The space in between Sleep, memories and dreams

This dissertation investigates the role of sleep and brain oscillations in memory consolidation and consciousness, by leveraging experiments performed in both rats and humans.
Here, we expanded the model-based closed-loop neurostimulation method to precisely forecast specific phases of theta (4 - 8 Hz) oscillations during REM sleep. We also tested this method's reliability when applied to other frequency bands from human encephalography recordings, as well as hippocampal local field potentials of rats. This method was then employed to perform target memory reactivation (TMR) by re-exposing participants to previously learned aversive sound cues, phase-locked to REM sleep theta oscillations. Our findings indicate that targeted interventions can influence the emotional tone of memories.
Furthermore, we characterized the shifts in functional connectivity across sleep stages in rats. We recorded single-neuron activity of cortical and subcortical regions (primary auditory cortex, medial pre-frontal cortex, hippocampus, basolateral amygdala), which we related to expected consciousness levels. Moreover, the presented dissertation also ponders about the function of dreams and its provided insights into consciousness and memory processing during sleep.
This thesis enhances our understanding of sleep, brain rhythms, memory, and consciousness, contributing to cognitive neuroscience and sleep research and suggesting avenues for memory enhancement and addressing sleep-related cognitive disorders.