It is unclear which circuit level changes mediate these shifts in network dynamics, though recent work has provided data on how communication from the mPFC to the BLA is altered after extinction training. Cho et al. (2013) showed that extinction altered feed-forward excitatory-inhibitory balance for mPFC inputs to the BLA reducing mPFC-evoked EPSPs in pyramidal cells but preserving excitatory drive onto BLA interneurons. Thus, the mPFC recruits local circuit interneurons, including intercalated cells (Amano et al., 2010), to mediate fear reduction during extinction (Likhtik et al., 2008). This is consistent with data from safety learning, where a safety-associated CS evoked a decreased lateral amygdala LFP response while a fear-associated CS evoked an enhanced LFP response (Rogan et al., 2005). These findings are consistent with the proposed model which suggests that a fast gamma-generating neuronal circuit, modulated by mPFC input, is engaged during relative safety, suppressing fear. The finding that extinction induces remodeling of perisomatic inhibitory synapses from parvalbumin positive (PV+) interneurons onto pyramidal cells in the amygdala (Trouche et al., 2013) raises the intriguing possibility that this interneuron subtype may
