Fig. 1: In vivo electrophysiological recordings during context exposure, fear extinction, and extinction retrieval.

A Illustration and representative traces of mPFC and HPC local field potential recordings (LFPs). B Behavioral timeline of the fear conditioning protocol. Representative photomicrographs show mPFC (C) and HPC (D) electrode placements. Similar photomicrographs were taken to confirm electrode placement for all animals. E Averaged freezing behavior (n = 6; 3 male and 3 female) during fear conditioning, context exposure, extinction, and extinction retrieval (BL = baseline). F Average freezing during fear retrieval during the first five trials of extinction (Fear) was greater than context exposure (Expo; p = 0.044, repeated measures one-way ANOVA with Tukey’s multiple comparison test) and the five extinction retrieval trials (Ext; p = 0.024). G, H, K Normalized spectral power of theta-range oscillations in the prelimbic (PL) and infralimbic (IL) cortex and the HPC during 10 s CS presentations across days. I Normalized 3–6 Hz power was elevated during Fear recall in the PL relative to Exposure (p < 0.0001) and Extinction (p < 0.0001). This was also observed in the IL (p < 0.0001; p < 0.0001) and HPC (p = 0.048; p = 0.006). L Conversely, 6–9 Hz power was decreased during Fear recall in the PL relative to Exposure (p = 0.0305) and Extinction (p < 0.002). This was likewise observed in the IL (p = 0.0109; p = 0.0092). J, M Linear regression of freezing vs IL theta-range power during Expo, Fear and Ext. N Cartoon illustrating synchronous theta oscillations. O Example coherogram depicting high mPFC-HPC theta coherence during extinction retrieval. P Average peak coherence of 6–9 Hz oscillations between the PL and HPC was highest during extinction retrieval, compared to exposure (p = 0.002) and fear retrieval (p = 0.008). IL-HPC coherence was also greater during extinction retrieval relative to context exposure (p = 0.005). BL baseline, CS conditioned stimulus, PL prelimbic cortex, IL infralimbic cortex, HPC hippocampus. Line plots represent mean ± s.e.m.s; boxplots represent mean plus minima and maxima with lower and upper quantiles. *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001. Source data are provided as a Source Data file.