Memory reactivation effects independent of reconsolidation

Abstract

Memory reactivation is an important process resulting from reexposure to salient training-related information whereby a memory is brought from an inactive to an active state. Reactivation is the first stage of memory retrieval but can result from the exposure to salient cues without any behavioral output. Such cue-induced reactivation, although frequently used by neuroscientists to study reconsolidation, has seldom been considered as a process in its own right and studied as such. This review presents arguments indicating that memory reactivation has two main consequences: (1) to enhance the accessibility of the target memory and (2) to make the memory malleable. Accordingly, reactivation creates a transient state during which the content of the memory is easily accessible and can be modified and/or updated. As both of these aspects can be observed shortly after memory reactivation, this review emphasizes that reconsolidation is not necessarily required for these processes and calls attention to reactivation as a factor in the dynamics of the memory.Memory retrieval is a complex (multistage) process through which previously acquired information can be used, leading to a behavioral output. Memory reactivation is the first component of retrieval corresponding to the process through which a memory is triggered from a latent state to a state in which it can be retrieved. Reactivation is generated by cues that are either external or self-generated and occurs in two general conditions. First, reactivation is required for retrieval and for every operation that enlarges or modifies previous knowledge. This includes retraining, when coherent supplementary information is provided, extinction when the previously learned response is no longer reinforced, and more generally, all rule-shiftings, i.e., when the contingency governing the response is changed. As a result, reactivation is largely embedded with retrieval and this probably explains why these two terms are often used interchangeably in the literature.

Characterization of spatial memory reconsolidation

“…6B). This raises the idea that reactivation may render the initial memory trace malleable to allow the introduction of new information (Lee 2009;Gisquet-Verrier and Riccio 2012). As a consequence, the reconsolidation in the CA3 region would be necessary again to restabilize this trace after the recall, including the update of the original memory (Nader and Einarsson 2010).…”

Only susceptible rats exposed to a model of PTSD exhibit reactivity to trauma-related cues and other symptoms: An effect abolished by a single amphetamine injection

“…Recently, we provided evidence indicating that when reactivated, memories are malleable, to allow introduction of new information such as new context within a reactivated memory [57]. We propose that reactivating traumatic memories, while the patient is placed in a positive mood, could induce the integration of this positive mood within the traumatic memory, rendering it less traumatic than it was initially.…”

A BDNF sensitive mechanism is involved in the fear memory resulting from the interaction between stress and the retrieval of an established trace

“…As previously noted (Dudai 2002;Hardt et al 2010), retrieval is not a passive readout of prior experiences, rather retrieval can turn memory in a transient plasticity enabling dynamic modifications of the established memory trace (Sara 2000;Nader 2003;Duvarci and Nader 2004;Dudai 2006;Lee 2009); however, it should be noted that retrieval does not always lead to a reconsolidation process (Gisquet-Verrier and Riccio 2012). Under certain circumstances, for instance, new information can be updated into the original trace and its strength can be significantly modified (Lee 2008(Lee , 2010Rodriguez-Ortiz et al 2008;Hupbach et al 2009).…”