A two-neuron system for adaptive goal-directed decision-making in Lymnaea

During goal-directed decision-making, animals must integrate information from the external environment and their internal state to maximize resource localization while minimizing energy expenditure. How this complex problem is solved by the nervous system, remains poorly understood. Here, using a combined behavioral and neurophysiological approach, we demonstrate that the mollusk Lymnaea performs a sophisticated form of decision-making during food-searching behavior using a core system comprised of just two neuron types. The first, a command-like cell, reports the presence of food and the second, a multifunctional interneuron, encodes motivational state, acting as a gain controller for adaptive behavior in the absence of food. Using an in vitro analog of the decision-making process, we show that the system employs an energy-management strategy, switching between a low and a high-use mode depending on the outcome of the decision. Our study reveals a parsimonious mechanism that drives a complex adaptive decision-making process. The first file contains data for behavioral experiments investigating appetitive biting behavior in <i>Lymnaea</i> in the absence of food. The second file contains data for electrophysiological experiments described in the paper. The data is organized according to the figures in the paper.