TMS-EEG and resting-state EEG applied to altered states of consciousness: oscillations, complexity, and phenomenology

Andres Ort; John W Smallridge; Simone Sarasso; Silvia Casarotto; Robin von Rotz; Andrea Casanova; Erich Seifritz; Katrin H Preller; Giulio Tononi; Franz X Vollenweider

doi:10.1016/j.isci.2023.106589

TMS-EEG and resting-state EEG applied to altered states of consciousness: oscillations, complexity, and phenomenology

iScience. 2023 Apr 7;26(5):106589. doi: 10.1016/j.isci.2023.106589. eCollection 2023 May 19.

Authors

Affiliations

¹ Neurophenomenology of Consciousness Lab, Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich, Zurich, Switzerland.
² Department of Biomedical and Clinical Sciences, University of Milan, Milan, Italy.
³ IRCCS Fondazione Don Carlo Gnocchi Milano, Milan, Italy.
⁴ Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich, Zurich, Switzerland.
⁵ Department of Psychiatry, University of Wisconsin, Madison, WI, USA.

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.

Keywords: Clinical neuroscience; Medical imaging; Pharmacology.