Episodic memory is akin to a mosaic assembled from different pieces of past experiences: the affective state, the context and participants of the event as well as sensory details. Episodic memories are far from flawless copies of the actual experiences, but rather reconstructions thereof. We hypothesize that reconstruction is based on representations in sensory and semantic systems and that the hippocampus in the medial temporal lobe is critical for episodic memory because it performs integration of higher-order representations. We therefore study, on the one hand, how episodic memories are stored and retrieved in interaction with the sensory and semantic systems. On the other hand, we investigate how episodic memories influence these sensory and semantic systems. In particular, we have been able to show that episodic memory is more accurate when perceptual-semantic representations are better tuned to the statistics of the input. In the other direction, we found that replaying perceptual information from previous experiences in episodic memory facilitates the optimization of perceptual-semantic representations. Furthermore, we investigate how to dissociate the effect of sensory processing from that of memory operations in cognitive tasks such as recognition memory and visual discrimination.
Improving sensory representations using episodic memory