Broadband cortical desynchronization underlies the human psychedelic state
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-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.
Muthukumaraswamy, S. D., Carhart-Harris, R. L., Moran, R. J., Brookes, M. J., Williams, T. M., Errtizoe, D., … & Feilding, A. (2013). Broadband cortical desynchronization underlies the human psychedelic state. The Journal of Neuroscience, 33(38), 15171-15183. 10.1523/JNEUROSCI.2063-13.2013
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Carl Gustav Jung pioneered the transformative potential of the deep unconscious. Psychedelic substances provide direct and powerful access to this inner world. How, then, might Jungian psychology help us to better understand the nature of psychedelic experiences? And how might psychedelics assist the movement toward psychological transformation described by Jung?
Drawing on two years of ethnographic field research among the Navajos, this book explores a controversial Native American ritual and healthcare practice: ceremonial consumption of the psychedelic Peyote cactus in the context of an indigenous postcolonial healing movement called the Native American Church (NAC), which arose in the 19th century in response to the creation of the reservations system and increasing societal ills, including alcoholism. The movement is the locus of cultural conflict with a long history in North America, and stirs very strong and often opposed emotions and moral interpretations. Joseph Calabrese describes the Peyote Ceremony as it is used in family contexts and federally funded clinical programs for Native American patients. He uses an interdisciplinary methodology that he calls clinical ethnography: an approach to research that involves clinically informed and self-reflective immersion in local worlds of suffering, healing, and normality. Calabrese combined immersive fieldwork among NAC members in their communities with a year of clinical work at a Navajo-run treatment program for adolescents with severe substance abuse and associated mental health problems. There he had the unique opportunity to provide conventional therapeutic intervention alongside Native American therapists who were treating the very problems that the NAC often addresses through ritual. Calabrese argues that if people respond better to clinical interventions that are relevant to their society’s unique cultural adaptations and ideologies (as seems to be the case with the NAC), then preventing ethnic minorities from accessing traditional ritual forms of healing may actually constitute a human rights violation.