Broadband Cortical Desynchronization Underlies the Human Psychedelic State
Journal of Neuroscience – September 18, 2013
Source: OpenAlex
Summary
Psilocybin, a potent hallucinogen, profoundly alters consciousness by desynchronizing brain activity. Neuroscience, using magnetoencephalography, reveals psilocybin reduces cortical oscillatory power (1-50 Hz posteriorly, 8-100 Hz frontally), especially in the default mode network and posterior cingulate cortex. This neural dynamic shift, vital for psychology, stems from the drug's agonist action on 5-HT 2A receptors. This neurotransmitter receptor influence on behavior suggests psychedelics disrupt brain function, a phenomenon also studied with electroencephalography in drug studies.
Abstract
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-HT 2A 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-HT 2A receptor-mediated excitation of deep pyramidal cells.