Letter to the editor: hypothesis for the neurophysiology of dreaming

During wakefulness, the cerebral cortex, which is responsible for generating mental activities, is activated by brain stem ascending influences. This is evidenced by classic electrophysiological field and unitary activities, gamma range activity and cortical blood flow. However, aminergic ascending neurons exert mainly diffuse inhibitory influences. These two kinds of influences together support reflective and rational psychological activities. During slow wave sleep, both kinds of ascending influences decrease and the mental content comprises low-intensity thought-like activities, similar to the waking mode of functioning, although dreams have been described. During rapid eye movement sleep, the principal dreaming stage, the cortex is activated but significantly disinhibited since all aminergic neurons are silent except the dopaminergic ones. We hypothesize that, in addition to this unusual state, the persistent release of dopamine associated with the specific silence of noradrenergic neurons could explain the characteristics of dream mental activity which are somewhat similar to psychotic symptoms.