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 ...
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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