Still conscious? Brain marker signals when anaesthesia takes hold

"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."

"Scientists have identified a distinctive brain-wave pattern that marks the 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. "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. To seek such a marker, Yuan and his colleagues studied 31 people who received the widely used drug propofol as a general anaesthetic before surgery."

A distinctive brain-wave pattern marks the transition into unconsciousness during propofol anaesthesia. Data were collected from 31 people receiving propofol before surgery. 128 electrodes recorded neuronal electrical activity from many scalp positions. Emerging mathematical methods isolated signals from nine brain regions implicated in consciousness and examined pairwise connections. The parietal cortex, occipital cortex and deeper structures such as the thalamus were analyzed. As anaesthesia took hold, interplay between several brain areas faltered. The shift could serve as a quantifiable biomarker to help avoid over- or under-sedation. The finding is limited to one anaesthetic and relies on an inferential external-recording technique.

Read at Nature