"Paradoxical wakefulness" induced by psychedelic 5-methoxy-N,N-dimethyltryptamine in mice
Psychedelics lead to profound changes in subjective experience and behaviour, which are typically conceptualised in psychological terms rather than corresponding to an altered brain state or a distinct state of arousal. Here, we performed chronic electrophysiological recordings from the cortex concomitant with pupillometry in freely moving adult male mice following an injection of a short-acting psychedelic 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT). We observed an acute induction of a dissociated state of arousal, characterised by prominent sleep-like slow waves in the cortex and marked pupil dilation in behaviourally awake, moving animals. REM sleep was markedly suppressed, similar to the effect of conventional antidepressants. We argue that the occurrence of a dissociated brain state combining features of waking and sleep may fundamentally underpin the known and hypothesised effects of psychedelics -- from dream-like hallucinations to reopening of the critical period for plasticity.