Dynamic Connectivity Patterns in Conscious and Unconscious Brain

Ma, Yuncong; Hamilton, C.J.; Zhang, Nanyin

doi:10.1089/brain.2016.0464

Cited by 69 publications

(63 citation statements)

References 61 publications

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“…Meta-analysis of numerous neuroimaging literature identified a functional spectrum along this hierarchical gradient from simple sensory perceptions to abstract and complex cognitive functions (31). A series of studies have found consistent evidence across species that the resting-state connectivity/dynamics are divergently modulated across the lower-and higher-order regions from wake to anesthetized conditions (32)(33)(34)(35). In addition, resting-state fMRI connectivity changes associated with a general psychopathological score, which reflects chronicity and symptom severity of mental illness in patient groups but risks in healthy individuals, also diverge in these two sets of brain regions (36).…”

Section: Discussionmentioning

confidence: 99%

Neuroimaging contrast across the cortical hierarchy is the feature maximally linked to behavior and demographics

Han

Brown

et al. 2019

Preprint

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AbstractWe employed a data-driven canonical correlation analysis to investigate the population covariance of whole-brain cortical thickness, resting-state functional connectivity, and hundreds of behavioral/demographic measures in a large cohort of individuals. We found that the maximal thickness-behavior correlation and the maximal connectivity-behavior correlation are largely converged along the same direction across subjects, which is characterized by very specific modulations of all three modalities. Along this direction, individuals tend to have more positive and less negative behavioral/demographic traits, and more importantly, their functional connectivity and cortical thickness show a similar divergent modulation across the cortical hierarchy: thinner cortex and stronger functional connectivity at the higher-order cognitive regions whereas thicker cortex and weaker connectivity at the lower-order sensory/motor areas. These findings provide a unique link between structural and functional brain organizations and human behavior. Specifically, they suggest that the cross-hierarchy contrast of structural and functional brain measures may be a specific feature linked to the overall goodness of behavior and demographics.

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Section: Discussionmentioning

confidence: 99%

Neuroimaging contrast across the cortical hierarchy is the feature maximally linked to behavior and demographics

Han

Brown

et al. 2019

Preprint

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“…All imaging and behavioral data (LORR) were also used in a separate study (Ma et al 2016), which examined the dynamic connectivity patterns in conscious and unconscious brain. All data were reanalyzed for a different purpose specifically for this study.…”

Section: Methodsmentioning

confidence: 99%

Global reduction of information exchange during anesthetic-induced unconsciousness

Hamilton

Zhang

2017

Brain Struct Funct

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During anesthetic-induced unconsciousness (AIU), the brain undergoes a dramatic change in its capacity to exchange information between regions. However, the spatial distribution of information exchange loss/gain across the entire brain remains elusive. In the present study, we acquired and analyzed resting-state functional magnetic resonance imaging (rsfMRI) data in rats during wakefulness and graded levels of consciousness induced by incrementally increasing the concentration of isoflurane. We found that, regardless of spatial scale, the functional connectivity (FC) change (i.e. ΔFC) was proportionally dependent on the FC strength at the awake state across all connections. This dependency became stronger at higher doses of isoflurane. In addition, the relative FC change at each anesthetized condition (i.e. ΔFC normalized to the corresponding FC strength at the awake state) was exclusively negative across the whole brain, indicating a global loss of meaningful information exchange between brain regions during AIU. To further support this notion, we showed that during unconsciousness, the entropy of rsfMRI signal increased to a value comparable to random noise while the mutual information decreased appreciably. Importantly, consistent results were obtained when unconsciousness was induced by dexmedetomidine, an anesthetic agent with a distinct molecular action than isoflurane. This result indicates that the observed global reduction in information exchange may be agent invariant. Taken together, these findings provide compelling neuroimaging evidence suggesting that the brain undergoes a widespread disruption in the exchange of meaningful information during AIU, and that this phenomenon may represent a common systems-level neural mechanism of AIU.

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“…Another recent study with nonhuman primates used propofol anaesthesia to characterize the transition between consciousness and unconsciousness, replicating this general pattern of results and showing that the predominant FC brain state during unconsciousness closely resembled the underlying anatomical map. This finding has been further demonstrated in both rats under isoflurane anesthesia (Ma et al 2017) and in human deep sleep (Tagliazucchi et al 2016) , suggesting that anesthesia serves to constrain the dynamic repertoire of FC patterns onto an anatomical structural backbone (see also Fischer et al 2018) . As alluded to above, our findings provide a complementary perspective from which to view these results: the type of modular flexibility expressed by brain regions at different levels of sedation (e.g., disjointedness vs. cohesive flexibility) may ultimately underly the phenomenological effects of anesthesia.…”

Section: Methodological Considerationsmentioning

confidence: 79%

Dynamic reconfiguration, fragmentation and integration of whole-brain modular structure across depths of unconsciousness

Standage

Areshenkoff

Nashed

et al. 2019

Preprint

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General anesthetics are routinely used to induce unconsciousness, and much is known about their effects on receptor function and single neuron activity. Much less is known about how these local effects are manifest at the whole-brain level, nor how they influence network dynamics, especially past the point of induced unconsciousness. Using resting-state functional magnetic resonance imaging (fMRI) with nonhuman primates, we investigated the dose-dependent effects of anesthesia on whole-brain temporal modular structure, following loss of consciousness. We found that higher isourane dose was associated with an increase in both the number and isolation of whole-brain modules, as well as an increase in the uncoordinated movement of brain regions between those modules. Conversely, we found that higher dose was associated with a decrease in the cohesive movement of brain regions between modules, as well as a decrease in the proportion of modules in which brain regions participated. Moreover, higher dose was associated with a decrease in the overall integrity of networks derived from the temporal modules, with the exception of a single, sensory-motor network. Together, these findings suggest that anaesthesia-induced unconsciousness results from the hierarchical fragmentation of dynamic whole-brain network structure, leading to the discoordination of temporal interactions between cortical modules.

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Dynamic Connectivity Patterns in Conscious and Unconscious Brain

Cited by 69 publications

References 61 publications

Neuroimaging contrast across the cortical hierarchy is the feature maximally linked to behavior and demographics

Neuroimaging contrast across the cortical hierarchy is the feature maximally linked to behavior and demographics

Global reduction of information exchange during anesthetic-induced unconsciousness

Dynamic reconfiguration, fragmentation and integration of whole-brain modular structure across depths of unconsciousness

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