Connectome Harmonic Signatures of Psychedelic State
Connectome Harmonic Signatures of Psychedelic States: A New Language for Altered States of Consciousness
What happens in the brain when consciousness is radically altered—when the boundaries of the self dissolve, time expands, and the world is perceived with heightened intensity? Using the framework of connectome harmonic decomposition, we explored this question by analyzing brain activity during psychedelic experiences.
In our study on LSD (Atasoy et al., 2017, Scientific Reports), and later in work exploring psilocybin (Atasoy et al., 2018, Progress in Brain Research) and DMT (Vohryzek et al., 2024, BioRxiv), we found a consistent changes in the brain’s harmonic activity—what we now refer to as the connectome harmonic signature of the psychedelic state.
Using fMRI data, we decomposed brain activity into its constituent connectome harmonics, revealing how different spatial frequencies contribute to the state of consciousness. Across all three substances—LSD, psilocybin, and DMT—we observed a consistent harmonic signature:
A significant increase in total power and energy of brain activity
A redistribution of energy toward higher-frequency connectome harmonics, and
A suppression of lower-frequency modes, which often reflect stable, integrative brain states like the default mode network
This shift indicates a dramatic expansion in the brain’s dynamical repertoire—as though the brain gains access to a broader and more intricate range of possible states. One way to understand this is through the metaphor of music: while normal brain activity may resemble a structured melody, psychedelics allow the brain to improvise like a jazz musician, exploring new variations, transitions, and tonalities.
These harmonic changes were not random—they correlated with specific subjective experiences. The greater the suppression of low-frequency modes, the stronger the reported ego dissolution. Increases in high-frequency energy were linked to emotional arousal and positive mood. This suggests that the quality and intensity of psychedelic experience depends on how the brain redistributes energy across its harmonic spectrum.
The findings also support the idea that LSD and other psychedelics may push the brain toward a state of criticality—a delicate balance between order and chaos. This state is believed to optimize information processing and creativity, and may explain why many people report heightened insight or emotional release under psychedelics.
These studies were carried out in close collaboration with Robin Carhart-Harris, Leor Roseman, Gustavo Deco, Morten Kringelbach, Jakub Vohryzek, Christopher Timmermann, and many others. By mapping altered states of consciousness in this new harmonic language, we take a step closer to understanding not just what psychedelics do to the brain—but how they open doors to expanded forms of awareness.
By decoding the psychedelic experience through the lens of connectome harmonics, we gain not only a new harmonic language for altered states of consciousness, but also a glimpse into the brain’s hidden capacity for spontaneous expression, integration, and improvisation."
If you want to dive deeper, see the related publications below and watch the selected talks:
• Atasoy, S., Roseman, L., Kaelen, M., Kringelbach, M. L., Deco, G., & Carhart-Harris, R. L. (2017). Connectome-harmonic decomposition of human brain activity reveals dynamical repertoire re-organization under LSD. Scientific reports, 7(1), 1-18.
• Atasoy, S., Vohryzek, J., G. Deco, G., Carhart-Harris, R. L., Kringelbach, M. L. (2018). Common neural signatures of psychedelics: Frequency-specific energy changes and repertoire expansion revealed using connectome-harmonic decomposition. Progress in brain research, 242, 97-120.
• Vohryzek, J., Luppi, A. I., Atasoy, S., Deco, G., Carhart-Harris, R. L., Timmermann, C., & Kringelbach, M. L. (2024). Time-resolved coupling between connectome harmonics and subjective experience under the psychedelic DMT. bioRxiv.
• Atasoy, S., Donnelly, I., & Pearson, J. (2016). Human brain networks function in connectome-specific harmonic waves. Nature communications, 7(1), 1-10. doi:10.1038/ncomms10340.
