Involvement of the central nucleus of the amygdala and nucleus accumbens core in mediating Pavlovian influences on instrumental behaviour.

Pavlovian conditioned cues exert a powerful influence on instrumental actions directed towards a common reward, this is known as Pavlovian-to-instrumental transfer (PIT). The nucleus accumbens (NAcc) has been hypothesized to function as an interface between limbic cortical structures required for associative conditioning, like the amygdala, and response mechanisms through which instrumental behaviour can be selected and performed. Here we have used selective excitotoxic lesions to investigate the involvement of subnuclei of the amygdala as well as the core and shell regions of the nucleus accumbens on PIT in rats. Within the amygdala, selective lesions of the central nucleus (CeN), but not of the basolateral nucleus (BLA), abolished the PIT effect. In addition, selective lesions of the NAcc core, but not the NAcc shell, also abolished PIT. None of the lesions impaired the acquisition of Pavlovian food cup approaches or instrumental responding itself. These data demonstrate that the CeN and NAcc core are central components of the neural system mediating the impact of Pavlovian cues on instrumental responding. We suggest that this effect may depend upon the regulation of the dopaminergic innervation of the NAcc core by projections from the CeN to the ventral tegmental area.