Common principles of motor control in vertebrates and invertebrates.

Abstract

Comparative neurobiology has proven to be a powerful discipline for elucidating the principles that describe the evolution, development, and functioning of the nervous system (Arb as et a11991; Cohen & Strumwasser 1985; Heiligenberg 1991). Studies on invertebrates have contributed sub­ stantially to establishing many of these principles. Some noteworthy ex­ amples are the mechanisms that establish the diversity of potassium chan­ nels (Jan & Jan 1990; MacKinnon 1991), the ionic mechanisms that generate action potentials (Hodgkin & Huxley 1952), and the cellular and molecular events that underlie learning and memory (Carew & Sahley 1986; Hawkins & Kandel 1990). The analysis of more complex integrative processes has also benefited from studies of invertebrate nervous systems. One example is the influence that the finding of lateral inhibition in the eye of Limulus (Hartline et al 1956) had on our understanding of sensory processing in more complex systems. Another is the profound effect that the analysis of rhythmic motor systems in invertebrates has had on inves­ tigations on rhythmic pattern generating networks in vertebrates (Getting 1988; Grillner 1981; Grillner & Wallen 1985). More recently, the utility of analyzing the action of neuromodulator� on the functioning of neuronal