NeuroImage
June 30, 2020
Thomas F. Varley, Robin Carhart‐Harris, Leor Roseman et al.
91 citations
Psychedelic drugs like psilocybin and LSD increase the fractal dimension of brain activity, suggesting that the brain moves toward a critical state between order and disorder. Using fMRI data from volunteers, the study tested two fractal measures: one for functional connectivity networks and one for BOLD time-series. Both drugs significantly increased the fractal dimension of functional connectivity networks. LSD also significantly increased the fractal dimension of BOLD signals, while psilocybin showed a non-significant trend in the same direction. Changes in the fractal dimension of BOLD signals were localized to brain areas in the dorsal attention network. These results indicate that psychedelic-induced changes in consciousness are associated with evolution toward a critical zone.
Human Brain Mapping
March 19, 2021
Andrea I. Luppi, Daniel Golkowski, Andreas Ranft et al.
72 citations
The human brain alternates between states of high integration and segregation, which are thought to support consciousness. Using dynamic functional connectivity and graph theory on resting-state fMRI data from healthy volunteers, the authors show that the integrated state is especially vulnerable to the anaesthetic sevoflurane. At higher doses (3% vol and burst-suppression), anaesthesia reduces the complexity and small-world character of integrated brain states and disrupts the temporal balance between integration and segregation. These effects reverse upon recovery, linking them to consciousness. Reduced anticorrelations between the default mode and executive control networks also reconfigure dynamically depending on the brain's integration state. The breakdown of the integrated sub-state may serve as a generalisable biomarker of loss and recovery of consciousness.
Science Advances
June 14, 2023
Leor Roseman, Christopher Timmermann, Daniel Golkowski et al.
65 citations
The effects of mind-altering drugs on brain function arise from complex interactions with multiple neurotransmitter systems, not just one. By linking the distribution of 19 neurotransmitter receptors and transporters (measured with PET) to changes in functional connectivity (measured with fMRI) caused by 10 drugs—anesthetics (propofol, sevoflurane, ketamine), psychedelics (LSD, psilocybin, DMT, ayahuasca), and others (MDMA, modafinil, methylphenidate)—the work shows a many-to-many mapping between drug effects and neurotransmitter systems. The drugs' impacts follow hierarchical gradients of brain structure and function, and regional susceptibility to drug-induced changes mirrors susceptibility to structural alterations from brain disorders.
bioRxiv (Cold Spring Harbor Laboratory)
August 10, 2020
Andrea I. Luppi, Jakub Vohryzek, Morten L. Kringelbach et al.
26 citations
preprint
Consciousness arises from how the brain's structural wiring shapes its dynamic activity. By decomposing resting-state fMRI data into harmonic modes of the human structural connectome, a generalizable signature of lost consciousness emerges—whether from anesthesia or brain injury—while a reversed signature characterizes psychedelic states induced by LSD or ketamine, reflecting decoupling of function from structure. This connectome harmonic approach discriminates between behaviorally indistinguishable brain-injured patients and tracks covert consciousness, linking neurobiology to conscious experience.
bioRxiv (Cold Spring Harbor Laboratory)
January 11, 2019
Tf Varley, Robin Carhart‐Harris, Leor Roseman et al.
8 citations
preprint
Psychedelic drugs like LSD and psilocybin increase the fractal dimension of brain activity, indicating a shift toward a critical state between order and chaos. Using fMRI data, researchers measured the fractal dimension of functional connectivity networks and BOLD time-series. Both drugs significantly increased the fractal dimension of functional connectivity networks; LSD also significantly increased the fractal dimension of BOLD signals, while psilocybin showed a non-significant trend in the same direction. Changes localized to the dorsal-attentional network. These findings support the Entropic Brain Hypothesis, which proposes that psychedelics alter consciousness by moving the brain closer to a critical tipping point.
bioRxiv (Cold Spring Harbor Laboratory)
July 13, 2022
Andrea I. Luppi, Justine Y. Hansen, R. Adapa et al.
5 citations
preprint
Psychoactive drugs reshape brain function by engaging multiple neurotransmitter systems simultaneously. By mapping the distribution of 19 neurotransmitter receptors and transporters (via PET) and the connectivity changes caused by 10 drugs (anesthetics, psychedelics, and stimulants), the study shows that drug effects are organized along hierarchical gradients of brain structure and function. Additionally, brain regions susceptible to drug-induced changes are also vulnerable to structural alterations from brain disorders. These findings reveal systematic links between molecular neurochemistry and large-scale functional reorganization.