Consolidation of memory during Slow Wave Sleep and implications in Rapid Eye Movement Sleep: a possible Neural Mass Model

There is strong evidence that this consolidation is due to the replay of memories during NREM sleep. Consolidation involves not only the reinforcement of learned information, but also generalization, conceptualization, and schema formation. It is known that the hippocampus encodes autobiographical-episodic memory, while semantic memory is localized in the cortex. Previous studies have demonstrated that episodic memories result to be more corticalized after sleep. Therefore, within corticalization, the representation generally migrates from the episodic representation in the hippocampus to the qualitative cortical representation. This work proposes a plausible mechanism for the corticalization and semantization of autobiographical sequential memories during NREM sleep. We implement a computational model based on NMM that simulates this consolidation mechanism during SWS. To do this, we use previous models to implement the episodic and the semantic network and we perform training during SWS-like conditions. Finally, we simulate REM sleep conditions to analyse the possible implications of this new connectivity pattern. After training, semantized representations can be retrieved independently of the hippocampus when multiple object-level cues are present. In contrast, REM sleep simulations – characterized by hippocampal disengagement, cortical theta modulation, and increased noise – produce fragmented and recombined memory patterns, consistent with dream-like associative and creative processes. The model reproduces key empirical findings on sleep-dependent abstraction and generates testable predictions about changes in cortical connectivity and cue-dependent retrieval after sleep. By relying solely on physiologically plausible Hebbian mechanisms and oscillatory dynamics, this framework provides a parsimonious account of how sleep promotes the transformation of episodic experience into a more semantized experience while preserving hippocampal specificity.