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Eur J Neurosci. 2006 Jul;24(2):606-16.

A context-specific single contingent-reinforcing stimulus boosts intermediate-term memory into long-term memory.

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Department of Physiology and Biophysics, Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1.


Following operant conditioning of aerial respiration in Lymnaea, memory forms. Depending on the training procedure either intermediate memory (ITM, < 3 h) or long-term memory (LTM, > 6 h) results. ITM is dependent on de novo protein synthesis whilst LTM is dependent on both transcription and de novo protein synthesis. LTM formation requires the soma of RPeD1 (one of the central pattern generator neurons) to be present. Following activation of a memory, it re-enters a labile state and undergoes a reconsolidation process to restabilize it. During reconsolidation, memory may be updated and/or changed. We add here another consequence of memory reactivation: a single contingent-reinforcing stimulus (SCRS), given in the same context as previous ITM training, boosts a residual memory trace to LTM. Separate cohorts of snails first received the ITM training procedure. In the cohort that received the SCRS 24 h after the last ITM training session, LTM was observed on the following day. LTM was not observed in cohorts that were: (i) given a single noncontingent stimulus; (ii) given the SCRS in a context other than the ITM training; (iii) given a 48-h gap between the last ITM training session and the context-specific SCRS; (iv) cooled immediately after the last ITM training session; (v) cooled immediately after the delivery of the context-specific SCRS; (vi) had the soma of RPeD1 ablated before the presentation of the context-specific SCRS; (vii) received a yoked control procedure. These data lead us to conclude that the context-specific SCRS reactivates a residual molecular memory trace in RPeD1 and boosts it into becoming the substrate for LTM.

[Indexed for MEDLINE]

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