Dynamic Switching Of The Connectivity In Default Mode Network Of Rats Under Sleep Deprivation

As an important part of life,sleep is thought to be associated with physical and psychological health.Usually,the total sleep cycle could be divided into two different states,such as the rapid eye movement(REM)sleep state and the non-rapid eye movement(NREM)sleep state.It has been showed that these two states could characterize different levels of consciousness during sleep.However,how the underlying mechanism on the switching within these two states is still unclear.As one of the most important brain resting state network,the default mode network(DMN)is considered to be closely related to the levels of consciousness.And sleep deprivation has been proven to cause abnormal changes in DMN connectivity.Therefore,DMN-based sleep research of rats under sleep deprivation might provide new insights into the deep understanding for the mechanism on the sleep state switching.In this thesis,we employed the multilayer network analysis measurement to investigate the dynamic changes of functional connectivity in rat DMN during the switching of sleep states systematically.To explore the role of sleep state switching in sleep disorders,we separately explore the dynamcs of DMN connectivity under normal sleep and different sleep deprivations.Our main results are as follows:1.Under normal sleep,the basic state mode of the brain before the sleep state switching is mainly dominanted by four modules,which are composed of anterior DMN areas,hippocampus,temporal lobe,and posterior DMN areas.After the sleep switching,the state mode of the brain is changed to be dominated by three modules,consisting of anterior DMN areas,temporal lobe,and hippocampus connected with posterior DMN areas.During the process of sleep state transition,both the reconstruction of several REM state-related functional moduls,including those between hippocampus and posterior DMN acreas and those between temporal lobe and anterior DMN acreas,and the enhancement in connectivity between the hippocampus and the temporal lobe represent a high level of functional integration,making the brain enters a high level of awareness.2.The total sleep deprivation mainly affects the brain area which is state-related before the sleep state switching.Decreased information interaction between the orbitofrontal lobe and other DMN regions could be observed,inferring that total sleep deprivation might negatively affect the emotional and behavioral responses of rats.Moreover,the information exchange between the hippocampus and the posterior brain area before conversion increased during the total sleep deprivation,suggesting that the level of consciousness improve compared to normal sleep.After the conversion,the total sleep deprivation causes the weakened functional connection of the medial prefrontal cortex,which indicates the reduced ability of the brain to process information.3.The REM sleep deprivation mainly affects the activity of DMN core areas after the sleep state transition.DMN activity in those areas tend to migrate from posterior to anterior,making the anterior DMN area more susceptible to network noise to change its original stable module.The alteration of stable module implys that the cognitive function may be impaired during REM sleep deprivation.Besides,the effect of REM sleep deprivation before sleep state transition is reflected in the reduced incidence of functional modes dominated by NREM,which confirming REM and NREM phase interaction mechanism that REM sleep pressure will inhibit NREM phase activity.In summary,our current work employs the multi-layer network analysis to describe the effect of sleep deprivation on the dynamic changes of the DMN connectivity during the sleep state transition from the DMN brain area level,function module level and function mode level.Our results reveal that the dynamic activities of the hippocampus and the temporal lobe promote the improvement of consciousness.The main abnormal changes caused by total sleep deprivation and REM sleep deprivation on DMN connectivity are separately reflected before and after the transition of sleep state.Our research provides new ideas and directions for the study of sleep mechanism,thus has important scientific significance and medical application value.