Non-linear susceptibility to interferences in declarative memory formation

Abstract

After encoding, memories go through a labile state followed by a stabilizationprocess known as consolidation. Once consolidated they can enter a new labile stateafter the presentation of a reminder of the original memory, followed by a period of restabilization (reconsolidation). During these periods of lability the memory traces canbe modified. Currently, there are studies that show a rapid stabilization after 30 min,while others show that stabilization occurs after longer periods (e.g. 6 h). Here weinvestigate the effect of an interference treatment on declarative memoryconsolidation, comparing distinct time intervals after acquisition. On day 1, participantslearned a list of non- syllable pairs (List 1). Immediately after, 30 min, 3 h or 8 h later,they received an interference list (List 2) that acted as an amnesic agent. On day 2(48 h after training) participants had to recall List 1 first, followed by List 2. We foundthat the List 1 memory was susceptible to interference when the List 2 wasadministered immediately or 3 h after learning; however, shortly after acquisition (e.g.30 min) the List 1 memory becomes transiently protected against interference. Wepropose the possibility that this rapid memory protection could be induced by a fastand transient neocortical integration (where the memory is transiently protected)becoming partially independent from the hippocampus followed by a hippocampal reengagement where the memory becomes susceptible to interferences again. Ourresults open a discussion about the contribution of molecular and systemic aspects tomemory consolidation.