Background: Ketamine, in doses suitable to induce anaesthesia in humans, gives rise to a unique state of unresponsiveness accompanied by vivid experiences and sensations, making it possible to disentangle the correlated but distinct concepts of conscious awareness and behavioural responsiveness. This distinction is often overlooked in the study of consciousness.
Methods: The mathematical framework of connectome harmonic decomposition (CHD) was used to view functional magnetic resonance imaging (fMRI) signals during ketamine-induced unresponsiveness as distributed patterns across spatial scales. The connectome harmonic signature of this particular state was mapped onto signatures of other states of consciousness for comparison.
Results: An increased prevalence of fine-grained connectome harmonics was found in fMRI signals obtained during ketamine-induced unresponsiveness, indicating higher granularity. After statistical assessment, the ketamine sedation harmonic signature showed alignment with signatures of LSD-induced (fixed effect =0.0113 [0.0099, 0.0127], P<0.001) or ketamine-induced (fixed effect =0.0087 [0.0071, 0.0103], P<0.001) psychedelic states, and misalignment with signatures seen in unconscious individuals owing to propofol sedation (fixed effect =-0.0213 [-0.0245, -0.0181], P<0.001) or brain injury (fixed effect =-0.0205 [-0.0234, -0.0178], P<0.001).
Conclusions: The CHD framework, which only requires resting-state fMRI data and can be applied retrospectively, has the ability to track alterations in conscious awareness in the absence of behavioural responsiveness on a group level. This is possible because of ketamine's unique property of decoupling these two facets, and is important for consciousness and anaesthesia research.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1016/j.bja.2024.12.036 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Connectome harmonic decomposition tracks the presence of disconnected consciousness during ketamine-induced unresponsiveness.
Br J Anaesth
February 2025
Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK; Division of Anaesthesia, University of Cambridge, Cambridge, UK; Centre for Eudaimonia and Human Flourishing, Department of Psychiatry, University of Oxford, Oxford, UK; Division of Information Engineering, University of Cambridge, Cambridge, UK; St John's College, University of Cambridge, Cambridge, UK.
Background: Ketamine, in doses suitable to induce anaesthesia in humans, gives rise to a unique state of unresponsiveness accompanied by vivid experiences and sensations, making it possible to disentangle the correlated but distinct concepts of conscious awareness and behavioural responsiveness. This distinction is often overlooked in the study of consciousness.
Methods: The mathematical framework of connectome harmonic decomposition (CHD) was used to view functional magnetic resonance imaging (fMRI) signals during ketamine-induced unresponsiveness as distributed patterns across spatial scales.
Human brain dynamics are shaped by rare long-range connections over and above cortical geometry.
Proc Natl Acad Sci U S A
January 2025
Centre for Brain and Cognition, Computational Neuroscience Group, Department of Information and Communication Technologies, Universitat Pompeu Fabra, Barcelona 08018, Spain.
Article Synopsis
- A topological principle suggests that the physical structure of the brain (its anatomy) significantly influences its functional dynamics.
- Researchers found that while local connectivity patterns can explain much of brain function, they overlook the essential role of rare long-range cortical connections, which enhance information processing.
- By incorporating both local connections and these rare long-range connections into a combined model (EDR+LR), they showed that this approach more effectively captures the complexities of brain activity compared to traditional geometric representations.
Dynamic Functional Connectome Harmonics.
Med Image Comput Comput Assist Interv
October 2023
Department of Radiology, University of North Carolina, Chapel Hill, NC, USA.
Functional connectivity (FC) "gradients" enable investigation of connection topography in relation to cognitive hierarchy, and yield the primary axes along which FC is organized. In this work, we employ a variant of the "gradient" approach wherein we solve for the normal modes of FC, yielding functional connectome harmonics. Until now, research in this vein has only considered static FC, neglecting the possibility that the principal axes of FC may depend on the timescale at which they are computed.
View Article and Find Full Text PDFIntegrative, segregative, and degenerate harmonics of the structural connectome.
Commun Biol
August 2024
Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA.
Unifying integration and segregation in the brain has been a fundamental puzzle in neuroscience ever since the conception of the "binding problem." Here, we introduce a framework that places integration and segregation within a continuum based on a fundamental property of the brain-its structural connectivity graph Laplacian harmonics and a new feature we term the gap-spectrum. This framework organizes harmonics into three regimes-integrative, segregative, and degenerate-that together account for various group-level properties.
View Article and Find Full Text PDFTime-resolved coupling between connectome harmonics and subjective experience under the psychedelic DMT.
bioRxiv
May 2024
Centre for Eudaimonia and Human Flourishing, Linacre College, University of Oxford, Oxford, United Kingdom.
Exploring the intricate relationship between brain's structure and function, and how this affects subjective experience is a fundamental pursuit in neuroscience. Psychedelic substances offer a unique insight into the influences of specific neurotransmitter systems on perception, cognition and consciousness. Specifically, their impact on brain function propagates across the structural connectome - a network of white matter pathways linking different regions.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!