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Repeated labilization-reconsolidation processes strengthen declarative memory in Humans
Congreso; Society For Neuroscience; 2011
It is generally recognized by cognitive psychology that memory is reconstructive in essence at retrieval. It is also clear that memories are not constant through time showing variations not only in content but also in strength. Conversely, in the neurobiological field understanding of learning and memory is quite different. The consolidation hypothesis assumes that memories are labile during a time window after acquisition but, as time passes, memories become stable and unalterable. However, this vision of immutable memories has been challenged. Several reports have shown that after the presentation of a specific reminder, reactivated old memories become labile and again susceptible to amnesic agents. Such vulnerability diminishes with the progress of time and implies a restabilization phase, usually referred to as reconsolidation. To date, the mechanisms associated with the labilization-reconsolidation process are accurately described, but little is known about its functionality from a biological standpoint. Indeed, two functions have been proposed.One suggests that destabilization of the original memory after the reminder allows the integration of new information into the background of the original memory (memory updating), and the other suggests that the labilization-reconsolidation process strengthens the original memory (memory strengthening). Our laboratory reported reconsolidation of human memories related to facts and episodes that are accessible to conscious recollection. We demonstrated updating in the framework of memory declarative reconsolidation by giving an opportune verbal instruction. Here we deal with the strengthening function attributed to the reconsolidation process. We triggered labilization-reconsolidation processes successively by repeated presentations of the proper reminder. Participants learned an association between five cue-syllables and their respectiveresponse-syllables. Twenty-four hours later, the paired-associate verbal memory was labilized by exposing the subjects to one, two or four reminders. The List-memory was evaluated on Day 3 showing that the memory was improved when at least a second reminder was presented in the time window of the first labilization-reconsolidation process prompted by the earlier reminder. However, the improvement effect was revealed on Day 3 only when at least two reminders were presented on Day2 and not as a consequence of only retrieval. Therefore, for the strengthening function this study delineates central concepts for the reconsolidation process, emphasizing its biological role and the parametrical constrains for this function to be operative.