-side superficial masseter peak later in the power stroke. The working-side deep masseter peaks, on average, slightly before the working-side superficial masseter. The balancing-side deep masseter typically peaks early, at about the same time as the balancing-side superficial masseter. Thus, treeshrews are unlike nonhuman anthropoids that peak their working-side deep masseters early and their balancing-side deep masseters late in the power stroke. Because in anthropoids the late firing of the balancing-side deep masseter contributes to wishboning of the symphysis, the treeshrew EMG data suggest that treeshrews do not routinely wishbone their symphyses during chewing. Based on the treeshrew EMG data, we speculate that during chewing, primitive euprimates 1) recruited more force from the working-side jaw-closing muscles as compared to the balancing-side muscles, 2) fired an early group of jaw-closing muscles followed by a second group of muscles that peaked later in the power stroke, 3) did not fire their working-side deep masseter significantly earlier than their working-side superficial masseter, and 4) did not routinely fire their balancing-side deep masseter after the working-side superficial masseter.
Vinyard Christopher J; Williams Susan H; Wall Christine E; Johnson Kirk R; Hylander William L
American journal of physical anthropology
2005
2005-05
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1002/ajpa.20176" target="_blank" rel="noreferrer noopener">10.1002/ajpa.20176</a>