DCN and Anxiety: The amygdala is a key brain structure for processing fear and anxiety, two core symptoms of PTSD.[33] Pavlovian fear conditioning test is a typical behavioral test used to assess exaggerated, dysfunctional fear and to investigate the neurobiological basis of PTSD.[34] Our results showed an increase in fear conditioning response after TBI, which is widely consistent with recent studies.[35, 36] Dcn knockout alleviated fear conditioning response caused by TBI, as observed upon chABC injection.