Neuronal Avalanche In Rat Electrophysiological Default Mode Network

Self-organized criticality refers to a property of dynamical systems that can transit freely between the stable and unstable states without any external stimulus.As one of the important characteristics of self-organized criticality,avalanche refers to the overall chain-like change or recombination of the system under the slight disturbance that comply with non-scale statistics.It has been demonstrated that real brain exhibits the similar property across different spatial scales and species.As a group of specific brain regions,the default mode network(DMN)is supposed to have the feature of spontaneous state transitions,but the relationships between DMN and self-organized critical state are still unclear.In this thesis,we collected electrophysiological data of DMN in freely behaving rats across three vigilance states: wakeful(WK),rapid eye movement sleep(REM)and slow wave sleep(SWS).The relevance analysis of neuronal avalanches was applied to explore the relationship between DMN and self-organized critical state in different vigilance states,and to reveal the internal relation between DMN related brain regions and neural avalanche patterns.Our main results are summarized as follows:1.By analyzing the spatial-temporal characteristics of avalanche data across different vigilance states,we found that the neuronal avalanche events in rat DMN brain regions satisfied the power-law distribution in both WK and REM states,indicating a strong invariance in both temporal and spatial scales.In SWS state,the distribution of neuronal avalanche events tends to shift to the exponential statistics and exhibits the subcritical avalanche dynamics,suggesting a relatively weak invariance in temporal and spatial scales.Therefore,we hypothesized that the existence of neuronal self-organized criticality in DMN related brain regions is highly associated with the level of conscious activity.2.Through a detailed analysis of significant avalanche patterns,we found that the neuronal avalanche patterns recorded in different vigilance states were repeated in a highly stereotyped way.Comparing with the case of WK state,a prominent increase in significant avalanche patterns was identified in REM state,whereas the opposite trend was observed in SWS state.By performing the dependency analysis of avalanche patterns on vigilance states,we showed that both REM and SWS states have more significant state-dependent avalanche patterns.Remarkably,such dependency was found to come from the vigilance state-induced changes in DMN related brain regions rather than brain region encodings.3.We further analyzed the state-independent neuronal avalanches across different vigilance states.For WK and REM states,our results indicated that the state-independent neuronal avalanches in rat DMN reappear in a relatively long-periodic way.In contrast,the state-independent avalanche patterns in SWS state appear periodically with a low frequency.Additionally,we also found that the encoding patterns of neuronal avalanches in SWS and WK states are completely different.In summary,our results showed that the rat DMN brain regions had closely relations with self-organized criticality in different vigilance states.In particular,the rat DMN participates in consciousness maintenance by activating different core brain regions under different vigilance states,whereas the state-independent neuronal avalanches tend to keep the fundamental brain functions.These findings might not only provide the features of the rat DMN from the dynamical perspective,but also inspire novel insights into the neural information integration mechanism involved in DMN and the underlying mechanism of consciousness maintenance.