Fig. 4: The CA3 region is susceptible to epileptiform activity in the ATR-deleted hippocampus.

a Deletion of ATR increases the amplitude of the preictal epileptiform discharges (PEDs). Example 30-second sections of 40-minute extracellular field potential recordings of PEDs in CA3. Zoom-in representative PEDs (0.5–5000 Hz) in population field activity band (PFA, 1–100 Hz) and fast ripple activity band (FRA, 200–500 Hz). b PEDs show higher instantaneous power in ATR-FBΔ (FBΔ) CA3 slices compared to controls (Ctr). Color-coded raster plots of the PED timing in all recorded slices. Colors represent the maximum instantaneous power of each PED in 1–100 Hz band. The slices are arranged in descending order, by the first slice having the highest number of detected PEDs. The slices containing PEDs with a power-level beyond 0.4 µV² (high-activity PEDs) are designated with a black square next to them. The ratio of slices with high-activity versus those with low-activity PED instantaneous power is increased after ATR deletion (right panel); Chi-square test (one-tailed), p = 0.012. c The instantaneous power of the whole field potential signal in 1–100 Hz band, computed within non-overlapping 1-min bins. The mean (solid line) ± SEM (shaded area). d Same as (c), but only for isolated PEDs (peak values) within 5-min bins. A one-tailed permutation test method of Cohen is used to compare the results of the two groups at each bin, with p < 0.05 (see Methods). e ATR-deletion leads to an increase in the power spectrum of PEDs over 1–100 Hz band. Power spectral density (PSD) of the PED events (solid lines), together with that of the baseline (i.e. non-PED epochs; dotted lines). f The summed baseline-normalized power presents an increase in the power of PEDs over 1–100 Hz shown in (e). Data presented as mean ± SEM. g ATR-deletion induces stronger fast ripples within PEDs. Same as (f), but for the fast ripple band (200–500 Hz). h Same as (f), but for the gamma band (30–90 Hz). i ATR-deletion increases the rate of spikes within PEDs, as detected in the multiple unit activity signal (MUA, > 500 Hz). Data are obtained from 16 slices of 4 control and 18 slices of 4 ATR-FBΔ mice and presented as mean ± SEM. Two-tailed t-test for (e–i): p = 0.026 for (e) and (f), p = 0.023 for (g), p = 0.027 for (h), and p = 0.016 for (i). *p < 0.05. Source data are provided as a Source Data file.