Figure 1.
A, Schematic of the medial prefrontal cortex projections to the amygdala hypothesized to underlie extinction. The IL excites GABAergic intercalated neurons, which in turn inhibit GABAergic cells in the centromedial amygdala (CeM). The PL excites glutamatergic neurons in the basolateral amygdala (BL), which excite GABAergic neurons in the CeM. B, Schematic of the relative contribution of the conditioned stimulus input into the amygdala before and after extinction. Before extinction, input about the conditioned stimulus to the amygdala generates increased firing in projection neurons, which promotes freezing behavior (top). After extinction, the conditioned stimulus strongly activates interneurons (bottom), thereby inhibiting freezing behavior. GABAergic pathways are in blue, and glutamatergic pathways are in red. ITC, Intercalated nuclei; CeL, centrolateral amygdala. This figure was adapted from Swanson (1992).