Mary W. Marzke - US grants

9987619
Ji-Ping He - Arizona State University
IGERT: Neural and Musculoskeletal Adaptation in Forms and Function

This Integrative Graduate Education and Research Training (IGERT) award supports the establishment of a multidisciplinary graduate training program of education and research on neural and musculoskeletal adaptation in form and function. This theme is examined with integrated approaches from bioengineering, neurophysiology, physical anthropology, exercise sciences, computer and system sciences. The goal of the program is to introduce students with diverse biological and engineering backgrounds to the challenges of deciphering complex phenomena in integrative and computational neuroscience, motor diorders and rehabilitation. The program will foster interdisciplinary education and training in research efforts toward meeting these challenges. Graduate training will expand upon two related areas in which participating faculty have developed research and teaching collaborations: (1) mechanisms underlying neural control of movements, emphasizing hand function and locomotion, and (2) evolutionary morphology of the human hand and bipedality. Three interdisciplinary courses built around core research laboratories (Biomechanics/Anatomy, Neurophysiology/Neuroengineering, and Computation/Visualization) will anchor the program. Research training will be enhanced by access to medical imaging resources and by basic and applied research projects in collaboration with leading medical institutions, biomedical enterprises and evolutionary research resources at the Institute of Human Origins. The program addresses the multidisciplinary needs of graduate education, creates a rich environment for generation of innovative ideas for leading edge research in neuroengineering, evolutionary morphology, motor control, stereo modeling and visualization.

IGERT is an NSF-wide program intended to meet the challenges of educating Ph.D. scientists and engineers with the multidisciplinary backgrounds 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 new, innovative models for graduate education and training in a fertile environment for collaborative research that transcends traditional disciplinary boundaries. In the third year of the program, awards are being made to nineteen institutions for programs that collectively span all areas of science and engineering supported by NSF. The intellectual foci of this specific award reside in the Directorates for Engineering; Biological Sciences; Social, Behavioral, and Economic Sciences; Computer and Information Science and Engineering; and Education and Human Resources.

Identifying skeletal features in the hands and wrists of early fossil hominid species (humans and their closest bipedal relatives) that may predict stone tool-making capabilities is of interest to anthropologists, because stone tools are found in fossil deposits where more than one hominid species has been recovered. Chimpanzees have traditionally been used as a model for early hominid hands because of their close genetic relationship to humans and their use of tools in the wild. Capuchin monkeys, less closely related to humans, rival chimpanzees in their tool-using abilities in captivity. Capuchins are unique among monkeys in that they frequently pound objects against trees in the wild. Pounding may be pre-adaptive for tool-making behaviors; therefore, capuchins may provide an alternative nonhuman primate model for identifying features in the fossil hands of early hominids that reflect stresses on the hand associated with pounding and forceful manipulation of stones.
The question addressed by this study is whether there are features of capuchin hand muscles and bones that reflect their distinctive manipulative behaviors. The answer will be approached as follows. First, relative cross-sectional areas of cadaver hand muscles will be compared in Cebus apella (tufted capuchin) and Saimiri sciureus (common squirrel monkey, a close relative of capuchins). Cross-sectional area reflects a muscle's potential to exert force and is estimated by measuring its volume and its fiber length. Second, relative leverage of these same muscles (i.e., their lever arms) will be estimated by passively moving each hand joint while simultaneously measuring (1) the joint's full range of motion and (2) the distance moved by the muscle tendon crossing the joint. These measurements will allow estimation of each muscle's potential to exert torque, i.e. the relative ability of each muscle to rotate a bone at a joint. Finally, skeletal features that reflect relative areas and lever arms of these muscles will be identified, described and measured, where possible. It is predicted that capuchins will have some hand muscles that are capable of generating relatively greater torques than in squirrel monkeys, and that these muscles will be associated with distinct skeletal features.
These data are essential to analysis of manipulative capabilities. They have not been previously obtained for either species. Once muscles with large torque potentials have been identified in the capuchins, these muscles can be tested in a future study using electromyography, to determine whether they are indeed strongly recruited during pounding behaviors.
Training in the techniques and interdisciplinary approach used in this study will be offered to other researchers at workshops, to undergraduate and graduate students at Arizona State University, and to high school students, including underrepresented groups, at open houses sponsored by the IGERT Neural & Musculoskeletal Adaptations in Form & Function program (NSF#9987619) at Arizona State University, to which both the PI and Co-PI are attached. Broad dissemination of the collected data, techniques, and interdisciplinary approach will allow for research collaborations worldwide to use the capuchin as an alternative nonhuman primate model in clinical research on hand function.

Reconstructing the form of locomotion that preceded the evolution of human bipedality is a key goal of paleoanthropology. Knuckle-walking (a semi-terrestrial form of locomotion in which weight is borne on the backs of the middle hand phalanges) is a plausible candidate because it is practiced by the African apes, which are humans' closest living relatives. However, arguments for a knuckle-walking ancestor for the human evolutionary lineage rely on accurate interpretations of certain anatomical features in chimpanzees, gorillas, and early hominins (fossil species more closely related to humans than chimpanzees) as adaptations to knuckle-walking. The proposed project, to be conducted by Caley Orr under the direction of Dr. Mary Marzke and Dr. Mark Spencer at Arizona State University, will test the hypothesis of adaptation to knuckle-walking for such features using the comparative method. The interdisciplinary project will proceed by integrating innovative techniques from the fields of anthropology, computer science, and bioengineering. Wrist joint shape in anthropoid primates will be quantified from laser scan-derived three-dimensional digital models. In addition, the three-dimensional movements of the wrist bones will be analyzed using serial computed tomography scanning of primate cadavers to test specific hypotheses about the functional consequences of differences in joint shape between species. The knuckle-walking African apes will be compared with the digitigrade baboons, which also use a "vertical manus" form of locomotion, during which the palm is held vertically when placed onto the substrate. These species will be contrasted with several primates capable of using extended-wrist palmigrade hand positions during which the palm is typically placed onto the substrate. Joint mechanisms shared exclusively by the African apes and baboons will be supported as adaptations to maintaining vertical manus postures, and these features can be used to infer such hand postures in fossil species.

The scientific merit of this study is that its novel integrative and quantitative approach facilitates the identification of features adapted to vertical manus postures. The appearance of these features in early hominins would support the hypothesis of a knuckle-walking ancestor. If a knuckle-walking phase in human evolution were to be demonstrated, it would limit adaptive explanations for the origins of bipedality to those consistent with a semi-terrestrial ancestor.

Broader impacts of the project are its value for education of students at all levels and its clinical as well as academic applications. First, the 3D laser-scan models and developed analytical software will be shared via an online database to facilitate further research. The data and software will be useful for researchers and educators in anthropology, paleontology, anatomy, and biomedical fields such as orthopedics. Second, the project will provide a research experience for an undergraduate student who will assist with data processing and analysis. Finally, the project will provide an interdisciplinary training opportunity for Caley Orr in techniques from anthropology, anatomy, bioengineering, and computer visualization that will facilitate his future research and enhance his teaching at the university level.