Figure 1

MK-801 induces state-dependent fear memory and enhances cortical delta oscillations. (a) Effect of different doses of MK-801 injected (i.p.) 30 min before fear conditioning on freezing (n = 8, 8, 9 mice, one-way ANOVA followed by Tukey’s test). (b) Effect of different doses of MK-801 injected (i.p.) 30 min before test on freezing (n = 7, 13, 9 mice, one-way ANOVA followed by Tukey’s test). (c) Effect of MK-801 injected (0.1 mg/kg) both before conditioning and before test on freezing (n = 8, 8 mice, unpaired t test). (d) Mice injected with vehicle/MK-801 before training only froze when tested under the same vehicle/MK-801 condition (n = 7, 9, 11 mice, two-way ANOVA followed by Sidak’s test). (e) Mice trained with MK-801 (0.1 mg/kg) showed robust freezing when tested with MK-801 (n = 11 mice, one-way ANOVA followed by Tukey’s test). (f) MK-801 when injected at the dose of 0.2 mg/kg impaired fear memory in mice (n = 7, 10, 13 mice, one-way ANOVA followed by Tukey’s test). (g) Mean speed measured without or with foot-shock after the injection of MK-801 (i.p.) at different doses (n = 18, 14, 7 mice, two-way ANOVA followed by Tukey’s test). (h) Representative raw traces of cortical LFPs under the basal (black) and the MK-801 (red) conditions. (i) One example of the temporal/spectral structures of cortical LFPs under the influence of MK-801 (0.1 mg/kg, i.p.). Black/red box (5 min) labels the signal used as baseline/MK-801 onboard in the following statistical analysis. (j) Average power spectrum of the baseline and the MK-801 onboard periods (n = 12 sites from 7 mice). Shadow areas indicate SEM. (k) Quantification of the average power of delta band (2–4 Hz) during the baseline and the MK-801 onboard periods (n = 12 sites from 7 mice, paired t test). (l) Illustration of MK-801 induced brain state transitions. ns: P > 0.05, *P < 0.05, **P < 0.01, ***P < 0.001, ^##P < 0.01. Veh., vehicle. MK, MK-801. Data presented as mean ± SEM.