In Figure 3 we showed that local BLA theta-BLA gamma coupling increases with CS+ presentation, arguing that local theta-gamma coupling is associated with fear. Yet here we present evidence of even stronger coupling of BLA gamma to mPFC theta, which was previously implicated in safety signaling (Likhtik et al., 2014). These findings suggested that mPFC and BLA theta might compete for control of the BLA fast gamma-generating circuit. According to this idea, during fear, local BLA theta modulates BLA gamma, reducing fast gamma power, while during safety, mPFC theta inputs predominate, increasing fast gamma power. To further test this hypothesis, we examined the relationship between BLA-mPFC theta directionality and gamma frequency changes in the BLA. To quantify directionality in the theta range, we calculated the cross-correlation between the theta power in the BLA and mPFC in short (1 s) time windows; the lag at the peak of this cross-correlation indicates predominant theta directionality (Supplementary Experimental Procedures; Adhikari et al., 2010a; Likhtik et al., 2014). We observed that on trials with a greater probability of mPFC theta lead, there was an
