CONSOLIDATION AND RECONSOLIDATION MECHANISMS SUPPORT UPDATING OF CONTEXT RECOGNITION MEMORY IN MICE
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Retrieval during ongoing learning provides a mechanism for integrating a new overlapping events or experiences into existing memories. How such integration takes place and impacts long-term retention of original memory remains poorly understood. Here, we used a new context recognition memory task in mice that provides a way to study memory-updating mechanisms and retroactive interference phenomenon, the most common cause of forgetting. The task is conducted in an operant chamber and involves spontaneous discrimination of novel from familiar nose-poke modules that are distinguishable by their visual feature and spatial location. In the acquisition session, mice are exposed for the first time to the testing chamber with one blinking nose-poke module. In the choice session, a novel non-blinking nose-poke module is inserted into an empty spatial location and the number of pokes in each set of nose-poke module is used as an index of recognition memory. We first verified that recognition performance varies as a function of the length of the acquisition period and the retention delay and is sensitive to conventional amnestic treatments. By manipulating the features of spatial context we show that introduction of new overlapping information during retrieval can impair subsequent recall of original memory and provide evidence that retroactive interference effects reflect a memory updating process that can occur either by a consolidation or a reconsolidation mechanism. We further show that both forms of memory updating do not overwrite previously stored information and that memory deficit may be due to retrieval failure.
