Hypnagogic (sleep-onset) and hypnopompic (awakening) experiences, including vivid dream-like perceptions without external stimuli, share neural mechanisms with pathological hallucinations in brain disorders such as Parkinson's disease and psychosis. Lucid dreaming, where the dreamer becomes aware of dreaming, may offer insights into these mechanisms. The authors suggest that studying these common sleep phenomena can illuminate the brain's reality-creation processes and inform understanding of neurological and mental health conditions. Recognizing the continuum between normal sleep experiences and pathological hallucinations could improve diagnosis and treatment of brain disorders.
Under isoflurane anaesthesia, activating layer 5 pyramidal neurons in one hemisphere of the mouse sensorimotor cortex using chemogenetics (DREADDs) produced local wakefulness-like activity—shifting from slow-wave to tonic firing—and disrupted interhemispheric synchrony with the opposite hemisphere. However, this local activation did not reduce the depth of unconsciousness during deep anaesthesia or during transitions into or out of anaesthesia. Global layer 5 synchrony may be sufficient for anaesthesia-induced unconsciousness but is not necessary, at least under isoflurane. Local wakefulness-like activity in layer 5 cortex can occur during deep anaesthesia, highlighting the need to further explore local versus global aspects of anaesthesia-induced unconsciousness.