The power of comparison
central nervous system and sensory inputs are essential for coordinated movement. Studies of central pattern generators have influenced profoundly the way we think about neurons, neuronal networks and their functional properties. It is clear, for example, that neuronal circuits can be reconfigured through the action of neuromodulatory neurons to produce a variety of outputs, and that intrinsic membrane properties of neurons are subject to homeostatic regulation. In this special issue, Marder and colleagues describe the effects of temperature on motor patterns generated by the stomatogastric nervous system of the crab, Cancer borealis, and consider how neuronal networks and the output they generate remain stable in the face of extreme temperature fluctuations. Temperature is a central focus also of the contribution from Xu and colleagues who consider the sophisticated mechanisms that have evolved to enable animals to sense and adapt to changes in temperature. In their review, these authors present a strongly comparative viewpoint, and their discussion offers fascinating insights into the effects of temperature on aging and longevity. Homeostasis, as an overarching theme, is central also to the contribution by Keene and colleagues, who discuss how the brain of the fruit fly modulates sleep and how sleep in this insect, and in other animals, is influenced by metabolic state. Insects have a long history in the study of sleep. Cockroaches, for example, were used to provide the first demonstration that animals show compensatory mechanisms after sleep loss (Campbell and Tobler, Neurosci Biobehav Rev 8:269–300, 1984), and the genetic mechanisms that underlie sleep and sleep disorders are now being investigated extensively using the fruit fly, Drosophila. Callaerts and colleagues use Drosophila to provide insights into the importance of glia in normal brain function. They explore what is, and what is not, known about This special issue celebrates excellent examples of invertebrate neuroscience. It has its origins in the Cold Spring Harbor Asia (CSHA) Conferences on invertebrate neurobiology held recently in Suzhou, China, and is designed to provide a ‘taster’ of some of the exciting works presented at these meetings. There are of course very many aspects of invertebrate neurobiology that have seen remarkable advances in recent years. This issue highlights a small number of interesting examples. The topics are as diverse as they are interesting, and illustrate well the excitement that exists in current invertebrate neuroscience. For many years, there has been intense interest in the neuronal circuits (central pattern generators, CPGs) that produce rhythmic motor patterns supporting activities such as feeding, walking, swimming, and breathing. Sakurai and Katz discuss the unique perspective that the study of gastropod CPGs brings to this field. One important emerging concept is that different and independently evolved circuits using the same set of neurons can generate the same behavior. Their contribution to this special issue illustrates beautifully the power of a comparative approach. This theme is expanded upon by Ayali and colleagues who discuss recent work on an important model of legged locomotion, the cockroach, Periplaneta americana. In their review, they emphasize that motor system activity is modulated by sensory information and that dynamic interactions between the