Neural Mechanisms of Leg Motor Control in Crayfish: Insights for Neurobiologically-Inspired Autonomous Systems

Neural Mechanisms of Leg Motor Control in Crayfish: Insights for Neurobiologically-Inspired Autonomous Systems

Didier Le Ray (Université de Bordeaux, France), Morgane Le Bon-Jego (Université de Bordeaux, France) and Daniel Cattaert (Université de Bordeaux, France)
DOI: 10.4018/978-1-59904-996-0.ch002

Abstract

Computational neuroscience has a lot to gain from invertebrate research. In this chapter focusing on the sensory-motor network that controls leg movement and position in crayfish, we describe how simple neural circuitry can integrate variable information to produce an adapted output function. We describe how a specific sensor encodes the dynamic and static parameters of leg movements, and how the central motor network assimilates and reacts to this information. We then present an overview of the regulatory mechanisms thus far described that operate at the various levels of this sensory-motor network to organize and maintain the system into a dynamic range. On the basis of this simple animal model, some basic neurobiological concepts are presented which may provide new insights for engineering artificial autonomous systems.
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Multi-Sensory Coding Of Leg Movements

Crayfish possess an external skeleton that allows movements only at the various joints, the movement of each joint being coded by simple sensory organs. Among these, the leg coxopodite-basipodite chordotonal organ (CBCO) plays a pivotal role in the control of locomotion and posture, since it monitors vertical leg movements (Figure1). This proprioceptor consists of an elastic strand of connective tissue in which sensory cells are embedded and whose function is comparable to that of joint receptors in mammals (Clarac et al., 2000). The CBCO strand is stretched during opening of the second, unidirectional joint and released during closure, which corresponds respectively to downward and upward movements of the leg. The sensing apparatus of the CBCO is composed of 40 neurons that are equally divided into 20 stretch-sensitive and 20 release-sensitive neurons that code depression and levation of the leg, respectively (see Cattaert & LeRay, 2001).

Figure 1.

Sensory-motor network controlling leg movements in crayfish. (A) Location of the coxo-basipodite chordotonal organ (CBCO) that encodes vertical movements of the crayfish walking leg. (B) In vitro preparation of the locomotor nervous system consisting of the last thoracic (T3-T5) and first abdominal (A1) ganglia, together with the levator and depressor nerves (Lev n, Dep n), and the sensory nerve (CBCO n) that can be recorded extracellularly. Simultaneous intracellular recordings can also be made from motoneurons (e.g., Dep MN) and CBCO terminals. A mechanical puller mimics natural vertical movements of the leg by stretching and releasing the CBCO strand

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