Dissociating encoding of memory and salience by manipulating long-term synaptic potentiation

Neural codes are thought to be reorganized during memory formation by long-term potentiation (LTP) of synapses. Here, using a novel approach for selectively blocking LTP, we found that eliminating LTP in hippocampal or striatal circuits only produces limited effects on learning and memory. To reconcile the discrepancy between the large physiological effect of blocking LTP and the absent effect on learning, we studied how LTP impacts neuronal computations in the hippocampus using in-vivo Ca2+-imaging. Contrary to current conceptual frameworks, we found that hippocampal CA1-region LTP is not required for accurate representations of space in hippocampal neurons, but rather endows these neurons with reward- and novelty-coding properties. Thus, instead of driving formation of cognitive maps and memory engrams, CA1-region LTP incorporates salience information into cognitive representations. One-Sentence SummaryA novel approach for studying long-term potentiation reveals its surprising and selective role in salience encoding