Black swans: challenging the relationship of anaesthetic-induced unconsciousness and electroencephalographic oscillations in the frontal cortex

The study of general anaesthesia and electroencephalographic oscillations in the frontal cortex spans at least four decades, with several notable findings:

• In 1977, Tinker and colleagues¹ proposed, based on studies of the nonhuman primate, that anteriorization—the shift of electroencephalographic power from posterior cortex to frontal cortex—correlated with unresponsiveness during general anaesthesia.

• In the early 1990s, Steriade contributed to our understanding of the neurophysiology of sleep and general anaesthesia in animals, including descriptions of three distinct oscillations involving corticothalamic networks: a slow rhythm at < 1 Hz, a delta rhythm at 1-4 Hz, and a faster theta/alpha rhythm at 7-14 Hz.^2,3

• In the mid-1990s, the shift of alpha oscillations to more anterior structures was identified during both propofol sedation⁴ and isoflurane/nitrous...