Interactions between sleep and sensory physiology.

The processing of sensory information is definitely present during sleep, however, profound modifications occur. All sensory systems reviewed (visual, auditory, vestibular, somesthetic and olfactory) demonstrate some influence on sleep and, at the same time, sensory systems undergo changes that depend on the sleep or waking state of the brain. Thus, different sensory modalities encoded by their specific receptors and pathways may not only alter the sleep and waking physiology, but also the sleeping brain imposes 'rules' on the incoming information. It is suggested that the neural networks responsible for sleep and waking control are actively modulated by sensory inputs in order to enter and maintain normal sleep and wakefulness. Furthermore, both sensory stimulation and deprivation may induce changes in sleep/waking neural networks. This leads to the conclusion that the central nervous system and sensory input have reciprocal interactions, on which normal/waking cycling and behaviour depends.