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Ort A, Smallridge JW, Sarasso S, Casarotto S, von Rotz R, Casanova A, Seifritz E, Preller KH, Tononi G, Vollenweider FX. TMS-EEG and resting-state EEG applied to altered states of consciousness: oscillations, complexity, and phenomenology. iScience 2023; 26:106589. [PMID: 37138774 PMCID: PMC10149373 DOI: 10.1016/j.isci.2023.106589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 12/22/2022] [Accepted: 04/03/2023] [Indexed: 05/05/2023] Open
Abstract
Exploring the neurobiology of the profound changes in consciousness induced by classical psychedelic drugs may require novel neuroimaging methods. Serotonergic psychedelic drugs such as psilocybin produce states of increased sensory-emotional awareness and arousal, accompanied by increased spontaneous electroencephalographic (EEG) signal diversity. By directly stimulating cortical tissue, the altered dynamics and propagation of the evoked EEG activity can reveal drug-induced changes in the overall brain state. We combine Transcranial Magnetic Stimulation (TMS) and EEG to reveal that psilocybin produces a state of increased chaotic brain activity which is not a result of altered complexity in the underlying causal interactions between brain regions. We also map the regional effects of psilocybin on TMS-evoked activity and identify changes in frontal brain structures that may be associated with the phenomenology of psychedelic experiences.
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Affiliation(s)
- Andres Ort
- Neurophenomenology of Consciousness Lab, Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich, Zurich, Switzerland
- Corresponding author
| | - John W. Smallridge
- Neurophenomenology of Consciousness Lab, Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich, Zurich, Switzerland
- Corresponding author
| | - Simone Sarasso
- Department of Biomedical and Clinical Sciences, University of Milan, Milan, Italy
| | - Silvia Casarotto
- Department of Biomedical and Clinical Sciences, University of Milan, Milan, Italy
- IRCCS Fondazione Don Carlo Gnocchi Milano, Milan, Italy
| | - Robin von Rotz
- Neurophenomenology of Consciousness Lab, Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich, Zurich, Switzerland
| | - Andrea Casanova
- Neurophenomenology of Consciousness Lab, Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich, Zurich, Switzerland
| | - Erich Seifritz
- Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich, Zurich, Switzerland
| | - Katrin H. Preller
- Neurophenomenology of Consciousness Lab, Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich, Zurich, Switzerland
| | - Giulio Tononi
- Department of Psychiatry, University of Wisconsin, Madison, WI, USA
| | - Franz X. Vollenweider
- Neurophenomenology of Consciousness Lab, Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich, Zurich, Switzerland
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Abstract
Renewed interest in the effects of psychedelics in the treatment of psychiatric
disorders warrants a better understanding of the neurobiological mechanisms
underlying the effects of these substances. During the past two decades,
state-of-the-art studies of animals and humans have yielded new important
insights into the molecular, cellular, and systems-level actions of psychedelic
drugs. These efforts have revealed that psychedelics affect primarily
serotonergic receptor subtypes located in cortico-thalamic and cortico-cortical
feedback circuits of information processing. Psychedelic drugs modulate
excitatory-inhibitory balance in these circuits and can participate in
neuroplasticity within brain structures critical for the integration of
information relevant to sensation, cognition, emotions, and the narrative of
self. Neuroimaging studies showed that characteristic dimensions of the
psychedelic experience obtained through subjective questionnaires as well as
alterations in self-referential processing and emotion regulation obtained
through neuropsychological tasks are associated with distinct changes in brain
activity and connectivity patterns at multiple-system levels. These recent
results suggest that changes in self-experience, emotional processing, and
social cognition may contribute to the potential therapeutic effects of
psychedelics.
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Affiliation(s)
- Franz X. Vollenweider
- Neuropsychopharmacology and Brain Imaging, Department of Psychiatry,
Psychotherapy and Psychosomatics, University Hospital for Psychiatry Zurich,
Zurich, Switzerland
| | - John W. Smallridge
- Neuropsychopharmacology and Brain Imaging, Department of Psychiatry,
Psychotherapy and Psychosomatics, University Hospital for Psychiatry Zurich,
Zurich, Switzerland
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