Spaced learning and the mechanisms that optimize memory formation

TINTORELLI, RAMIRO; BUDRIESI, PABLO; LOPES DA CUNHA PAMELA; CORREA JULIETA; VIOLA HAYDEE

Congreso; 33th Annual Meeting of Argentine Society of Neuroscience; 2018

Argentine Society of Neuroscience

The superiority of spaced learning over the massed one is a fundamental fact in the formation oflong-term memories (LTM). We studied the cellular processes and the temporal demands of thisphenomenon, using weak spatial object recognition (wSOR) and weak inhibitory avoidance (wIA)learning tasks. We observed SOR-LTM promotion when two identical wSOR, which individuallyinduced short-term memories but did not form LTM, were spaced by an inter trial interval (ITI)ranged between 15 min to 4 hr. The promoting effect was dependent on hippocampal proteinsynthesis and MAPKs activity. Also, two identical wIA training sessions spaced by 4 hr, promotedIA-LTM. In contrast, when we combined one wIA with a wSOR, neither of the two tasks formedLTMs.We discuss these results under the "behavioral tagging" hypothesis which postulate the existenceof a tag induced by learning that utilize proteins to form LTM. We suggest that the neural contactsstimulated by the first training session are re-tagged by retraining. Moreover, after retraining, theintracellular mechanisms triggered by both sessions could be added, reaching the threshold forprotein synthesis required for memory consolidation. On the other hand, when animals aretrained in two different and weak tasks, the processes triggered by them would not meet thespatial requirements necessary to form LTM.