Dopamine controls whether new declarative information updates reactivated memories through reconsolidation

Consolidation and reconsolidation are independent memory processes. Consolidation stabilizes new memories, whereas reconsolidation restabilizes memories destabilized when reactivated during recall. However, the biological role of the destabilization/reconsolidation cycle is still unknown. It has been hypothesized that reconsolidation links new information with reactivated memories, but some reports suggest that new and old memories are associated through consolidation mechanisms instead. Object-recognition memory (ORM) serves to judge the familiarity of items and is essential for remembering previous events. We took advantage of the fact that ORM consolidation, destabilization, and reconsolidation can be pharmacologically dissociated to demonstrate that, depending on the activation state of hippocampal dopamine D1/D5 receptors, the memory of a novel object presented during recall of the memory of a familiar one can be formed via reconsolidation or consolidation, but only reconsolidation can link them. We also found that recognition memories formed through reconsolidation can be destabilized even if indirectly reactivated. Our results indicate that dopamine couples novelty detection with memory destabilization to determine whether a new recognition trace is associated with an active network and suggest that declarative reminders should be used with caution during reconsolidation-based psychotherapeutic interventions.

Destabilizing Different Strengths of Fear Memories Requires Different Degrees of Prediction Error During Retrieval

Reactivation of consolidated memories can induce a labile period, in which these reactivated memories might be susceptible to change and need reconsolidation. Prediction error (PE) has been recognized as a necessary boundary condition for memory destabilization. Moreover, memory strength is also widely accepted as an essential boundary condition to destabilize fear memory. This study investigated whether different strengths of conditioned fear memories require different degrees of PE during memory reactivation in order for the memories to become destabilized. Here, we assessed the fear-potentiated startle and skin conductance response, using the post-retrieval extinction procedure. A violation of expectancy (PE) was induced during retrieval to reactivate enhanced (unpredictable-shock) or ordinary (predictable-shock) fear memories that were established the day before. Results showed that a PE retrieval before extinction can prevent the return of predictable-shock fear memory but cannot prevent the return of unpredictable-shock fear memory, indicating that a single PE is insufficient to destabilize enhanced fear memory. Therefore, we further investigated whether increasing the degree of PE could destabilize enhanced fear memory using different retrieval strategies (multiple PE retrieval and unreinforced CS retrieval). We found that spontaneous recovery of enhanced fear memory was prevented in both retrieval strategies, but reinstatement was only prevented in the multiple PE retrieval group, suggesting that a larger amount of PE is needed to destabilize enhanced fear memory. The findings suggest that behavioral updating during destabilization requires PE, and the degree of PE needed to induce memory destabilization during memory retrieval depends on the strength of fear memory. The study indicates that memory reconsolidation inference can be used to destabilize stronger memories, and the findings shed lights on the treatment of posttraumatic stress disorders and anxiety disorders.

The Names of Local Heroes

This chapter emphasizes the significance of the war in rearranging relations between races at the local level. In a colonial spirit of “closing the frontier,” settlers living on or near Indian reservations appropriated Indian military participation. When raising funds for monuments or creating local heroes, whites invoked a brotherhood-in-arms and celebrated the true end of the Indian wars. Indians took advantage of their neighbors' willingness to include them in their celebrations and reactivated memories and heroes of the pre-reservation era. However, the war monuments that memorialized the dead Indian heroes on several reservations often did little else but list their names and dates of service. But their very existence resulted from a complex struggle in which tribes, bands, chiefs and chiefs' descendants, town notables, and white and Indian elites tried to appropriate for themselves the national legitimacy that military sacrifice carried.

Disruption of reconsolidation processes is a balancing act – can it really account for change in psychotherapy?

Lane et al. argue that any psychotherapeutic intervention at its core acts on reactivated memories via the process of reconsolidation which leads to modified memory traces. From our perspective, this model (1) only explains a small subsegment of psychotherapeutic mechanisms and (2) ignores the difficulties of generating reliable experimental conditions that allow interference with reconsolidation processes and – if successful – their transient nature.

Clinical applications of counterfactual thinking during memory reactivation

The Integrative Memory Model offers a strong foundation upon which to build successful strategies for clinical intervention. The next challenge is to figure out which cognitive strategies are more likely to bring about successful and beneficial modifications of reactivated memories during therapy. In this commentary we suggest that exercising emotional regulation during episodic counterfactual thinking is likely to be a successful therapeutic strategy to bring about beneficial memory modifications.