My students and I are engaged in studies of the vertebrate neuromuscular and musculoskeletal systems with an emphasis on function and evolution. We examine limb kinematics, muscle design and spinal cord organization using a variety of techniques including high-speed photography and electromyography. The particular focus of this study is functional analysis of the Avian shoulder. The project is designed to yield basic morphological and physiological data requisite for the eventual modeling and testing of the neural control of wing movements in birds. Evidence exists from studies of muscle is ordered according to specific synaptic properties of the motoneuron which relate to size. Theoretical considerations, however, have resulted in alternative hypotheses for the ordering of motor unit within birds. To help clarify this important issue, we are studying the physiological profiles of isolated flight muscle motor units as well as their peripheral and central anatomical organization in two species with contrasting flight styles. This study is designed to address fundamental questions concerning the evolution of neuromuscular organization across the major vertebrate groups. Studies of birds will also provide data useful for evaluating current interpretations (based primarily on studies of the fossil bird Archaeopteryx) of the evolutionary origin of wings from the shoulder of early Mesozoic terrestrial archosaurs. Until we fully understand the musculoskeletal and neuromuscular basis of flight in a extant species, our understanding of the fundamental issue of the evolution of flight among tetrapods will be hampered.
