[The neurology of REM sleep. A synoptic tour de force].

REM or dreaming sleep is one of three states of consciousness. It is characterized by rapid eye movements, muscle atonia, desynchronized EEG, and autonomic dysregulation. A dysfunction of one of these four cardinal traits explains the primary disorders of REM sleep, including REM sleep behavior disorder and narcolepsy. Although seen in other stages, sleep apnea syndrome, coronary syndromes, and stroke are strongly triggered by the autonomic dysregulation of REM sleep. REM sleep has an antiepileptic effect, which has not yet been used in clinical practice. It favors procedural memory, but not declarative memory. While present neurophysiologic theories, backed up by new neuroimaging techniques, preferentially explore the genesis of REM sleep, psychodynamic theories have searched for its raison d'être by focusing on mentally stabilizing or purifying effects of dreaming. The exploding interest in dreaming sleep, images, and imaging may also yield a harvest for clinical medicine, and further perplexing findings, such as RBD as harbinger of parkinsonism should be expected.