A long neural circuit spanning multiple brain regions is involved in context-induced retrieval of fear memory.

Individuals recovering from post-traumatic stress disorder (PTSD) often relapse due to context-induced fear memory retrieval when exposed to the same context in which they first experienced the trauma. Previous studies showed that both the ventral hippocampus CA1 (vCA1) and the dorsal hippocampus CA1 (dCA1) were involved in context-induced retrieval of fear memories. However, the causal relationship and the neural circuits between vCA1 and dCA1 during this process remain unknown. The present results show that vCA1 is an upstream brain region of the activation of dCA1; neural circuits from the vCA1 to the dCA1 via the lateral entorhinal cortex (LEC) mediate context-induced retrieval of fear memory; downstream neural circuits of dCA1 involve projections to the basolateral amygdala (BLA) via the postrhinal cortex (POR). These results suggest that a long neural circuit spanning multiple brain regions is involved in context-induced retrieval of fear memory.