The hippocampus and the amygdala are two structures required for emotional memory. While the hippocampus encodes the contextual part of the memory, the amygdala processes its emotional valence. During Non-REM sleep, the hippocampus displays high frequency oscillations called “ripples”.
Our early work shows that the suppression of ripples during sleep impairs performance on a spatial task, underlying their crucial role in memory consolidation. We more recently showed that the joint amygdala-hippocampus activity linked to aversive learning is reinstated during the following Non-REM sleep epochs, specifically during ripples. This mechanism potentially sustains the consolidation of aversive associative memories during Non REM sleep.
On the other hand, REM sleep is associated with regular 8 Hz theta oscillations, and is believed to play a role in the regulation of emotional reactions and the consolidation of emotional memories. In particular, the activity of the amygdala during REM sleep is believe to be important for emotional regulation, but the underlying physiology is relatively unknown. Unraveling the fine neuronal dynamics related to REM sleep, Non-REM sleep and the transitions between states in the amygdala will further our understanding of the implication of these sleep stages and related brain patterns in emotional processing.
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