Fig. 4. Task-specific gamma synchrony between entorhinal cortex and hippocampus.

(A) Learning-induced changes for MEC-DG and LEC-DG LFP-LFP gamma WPLI in the spatial and object learning tasks, respectively. Mean ± SEM WPLI (learning − baseline)/(learning + baseline) (n = 12/12 sessions in 4/4 rats for MEC and LEC, respectively). LFP traces were taken from the DG molecular layer and EC layer 2. Red and blue lines indicate frequencies with a significant effect (P < 0.05 with Bonferroni correction for multiple comparisons). In the spatial task, DG WPLI increased more with MEC than with LEC in the gamma_F band (P = 4.8 × 10⁻⁶, rank-sum test), whereas in the object task it increased more with LEC than MEC in the gamma_S band (P = 9.0 × 10⁻⁵). (B) Spike-LFP coupling (PPC) between spikes of layer II MEC and DG gamma LFP and LEC LII excitatory neurons and DG gamma LFP during spatial or object learning, respectively (n = 192/95 MEC cells in the spatial and object tasks and n = 72/128 LEC cells, from four rats in each case). In the spatial task, DG spikes’ PPC increased more with MEC gamm_F LFP than with LEC (P = 3.8 × 10⁻³, rank-sum test), whereas in the object task, it increased more with gamma_S LEC LFPs than with MEC (P = 1.4 × 10⁻⁴). (C) Learning-induced power change for DG LEC gamma_S and MEC gamma_F oscillations in the two tasks (P = 6.3 × 10⁻⁷/0.0033 gamma_S versus gamma_F, signed-rank test, n = 36/24 sessions in the spatial and objects tasks from 12 rats). In (A) to (C), **P < 0.01, ***P < 0.001, signed-rank test for learning versus baseline effect in the gamma_S or gamma_F bands. (D) Schema summarizing the spatiotemporal organization of LEC and MEC gamma inputs to the DG.