Investigating the Role of the Locus Coeruleus on Rodent Decision-Making Using a Foraging Model

Abstract

Animals scavenge and collect resources from their environment through a process called foraging. For resources like food, it is essential animals forage efficiently for optimal growth and survival. Prior research has revealed that many species including humans forage optimally as the marginal value theorem predicts. (Charnov, 1976; Cassini, Kacelnik, Segura, 1990; Agetsuma, 1999; Pkye, 1978; Cowie, 1977; Smith & Winterhalder, 1992). However the neural mechanisms underlying foraging remain poorly understood. This study attempts to clarify the neural basis of foraging using the principles of adaptive gain theory, which proposes the locus coeruleus (LC) optimizes performance on tasks such as foraging by promoting adaptive strategies. Specifically this study follows adaptive gain theory’s principals that phasic LC activity promotes task exploitation in states of high reward while tonic LC activity promotes exploration of alternatives in states of low reward (Aston-Jones & Cohen, 2005). Our investigation uses a DREADD experimental design to artificially induce LC tonic activity (Vazey & Aston-Jones, 2014). We demonstrate LC’s significant role in rat decision-making behavior by combining the DREADD technique with a novel foraging paradigm. Analysis of behavioral data using a diffusion decision model assessed the impact of tonic LC activity on decision-making and demonstrates LC controls the exploitation-exploration balance by modulating decision noise.