An Epigenetic Approach to Unlearning Old Fears in Animals

Fear extinction replaces a fearful association to a stimulus or context with a safe one, but the process needs to occur during reconsolidation when recent learning reactivates the fear memory. This process — the basis of exposure therapy for post-traumatic stress disorder (PTSD) — works better for recent than remote memories. These researchers accomplished context fear conditioning in mice by administering foot shocks in a particular cage. Extinction was attempted by repeatedly returning the mice to the cage without a shock on various schedules (18 minutes total spent in cage) beginning at 1 or 30 days after conditioning.

Fear extinction alone was successful at 1 day after conditioning but not at 30 days. However, pretreatment with a histone…