Is autonomy working under unconscious state of sleep?

Conventionally sleep is understood as an unconscious state in which human and animals are taking rest physically as well as physiologically. However, sleep has been suggested to serve for development and maintenance of the higher-order brain functions as well. Actually neuronal activities show peculiar dynamics to sleep state and some neurons become rather active during sleep than wakefulness. Associated with neuronal activities, molecular and cellular machinery are found to be involved for the functions of sleep. Considering unconsciousness during sleep, neurobiological events characterizing sleep seem to be autonomously regulated. But, are they? In this essay, the neurobiological phenomena during sleep and their possible contribution to the sleep functions are reviewed. In addition, it is examined whether these neurobiological events during unconscious state of sleep are causally regulated or not.