In addition to ORM and OLM tasks, we examined long-term memory for contextual and cued fear conditioning in BAF53bΔHDlow and Baf53b+/− het mice. Both lines exhibited normal response to shock, as measured by pre- and post-shock velocity (Fig. 3A & 3D). BAF53bΔHDlow mice exhibited a significant decrease in freezing in a 24 hr retention test, indicating impaired long-term memory for contextual fear (Fig. 3B). In contrast, long-term memory for cued fear was normal in BAF53bΔHDlow mice as compared to wildtype littermates in a 24 hr retention test (Fig. 3C). Similar results were observed in Baf53b+/− het mice. Baf53b+/− het mice exhibited a significant decrease in freezing in the conditioned context in a 24 hr retention test, indicating impaired long-term memory for contextual fear (Fig. 3E). In contrast, long-term memory for cued fear was normal in Baf53b+/− het mice as compared to wildtype littermates in a 24 hr retention test (Fig. 3F). Together, these results suggest that BAF53b has a role in long-term memory for contextual fear, but perhaps not cued fear memory. Because contextual fear conditioning is hippocampus-dependent, whereas cued fear conditioning is hippocampus-independent, the results also suggest that the hippocampus may be more sensitive to alterations in BAF53b.
