Figure 4. Two types of social buffering. In all paradigms, a rodent is fear-conditioned to auditory cues alone and then tested for recall 24 h later (see Kiyokawa et al., 2007). Recall in the solitary condition induces significant activation of CeA, LA, BA, and PAG, as indicated by red on the schematics of brain sections in the figure. Recall is also accompanied by activity in the HPA axis, SIH, and freezing behavior. In pair-housing, the rodent is housed with a conspecific for the 24 h between conditioning and recall. In this group, there is significant activation of the LA and PAG, but not of the BA and CeA. Although freezing behavior is still observed, there is reduced HPA activation and SIH. In pair exposure, the conditioned rodent is housed overnight in isolation but placed with a conspecific during recall. In this case, there is significant BA activation, and reduced HPA axis, CeA, and LA activity than when animals are housed and tested without conspecifics present. Freezing behavior is abolished in this condition, but SIH remains high. When a conspecific is present overnight as well as during testing, activation is reduced in all the aforementioned fear-associated regions, as well as a significant decrease in HPA axis activation, SIH, and freezing behavior.