Douglas L. Altshuler, Ph.D. - US grants

[unreadable] DESCRIPTION (provided by applicant): My proposed research seeks to address specific gaps in our understanding of how nervous systems modulate transitions among complex motor behaviors. Specifically, although considerable information is available regarding the neuromuscular control of stereotyped movements such as walking or running, little is known about how the nervous system regulates muscles to change speed, alter direction, and maneuver, I will examine these questions using the flight behaviors of hummingbirds. Hummingbirds are particularly good organisms for studies of motor control because of their extreme design for precise locomotion and maneuvering as well as their ease of training to complex flight behaviors. The approach of this study is to conduct two sets of laboratory experiments that quantify muscle activity and performance. During free flight I will record the wing and body motions (kinematics) using high-speed videography and measure the muscle activity of the 17 flight muscles using electromyography (EMG). Having linked muscle activity to flight kinematics I will then measure muscle forces on detached muscles using work loops to quantify how muscle stimulation patterns correspond to power production. Linking detailed flight kinematics, in vivo EMG recordings, and in vitro work loop analysis will provide an integrated view of all of the important characteristics of the motor control of shifts in locomotor modes. Improved understanding of the neural control of the regulation of complex motor behaviors would have direct relevance to studies of human motor control diseases and motor control degeneration that accompanies ageing. [unreadable] [unreadable]

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

The ability of an animal to maneuver can determine its success at avoiding predators, catching food, and other fundamental behaviors that define the margin between life and death. Most research on the biomechanics of animal motion has concerned the initiation or maintenance of ballistic, brief, or steady state movements because these can be studied most readily in the laboratory. Maneuverability is therefore one of the most important but least understood aspects of animal locomotion. Previous research has progressed along two independent tracks: 1) Studies of animal morphology have explained how the size and shape of the body and the limbs influence the efficiency and dynamics of maneuvering. 2) Studies of neuromuscular physiology have revealed the mechanisms that animals use to power particular maneuvers. However, animals with the ability to generate substantial muscle power, such as those that hover or fly slowly, may be able to overcome efficiency costs imposed by suboptimal morphology to generate rapid but inefficient maneuvers. The proposed work will test the hypothesis that the limitations imposed by morphology are strongest when muscle power-generating capacity is low. Research will focus on the remarkable maneuvering flight of hummingbirds because these animals inhabit broad elevational ranges, which provide natural experiments for varying muscle power capacity. Experiments with Anna?s hummingbirds (Calypte anna) in California will determine the effects of elevation and the independent influences of mechanical and metabolic constraints on maneuvering performance. Measurements from the diverse Andean hummingbird fauna will allow for determination of how vastly different morphologies influence maneuvering performance across elevations.

A common requirement of diverse disciplines of biology is to have a means of quantitatively describing behavior. This project utilizes a custom-designed, automated analysis of movement to identify the fundamental building blocks of maneuverability. Developing this approach will provide tools that are broadly applicable for studying complex movement in animals. The educational training will foster the scientific development of a postdoctoral scholar, graduate students, and undergraduate students from under-represented groups. These participants will receive integrative training in computational biology and comparative biomechanics. The results of the research will be used to develop a teaching module for use in upper division undergraduate courses. In addition, results produced by the students and the PIs will be presented via scientific conferences, scholarly publications, and public lectures.