RT Journal Article SR Electronic T1 Broadband Cortical Desynchronization Underlies the Human Psychedelic State JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 15171 OP 15183 DO 10.1523/JNEUROSCI.2063-13.2013 VO 33 IS 38 A1 Suresh D. Muthukumaraswamy A1 Robin L. Carhart-Harris A1 Rosalyn J. Moran A1 Matthew J. Brookes A1 Tim M. Williams A1 David Errtizoe A1 Ben Sessa A1 Andreas Papadopoulos A1 Mark Bolstridge A1 Krish D. Singh A1 Amanda Feilding A1 Karl J. Friston A1 David J. Nutt YR 2013 UL http://www.jneurosci.org/content/33/38/15171.abstract AB Psychedelic drugs produce profound changes in consciousness, but the underlying neurobiological mechanisms for this remain unclear. Spontaneous and induced oscillatory activity was recorded in healthy human participants with magnetoencephalography after intravenous infusion of psilocybin—prodrug of the nonselective serotonin 2A receptor agonist and classic psychedelic psilocin. Psilocybin reduced spontaneous cortical oscillatory power from 1 to 50 Hz in posterior association cortices, and from 8 to 100 Hz in frontal association cortices. Large decreases in oscillatory power were seen in areas of the default-mode network. Independent component analysis was used to identify a number of resting-state networks, and activity in these was similarly decreased after psilocybin. Psilocybin had no effect on low-level visually induced and motor-induced gamma-band oscillations, suggesting that some basic elements of oscillatory brain activity are relatively preserved during the psychedelic experience. Dynamic causal modeling revealed that posterior cingulate cortex desynchronization can be explained by increased excitability of deep-layer pyramidal neurons, which are known to be rich in 5-HT2A receptors. These findings suggest that the subjective effects of psychedelics result from a desynchronization of ongoing oscillatory rhythms in the cortex, likely triggered by 5-HT2A receptor-mediated excitation of deep pyramidal cells.