Figure 4

LTP modulation of Ketamine effects on HPC-PFC connectivity. Experimental design for LTP-SAL (A) and LTP-KET groups (E) (top) and representative fPSPs of baseline (left) and after HFS (right). (B) Effects of HFS (LTP-SAL group n = 15) on fPSPs (left and middle) and paired-pulse ratio (right) shown in 10 min blocks as mean ± standard errors. Data are presented as ratios from the baseline mean amplitude. Short-term potentiation (STP) corresponds to the transient decaying phase of LTP in the initial ~30 min. (C) PSDs of gamma frequencies before and after HFS, in the DEA (left) and ACT states (right). Bar plots display mean and standard errors of low (top) and high-gamma power (bottom). There is a significant increase in gamma power after HFS in the DEA states. No differences were found in the activated state. (D) Mean high-gamma amplitude as a function of delta phase before and after HFS (left). MI in deactivated state is not affected by LTP induction (right). (F) LTP induction precludes the ketamine enhancement of fPSPs and PPF (LTP-KET, n = 9). No statistical differences were observed between LTP and LTP-KET groups. (G) PSDs of gamma frequencies before and after Ketamine on LTP-KET group, in the deactivated (left) and activated states (right). There is a significant increase in high-gamma and a statistical trend in low-gamma power in the deactivated state (left). In the activated state, there is a significant increase in both low and high-gamma power (right). (H) Mean high-gamma amplitude as a function of delta phase before and after Ketamine in the LTP-KET group (left). MI in deactivated state is not affected in the LTP-KET group (right). *(p < 0.05), ~(p = 0.06).