Phase-locking of single unit activity to LFP theta <i>across</i> regions.

<p>(A) Summary of phase-locking analysis during freezing states in R1 and non-freezing states in E. Each identified unit in CA1 (upper), LA (middle), and IL-PFC (bottom) was assigned a LFP theta phase recorded simultaneously in the other two brain areas (grey, blue, green diagrams indicating LFP in CA1, LA, IL-PFC, respectively). Plotted are mean time shifts between unit activity and the LFP theta phase calculated from MRLs in each area. Note the significant lead of unit activity in IL-PFC related to the LFP theta in CA1 and LA during non-freezing in E (highlighted by red lines). (B) Mean MRL of all identified theta phase-locked IL-PFC units during freezing in R1 and non-freezing in E related to LFP theta oscillations recorded simultaneously in CA1 (upper diagram) and LA (lower diagram). Note the peak MRL (indicated by red arrows) signaling a lead of unit activity in IL-PFC related to LFP theta in CA1 and LA during non-freezing in E. (C) Schematic representation of phase-locking of single unit activity to LFP theta across regions, during freezing at R1 and non-freezing at E. Black lines with two arrowheads indicate high theta synchrony (with no significant time lead or lag), red lines indicate theta directionality. Values are mean±SEM; asterisks indicate the significance level revealed by Wilcoxon Signed Rank test : *,p<0.05. MRL, mean resultant length vector; f, freezing; nf, non-freezing.