Psilocybin-induced EEG spectral changes of functional networks in healthy subjects.
Poster No:
1353
Submission Type:
Late-Breaking Abstract Submission
Authors:
Vidushani Dhanawansa1, Devon Stoliker2, Leonardo Novelli2, Mana Biabani1, Adeel Razi1, Levin Kuhlmann2
Institutions:
1Monash University, Melbourne, VIC, 2Monash University, Melbourne, Victoria
First Author:
Co-Author(s):
Late Breaking Reviewer(s):
Introduction:
Psilocybin, a serotonergic psychedelic, is valuable in studying altered states of consciousness and has shown efficacy in alleviating depressive symptoms(Haikazian et al., 2023). Since brain region inhibition and engagement are mediated by different frequency bands(Jensen & Mazaheri, 2010), studying psilocybin-induced broadband neural changes via EEG imaging could improve understanding of its subjective effects. Also, exploring functional connectivity (FC) between functionally relevant cortical regions rather than anatomical divisions could offer new insights(Kometer et al., 2015; Pallavicini et al., 2019). Major depressive disorder (MDD) patients exhibit higher alpha and beta coherence, but psilocybin's modulation of this remains unclear. To address this gap, we computed frequency specific resting-state FC using source-reconstructed EEG on the current largest non-clinical psychedelic imaging dataset.
Methods:
Eyes-closed resting-state EEG scans of baseline and post-administration(19mg psilocybin) were acquired from 56 participants using a 64-electrode cap. EEG preprocessing was followed by Minimum Norm Estimation (MNE) based EEG source reconstruction(Baillet et al., 2001). Electrode positions were co-registered with head anatomies, and Boundary Element Models (BEM) were generated. Source estimation resulted in 15002 electric dipoles constrained normal to the cortical surface. The Welch periodogram was computed with Hanning tapers on 2s epochs with 50% overlap. Source power maps generated within six canonical frequency bands were projected to the default anatomical surface and smoothened. Paired t-tests between baseline and psilocybin sessions analyzed group effects.
Resting-state functional connectivity (RSFC) was inferred via magnitude-squared coherence (MSC) within Yeo17 atlas networks using 100 Schaefer cortical parcellations. MSC was computed between principal components of each region, and time-frequency decomposition was achieved via Hilbert transform. Paired tests assessed the differences of the mean within-network MSC of all networks and frequency bands between sessions. All tests applied 5000 permutations and FDR correction at 0.05.
Resting-state functional connectivity (RSFC) was inferred via magnitude-squared coherence (MSC) within Yeo17 atlas networks using 100 Schaefer cortical parcellations. MSC was computed between principal components of each region, and time-frequency decomposition was achieved via Hilbert transform. Paired tests assessed the differences of the mean within-network MSC of all networks and frequency bands between sessions. All tests applied 5000 permutations and FDR correction at 0.05.
Results:
Psilocybin increased frontal delta power and decreased occipital delta power, induced widespread theta power decreases, reduced alpha power in DMN and visual networks, and increased gamma power(Fig.1). DMN-A (core DMN) engaged in self-referential processing, and DMN-B linked to planning showed FC decreases in the alpha and beta bands, but did not survive multiple comparison correction. FC decreased in the salience networks in the same bands. Psilocybin significantly increased FC in central and peripheral visual networks across all frequency bands except alpha(Fig.2).
Conclusions:
The DMN, integral to self-referential thought, exhibits hyperconnectivity in MDD(Broyd et al., 2009), highlighting its importance in interventions. MDD patients show higher alpha and beta coherence, critical for top-down control(Klimesch et al., 2007) and this increased alpha coherence may reflect impaired top-down regulation. Our findings show psilocybin acutely decreases RSFC in DMN, salience, and somatomotor networks in alpha and beta bands, key in top-down control. While studied in healthy subjects, psilocybin could modulate MDD-related coherence abnormalities, particularly in lower frequencies, normalizing dysfunctional top-down regulation.
Conversely, we found increased gamma FC, associated with neuronal excitation. This decrease in alpha and increase in gamma power supports the idea of a psilocybin-induced shift in excitation/inhibition balance toward excitation, contributing to altered states of consciousness. Additionally, increased visual network FC in non-alpha bands suggests a loss of alpha dominance, possibly linked to psychedelic-induced visual effects.
We contribute to the understanding how psilocybin could modulate neural markers of depression, such as dysfunctional DMN hyperconnectivity and impaired top-down control.
Conversely, we found increased gamma FC, associated with neuronal excitation. This decrease in alpha and increase in gamma power supports the idea of a psilocybin-induced shift in excitation/inhibition balance toward excitation, contributing to altered states of consciousness. Additionally, increased visual network FC in non-alpha bands suggests a loss of alpha dominance, possibly linked to psychedelic-induced visual effects.
We contribute to the understanding how psilocybin could modulate neural markers of depression, such as dysfunctional DMN hyperconnectivity and impaired top-down control.
Higher Cognitive Functions:
Executive Function, Cognitive Control and Decision Making
Modeling and Analysis Methods:
Connectivity (eg. functional, effective, structural)
EEG/MEG Modeling and Analysis 1
Task-Independent and Resting-State Analysis 2
Keywords:
Electroencephaolography (EEG)
Other - Resting state functional connectivity; Psilocybin; Default Mode Network
1|2Indicates the priority used for review
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