Emotional memory Consolidation and Homeostatic regulation during REM sleep: a translational approach – ECHoR

Sleep and emotional functions are tightly linked. Sleep benefits both emotional memory consolidation and emotional regulation. These two aspects of emotional processing are key to the survival of an individual, ensuring the retrieval of emotional memories and appropriate responses to threatening or rewarding information. The mechanisms that underlie emotional processing in sleep, however, are still unclear. Reactivation of waking experiences during sleep has been found to support memory functions, and may similarly underlie emotional consolidation and emotional regulation. Moreover, rapid-eye-movement (REM) sleep has emerged as a promising candidate state to support emotional functions: it benefits emotional memory consolidation, aids the regulation of emotional responses, and is disrupted in emotional disorders. While the neural dynamics of memory reactivation have been extensively studied in non-REM sleep, little is known about information processing during REM sleep and its role in emotional processing.
The overarching goal of this proposal is to determine the role of REM sleep for emotional memory consolidation and emotional regulation. We are proposing an innovative, translational approach with parallel experiments in humans (M. Schonauer) and rats (G. Girardeau) along two aims. First, we hypothesize that the valence of a previous learning experience is processed during REM sleep, supporting the consolidation of emotional memories. We will test whether we can detect and quantify reactivation of negative or positive experiences during REM sleep in core structures of the emotional memory network using novel machine learning methods (Aim 1). Further, we expect that emotional regulation is linked to homeostatic neural processes occurring during REM sleep, which could co-occur or compete with memory consolidation. We will record and selectively perturb activity in structures involved in emotional processing during REM sleep to test how this influences emotional responses at the behavioral and physiological levels (Aim 2). To do so, we will record EEG and fMRI in humans while they are exposed to positive, neutral, and aversive stimuli and during subsequent sleep periods. In rats, we will combine in vivo large-scale electrophysiological recordings in the amygdala, hippocampus, and prefrontal cortex with optogenetic manipulations during positive and aversive spatial tasks and sleep.
Disturbed sleep and dysfunctional memory processes have been linked to the development and maintenance of most psychiatric disorders, including post-traumatic stress disorder. Our project will significantly further our understanding of memory and emotional regulation during sleep. This is crucial to develop a coherent model of emotional functioning, and, in the long-term, tailor new treatments and interventions targeted at sleep.