Entry Date:
September 30, 2008

Modular Control of Natural Motor Behavior

Principal Investigator Emilio Bizzi


We address the issue of how the central nervous system may coordinate the many degrees of freedom of the musculoskeletal apparatus to control motor behavior. In particular, we explore the idea that the control of limb movements is organized in a small number of modules that can be flexibly combined. We are testing the hypothesis that the muscle activation patterns observed in natural motor behaviors might be generated by linear combinations of a small number of muscle synergies. In one series of experiments, EMGs are recorded in intact frogs from fourteen leg muscles during different forms of locomotion (swimming, jumping, and walking) and defensive reflexes (wiping and extensor-thrust). We find synergies that are similar across different behaviors and frogs, though a few synergies appear to be recruited only in specific behaviors. Our results support a modular organization of the control of natural motor behavior and suggest that some of the modules may be organized in the spinal cord and shared across behaviors. A factorization algorithm is used to extract a set of synergies whose non-negative combinations can explain the majority of variation in the data.