Current Evidence for Sleep States in Drosophila: Findings and Implications

Sleep is an essential biological behavior, with its absence leading to severe consequences, including death. In mammals, sleep consists of distinct states—such as REM and non-REM—that are often thought to serve different physiological functions. Traditionally, Drosophila melanogaster were believed to experience sleep as a single, unitary state. However, recent research suggests that sleep in flies is more complex than previously understood and can be divided into distinct states. This raises the possibility that the fly model can be used to investigate the functional role(s) of each sleep state. In this review, we explore the behavioral, neurophysiological, metabolic, and transcriptional evidence supporting the existence of these sleep states in Drosophila. We assess whether consistent criteria can be established for these sleep states and propose a new direction for sleep research by identifying genetic correlates associated with these states. This approach has the potential to deepen our understanding of sleep architecture and its genetic underpinnings, offering insights that may extend beyond the Drosophila model to other species, including humans.