Given that gamma couples strongly to theta oscillations, we reasoned that the observed mPFC-to-BLA gamma directionality is at least partly a result of safety-related directional theta information transfer from the mPFC to BLA (Likhtik et al., 2014). We therefore examined the relationship between gamma and theta activity within and across structures in the BLA-mPFC-vHPC network. Theta-gamma coupling was qualitatively similar in all three brain regions, with slow and fast gamma coupling to similar phases of theta (Figure 6A; n=23, BLA; n=17, vHPC; n=27, mPFC). We also found considerable theta-gamma coupling across structures (Figure 7B), consistent with a highly interconnected network. Intriguingly, fast gamma oscillations in the BLA had significantly stronger coupling to mPFC theta oscillations than to local BLA theta oscillations (p<.001, Figure 7B). By contrast, mPFC gamma oscillations were better modulated by local mPFC theta than BLA theta (p<.001; data not shown). We were concerned that strong mPFC theta-BLA fast gamma coupling could arise if the gamma recorded in the BLA was not locally generated. To address this caveat, we re-examined phase-locking of BLA multi-unit recordings to BLA fast
