Spike Timing, Precision, and Sensory Conflict in Motor Control
School of Physics
Movement is a defining feature of animals. They have evolved diverse locomotor strategies, demonstrating remarkable stability and maneuverability in complex environments. To accomplish this, an animal’s nervous system acquires, processes and acts upon information, but must interface with the animal’s environment through the physics of sensors and actuators. By understanding the function of peripheral sensory systems and muscle mechanics we can construct testable principles of how the nervous system functions to enable versatile locomotion. We explore three insights gained from the study of invertebrate systems, but that touch on general strategies for motor control. 1) Muscles in a large variety of animals are tuned for submaximal power output given their timing of activation. We show that this enables greater capacity for control via precise, even sub-millisecond, timing of individual motor spikes. 2) By altering sensory feedback loops, control theory can allow us to generate strong analytical and experimental conditions that provide a framework for testing how sensory modalities are integrated. We show that in free flight, mechanoreception and vision are combined linearly and generalize to allow prediction of individual flight trajectories with up to 95% accuracy. 3) Dimensionality reduction and information theoretic approaches to understanding the coordination of motor signals shows that phase and time scale are important factors. Motor signals that coordinate muscle synergies at one time scale encode independent information within a single gait cycle. The emerging view is that timing, feedback, and mechanics condition how neural systems must function to control movement.
Simon Sponberg is an assistant professor of physics and biological sciences at the Georgia Institute of Technology in Atlanta. He earned his Ph.D. in Integrative Biology from UC, Berkeley with Professor Robert Full. He was an NSF postdoctoral fellow in biological informatics at the University of Washington where he worked with Professor Tom Daniel (Biology) and Professor Adrienne Fairhall (Physiology & Biophysics). Simon is a Hertz fellow and was awarded the young investigator award from the International Society of Neuroethology. His work recently was awarded an NSF CAREER grant. His research is at the interface of physics and physiology, using a dynamic systems and neuromechanics approach to understand locomotion, and especially maneuverability and stability, in biological systems.