Amygdala and nucleus accumbens involvement in appetitive extinction

Abstract

Extinction of appetitive conditioning is regarded as an important model for the treatment of psychiatric disorders like addiction. However, very few studies have investigated its neural correlates. Therefore, we investigated neural correlates of appetitive extinction in a large human sample including all genders (N = 76, 40 females) to replicate and extend results from a previous study. During differential appetitive conditioning, one stimulus (CS+) was paired with the chance to win a monetary reward, whereas another stimulus (CS-) was not. During appetitive extinction on the next day, neither the CS+ nor the CS- were reinforced. After successful acquisition of appetitive conditioning, the extinction phase elicited significant reductions of valence and arousal ratings toward the CS+ and a significant reduction in skin conductance responses to the CS+ from early to late extinction. On a neural level, early extinction showed significant differential (CS+ - CS-) activation in dACC and hippocampus, whereas involvement of the vACC and caudate nucleus did not replicate. The differential activation of amygdala and nucleus accumbens during late extinction was replicated, with the amygdala displaying significantly higher differential activation during the late phase of extinction as compared to the early phase of extinction. We show discernible signals for reward learning and extinction in subregions of amygdala and nucleus accumbens after extinction learning. This successful replication underlines the role of nucleus accumbens and amygdala in neural models of appetitive extinction in humans that was previously only based on animal findings.

Keywords: amygdala; conditioning; fMRI; nucleus accumbens; reward.

Figure 1

(left) Time course of contrast estimates (CS+ − CS−) at the location of the significant peak voxels during acquisition (blue) and late extinction (green) in the left NAcc (above) and right amygdala (below). The line plots show the contrast estimates for the location of each of the four peak voxels (acquisition/extinction peak in NAcc & acquisition/extinction peak in amygdala) for the early and late phase of acquisition as well as the early and late extinction phases. At the location of acquisition‐peak voxels, there is significant differential BOLD‐contrast during acquisition but a marked reduction of differential BOLD‐contrast during extinction. At the location of extinction‐peak voxels, there is differential BOLD‐contrast similar to that at the acquisition peak voxels during acquisition but discernible patterns of activation during extinction. (right) Significant activation in NAcc (above) and amygdala (below) during late extinction