The Role of Locus Coeruleus-Norepinephrine Function in Rat Foraging Behavior

Abstract

Foraging behavior describes an organism’s search for food, and is thus fundamental to the lives of animals. More generally, foraging refers to the decision of whether to exploit a resource now or incur a cost in order to obtain a resource of greater utility later. While the neural mechanisms motivating foraging remain poorly understood, the adaptive gain theory proposes that the locus coeruleus-norepinephrine (LC-NE) system is implicated in optimizing behavioral performance. Specifically this theory posits that the LC-NE system integrates cost and reward inputs to generate two types of LC function: phasic and tonic activation. Phasic LC activation is associated with the optimization of task performance, while tonic LC activation involves task disengagement as a result of waning task utility (Aston-Jones & Cohen, 2005). To assess the LC-NE system’s role in modulating foraging behavior, we characterized rat foraging behavior by testing rats on a foraging task simulating a patchy environment. We observed that rats behaved in accordance with the optimal solution for foraging in this task, as defined by the marginal value theorem (Charnov, 1976). Furthermore, we successfully activated the rat LC with the hM3Dq designer receptor. These findings extend an understanding of the neurobiology underlying foraging decisions, as well as provide support for assessing rat foraging behavior through using the hM3Dq designer receptor to modulate the LC-NE system and subsequently assess its role in influencing rat foraging decisions. Keywords: foraging behavior, marginal value theorem, locus coeruleusnorepinephrine system, adaptive gain theory, DREADDs