To further explore the dynamics of the mPFC-BLA-vHPC circuit, we used the Granger causality index (GCI) to model potential causal influences using phase and power information. The GCI infers the strength of directional influences between LFPs by testing whether one LFP (e.g., from the mPFC) is useful in predicting the other (e.g., from the BLA), and vice versa. For fast gamma, we found significantly stronger Granger causality for the mPFC→BLA direction than the BLA→mPFC direction (Figure 7D; p <.05, sign-rank), suggesting that on average, fast gamma frequency activity in the mPFC tends to be predictive of future changes in the BLA. Granger causality similarly suggested predominant BLA→ vHPC and mPFC→vHPC directionality (p < 0.05, sign-rank), suggesting that gamma activity flows from the mPFC to the BLA and then to the vHPC (Figure 6F). Moreover, the mPFC->BLA Granger lead strength, which we defined for each animal as GCImPFC→BLA / (GCImPFC→BLA + GCIBLA→mPFC), was correlated with discrimination (Figure 6E, r=.50, p<.05), such that stronger evidence for an mPFC lead was present during the CS− compared to the CS+. These findings support a
