Chiel - 2009 - The brain in its body: motor control and sensing in a biomechanical context

Citation

Chiel HJ, Ting LH, Ekeberg O, Hartmann MJ. The brain in its body: motor control and sensing in a biomechanical context. J Neurosci. 2009 Oct 14;29(41):12807-14. PUBMED

10 Word Summary

Biological motion requires nervous and mechanical pathways.

Analysis of both neural and mechanical pathways is required to understand biological motion.

Abstract

Although it is widely recognized that adaptive behavior emerges from the ongoing interactions among the nervous system, the body, and the environment, it has only become possible in recent years to experimentally study and to simulate these interacting systems. We briefly review work on molluscan feeding, maintenance of postural control in cats and humans, simulations of locomotion in lamprey, insect, cat and salamander, and active vibrissal sensing in rats to illustrate the insights that can be derived from studies of neural control and sensing within a biomechanical context. These studies illustrate that control may be shared between the nervous system and the periphery, that neural activity organizes degrees of freedom into biomechanically meaningful subsets, that mechanics alone may play crucial roles in enforcing gait patterns, and that mechanics of sensors is crucial for their function.

Notes

• Major questions of the paper
  • How can the nervous system group DoFs?
  • How can the nervous system respond robustly to changing environments?
  • How does neural input affect motor output?
  • How does motor movement affect sensory processing?
• Manipulating neuromechanical equilibrium points for multifunctionality
  • Aplysia use same system for biting, swallowing, rejetion, and egg-laying
  • Neuromechanical equilibrium points specify behavior and specify how much energy is required to move between the different biomechanical states.
• Neuromechanical interactions underlying muscle synergy control of posture and movement
  • Sensory binding problem: incorporation of multiple variable sensory streams into a recognizable event occuring in the physical world.
  • Motor binding problem: Movement intentions must employ complex spatio-temporal patterns to produce coordinated motion.
  • What are the neuromechanical structures governing the hierarchal selection and modulstion of muscles during movement?
  • How do these mechanisms develop, evolve and decay during one's lifespan?
• Neuromechanical models of locomotion
  • Regulation of muscle stiffness was found to be important so that "resonant" behavior could be modeled.
  • Modeling of walking suggests that the system is critically damped
• Biomechanical constraints on sensing behaviors
  • Whisker sensing is highly dependent on the mechanical system location and geometry
  • Distance and textural information is encoded as moments and forces at the base of the whisker
• Conclusions
  • To understand "neuromechanics" requires examining both the mechanical and neurological systems in conjunction with the environment in order to understand the full behavior.
  • Major open question is what serves the basis for "motor invariants"?