Essentials of sleep recordings in Drosophila: moving beyond sleep time.

The power of Drosophila genetics can be used to facilitate the molecular dissection of sleep regulatory mechanisms. While evaluating total sleep time and homeostatic processes provides valuable information, other variables, such as sleep latency, sleep bout duration, sleep cycle length, and the time of day when the longest sleep bout is initiated, should also be used to explore the nature of a genetic lesion on sleep regulatory processes. Each of these variables requires that the recording interval used to identify periods of sleep and waking be determined accurately and empirically. This article describes the procedures for recording sleep in Drosophila and associated methodological constraints. In addition, it provides results from a normative data set of 1037 Canton-S female flies and 639 male flies to illustrate the nature and variability of sleep variables that one can extract from 24 h of data collection in Drosophila.