Sleep, emotions, and visceral control

It is known that sleep is connected with sensory isolation of the brain, inactivation of the consciousness and reorganization of the electrical activity in all cerebral cortical areas. On the other hand, sleep deprivation leads to pathology in visceral organs and finally to the death of animals, while there are no obvious changes in the brain itself. It is still unclear how the changes in the brain activity during sleep could be connected with the visceral health. We assumed that the same brain areas and the same neurons that, in wakefulness, process exteroceptive information, switch, during sleep, to the processing of the interoceptive information. Thus, the central nervous system is involved in regulating the life support functions of the body during sleep. The results of our experiments supported this hypothesis, explained many observations obtained in somnology, and offered mechanisms of several pathological states connected with sleep. However, at the present level of the visceral sleep theory, there is no understanding of the well-known link between the emotional reactions of the body and transition from wakefulness to sleep, and sleep quality. In this study, an attempt is undertaken to combine the visceral theory of sleep with the need-informational theory of emotions proposed by P. Simonov. The visceral theory of sleep assumes that in living organisms there is a constant monitoring of the correspondence of the visceral parameters to the genetically determined values. Mismatch signals evoke the feeling of tiredness and the need of sleep. This sleep need enters the competition with other actual needs of the body. In accordance with the theory of Simonov, emotions connected with a particular need play an important role in their ranking for satisfaction. We propose that emotional estimation of the sleep need based on visceral signals occurs in the same brain structures which undertake this estimation for other behavioral needs in wakefulness. During sleep, the same brain structures involved in estimating emotions continue to rank visceral needs and define their order for processing in the cortical areas and in the highest centers of visceral integration. In the context of the proposed hypothesis, we discuss the results of the studies on the link between sleep and emotions.