The nucleus accumbens (NAc) is thought to be a site of integration of positively and negatively valenced information and action selection. Functional differentiation in valence processing has previously been found along the rostrocaudal axis of the shell region of the NAc in assessments of unconditioned motivation. Given that the core region of the NAc has been implicated in the elicitation of motivated behavior in response to conditioned cues, we sought to assess the role of caudal, intermediate and rostral sites within this subregion in cue-elicited approach-avoidance decisions. Rats were trained to associate visuo-tactile cues with appetitive, aversive and neutral outcomes. Following the successful acquisition of the cue-outcome associations, rats received microinfusions of GABAA and GABAB receptor agonists (muscimol/baclofen) or saline into the caudal, intermediate or rostral NAc core, and were then exposed to a superimposition of appetitively and aversively valenced cues vs. neutral cues in a ‘conflict test’, as well as to the appetitive vs. neutral cues, and aversive cues vs. neutral cues, in separate conditioned preference/avoidance tests. Disruption of activity in the intermediate to caudal parts of the NAc core resulted in a robust avoidance bias in response to motivationally conflicting cues, as well as a potentiated avoidance of aversive cues as compared with control animals, coupled with an attenuated conditioned preference for the appetitive cue. These results suggest that the caudal NAc core may have the capacity to exert bidirectional control over appetitively and aversively motivated responses to valence signals.
Significance Statement The nucleus accumbens is a heterogeneous structure, known as a site of confluence of limbic information. While traditionally thought to divide into shell and core subregions, recent evidence has demonstrated a topographical organization of valence information processing along a rostrocaudal gradient in the shell. However, such rostrocaudal differentiation of valenced information has not been well characterised in the core. Using transient, localised inactivation of the core combined with a novel approach-avoidance conflict paradigm, we found evidence of a dissociation between the rostral and caudal core in the processing of valenced cues in motivating approach and avoidance responses. Our findings implicate the caudal core to be critical in facilitating cued approach, while suppressing cued avoidance in the face of motivational conflict.
Authors report no conflict of interest.
This work was supported by the Natural Science and Engineering Council (N.S.E.R.C) of Canada, Discovery grant number 402642.