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Session Schedule & Abstracts

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Sunday 3rd July, 2016

Feeding 4

Room: Salon C   2:30 pm–3:45 pm

Moderator(s): Marcé-Nogué J, Pineda-Munoz S
FED4-1  2:30 pm  Hierarchical variation in EMG signal in oral vs. pharyngeal muscles. German RZ*, NEOMED; Gould F. DH, NEOMED; Ohlemacher JA , NEOMED; Vinyard CJ, NEOMED
Abstract: Variation in EMG signals of the oropharyngeal muscles can be partitioned into hierarchical components ranging from the cycle, through sequence, experiment (e.g., day), individual and species. By integrating data on mammalian oropharyngeal muscles from the FEED database, it is possible to compare the relative significance of different components of variation among anatomical groups of muscles. In particular, there are significant differences in function and evolutionary history among (1) the muscles of the oral floor/suprahyoid muscles; (2) the muscles of mastication; and (3) the infrahyoid muscles. We measured both the time of peak activity and the relative amplitude at peak activity for multiple muscles in each of these anatomical groups for various mammalian species. Among the pharyngeal muscles, the suprahyoid muscles were more variable than the infrahyoid muscles. The pharyngeal muscles demonstrated the most variation among individuals and then within a given muscle (duplicate electrodes). For the muscles of mastication, the cycle accounted for the largest portion of the variation in peak timing followed by sequence or species depending on the muscle. Variation in peak activity was accounted for primarily by variation at the level of the cycle and sequence. While the pharyngeal and masticatory muscle datasets vary in species and ontogenetic stage, the comparison of variance components among these anatomical muscle groups suggest future testable hypotheses relating to oropharyngeal muscle function, feeding plasticity, and performance across mammals. Supported by NIH:DC9980, NSF:DBI – 1062332, NSF:BCS-0552285.

FED4-2  2:45 pm  The relationship between kinematics and performance in mammalian swallowing. Ohlemacher J*, Northeast Ohio Medical University; Gould F, Northeast Ohio Medical University; German R, Northeast Ohio Medical University
Abstract: An organism’s performance is controlled by a hierarchy of mechanisms, from the CNS, through muscle activity, which produces kinematics. Here, we use mammalian swallowing to assess the relationship between kinematics and performance. Swallow performance falls into discrete categories: swallows without error and those with corrected error. We tested the hypotheses that correcting performance errors was correlated with kinematics changes and that the variation would be higher in the corrected swallows. Infant pigs, with radio-opaque markers in the hard and soft palates, the tongue, the hyoid and the epiglottis, were recorded, via videofluroscopy at 100 fps, drinking milk. Swallows were scored using the Infant Mammalian Penetration Aspiration Scale (IMPAS). IMPAS = 1 are swallows without error and IMPAS = 2 are swallows with corrected errors. This study included three animals with both IMPAS 1 & 2 swallows, and 218 swallows. A repeated measures design in a mixed GLM model was used to test for differences among our measurements between the two performance scores. The duration of the swallow cycle was different between swallows IMPAS 1 and 2 (p<0.00). The range in movement of the posterior tongue, epiglottis, and hyoid were more variable in swallows IMPAS = 2 than swallows IMPAS = 1 (p<0.00). Despite differences in duration of the swallow cycle and differences in variation of the range of movement of structures directly implicated in the swallow, relative timing of movement, the movement and location of one structure relative to the others at the same time, was not different (p=0.11). For swallows with corrected errors, variation is increased in the duration of the swallow cycle and the range in movement of structures implicated in swallows compared to swallows without error. It is possible that these changes are due to the mechanisms employed in swallows where error is corrected, which informs us on how kinematic changes can lead to performance changes.

FED4-3  3:00 pm  Variation in tongue and bolus shape and its relationship to airway protection in infant mammals. Gould F.D.H.*, Northeast Ohio Medical University; Ohlemacher J., Northeast Ohio Medical University; German R.Z., Northeast Ohio Medical University
Abstract: Obligate liquid feeding using a lingual suction pump is a mammalian behavioral synapomorphy of infants. Owing to the anatomical relationships between the trachea and the esophagus, the path of the liquid bolus during the swallow crosses over the entrance to the airway. Thus, control of the movement dynamics of the liquid bolus as it is propelled from the oral cavity into the pharynx is crucial for maintaining airway protection. In this study we tested the hypothesis that, following sensory nerve lesion, changes in tongue shape and bolus shape prior to movement of the bolus from the oral cavity to the pharynx affect airway protection. Four infant pigs were trained to drink milk with barium. The right recurrent laryngeal nerve, which provides sensory supply to the lower trachea, was lesioned in each animal. Swallows were recorded using highspeed videofluroscopy, pre- and post-lesion, and subsequently assessed for airway protection. Bolus and tongue surface shape were digitized in the frame prior to onset of movement of the bolus across the airway. Bolus shape was analyzed using elliptical Fourier analysis and principal components, and tongue surface shape analyzed with second order polynomial fitting. Although bolus shape and tongue shape varied significantly among individuals, within individuals, consistent, statistically significant patterns of change in bolus shape and in tongue shape exist both pre- and post- lesion, and between swallows with and without adequate airway protection. Variation in bolus dynamics and tongue behaviors is hierarchically partitioned. Within individuals, tongue control is key to bolus control, and safe swallow. A better understanding of the kinematics of the muscular tongue is needed to understand how infant mammals protect the airway while swallowing milk. This work was supported by NIH R01 009980.

FED4-4  3:15 pm  Dental morphology, diet and the dynamics of morphological evolution across marsupials and placentals. Pineda-Munoz S.*, NMNH Smithsonian Institution; Alroy J., Macquarie University; Evans A.R., Monash University
Abstract: Dietary inferences are a key foundation for paleoecological, ecomorphological and macroevolutionary studies because they inform us about the direct relationships between the components of an ecosystem. Our goal was to design a quantitative phylogeny-free method to infer the typical diet of a species that could be also applied to macroevolutionary questions. Thus, we designed a multidimensional approach called Multi-Proxy Dental Morphology Analysis (MPDMA), which captures the variability of diet and dietary morphospaces. Marsupials and placentals have experienced extraordinary adaptive radiations since their divergence in the Late Jurassic. Thus, they provide a unique opportunity to quantitatively both to test the power of MPDMA and to show whether diet specialization drives the evolution of dental morphology towards functional optima. We three-dimensionally scanned 32 marsupial and 115 placental species and qualitatively classified their diets. Orientation patch count (OPCR), slope diversity and the relief index were calculated from the dental 3D scans, and multivariate statistical analyses were used to test for discriminatory power. MPDMA demonstrates significant morphological differences across diets (P < 0.05) in a dataset including all species and in separate datasets including all individual orders save rodents (P = 0.321). Additionally, it correctly discriminates diet for 66 to 82% of the specimens in the dataset, including and excluding rodents respectively. Here, we quantitatively show for the first time how marsupials and placentals with the same dietary specializations overlap strongly in ecomorphospace, which suggests convergent phenotypic evolution in these two clades. Additionally, MPDMA highlights evolutionary changes within a given phylogeny. The coverage as well as movement across the plots of species belonging to different paleocommunities illustrates processes of diversification and ecomorphological evolutionary patterns such as niche competition.

FED4-5  3:30 pm  Primate chewing biomechanics revisited using Finite Element Analysis of the mandible. Marcé-Nogué J*, Centrum für Naturkunde, University of Hamburg, Hamburg, Germany; de Esteban-Trivigno S, Institut Català de Paleontologia, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain; González P, Instituto de Genética Veterinaria ; Kaiser TM, Centrum für Naturkunde, University of Hamburg, Hamburg, Germany
Abstract: Both biomechanics and teeth characteristics (morphology and wear) have been shown to be crucial to understand diet and evolution in primates. However, the relationship between these two types of data still remains unknown. In this work, biomechanics of the primate jaw were analysed using a classical two-dimensional lever approach together with a Finite Element Model. The aim was to analyse if there is a correlation between some biomechanical indicators of the jaw—such as bite force, mechanical advantage, von Mises Stress, etc.—and geometrical and physical properties of the teeth such as radius, enamel thickness, failure loads of the teeth, etc. If this correlation exists, that would allow researchers to predict the biomechanical behaviour of other taxa—especially extinct taxa—from physical characteristics of the teeth. Classical biomechanics were used to estimate muscular and biting forces as a load response in the models whereas FEA generated stress distribution patterns from the models. Recent procedures to compare quantitative FEA results from different models were used combining the Stress distribution maps and the values for the whole model. That includes exploratory methods such as box-plots and Principal Component Analysis. Phylogenetic signal was tested by means of Bloomberg’s K. The physical properties of the teeth (enamel thickness or failure loads) were obtained from the literature. As a whole they suggest that there is a relationship between some biomechanical parameters with enamel thickness and tooth radius as well as with the critical loads of tooth failure. The use of exploratory methods on the biomechanical variables helped to understand the oral behaviour of the primates, as well as the biomechanical performance.

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