11 Invertebrate Central Pattern Generators

Abstract

The neural bases of complex, rhythmic movements, such as walking, chewing, or swimming, have been studied as a window into understanding how nervous systems generate behavior. Work in invertebrates has been particularly fruitful in providing general insights into how neural circuits control the body. The neural control for almost all rhythmic movements originates in neural circuits called central pattern generators (CPGs), which can produce rhythmic neural outputs autonomously without sensory feedback or patterned input (Delcomyn 1980). Invertebrate CPGs have been intensively studied. We make no pretense of covering all invertebrate CPGs in this chapter and, indeed, can provide only superficial coverage of those we do discuss. For more detailed information, the reader should consult more comprehensive CPG reviews (Selverston and Moulins 1987; Harris-Warrick et al. 1992; Pearson 1993; Marder and Calabrese 1996; Orlovsky et al. 1999; Nusbaum and Beenhakker 2002; Hooper and DiCaprio 2004; Kristan et al. 2005; Marder et al. 2005). Our intent instead is to provide an overview of the general principles that have been gained from studying invertebrate CPGs. Before moving to this overview, however, two further points should be made. First, due to various experimental advantages and limitations, different questions are typically studied in different preparations. Consequently, in no one preparation are all aspects of motor pattern generation—central mechanisms, the role of sensory input, and transformation into movement—understood. For example, much is known about how cellular properties contribute to motor pattern production in the CPGs of the crustacean stomatogastric system (Selverston and Moulins 1987;...