Process consolidating memories

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Based on this, I would like to argue that the reconsolidation phenomenon reflects a fragile state of a memory that has not yet been fully consolidated, although it has passed the initial protein synthesis-dependent phase.Thus, as detailed below, I propose that reconsolidation is a phase of the overall consolidation process [] found that in chicks intracerebral administration of the protein synthesis inhibitor cycloheximide 5 min before a passive avoidance reminder procedure, which was performed 2, 24, or 48 h after training, resulted in temporary amnesia that gradually decreased in duration as the interval between training and reminding increased.We recently confirmed these results using bilateral amygdala injections of either the protein synthesis inhibitor anysomycin or antisense DNA sequences specific for the transcription factor CCAAT enhancer binding protein β (C/EBPβ) (; Milekic et al., unpublished).We conclude that upon reactivation, an older memory does not become fragile to the same degree as a young one does, and that, over time, memory becomes increasingly stable and insensitive to the postreactivation interference.Events able to disrupt a reactivated memory are the same as those found to be effective in disrupting consolidation including treatments that inhibit molecular mechanisms or protein synthesis in general.The process by which a labile memory again becomes stable and therefore insensitive to disruption has been termed , reminiscent of the labile phase of the posttraining consolidation process.Similar infusions into the anterior cingulate cortex had no effect on either recent or remote contextual fear memories, whereas systemically applied anisomycin blocked remote memory expression only when long reexposure durations were used to retrieve the memory.The dissociation between the effects of systemically and centrally administered anisomycin on remote memory led the authors to suggest that memory stability is due, in part, to the distributed nature of remote contextual fear memory traces.

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The classical view proposes that memory consolidation is a unitary process through which a newly formed memory, which is initially sensitive to disruption, becomes stable over time; once stabilized, the memory remains insensitive to disruption.

Studies from my laboratory, as well as those of several others, have pointed out that the passage of time is a limiting factor for the postretrieval vulnerability of memory.

Using the fear-conditioning-based task inhibitory avoidance, we have found that systemic inhibition of protein synthesis resulted in decrementally graded amnesia of 2-day- and 1-week-old memories while leaving intact 2-week- and 4-week-old memories [].

Additional corroboration of the same phenomenon was provided by Suzuki et al.

[] who, using systemic anisomycin injections in mice at time points covering an 8-week temporal window after training, elegantly showed that contextual fear conditioning displays a gradient of postreactivation fragility.

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