Learning from biological systems: modeling neural control

We have been pursuing a modular approach to modeling and investigating the neural control of posture and movement. A modular approach is a practical and natural way of investigating the function and structure of the complex central nervous system (CNS). The modules can include skeletal dynamics, muscle dynamics with recruitment and force-generation characteristics, basic spinal cord neural circuits responsible for the local stretch reflex, interneuronal networks that provide modulation of various reflexes, various structures of brain circuits, and control strategy decision-making centers. The anatomical detail and complexity of each module can vary depending on the specific scientific question or motor task to be investigated and the extent of information available on the hierarchy. To demonstrate the modular approach, we present two examples that illustrate how biological motor control tasks can be investigated in varying degrees of complexity and detail. One example shows that a model with detailed anatomical structure and dynamic properties has to be developed to investigate the detailed interactions among several sensory feedback loops in the spinal cord. The other example shows that when investigating whole-body behavior, a grosser structured model with lumped components is more tractable so issues such as the interaction of spinal cord regulation and upper CNS intelligent control can be investigated.