Abstract
The theory of memory reconsolidation argues that consolidated memory is not unchangeable. Once a memory is reactivated it may go back into an unstable state and need new protein synthesis to be consolidated again, which is called “memory reconsolidation”. Boundary studies have shown that interfering with reconsolidation through pharmacologic or behavioral intervention can lead to the updating of the initial memory, for example, erasing undesired memories. Behavioral procedures based on memory reconsolidation interference have been shown to be an effective way to inhibit fear memory relapse after extinction. However, the effectiveness of retrieval–extinction differs by subtle differences in the protocol of the reactivation session. This represents a challenge with regard to finding an optimal operational model to facilitate its clinical use for patients suffering from pathogenic memories such as those associated with post-traumatic stress disorder. Most of the laboratory models for fear learning have used a single conditioned stimulus (CS) paired with an unconditioned stimulus (US). This has simplified the real situation of traumatic events to an excessive degree, and thus, limits the clinical application of the findings based on these models. Here, we used a basic visual compound CS model as the CS to ascertain whether partial repetition of the compound CSs in conditioning can reactivate memory into reconsolidation. The results showed that the no retrieval group or the 1/3 ratio retrieval group failed to open the memory reconsolidation time window. The 2/3 repetition retrieval group and the whole repetition retrieval group were able to prevent fear reinstatement, whereas only a 2/3 ratio repetition of the initial compound CS as a reminder could inhibit spontaneous recovery. We inferred that a retrieval–extinction paradigm was also effective in a more complex model of fear if a sufficient prediction error (PE) could be generated in the reactivation period. In addition, in order to achieve an optimal effect, a CS of moderate discrepancy should be used as a reminder.
Highlights
Memory is not an exact copy but rather an adaptive presentation of a past experience
These results showed that participants acquired a conditioned fear to the conditioned stimulus (CS)+ but not to the CS−, and that the fear memory acquired by each group was of the same strength
No differences between other groups were detected. These results suggested that only the 2/3 repetition retrieval group had no spontaneous recovery of conditioned fear memories 24 h after post-retrieval extinction
Summary
Memory is not an exact copy but rather an adaptive presentation of a past experience. The acquired fear can be eliminated gradually if the conditioned stimulus (CS) is no longer followed by an unconditioned stimulus (US) such as electric shock, which is the principle of ‘‘exposure therapy’’. Fears extinguished successfully are prone to recover if the patient encounters the US after extinction (‘‘reinstatement’’), returned to the original context of conditioning (‘‘renewal’’), or as a result of the passage of time (‘‘spontaneous recovery’’; Bouton, 2002). The standard extinction forms a new inhibitory memory which competes with the acquired fear memory (Rothbaum and Davis, 2003; Jones and Monfils, 2016), the behavioral response to fear being the result of competition, which leaves the original fear memory intact. How to eliminate the acquired fear memory thoroughly and prevent relapse has been the focus of several scholars
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