Hedonic and nucleus accumbens neural responses to a natural reward are regulated by aversive conditioning.
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.
Department of Psychology, University of Illinois at Chicago, Chicago, Illinois 60607, USA. mroitman@uic.edu
Mitchell F
MF
Roitman
Robert A
RA
Wheeler
Paul H E
PH
Tiesinga
Jamie D
JD
Roitman
Regina M
RM
Carelli
D000200:Action Potentials / Q000502:physiology; D000704:Analysis of Variance; D000818:Animals; D001362:Avoidance Learning / Q000502:physiology*; D001931:Brain Mapping; D003216:Conditioning, Operant / Q000502:physiology*; D004576:Electromyography / Q000379:methods; D005518:Food Preferences / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D009474:Neurons / Q000502:physiology; D009714:Nucleus Accumbens / Q000166:cytology / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012201:Reward; D013395:Sucrose / Q000008:administration & dosage; D013549:Sweetening Agents / Q000008:administration & dosage; D013649:Taste / Q000502:physiology
D013549:Sweetening Agents; D013395:Sucrose