Impact Of Sleep Deprivation On Neuronal Avalanche Of Rat Default Mode Network

As a naturally recurring state of mind and body,sleep is considered as an intrinsic part of human life.Revealing the underlying mechanism of brain during sleep cycle has been more and more popular which could help deepen our understanding on sleep.It has been reported that in the brain there exists several resting-state networks(RSNs)which are constituted of simultaneously activated brain regions at rest.As a fundamental RSN,the default mode network(DMN)has received much more attention due to its high level of activity during resting state and unique performance for cognitive tasks.Several studies have shown that the DMN is critical for the compensatory process after sleep deprivation(SD).However,the neurodynamic mechanism of sleep compensation still remains unclear.In the present dissertation,we addressed this issue by recording the electrophysiological(EEG)signals from 10 rats.All the rats would firstly perform the short-term(4 hours)rapid eye movement sleep deprivation(REM-SD)experiment,and then suffered the short-term(4 hours)total sleep deprivation(Total-SD)experiment after two days' recovery.For each SD experiment,we continued to record EEG signals during the whole SD duration and 6 hours after SD.The data after SD was employed as the signals for recovery periods.We analyzed the self-organized criticality,the type of neuronal avalanche and the coding mode of sleep dependence from the data in the recovery periods to characterize the neurodynamic features of compensatory responses after different types of SD.Our main findings are summarized as follows:1.The results of self-organized criticality analysis showed that the distribution of neuronal avalanche during REM state is in accord with the power law distribution,exhibiting a similar self-organized critical state with the awake state.However,the distribution of neuronal avalanche during SWS state tended to be a kind of exponential distribution,indicating that the SWS state might be a sub-critical state.In comparison with the REM state,the SWS state usually occurs during the deep sleep stage of sleep cycle and can be characterized with high amplitude,low frequency and weak invariance in both temporal and spatial scales,thus preferentially presenting subcritical avalanche dynamics.2.With avalanche type analysis,we manifested that DMN activity might take thesignificant avalanche as its basic unit due to the high proportion of these avalanches in all avalanches for all states in our study.After both types of SD,the features of significant avalanches during the 6th hour of the recovery period had greater variability than those of the 1st hour.Meanwhile,these features showed more variable during the 6th hour of the recovery period after REM-SD compared with those in the 6th hour of the recovery period after Total-SD.These differences between REM-SD and Total-SD might result from the variant delay times and the distinct neurodynamic mechanisms for the compensatory responses during the recovery period after different types of SD.3.We found that during recovery period after both types of SD,the pivotal regions of DMN migrated from the posterior structures to the anterior regions.The migration of DMN hubs illustrated that SD might depress the activation in some cortical regions of brain networks including the DMN,and damage their executive functions.These depression and damage would be eliminated adaptively by the compensatory response and consciousness maintenance of brain during the recovery period after SD with the less employed power in normal sleep cycle.In conclusion,our study demonstrated that rat DMN displays the self-organized criticality after both types of SD and the significant avalanche was the basic unit of rat DMN activity.Moreover,the SWS-dependent significant avalanche maintained sleep homeostasis.Different migrations of pivotal DMN regions suggested that there existed distinct compensation mechanisms for the recovery periods after REM-SD and Total-SD,indicating a key role of DMN for sleep recovery.Overall,our study revealed the neuro-avalanche phenomenon of rat DMN during the recovery period of SD from the perspective of neurodynamic,and the results contribute to both important scientific significance and potential medical application for deepening our understanding of sleep compensation.