How sleep helps to process emotions
Researchers at the Department of Neurology of the University of Bern and University Hospital Bern identified how the brain triages emotions during dream sleep to consolidate the storage of positive emotions while dampening the consolidation of negative ones. The work expands the importance of sleep in mental health and opens new ways of therapeutic strategies.

Rapid eye movement (REM or paradoxical) sleep is a unique and mysterious sleep state during which most of the dreams occur together with intense emotional contents. How and why these emotions are reactivated is unclear. The prefrontal cortex integrates many of these emotions during wakefulness but appears paradoxically quiescent during REM sleep. Processing emotions, particularly distinguishing between danger and safety, is critical for the survival of animals. In humans, excessively negative emotions, such as fear reactions and states of anxiety, lead to pathological states like Post-Traumatic Stress Disorders (PTSD). In Europe, roughly 15% of the population is affected by persistent anxiety and severe mental illness.

This decoupling is important because the strong activity of the dendrites allows the encoding of both danger and safety emotions, while the inhibitions of the soma completely block the output of the circuit during REM sleep. In other words, the brain favours the discrimination of safety versus danger in the dendrites, but block the over-reaction to emotion, in particular danger.