The amygdala's ability to assign value to experience depends on a compact set of interconnected nuclei and cell populations. The basolateral complex (BLA), which includes the lateral (LA) and basal (BA) nuclei, is made up mostly of excitatory neurons. The central nucleus (CeA), in contrast, is predominantly inhibitory.
Anatomically, information can move from LA to BA and then on to CeA. A second route connects LA directly to CeA. This arrangement places LA at the sensory-input stage and BA at a stage where context is combined with sensory information before signals reach CeA.
The molecular picture is not a simple positive/negative switch. Rspo2+ cells have been associated with positive valence, while Ppp1r1b+ cells are linked to negative valence. Fezf2 co-labels with Rspo2, but the population is split: half fall on the positive-valence side and half on the negative-valence side. Co-labeling with Rspo2 therefore does not guarantee a single valence identity.
Reference: Zhang, X., Guan, W., Yang, T. et al. Genetically identified amygdala–striatal circuits for valence-specific behaviors. Nat Neurosci (2021). https://doi.org/10.1038/s41593-021-00927-0