Nucleus Accumbens Core and Shell are Necessary for Reinforcer Devaluation Effects on Pavlovian Conditioned Responding.

Teghpal Singh,Domenic H Cerri,Geoffrey Schoenbaum,Michael A Mcdannald,Richard Z Haney

doi:10.3389/fnint.2010.00126

Abstract

The nucleus accumbens (NA) has been hypothesized to be part of a circuit in which cue-evoked information about expected outcomes is mobilized to guide behavior. Here we tested this hypothesis using a Pavlovian reinforcer devaluation task, previously applied to assess outcome-guided behavior after damage to regions such as the orbitofrontal cortex and amygdala that send projections to NA. Rats with sham lesions or neurotoxic lesions of either the core or shell subdivision of NA were trained to associate a 10-s CS+ with delivery of three food pellets. After training, half of the rats in each lesion group received food paired with illness induced by LiCl injections; the remaining rats received food and illness unpaired. Subsequently, responding to the CS+ was assessed in an extinction probe test. Both sham and lesioned rats conditioned to the CS+ and formed a conditioned taste aversion. However only sham rats reduced their conditioned responding as a result of reinforcer devaluation; devalued rats with lesions of either core or shell showed levels of responding that were similar to lesioned, non-devalued rats. This impairment was not due to the loss of motivational salience conferred to the CS+ in lesioned rats as both groups responded similarly for the cue in conditioned reinforcement testing. These data suggest that NA core and shell are part of a circuit necessary for the use of cue-evoked information about expected outcomes to guide behavior.

Highlights

A critical feature of adaptive behavior is the ability to use expectations of outcomes to appropriately guide behavior
While post hoc testing revealed that sham rats responded significantly more during the pre-CS baseline period than core and shell lesioned rats (Tukey’s honestly significant difference (HSD), p < 0.05, df = 43), on the final day of conditioning there were no significant differences in responding during the CS + in any group
Here we show that nucleus accumbens (NA) lesions impair changes in Pavlovian conditioned responding after reinforcer devaluation, in a task that is sensitive to damage to upstream regions of the orbitofrontal cortex (OFC) and ABL

Summary

Introduction

A critical feature of adaptive behavior is the ability to use expectations of outcomes to appropriately guide behavior. Neurons in the NA fire to cues in a manner that appears to signal their associative significance (Setlow et al, 2003; Nicola et al, 2004; Peoples et al, 2004; German and Fields, 2007; Hollander and Carelli, 2007; Kimchi and Laubach, 2009; Roesch et al, 2009; van der Meer and Redish, 2009), and this region is critical to Pavlovian-toinstrumental transfer and other aspects of Pavlovian responding (Parkinson et al, 1999a,b, 2000; Corbit et al, 2001; Hall et al, 2001; Cardinal et al, 2002b; de Borchgrave et al, 2002; Balleine and Corbit, 2005) These data suggest that NA, along with ABL and afferent regions in lateral OFC, might be part of a circuit critical for the use of cueevoked information about expected outcomes to guide behavior. We tested the role of NA core and shell in the Pavlovian reinforcer devaluation task and found pre-training lesions disrupted the ability of the animal to alter conditioned responding based on the current value of the outcome

Methods

Results

Conclusion