It has long been assumed that initially labile memory traces are transformed into relatively permanent ones by a time-dependent stabilization process called memory consolidation (Mc Gaugh 2000). It is assumed that memories in this state need to be reconsolidated or they will be lost.The permanence of consolidated traces has been called into question by studies showing that memories can become labile for some time after reactivation (e.g., Misanin et al. It is possible that in this transient plastic state, memories are also open to modification. Forty-eight hours later (session 2), subjects were either reminded of the first session or not and immediately afterward learned a second set of objects.Consistent with this view, reconsolidation effects have been demonstrated in a variety of animal protocols and also in human procedural memory (Walker et al. On the assumption that reconsolidation underlies the malleability of memory, we recently asked whether reactivation is involved in the updating of human episodic memory (Hupbach et al. Again 48 h later (session 3), subjects were asked to recall the first set only, that is, the objects learned in session 1.Reminded subjects showed a high number of intrusions from set 2 when recalling set 1 in session 3, while subjects who had not been reminded showed almost no intrusions, demonstrating that the updating of pre-existing memory is dependent on reactivation of that memory.Despite the different reminders that were implemented in session 2, all other aspects of the experimental procedure were identical to our previous study.
The dynamic nature of memory is probably not a design flaw; it can allow us to update existing knowledge in light of new information.A total of 36 undergraduate students from the University of Arizona participated in the experiment. Twelve subjects were randomly assigned to each condition.