Linking the nature and functions of sleep: insights from multimodal imaging of the sleeping brain

Song, Chen; Tagliazucchi, Enzo

doi:10.1016/j.cophys.2019.11.012

Cited by 18 publications

(14 citation statements)

References 64 publications

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“…N1 sleep is characterized by diminished thalamo-cortical coupling with preserved cortical activation, a condition compatible with conscious mentation and imagery during the onset of sleep [52]. From an evolutionary perspective, it is reasonable that N1 sleep is susceptible to transitioning towards wakefulness upon external stimulation, since during this stage the individual is vulnerable to environmental threats, while offline information processing associated with learning and memory consolidation is not yet taking place [53]. On the other hand, propofol-induced unconsciousness and DoC are either artificially induced or arise as a consequence of brain injury, and thus do not reflect the adaptive pressures that constrain the stability of human sleep.…”

Section: Discussionmentioning

confidence: 99%

Perturbations in dynamical models of whole-brain activity dissociate between the level and stability of consciousness

et al. 2021

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Consciousness transiently fades away during deep sleep, more stably under anesthesia, and sometimes permanently due to brain injury. The development of an index to quantify the level of consciousness across these different states is regarded as a key problem both in basic and clinical neuroscience. We argue that this problem is ill-defined since such an index would not exhaust all the relevant information about a given state of consciousness. While the level of consciousness can be taken to describe the actual brain state, a complete characterization should also include its potential behavior against external perturbations. We developed and analyzed whole-brain computational models to show that the stability of conscious states provides information complementary to their similarity to conscious wakefulness. Our work leads to a novel methodological framework to sort out different brain states by their stability and reversibility, and illustrates its usefulness to dissociate between physiological (sleep), pathological (brain-injured patients), and pharmacologically-induced (anesthesia) loss of consciousness.

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Section: Discussionmentioning

confidence: 99%

Perturbations in dynamical models of whole-brain activity dissociate between the level and stability of consciousness

et al. 2021

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“…Transition of consciousness in the near-awake to light-decrease of alertness is emerging as a model for internally caused interactions (Canales-Johnson et al;Comsa et al, 2019;Noreika et al;Song and Tagliazucchi, 2020;Tagliazucchi and Laufs, 2014) . With lesion and pharmacological challenges, neuropsychology and cognitive neuroscience have tried to define the necessary and sufficient brain networks, areas and dynamics of the brain to implement cognition, revealing compensation, reconfiguration and plasticity (Adolphs, 2016;Valero-Cabré et al, 2017;Yeung et al, 2018) .…”

Section: Discussionmentioning

confidence: 99%

Decreasing alertness modulates perceptual decision-making

Jagannathan

Bareham

Bekinschtein

2020

Preprint

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The ability to make decisions based on external information, prior knowledge and context is a crucial aspect of cognition and it may determine the success and survival of an organism. Despite extensive and detailed work done on the decision making mechanisms, the understanding of the effects of arousal remain limited. Here we characterise behavioural and neural dynamics of decision making in awake and low alertness periods to characterise the compensatory signatures of the cognitive system when arousal decreases. We used an auditory tone-localisation task in human participants under conditions of fully awake and low arousal. Behavioural dynamics analyses using psychophysics, signal detection theory and drift-diffusion modelling showed slower responses, decreased performance and a lower rate of evidence accumulation due to alertness fluctuations. To understand the modulation in neural dynamics we used multivariate pattern analysis (decoding), identifying a shift in the temporal and spatial signatures involved. Finally, we connected the computational parameters identified in the drift diffusion modelling with neural signatures, capturing the effective lag exerted by alertness in the neurocognitive system underlying decision making. These results define the reconfiguration of the brain networks, regions and dynamics needed for the implementation of perceptual decision making, revealing mechanisms of resilience of cognition when challenged by decreases in arousal.

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“…A remarkable feature of the human brain is its adaptability and plasticity. Changes in brain structure occur not only when one is awake and interacting with the external world, but also when one is asleep (Bernardi et al, 2016;Cirelli, 2013;Song et al, 2017;Song & Tagliazucchi, 2020;Tononi & Cirelli, 2014;Vivo et al, 2017).…”

Section: Intra-individual Changes In Brain Structural Complexity and Consciousnessmentioning

confidence: 99%

“…The external inputs tend to co-activate different neurons, regardless of whether these neurons are previously unconnected, sparsely connected, or densely connected. The neuronal co-activation, in turn, will lead to a general increase in the number and strength of neuronal connections across the brain (Cirelli, 2013;Song & Tagliazucchi, 2020;Tononi & Cirelli, 2014). These wake-associated changes in brain structure are not sustainable (Figure 7): as neurons across the brain all get connected and neuronal connections across the brain all become saturated, the structural diversity between neurons and the structural diversity between neuronal connections will decrease; moreover, if the increase in neuronal connections continues without limits, for example due to prolonged wakefulness, the brain will eventually use up biological material to build, physical space to accommodate, and metabolic energy to support any further connections.…”

Section: Intra-individual Changes In Brain Structural Complexity and Consciousnessmentioning

confidence: 99%

“…By contrast, during sleep, the brain is disconnected from the external world and its activity is driven primarily by itself. The self-driven neuronal activity exhibits spontaneous alternations between periods of intense firing and periods of silence, which in turn will lead to the pruning of weak neuronal connections and the stabilization of strong neuronal connections (Cirelli, 2013;Song & Tagliazucchi, 2020; Figure 6: Inter-individual Differences in Brain Structural Complexity and Consciousness. Utilizing the inter-individual differences in cortical structure, studies have investigated the relationship between brain structure complexity and consciousness.…”

Section: Intra-individual Changes In Brain Structural Complexity and Consciousnessmentioning

confidence: 99%

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Brain structural complexity and consciousness

Song

2021

PhiMiSci

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Structure shapes function. Understanding what is structurally special about the brain that allows it to generate consciousness remains a fundamental scientific challenge. Recently, advances in brain imaging techniques have made it possible to measure the structure of human brain, from the morphology of neurons and neuronal connections to the gross anatomy of brain regions, in-vivo and non-invasively. Using advanced brain imaging techniques, it was discovered that the structural diversity between neurons and the topology of neuronal connections, as opposed to the sheer number of neurons or neuronal connections, are key to consciousness. When the structural diversity is high and the connections follow a modular topology, neurons will become functionally differentiable and functionally integrable with one another. The high levels of differentiation and integration, in turn, enable the brain to produce the richest conscious experiences from the smallest number of neurons and neuronal connections. Consequently, across individuals, those with a smaller brain volume but a higher structural diversity tend to have richer conscious experiences than those with a larger brain volume but a lower structural diversity. Moreover, within individuals, a reduction in neuronal connections, if accompanied by an increase in structural diversity, will result in richer conscious experiences, and vice versa. These findings suggest that having a larger number of neurons and neuronal connections is not necessarily beneficial for consciousness; in contrast, an optimal brain architecture for consciousness is one where the richest conscious experiences are generated from the smallest number of neurons and neuronal connections, at the minimal cost of biological material, physical space, and metabolic energy.

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Linking the nature and functions of sleep: insights from multimodal imaging of the sleeping brain

Cited by 18 publications

References 64 publications

Perturbations in dynamical models of whole-brain activity dissociate between the level and stability of consciousness

Perturbations in dynamical models of whole-brain activity dissociate between the level and stability of consciousness

Decreasing alertness modulates perceptual decision-making

Brain structural complexity and consciousness

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