Spatiotemporal brain complexity quantifies consciousness outside of perturbation paradigms
Martin Breyton, Jan Fousek, Giovanni Rabuffo, Pierpaolo Sorrentino, Lionel Kusch, Marcello Massimini, Spase Petkoski, Viktor Jirsa
bioRxiv Preprint Server April 18, 2023 preprint DOI: 10.1101/2023.04.18.537321 via bioRxiv
Summary
Consciousness depends on the brain's ability to produce complex, variable patterns of activity after a perturbation, but measuring this directly is difficult. Using a whole-brain model, researchers found that such complexity only arises when spontaneous brain activity is highly fluid—meaning functional networks reorganize extensively. This fluid regime can be captured by a small set of dynamical systems metrics, which predict the effects of consciousness-altering drugs like Xenon, Propofol, and Ketamine. These predictions were validated in 15 subjects at different consciousness levels, showing agreement with established perturbational complexity measures but using a simpler, more accessible paradigm. The findings point to complexity properties underlying consciousness.
Study at a glance
| Characteristics | Observational cohort with computational modeling |
|---|---|
| Sample size | 15 |
| Population | Human subjects at various stages of consciousness |
| Key finding | Brain fluidity, measured by dynamical systems metrics, predicts levels of consciousness and agrees with perturbational complexity in a simpler paradigm. |
Abstract
Signatures of consciousness are found in spectral and temporal properties of neuronal activity. Among these, spatiotemporal complexity after a perturbation has recently emerged as a robust metric to infer levels of consciousness. Perturbation paradigms remain, however, difficult to perform routinely. To discover alternative paradigms and metrics, we systematically explore brain stimulation and resting-state activity in a whole-brain model. We find that perturbational complexity only occurs when the brain model operates within a specific dynamical regime, in which spontaneous activity produces a large degree of functional network reorganizations referred to as being fluid. The regime of high brain fluidity is characterized by a small battery of metrics drawn from dynamical systems theory and predicts the impact of consciousness-altering drugs (Xenon, Propofol, and Ketamine). We validate the predictions in a cohort of 15 subjects at various stages of consciousness and demonstrate their agreement with previously reported perturbational complexity, but in a more accessible paradigm. Beyond the facilitation in clinical use, the metrics highlight complexity properties of brain dynamics in support of the emergence of consciousness.