Fig. 8

Fmr1^−/y CA1 pyramidal neurons are less phase locked to gamma oscillations than WT neurons. A Representative firing phase distribution of a single principal neuron along a theta cycle. Same for slow gamma oscillations (D) and medium gamma oscillations (G). B Average Mean Vector Length (MVL), quantifying the strength of phase locking to theta oscillations across the six recording sessions. MVL decreased significantly in cells of both genotypes across sessions within a day (session-in-day effect p = 0.026), but there were no differences between genotypes or days (p’s > 0.05). C The proportion of significantly phase-locked (Rayleigh p < 0.05) pyramidal neurons to theta oscillations across six recording sessions. There were no differences between genotypes, and no genotype x session interaction (p’s > 0.05). However, there is a significant main effect of session (Log-likelihood ratio: session effect p = 0.029), with theta phase locking higher in sessions 1 and 3 compared to sessions 5 and 6 (two proportion z-test, session 1 vs session 5 ^#p < 0.01; session 1 vs session 6 ^#p < 0.01; session 2 vs session 5 ^#p < 0.05; session 2 vs session 6 ^#p < 0.01) E WT neurons exhibit higher MVLs (stronger phase locking) to slow gamma compared to Fmr1^−/y neurons (LME: main effect of genotype *p = 0.022), with no significant differences between days or sessions within a day (p’s > 0.05). Further tests indicate significant differences between genotypes only in sessions 1 and 3 (Tukey post hoc, session 1 ⁺p < 0.001; session 3 ⁺p = 0.02). F A higher proportion of WT pyramidal neurons is significantly phase locked to slow gamma oscillations compared to Fmr1^−/y neurons (Log-likelihood ratio: genotype effect p = 0.035) and sessions different between one another (Log-likelihood ratio: session effect p < 0.001). While there was no significant genotype x session interaction (Log-likelihood ratio: genotype x session p = 0.053), the proportion of slow gamma phase locked neurons was higher in WT that rats in Sessions 1 and 3 of Day 1, but not for any other session (two proportion z-test, WT vs Fmr1^−/y Session 1: ⁺p < 0.001; Session 3: ⁺p = 0.023) a significantly higher proportion of WT neurons were phase-locked in session 1 than any other session (two proportion z-test WT, session 1 vs session 2 ^#p < 0.001; session 1 vs session 3 ^#p = 0.014; session 1 vs session 4 ^#p < 0.001; session 1 vs session 5 ^#p < 0.001; session 1 vs session 6 ^#p < 0.001). H There were no significant differences in MVL with respect to medium gamma between genotypes, days or sessions within a day (LME all p’s > 0.05). I However, a significantly higher proportion of WT than Fmr1^−/y neurons was significantly phase locked to medium gamma oscillations (Log-likelihood ratio: genotype effect p = 0.013). N_WT-D1 = 222, N_WT-D2 = 207, N_KO-D1 = 211, N_KO-D2 = 205. Pale yellow and pale purple backgrounds denote data from Day 1 and Day 2, respectively