Hedonic and nucleus accumbens neural responses to a natural reward are regulated by aversive conditioning

Mitchell F. Roitman; Robert A. Wheeler; Paul H.E. Tiesinga; Jamie D. Roitman; Regina M. Carelli

doi:10.1101/lm.1869710

Hedonic and nucleus accumbens neural responses to a natural reward are regulated by aversive conditioning

¹Department of Psychology, University of Illinois at Chicago, Chicago, Illinois 60607, USA
²Department of Psychology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
³Donders Institute for Brain, Cognition and Behavior, Radboud University Nijmegen, Nijmegen 6525, The Netherlands
⁴Physics and Astronomy Department, University of North Carolina, Chapel Hill, North Carolina 27599, USA
⁵Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA

↵6 These authors contributed equally to this work.

Abstract

The nucleus accumbens (NAc) plays a role in hedonic reactivity to taste stimuli. Learning can alter the hedonic valence of a given stimulus, and it remains unclear how the NAc encodes this shift. The present study examined whether the population response of NAc neurons to a taste stimulus is plastic using a conditioned taste aversion (CTA) paradigm. Electrophysiological and electromyographic (EMG) responses to intraoral infusions of a sucrose (0.3 M) solution were made in naïve rats (Day 1). Immediately following the session, half of the rats (n = 6; Paired) received an injection of lithium chloride (0.15 M; i.p.) to induce malaise and establish a CTA while the other half (n = 6; Unpaired) received a saline injection. Days later (Day 5), NAc recordings during infusions of sucrose were again made. Electrophysiological and EMG responses to sucrose did not differ between groups on Day 1. For both groups, the majority of sucrose responsive neurons exhibited a decrease in firing rate (77% and 71% for Paired and Unpaired, respectively). Following conditioning, in Paired rats, EMG responses were indicative of aversion. Moreover, the majority of responsive NAc neurons now exhibited an increase in firing rate (69%). Responses in Unpaired rats were unchanged by the experience. Thus, the NAc differentially encodes the hedonic value of the same stimulus based on learned associations.