Two distinct projection pathways converge onto the same BLA neurons to contribute to fear memory retrieval.

Studying the neural circuits that mediate context-induced fear memory retrieval is of importance to develop new therapeutic approaches to prevent post-traumatic stress disorder relapse. The basolateral amygdala (BLA) is crucial for context-induced retrieval of fear memory. Previous studies indicate that projection neurons from the ventral hippocampus CA1 (vCA1) to the BLA (vCA1-BLA neurons) mediate context-induced retrieval of fear memory. However, it remains unclear whether other projection neurons to the BLA are involved in context-induced retrieval of fear memory and how they interact with vCA1-BLA neurons. Our findings indicate that the postrhinal cortex (POR) to the BLA (POR-BLA) neurons are also involved in context-induced retrieval of fear memory. These neurons innervate the same BLA neurons as vCA1-BLA neurons and participate in fear memory retrieval. These results suggest that two different projection neurons of POR-BLA and vCA1-BLA innervate on the same BLA neurons and POR-BLA neurons and vCA1-BLA neuron contribute to fear memory retrieval. These findings provide new insights into the neural mechanisms underlying fear memory retrieval.