Development of motor rhythms in zebrafish embryos.

The nervous system can generate rhythms of various frequencies; on the low-frequency side, we have the circuits regulating circadian rhythms with a 24-h period, while on the high-frequency side we have the motor circuits that underlie flight in a hummingbird. Given the ubiquitous nature of rhythms, it is surprising that we know very little of the cellular and molecular mechanisms that produce them in the embryos and of their potential role during the development of neuronal circuits. Recently, zebrafish has been developed as a vertebrate model to study the genetics of neural development. Zebrafish offer several advantages to the study of nervous system development including optical and electrophysiological analysis of neuronal activity even at the earliest embryonic stages. This unique combination of physiology and genetics in the same animal model has led to insights into the development of neuronal networks. This chapter reviews work on the development of zebrafish motor rhythms and speculates on birth and maturation of the circuits that produce them.