Based on these findings, along with results from a number of studies demonstrating enhanced theta-frequency synchrony during fear-related behavior (Lesting et al., 2011, Seidenbecher et. al., 2003, Popa et. al., 2010, Likhtik et al, 2014), we propose the following conceptual model (Figure S8). During fear, a threat-related theta signal strongly and reciprocally synchronizes BLA and mPFC, coordinating local gamma activity within each structure and leading to strong local theta/gamma coupling during the CS+. During safety, theta frequency inputs from the mPFC to the BLA predominate, suppressing the fear response via the BLA fast gamma circuit. The CS− is therefore characterized by strong, directional thetatheta synchrony from the mPFC to the BLA (Likhtik et al., 2014) and strong modulation of BLA gamma by mPFC theta (reported here). Because mPFC theta activity drives gamma generators locally in the mPFC and distally in the BLA, the CS− is also associated with strong mPFC-BLA gamma synchrony. This long-range gamma synchrony is predominantly directional from the mPFC to the BLA, either because the mPFC theta drives mPFC gamma with a shorter delay than BLA gamma,
