2001 — 2006 |
Ross, Callum |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
In Vivo Emg, Bone Strain and Cineradiography in Strepsirrhine Primates
The faces of primates exhibit a variety of shapes, particularly around the bony orbits, which house the eyes. It is not known whether this variety reflects differences in adaptations to feeding or adaptations to vision. Recent research has suggested that the bones around the orbit are strained very little during feeding, and a suite of "nonfeeding" explanations for the evolution of the primate orbital region have been proposed. It has also been suggested that the orbital region might be adapted for resisting feeding forces in some primates, but not in others. The research proposed here will determine whether there are differences between monkeys, apes and humans on one hand, and bushbabies on the other in the functioning of the orbital region during feeding. In contrast with the diversity in primate facial shape, primates seem to move their jaws in similar ways. This suggests that primates might have evolved their shape differences within the limits dictated by an ancient, conserved, behavior pattern shared with other mammals. This research will collect data on simultaneous jaw movements and muscle activity in several species of primates to determine whether changes in bony form really have proceeded without significant changes in the way primates move their jaws and fire their chewing muscles.
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0.915 |
2007 — 2012 |
Ross, Callum |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Collaborative Research: Integrative Analysis of Hominid Feeding Biomechanics
Understanding the forces that shaped the appearance and development of modern humans has been a leading goal of biological anthropology for decades. As technology has improved, our capability to investigate key questions about the factors affecting the shape of our anatomy have advanced significantly. Here, an interdisciplinary team of anthropologists and engineers will use engineering and experimental methods to examine how the shape of the skull has evolved in order to adapt to the forces associated with feeding on different types of food items. Specifically, the researchers will take a highly interdisciplinary approach to examining whether the skulls of these early humans were well designed to crack open and chew such hard, brittle objects. Dietary adaptations are thought to have been critical factors influencing the course of early human evolution, so this research project will provide valuable insights into the functional anatomy, diet, ecology and behavior of the earliest human ancestors.
With respect to intellectual merit, this project will: (a) examine the functional and evolutionary relationships between diet and skull form, (b) test a leading hypothesis explaining the evolution of the earliest humans, (c) collect and integrate multiple types of raw data critical to an understanding of feeding biomechanics, (d) develop methods for the rapid construction of engineering models that can be applied to research questions in a wide range of disciplines, (e) integrate ecological, comparative, experimental, and engineering techniques for the investigation of evolutionary questions, and (f) rapidly disseminate data, models and findings to the scientific community.
With respect to broader impacts, this study will: (a) promote interdisciplinarity, diversity and internationalism in science, (b) collect data about skull biomechanics that are relevant to dentistry and craniofacial medicine, (c) support the research of three junior investigators each in the first year of their academic appointments, (d) support female graduate students at several universities, (e) provide support to undergraduates at a university whose student body has a high proportion of minorities, (f) provide training for international students in developing nations (Brazil, Suriname), which will ultimately support the development of scientific infrastructure and institutions in those countries, (g) provide content to an exhibit focusing on human biology and evolution at the Georgia Children?s Museum, (h) using engineering models, limit the need for, or at least increase the analytical power of, future experimental studies requiring the use of live animals, (i) generate data relevant to conservation efforts by documenting the relationship between ecology and adaptation in certain primates, (j) strengthen collaborations between anthropologists and engineers in ten universities and two countries, (k) heighten awareness in the engineering community about how their methods are applicable to evolutionary questions.
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0.915 |
2009 — 2015 |
Shubin, Neil (co-PI) [⬀] Ross, Callum Hale, Melina [⬀] Hatsopoulos, Nicholas (co-PI) [⬀] Maciver, Malcolm |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Igert: Integrative Training in Motor Control and Movement
This Integrative Graduate Education and Research Traineeship (IGERT) project builds links broadly across Chicago's scientific community to develop an integrative training program for U.S. doctoral students in motor control and movement. To develop an integrative understanding of movement, it is necessary to address both the biology and the engineering of the systems involved and how they work together. Students from graduate programs at the University of Chicago and Northwestern University will obtain the biological and engineering backgrounds required to develop the integrative approach needed to take the field in new directions. Educational tools include a boot camp, a three-quarter common core curriculum, a discussion series, required laboratory rotations, and workshops and seminars at the Field Museum. The program will involve outreach to local Chicago-area schools, with training for students and faculty in the development and conduct of effective outreach. Mentoring of undergraduate students by IGERT graduate trainees will be done in close collaboration with local universities that primarily serve underrepresented minorities in the Chicago area. A trans-institutional website will highlight opportunities and results related to this program's IGERT goals and provide resources for teachers and students. IGERT is an NSF-wide program intended to meet the challenges of educating U.S. Ph.D. scientists and engineers with the interdisciplinary background, deep knowledge in a chosen discipline, and the technical, professional, and personal skills needed for the career demands of the future. The program is intended to catalyze a cultural change in graduate education by establishing innovative new models for graduate education and training in a fertile environment for collaborative research that transcends traditional disciplinary boundaries.
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0.915 |
2010 — 2013 |
Ross, Callum |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Collaborative Research: Integrative Analysis of the Scaling of Primate Feeding Systems
Feeding systems are the energy-acquiring systems of humans and other primates. The teeth, jaws, and muscles, are the proximal interface between primates and their environments. Therefore, understanding the evolutionary forces that shape those components is essential to understanding the adaptation and evolution of primates. This work tests hypotheses and models relating diversity in the primate feeding system to size-related changes in food intake rate. It documents how shape and movements of the mandible, the size and architecture of the jaw muscles, and the amount of food an animal eats in a single bite change with body size to meet size-required changes in food intake rate of primates. These data will be collected using computed tomography (CT) scanning of primate mandibles, anatomical studies of primate chewing muscles, and behavioral studies of primates feeding in captivity. Mathematical models of the feeding system will be tested, modified and improved, then used to examine how feeding system designs in different evolutionary groups of primates balance trade-offs between advantages of bite force production, chewing speed and gape.
This research will create novel and important data sets that can be accessed in the future by other researchers interested in feeding biomechanics, bone biomechanics, and musculoskeletal systems in general. The investigators will continue to recruit under-represented minority and female undergraduates to receive training and mentoring in research and advice on their paths to graduate, medical, and other professional schools. These students will collaborate in all aspects of the work, including presentation and publication. The PIs will continue their outreach programs to local schools and their synergistic activities with other NSF-funded projects.
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0.915 |
2010 — 2014 |
Shubin, Neil [⬀] Ross, Callum |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Collaborative Research: the Late Devonian Tetrapodomorph Tiktaalik Roseae
ABSTRACT
Project Title: Collaborative Research: The Late Devonian Tetrapodomorph Tiktaalik roseae
PI: Edward B. Daeschler, Associate Curator of Vertebrate Zoology, Academy of Natural Sciences of Philadelphia, 1900 Benjamin Franklin Parkway, Philadelphia, PA 19103
PI: Neil H. Shubin, Robert R. Bensley Distinguished Professor, Department of Organismal Biology and Anatomy, 1027 East 57th Street, University of Chicago, Chicago, IL 60637
Tiktaalik roseae is a fossil fish from the Late Devonian Period (385-362 million-years-ago) that was discovered in 2004 on Ellesmere Island, Nunavut, Canada. This species is the finned animal that is most closely related to tetrapods (limbed vertebrates). As an intermediate form, T. roseae helps us to recognize the sequence of morphological changes across the fish-to-tetrapod transition and can teach us about the forces that were driving these important evolutionary changes. T. roseae was first described in 2006 and has provoked a great deal of interest among evolutionary biologists. To date, however, the only published reports on this species have been short papers in Nature. With continued study and documentation of the abundant and well-preserved material of T. roseae, we will fill the need for a detailed investigation of this important fossil at the cusp of the fish-to-tetrapod transition.
A primary contribution of this research will be a detailed publication on a wide range of topics about T. roseae. The core of this publication will be a thorough morphological description including extensive figures of many of the 50+ specimens. We will also investigate the internal structure of bones in the fins for the first time, further document the ancient environment where T. roseae lived, and produce new studies of the evolutionary tree across the fish-to-tetrapod transition. The other major contribution of this project will take advantage of the quality of T. roseae fossils to assess the functional anatomy of the fins and skull. Evaluation of the hypothesis that the fins were capable of body support will involve detailed analysis of joint structure and the relative motions possible between bones, fin rays, and scales of the front fin and shoulder. The second set of analyses will explore the relationship between skull architecture and different stresses and strains in the skull related to movement, breathing and feeding. At the conclusion of this study, all T. roseae specimens are to be returned to the Government of Nunavut, and so the timely publication of these data via print and websites is of particular importance.
The discovery and description of T. roseae has received considerable attention from educational organizations and media internationally; as a textbook transitional fossil it has become a powerful tool in the communication of evolution to the general public. The PIs have a record of public lectures and development of web-based educational resources. We will make use of this research project to further communicate the results of the work, as well as the scientific process, to a broad audience and thereby help people get a better grasp of how evolution works.
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0.915 |
2013 — 2017 |
Margoliash, Daniel (co-PI) [⬀] Westneat, Mark (co-PI) [⬀] Ross, Callum Hale, Melina (co-PI) [⬀] |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Mri: Acquisition of Biplanar Digital Videofluoroscopy For X-Ray Reconstruction of Moving Morphology
An award is made to The University of Chicago to acquire and install a biplanar videofluoroscopy system that uses X-rays to measure 3-dimensional movements of the inside of animals through a method called X-ray Reconstruction of Moving Morphology (XROMM). XROMM generates 3D measurements and animations of biological movement by integrating 3D movement data collected using bi-planar digital videofluoroscopy with CT scan-based reconstructions of animal anatomy. XROMM makes it possible to measure movements of internal skeletal elements to which external markers cannot be attached without disrupting animal function, to study internal mechanics of small animals, such as mice, rats, and songbirds which are too small for external markers, to study animals that will only behave in optically opaque environment, such as in the dark, under soil, in water and/or in structurally complex environments, and to image internal soft tissue structures, such as muscles. The ability to make these measurements will enhance and expand research and training in integrative and evolutionary biomechanics, neuromechanics and neuroscience in the Chicago area. In particular, XROMM will enable innovations in the following areas: (1) Comparisons of locomotion and feeding movements of fish and amphibians in complex aquatic and terrestrial environments, and their relationship to evolutionary changes in form at the origin of tetrapods,(2) the diversity, complexity and control of 3D jaw and tongue movements during feeding in living mammals, and their relationship to changes in the structure of the feeding system during the origin and radiation of mammals, and (3) the role of the brain in control of 3D movements of a range of musculoskeletal organs, including jaws, tongues, eye muscles, and hands.
This research equipment will have multiple impacts beyond research, including teaching and training, public outreach and exhibit development, robotics and applied biomechanics. The XROMM instrumentation will provide postdoctoral researchers, graduate and undergraduate students with access to state-of-the-art research equipment in a dynamic intellectual environment that will make possible novel approaches to integrative analyses of animal movement. Graduate programs with access to XROMM will include: at the University of Chicago, the Graduate Program in Integrative Biology, the Committee on Evolutionary Biology, the Committee on Computational Neuroscience and the Committee on Medical Physics; at Northwestern University, the graduate programs in Biomedical Engineering, Physical Medicine & Rehabilitation, and Physiology; and the inter-institution, interdisciplinary NSF IGERT program, Integrative Training in Motor Control and Movement. Faculty and graduate students in these programs are actively involved in outreach locally (Sisters 4 Science; Global Village Science Project; Brain Day), and at national and international levels (Outreach programs in Fiji, New Guinea; Encyclopedia of Life Project; Biomechanics Exhibit, Field Museum of Natural History). The XROMM instrumentation will significantly augment these efforts by generating visually compelling animations of animal movement for presentation and online distribution. In making possible novel research into the role of the brain in control of movement, this equipment will contribute to understanding of motor control disorders including Parkinson's Disease and stroke.
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0.915 |
2014 — 2017 |
Ross, Callum |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Collaborative Research: Integrative Analysis of Ingestive Biomechanics and Dental Microwear in Evolutionary and Ecological Context
Modern humans exhibit small teeth, lightly built jaws and weak chewing muscles - anatomical features which have been shaped by evolutionary processes related to dietary intake and the processing of foods. The fossil record demonstrates that our morphology stands in contrast to that of our ancestors, who evolved to have large, strong teeth, massive jaws and powerful chewing muscles. Evolutionary explanations for this change include competing hypotheses as to how natural selection on diet drove adaptation over the course of human evolution. These hypotheses suggest that the presence or absence of either very hard or very tough foods may have been a critical factor influencing the evolution of our ancestors. Alternatively, the hardness or toughness of foods may have been less important than the behaviors (i.e., biting, puncturing, crushing, twisting, grinding) used to process foods of various shape and size with the jaws and teeth. This project will provide evidence to differentiate between these selective scenarios, thereby contributing to a fuller understanding of the evolutionary processes that have shaped this important aspect of modern human anatomy.
This research will require focus on a primate model, South American capuchins, which exhibit the relevant diversity in musculoskeletal anatomy and diet requisite to testing hypotheses regarding how food properties (i.e., hardness, toughness) or feeding behaviors influence the evolution of feeding adaptations. The study integrates observations of capuchin feeding behavior in the wild with laboratory experiments, advanced computer modeling using engineering methods, examination of the microscopic damage done to teeth by food and other items (i.e., dental microwear), the determination of the material properties (i.e., hardness, toughness) of food resources in the wild, and the collection and analysis of abrasive particles adhering to those foods (that might be influencing microwear patterns). Collectively, these data in capuchins will allow us to evaluate the assumptions underlying our interpretations of the interrelationships between dietary behavior, food resources, and the biology of our human ancestors, thereby transforming our understanding of human evolutionary history.
The broader impacts of this research are considerable. In relation to the public understanding of science, the research provides information that will address a topic of great public interest; namely, our own evolutionary history. As a related benefit, the project illustrates how ecological factors affecting other animals may be equally relevant and impactful for our own species. In terms of STEM training, research training opportunities are provided for high school students, undergraduates, graduate students, and postdoctoral fellows, many of whom are expected (based on past history at the collaborating institutions) to be young female scientists. The project also contributes to environmental awareness by collecting basic ecological data relevant to rainforest conservation. In the process of doing so, it further develops collaborative ties with international counterparts and institutions. Lastly, the project illustrates to the engineering community how their methods can be used to answer evolutionary questions.
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0.915 |
2014 — 2018 |
Ross, Callum F |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Neuroplasticity and the Role of Sensorimotor Cortex in Control of Orofacial Funct
DESCRIPTION (provided by applicant): Orofacial sensorimotor cortex (OSMcx)-orofacial primary motor cortex (MIo), primary somatosensory cortex (SIo), cortical masticatory area (CMAp)-dysfunction has been implicated in many orofacial sensorimotor disorders, including dysphagia, orofacial dystonia and dysarthria, spasmodic dysphonia, apraxia of speech, bruxism, chronic pain, and temporomandibular disorders. OSMcx displays neuroplasticity in association with acquisition of novel oral motor skills, intra-oral manipulations, and pain, and clinically targeting OSMcx has promise in treatment of orofacial disorders, such as dysphagia. The relationship between OSMcx neuroplasticity and learning of new oral skills is poorly understood, and the potential of OSMcx-targeted therapies for rehabilitation of speech, chewing, and swallowing disorders is barely explored. What roles do MIo, SIo, & CMAp independently and collectively play in control of natural feeding and trained orofacial motor tasks? How are neuroplastic changes in OSMcx orofacial motor and sensory representations related to changes in task performance? To address these questions, we will quantify neuroplasticity in OSMcx, and encoding of tongue and jaw kinematics and kinetics by recording simultaneously from MIo, SIo, & CMAp during natural feeding and learning of tongue protrusion or incisor biting tasks. We have 3 specific aims: Aim 1: to document the modulation of activity in neural ensembles in MIo, SIo, & CMAp during feeding, and performance of tongue protrusion or incisor-biting tasks before, during, and after long-term training to these tasks. Aim 2: to document simultaneously in MIo, SIo, & CMAp the encoding of jaw and tongue kinematics and kinetics in neural ensembles during feeding and during performance of tongue protrusion or incisor-biting tasks before, during, and after long-term training to these tasks. Aim 3: to document simultaneously in MIo, SIo, & CMAp the timing and nature of neuroplasticity associated with training in tongue protrusion or incisor biting tasks. The proposed research will provide novel insights into neuronal processes underlying OSMcx control of orofacial function and lay the groundwork for future studies of the rehabilitative potential of intensive task training and neuroplastic changes n OSMcx in recovery of orofacial function. These data will inform treatments of sensorimotor disorders that target OSMcx, such as those using stimulation or brain machine interfaces. The proposed research will leverage significant advances in neural recording, kinematic measurement, and data analysis that are being applied to studies of reach-to-grasp behaviors and, for the first time, apply them to addressing clinically significant problems in orofacial function.
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1 |
2015 — 2018 |
Ross, Callum |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Collaborative Research: Integrative Investigation of the Evolution and Biomechanics of Mandibular Form in Hominids
Among the fundamental questions about human origins is how our hominin ancestors lived. This study uses a multidisciplinary approach (paleontology, paleoecology, comparative anatomy, experimental biology) to ask questions about how extinct populations of hominins behaved on their natural landscapes. Specifically, the investigators will analyze lower jaws (mandibles), among the most commonly represented parts of the skeleton in the early human fossil record, of modern great apes and two early species of extinct hominins (Autralopithecus), to understand how the structure of the mandible is related to changes in feeding behavior and diet. The research will provide new data about how changes in diet and feeding behavior transformed our anatomy across time, permitting more robust explanations of the processes by which we became human. Broader impacts will include undergraduate, graduate and postdoctoral training in the latest analytical techniques for fossil analyses; outreach to primary and secondary school science teachers and students using hands-on experiences and web-based content designed to enhance teaching and learning about human origins; and the production of a unique collection 3D data for modern apes and rare fossil specimens that will be available to the scientific community.
Mandibles are the most common element in the hominin fossil record after teeth; they are used to diagnose species, test phylogenetic hypotheses, and infer feeding behavior and diet. However, extensive theoretical and experimental work on extant primates has not clarified which aspects of variation in mandibular form are related to variation in the positions of the tooth row, jaw muscles and jaw joint, which are related to the mandible's resistance to internal forces, and how these relate to feeding behavior and diet. Furthermore, the classical consensus on the relationship between dentognathic morphology and diet in Plio-Pleistocene hominins - adaptation to processing mechanically resistant foods - has been challenged by recent inferences from dietary isotopes, occlusal microwear, and finite element modeling, which do not converge on a shared view of early hominin diets and feeding behavior. This lack of consensus is especially glaring in light of the rich fossil record of mandibles for the Australopithecus anamensis-A. afarensis lineage (4.2-3.0 Ma), which documents clear changes in dentognathic morphology and carbon-isotope signatures over time. The primary focus of the proposed research is an integrative investigation of how spatial and mechanical determinants of mandibular form track change in diet and feeding behavior in extant hominids (great apes and humans) and early Australopithecus. The research is organized under three specific aims: 1. Quantifying and comparing the location, magnitude and nature of external and internal morphological variation in mandibles of extant (Homo, Pongo, Pan, and Gorilla) and fossil (A. anamensis, A. afarensis) hominids via computed tomography and geometric morphometrics; 2. Testing specific hypotheses about the biomechanical significance of variation in hominid mandibular morphology via finite-element models; and 3. Evaluating the extent to which spatial positioning of masticatory system components (tooth row, jaw joint, and muscle attachment points) explain variation in mandibular morphology across extant hominids and early Australopithecus. The project will provide new data on the structural and functional determinants of early hominin mandibular morphology, to help identify the factors that drove these morphological changes and allow tests of adaptive hypotheses about the early evolution of the genus.
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0.915 |
2016 — 2019 |
Kindlmann, Gordon Ross, Callum Runesha, Hakizumwami B. |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Mri: Acquisition of a Data Lifecycle Instrument (Dali) For Management and Sharing of Data From Instruments and Observations
Data from instruments and observations are being generated at increasing rates which leads to increased challenges in data management and computation. It is critical that we address these challenges because these large datasets enable massive breakthroughs across many scientific disciplines. Instruments and observations can generate terabytes of data per day, which often must be transferred from remote locations, field stations, or core facilities to the user's home system for storage and analysis. To address these challenges, The University of Chicago (UChicago) will acquire and operate a Data Lifecycle Instrument (DaLI) to manage and share data from instruments and observations at UChicago and the Marine Biological Laboratory (MBL). DaLI will simplify data management for researchers, allowing them to acquire, transfer, process, and share data from instruments and observations in a single workflow as well as share their data with a larger community of users. In partnership with UChicago, MBL, and collaborating Minority Serving Institutions, DaLI will be used as a training instrument to prepare students to meet the data challenges of the 21st century and will support several outreach programs.
The Data Lifecycle instrument (DaLI) for management and sharing of data from instruments and observations will enable researchers to (a) acquire, transfer, process, and store data from experiments and observations in a unified workflow, (b) manage data collections over their entire life cycle, and (c) share and publish data. DaLI will also (d) enhance outreach and education opportunities and (e) provide a replicable model for other institutions. DaLI will create a scalable, seamless, and replicable infrastructure for data management and sharing to enable new transformative science and enable researchers to implement best practices in data management. The DaLI platform will consist of four pools of resources: a high-performance compute resource for pre- and post-processing of data, a high-performance storage pool, a low cost storage pool, and a tape backup pool. In addition to hardware, DaLI is designed to have software tools that create intuitive interfaces for data lifecycle management and integration with the campus and national cyberinfrastructures.
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0.915 |
2017 — 2018 |
Ross, Callum Orsbon, Courtney (co-PI) [⬀] |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Doctoral Dissertation Research: Evolutionary Biomechanics of the Human Hyolingual Apparatus
The human tongue and hyoid bone have been extensively studied for their role in the evolution of speech. Some researchers hypothesize that our unique tongue and hyoid morphology also makes us more prone to choking. This research uses advanced imaging techniques and computational modeling to test whether human hyolingual morphology is beneficial or detrimental for swallowing. While this research focuses on swallowing function in an evolutionary context, the findings of this research will also advance our understanding of normal swallowing mechanisms and therefore may have clinical applications. The software for the computational model generated by this project will be made freely available upon completion. This project provides mentored research not only to a woman in science but specifically one studying biomechanics, a field in which women are underrepresented. Furthermore, the project will support undergraduate research and training for a diverse group of students at the University of Chicago.
The short faces and low tongue, hyoid, and larynx of humans have been argued to be adapted for speech and maladapted for swallowing. Recent studies cast doubt on both of these claims, prompting further exploration of alternative hypotheses to explain the origin of the uniquely human hyolingual apparatus. This project tests the hypothesis that hyolingual biomechanics constrain morphology, specifically that a low hyolingual apparatus is necessary to maintain swallowing performance as the face becomes shorter. X-ray Reconstruction of Moving Morphology (XROMM), diffusible iodine-based contrast-enhanced CT (diceCT), and electromyography (EMG) will be used to obtain high spatiotemporal resolution in vivo measurements of bone, tongue, and muscle biomechanics, including hyolingual muscle length, velocity, and activity in a primate model system. These data will then be used to validate a computational model of the impacts on swallowing biomechanics and performance of variation in hyolingual position, and craniofacial morphology. Falsification of the constraint hypothesis would provide indirect support for the hypothesis that the morphology of the human vocal tract is the result of natural selection for speech performance. This project will inform future research on how the functional requirements of the hyolingual apparatus may have influenced the morphology of surrounding structures, e.g., the mandibular symphysis, in both extant and extinct taxa.
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0.915 |
2019 — 2020 |
Hatsopoulos, Nicholas G [⬀] Ross, Callum F |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Coding of Action by Motor & Premotor Cortical Ensembles
Abstract The goal of this project is to understand how spatio-temporal patterns of activity across motor cortex initiate different types of voluntary movements. Large distributed ensembles of motor cortical neurons begin modulating their firing rates prior to voluntary movement and are thought to causally generate these movements. However, it is still unresolved why movement is not initiated when similar modulations in single unit motor cortical activity occur during movement planning, imagery, and visual observation of action. The amplitude of local field potential (LFP) oscillations in the beta frequency (15-40 Hz) range is known to attenuate prior to movement onset and is considered a mesoscopic signature of corticospinal excitability. We have recently discovered a sequential pattern of LFP beta attenuation and single unit modulation timing in primary motor cortex that is spatially organized prior to reaching movement onset but not during movement preparation. Our working hypothesis is that such a propagating sequential pattern is necessary to initiate movement. In this project, we will test and extend this hypothesis by demonstrating that such propagating patterns generalize to movement initiation of different behaviors including 2D reaching under different conditions, more complex 3D reach-to-grasp, and tongue protrusion and occur in premotor cortex. We will first demonstrate that propagating sequences in beta attenuation and single unit modulation timing occur during initiation of each of these behaviors along different portions of the somatotopic map of primary motor and premotor cortices. Second, we will provide a causal link between these propagating patterns and movement initiation by applying subthreshold, spatio-temporal patterns of electrical stimulation. We will demonstrate that movement initiation is delayed when patterned stimulation travels against the natural propagating sequence but not when it mimics the natural propagating pattern. Third, we will provide a mechanistic explanation of how these propagating sequences lead to muscle activation that supports movement initiation using patterned stimulus-triggered muscle activity and muscle decoding. To accomplish these aims, four high-density electrode arrays will be chronically implanted in the either the upper limb or orofacial areas of primary motor and premotor cortices from which 100s of single units and LFPs will be simultaneously recorded. A two-link exoskeletal robot and a motion tracking system using a set of fourteen infrared cameras will monitor the kinematics of the arm and hand. A strain gauge will measure tongue force and kinematics of the tongue will be tracked with a novel 3D x-ray fluoroscopy system. Indwelling EMG electrodes will also measure activity from arm, hand, and tongue muscles. A set of classical and novel computational methods will be employed to characterize the spatio-temporal dynamics of motor cortical activity during movement initiation.
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