Experience alters hippocampal and cortical network communication via a KIBRA-dependent mechanism

Abstract

Synaptic plasticity is hypothesized to underlie "replay" of salient experience during hippocampal sharp-wave/ripple (SWR)-based ensemble activity and to facilitate systems-level memory consolidation coordinated by SWRs and cortical sleep spindles. It remains unclear how molecular changes at synapses contribute to experience-induced modification of network function. The synaptic protein KIBRA regulates plasticity and memory. To determine the impact of KIBRA-regulated plasticity on circuit dynamics, we recorded in vivo neural activity from wild-type (WT) mice and littermates lacking KIBRA and examined circuit function before, during, and after novel experience. In WT mice, experience altered population activity and oscillatory dynamics in a manner consistent with incorporation of new information content in replay and enhanced hippocampal-cortical communication. While baseline SWR features were normal in KIBRA conditional knockout (cKO) mice, experience-dependent alterations in SWRs were absent. Furthermore, intra-hippocampal and hippocampal-cortical communication during SWRs was disrupted following KIBRA deletion. These results indicate molecular mechanisms that underlie network-level adaptations to experience.

Keywords: CP: Neuroscience; KIBRA; anterior cingulate cortex; hippocampus; place cell; plasticity; sharp-wave ripple; sleep spindle.

Figure 1.. KIBRA cKO mice show normal baseline hippocampal area CA1 circuit dynamics

(A) Timeline for experiments. (B–D) Total distance traveled (B: WT, 89.8 ± 7; cKO, 82.4 ± 4), total time spent moving ≥3 cm/s (C: WT, 20.7 ± 1 min; cKO, 19.5 ± 0.9 min), and mean velocity (D: WT, 3.8 ± 0.3; cKO, 3.4 ± 0.1) during behavior sessions. (E and F) Baseline power spectral density from pre-experience home cage during active periods (E: velocity>3 cm/s for at least 2.5 s) and immobility periods (F: velocity <1 cm/s for 3–60 s). (G–I) Mean theta band (6–12 Hz) oscillatory power (G: WT, 106.5 ± 7; cKO, 99.9 ± 8), mean theta frequency (H: WT, 8.71 ± 0.12 Hz; cKO, 8.75 ± 0.06 Hz), and peak theta frequency (I: WT, 9.16 ± 0.10 Hz; cKO, 9.01 ± 0.10 Hz) during active periods in the pre-experience home cage. (J and K) Low-gamma-band (J: 25–50 Hz; WT, 68.5 ± 4; cKO, 65.8 ± 6) and high-gamma-band (K: 65–140 Hz; WT, 46.1 ± 2; cKO, 48.4 ± 4) oscillatory power for WT and KIBRA cKO mice during active periods in the pre-experience home cage session. (L) Theta phase/low-gamma-amplitude cross-frequency coupling (phase/amplitude coupling [PAC]). Left: theta phase vs. normalized gamma amplitude (20° bins). Right: PAC measure (modulation index [MI]: WT, 0.0106 ± 0.0005; cKO, 0.0114 ± 0.0006). (M) Theta-phase/high-gamma-amplitude coupling (MI: WT, 0.0118 ± 0.0007; cKO, 0.0126 ± 0.0005). (N) Example of raw and ripple-filtered traces depicting detected SWRs in WT (top) and cKO (bottom) mice. Scale bars: 100 ms, 200 μV; same scale for WT and cKO traces. (O) Pre-experience SWR rate by detection threshold (standard deviations above the mean; WT, 2 SD 0.76 ± 0.02, 3 SD 0.57 ± 0.02, 4 SD 0.43 ± 0.01, 5 SD 0.31 ± 0.01, 6 SD 0.22 ± 0.01, 7 SD 0.14 ± 0.01; cKO, 2 SD 0.76 ± 0.05, 3 SD 0.53 ± 0.05, 4 SD 0.38 ± 0.05, 5 SD 0.26 ± −0.04, 6 SD 17 ± 0.03, 7 SD 0.1 ± 0.02). (P) Ripple-band power spectrograms averaged across all detected SWRs for WT (top) or cKO (bottom) mice, scale bar indicates Z-scored power. (Q–S) Baseline ripple properties during pre-experience home cage immobility using detection threshold of 5 SDs above mean SWR power; SWR rate (Q: WT, 0.24 ± 0.01; cKO, 0.22 ± 0.01 events/s immobile), mean duration of SWR events (R: WT, 0.13 ± 0.004; cKO, 0.13 ± 0.006 s), and peak SWR power (S: WT, 7.15 ± 0.19; cKO, 6.96 ± 0.16). Data values reported are mean ± SEM. Statistics: unpaired Mann-Whitney rank-sum test (B) or unpaired t test (C and D, G–M, Q–S). Two-group test for equal spectra (E and F). Multiple Mann-Whitney rank-sum test with Holm-Šidák correction (O). All comparisons were not significant (WT vs. cKO, p > 0.1). n = 8 (cKO)/10 (WT) mice.

Figure 2.. Experience-dependent modulation of CA1 SWR properties is impaired in KIBRA cKO mice, while modulation of ripple abundance is intact

(A) Pre- and post-experience SWR abundance shown in 5-min segments for a representative WT (gray, top) and cKO (purple, bottom) mouse. (B) SWR rate (events/s during immobility) in pre- and post-experience home cage sessions (main effect of experience p < 0.0001, pre vs. post WT p < 0.0001, pre vs. post cKO p < 0.0001; WT, pre 0.24 ± 0.01, post 0.37 ± 0.02; cKO, pre 0.22 ± 0.01, post 0.33 ± 0.02). (C) Example trace showing experience-dependent increases in SWR power and duration in WT but not cKO mice. Scale bar: 100 ms, 200 mV. (D) Peak SWR power during pre- and post-experience home cage sessions (main effect of experience p = 0.0284, pre vs. post WT p = 0.0168, pre vs. post cKO p = 0.8335; WT, pre 0.13 ± 0.004, post 0.14 ± 0.005; cKO, pre 0.13 ± 0.006, post 0.13 ± 0.004). (E) SWR duration during pre- and post-experience home cage sessions (main effect of experience p = 0.0279, experience × genotype p = .0656, pre vs. post WT p = 0.0091, pre vs. post cKO p = 0.9476; WT, pre 7.15 ± 0.19, post 7.55 ± 0.19; cKO, pre 6.96 ± 0.16, post 7.04 ± 0.19). Data values reported are mean ± SEM. Statistics: two-way repeated measures (RM) ANOVA with Šidák’s multiple comparisons. ****p < 0.0001, ***p < 0.001, **p < 0.01, *p < 0.05. n = 8 (cKO)/10 (WT) mice per group. See also Figures S3–S5.

Figure 3.. Experience-dependent increase SWR-associated low gamma power is impaired in KIBRA cKO mice

(A and B) Transient increase in low gamma power during SWR events recorded from area CA1 in pre- and post-experience home cage for (A) WT and (B) cKO mice. Low gamma power was averaged across 100-ms bins within 450 ms of SWR onset (data plotted at bin center and normalized to −450- to −350-ms bin for each SWR). (C) Time-frequency spectrograms showing experience modulation of SWR-associated low gamma power in WT (top) and cKO (bottom) mice, scale bar to right indicates Z-scored power. (D) Low gamma power at peak ripple power during SWR (main effect of experience p < 0.0001; experience × genotype interaction p = 0.0095; pre WT vs. cKO p = 0.9916; post WT vs. cKO p = 0.0469; WT, pre 1.00 ± 0.07, post 1.61 ± 0.06, pre vs. post p < 0.0001; cKO, pre 0.99 ± 0.09, post 1.29 ± 0.15, pre vs. post p = 0.0018). Data values reported are mean ± SEM. Statistics: twoway RM ANOVA with Šidák’s multiple comparisons (D). *p < 0.05. n = 8 (cKO)/10 (WT) mice per group.

Figure 4.. Loss of KIBRA impairs awake CA1 SWR properties during novel experience

(A) Z-scored peak ripple power (p = 0.0377, WT, 7.17 ± 0.29; cKO, 6.33 ± 0.16). (B and C) (B) SWR rate (p = 0.0769, WT, 0.15 ± 0.04; cKO, 0.07 ± 0.02) and (C) SWR duration (p = 0.6240, WT, 0.13 ± 0.005; cKO, 0.13 ± 0.006) for SWRs with 3-SD threshold that occurred in periods of immobility during a novel experience. (D) SWR-associated increase in low gamma power. (E) Low gamma power at peak ripple power (p = 0.9420, WT, 1.08 ± 0.15; cKO, 1.10 ± 0.15). Data values reported are mean ± SEM. Statistics: unpaired t test (A–C and E), *p < 0.05. cKO n = 7 mice (A and C–E), n = 8 mice (B, note that one mouse had no SWRs during novel experience, so the SWR rate of 0 was included in B, but excluded from all other analyses in this figure); WT n = 10 mice. See also Figure S3.

Figure 5.. KIBRA is required for experience-induced increase in hippocampal pyramidal cell participation in SWRs

(A) Example place fields for five cells each from WT and KIBRA cKO mice. Arena dimensions 40 × 60 cm. Heatmap scale bar, 0 to maximum firing rate, where the maximum firing rate (Hz) for each cell is indicated in the top right corner. (B) Mean firing rate during exploration of a novel environment for each cell with an identified place field (WT, 0.98 ± 0.22 Hz; cKO, 1.04 ± 0.18 Hz; WT vs. cKO p = 0.5336). (C) Mean in-field firing rate during active exploration (WT, 2.34 ± 0.30 Hz; cKO, 1.72 ± 0.23 Hz; WT vs. cKO p = 0.0595). (D) Maximum in-field firing rate during active exploration (WT, 4.94 ± 0.66 Hz; cKO, 3.52 ± 0.42 Hz; WT vs. cKO p = 0.0410). (E) Number of place fields per cell in novel environment shown in (A) (WT, 1.70 ± 0.22; cKO, 1.74 ± 0.19; WT vs. cKO p = 0.9091). (F) Mean place-field size for each cell (WT, 420.2 ± 105.5 cm²; cKO, 689.2 ± 87.0 cm²; WT vs. cKO p = 0.0351). (G) Information (bits) per spike for each WT and KIBRA cKO cell with identified place field(s) (WT, 2.05 ± 0.22; cKO, 1.46 ± 0.20; WT vs. cKO p = 0.0416). (H) Average participating cell firing rate during pre-experience SWRs (WT, 12.14 ± 0.69 Hz; cKO, 12.44 ± 0.68 Hz; WT vs. cKO p = 0.9463). (I) Experience modulation of firing rate in SWRs (for each cell, firing rate in post-experience SWRs/firing rate in pre-experience SWRs. WT, 2.54 ± 0.54; cKO, 1.30 ± 0.14; WT vs. cKO p = 0.0043. One-sample Wilcoxon test vs. 1; WT, p = 0.0002; cKO p = 0.0635). (J) Experience modulation of cell participation in SWRs (fraction of SWRs in which a cell fired at least one action potential, post-/pre-experience. WT, 2.24 ± 0.45; cKO, 1.17 ± 0.10; WT vs. cKO p = 0.0010 One-sample Wilcoxon test vs. 1, WT p < 0.0001, cKO p = 0.1663). (B–G) WT, 20 cells from six mice; cKO, 31 cells from five mice; cells with peak firing rate <1 Hz were excluded from these analyses. (H–J) WT, 24 cells from six mice; cKO, 36 cells from five mice. Note that consistent results were observed when analyses in (I) and (J) were restricted to neurons with place fields (experience modulation of firing rate in SWRs: WT = 2.52 ± 0.63, cKO = 1.35 ± 0.16, WT vs. cKO p = 0.0153. Experience modulation of cell participation in SWRs: WT = 2.14 ± 0.47, cKO = 1.19 ± 0.11, WT vs. cKO p = 0.0029). Statistics: Mann-Whitney rank sum (B–J) and one-sample Wilcoxon (I and J).

Figure 6.. Loss of KIBRA impairs CA3-CA1 communication and experience modulation of CA3 ripple and low gamma power during SWRS

(A) Baseline CA3 low gamma power in pre-experience rest (p = 0.3185; WT, 60.0 ± 3; cKO, 47.6 ± 10). (B) Experience modulation of peak CA3 low gamma power during identified CA1 SWRs, shown as ratio of post/pre experience (p = 0.0411; WT, 1.71 ± 0.17; cKO, 1.10 ± 0.18). (C) Experience modulation of peak CA3 ripple power during CA1 SWRs shown as ratio of post/pre experience (p = 0.0428; WT, 1.22 ± 0.06; cKO, 0.91 ± 0.13). (D) Probability normalizied polar histogram (10° bins) showing distribution of CA3-CA1 low-gamma-phase offsets in SWRs during pre- (left) and post-experience (right) home cage sessions for all WT (gray) and KO (purple) SWRs. To combine phase-offset distributions across animals, normalized data from each mouse were rotated to set the peak phase offset bin to 0 (Rayleigh test for uniformity: WT and KO, pre and post p < 0.0001. Kuiper’s two-sample test: WT vs. KO distribution, pre p = 0.004, post p = 0.002). (E and F) Across both pre- and post-experience sessions, mean CA3-CA1 phase coherence (ISPC) across SWRs (E: WT = 0.50 ± 0.26, cKO = 0.23 ± 0.06, p = 0.0457) and within SWRs (F: WT = 0.55 ± 0.11, cKO = 0.47 ± 0.02, p = 0.0381). Statistics: unpaired t test (A–C and E), with Welch’s correction (A and E). Mann-Whitney rank-sum test (F). Rayleigh test for uniformity, Kuiper two-sample test with Bonferroni-Holm corrections for multiple comparisons (D). WT n = 6, cKO n = 4 mice (A–C, E, and F). (D) n = # ripples. WT: pre (n = 3,894), post (n = 7,432). cKO: pre (n = 2,262), post (n = 3,002). See also Figures S6 and S7.

Figure 7.. Coordination of ACC spindles and CA1 SWRs during sleep is disrupted by loss of KIBRA

(A) Example of a spindle event detected in the ACC. Top: raw LFP during spindle event. Middle: sigma-filtered trace (10–15 Hz). Bottom: root-mean-square (RMS) transformed trace used for spindle detection (black) and thresholds used to define occurrence, onset, and offset (red). Scale bars: raw LFP 500 μV, sigma filtered 200 μV, transformed 1 × 10⁶ μV³. (B) ACC sigma power in pre-experience home cage sessions during all immobility periods (p = 0.1416; WT, 47.4 ± 3; cKO, 50.1 ± 1). (C–E) Pre-experience baseline properties of identified spindles: (C) Rate (spindle events per second; WT vs. cKO, p = 0.1571; WT, 0.11 ± 0.01; cKO, 0.09 ± 0.01); (D) mean spindle duration (WT vs. cKO, p = 0.6135; WT, 1.81 ± 0.06; cKO, 1.85 ± 0.05); (E) Peak sigma power during spindles (WT vs. cKO, p = 0.8865; WT, 4.47 ± 0.07; cKO, 4.58 ± 0.19). (F–H) Experience modulation of ACC spindles: (F) spindle rate (main effect of experience p = 0.0002; WT pre vs. post p = 0.0009; cKO pre vs. post p = 0.0453; WT, pre 0.11 ± 0.01, post 0.13 ± 0.01; cKO, pre 0.09 ± 0.01, post 0.10 ± 0.01); (G) spindle duration (main effect of experience p = 0.0631; WT pre vs. post p = 0.0343, cKO pre vs. post p = 0.9676; WT, pre 1.81 ± 0.06, post 2.00 ± 0.08; cKO, 1.85 ± 0.05, post 1.87 ± 0.07); (H) peak sigma power across all spindles (WT pre vs. post p = 0.9729; cKO pre vs. post p = 0.6787; WT, pre 4.47 ± 0.07, post 4.45 ± 0.06; cKO, pre 4.58 ± 0.19, post 4.50 ± 0.09). (I) Peak ACC sigma power for spindles co-occurring with CA1 SWRs (main effect of experience, p = 0.0002; experience × genotype, p = 0.0376; WT pre vs. post p = 0.0002, cKO pre vs. post p = 0.1250; WT, pre 1.23 ± 0.10, post 1.47 ± 0.09; cKO, pre 1.12 ± 0.04, post 1.22 ± 0.07). (J and K) Probability distribution for absolute lag between CA1 SWRs and ACC spindle onset during putative NREM sleep for WT (J) and cKO (K): pre vs. post, WT p < 0.0001, cKO p = 0.1063. (L) Percentage of SWR events occurring within 2 s of a spindle during post-experience rest (WT vs. KO, p = 0.0217; WT, 0.49 ± 0.03; cKO, 0.36 ± 0.04). (M) Proportion of ACC spindles that co-occur with CA1 ripples (main effect of experience, p = 0.0007; WT pre vs. post p = 0.0013, cKO pre vs. post p = 0.1694; WT, pre 0.20 ± 0.02, post 0.26 ± 0.02; cKO, pre 0.16 ± 0.01, post 0.19 ± 0.03). (N) Peak ripple power of SWRs nested within spindles (experience × genotype, p = 0.0308; WT pre vs. post p = 0.0408, cKO pre vs. post p = 0.6521; WT, pre 6.96 ± 0.11, post 7.32 ± 0.06; cKO, pre 7.07 ± 0.24, post 6.94 ± 0.17). (O) Fraction of spindles containing more than one nested SWR (# spindles containing >1 SWR/# spindles containing ≥1 SWRs; main effect of experience, p = 0.0425; experience × genotype, p = 0.0684; main effect of genotype, p = 0.0964; WT pre vs. post p = 0.0168, cKO pre vs. post p = 0.9806; WT, pre 0.40 ± 0.04, post 0.48 ± 0.03; cKO, pre 0.35 ± 0.03, post 0.35 ± 0.04). Data values reported are mean ± SEM. Statistics: unpaired t test (C, D, and L). Mann-Whitney rank-sum test (B and E). Two-way RM ANOVA with Šidák’s multiple comparisons (F–H, I, and M–O), Wilcoxon rank-sum test on distributions with Bonferroni-Holm correction for multiple comparisons (J and K). n = 8 (WT)/n = 7 (KO) mice per group (B–I and L–O). n = # ripples in J and K;WT, pre (n = 3,969) post (n = 5,262); cKO, pre (n = 3,352) post (n = 4,555). ****p < 0.0001,***p < 0.001,**p < 0.01,*p < 0.05.