Spatial reversal training increasesArc expression in hippocampus and entorhinal cortex. Rats were trained in one of three spatial water tasks (for behavioral data, see Fig. 4) and were killed 30 min later. The experimental groups included caged, first session, seventh session, and seventh session-reversal (n = 6 rats per group). IEG RNA levels for the dorsal hippocampus (A), lateral entorhinal cortex (B), and primary visual cortex (C) were determined by RPA. IEG RNA levels for all water task-trained groups were significantly above caged control levels for each brain region (p < 0.02; Mann–Whitney U test). See Results section for additional details and statistical comparisons. n = 6 rats per group.