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. Author manuscript; available in PMC: 2012 Jul 1.
Published in final edited form as: Neurobiol Learn Mem. 2010 Dec 30;96(1):2–12. doi: 10.1016/j.nlm.2010.12.008

Figure 2.

Figure 2

Unique targets and timelines for DNA methylation/demethylation in the hippocampus and cortex. a, Sagittal section of rat brain representing methylation changes occurring at CpG islands in the promoter regions of selected genes in response to contextual fear conditioning. Both DNA methylation and demethylation are observed at different genes and even within the same gene. Brain section graphic taken from (Paxinos and Watson, 2005). b, Temporal dynamics of DNA methylation changes in response to contextual fear conditioning. Although all of the changes observed in the hippocampus return to basal levels within 24 hours of learning, at least one change (increased calcineurin methylation) is maintained within the dorsomedial PFC. Importantly, blocking DNA methylation in the hippocampus immediately after conditioning disrupts memory consolidation. In contrast, inhibiting DNA methylation in the dmPFC immediately after learning has no effect on retrieval of remote memories 30 days later, but blocking DNA methylation several days immediately prior to remote retrieval significantly impairs performance, indicating a necessity for ongoing DNA methylation in the maintenance of fear memories (Miller et al., 2010).