Figure 1. En2−/− mice show impaired spatial learning in the MWM test. A, Escape latency during training. B, Proximity to platform in target and opposite quadrants during probe trial. C, Number of crossings in target and opposite quadrants during probe trial. D, Time spent in target and opposite quadrants during probe trial. WT, Open circles; En2−/−, black squares; T, target quadrant; OP, quadrant opposite to target. *p < 0.05, **p < 0.01, and ***p < 0.001 (one-way ANOVA followed by Holm–Sidak post hoc test; n = 11 per genotype). E, Representative in situ hybridization on WT and En2−/− hippocampi and quantification of Arc mRNA signal in the CA1 and CA3 pyramidal cell layers (*p < 0.05, **p < 0.01; Student's t test, WT vs En2−/−; n = 3 per genotype). Scale bar, 200 μm.