Retrieval as a Fast Route to Memory Consolidation

Abstract

Retrieval-mediated learning is a powerful way to make memories last, but its neurocognitive mechanisms remain unclear. We propose that retrieval acts as a rapid consolidation event, supporting the creation of adaptive hippocampal-neocortical representations via the 'online' reactivation of associative information. We describe parallels between online retrieval and offline consolidation and offer testable predictions for future research.

Keywords: consolidation; episodic memory; long-term memory; reactivation; replay; retrieval-mediated learning; sleep; testing effect.

Figure 1. Neural network changes via retrieval compared to restudy

Imagine you form a new memory of leaving your phone in a taxicab. Also imagine that two weeks prior to this episode, you needed a taxi because you had a very heavy suitcase with you. The two episodes have distinct, non-overlapping representations in hippocampus (HC) but are connected via the shared element “taxi” in neocortex (NC). NC also holds representations of memories that are loosely connected with phones and suitcases, respectively. Retrieval of the taxi-phone episode will activate the core representations in HC and NC, but it will also cause co-activation of related information including the suitcase, and knowledge related to phones. Strongly active memories and their connections (blue elements) will be strengthened, supporting memory integration. Moderately co-activated information will be weakened, supporting differentiation, while no change in connection strength occurs for weakly active memories. In comparison, restudy re-instantiates the cortical representations only of those elements that are explicitly presented; connections between these elements will be strengthened, but the memory will not be integrated with or differentiated from other stored knowledge.