Fig. 2.

Impaired hippocampus-dependent cognition in Ccnd2^−/− mice. Responses to tone CS⁺ and training context 24–30 h following aversive conditioning. (A) Conditioned behavioral freezing to the tone CS⁺ presented in a novel context (arrows indicate CS⁺ presentation). Both Ccnd2^+/+ (blue line) and Ccnd2^−/− (red line) mice show minimal baseline freezing (<300 s) and robust conditioned freezing to the first tone CS⁺ (t₁₆ = 1.3, P > 0.25; n = 9 per genotype). On subsequent tone CS⁺ presentations, Ccnd2^−/− mice show less posttone freezing, a hippocampus-dependent behavior. (B) Average posttone freezing in the novel context (t_15.8 = 2.3, P < 0.05). (C) Ccnd2^−/− mice show reduced context-conditioned freezing (t₁₆ = 2.3, P < 0.05). The mixed repeated measures ANOVA showed a significant effect of genotype (F_1,16 = 14.4, P < 0.01). Box plot parameters are described in Fig. 1. *P < 0.05, planned comparisons with independent t tests.