After hemispherotomy surgery for epilepsy, which disconnects an entire brain hemisphere, the isolated cortex shows brainwave patterns typical of deep sleep or anesthesia, not wakefulness. In 10 pediatric patients, EEG recordings revealed prominent slow oscillations and a steeper spectral decay in the disconnected hemisphere, while the connected hemisphere maintained normal waking patterns. These sleep-like patterns persisted years after surgery, suggesting the isolated cortex likely lacks awareness.
Only 47 out of over 7,700 time-series features reliably distinguished wakefulness from anesthesia or sleep across all evaluation groups of flies. Most of these features were related to autocorrelation, indicating that signals during wakefulness remained correlated to their past for longer than during anesthesia or sleep. Features related to complexity or spectral power, often proposed as consciousness markers, failed to generalize across all datasets, though many showed consistent direction of effect. These results caution that many newly discovered potential consciousness markers may not generalize across datasets, and point to autocorrelation as a class of dynamical properties that does.
A new pre-registered study in PLOS Biology compares several proposed neuronal markers of loss of consciousness in flies across three global brain states: awake, asleep, and anesthetized. The work evaluates which neural markers can differentiate these states, testing markers previously suggested to underlie states of consciousness. The findings indicate which markers reliably distinguish between wakefulness, sleep, and anesthesia in the fly model.