Worm sleep: a universal behavior meets a simple model system

All animals sleep, or do they? This question remains controversial. If sleep is truly universal to the animal kingdom then even the simplest model animal, the hydrogen atom of neuroscience if you will, should sleep. The nematode Caenorhabditis elegans develops through four larval stages before it reaches adulthood. At the transition between stages and before it molts, i.e., synthesizes a new exoskeleton and sheds the old one, it exhibits a quiescent state termed lethargus. In a seminal paper in 2008, David Raizen has demonstrated that lethargus bears several similarities to sleep. The talk will describe our contributions to establishing C. elegans lethargus as a model for sleep, as well as related topics. We approach the problem with a combination of behavioral, computational, genetic, physiological and optical techniques. Examples of behavioral dynamics associated with lethargus include the nematode’s hockey stick-like posture and the maneuver that it facilitates, non-Markovian locomotion dynamics (micro-homeostasis) and the modulation of global locomotion states over long timescales. As time permits, the modulation of neuronal activity associated with lethargus, the role of serotonin in sleep-wake transitions, and a novel nematode nociceptor will be briefly discussed.