Exploratory decisions of the Caenorhabditis elegans male: a conflict of two drives.

The ability to generate behavioral plasticity according to ever-changing physiological demands and environmental conditions is a universal feature of decision-making circuits in all animals. Decision-making requires complex integration of internal states with sensory context. As a mate searching strategy, the Caenorhabditis elegans male modifies his exploratory behavior in relation to a source of food according to recent sensory experience with mates. Information about the reproductive and nutritional status of the male is also incorporated in his choice of exploratory behavior. The study of mate searching in the C. elegans male, a genetic model organism with a nervous system of only 383 neurons, provides the opportunity to elucidate the molecular and cellular mechanisms of state-dependent control of behavior and sensory integration. Here I review our progress in understanding the physiological and environmental regulation of the male's exploratory choices - to explore in search of mates or to exploit a source of food - and the neural circuits and neuromodulator pathways underlying this decision.