The roles of the mPFC and BLA in acquisition and extinction of conditioned fear responses are well-characterized. While the prevailing model is that amygdala output generates fear responses and input from the PFC inhibits fear behavior (Maren and Quirk, 2004; Pape and Pare, 2010), this description is oversimplified. For example, silencing or disrupting plasticity in either structure impairs both acquisition and extinction of learned fear (Sierra-Mercado et al., 2011), suggesting that both the mPFC and BLA have roles to play in fear expression and suppression. Furthermore, a number of experiments have suggested that specific subregions within the mPFC might play opposing roles in the regulation of fear, with output from the prelimbic (PL) area facilitating fear and output from the infralimibic (IL) suppressing fear (Knapska et al., 2012; Sierra-Mercado et al., 2011; Vidal-Gonzalez et al., 2006). The dynamic interactions described here further add to this complexity; fear and safety can be seen as different modes of BLA-mPFC communication.
