Noradrenaline involvement in basic and higher integrated REM sleep processes

There has been an abundance of literature devoted to the involvement of noradrenaline in basic rapid eye movement (REM) sleep processes since the subject was first investigated in 1964. Nowadays, the great majority of studies highlight the need for silence in the locus coeruleus noradrenergic neurons as a condition for the occurrence and maintenance of REM sleep. However, throughout the successive years of work on this topic, few researchers have consistently claimed that some amount of noradrenaline is essential for the appearance of this sleep stage. In the first part of this review, each of the papers published in this field is analyzed. Then, in the discussion, arguments supporting the requirement for a given level of noradrenaline for REM sleep occurrence are presented. This second part also examines, based on waking noradrenergic influences on higher integrated brain processes, the major consequences of noradrenergic neuron silence during REM sleep for mental functioning.