Communications Biology
January 28, 2023
Andrea I. Luppi, Jakub Vohryzek, Morten L. Kringelbach et al.
98 citations
Consciousness depends on how tightly brain function follows the brain's physical wiring. Using MRI scans, researchers measured structure-function coupling across spatial scales in people who were unconscious from anesthesia or brain injury and in people under psychedelics (LSD or ketamine). During loss of consciousness, function more closely tracked the brain's structural connections, a signature that could distinguish behaviorally similar brain-injured patients and detect covert consciousness. In contrast, psychedelics decoupled function from structure, and this decoupling correlated with physiological and subjective scores. The findings suggest that connectome harmonic decomposition reveals how neuromodulation and network architecture jointly shape consciousness.
bioRxiv
November 26, 2020
Andrea I. Luppi, Pedro A. M. Mediano, Fernando E. Rosas et al.
49 citations
preprint
The brain coordinates information from many sources to create a unified conscious experience. Combining network science and information theory, the authors identify a “synergistic global workspace” where gateway regions gather synergistic information from specialized brain modules, integrate it, and then broadcast it widely via broadcaster regions. Functional MRI shows that gateway regions correspond to the default mode network and broadcasters to the executive control network. Loss of consciousness from general anesthesia or disorders of consciousness reduces the workspace’s ability to integrate information, which is restored upon recovery. This work reconciles aspects of the Global Neuronal Workspace and Integrated Information Theory.
bioRxiv (Cold Spring Harbor Laboratory)
August 10, 2020
Andrea I. Luppi, Jakub Vohryzek, Morten L. Kringelbach et al.
26 citations
preprint
Consciousness arises from how the brain's structural wiring shapes its dynamic activity. By decomposing resting-state fMRI data into harmonic modes of the human structural connectome, a generalizable signature of lost consciousness emerges—whether from anesthesia or brain injury—while a reversed signature characterizes psychedelic states induced by LSD or ketamine, reflecting decoupling of function from structure. This connectome harmonic approach discriminates between behaviorally indistinguishable brain-injured patients and tracks covert consciousness, linking neurobiology to conscious experience.
Elife
July 18, 2024
Andrea I. Luppi, Pedro A. M. Mediano, Fernando E. Rosas et al.
1 citation
Loss of consciousness significantly disrupts the brain's ability to integrate information. In a study involving functional MRI analysis, it was revealed that gateway regions in a 'synergistic global workspace' correspond to the default mode network, while broadcaster regions align with the executive control network. This integration breakdown occurs during general anaesthesia or disorders of consciousness, with recovery restoring functionality. The findings enhance understanding of consciousness by bridging Global Neuronal Workspace and Integrated Information Theory, highlighting the critical role of brain networks in maintaining conscious experience.
Neuroimage
February 11, 2023
Andrea I. Luppi, Pedro A. M. Mediano, Fernando E. Rosas et al.
High-level brain functions are thought to arise from coordinated activity across neural systems, but this has been hard to test empirically. Using a framework called Integrated Information Decomposition, which quantifies emergence in dynamical systems, the authors analyzed functional MRI data and found that emergent and hierarchical neural dynamics are significantly reduced in chronically unresponsive patients with severe brain injury. Emergence capacity was positively correlated with hierarchical organization in brain activity. Combining network control theory and whole-brain modeling, the authors show that reduced emergent and hierarchical dynamics in these patients can be explained by disruptions in the structural connectome. The results suggest that chronic unresponsiveness after severe brain injury may stem from structural damage to neural infrastructure needed for emergent brain dynamics.
Communications Biology
April 20, 2022
A. Luppi, P. Mediano, F. Rosas et al.
A neurobiologically realistic computational model of whole-brain haemodynamic signals, perturbed to simulate loss of consciousness, reveals two distinct neurobiological paths to unconscious brain activity. Incorporating PET data on GABA receptor distribution shows that spatially-specific local inhibition reproduces fMRI activity observed during propofol anaesthesia. Incorporating diffusion MRI data from patients with disorders of consciousness shows that randomized neuroanatomical connectivity can also produce the dynamics characteristic of loss of consciousness. The results generalize across anaesthesia and injury datasets, suggesting that increased inhibition and connectome perturbation are distinct routes to the same functional brain dynamics.
Proceedings of the National Academy of Sciences of the United States of America
July 23, 2021
L. R. Spindler, A. Luppi, R. Adapa et al.
A network of brain regions called the default mode network breaks down during anesthesia and after brain damage causing disorders of consciousness. The neurochemical reasons for this breakdown were unclear. Using functional MRI, researchers found that the ventral tegmental area, a dopamine-producing brainstem region, disconnects from key default mode network nodes (precuneus and posterior cingulate) during both propofol sedation and disorders of consciousness. Stronger connectivity between the ventral tegmental area and these nodes was associated with a more awake-like configuration of the default mode network. In patients with disorders of consciousness who later improved behaviorally, this connectivity increased toward healthy levels. In a separate group of traumatic brain injury patients, the drug methylphenidate significantly strengthened this connection. The findings suggest that dopamine modulation may be central to maintaining consciousness.
PLoS One
February 13, 2020
Thomas F. Varley, Michael M. Craig, R. Adapa et al.
Fractal dimension of brain activity—a measure of complexity beyond simple randomness—is lower in patients with disorders of consciousness than in healthy volunteers. Using fMRI data, fractal dimension was computed for cortical functional connectivity networks, adjacency matrices, and BOLD time-series. Healthy volunteers (n=15) had the highest fractal dimensions, followed by patients in a minimally conscious state (n=10), and patients in a vegetative state (n=8). Decreases in fractal dimension correlated with decreasing level of consciousness regardless of injury mechanism. The findings support the hypothesis that consciousness is associated with brain complexity and that fractal structures may indicate proximity to a critical point between low- and high-entropy states.
Nature Communications
October 10, 2019
A. Luppi, Michael M. Craig, I. Pappas et al.
Consciousness relies on spatio-temporal interactions between brain integration and functional diversity. Combining graph theory and dynamic functional connectivity, resting-state fMRI data from awake volunteers, propofol-anaesthetised volunteers, and patients with disorders of consciousness showed that cortical networks are especially affected during loss of consciousness in temporal states of high integration, exhibiting reduced functional diversity and compromised informational capacity, while thalamo-cortical functional disconnections emerge during states of higher segregation. Posterior regions of the brain's default mode network show reductions in both functional diversity and integration during unconsciousness. These overlapping reductions in diversity and integration may represent a generalisable biomarker of loss of consciousness.