Control Of Posture And Locomotion

R. B. Stein Department of Physiology, University of Alberta, Edmonton, Canada The impetus for this volume and the conference that gave rise to it was the feeling that studies on motor control had reached a turning point. In recent years, studies on motor units and muscle receptors have become increasingly detailed. Attempts to integrate these studies into quantitative models for the spinal control of posture have appeared and preliminary attempts have been made to include the most direct supraspinal pathways into these models (see for example the chapters by Nashner and Melvill Jones et al. in this volume). Thus, we felt that the time was ripe to summarize these developments in a way which might be useful not only to basic medical scientists, but also to clinicians dealing with disorders of motor control, and to bioengineers attempting to build devices to assist or replace normal control. Over the past few years, computer methods have also made possible increasingly detailed studies of mammalian locomotion, and improved physiological and pharmacological studies have appeared. There seems to be almost universal agreement now that the patterns for locomotion are generated in the spinal cord, and that they can be generated with little, if any, phasic sensory information (see chapters by Grillner and Miller et al. ). This concludes a long controversy on whether chains of reflexes or central circuits generate stepping patterns. The nature of the pattern generators in mammals remains obscure, but invertebrate studies on locomotion have recently made striking advances.

Most routine motor tasks are complex, involving load transmission through out the body, intricate balance, and eye-head-shoulder-hand-torso-leg coor dination. The quest toward understanding how we perform such tasks with skill and grace, often in the presence of unpredictable perturbations, has a long history. This book arose from the Ninth Engineering Foundation Con ference on Biomechanics and Neural Control of Movement, held in Deer Creek, Ohio, in June 1996. This unique conference, which has met every 2 to 4 years since the late 1960s, is well known for its informal format that promotes high-level, up-to-date discussions on the key issues in the field. The intent is to capture the high quality ofthe knowledge and discourse that is an integral part of this conference series. The book is organized into ten sections. Section I provides a brief intro duction to the terminology and conceptual foundations of the field of move ment science; it is intended primarily for students. All but two of the re maining nine sections share a common format: (l) a designated section editor; (2) an introductory didactic chapter, solicited from recognized lead ers; and (3) three to six state-of-the-art perspective chapters. Some per spective chapters are followed by commentaries by selected experts that provide balance and insight. Section VI is the largest section, and it con sists of nine perspective chapters without commentaries.

Neuromechanics is a new, quickly growing field of neuroscience research that merges neurophysiology, biomechanics and motor control and aims at understanding living systems and their elements through interactions between their neural and mechanical dynamic properties. Although research in Neuromechanics is not limited by computational approaches, neuromechanical modeling is a powerful tool that allows for integration of massive knowledge gained in the past several decades in organization of motion related brain and spinal cord activity, various body sensors and reflex pathways, muscle mechanical and physiological properties and detailed quantitative morphology of musculoskeletal systems. Recent work in neuromechanical modeling has demonstrated advantages of such an integrative approach and led to discoveries of new emergent properties of neuromechanical systems. Neuromechanical Modeling of Posture and Locomotion will cover a wide range of topics from theoretical studies linking the organization of reflex pathways and central pattern generating circuits with morphology and mechanics of the musculoskeletal system (Burkholder; Nichols; Shevtsova et al.) to detailed neuromechanical models of postural and locomotor control (Bunderson; Edwards, Marking et al., Ting). Furthermore, uniquely diverse modeling approaches will be presented in the book including a theoretical dynamic analysis of locomotor phase transitions (Spardy and Rubin), a hybrid computational modeling that allows for in vivo interactions between parts of a living organism and a computer model (Edwards et al.), a physical neuromechanical model of the human locomotor system (Lewis), and others.

Afferent Control of Posture and Locomotion

This collection of contributions on the subject of the neural mechanisms of sensorimotor control resulted from a conference held in Cairns, Australia, September 3-6, 2001. While the three of us were attending the International Union of Physiological Sciences (IUPS) Congress in St Petersburg, Russia, in 1997, we discussed the implications of the next Congress being awarded to New Zealand. We agreed to organise a satellite to this congress in an area of mutual interest -the neuroscience of movement and sensation. Australia has a long-standing and enviable reputation in the field of neural mechanisms of sensorimotor control. Arguably this reached its peak with the award of a Nobel Prize to Sir John Eccles in 1963 for his work on synaptic transmission in the central nervous system. Since that time, the subject of neuroscience has progressed considerably. One advance is the exploitation of knowledge acquired from animal experiments to studies on conscious human subjects. In this development, Australians have achieved international prominence, particularly in the areas of kinaesthesia and movement control. This bias is evident in the choice of subject matter for the conference and, subsequently, this book. It was also decided to assign a whole section to muscle mechanics, a subject that is often left out altogether from conferences on motor control. Cairns is a lovely city and September is a good time to visit it.

Reflex Control of Posture and Movement