Schematic diagrams of the experimental paradigm and the brain regions analyzed for gene expression. (A) The experimental paradigm consisted of a 15-day training period in which all rats received access to chocolate Ensure and water in one of two distinct environments (contexts A and B). Locomotor activity was measured in context A over the training phase of the study. On the test day, 3 days after the final day of training, rats were reintroduced to context A after an acute 12-hour food deprivation period. Locomotor activity was measured in context A for 45 minutes, after which time rats were killed, and trunk blood and brains were taken for plasma corticosterone assay and in situ hybridization analysis of forebrain gene expression. (B) The brain regions analyzed for activity-dependent gene expression via in situ hybridization included the ventral orbital prefrontal cortex (VO), lateral orbital prefrontal cortex (LO), prelimbic cortex (PreL), infralimbic cortex (InfrL), anterior and posterior cingulate cortex (A and P Cing), primary sensory cortex (S1), agranular insular cortex (AgrIns), piriform cortex (Pir), sensorimotor cortex, nucleus accumbens shell (NAcc shell), nucleus accumbens core (NAcc core), anterior ventrolateral striatum (AVLS), anterior medial striatum (AMS), anterior dorsolateral striatum (ADLS), sensorimotor cortex (SM), posterior ventrolateral striatum (PVLS), posterior medial striatum (PMS), posterior dorsolateral striatum (PDLS), CA1 and CA3 subfields of the dorsal hippocampus, basolateral amygdala (BLA), central nucleus of the amygdala (CeA), periventricular thalamus (PVN), centromedian thalamus (CM), rhomboid and reunions thalamus (Rh/Re), mediodorsal thalamus (MD), ventralposteromedial and ventralposterolateral thalamus (VPM/VPL), lateral hypothalamus (LH), dorsomedial hypothalamus (DMH), ventromedial hypothalamus (VMH), and arcuate hypothalamus. Numbers represent distance from bregma in mm (adapted with permission from ).