Prefrontal and Auditory Input to Intercalated Neurons of the Amygdala

•Lateral intercalated neurons receive auditory input from both cortex and thalamus•Auditory input to medial ITC neurons is strong from thalamus but weak from cortex•Prefrontal IL inputs innervate BLA principal neurons but not medial ITC neurons•Excitation of medial ITC neurons from the IL is disynaptic via the basolateral amygdala

SummaryThe basolateral amygdala (BLA) and prefrontal cortex (PFC) are partners in fear learning and extinction. Intercalated (ITC) cells are inhibitory neurons that surround the BLA. Lateral ITC (lITC) neurons provide feed-forward inhibition to BLA principal neurons, whereas medial ITC (mITC) neurons form an inhibitory interface between the BLA and central amygdala (CeA). Notably, infralimbic prefrontal (IL) input to mITC neurons is thought to play a key role in fear extinction. Here, using targeted optogenetic stimulation, we show that lITC neurons receive auditory input from cortical and thalamic regions. IL inputs innervate principal neurons in the BLA but not mITC neurons. These results suggest that (1) these neurons may play a more central role in fear learning as both lITCs and mITCs receive auditory input and that (2) mITC neurons cannot be driven directly by the IL, and their role in fear extinction is likely mediated via the BLA.

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