Neuromechanical Control of Elastic Energy Storage and Recovery during Ballistic Movements

Northern Arizona University, Flagstaff AZ

Investigators

Abstract

Over the past 20 years, it has become increasingly clear that an understanding of biomechanics is necessary for understanding motor control. However, our knowledge of precisely how biomechanics influences the control of movement is still rudimentary. One obstacle to developing a deeper understanding of this problem is the sheer complexity of animal bodies. The number of muscles far exceeds the number of joints, and muscles may serve a variety of different functions in addition to their conventional roles as contractile and force-producing elements. The research proposed here uses ballistic tongue projection in toads as a model system to investigate the relationship between the biomechanics and neural control of movement. Ballistic tongue projection in toads is one of the fastest known movements, yet it shares many general features with typical vertebrate motor systems. Because it is relatively well understood, ballistic tongue projection in toads is a tractable model system for investigating the relationship between biomechanics and neural control. The fundamental idea of this proposal is to work backward from a predictive biomechanical model, toward an understanding of the design of the neural circuits that produce movement. The first goal of the proposed research is to develop a complete and predictive biomechanical model of elastic energy storage and recovery during ballistic tongue projection in toads. To complete the biomechanical modeling, the investigators will determine: (1) the force(s) that permit elastic energy storage, including co-activation of antagonistic muscles as well as passive mechanisms; and (2) the mechanical and neural events that permit recovery of elastic strain energy. The second goal of the proposed studies is to use present understanding of biomechanics to develop and test hypotheses about the design of the neural circuits that control ballistic tongue projection. Using neuroanatomical techniques, descriptions will be developed of the neural connections among proprioceptive sensory neurons, motor neurons, and the pre-motor neurons of the cerebellum and medial reticular formation that receive sensory input and control the activity of motor neurons. The proposed studies will provide insight into three important issues in the field of neuromechanics: (1) the contribution of antagonistic muscle contraction to motor control; (2) the structure of neural circuits for feed-forward control of movement, from sensory input to motor output; and (3) the neuroanatomical basis for muscle synergies. The broader impacts of this proposal include the collaboration of a multidisciplinary team, composed of a biomechanist, a behavioral neuroscientist, and a neuroanatomist. In addition, through support from the National Institute of General Medical Sciences (NIH), the proposed studies will provide opportunities for participation of underrepresented students, especially Hispanics and Native Americans.