Novelty induces the formation of long-term memories

M. C. MARTÍNEZ; F. BALLARINI; N. ALEN; D. MONCADA; H. VIOLA

Washington, DC, ESTADOS UNIDOS

Congreso; Neuroscience Meeting Planner; 2008

Society for Neuroscience

In recent experiments using memory paradigms in rats, we have demonstrated the existence of behavioral tagging, a behavioral analog of synaptic tagging, which has been extensively studied in long-term potentiation models. By this mechanism, the learning of an inhibitory avoidance task that normally induces short-term memory (STM), but not a long lasting one (LTM), can be stabilized into a LTM by the recruitment of the proteins derived from another behavioral experience (in our case, the exploration of a novel open field). The hypothesis postulates that learning induces a transient mark or tag that allows the local recognition of newly synthesized proteins to produce an enduring change in transmission efficiency. In order to occur the behavioral tagging, there must be temporal convergence of the events triggered by both tasks in a common neuronal population.With the aim of validating the behavioral tag hypothesis, we decided to study this phenomenon using different behavioral paradigms. Therefore, we evaluated the effect of the exploration of an open field (OF) on the learning of two other tasks which also depend on hippocampal processing: Spatial Object Recognition (SOR) and Contextual Fear Conditioning (CFC).Our results show that STM of SOR or CFC training protocols, which cannot induce LTM by themselves, can be consolidated into LTM by the exploration to a novel OF, when this one is applied in a specific time window. In contrast, in all cases, the effect is abolished when the OF is familiar.Furthermore, when OF is combined with a weak protocol of Conditioned Taste Aversion, a task processed in the insular cortex, there is no LTM, indicating that it is fundamental the anatomical coincidence of both tasks so that tagged synapses can capture proteins.In summary, these results provide further evidence that support the hypothesis of behavioral tagging.