Asynchronous development of sleep - a plausible cause of cognitive impairment and a number of pathological conditions related to sleep-wake cycle
The article gives a review to several theories of sleep. According to them, sleep is regarded as a period of recovery of effective brain functioning after active wakefulness. Several studies have demonstrated the association between decreased cognition and increased sleepiness. According to the alternative hypothesis, cognitive impairment is explained by shutdown of certain cortical zones due to their local sleep rather than by impaired brain performance. The studies of asynchronous development of sleep in the cortical zones are described. Causes and conditions for the development of local sleep are discussed in the framework of authirs’ visceral theory of sleep. The theory is based upon an assumption that, during sleep, central parts of the nervous system shift from the analysis of external information to the analysis of internal (visceral) signals. Hypothetical switching network diagram of the main information pathways in the sleep-wake cycle is presented. The authors emphasize that asynchronous switching may explain the development of the number of the sleep-wake cycle-associated pathological conditions (i.e. waking hallucinations, sleep starts, dreams/anxiety dreams, sleepwaking and sleep paralysis). This theory may predict emergence of‘visceral hallucinations’ which are regarded as a potential cause of seasickness, motion-sickness and some other psychosomatic disorders.