Participation of the rostral anterior cingulate cortex in defensive behavior induced by electrical stimulation of the dorsal periaqueductal gray and contextual fear conditioning

The rostral anterior cingulate cortex (rACC) is a critical brain structure related to defensive behavior. However, still unclear is whether the rACC also plays a role in defensive behavior induced by electrical stimulation of the dorsal periaqueductal gray (dPAG). In the present study, rats were implanted with electrodes into the dPAG to determine freezing and escape response thresholds after sham or bilateral electrolytic lesions of the rACC. The duration of freezing behavior that outlasted electrical stimulation of the dPAG was also measured. The next day, these animals were subjected to contextual fear conditioning using footshock as an unconditioned stimulus. Lesions of the rACC did not change aversive freezing and escape response thresholds but disrupted post-dPAG stimulation freezing. The lesions also disrupted defensive freezing behavior and analgesia in the formalin test in response to contextual cues previously associated with footshock. These results indicate that the rACC is involved in some but not all aspects of defensive behavior generated at the level of the dPAG. The rACC also appears to play an important role in contextual fear conditioning.