Nature: Volume 650, February 2026
February 2, 2026
Scientists have identified a distinctive slide into unconsciousness during general anaesthesia. If the finding is confirmed, this pattern could help doctors to avoid sedating patients too deeply — or not deeply enough.
The data were collected from people about to have surgery. They show that as anaesthesia takes hold, the interplay between several brain areas falters. This shift could serve as a biomarker — a quantifiable biological measure — of loss of consciousness, the authors reported last week in Cell Reports Medicine (Y. Li et al. Cell Rep. Med. 7, 102581; 2026).
“This will finally provide the possibility [of] a translatable biomarker,” says co-author Ti-Fei Yuan, a neuroscientist at Shanghai Jiao Tong University in China.
But, Yuan acknowledges, the study assesses the effects of only one anaesthetic and relies on a new technique to infer brain-wide signals from data recorded from outside the skull.
Going under
Scientists have long sought non-behavioural correlates of consciousness. Anaesthesiologists could use such signatures to fine-tune drug dosing and avoid the complications and side-effects of over- and under-sedation.
In search of such a marker, Yuan and his colleagues studied 31 people who received the widely used drug propofol as a general anaesthetic before surgery.
The authors placed 128 electrodes on each participant’s scalp to record the underlying neurons’ electrical activity from many positions. They then used emerging mathematical methods to isolate signals originating from nine brain regions previously implicated in mediating consciousness and examined connections between pairs of these regions.
Among them were the parietal cortex, which is at the top of the brain, about halfway between the forehead and the back of the skull; the occipital cortex, at the back of the head; and several small, deeper structures, such as one called the thalamus.
Before the propofol was administered, an oscillating brain wave called an alpha-band wave was highly synchronized between the parietal area and the thalamus. This correlation was a sign that these areas are in close communication in the awake brain. The researchers also saw signs of high connectivity between the parietal and occipital areas in the unsedated brain.
But when the participants lost consciousness under anaesthesia, the alpha-band activity between the parietal cortex and deep-brain structures became desynchronized. So did the activity between the parietal cortex and the occipital cortex. Yuan says that the key role of the parietal cortex and its communications with the thalamus challenge the view that the frontal cortex — the region just behind the forehead — is central to maintaining consciousness.
Deep-brain data needed
Andrea Luppi, a neuroscientist at the University of Cambridge, UK, says the work supports previous research indicating that the thalamus plays a crucial part in regulating consciousness under anaesthesia. He also says that the work will feed debates about the relative importance of frontal versus parietal activity.
Luppi does note, however, that the techniques used in the paper might not accurately isolate signals from small structures deep in the brain, such as the thalamus. “This is still a field of active development,” he says, adding that confirmation using electrodes implanted deeper into the brain would bolster the conclusions. Such electrodes are used in some forms of neurosurgery. Luppi would also like to know whether the same regions’ connectivity changes in response to other general anaesthetics and whether these changes reverse when people regain consciousness.
Yuan says his group is working on these experiments. He also acknowledges that 128-electrode arrays cannot be feasibly used at scale. But he hopes that a handful of electrodes strategically attached to a person’s forehead will be able to tap into the key brain circuits. Such a system, Yuan says, could enter all surgical departments.
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