The auditory CS information reaches the amygdala via the direct thalamic pathway and indirect cortical pathway. The footshock US information is relayed to the amygdala via the ascending pain pathways. The CS-US association formation is thought to occur in specific subnuclei via associative LTP-like mechanism that strengthens the CS-amygdala synapses. BLA, basolateral complex of the amygdala; CEA, central nucleus of the amygdala; ITC, intercalated cells of the amygdala; PL, prelimbic cortex; IL, infralimbic cortex; HTP, hippocampus; Thal, thalamus; PAG, periaqueductal gray; PBN, parabrachial nucleus. Inhibitory pathways are represented by encircled minus symbols.