A Model of Leg Coordination in the Stick Insect, Carausim Morosus – IV. Comparisons of Different Forms of Coordinating Mechanisms

The kinematic model presented in a separate report is used here to investigate several questions concerning the nature of the coordinating mechanisms. First, one or more mechanisms are inactivated in order to compare the relative efficiencies of the different coordinating mechanisms in maintaining proper coordination. Second, the most efficient mechanism, the position-dependent influence, is varied in order to illustrate the consequences for coordination. Third, the strength of the contralateral coupling is varied in order to make predictions about how contralateral legs establish alternation when started from symmetric positions. The consequences of adding reciprocal contralateral inhibition during swing is tested in the same context. © 1992 Springer-Verlag

Six-legged walking in insects: how CPGs, peripheral feedback, and descending signals generate coordinated and adaptive motor rhythms

Walking is a rhythmic locomotor behavior of legged animals, and its underlying mechanisms have been the subject of neurobiological research for more than 100 years. In this article, we review relevant historical aspects and contemporary studies in this field of research with a particular focus on the role of central pattern generating networks (CPGs) and their contribution to the generation of six-legged walking in insects. Aspects of importance are the generation of single-leg stepping, the generation of interleg coordination, and how descending signals influence walking. We first review how CPGs interact with sensory signals from the leg in the generation of leg stepping. Next, we summarize how these interactions are modified in the generation of motor flexibility for forward and backward walking, curve walking, and speed changes. We then review the present state of knowledge with regard to the role of CPGs in intersegmental coordination and how CPGs might be involved in mediating descending influences from the brain for the initiation, maintenance, modification, and cessation of the motor output for walking. Throughout, we aim to specifically address gaps in knowledge, and we describe potential future avenues and approaches, conceptual and methodological, with the latter emphasizing in particular options arising from the advent of neurogenetic approaches to this field of research and its combination with traditional approaches