(A) Density of Zif268 positive cells in the three experimental groups relative to paired controls (C—black line) in the CA1, CA3 and DG of the dorsal hippocampus, medial prefrontal cortex (PFC), lateral entorhinal cortex (LEC) and primary somatosensory cortex (SS1), after 10 days of training. All groups of rats expressed an increased density of Zif268 immunoreactive cells in these areas (except the control structure SS1) compared to control animals (n = 16, 100% baseline). This increase was not observed in the DG of HIWM rats (HIWM versus C: Mann–Whitney U-test, p = 0.1876, RM versus C: ** p = 0.0019, ** LIWM versus C: p = 0.004, HIWM versus LIWM: # p = 0.01, RM versus HIWM: ## p = 0.0065). * p < 0.05; **, ## p < 0.01; *** p < 0.001. Dots represent each animal in each group. (B) Representative photomicrographs showing Zif268-stained nuclei in the dorsal DG. Scale bar, 100 μm.