Muting, not fragmentation, of functional brain networks under general anesthesia

Areshenkoff, Corson N.; Nashed, Joseph Y.; Hutchison, R. Matthew; Hutchison, Melina; Lévy, Ron; Cook, Douglas J.; Menon, Ravi S.; Everling, Stefan; Gallivan, Jason P.

doi:10.1101/2020.07.08.188011

Cited by 7 publications

(12 citation statements)

References 61 publications

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“…This could be consistent with both a reduction in high-frequency noise, as well as a decreasing correlation length, both of which are consistent with other, well-established elements of propofol anaesthesia. As previously mentioned, a leading hypothesis is that anaesthetics like propofol “fragment” brain networks [ 64 , 73 , 74 ], or alternately “mute” the flow of information [ 75 ] between regions. In the context of functional connectivity analysis (a core element of many of these analyses), decreased connectivity can be directly related to a decrease in correlation length, which is consistent with the loss of power-law behaviour in the tails of the distributions.…”

Section: Discussionmentioning

confidence: 99%

Differential effects of propofol and ketamine on critical brain dynamics

et al. 2020

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Whether the brain operates at a critical “tipping” point is a long standing scientific question, with evidence from both cellular and systems-scale studies suggesting that the brain does sit in, or near, a critical regime. Neuroimaging studies of humans in altered states of consciousness have prompted the suggestion that maintenance of critical dynamics is necessary for the emergence of consciousness and complex cognition, and that reduced or disorganized consciousness may be associated with deviations from criticality. Unfortunately, many of the cellular-level studies reporting signs of criticality were performed in non-conscious systems (in vitro neuronal cultures) or unconscious animals (e.g. anaesthetized rats). Here we attempted to address this knowledge gap by exploring critical brain dynamics in invasive ECoG recordings from multiple sessions with a single macaque as the animal transitioned from consciousness to unconsciousness under different anaesthetics (ketamine and propofol). We use a previously-validated test of criticality: avalanche dynamics to assess the differences in brain dynamics between normal consciousness and both drug-states. Propofol and ketamine were selected due to their differential effects on consciousness (ketamine, but not propofol, is known to induce an unusual state known as “dissociative anaesthesia”). Our analyses indicate that propofol dramatically restricted the size and duration of avalanches, while ketamine allowed for more awake-like dynamics to persist. In addition, propofol, but not ketamine, triggered a large reduction in the complexity of brain dynamics. All states, however, showed some signs of persistent criticality when testing for exponent relations and universal shape-collapse. Further, maintenance of critical brain dynamics may be important for regulation and control of conscious awareness.

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Section: Discussionmentioning

confidence: 99%

Differential effects of propofol and ketamine on critical brain dynamics

et al. 2020

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“…Note that the aforementioned procedure, repeated over two fMRI sessions, was collected to explore individual differences in functional brain organization related to sensorimotor adaptation, de-adaptation, and subsequent re-adaptation (see [57, 87]). Given that the present study aims to specifically examine changes in functional brain architecture during initial adaptation to a novel visuomotor perturbation, we focused our analyses exclusively on the task scans of the first session.…”

Section: Methodsmentioning

confidence: 99%

Distinct patterns of cortical manifold expansion and contraction underlie human sensorimotor adaptation

Gale

Areshenkoff

Standage

et al. 2022

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Sensorimotor learning is a dynamic, systems-level process that involves the combined action of multiple neural systems distributed across the brain. Although we understand a great deal about the specialized cortical systems that support specific components of action (such as reaching), we know less about how cortical systems function in a coordinated manner to facilitate adaptive behaviour. To address this gap in knowledge, our study measured human brain activity using functional MRI (fMRI) while participants performed a classic sensorimotor adaptation task, and used a manifold learning approach to describe how behavioural changes during adaptation relate to changes in the landscape of cortical activity. During early adaptation, we found that areas in parietal and premotor cortex exhibited significant contraction along the cortical manifold, which was associated with their increased covariance with regions in higher-order association cortex, including both the default mode and fronto-parietal networks. By contrast, during late adaptation, when visuomotor errors had been largely reduced, we observed a significant expansion of visual cortex along the cortical manifold, which was associated with its reduced covariance with association cortex and its increased intraconnectivity. Lastly, we found that individuals who learned more rapidly exhibited greater covariance between regions in the sensorimotor and association cortices during early adaptation. Together, these findings are consistent with a view that sensorimotor adaptation depends on changes in the integration and segregation of neural activity across more specialized regions of unimodal cortex with regions in association cortex implicated in higher-order processes. More generally, they lend support to an emerging line of evidence implicating regions of the default mode network in task-based performance.

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“…This could be consistent with both a reduction in high-frequency noise, as well as a decreasing correlation length, both of which are consistent with other, well-established elements of propofol anaesthesia. As previously mentioned, a leading hypothesis is that anaesthetics like propofol "fragment" brain networks [64,73,74], or alternately "mute" the flow of information [75] between regions. In the context of functional connectivity analysis (a core element of many of these analyses), decreased connectivity can be directly related to a decrease in correlation length, which is consistent with the loss of power-law behaviour in the tails of the distributions.…”

Section: Indicators Of Critical Dynamicsmentioning

confidence: 99%

Differential Effects of Propofol and Ketamine on Critical Brain Dynamics

Varley

Sporns

Puce

et al. 2020

Preprint

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Whether the brain operates at a critical "tipping" point is a long standing scientific question, with evidence from both cellular and systems-scale studies suggesting that the brain does sit in, or near, a critical regime. Neuroimaging studies of humans in altered states of consciousness have prompted the suggestion that maintenance of critical dynamics is necessary for the emergence of consciousness and complex cognition, and that reduced or disorganized consciousness may be associated with deviations from criticality. Unfortunately, many of the cellular-level studies reporting signs of criticality were performed in non-conscious systems (in vitro neuronal cultures) or unconscious animals (e.g. anaesthetized rats). Here we attempted to address this knowledge gap by exploring critical brain dynamics in invasive ECoG recordings from multiple sessions with a single macaque as the animal transitioned from consciousness to unconsciousness under different anaesthetics (ketamine and propofol). We use a previously-validated test of criticality: avalanche dynamics to assess the differences in brain dynamics between normal consciousness and both drug-states. Propofol and ketamine were selected due to their differential effects on consciousness (ketamine, but not propofol, is known to induce an exotic state known as "dissociative anaesthesia"). Our analyses indicate that propofol dramatically restricted the size and duration of avalanches, while ketamine allowed for a more awake-like dynamic to persist. In addition, propofol, but not ketamine, triggered a large reduction in the complexity of brain dynamics. All states, however, showed some signs of persistent criticality when testing for exponent relations and universal shape-collapse. Further, maintenance of critical brain dynamics may be important for regulation and control of conscious awareness. Author summaryHere we explore how different anaesthetic drugs change the nature of brain dynamics, using sub-dural electrophysiological arrays implanted in a macaque brain. Previous research has suggested that loss of consciousness under anaesthesia is associated with a movement away from critical brain dynamics, towards a less flexible regime. When comparing ketamine and propofol, two anaesthetics with largely different effects on consciousness, we find that propofol, but not ketamine, produces a dramatic reduction in the complexity of brain activity and restricts the range of scales where critical March 27, 2020 1/28 dynamics are plausible. These results suggest that maintenance of critical dynamics may be important for regulation and control of conscious awareness. Introduction 1The hypothesis that the brain operates in a critical regime near a "tipping" point 2 between different states (often, but not always, described as low and high entropy, 3 respectively) is growing in popularity, both on neurophysiological evidence and due to 4 appealing properties of critical, or near-critical, systems [1], that are thought to be key 5 elements of optimal nervous system functioning. I...

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Muting, not fragmentation, of functional brain networks under general anesthesia

Cited by 7 publications

References 61 publications

Differential effects of propofol and ketamine on critical brain dynamics

Differential effects of propofol and ketamine on critical brain dynamics

Distinct patterns of cortical manifold expansion and contraction underlie human sensorimotor adaptation

Differential Effects of Propofol and Ketamine on Critical Brain Dynamics

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